)]}'
{
  "log": [
    {
      "commit": "40393f525fe698e2b639cf1851ef0a40e7e158a8",
      "tree": "4067b416468413225a8ac8c75c43859fe3b03bb5",
      "parents": [
        "0e11c8e8a60f8591556d142c2e1e53eaf86ab528",
        "4eacdf18374e5d7d21a728b46dfec269ac8ef55c",
        "6d4b418c75a74eea1dd3701e106a9da8c335c451",
        "9fc52d832b5e7f6e175f3b20ae94504b780b9fd3"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jan 28 22:25:02 2013 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jan 28 22:25:21 2013 -0800"
      },
      "message": "Merge branches \u0027doctorture.2013.01.29a\u0027, \u0027fixes.2013.01.26a\u0027, \u0027tagcb.2013.01.24a\u0027 and \u0027tiny.2013.01.29b\u0027 into HEAD\n\ndoctorture.2013.01.11a: Changes to rcutorture and to RCU documentation.\n\nfixes.2013.01.26a: Miscellaneous fixes.\n\ntagcb.2013.01.24a: Tag RCU callbacks with grace-period number to\n\tsimplify callback advancement.\n\ntiny.2013.01.29b: Enhancements to uniprocessor handling in tiny RCU.\n"
    },
    {
      "commit": "6bfc09e2327dfbffc312004c16188dbf8dfb0297",
      "tree": "f36ac34ec671ea5eaa926ebabba8486bbda9c175",
      "parents": [
        "1b0048a44c502c5ab850203e6e0a6498d7d8676d"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Fri Oct 19 12:49:17 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jan 28 22:06:21 2013 -0800"
      },
      "message": "rcu: Provide RCU CPU stall warnings for tiny RCU\n\nTiny RCU has historically omitted RCU CPU stall warnings in order to\nreduce memory requirements, however, lack of these warnings caused\nThomas Gleixner some debugging pain recently.  Therefore, this commit\nadds RCU CPU stall warnings to tiny RCU if RCU_TRACE\u003dy.  This keeps\nthe memory footprint small, while still enabling CPU stall warnings\nin kernels built to enable them.\n\nUpdated to include Josh Triplett\u0027s suggested use of RCU_STALL_COMMON\nconfig variable to simplify #if expressions.\n\nReported-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "347f42382184f7448fa96bf9e9fa4eb6f6d1099e",
      "tree": "fd784fd8c7ae6b0ef2291a7cc2cf59da689d518e",
      "parents": [
        "2f03e3ca74a7f8b17ce626d337d321163dce2dad"
      ],
      "author": {
        "name": "Li Zhong",
        "email": "zhong@linux.vnet.ibm.com",
        "time": "Mon Jan 07 09:36:48 2013 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat Jan 26 16:34:48 2013 -0800"
      },
      "message": "rcu: Remove unused code originally used for context tracking\n\nAs context tracking subsystem evolved, it stopped using ignore_user_qs\nand in_user defined in the rcu_dynticks structure.  This commit therefore\nremoves them.\n\nSigned-off-by: Li Zhong \u003czhong@linux.vnet.ibm.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nAcked-by: Frederic Weisbecker \u003cfweisbec@gmail.com\u003e\n"
    },
    {
      "commit": "dc35c8934eba959b690921615fcd987e8bc17e4a",
      "tree": "c8020ec8ac191505e35905e89e58f02aa4e5fc31",
      "parents": [
        "1b0048a44c502c5ab850203e6e0a6498d7d8676d"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Dec 03 13:52:00 2012 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Jan 08 14:15:57 2013 -0800"
      },
      "message": "rcu: Tag callback lists with corresponding grace-period number\n\nCurrently, callbacks are advanced each time the corresponding CPU\nnotices a change in its leaf rcu_node structure\u0027s -\u003ecompleted value\n(this value counts grace-period completions).  This approach has worked\nquite well, but with the advent of RCU_FAST_NO_HZ, we cannot count on\na given CPU seeing all the grace-period completions.  When a CPU misses\na grace-period completion that occurs while it is in dyntick-idle mode,\nthis will delay invocation of its callbacks.\n\nIn addition, acceleration of callbacks (when RCU realizes that a given\ncallback need only wait until the end of the next grace period, rather\nthan having to wait for a partial grace period followed by a full\ngrace period) must be carried out extremely carefully.  Insufficient\nacceleration will result in unnecessarily long grace-period latencies,\nwhile excessive acceleration will result in premature callback invocation.\nChanges that involve this tradeoff are therefore among the most\nnerve-wracking changes to RCU.\n\nThis commit therefore explicitly tags groups of callbacks with the\nnumber of the grace period that they are waiting for.  This means that\ncallback-advancement and callback-acceleration functions are idempotent,\nso that excessive acceleration will merely waste a few CPU cycles.  This\nalso allows a CPU to take full advantage of any grace periods that have\nelapsed while it has been in dyntick-idle mode.  It should also enable\nsimulataneous simplifications to and optimizations of RCU_FAST_NO_HZ.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "c635a4e1c24e9396db10ed7424b2084908b32252",
      "tree": "ac1cced2e0c05d5edcd74af6d3493e15e99a7cec",
      "parents": [
        "3fbfbf7a3b66ec424042d909f14ba2ddf4372ea8"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon Oct 29 07:29:20 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Nov 16 10:05:57 2012 -0800"
      },
      "message": "rcu: Separate accounting of callbacks from callback-free CPUs\n\nCurrently, callback invocations from callback-free CPUs are accounted to\nthe CPU that registered the callback, but using the same field that is\nused for normal callbacks.  This makes it impossible to determine from\ndebugfs output whether callbacks are in fact being diverted.  This commit\ntherefore adds a separate -\u003en_nocbs_invoked field in the rcu_data structure\nin which diverted callback invocations are counted.  RCU\u0027s debugfs tracing\nstill displays normal callback invocations using ci\u003d, but displayed\ndiverted callbacks with nci\u003d.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "3fbfbf7a3b66ec424042d909f14ba2ddf4372ea8",
      "tree": "cc364c320a6e23927ecc154a8ef8021dc7d1a9e8",
      "parents": [
        "aac1cda34b84a9411d6b8d18c3658f094c834911"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Sun Aug 19 21:35:53 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Nov 16 10:05:56 2012 -0800"
      },
      "message": "rcu: Add callback-free CPUs\n\nRCU callback execution can add significant OS jitter and also can\ndegrade both scheduling latency and, in asymmetric multiprocessors,\nenergy efficiency.  This commit therefore adds the ability for selected\nCPUs (\"rcu_nocbs\u003d\" boot parameter) to have their callbacks offloaded\nto kthreads.  If the \"rcu_nocb_poll\" boot parameter is also specified,\nthese kthreads will do polling, removing the need for the offloaded\nCPUs to do wakeups.  At least one CPU must be doing normal callback\nprocessing: currently CPU 0 cannot be selected as a no-CBs CPU.\nIn addition, attempts to offline the last normal-CBs CPU will fail.\n\nThis feature was inspired by Jim Houston\u0027s and Joe Korty\u0027s JRCU, and\nthis commit includes fixes to problems located by Fengguang Wu\u0027s\nkbuild test robot.\n\n[ paulmck: Added gfp.h include file as suggested by Fengguang Wu. ]\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "a30489c5228fba6f16b4c740a0292879ef13371e",
      "tree": "2a28a2d6180f8315a8c1cee12cdb415a90b167f0",
      "parents": [
        "40694d6644d5cca28531707559466122eb212d8b"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Thu Oct 11 16:18:09 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Nov 08 11:50:13 2012 -0800"
      },
      "message": "rcu: Instrument synchronize_rcu_expedited() for debugfs tracing\n\nThis commit adds the counters to rcu_state and updates them in\nsynchronize_rcu_expedited() to provide the data needed for debugfs\ntracing.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "40694d6644d5cca28531707559466122eb212d8b",
      "tree": "4585fe95e0fa05c3273343971d46ea4403af294f",
      "parents": [
        "1924bcb0259711eea98491a7942d1ffbf677e114"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Thu Oct 11 15:24:03 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Nov 08 11:50:12 2012 -0800"
      },
      "message": "rcu: Move synchronize_sched_expedited() state to rcu_state\n\nTracing (debugfs) of expedited RCU primitives is required, which in turn\nrequires that the relevant data be located where the tracing code can find\nit, not in its current static global variables in kernel/rcutree.c.\nThis commit therefore moves sync_sched_expedited_started and\nsync_sched_expedited_done to the rcu_state structure, as fields\n-\u003eexpedited_start and -\u003eexpedited_done, respectively.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "7b2e6011f150c42235c4a541d20cf6891afe878a",
      "tree": "a02ac239103e97847ec29183d8aaa45c385a3335",
      "parents": [
        "489832609a1ad7189d11715d8cefb457d90182c5"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon Oct 08 10:54:03 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Nov 08 11:50:11 2012 -0800"
      },
      "message": "rcu: Rename -\u003eonofflock to -\u003eorphan_lock\n\nThe -\u003eonofflock field in the rcu_state structure at one time synchronized\nCPU-hotplug operations for RCU.  However, its scope has decreased over time\nso that it now only protects the lists of orphaned RCU callbacks.  This\ncommit therefore renames it to -\u003eorphan_lock to reflect its current use.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "a4fbe35a124526e6759be07bd9c7ea796ba1e00d",
      "tree": "cb5c5a1608fcff588ed9a204ea67d5891adb18fb",
      "parents": [
        "cb349ca95407cbc11424d5e9fc7c8e700709041b"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Oct 07 08:36:12 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Oct 08 09:06:38 2012 -0700"
      },
      "message": "rcu: Grace-period initialization excludes only RCU notifier\n\nKirill noted the following deadlock cycle on shutdown involving padata:\n\n\u003e With commit 755609a9087fa983f567dc5452b2fa7b089b591f I\u0027ve got deadlock on\n\u003e poweroff.\n\u003e\n\u003e It guess it happens because of race for cpu_hotplug.lock:\n\u003e\n\u003e       CPU A                                   CPU B\n\u003e disable_nonboot_cpus()\n\u003e _cpu_down()\n\u003e cpu_hotplug_begin()\n\u003e  mutex_lock(\u0026cpu_hotplug.lock);\n\u003e __cpu_notify()\n\u003e padata_cpu_callback()\n\u003e __padata_remove_cpu()\n\u003e padata_replace()\n\u003e synchronize_rcu()\n\u003e                                       rcu_gp_kthread()\n\u003e                                       get_online_cpus();\n\u003e                                       mutex_lock(\u0026cpu_hotplug.lock);\n\nIt would of course be good to eliminate grace-period delays from\nCPU-hotplug notifiers, but that is a separate issue.  Deadlock is\nnot an appropriate diagnostic for excessive CPU-hotplug latency.\n\nFortunately, grace-period initialization does not actually need to\nexclude all of the CPU-hotplug operation, but rather only RCU\u0027s own\nCPU_UP_PREPARE and CPU_DEAD CPU-hotplug notifiers.  This commit therefore\nintroduces a new per-rcu_state onoff_mutex that provides the required\nconcurrency control in place of the get_online_cpus() that was previously\nin rcu_gp_init().\n\nReported-by: \"Kirill A. Shutemov\" \u003ckirill@shutemov.name\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nTested-by: Kirill A. Shutemov \u003ckirill@shutemov.name\u003e\n"
    },
    {
      "commit": "1e1a689f10a27a4fe1ab9b4c6db04fa7232746a5",
      "tree": "098f180287723813d248f59f452ca3a7db04b636",
      "parents": [
        "c5d900bf676b1e2a61c44483932c8088651bbb4e"
      ],
      "author": {
        "name": "Frederic Weisbecker",
        "email": "fweisbec@gmail.com",
        "time": "Wed Jul 11 20:26:32 2012 +0200"
      },
      "committer": {
        "name": "Frederic Weisbecker",
        "email": "fweisbec@gmail.com",
        "time": "Wed Sep 26 15:47:01 2012 +0200"
      },
      "message": "rcu: Ignore userspace extended quiescent state by default\n\nBy default we don\u0027t want to enter into RCU extended quiescent\nstate while in userspace because doing this produces some overhead\n(eg: use of syscall slowpath). Set it off by default and ready to\nrun when some feature like adaptive tickless need it.\n\nSigned-off-by: Frederic Weisbecker \u003cfweisbec@gmail.com\u003e\nCc: Alessio Igor Bogani \u003cabogani@kernel.org\u003e\nCc: Andrew Morton \u003cakpm@linux-foundation.org\u003e\nCc: Avi Kivity \u003cavi@redhat.com\u003e\nCc: Chris Metcalf \u003ccmetcalf@tilera.com\u003e\nCc: Christoph Lameter \u003ccl@linux.com\u003e\nCc: Geoff Levand \u003cgeoff@infradead.org\u003e\nCc: Gilad Ben Yossef \u003cgilad@benyossef.com\u003e\nCc: Hakan Akkan \u003chakanakkan@gmail.com\u003e\nCc: H. Peter Anvin \u003chpa@zytor.com\u003e\nCc: Ingo Molnar \u003cmingo@kernel.org\u003e\nCc: Josh Triplett \u003cjosh@joshtriplett.org\u003e\nCc: Kevin Hilman \u003ckhilman@ti.com\u003e\nCc: Max Krasnyansky \u003cmaxk@qualcomm.com\u003e\nCc: Peter Zijlstra \u003cpeterz@infradead.org\u003e\nCc: Stephen Hemminger \u003cshemminger@vyatta.com\u003e\nCc: Steven Rostedt \u003crostedt@goodmis.org\u003e\nCc: Sven-Thorsten Dietrich \u003cthebigcorporation@gmail.com\u003e\nCc: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "c5d900bf676b1e2a61c44483932c8088651bbb4e",
      "tree": "881ee6420ba291d68d451986d5ed9832ee95661f",
      "parents": [
        "2b1d5024e17be459aa6385763ca3faa8f01c52d9"
      ],
      "author": {
        "name": "Frederic Weisbecker",
        "email": "fweisbec@gmail.com",
        "time": "Wed Jul 11 20:26:31 2012 +0200"
      },
      "committer": {
        "name": "Frederic Weisbecker",
        "email": "fweisbec@gmail.com",
        "time": "Wed Sep 26 15:46:55 2012 +0200"
      },
      "message": "rcu: Allow rcu_user_enter()/exit() to nest\n\nAllow calls to rcu_user_enter() even if we are already\nin userspace (as seen by RCU) and allow calls to rcu_user_exit()\neven if we are already in the kernel.\n\nThis makes the APIs more flexible to be called from architectures.\nException entries for example won\u0027t need to know if they come from\nuserspace before calling rcu_user_exit().\n\nSigned-off-by: Frederic Weisbecker \u003cfweisbec@gmail.com\u003e\nCc: Alessio Igor Bogani \u003cabogani@kernel.org\u003e\nCc: Andrew Morton \u003cakpm@linux-foundation.org\u003e\nCc: Avi Kivity \u003cavi@redhat.com\u003e\nCc: Chris Metcalf \u003ccmetcalf@tilera.com\u003e\nCc: Christoph Lameter \u003ccl@linux.com\u003e\nCc: Geoff Levand \u003cgeoff@infradead.org\u003e\nCc: Gilad Ben Yossef \u003cgilad@benyossef.com\u003e\nCc: Hakan Akkan \u003chakanakkan@gmail.com\u003e\nCc: H. Peter Anvin \u003chpa@zytor.com\u003e\nCc: Ingo Molnar \u003cmingo@kernel.org\u003e\nCc: Josh Triplett \u003cjosh@joshtriplett.org\u003e\nCc: Kevin Hilman \u003ckhilman@ti.com\u003e\nCc: Max Krasnyansky \u003cmaxk@qualcomm.com\u003e\nCc: Peter Zijlstra \u003cpeterz@infradead.org\u003e\nCc: Stephen Hemminger \u003cshemminger@vyatta.com\u003e\nCc: Steven Rostedt \u003crostedt@goodmis.org\u003e\nCc: Sven-Thorsten Dietrich \u003cthebigcorporation@gmail.com\u003e\nCc: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "5217192b85480353aeeb395574e60d0db04f3676",
      "tree": "a45b440623a8fc55ece18b72e40829b2d9815d74",
      "parents": [
        "bda4ec9f6a7d7b249c7b14baa553731efedce300",
        "bff4a394795add6b919debc009f72b7607f5d4bf"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Sep 25 10:01:45 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Sep 25 10:01:45 2012 -0700"
      },
      "message": "Merge remote-tracking branch \u0027tip/smp/hotplug\u0027 into next.2012.09.25b\n\nThe conflicts between kernel/rcutree.h and kernel/rcutree_plugin.h\nwere due to adjacent insertions and deletions, which were resolved\nby simply accepting the changes on both branches.\n"
    },
    {
      "commit": "bda4ec9f6a7d7b249c7b14baa553731efedce300",
      "tree": "3ef6df518d8d48a29f4aafc05ffa4d427b015ce9",
      "parents": [
        "b17c7035f37f47c7f7cb08a5555ab2aebfa31f91",
        "60f53782c51f27c695840ce90c6c432284319eef",
        "86f343b50bb9f56cce60fade22da9defff28934c",
        "429227bbe55647aa42f8f63cac61e4544e248629",
        "93482f4ef1093f5961a63359a34612183d6beea0"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 23 20:37:55 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Sep 24 20:02:22 2012 -0700"
      },
      "message": "Merge branches \u0027bigrt.2012.09.23a\u0027, \u0027doctorture.2012.09.23a\u0027, \u0027fixes.2012.09.23a\u0027, \u0027hotplug.2012.09.23a\u0027 and \u0027idlechop.2012.09.23a\u0027 into HEAD\n\nbigrt.2012.09.23a contains additional commits to reduce scheduling latency\n\tfrom RCU on huge systems (many hundrends or thousands of CPUs).\n\ndoctorture.2012.09.23a contains documentation changes and rcutorture fixes.\n\nfixes.2012.09.23a contains miscellaneous fixes.\n\nhotplug.2012.09.23a contains CPU-hotplug-related changes.\n\nidle.2012.09.23a fixes architectures for which RCU no longer considered\n\tthe idle loop to be a quiescent state due to earlier\n\tadaptive-dynticks changes.  Affected architectures are alpha,\n\tcris, frv, h8300, m32r, m68k, mn10300, parisc, score, xtensa,\n\tand ia64.\n"
    },
    {
      "commit": "1331e7a1bbe1f11b19c4327ba0853bee2a606543",
      "tree": "596d9ed379ef7e2c5d8cf1cc0ba56ade084548ec",
      "parents": [
        "a10d206ef1a83121ab7430cb196e0376a7145b22"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Thu Aug 02 17:43:50 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 23 07:43:55 2012 -0700"
      },
      "message": "rcu: Remove _rcu_barrier() dependency on __stop_machine()\n\nCurrently, _rcu_barrier() relies on preempt_disable() to prevent\nany CPU from going offline, which in turn depends on CPU hotplug\u0027s\nuse of __stop_machine().\n\nThis patch therefore makes _rcu_barrier() use get_online_cpus() to\nblock CPU-hotplug operations.  This has the added benefit of removing\nthe need for _rcu_barrier() to adopt callbacks:  Because CPU-hotplug\noperations are excluded, there can be no callbacks to adopt.  This\ncommit simplifies the code accordingly.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "d7d6a11e8609f0319d4a2d8ede348f8b3374b652",
      "tree": "64a2e3260690a85fe637a3e34c94e8ca540e8fc6",
      "parents": [
        "1943c89de700248d68385300a9b5588a1e314f90"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue Aug 21 15:00:05 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 23 07:41:56 2012 -0700"
      },
      "message": "rcu: Simplify quiescent-state detection\n\nThe current quiescent-state detection algorithm is needlessly\ncomplex.  It records the grace-period number corresponding to\nthe quiescent state at the time of the quiescent state, which\nworks, but it seems better to simply erase any record of previous\nquiescent states at the time that the CPU notices the new grace\nperiod.  This has the further advantage of removing another piece\nof RCU for which lockless reasoning is required.\n\nTherefore, this commit makes this change.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "394f2769aa0dbcf027bae6fb52835e25e05d332e",
      "tree": "78471127d379e8d128d73e976ce33022c195b0c5",
      "parents": [
        "4605c0143c6d611b3076025ba3a7e04293c01d69"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Jun 26 17:00:35 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 23 07:41:54 2012 -0700"
      },
      "message": "rcu: Prevent force_quiescent_state() memory contention\n\nLarge systems running RCU_FAST_NO_HZ kernels see extreme memory\ncontention on the rcu_state structure\u0027s -\u003efqslock field.  This\ncan be avoided by disabling RCU_FAST_NO_HZ, either at compile time\nor at boot time (via the nohz kernel boot parameter), but large\nsystems will no doubt become sensitive to energy consumption.\nThis commit therefore uses a combining-tree approach to spread the\nmemory contention across new cache lines in the leaf rcu_node structures.\nThis can be thought of as a tournament lock that has only a try-lock\nacquisition primitive.\n\nThe effect on small systems is minimal, because such systems have\nan rcu_node \"tree\" consisting of a single node.  In addition, this\nfunctionality is not used on fastpaths.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "4605c0143c6d611b3076025ba3a7e04293c01d69",
      "tree": "bbdc00cf1043729d07b7e228fd5581d992b17cd1",
      "parents": [
        "b4be093fee0200789df59b6c90e2d099a20f55b3"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Jun 26 14:00:48 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 23 07:41:54 2012 -0700"
      },
      "message": "rcu: Adjust debugfs tracing for kthread-based quiescent-state forcing\n\nMoving quiescent-state forcing into a kthread dispenses with the need\nfor the -\u003en_rp_need_fqs field, so this commit removes it.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "4cdfc175c25c89eedc08460b5e6239c2ec67fcb6",
      "tree": "716acd208cb0633cdd19fc0cd5ad601906cceb24",
      "parents": [
        "b402b73b3afe3614bc0e921ebe18013ea103115a"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Jun 22 17:06:26 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 23 07:41:54 2012 -0700"
      },
      "message": "rcu: Move quiescent-state forcing into kthread\n\nAs the first step towards allowing quiescent-state forcing to be\npreemptible, this commit moves RCU quiescent-state forcing into the\nsame kthread that is now used to initialize and clean up after grace\nperiods.  This is yet another step towards keeping scheduling\nlatency down to a dull roar.\n\nUpdated to change from raw_spin_lock_irqsave() to raw_spin_lock_irq()\nand to remove the now-unused rcu_state structure fields as suggested by\nPeter Zijlstra.\n\nReported-by: Mike Galbraith \u003cmgalbraith@suse.de\u003e\nReported-by: Dimitri Sivanich \u003csivanich@sgi.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "b402b73b3afe3614bc0e921ebe18013ea103115a",
      "tree": "d5f941ae2bbae05e496ff1b8415bffc30b6a80b8",
      "parents": [
        "b626c1b689364859ccd2e86d5e043aeadfeb2cd4"
      ],
      "author": {
        "name": "Dimitri Sivanich",
        "email": "sivanich@sgi.com",
        "time": "Fri Jun 29 14:17:29 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 23 07:41:53 2012 -0700"
      },
      "message": "rcu: Segregate rcu_state fields to improve cache locality\n\nThe fields in the rcu_state structure that are protected by the\nroot rcu_node structure\u0027s -\u003elock can share a cache line with the\nfields protected by -\u003eonofflock.  This can result in excessive\nmemory contention on large systems, so this commit applies\n____cacheline_internodealigned_in_smp to the -\u003eonofflock field in\norder to segregate them.\n\nSigned-off-by: Dimitri Sivanich \u003csivanich@sgi.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nTested-by: Dimitri Sivanich \u003csivanich@sgi.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "b626c1b689364859ccd2e86d5e043aeadfeb2cd4",
      "tree": "6a9deb7bd94a1bcf30b60ca0eb8c1d5f3a2b9172",
      "parents": [
        "bfa00b4c4028f39357d16279ff0fddf550241593"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon Jun 11 17:39:43 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 23 07:41:53 2012 -0700"
      },
      "message": "rcu: Provide OOM handler to motivate lazy RCU callbacks\n\nIn kernels built with CONFIG_RCU_FAST_NO_HZ\u003dy, CPUs can accumulate a\nlarge number of lazy callbacks, which as the name implies will be slow\nto be invoked.  This can be a problem on small-memory systems, where the\ndefault 6-second sleep for CPUs having only lazy RCU callbacks could well\nbe fatal.  This commit therefore installs an OOM hander that ensures that\nevery CPU with lazy callbacks has at least one non-lazy callback, in turn\nensuring timely advancement for these callbacks.\n\nUpdated to fix bug that disabled OOM killing, noted by Lai Jiangshan.\n\nUpdated to push the for_each_rcu_flavor() loop into rcu_oom_notify_cpu(),\nthus reducing the number of IPIs, as suggested by Steven Rostedt.  Also\nto make the for_each_online_cpu() loop be preemptible.  (Later, it might\nbe good to use smp_call_function(), as suggested by Peter Zijlstra.)\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nTested-by: Sasha Levin \u003clevinsasha928@gmail.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "b3dbec76e5334fbb063987dea14e7b255602d7e4",
      "tree": "5b75e737856baf09b2303bebf7d9893b8279c84e",
      "parents": [
        "a10d206ef1a83121ab7430cb196e0376a7145b22"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jun 18 18:36:08 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 23 07:41:52 2012 -0700"
      },
      "message": "rcu: Move RCU grace-period initialization into a kthread\n\nAs the first step towards allowing grace-period initialization to be\npreemptible, this commit moves the RCU grace-period initialization\ninto its own kthread.  This is needed to keep large-system scheduling\nlatency at reasonable levels.\n\nAlso change raw_spin_lock_irqsave() to raw_spin_lock_irq() as suggested\nby Peter Zijlstra in review comments.\n\nReported-by: Mike Galbraith \u003cmgalbraith@suse.de\u003e\nReported-by: Dimitri Sivanich \u003csivanich@sgi.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "62ab7072476ae1600e877cc62b43758e485f4f1e",
      "tree": "c1df0992432cf5bae0f9122d606e73628368fb8e",
      "parents": [
        "bcd951cf10f24e341defcd002c15a1f4eea13ddb"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 16 10:42:38 2012 +0000"
      },
      "committer": {
        "name": "Thomas Gleixner",
        "email": "tglx@linutronix.de",
        "time": "Mon Aug 13 17:01:08 2012 +0200"
      },
      "message": "rcu: Use smp_hotplug_thread facility for RCUs per-CPU kthread\n\nBring RCU into the new-age CPU-hotplug fold by modifying RCU\u0027s per-CPU\nkthread code to use the new smp_hotplug_thread facility.\n\n[ tglx: Adapted it to use callbacks and to the simplified rcu yield ]\n    \nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: Peter Zijlstra \u003cpeterz@infradead.org\u003e\nCc: Srivatsa S. Bhat \u003csrivatsa.bhat@linux.vnet.ibm.com\u003e\nCc: Rusty Russell \u003crusty@rustcorp.com.au\u003e\nCc: Namhyung Kim \u003cnamhyung@kernel.org\u003e\nLink: http://lkml.kernel.org/r/20120716103948.673354828@linutronix.de\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\n"
    },
    {
      "commit": "5d01bbd111d6ff9ea9d9847774f66dff39633776",
      "tree": "77cbce5ff479b3e70f95a29cc88ce50e025f9078",
      "parents": [
        "3bf671af14d591ede9251acb0085e8017f3705e7"
      ],
      "author": {
        "name": "Thomas Gleixner",
        "email": "tglx@linutronix.de",
        "time": "Mon Jul 16 10:42:35 2012 +0000"
      },
      "committer": {
        "name": "Thomas Gleixner",
        "email": "tglx@linutronix.de",
        "time": "Mon Aug 13 17:01:06 2012 +0200"
      },
      "message": "rcu: Yield simpler\n\nThe rcu_yield() code is amazing. It\u0027s there to avoid starvation of the\nsystem when lots of (boosting) work is to be done.\n\nNow looking at the code it\u0027s functionality is:\n\n Make the thread SCHED_OTHER and very nice, i.e. get it out of the way\n Arm a timer with 2 ticks\n schedule()\n\nNow if the system goes idle the rcu task returns, regains SCHED_FIFO\nand plugs on. If the systems stays busy the timer fires and wakes a\nper node kthread which in turn makes the per cpu thread SCHED_FIFO and\nbrings it back on the cpu. For the boosting thread the \"make it FIFO\"\nbit is missing and it just runs some magic boost checks. Now this is a\nlot of code with extra threads and complexity.\n\nIt\u0027s way simpler to let the tasks when they detect overload schedule\naway for 2 ticks and defer the normal wakeup as long as they are in\nyielded state and the cpu is not idle.\n\nThat solves the same problem and the only difference is that when the\ncpu goes idle it\u0027s not guaranteed that the thread returns right away,\nbut it won\u0027t be longer out than two ticks, so no harm is done. If\nthat\u0027s an issue than it is way simpler just to wake the task from\nidle as RCU has callbacks there anyway.\n\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nCc: Peter Zijlstra \u003cpeterz@infradead.org\u003e\nCc: Srivatsa S. Bhat \u003csrivatsa.bhat@linux.vnet.ibm.com\u003e\nCc: Rusty Russell \u003crusty@rustcorp.com.au\u003e\nCc: Namhyung Kim \u003cnamhyung@kernel.org\u003e\nReviewed-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nLink: http://lkml.kernel.org/r/20120716103948.131256723@linutronix.de\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\n"
    },
    {
      "commit": "02a0677b0be545a07ffb15a13419efd7c82881e0",
      "tree": "90a5e0699269465c16cc4e247bc5980d0655c3e6",
      "parents": [
        "ff015030c939f0bec68fa9b8898da3aaa7fe55ea",
        "72472a02a9c4507ef54d03d71bb253c26015f52c",
        "cfca927972e31a5b3da49bf641c525732ff3c357",
        "9d2ad24306f2fafc3612e5a216aab31f9e56e879"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Jul 06 05:59:20 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Jul 06 05:59:30 2012 -0700"
      },
      "message": "Merge branches \u0027bigrtm.2012.07.04a\u0027, \u0027doctorture.2012.07.02a\u0027, \u0027fixes.2012.07.06a\u0027 and \u0027fnh.2012.07.02a\u0027 into HEAD\n\nbigrtm: First steps towards getting RCU out of the way of\n\ttens-of-microseconds real-time response on systems compiled\n\twith NR_CPUS\u003d4096.  Also cleanups for and increased concurrency\n\tof rcu_barrier() family of primitives.\ndoctorture: rcutorture and documentation improvements.\nfixes:  Miscellaneous fixes.\nfnh: RCU_FAST_NO_HZ fixes and improvements.\n"
    },
    {
      "commit": "9d2ad24306f2fafc3612e5a216aab31f9e56e879",
      "tree": "6ced8145e842e29aaedda3d9453c74b6f0c92b4f",
      "parents": [
        "4fa3b6cb1bc8c14b81b4c8ffdfd3f2500a7e9367"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Sun Jun 24 10:15:02 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 12:34:43 2012 -0700"
      },
      "message": "rcu: Make RCU_FAST_NO_HZ respect nohz\u003d boot parameter\n\nIf the nohz\u003d boot parameter disables nohz, then RCU_FAST_NO_HZ needs to\nalso disable itself.  This commit therefore checks for tick_nohz_enabled\nbeing zero, disabling rcu_prepare_for_idle() if so.  This commit assumes\nthat tick_nohz_enabled can change at runtime: If this is not the case,\nthen a simpler approach suffices.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "6ce75a2326e6f8b3bdfb60e1de7934b89858e87b",
      "tree": "c3ecd512422ad9f445f69c78037142a99bc8db2c",
      "parents": [
        "1bca8cf1a2c3c6683b12ad28a3e826ca7a834978"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Jun 12 11:01:13 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 12:33:24 2012 -0700"
      },
      "message": "rcu: Introduce for_each_rcu_flavor() and use it\n\nThe arrival of TREE_PREEMPT_RCU some years back included some ugly\ncode involving either #ifdef or #ifdef\u0027ed wrapper functions to iterate\nover all non-SRCU flavors of RCU.  This commit therefore introduces\na for_each_rcu_flavor() iterator over the rcu_state structures for each\nflavor of RCU to clean up a bit of the ugliness.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "cf3a9c4842b1e097dbe0854933c471d43dd24f69",
      "tree": "5b2737cade79c491ba46cd642c01cc165118d723",
      "parents": [
        "cfed0a85dad921c683e9c0d25b072bcc5745ede0"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue May 29 14:56:46 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 12:33:23 2012 -0700"
      },
      "message": "rcu: Increase rcu_barrier() concurrency\n\nThe traditional rcu_barrier() implementation has serialized all requests,\nregardless of RCU flavor, and also does not coalesce concurrent requests.\nIn the past, this has been good and sufficient.\n\nHowever, systems are getting larger and use of rcu_barrier() has been\nincreasing.  This commit therefore introduces a counter-based scheme\nthat allows _rcu_barrier() calls for the same flavor of RCU to take\nadvantage of each others\u0027 work.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "7be7f0be907224445acc62b3884c892f38b7ff40",
      "tree": "9802c524d04374e6a4e5c5b9d3a0d3c9085ef2fd",
      "parents": [
        "7db74df88b52844f4e966901e2972bba725e6766"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue May 29 05:18:53 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 12:33:22 2012 -0700"
      },
      "message": "rcu: Move rcu_barrier_mutex to rcu_state structure\n\nIn order to allow each RCU flavor to concurrently execute its\nrcu_barrier() function, it is necessary to move the relevant\nstate to the rcu_state structure.  This commit therefore moves the\nrcu_barrier_mutex global variable to a new -\u003ebarrier_mutex field\nin the rcu_state structure.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "7db74df88b52844f4e966901e2972bba725e6766",
      "tree": "ccb2139d2c4628591287bf456ede1164cef43d0f",
      "parents": [
        "24ebbca8ecdd5129d7f829a7cb5146aaeb531f77"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue May 29 03:03:37 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 12:33:22 2012 -0700"
      },
      "message": "rcu: Move rcu_barrier_completion to rcu_state structure\n\nIn order to allow each RCU flavor to concurrently execute its\nrcu_barrier() function, it is necessary to move the relevant\nstate to the rcu_state structure.  This commit therefore moves the\nrcu_barrier_completion global variable to a new -\u003ebarrier_completion\nfield in the rcu_state structure.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "24ebbca8ecdd5129d7f829a7cb5146aaeb531f77",
      "tree": "b7a4bb8044dcd1e13119113c77d2a4b96ba25a43",
      "parents": [
        "06668efa9180f4824fe846a8ff96338c18646bc7"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue May 29 00:34:56 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 12:33:22 2012 -0700"
      },
      "message": "rcu: Move rcu_barrier_cpu_count to rcu_state structure\n\nIn order to allow each RCU flavor to concurrently execute its rcu_barrier()\nfunction, it is necessary to move the relevant state to the rcu_state\nstructure.  This commit therefore moves the rcu_barrier_cpu_count global\nvariable to a new -\u003ebarrier_cpu_count field in the rcu_state structure.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "06668efa9180f4824fe846a8ff96338c18646bc7",
      "tree": "2bda53825cb3437af82bc1db4a4114ee8e29e954",
      "parents": [
        "037b64ed0bf2405a1a01542164d3418564b44fff"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon May 28 23:57:46 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 12:33:21 2012 -0700"
      },
      "message": "rcu: Move _rcu_barrier()\u0027s rcu_head structures to rcu_data structures\n\nIn order for multiple flavors of RCU to each concurrently run one\nrcu_barrier(), each flavor needs its own per-CPU set of rcu_head\nstructures.  This commit therefore moves _rcu_barrier()\u0027s set of\nper-CPU rcu_head structures from per-CPU variables to the existing\nper-CPU and per-RCU-flavor rcu_data structures.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "037b64ed0bf2405a1a01542164d3418564b44fff",
      "tree": "59aa7e486e1673564f2a5687992130dffa71ca1b",
      "parents": [
        "6c90cc7bf077f28144013e949ee0c122012d194a"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon May 28 23:26:01 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 12:33:21 2012 -0700"
      },
      "message": "rcu: Place pointer to call_rcu() in rcu_data structure\n\nThis is a preparatory commit for increasing rcu_barrier()\u0027s concurrency.\nIt adds a pointer in the rcu_data structure to the corresponding call_rcu()\nfunction.  This allows a pointer to the rcu_data structure to imply the\nfunction pointer, which allows _rcu_barrier() state to be placed in the\nrcu_state structure.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "f885b7f2b2de70be266d2cecc476f773a1e2ca5d",
      "tree": "c4f4d03ca1469f22701b848274034a74c5ae2b04",
      "parents": [
        "cba6d0d64ee53772b285d0c0c288deefbeaf7775"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Apr 23 15:52:53 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 12:33:20 2012 -0700"
      },
      "message": "rcu: Control RCU_FANOUT_LEAF from boot-time parameter\n\nAlthough making RCU_FANOUT_LEAF a kernel configuration parameter rather\nthan a fixed constant makes it easier for people to decrease cache-miss\noverhead for large systems, it is of little help for people who must\nrun a single pre-built kernel binary.\n\nThis commit therefore allows the value of RCU_FANOUT_LEAF to be\nincreased (but not decreased!) via a boot-time parameter named\nrcutree.rcu_fanout_leaf.\n\nReported-by: Mike Galbraith \u003cefault@gmx.de\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "cba6d0d64ee53772b285d0c0c288deefbeaf7775",
      "tree": "b2d3de62d15a77d23708c1af6f188c86f0d87fb9",
      "parents": [
        "6887a4131da3adaab011613776d865f4bcfb5678"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 07:08:42 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jul 02 11:39:19 2012 -0700"
      },
      "message": "Revert \"rcu: Move PREEMPT_RCU preemption to switch_to() invocation\"\n\nThis reverts commit 616c310e83b872024271c915c1b9ab505b9efad9.\n(Move PREEMPT_RCU preemption to switch_to() invocation).\nTesting by Sasha Levin \u003clevinsasha928@gmail.com\u003e showed that this\ncan result in deadlock due to invoking the scheduler when one of\nthe runqueue locks is held.  Because this commit was simply a\nperformance optimization, revert it.\n\nReported-by: Sasha Levin \u003clevinsasha928@gmail.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nTested-by: Sasha Levin \u003clevinsasha928@gmail.com\u003e\n"
    },
    {
      "commit": "5955f7eecd77d6b440db278b266cfecdb72ecd00",
      "tree": "a69a23707da5595be22fa09738be572a4ef69b4c",
      "parents": [
        "fd4b352687fd8604d49c190c4c9ea9e369fd42d5"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Wed May 09 12:07:05 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Jun 06 20:43:28 2012 -0700"
      },
      "message": "rcu: Move RCU_FAST_NO_HZ per-CPU variables to rcu_dynticks structure\n\nThe RCU_FAST_NO_HZ code relies on a number of per-CPU variables.\nThis works, but is hidden from someone scanning the data structures\nin rcutree.h.  This commit therefore converts these per-CPU variables\nto fields in the per-CPU rcu_dynticks structures.\n\nSuggested-by: Peter Zijlstra \u003cpeterz@infradead.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nTested-by: Heiko Carstens \u003cheiko.carstens@de.ibm.com\u003e\nTested-by: Pascal Chapperon \u003cpascal.chapperon@wanadoo.fr\u003e\n"
    },
    {
      "commit": "dc36be4419311fd57becdf54bfeef6bd04a6741d",
      "tree": "179d34f4e56861b66142dd6c39dac1af1e1e10d9",
      "parents": [
        "b1420f1c8bfc30ecf6380a31d0f686884834b599",
        "048a0e8f5e1d94c01a5fc70f5b2f2fd2f4527326",
        "9dd8fb16c36178df2066387d2abd44d8b4dca8c8",
        "9fab97876af844c2abb7c39300bff34025926565"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri May 11 10:14:09 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri May 11 10:14:21 2012 -0700"
      },
      "message": "Merge branches \u0027barrier.2012.05.09a\u0027, \u0027fixes.2012.04.26a\u0027, \u0027inline.2012.05.02b\u0027 and \u0027srcu.2012.05.07b\u0027 into HEAD\n\nbarrier:  Reduce the amount of disturbance by rcu_barrier() to the rest of\n    \tthe system.  This branch also includes improvements to\n    \tRCU_FAST_NO_HZ, which are included here due to conflicts.\nfixes:  Miscellaneous fixes.\ninline:  Remaining changes from an abortive attempt to inline\n    \tpreemptible RCU\u0027s __rcu_read_lock().  These are (1) making\n    \texit_rcu() avoid unnecessary work and (2) avoiding having\n    \tpreemptible RCU record a blocked thread when the scheduler\n    \tdeclines to do a context switch.\nsrcu:\tLai Jiangshan\u0027s algorithmic implementation of SRCU, including\n    \tcall_srcu().\n"
    },
    {
      "commit": "b1420f1c8bfc30ecf6380a31d0f686884834b599",
      "tree": "56eb378bcd64175a7302a1031b388ecf569a30bb",
      "parents": [
        "98248a0e24327bc64eb7518145c44bff7bebebc3"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Thu Mar 01 13:18:08 2012 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed May 09 14:27:54 2012 -0700"
      },
      "message": "rcu: Make rcu_barrier() less disruptive\n\nThe rcu_barrier() primitive interrupts each and every CPU, registering\na callback on every CPU.  Once all of these callbacks have been invoked,\nrcu_barrier() knows that every callback that was registered before\nthe call to rcu_barrier() has also been invoked.\n\nHowever, there is no point in registering a callback on a CPU that\ncurrently has no callbacks, most especially if that CPU is in a\ndeep idle state.  This commit therefore makes rcu_barrier() avoid\ninterrupting CPUs that have no callbacks.  Doing this requires reworking\nthe handling of orphaned callbacks, otherwise callbacks could slip through\nrcu_barrier()\u0027s net by being orphaned from a CPU that rcu_barrier() had\nnot yet interrupted to a CPU that rcu_barrier() had already interrupted.\nThis reworking was needed anyway to take a first step towards weaning\nRCU from the CPU_DYING notifier\u0027s use of stop_cpu().\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "616c310e83b872024271c915c1b9ab505b9efad9",
      "tree": "1339bc7b3bef920b4641a5af2f182e9dfa2a6632",
      "parents": [
        "66f75a5d028beaf67c931435fdc3e7823125730c"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue Mar 27 16:02:08 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed May 02 14:43:23 2012 -0700"
      },
      "message": "rcu: Move PREEMPT_RCU preemption to switch_to() invocation\n\nCurrently, PREEMPT_RCU readers are enqueued upon entry to the scheduler.\nThis is inefficient because enqueuing is required only if there is a\ncontext switch, and entry to the scheduler does not guarantee a context\nswitch.\n\nThe commit therefore moves the enqueuing to immediately precede the\ncall to switch_to() from the scheduler.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nTested-by: Linus Torvalds \u003ctorvalds@linux-foundation.org\u003e\n"
    },
    {
      "commit": "c57afe80db4e169135eb675acc2d241e26cc064e",
      "tree": "ec011600725a2884efdca6f4c187ea7e3fa4d277",
      "parents": [
        "2ee3dc80660ac8285a37e662fd91b2e45c46f06a"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue Feb 28 11:02:21 2012 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Apr 24 20:55:20 2012 -0700"
      },
      "message": "rcu: Make RCU_FAST_NO_HZ account for pauses out of idle\n\nBoth Steven Rostedt\u0027s new idle-capable trace macros and the RCU_NONIDLE()\nmacro can cause RCU to momentarily pause out of idle without the rest\nof the system being involved.  This can cause rcu_prepare_for_idle()\nto run through its state machine too quickly, which can in turn result\nin needless scheduling-clock interrupts.\n\nThis commit therefore adds code to enable rcu_prepare_for_idle() to\ndistinguish between an initial entry to idle on the one hand (which needs\nto advance the rcu_prepare_for_idle() state machine) and an idle reentry\ndue to idle-capable trace macros and RCU_NONIDLE() on the other hand\n(which should avoid advancing the rcu_prepare_for_idle() state machine).\nAdditional state is maintained to allow the timer to be correctly reposted\nwhen returning after a momentary pause out of idle, and even more state\nis maintained to detect when new non-lazy callbacks have been enqueued\n(which may require re-evaluation of the approach to idleness).\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "8932a63d5edb02f714d50c26583152fe0a97a69c",
      "tree": "ec71159908f1a78eb21e736d284ffe7ed7584b6c",
      "parents": [
        "d8169d4c369e8aa2fda10df705a4957331b5a4db"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Apr 19 12:20:14 2012 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Apr 24 20:54:52 2012 -0700"
      },
      "message": "rcu: Reduce cache-miss initialization latencies for large systems\n\nCommit #0209f649 (rcu: limit rcu_node leaf-level fanout) set an upper\nlimit of 16 on the leaf-level fanout for the rcu_node tree.  This was\nneeded to reduce lock contention that was induced by the synchronization\nof scheduling-clock interrupts, which was in turn needed to improve\nenergy efficiency for moderate-sized lightly loaded servers.\n\nHowever, reducing the leaf-level fanout means that there are more\nleaf-level rcu_node structures in the tree, which in turn means that\nRCU\u0027s grace-period initialization incurs more cache misses.  This is\nnot a problem on moderate-sized servers with only a few tens of CPUs,\nbut becomes a major source of real-time latency spikes on systems with\nmany hundreds of CPUs.  In addition, the workloads running on these large\nsystems tend to be CPU-bound, which eliminates the energy-efficiency\nadvantages of synchronizing scheduling-clock interrupts.  Therefore,\nthese systems need maximal values for the rcu_node leaf-level fanout.\n\nThis commit addresses this problem by introducing a new kernel parameter\nnamed RCU_FANOUT_LEAF that directly controls the leaf-level fanout.\nThis parameter defaults to 16 to handle the common case of a moderate\nsized lightly loaded servers, but may be set higher on larger systems.\n\nReported-by: Mike Galbraith \u003cefault@gmx.de\u003e\nReported-by: Dimitri Sivanich \u003csivanich@sgi.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "2036d94a7b61ca5032ce90f2bda06afec0fe713e",
      "tree": "fc9f4b5ba1058e5a2fdf9ccd187766c90f5ae036",
      "parents": [
        "c5fdcec927ee31fc96e92339c3a83ac6e0725289"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon Jan 30 17:02:47 2012 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Feb 21 09:06:07 2012 -0800"
      },
      "message": "rcu: Rework detection of use of RCU by offline CPUs\n\nBecause newly offlined CPUs continue executing after completing the\nCPU_DYING notifiers, they legitimately enter the scheduler and use\nRCU while appearing to be offline.  This calls for a more sophisticated\napproach as follows:\n\n1.\tRCU marks the CPU online during the CPU_UP_PREPARE phase.\n\n2.\tRCU marks the CPU offline during the CPU_DEAD phase.\n\n3.\tDiagnostics regarding use of read-side RCU by offline CPUs use\n\tRCU\u0027s accounting rather than the cpu_online_map.  (Note that\n\t__call_rcu() still uses cpu_online_map to detect illegal\n\tinvocations within CPU_DYING notifiers.)\n\n4.\tOffline CPUs are prevented from hanging the system by\n\tforce_quiescent_state(), which pays attention to cpu_online_map.\n\tSome additional work (in a later commit) will be needed to\n\tguarantee that force_quiescent_state() waits a full jiffy before\n\tassuming that a CPU is offline, for example, when called from\n\tidle entry.  (This commit also makes the one-jiffy wait\n\texplicit, since the old-style implicit wait can now be defeated\n\tby RCU_FAST_NO_HZ and by rcutorture.)\n\nThis approach avoids the false positives encountered when attempting to\nuse more exact classification of CPU online/offline state.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "a858af2875fb291d0f4b0a4419fefbf03c2379c0",
      "tree": "5183796cbf50ec0cd3bd5c741db15705376dacbd",
      "parents": [
        "13cfcca0e4e2d4cee1d0183c049eb34e54ac976e"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon Jan 16 13:29:10 2012 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Feb 21 09:03:49 2012 -0800"
      },
      "message": "rcu: Print scheduling-clock information on RCU CPU stall-warning messages\n\nThere have been situations where RCU CPU stall warnings were caused by\nissues in scheduling-clock timer initialization.  To make it easier to\ntrack these down, this commit causes the RCU CPU stall-warning messages\nto print out the number of scheduling-clock interrupts taken in the\ncurrent grace period for each stalled CPU.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "13cfcca0e4e2d4cee1d0183c049eb34e54ac976e",
      "tree": "2aa48f0db717ae7741602022e4020f22cc3cea7f",
      "parents": [
        "27565d64a4e564e72c22d8c91a3cfcb9442383e8"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Jan 13 15:32:18 2012 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Feb 21 09:03:48 2012 -0800"
      },
      "message": "rcu: Set RCU CPU stall times via sysfs\n\nThe default CONFIG_RCU_CPU_STALL_TIMEOUT value of 60 seconds has served\nLinux users well for production use for quite some time.  However, for\ndebugging, there will be more than three minutes between subsequent\nstall-warning messages.  This can be an annoyingly long wait if you\nare trying to work out where the offending infinite loop is hiding.\n\nTherefore, this commit provides a rcu_cpu_stall_timeout sysfs\nparameter that may be adjusted at boot time and at runtime to speed\nup debugging.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "30fbcc90b02187c55c57ff0ecf57cecbd487d694",
      "tree": "866824e1972d900ceda045c93a3958c74ffbf1e9",
      "parents": [
        "1aa03f1188f7b0b85df2de602b33ee7b6fab8e00"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Thu Jan 12 11:01:14 2012 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Feb 21 09:03:44 2012 -0800"
      },
      "message": "rcu: Clean up straggling rcu_preempt_needs_cpu() name\n\nThe recent updates to RCU_CPU_FAST_NO_HZ have an rcu_needs_cpu() that\ndoes more than just check for callbacks, so get the name for\nrcu_preempt_needs_cpu() consistent with that change, now calling it\nrcu_preempt_cpu_has_callbacks().\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "e5601400081651060a59bd1f45f2821bb8e97f95",
      "tree": "391e7e0b08d8b642eca260950c7f052832411aa9",
      "parents": [
        "ae1f18e480c83d15539fb234a2dc5f0aa04cb119"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Sat Jan 07 11:03:57 2012 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Feb 21 09:03:34 2012 -0800"
      },
      "message": "rcu: Simplify offline processing\n\nMove -\u003eqsmaskinit and blkd_tasks[] manipulation to the CPU_DYING\nnotifier.  This simplifies the code by eliminating a potential\ndeadlock and by reducing the responsibilities of force_quiescent_state().\nAlso rename functions to make their connection to the CPU-hotplug\nstages explicit.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "486e259340fc4c60474f2c14703e3b3634bb58ca",
      "tree": "70a58702194588fa0773463523f72c682785d040",
      "parents": [
        "0bb7b59d6e2b8440cd7097097dd4bbfc4d76ed07"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Fri Jan 06 14:11:30 2012 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Feb 21 09:03:25 2012 -0800"
      },
      "message": "rcu: Avoid waking up CPUs having only kfree_rcu() callbacks\n\nWhen CONFIG_RCU_FAST_NO_HZ is enabled, RCU will allow a given CPU to\nenter dyntick-idle mode even if it still has RCU callbacks queued.\nRCU avoids system hangs in this case by scheduling a timer for several\njiffies in the future.  However, if all of the callbacks on that CPU\nare from kfree_rcu(), there is no reason to wake the CPU up, as it is\nnot a problem to defer freeing of memory.\n\nThis commit therefore tracks the number of callbacks on a given CPU\nthat are from kfree_rcu(), and avoids scheduling the timer if all of\na given CPU\u0027s callbacks are from kfree_rcu().\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "dff1672d9199fffddb58fa7970ccf59005fc35f3",
      "tree": "a9740f65dfc203d183cb06ce0faeed0de5cef58b",
      "parents": [
        "facc4e159672b4ed10aa18147bfa187b013c9505"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue Nov 29 15:57:13 2011 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Dec 11 10:32:09 2011 -0800"
      },
      "message": "rcu: Keep invoking callbacks if CPU otherwise idle\n\nThe rcu_do_batch() function that invokes callbacks for TREE_RCU and\nTREE_PREEMPT_RCU normally throttles callback invocation to avoid degrading\nscheduling latency.  However, as long as the CPU would otherwise be idle,\nthere is no downside to continuing to invoke any callbacks that have passed\nthrough their grace periods.  In fact, processing such callbacks in a\ntimely manner has the benefit of increasing the probability that the\nCPU can enter the power-saving dyntick-idle mode.\n\nTherefore, this commit allows callback invocation to continue beyond the\npreset limit as long as the scheduler does not have some other task to\nrun and as long as context is that of the idle task or the relevant\nRCU kthread.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "7cb92499000e3c86dae653077b1465458a039ef6",
      "tree": "ebc982a5cc562b4fe0cb8f20541f45a5506a0b5f",
      "parents": [
        "3842a0832a1d6eb0b31421f8810a813135967512"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon Nov 28 12:28:34 2011 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Dec 11 10:32:07 2011 -0800"
      },
      "message": "rcu: Permit dyntick-idle with callbacks pending\n\nThe current implementation of RCU_FAST_NO_HZ prevents CPUs from entering\ndyntick-idle state if they have RCU callbacks pending.  Unfortunately,\nthis has the side-effect of often preventing them from entering this\nstate, especially if at least one other CPU is not in dyntick-idle state.\nHowever, the resulting per-tick wakeup is wasteful in many cases: if the\nCPU has already fully responded to the current RCU grace period, there\nwill be nothing for it to do until this grace period ends, which will\nfrequently take several jiffies.\n\nThis commit therefore permits a CPU that has done everything that the\ncurrent grace period has asked of it (rcu_pending() \u003d\u003d 0) even if it\nstill as RCU callbacks pending.  However, such a CPU posts a timer to\nwake it up several jiffies later (6 jiffies, based on experience with\ngrace-period lengths).  This wakeup is required to handle situations\nthat can result in all CPUs being in dyntick-idle mode, thus failing\nto ever complete the current grace period.  If a CPU wakes up before\nthe timer goes off, then it cancels that timer, thus avoiding spurious\nwakeups.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "f535a607c13c7b674e0788ca5765779aa74a01c3",
      "tree": "433a07d16ff11d9f67e7991831cebf3cadfd9939",
      "parents": [
        "84ad00cb61f1cb21f0b63bc6f7dc254399eb3830"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue Nov 22 20:43:02 2011 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Dec 11 10:32:02 2011 -0800"
      },
      "message": "rcu: Eliminate RCU_FAST_NO_HZ grace-period hang\n\nWith the new implementation of RCU_FAST_NO_HZ, it was possible to hang\nRCU grace periods as follows:\n\no\tCPU 0 attempts to go idle, cycles several times through the\n\trcu_prepare_for_idle() loop, then goes dyntick-idle when\n\tRCU needs nothing more from it, while still having at least\n\ton RCU callback pending.\n\no\tCPU 1 goes idle with no callbacks.\n\nBoth CPUs can then stay in dyntick-idle mode indefinitely, preventing\nthe RCU grace period from ever completing, possibly hanging the system.\n\nThis commit therefore prevents CPUs that have RCU callbacks from entering\ndyntick-idle mode.  This approach also eliminates the need for the\nend-of-grace-period IPIs used previously.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "aea1b35e29e658d42d7ba2237f3aa7f93e18509d",
      "tree": "0221b1c12b5c3e3ed7f2bb2ffc957b09891bcb51",
      "parents": [
        "0989cb46783188ea7346ba6490be0046b9b7a725"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Wed Nov 02 06:54:54 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Dec 11 10:31:43 2011 -0800"
      },
      "message": "rcu: Allow dyntick-idle mode for CPUs with callbacks\n\nCurrently, RCU does not permit a CPU to enter dyntick-idle mode if that\nCPU has any RCU callbacks queued.  This means that workloads for which\neach CPU wakes up and does some RCU updates every few ticks will never\nenter dyntick-idle mode.  This can result in significant unnecessary power\nconsumption, so this patch permits a given to enter dyntick-idle mode if\nit has callbacks, but only if that same CPU has completed all current\nwork for the RCU core.  We determine use rcu_pending() to determine\nwhether a given CPU has completed all current work for the RCU core.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "b40d293eb36ba40cd428b6d178db911174689702",
      "tree": "78109a13c0bf86608f3caaea547fd9e948aee743",
      "parents": [
        "34240697d619c439c55f21989680024dcb604aab"
      ],
      "author": {
        "name": "Thomas Gleixner",
        "email": "tglx@linutronix.de",
        "time": "Sat Oct 22 07:12:34 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Dec 11 10:31:28 2011 -0800"
      },
      "message": "rcu: Omit self-awaken when setting up expedited grace period\n\nWhen setting up an expedited grace period, if there were no readers, the\ntask will awaken itself.  This commit removes this useless self-awakening.\n\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "9b2e4f1880b789be1f24f9684f7a54b90310b5c0",
      "tree": "1fa922e0616e298837a7079cb49118188a58186c",
      "parents": [
        "b804cb9e91c6c304959c69d4f9daeef4ffdba71c"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Fri Sep 30 12:10:22 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Dec 11 10:31:24 2011 -0800"
      },
      "message": "rcu: Track idleness independent of idle tasks\n\nEarlier versions of RCU used the scheduling-clock tick to detect idleness\nby checking for the idle task, but handled idleness differently for\nCONFIG_NO_HZ\u003dy.  But there are now a number of uses of RCU read-side\ncritical sections in the idle task, for example, for tracing.  A more\nfine-grained detection of idleness is therefore required.\n\nThis commit presses the old dyntick-idle code into full-time service,\nso that rcu_idle_enter(), previously known as rcu_enter_nohz(), is\nalways invoked at the beginning of an idle loop iteration.  Similarly,\nrcu_idle_exit(), previously known as rcu_exit_nohz(), is always invoked\nat the end of an idle-loop iteration.  This allows the idle task to\nuse RCU everywhere except between consecutive rcu_idle_enter() and\nrcu_idle_exit() calls, in turn allowing architecture maintainers to\nspecify exactly where in the idle loop that RCU may be used.\n\nBecause some of the userspace upcall uses can result in what looks\nto RCU like half of an interrupt, it is not possible to expect that\nthe irq_enter() and irq_exit() hooks will give exact counts.  This\npatch therefore expands the -\u003edynticks_nesting counter to 64 bits\nand uses two separate bitfields to count process/idle transitions\nand interrupt entry/exit transitions.  It is presumed that userspace\nupcalls do not happen in the idle loop or from usermode execution\n(though usermode might do a system call that results in an upcall).\nThe counter is hard-reset on each process/idle transition, which\navoids the interrupt entry/exit error from accumulating.  Overflow\nis avoided by the 64-bitness of the -\u003edyntick_nesting counter.\n\nThis commit also adds warnings if a non-idle task asks RCU to enter\nidle state (and these checks will need some adjustment before applying\nFrederic\u0027s OS-jitter patches (http://lkml.org/lkml/2011/10/7/246).\nIn addition, validation of -\u003edynticks and -\u003edynticks_nesting is added.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "af446b702c58b700cc5fa99f6edc78b99e55b995",
      "tree": "0eacf146b7f1b221e844c52db6061e31928ff99e",
      "parents": [
        "dc47ce90c3a822cd7c9e9339fe4d5f61dcb26b50"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat Sep 10 21:54:08 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Dec 11 10:31:20 2011 -0800"
      },
      "message": "rcu: -\u003esignaled better named -\u003efqs_state\n\nThe -\u003esignaled field was named before complications in the form of\ndyntick-idle mode and offlined CPUs.  These complications have required\nthat force_quiescent_state() be implemented as a state machine, instead\nof simply unconditionally sending reschedule IPIs.  Therefore, this\ncommit renames -\u003esignaled to -\u003efqs_state to catch up with the new\nforce_quiescent_state() reality.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "e90c53d3e238dd0b7b02964370e8fece1778df96",
      "tree": "23e5b8623c2c37bd8a4656c66266209872f80701",
      "parents": [
        "5b61b0baa9e80289c53413e573befc5790a04ac7"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat Aug 20 18:29:32 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Sep 28 21:38:48 2011 -0700"
      },
      "message": "rcu: Remove rcu_needs_cpu_flush() to avoid false quiescent states\n\nThe purpose of rcu_needs_cpu_flush() was to iterate on pushing the\ncurrent grace period in order to help the current CPU enter dyntick-idle\nmode.  However, this can result in failures if the CPU starts entering\ndyntick-idle mode, but then backs out.  In this case, the call to\nrcu_pending() from rcu_needs_cpu_flush() might end up announcing a\nnon-existing quiescent state.\n\nThis commit therefore removes rcu_needs_cpu_flush() in favor of letting\nthe dyntick-idle machinery at the end of the softirq handler push the\nloop along via its call to rcu_pending().\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "9bc8b5586f94be6391458074ecbba8827ba8ba9d",
      "tree": "323804bb7180337c266f88519cea6b1f42114ead",
      "parents": [
        "037067a1b6f9a70f862f3ed9d59fe28b7cd55ac4"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat Aug 13 13:31:47 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Sep 28 21:38:41 2011 -0700"
      },
      "message": "rcu: Suppress NMI backtraces when stall ends before dump\n\nIt is possible for an RCU CPU stall to end just as it is detected, in\nwhich case the current code will uselessly dump all CPU\u0027s stacks.\nThis commit therefore checks for this condition and refrains from\nsending needless NMIs.\n\nAnd yes, the stall might also end just after we checked all CPUs and\ntasks, but in that case we would at least have given some clue as\nto which CPU/task was at fault.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "e4cc1f22b2f4e9b0207a8cdb63e56dcf99e82d35",
      "tree": "ec3fad6587f0a83e764a571394bdfb85a84edf30",
      "parents": [
        "d4c08f2ac311a360230eef7e5395b0ec8d8f0670"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon Jun 27 00:17:43 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Sep 28 21:38:22 2011 -0700"
      },
      "message": "rcu: Simplify quiescent-state accounting\n\nThere is often a delay between the time that a CPU passes through a\nquiescent state and the time that this quiescent state is reported to the\nRCU core.  It is quite possible that the grace period ended before the\nquiescent state could be reported, for example, some other CPU might have\ndeduced that this CPU passed through dyntick-idle mode.  It is critically\nimportant that quiescent state be counted only against the grace period\nthat was in effect at the time that the quiescent state was detected.\n\nPreviously, this was handled by recording the number of the last grace\nperiod to complete when passing through a quiescent state.  The RCU\ncore then checks this number against the current value, and rejects\nthe quiescent state if there is a mismatch.  However, one additional\npossibility must be accounted for, namely that the quiescent state was\nrecorded after the prior grace period completed but before the current\ngrace period started.  In this case, the RCU core must reject the\nquiescent state, but the recorded number will match.  This is handled\nwhen the CPU becomes aware of a new grace period -- at that point,\nit invalidates any prior quiescent state.\n\nThis works, but is a bit indirect.  The new approach records the current\ngrace period, and the RCU core checks to see (1) that this is still the\ncurrent grace period and (2) that this grace period has not yet ended.\nThis approach simplifies reasoning about correctness, and this commit\nchanges over to this new approach.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "d4c08f2ac311a360230eef7e5395b0ec8d8f0670",
      "tree": "06e425b8153e076fbe43b037cf4497ac50afddb7",
      "parents": [
        "965a002b4f1a458c5dcb334ec29f48a0046faa25"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Sat Jun 25 06:36:56 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Sep 28 21:38:21 2011 -0700"
      },
      "message": "rcu: Add grace-period, quiescent-state, and call_rcu trace events\n\nAdd trace events to record grace-period start and end, quiescent states,\nCPUs noticing grace-period start and end, grace-period initialization,\ncall_rcu() invocation, tasks blocking in RCU read-side critical sections,\ntasks exiting those same critical sections, force_quiescent_state()\ndetection of dyntick-idle and offline CPUs, CPUs entering and leaving\ndyntick-idle mode (except from NMIs), CPUs coming online and going\noffline, and CPUs being kicked for staying in dyntick-idle mode for too\nlong (as in many weeks, even on 32-bit systems).\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n\nrcu: Add the rcu flavor to callback trace events\n\nThe earlier trace events for registering RCU callbacks and for invoking\nthem did not include the RCU flavor (rcu_bh, rcu_preempt, or rcu_sched).\nThis commit adds the RCU flavor to those trace events.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "eab0993c7ba5c7d9b3613d6037e0f31f0ccbe181",
      "tree": "9f37a94506e2c58d7d0139374bc21b64b9e073ed",
      "parents": [
        "e0f23060adfa3f27beaa7918eff70258b88471b6"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue Jun 21 01:59:33 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Sep 28 21:38:18 2011 -0700"
      },
      "message": "rcu: Move RCU_BOOST declarations to allow compiler checking\n\nAndi Kleen noticed that one of the RCU_BOOST data declarations was\nout of sync with the definition.  Move the declarations so that the\ncompiler can do the checking in the future.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "f8b7fc6b514f34a51875dd48dff70d4d17a54f38",
      "tree": "dc6583851e3536516761b0fd9b07f5a3a1743ebb",
      "parents": [
        "a46e0899eec7a3069bcadd45dfba7bf67c6ed016"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Thu Jun 16 08:26:32 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Jun 16 16:12:05 2011 -0700"
      },
      "message": "rcu: Move RCU_BOOST #ifdefs to header file\n\nThe commit \"use softirq instead of kthreads except when RCU_BOOST\u003dy\"\njust applied #ifdef in place.  This commit is a cleanup that moves\nthe newly #ifdef\u0027ed code to the header file kernel/rcutree_plugin.h.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "a46e0899eec7a3069bcadd45dfba7bf67c6ed016",
      "tree": "78158b4056fe1365d5086f66769abdc3ef2643c3",
      "parents": [
        "09223371deac67d08ca0b70bd18787920284c967"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Jun 15 15:47:09 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Jun 15 23:07:21 2011 -0700"
      },
      "message": "rcu: use softirq instead of kthreads except when RCU_BOOST\u003dy\n\nThis patch #ifdefs RCU kthreads out of the kernel unless RCU_BOOST\u003dy,\nthus eliminating context-switch overhead if RCU priority boosting has\nnot been configured.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "09223371deac67d08ca0b70bd18787920284c967",
      "tree": "0ad0354a93ac209c8cfd2b79d03d0462aa3c5c58",
      "parents": [
        "9a432736904d386cda28b987b38ba14dae960ecc"
      ],
      "author": {
        "name": "Shaohua Li",
        "email": "shaohua.li@intel.com",
        "time": "Tue Jun 14 13:26:25 2011 +0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Jun 14 15:25:39 2011 -0700"
      },
      "message": "rcu: Use softirq to address performance regression\n\nCommit a26ac2455ffcf3(rcu: move TREE_RCU from softirq to kthread)\nintroduced performance regression. In an AIM7 test, this commit degraded\nperformance by about 40%.\n\nThe commit runs rcu callbacks in a kthread instead of softirq. We observed\nhigh rate of context switch which is caused by this. Out test system has\n64 CPUs and HZ is 1000, so we saw more than 64k context switch per second\nwhich is caused by RCU\u0027s per-CPU kthread.  A trace showed that most of\nthe time the RCU per-CPU kthread doesn\u0027t actually handle any callbacks,\nbut instead just does a very small amount of work handling grace periods.\nThis means that RCU\u0027s per-CPU kthreads are making the scheduler do quite\na bit of work in order to allow a very small amount of RCU-related\nprocessing to be done.\n\nAlex Shi\u0027s analysis determined that this slowdown is due to lock\ncontention within the scheduler.  Unfortunately, as Peter Zijlstra points\nout, the scheduler\u0027s real-time semantics require global action, which\nmeans that this contention is inherent in real-time scheduling.  (Yes,\nperhaps someone will come up with a workaround -- otherwise, -rt is not\ngoing to do well on large SMP systems -- but this patch will work around\nthis issue in the meantime.  And \"the meantime\" might well be forever.)\n\nThis patch therefore re-introduces softirq processing to RCU, but only\nfor core RCU work.  RCU callbacks are still executed in kthread context,\nso that only a small amount of RCU work runs in softirq context in the\ncommon case.  This should minimize ksoftirqd execution, allowing us to\nskip boosting of ksoftirqd for CONFIG_RCU_BOOST\u003dy kernels.\n\nSigned-off-by: Shaohua Li \u003cshaohua.li@intel.com\u003e\nTested-by: \"Alex,Shi\" \u003calex.shi@intel.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "08bca60a6912ad225254250c0a9c3a05b4152cfa",
      "tree": "760b20e6eaaa02412fcecb6bc5c3598b6bc0fdce",
      "parents": [
        "8826f3b0397562eee6f8785d548be9dfdb169100"
      ],
      "author": {
        "name": "Peter Zijlstra",
        "email": "a.p.zijlstra@chello.nl",
        "time": "Fri May 20 16:06:29 2011 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sat May 28 17:41:52 2011 +0200"
      },
      "message": "rcu: Remove waitqueue usage for cpu, node, and boost kthreads\n\nIt is not necessary to use waitqueues for the RCU kthreads because\nwe always know exactly which thread is to be awakened.  In addition,\nwake_up() only issues an actual wakeup when there is a thread waiting on\nthe queue, which was why there was an extra explicit wake_up_process()\nto get the RCU kthreads started.\n\nEliminating the waitqueues (and wake_up()) in favor of wake_up_process()\neliminates the need for the initial wake_up_process() and also shrinks\nthe data structure size a bit.  The wakeup logic is placed in a new\nrcu_wait() macro.\n\nSigned-off-by: Peter Zijlstra \u003ca.p.zijlstra@chello.nl\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "8826f3b0397562eee6f8785d548be9dfdb169100",
      "tree": "3b911e0ffe56b1792126f3f36f1fa4de39fd5979",
      "parents": [
        "55c2945aa9d4d907ec5ca4f6a4e30ae908d8d30d"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Wed May 11 05:41:41 2011 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sat May 28 17:41:49 2011 +0200"
      },
      "message": "rcu: Avoid acquiring rcu_node locks in timer functions\n\nThis commit switches manipulations of the rcu_node -\u003ewakemask field\nto atomic operations, which allows rcu_cpu_kthread_timer() to avoid\nacquiring the rcu_node lock.  This should avoid the following lockdep\nsplat reported by Valdis Kletnieks:\n\n[   12.872150] usb 1-4: new high speed USB device number 3 using ehci_hcd\n[   12.986667] usb 1-4: New USB device found, idVendor\u003d413c, idProduct\u003d2513\n[   12.986679] usb 1-4: New USB device strings: Mfr\u003d0, Product\u003d0, SerialNumber\u003d0\n[   12.987691] hub 1-4:1.0: USB hub found\n[   12.987877] hub 1-4:1.0: 3 ports detected\n[   12.996372] input: PS/2 Generic Mouse as /devices/platform/i8042/serio1/input/input10\n[   13.071471] udevadm used greatest stack depth: 3984 bytes left\n[   13.172129]\n[   13.172130] \u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\u003d\n[   13.172425] [ INFO: possible circular locking dependency detected ]\n[   13.172650] 2.6.39-rc6-mmotm0506 #1\n[   13.172773] -------------------------------------------------------\n[   13.172997] blkid/267 is trying to acquire lock:\n[   13.173009]  (\u0026p-\u003epi_lock){-.-.-.}, at: [\u003cffffffff81032d8f\u003e] try_to_wake_up+0x29/0x1aa\n[   13.173009]\n[   13.173009] but task is already holding lock:\n[   13.173009]  (rcu_node_level_0){..-...}, at: [\u003cffffffff810901cc\u003e] rcu_cpu_kthread_timer+0x27/0x58\n[   13.173009]\n[   13.173009] which lock already depends on the new lock.\n[   13.173009]\n[   13.173009]\n[   13.173009] the existing dependency chain (in reverse order) is:\n[   13.173009]\n[   13.173009] -\u003e #2 (rcu_node_level_0){..-...}:\n[   13.173009]        [\u003cffffffff810679b9\u003e] check_prevs_add+0x8b/0x104\n[   13.173009]        [\u003cffffffff81067da1\u003e] validate_chain+0x36f/0x3ab\n[   13.173009]        [\u003cffffffff8106846b\u003e] __lock_acquire+0x369/0x3e2\n[   13.173009]        [\u003cffffffff81068a0f\u003e] lock_acquire+0xfc/0x14c\n[   13.173009]        [\u003cffffffff815697f1\u003e] _raw_spin_lock+0x36/0x45\n[   13.173009]        [\u003cffffffff81090794\u003e] rcu_read_unlock_special+0x8c/0x1d5\n[   13.173009]        [\u003cffffffff8109092c\u003e] __rcu_read_unlock+0x4f/0xd7\n[   13.173009]        [\u003cffffffff81027bd3\u003e] rcu_read_unlock+0x21/0x23\n[   13.173009]        [\u003cffffffff8102cc34\u003e] cpuacct_charge+0x6c/0x75\n[   13.173009]        [\u003cffffffff81030cc6\u003e] update_curr+0x101/0x12e\n[   13.173009]        [\u003cffffffff810311d0\u003e] check_preempt_wakeup+0xf7/0x23b\n[   13.173009]        [\u003cffffffff8102acb3\u003e] check_preempt_curr+0x2b/0x68\n[   13.173009]        [\u003cffffffff81031d40\u003e] ttwu_do_wakeup+0x76/0x128\n[   13.173009]        [\u003cffffffff81031e49\u003e] ttwu_do_activate.constprop.63+0x57/0x5c\n[   13.173009]        [\u003cffffffff81031e96\u003e] scheduler_ipi+0x48/0x5d\n[   13.173009]        [\u003cffffffff810177d5\u003e] smp_reschedule_interrupt+0x16/0x18\n[   13.173009]        [\u003cffffffff815710f3\u003e] reschedule_interrupt+0x13/0x20\n[   13.173009]        [\u003cffffffff810b66d1\u003e] rcu_read_unlock+0x21/0x23\n[   13.173009]        [\u003cffffffff810b739c\u003e] find_get_page+0xa9/0xb9\n[   13.173009]        [\u003cffffffff810b8b48\u003e] filemap_fault+0x6a/0x34d\n[   13.173009]        [\u003cffffffff810d1a25\u003e] __do_fault+0x54/0x3e6\n[   13.173009]        [\u003cffffffff810d447a\u003e] handle_pte_fault+0x12c/0x1ed\n[   13.173009]        [\u003cffffffff810d48f7\u003e] handle_mm_fault+0x1cd/0x1e0\n[   13.173009]        [\u003cffffffff8156cfee\u003e] do_page_fault+0x42d/0x5de\n[   13.173009]        [\u003cffffffff8156a75f\u003e] page_fault+0x1f/0x30\n[   13.173009]\n[   13.173009] -\u003e #1 (\u0026rq-\u003elock){-.-.-.}:\n[   13.173009]        [\u003cffffffff810679b9\u003e] check_prevs_add+0x8b/0x104\n[   13.173009]        [\u003cffffffff81067da1\u003e] validate_chain+0x36f/0x3ab\n[   13.173009]        [\u003cffffffff8106846b\u003e] __lock_acquire+0x369/0x3e2\n[   13.173009]        [\u003cffffffff81068a0f\u003e] lock_acquire+0xfc/0x14c\n[   13.173009]        [\u003cffffffff815697f1\u003e] _raw_spin_lock+0x36/0x45\n[   13.173009]        [\u003cffffffff81027e19\u003e] __task_rq_lock+0x8b/0xd3\n[   13.173009]        [\u003cffffffff81032f7f\u003e] wake_up_new_task+0x41/0x108\n[   13.173009]        [\u003cffffffff810376c3\u003e] do_fork+0x265/0x33f\n[   13.173009]        [\u003cffffffff81007d02\u003e] kernel_thread+0x6b/0x6d\n[   13.173009]        [\u003cffffffff8153a9dd\u003e] rest_init+0x21/0xd2\n[   13.173009]        [\u003cffffffff81b1db4f\u003e] start_kernel+0x3bb/0x3c6\n[   13.173009]        [\u003cffffffff81b1d29f\u003e] x86_64_start_reservations+0xaf/0xb3\n[   13.173009]        [\u003cffffffff81b1d393\u003e] x86_64_start_kernel+0xf0/0xf7\n[   13.173009]\n[   13.173009] -\u003e #0 (\u0026p-\u003epi_lock){-.-.-.}:\n[   13.173009]        [\u003cffffffff81067788\u003e] check_prev_add+0x68/0x20e\n[   13.173009]        [\u003cffffffff810679b9\u003e] check_prevs_add+0x8b/0x104\n[   13.173009]        [\u003cffffffff81067da1\u003e] validate_chain+0x36f/0x3ab\n[   13.173009]        [\u003cffffffff8106846b\u003e] __lock_acquire+0x369/0x3e2\n[   13.173009]        [\u003cffffffff81068a0f\u003e] lock_acquire+0xfc/0x14c\n[   13.173009]        [\u003cffffffff815698ea\u003e] _raw_spin_lock_irqsave+0x44/0x57\n[   13.173009]        [\u003cffffffff81032d8f\u003e] try_to_wake_up+0x29/0x1aa\n[   13.173009]        [\u003cffffffff81032f3c\u003e] wake_up_process+0x10/0x12\n[   13.173009]        [\u003cffffffff810901e9\u003e] rcu_cpu_kthread_timer+0x44/0x58\n[   13.173009]        [\u003cffffffff81045286\u003e] call_timer_fn+0xac/0x1e9\n[   13.173009]        [\u003cffffffff8104556d\u003e] run_timer_softirq+0x1aa/0x1f2\n[   13.173009]        [\u003cffffffff8103e487\u003e] __do_softirq+0x109/0x26a\n[   13.173009]        [\u003cffffffff8157144c\u003e] call_softirq+0x1c/0x30\n[   13.173009]        [\u003cffffffff81003207\u003e] do_softirq+0x44/0xf1\n[   13.173009]        [\u003cffffffff8103e8b9\u003e] irq_exit+0x58/0xc8\n[   13.173009]        [\u003cffffffff81017f5a\u003e] smp_apic_timer_interrupt+0x79/0x87\n[   13.173009]        [\u003cffffffff81570fd3\u003e] apic_timer_interrupt+0x13/0x20\n[   13.173009]        [\u003cffffffff810bd51a\u003e] get_page_from_freelist+0x2aa/0x310\n[   13.173009]        [\u003cffffffff810bdf03\u003e] __alloc_pages_nodemask+0x178/0x243\n[   13.173009]        [\u003cffffffff8101fe2f\u003e] pte_alloc_one+0x1e/0x3a\n[   13.173009]        [\u003cffffffff810d27fe\u003e] __pte_alloc+0x22/0x14b\n[   13.173009]        [\u003cffffffff810d48a8\u003e] handle_mm_fault+0x17e/0x1e0\n[   13.173009]        [\u003cffffffff8156cfee\u003e] do_page_fault+0x42d/0x5de\n[   13.173009]        [\u003cffffffff8156a75f\u003e] page_fault+0x1f/0x30\n[   13.173009]\n[   13.173009] other info that might help us debug this:\n[   13.173009]\n[   13.173009] Chain exists of:\n[   13.173009]   \u0026p-\u003epi_lock --\u003e \u0026rq-\u003elock --\u003e rcu_node_level_0\n[   13.173009]\n[   13.173009]  Possible unsafe locking scenario:\n[   13.173009]\n[   13.173009]        CPU0                    CPU1\n[   13.173009]        ----                    ----\n[   13.173009]   lock(rcu_node_level_0);\n[   13.173009]                                lock(\u0026rq-\u003elock);\n[   13.173009]                                lock(rcu_node_level_0);\n[   13.173009]   lock(\u0026p-\u003epi_lock);\n[   13.173009]\n[   13.173009]  *** DEADLOCK ***\n[   13.173009]\n[   13.173009] 3 locks held by blkid/267:\n[   13.173009]  #0:  (\u0026mm-\u003emmap_sem){++++++}, at: [\u003cffffffff8156cdb4\u003e] do_page_fault+0x1f3/0x5de\n[   13.173009]  #1:  (\u0026yield_timer){+.-...}, at: [\u003cffffffff810451da\u003e] call_timer_fn+0x0/0x1e9\n[   13.173009]  #2:  (rcu_node_level_0){..-...}, at: [\u003cffffffff810901cc\u003e] rcu_cpu_kthread_timer+0x27/0x58\n[   13.173009]\n[   13.173009] stack backtrace:\n[   13.173009] Pid: 267, comm: blkid Not tainted 2.6.39-rc6-mmotm0506 #1\n[   13.173009] Call Trace:\n[   13.173009]  \u003cIRQ\u003e  [\u003cffffffff8154a529\u003e] print_circular_bug+0xc8/0xd9\n[   13.173009]  [\u003cffffffff81067788\u003e] check_prev_add+0x68/0x20e\n[   13.173009]  [\u003cffffffff8100c861\u003e] ? save_stack_trace+0x28/0x46\n[   13.173009]  [\u003cffffffff810679b9\u003e] check_prevs_add+0x8b/0x104\n[   13.173009]  [\u003cffffffff81067da1\u003e] validate_chain+0x36f/0x3ab\n[   13.173009]  [\u003cffffffff8106846b\u003e] __lock_acquire+0x369/0x3e2\n[   13.173009]  [\u003cffffffff81032d8f\u003e] ? try_to_wake_up+0x29/0x1aa\n[   13.173009]  [\u003cffffffff81068a0f\u003e] lock_acquire+0xfc/0x14c\n[   13.173009]  [\u003cffffffff81032d8f\u003e] ? try_to_wake_up+0x29/0x1aa\n[   13.173009]  [\u003cffffffff810901a5\u003e] ? rcu_check_quiescent_state+0x82/0x82\n[   13.173009]  [\u003cffffffff815698ea\u003e] _raw_spin_lock_irqsave+0x44/0x57\n[   13.173009]  [\u003cffffffff81032d8f\u003e] ? try_to_wake_up+0x29/0x1aa\n[   13.173009]  [\u003cffffffff81032d8f\u003e] try_to_wake_up+0x29/0x1aa\n[   13.173009]  [\u003cffffffff810901a5\u003e] ? rcu_check_quiescent_state+0x82/0x82\n[   13.173009]  [\u003cffffffff81032f3c\u003e] wake_up_process+0x10/0x12\n[   13.173009]  [\u003cffffffff810901e9\u003e] rcu_cpu_kthread_timer+0x44/0x58\n[   13.173009]  [\u003cffffffff810901a5\u003e] ? rcu_check_quiescent_state+0x82/0x82\n[   13.173009]  [\u003cffffffff81045286\u003e] call_timer_fn+0xac/0x1e9\n[   13.173009]  [\u003cffffffff810451da\u003e] ? del_timer+0x75/0x75\n[   13.173009]  [\u003cffffffff810901a5\u003e] ? rcu_check_quiescent_state+0x82/0x82\n[   13.173009]  [\u003cffffffff8104556d\u003e] run_timer_softirq+0x1aa/0x1f2\n[   13.173009]  [\u003cffffffff8103e487\u003e] __do_softirq+0x109/0x26a\n[   13.173009]  [\u003cffffffff8106365f\u003e] ? tick_dev_program_event+0x37/0xf6\n[   13.173009]  [\u003cffffffff810a0e4a\u003e] ? time_hardirqs_off+0x1b/0x2f\n[   13.173009]  [\u003cffffffff8157144c\u003e] call_softirq+0x1c/0x30\n[   13.173009]  [\u003cffffffff81003207\u003e] do_softirq+0x44/0xf1\n[   13.173009]  [\u003cffffffff8103e8b9\u003e] irq_exit+0x58/0xc8\n[   13.173009]  [\u003cffffffff81017f5a\u003e] smp_apic_timer_interrupt+0x79/0x87\n[   13.173009]  [\u003cffffffff81570fd3\u003e] apic_timer_interrupt+0x13/0x20\n[   13.173009]  \u003cEOI\u003e  [\u003cffffffff810bd384\u003e] ? get_page_from_freelist+0x114/0x310\n[   13.173009]  [\u003cffffffff810bd51a\u003e] ? get_page_from_freelist+0x2aa/0x310\n[   13.173009]  [\u003cffffffff812220e7\u003e] ? clear_page_c+0x7/0x10\n[   13.173009]  [\u003cffffffff810bd1ef\u003e] ? prep_new_page+0x14c/0x1cd\n[   13.173009]  [\u003cffffffff810bd51a\u003e] get_page_from_freelist+0x2aa/0x310\n[   13.173009]  [\u003cffffffff810bdf03\u003e] __alloc_pages_nodemask+0x178/0x243\n[   13.173009]  [\u003cffffffff810d46b9\u003e] ? __pmd_alloc+0x87/0x99\n[   13.173009]  [\u003cffffffff8101fe2f\u003e] pte_alloc_one+0x1e/0x3a\n[   13.173009]  [\u003cffffffff810d46b9\u003e] ? __pmd_alloc+0x87/0x99\n[   13.173009]  [\u003cffffffff810d27fe\u003e] __pte_alloc+0x22/0x14b\n[   13.173009]  [\u003cffffffff810d48a8\u003e] handle_mm_fault+0x17e/0x1e0\n[   13.173009]  [\u003cffffffff8156cfee\u003e] do_page_fault+0x42d/0x5de\n[   13.173009]  [\u003cffffffff810d915f\u003e] ? sys_brk+0x32/0x10c\n[   13.173009]  [\u003cffffffff810a0e4a\u003e] ? time_hardirqs_off+0x1b/0x2f\n[   13.173009]  [\u003cffffffff81065c4f\u003e] ? trace_hardirqs_off_caller+0x3f/0x9c\n[   13.173009]  [\u003cffffffff812235dd\u003e] ? trace_hardirqs_off_thunk+0x3a/0x3c\n[   13.173009]  [\u003cffffffff8156a75f\u003e] page_fault+0x1f/0x30\n[   14.010075] usb 5-1: new full speed USB device number 2 using uhci_hcd\n\nReported-by: Valdis Kletnieks \u003cValdis.Kletnieks@vt.edu\u003e\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "23b5c8fa01b723c70a20d6e4ef4ff54c7656d6e1",
      "tree": "d03faad5e19848b35a019793b9a1cbc0bb68a708",
      "parents": [
        "4305ce7894dd38b0633bfc8978437320119223bd"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Sep 07 10:38:22 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 26 09:42:23 2011 -0700"
      },
      "message": "rcu: Decrease memory-barrier usage based on semi-formal proof\n\n(Note: this was reverted, and is now being re-applied in pieces, with\nthis being the fifth and final piece.  See below for the reason that\nit is now felt to be safe to re-apply this.)\n\nCommit d09b62d fixed grace-period synchronization, but left some smp_mb()\ninvocations in rcu_process_callbacks() that are no longer needed, but\nsheer paranoia prevented them from being removed.  This commit removes\nthem and provides a proof of correctness in their absence.  It also adds\na memory barrier to rcu_report_qs_rsp() immediately before the update to\nrsp-\u003ecompleted in order to handle the theoretical possibility that the\ncompiler or CPU might move massive quantities of code into a lock-based\ncritical section.  This also proves that the sheer paranoia was not\nentirely unjustified, at least from a theoretical point of view.\n\nIn addition, the old dyntick-idle synchronization depended on the fact\nthat grace periods were many milliseconds in duration, so that it could\nbe assumed that no dyntick-idle CPU could reorder a memory reference\nacross an entire grace period.  Unfortunately for this design, the\naddition of expedited grace periods breaks this assumption, which has\nthe unfortunate side-effect of requiring atomic operations in the\nfunctions that track dyntick-idle state for RCU.  (There is some hope\nthat the algorithms used in user-level RCU might be applied here, but\nsome work is required to handle the NMIs that user-space applications\ncan happily ignore.  For the short term, better safe than sorry.)\n\nThis proof assumes that neither compiler nor CPU will allow a lock\nacquisition and release to be reordered, as doing so can result in\ndeadlock.  The proof is as follows:\n\n1.\tA given CPU declares a quiescent state under the protection of\n\tits leaf rcu_node\u0027s lock.\n\n2.\tIf there is more than one level of rcu_node hierarchy, the\n\tlast CPU to declare a quiescent state will also acquire the\n\t-\u003elock of the next rcu_node up in the hierarchy,  but only\n\tafter releasing the lower level\u0027s lock.  The acquisition of this\n\tlock clearly cannot occur prior to the acquisition of the leaf\n\tnode\u0027s lock.\n\n3.\tStep 2 repeats until we reach the root rcu_node structure.\n\tPlease note again that only one lock is held at a time through\n\tthis process.  The acquisition of the root rcu_node\u0027s -\u003elock\n\tmust occur after the release of that of the leaf rcu_node.\n\n4.\tAt this point, we set the -\u003ecompleted field in the rcu_state\n\tstructure in rcu_report_qs_rsp().  However, if the rcu_node\n\thierarchy contains only one rcu_node, then in theory the code\n\tpreceding the quiescent state could leak into the critical\n\tsection.  We therefore precede the update of -\u003ecompleted with a\n\tmemory barrier.  All CPUs will therefore agree that any updates\n\tpreceding any report of a quiescent state will have happened\n\tbefore the update of -\u003ecompleted.\n\n5.\tRegardless of whether a new grace period is needed, rcu_start_gp()\n\twill propagate the new value of -\u003ecompleted to all of the leaf\n\trcu_node structures, under the protection of each rcu_node\u0027s -\u003elock.\n\tIf a new grace period is needed immediately, this propagation\n\twill occur in the same critical section that -\u003ecompleted was\n\tset in, but courtesy of the memory barrier in #4 above, is still\n\tseen to follow any pre-quiescent-state activity.\n\n6.\tWhen a given CPU invokes __rcu_process_gp_end(), it becomes\n\taware of the end of the old grace period and therefore makes\n\tany RCU callbacks that were waiting on that grace period eligible\n\tfor invocation.\n\n\tIf this CPU is the same one that detected the end of the grace\n\tperiod, and if there is but a single rcu_node in the hierarchy,\n\twe will still be in the single critical section.  In this case,\n\tthe memory barrier in step #4 guarantees that all callbacks will\n\tbe seen to execute after each CPU\u0027s quiescent state.\n\n\tOn the other hand, if this is a different CPU, it will acquire\n\tthe leaf rcu_node\u0027s -\u003elock, and will again be serialized after\n\teach CPU\u0027s quiescent state for the old grace period.\n\nOn the strength of this proof, this commit therefore removes the memory\nbarriers from rcu_process_callbacks() and adds one to rcu_report_qs_rsp().\nThe effect is to reduce the number of memory barriers by one and to\nreduce the frequency of execution from about once per scheduling tick\nper CPU to once per grace period.\n\nThis was reverted do to hangs found during testing by Yinghai Lu and\nIngo Molnar.  Frederic Weisbecker supplied Yinghai with tracing that\nlocated the underlying problem, and Frederic also provided the fix.\n\nThe underlying problem was that the HARDIRQ_ENTER() macro from\nlib/locking-selftest.c invoked irq_enter(), which in turn invokes\nrcu_irq_enter(), but HARDIRQ_EXIT() invoked __irq_exit(), which\ndoes not invoke rcu_irq_exit().  This situation resulted in calls\nto rcu_irq_enter() that were not balanced by the required calls to\nrcu_irq_exit().  Therefore, after these locking selftests completed,\nRCU\u0027s dyntick-idle nesting count was a large number (for example,\n72), which caused RCU to to conclude that the affected CPU was not in\ndyntick-idle mode when in fact it was.\n\nRCU would therefore incorrectly wait for this dyntick-idle CPU, resulting\nin hangs.\n\nIn contrast, with Frederic\u0027s patch, which replaces the irq_enter()\nin HARDIRQ_ENTER() with an __irq_enter(), these tests don\u0027t ever call\neither rcu_irq_enter() or rcu_irq_exit(), which works because the CPU\nrunning the test is already marked as not being in dyntick-idle mode.\nThis means that the rcu_irq_enter() and rcu_irq_exit() calls and RCU\nthen has no problem working out which CPUs are in dyntick-idle mode and\nwhich are not.\n\nThe reason that the imbalance was not noticed before the barrier patch\nwas applied is that the old implementation of rcu_enter_nohz() ignored\nthe nesting depth.  This could still result in delays, but much shorter\nones.  Whenever there was a delay, RCU would IPI the CPU with the\nunbalanced nesting level, which would eventually result in rcu_enter_nohz()\nbeing called, which in turn would force RCU to see that the CPU was in\ndyntick-idle mode.\n\nThe reason that very few people noticed the problem is that the mismatched\nirq_enter() vs. __irq_exit() occured only when the kernel was built with\nCONFIG_DEBUG_LOCKING_API_SELFTESTS.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "80d02085d99039b3b7f3a73c8896226b0cb1ba07",
      "tree": "c310902423ecb00effadcb59c60cbf118d4037cb",
      "parents": [
        "11c476f31a0fabc6e604da5b09a6590b57c3fb20"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 12 01:08:07 2011 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu May 19 23:25:29 2011 +0200"
      },
      "message": "Revert \"rcu: Decrease memory-barrier usage based on semi-formal proof\"\n\nThis reverts commit e59fb3120becfb36b22ddb8bd27d065d3cdca499.\n\nThis reversion was due to (extreme) boot-time slowdowns on SPARC seen by\nYinghai Lu and on x86 by Ingo\n.\nThis is a non-trivial reversion due to intervening commits.\n\nConflicts:\n\n\tDocumentation/RCU/trace.txt\n\tkernel/rcutree.c\n\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "1217ed1ba5c67393293dfb0f03c353b118dadeb4",
      "tree": "a765356c8418e134de85fd05d9fe6eda41de859c",
      "parents": [
        "29ce831000081dd757d3116bf774aafffc4b6b20"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Wed May 04 21:43:49 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat May 07 22:50:45 2011 -0700"
      },
      "message": "rcu: permit rcu_read_unlock() to be called while holding runqueue locks\n\nAvoid calling into the scheduler while holding core RCU locks.  This\nallows rcu_read_unlock() to be called while holding the runqueue locks,\nbut only as long as there was no chance of the RCU read-side critical\nsection having been preempted.  (Otherwise, if RCU priority boosting\nis enabled, rcu_read_unlock() might call into the scheduler in order to\nunboost itself, which might allows self-deadlock on the runqueue locks\nwithin the scheduler.)\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "6cc68793e380bb51f447d8d02af873b7bc01f222",
      "tree": "f2b66ace23acc0a31a08f136ad25659d6b51c4b1",
      "parents": [
        "13491a0ee1ef862b6c842132b6eb9c5e721af5ad"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Mar 02 13:15:15 2011 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 05 23:16:59 2011 -0700"
      },
      "message": "rcu: fix spelling\n\nThe \"preemptible\" spelling is preferable.  May as well fix it.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "15ba0ba860871cf74b48b1bb47c26c91a66126f3",
      "tree": "2043eeca7d6df62fc0ae918b61abada073f81415",
      "parents": [
        "a9f4793d8900dc5dc09b3951bdcd4731290e06fe"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Wed Apr 06 16:01:16 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 05 23:16:56 2011 -0700"
      },
      "message": "rcu: add grace-period age and more kthread state to tracing\n\nThis commit adds the age in jiffies of the current grace period along\nwith the duration in jiffies of the longest grace period since boot\nto the rcu/rcugp debugfs file.  It also adds an additional \"O\" state\nto kthread tracing to differentiate between the kthread waiting due to\nhaving nothing to do on the one hand and waiting due to being on the\nwrong CPU on the other hand.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "d71df90eadfc35aa549ff9a850842673febca71f",
      "tree": "dd275a3f4848784bc6625574341c11befc1b3823",
      "parents": [
        "0ac3d136b2e3cdf1161178223bc5da14a06241d0"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue Mar 29 17:48:28 2011 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 05 23:16:56 2011 -0700"
      },
      "message": "rcu: add tracing for RCU\u0027s kthread run states.\n\nAdd tracing to help debugging situations when RCU\u0027s kthreads are not\nrunning but are supposed to be.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "0ea1f2ebeb217d38770aebf91c4ecaa8e01b3305",
      "tree": "ef558d2eb804ca033a5166d24f5b4be7cf87727f",
      "parents": [
        "67b98dba474f293c389fc2b7254dcf7c0492e3bd"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Tue Feb 22 13:42:43 2011 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 05 23:16:55 2011 -0700"
      },
      "message": "rcu: Add boosting to TREE_PREEMPT_RCU tracing\n\nIncludes total number of tasks boosted, number boosted on behalf of each\nof normal and expedited grace periods, and statistics on attempts to\ninitiate boosting that failed for various reasons.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "27f4d28057adf98750cf863c40baefb12f5b6d21",
      "tree": "a66584d2cb68cebda327313f78b8f4eb602ed4ef",
      "parents": [
        "a26ac2455ffcf3be5c6ef92bc6df7182700f2114"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon Feb 07 12:47:15 2011 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 05 23:16:55 2011 -0700"
      },
      "message": "rcu: priority boosting for TREE_PREEMPT_RCU\n\nAdd priority boosting for TREE_PREEMPT_RCU, similar to that for\nTINY_PREEMPT_RCU.  This is enabled by the default-off RCU_BOOST\nkernel parameter.  The priority to which to boost preempted\nRCU readers is controlled by the RCU_BOOST_PRIO kernel parameter\n(defaulting to real-time priority 1) and the time to wait before\nboosting the readers who are blocking a given grace period is\ncontrolled by the RCU_BOOST_DELAY kernel parameter (defaulting to\n500 milliseconds).\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "a26ac2455ffcf3be5c6ef92bc6df7182700f2114",
      "tree": "601697c7c3fd152a1b3f29f43d3a028fc8fefd5f",
      "parents": [
        "12f5f524cafef3ab689929b118f2dfb8bf2be321"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Wed Jan 12 14:10:23 2011 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 05 23:16:54 2011 -0700"
      },
      "message": "rcu: move TREE_RCU from softirq to kthread\n\nIf RCU priority boosting is to be meaningful, callback invocation must\nbe boosted in addition to preempted RCU readers.  Otherwise, in presence\nof CPU real-time threads, the grace period ends, but the callbacks don\u0027t\nget invoked.  If the callbacks don\u0027t get invoked, the associated memory\ndoesn\u0027t get freed, so the system is still subject to OOM.\n\nBut it is not reasonable to priority-boost RCU_SOFTIRQ, so this commit\nmoves the callback invocations to a kthread, which can be boosted easily.\n\nAlso add comments and properly synchronized all accesses to\nrcu_cpu_kthread_task, as suggested by Lai Jiangshan.\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "12f5f524cafef3ab689929b118f2dfb8bf2be321",
      "tree": "639473556b6edf9b79e0a18d5ba58f80eea76519",
      "parents": [
        "e59fb3120becfb36b22ddb8bd27d065d3cdca499"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paul.mckenney@linaro.org",
        "time": "Mon Nov 29 21:56:39 2010 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 05 23:16:54 2011 -0700"
      },
      "message": "rcu: merge TREE_PREEPT_RCU blocked_tasks[] lists\n\nCombine the current TREE_PREEMPT_RCU -\u003eblocked_tasks[] lists in the\nrcu_node structure into a single -\u003eblkd_tasks list with -\u003egp_tasks\nand -\u003eexp_tasks tail pointers.  This is in preparation for RCU priority\nboosting, which will add a third dimension to the combinatorial explosion\nin the -\u003eblocked_tasks[] case, but simply a third pointer in the new\n-\u003eblkd_tasks case.\n\nAlso update documentation to reflect blocked_tasks[] merge\n\nSigned-off-by: Paul E. McKenney \u003cpaul.mckenney@linaro.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "e59fb3120becfb36b22ddb8bd27d065d3cdca499",
      "tree": "37eaadfe112b64caae943fc7469274bc96553d92",
      "parents": [
        "a00e0d714fbded07a7a2254391ce9ed5a5cb9d82"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Sep 07 10:38:22 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 05 23:16:54 2011 -0700"
      },
      "message": "rcu: Decrease memory-barrier usage based on semi-formal proof\n\nCommit d09b62d fixed grace-period synchronization, but left some smp_mb()\ninvocations in rcu_process_callbacks() that are no longer needed, but\nsheer paranoia prevented them from being removed.  This commit removes\nthem and provides a proof of correctness in their absence.  It also adds\na memory barrier to rcu_report_qs_rsp() immediately before the update to\nrsp-\u003ecompleted in order to handle the theoretical possibility that the\ncompiler or CPU might move massive quantities of code into a lock-based\ncritical section.  This also proves that the sheer paranoia was not\nentirely unjustified, at least from a theoretical point of view.\n\nIn addition, the old dyntick-idle synchronization depended on the fact\nthat grace periods were many milliseconds in duration, so that it could\nbe assumed that no dyntick-idle CPU could reorder a memory reference\nacross an entire grace period.  Unfortunately for this design, the\naddition of expedited grace periods breaks this assumption, which has\nthe unfortunate side-effect of requiring atomic operations in the\nfunctions that track dyntick-idle state for RCU.  (There is some hope\nthat the algorithms used in user-level RCU might be applied here, but\nsome work is required to handle the NMIs that user-space applications\ncan happily ignore.  For the short term, better safe than sorry.)\n\nThis proof assumes that neither compiler nor CPU will allow a lock\nacquisition and release to be reordered, as doing so can result in\ndeadlock.  The proof is as follows:\n\n1.\tA given CPU declares a quiescent state under the protection of\n\tits leaf rcu_node\u0027s lock.\n\n2.\tIf there is more than one level of rcu_node hierarchy, the\n\tlast CPU to declare a quiescent state will also acquire the\n\t-\u003elock of the next rcu_node up in the hierarchy,  but only\n\tafter releasing the lower level\u0027s lock.  The acquisition of this\n\tlock clearly cannot occur prior to the acquisition of the leaf\n\tnode\u0027s lock.\n\n3.\tStep 2 repeats until we reach the root rcu_node structure.\n\tPlease note again that only one lock is held at a time through\n\tthis process.  The acquisition of the root rcu_node\u0027s -\u003elock\n\tmust occur after the release of that of the leaf rcu_node.\n\n4.\tAt this point, we set the -\u003ecompleted field in the rcu_state\n\tstructure in rcu_report_qs_rsp().  However, if the rcu_node\n\thierarchy contains only one rcu_node, then in theory the code\n\tpreceding the quiescent state could leak into the critical\n\tsection.  We therefore precede the update of -\u003ecompleted with a\n\tmemory barrier.  All CPUs will therefore agree that any updates\n\tpreceding any report of a quiescent state will have happened\n\tbefore the update of -\u003ecompleted.\n\n5.\tRegardless of whether a new grace period is needed, rcu_start_gp()\n\twill propagate the new value of -\u003ecompleted to all of the leaf\n\trcu_node structures, under the protection of each rcu_node\u0027s -\u003elock.\n\tIf a new grace period is needed immediately, this propagation\n\twill occur in the same critical section that -\u003ecompleted was\n\tset in, but courtesy of the memory barrier in #4 above, is still\n\tseen to follow any pre-quiescent-state activity.\n\n6.\tWhen a given CPU invokes __rcu_process_gp_end(), it becomes\n\taware of the end of the old grace period and therefore makes\n\tany RCU callbacks that were waiting on that grace period eligible\n\tfor invocation.\n\n\tIf this CPU is the same one that detected the end of the grace\n\tperiod, and if there is but a single rcu_node in the hierarchy,\n\twe will still be in the single critical section.  In this case,\n\tthe memory barrier in step #4 guarantees that all callbacks will\n\tbe seen to execute after each CPU\u0027s quiescent state.\n\n\tOn the other hand, if this is a different CPU, it will acquire\n\tthe leaf rcu_node\u0027s -\u003elock, and will again be serialized after\n\teach CPU\u0027s quiescent state for the old grace period.\n\nOn the strength of this proof, this commit therefore removes the memory\nbarriers from rcu_process_callbacks() and adds one to rcu_report_qs_rsp().\nThe effect is to reduce the number of memory barriers by one and to\nreduce the frequency of execution from about once per scheduling tick\nper CPU to once per grace period.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "a00e0d714fbded07a7a2254391ce9ed5a5cb9d82",
      "tree": "7c213dbf1e2561655d07749b6d689027460fb8cc",
      "parents": [
        "0ee5623f9a6e52df90a78bd21179f8ab370e102e"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Feb 08 17:14:39 2011 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu May 05 23:16:54 2011 -0700"
      },
      "message": "rcu: Remove conditional compilation for RCU CPU stall warnings\n\nThe RCU CPU stall warnings can now be controlled using the\nrcu_cpu_stall_suppress boot-time parameter or via the same parameter\nfrom sysfs.  There is therefore no longer any reason to have\nkernel config parameters for this feature.  This commit therefore\nremoves the RCU_CPU_STALL_DETECTOR and RCU_CPU_STALL_DETECTOR_RUNNABLE\nkernel config parameters.  The RCU_CPU_STALL_TIMEOUT parameter remains\nto allow the timeout to be tuned and the RCU_CPU_STALL_VERBOSE parameter\nremains to allow task-stall information to be suppressed if desired.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "0209f6490b030f35349a2bb71294f3fd75b0f36d",
      "tree": "159e233c6fcaf63fbb1a18f5db54af38a8336ee3",
      "parents": [
        "121dfc4b3eba9e2f3c42d35205a3510cc65b9931"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Dec 14 16:07:52 2010 -0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Dec 17 12:34:20 2010 -0800"
      },
      "message": "rcu: limit rcu_node leaf-level fanout\n\nSome recent benchmarks have indicated possible lock contention on the\nleaf-level rcu_node locks.  This commit therefore limits the number of\nCPUs per leaf-level rcu_node structure to 16, in other words, there\ncan be at most 16 rcu_data structures fanning into a given rcu_node\nstructure.  Prior to this, the limit was 32 on 32-bit systems and 64 on\n64-bit systems.\n\nNote that the fanout of non-leaf rcu_node structures is unchanged.  The\norganization of accesses to the rcu_node tree is such that references\nto non-leaf rcu_node structures are much less frequent than to the\nleaf structures.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "29494be71afe2a16ad04e344306a620d7cc22d06",
      "tree": "d16a2acd1566be326483d5217d39b78d2ef798c5",
      "parents": [
        "7b27d5475f86186914e54e4a6bb994e9a985337b"
      ],
      "author": {
        "name": "Lai Jiangshan",
        "email": "laijs@cn.fujitsu.com",
        "time": "Wed Oct 20 14:13:06 2010 +0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Nov 29 22:01:58 2010 -0800"
      },
      "message": "rcu,cleanup: simplify the code when cpu is dying\n\nWhen we handle the CPU_DYING notifier, the whole system is stopped except\nfor the current CPU.  We therefore need no synchronization with the other\nCPUs.  This allows us to move any orphaned RCU callbacks directly to the\nlist of any online CPU without needing to run them through the global\norphan lists.  These global orphan lists can therefore be dispensed with.\nThis commit makes thes changes, though currently victimizes CPU 0 @@@.\n\nSigned-off-by: Lai Jiangshan \u003claijs@cn.fujitsu.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "269dcc1c2ec25864308ee03a3fa26ea819d9f5d0",
      "tree": "1c81ee6a9151ab1580628f6e9f85c469ceccb5c0",
      "parents": [
        "0ddea0ead2ced99eaaaddff2beb755381e5c89f8"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Sep 07 14:23:09 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Sep 23 09:16:53 2010 -0700"
      },
      "message": "rcu: Add tracing data to support queueing models\n\nThe current tracing data is not sufficient to deduce the average time\nthat a callback spends waiting for a grace period to end.  Add three\nper-CPU counters recording the number of callbacks invoked (ci), the\nnumber of callbacks orphaned (co), and the number of callbacks adopted\n(ca).  Given the existing callback queue length (ql), the average wait\ntime in absence of CPU hotplug operations is ql/ci.  The units of wait\ntime will be in terms of the duration over which ci was measured.\n\nIn the presence of CPU hotplug operations, there is room for argument,\nbut ql/(ci-co+ca) won\u0027t steer you too far wrong.\n\nAlso fixes a typo called out by Lucas De Marchi \u003clucas.de.marchi@gmail.com\u003e.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "a3dc3fb161f9b4066c0fce22db72638af8baf83b",
      "tree": "e41a30edd7e4965807b199da7637a6d6e44d4ed1",
      "parents": [
        "53d84e004d5e8c018be395c4330dc72fd60bd13e"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Aug 13 16:16:25 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Aug 20 09:00:13 2010 -0700"
      },
      "message": "rcu: repair code-duplication FIXMEs\n\nCombine the duplicate definitions of ULONG_CMP_GE(), ULONG_CMP_LT(),\nand rcu_preempt_depth() into include/linux/rcupdate.h.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "53d84e004d5e8c018be395c4330dc72fd60bd13e",
      "tree": "6d5b265442ac42c7cc73147b0de0d029644e312b",
      "parents": [
        "8cdd32a918350430483751feaae1c19cef816f69"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Aug 10 14:28:53 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Aug 20 09:00:12 2010 -0700"
      },
      "message": "rcu: permit suppressing current grace period\u0027s CPU stall warnings\n\nWhen using a kernel debugger, a long sojourn in the debugger can get\nyou lots of RCU CPU stall warnings once you resume.  This might not be\nhelpful, especially if you are using the system console.  This patch\ntherefore allows RCU CPU stall warnings to be suppressed, but only for\nthe duration of the current set of grace periods.\n\nThis differs from Jason\u0027s original patch in that it adds support for\ntiny RCU and preemptible RCU, and uses a slightly different method for\nsuppressing the RCU CPU stall warning messages.\n\nSigned-off-by: Jason Wessel \u003cjason.wessel@windriver.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nTested-by: Jason Wessel \u003cjason.wessel@windriver.com\u003e\n"
    },
    {
      "commit": "910b1b7e19a292ff685001caf1bf1a9775b771a1",
      "tree": "7ec42bf018ab62c3c2180fbe168cd6130556cb80",
      "parents": [
        "687d7a960aea46e016182c7ce346d62c4dbd0366"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Jul 21 08:05:56 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Aug 19 17:18:04 2010 -0700"
      },
      "message": "rcu: Allow RCU CPU stall warnings to be off at boot, but manually enablable\n\nCurrently, if RCU CPU stall warnings are enabled, they are enabled\nimmediately upon boot.  They can be manually disabled via /sys (and\nalso re-enabled via /sys), and are automatically disabled upon panic.\nHowever, some users need RCU CPU stalls to be disabled at boot time,\nbut to be enabled without rebuilding/rebooting.  For example, someone\nrunning a real-time application in production might not want the\nadditional latency of RCU CPU stall detection in normal operation, but\nmight need to enable it at any point for fault isolation purposes.\n\nThis commit therefore provides a new CONFIG_RCU_CPU_STALL_DETECTOR_RUNNABLE\nkernel configuration parameter that maintains the current behavior\n(enable at boot) by default, but allows a kernel to be configured\nwith RCU CPU stall detection built into the kernel, but disabled at\nboot time.\n\nRequested-by: Clark Williams \u003cwilliams@redhat.com\u003e\nRequested-by: John Kacur \u003cjkacur@redhat.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "b163760e37047781b37c412cde54d146ac4b651f",
      "tree": "5b447a210c81b78e20393472f4b53623c8fed28b",
      "parents": [
        "4221a9918e38b7494cee341dda7b7b4bb8c04bde"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Jun 02 16:21:38 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Aug 19 17:18:02 2010 -0700"
      },
      "message": "rcu: make CPU stall warning timeout configurable\n\nAlso set the default to 60 seconds, up from the previous hard-coded timeout\nof 10 seconds.  This allows people who care to set short timeouts, while\navoiding people with unusual configurations (make randconfig!!!) from being\nbothered with spurious CPU stall warnings.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "394f99a9007d4274f7076bb8553ab0ff9707688b",
      "tree": "7d379f91321cec58b87fd5f5089947872689d591",
      "parents": [
        "e546f485e1d7520ca0200502cdcc11b503f4805c"
      ],
      "author": {
        "name": "Lai Jiangshan",
        "email": "laijs@cn.fujitsu.com",
        "time": "Mon Jun 28 16:25:04 2010 +0800"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Aug 19 17:18:01 2010 -0700"
      },
      "message": "rcu: simplify the usage of percpu data\n\n\u0026percpu_data is compatible with allocated percpu data.\n\nAnd we use it and remove the \"-\u003erda[NR_CPUS]\" array, saving significant\nstorage on systems with large numbers of CPUs.  This does add an additional\nlevel of indirection and thus an additional cache line referenced, but\nbecause -\u003erda is not used on the read side, this is OK.\n\nSigned-off-by: Lai Jiangshan \u003claijs@cn.fujitsu.com\u003e\nReviewed-by: Tejun Heo \u003ctj@kernel.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nReviewed-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\n"
    },
    {
      "commit": "d21670acab9fcb4bc74a40b68a6941059234c55c",
      "tree": "6a4c054bc4dbadf0524b4e221889a8da558dbdaf",
      "parents": [
        "4a90a0681cf6cd21cd444184302aa045156486b3"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Apr 14 17:39:26 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon May 10 11:08:35 2010 -0700"
      },
      "message": "rcu: reduce the number of spurious RCU_SOFTIRQ invocations\n\nLai Jiangshan noted that up to 10% of the RCU_SOFTIRQ are spurious, and\ntraced this down to the fact that the current grace-period machinery\nwill uselessly raise RCU_SOFTIRQ when a given CPU needs to go through\na quiescent state, but has not yet done so.  In this situation, there\nmight well be nothing that RCU_SOFTIRQ can do, and the overhead can be\nworth worrying about in the ksoftirqd case.  This patch therefore avoids\nraising RCU_SOFTIRQ in this situation.\n\nChanges since v1 (http://lkml.org/lkml/2010/3/30/122 from Lai Jiangshan):\n\no\tOmit the rcu_qs_pending() prechecks, as they aren\u0027t that\n\tmuch less expensive than the quiescent-state checks.\n\no\tMerge with the set_need_resched() patch that reduces IPIs.\n\no\tAdd the new n_rp_report_qs field to the rcu_pending tracing output.\n\no\tUpdate the tracing documentation accordingly.\n\nSigned-off-by: Lai Jiangshan \u003claijs@cn.fujitsu.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "4300aa642cc9ecb35f2e0683dd294fb790ef028c",
      "tree": "b70d676b02c6311a638fdaa6f3df8773b39fade1",
      "parents": [
        "26845c2860cebebe6ce2d9d01ae3cb3db84b7e29"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Apr 13 16:18:22 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon May 10 11:08:34 2010 -0700"
      },
      "message": "rcu: improve RCU CPU stall-warning messages\n\nThe existing RCU CPU stall-warning messages can be confusing, especially\nin the case where one CPU detects a single other stalled CPU.  In addition,\nthe console messages did not say which flavor of RCU detected the stall,\nwhich can make it difficult to work out exactly what is causing the stall.\nThis commit improves these messages.\n\nRequested-by: Dhaval Giani \u003cdhaval.giani@gmail.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "007b09243b099811124f69d492adeebe9e439f96",
      "tree": "fc80fcd1f6c5dfcb37144f4d17507d22cbbc0c11",
      "parents": [
        "3f379b03fbfddd20536389a85c6456f8233d1f8d"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Mar 05 15:03:26 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Mar 11 13:38:01 2010 +0100"
      },
      "message": "rcu: Increase RCU CPU stall timeouts if PROVE_RCU\n\nCONFIG_PROVE_RCU imposes additional overhead on the kernel, so\nincrease the RCU CPU stall timeouts in an attempt to allow for\nthis effect.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c1267830207-9474-2-git-send-email-paulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "a47cd880b50e14b0b6f5e9d426ae9a2676c9c474",
      "tree": "c134dcec52450ec92ea853f4aeeef8e3967a36cb",
      "parents": [
        "f5f654096487c6d526c47bb66308f9de81f091cf"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Feb 26 16:38:56 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sat Feb 27 09:53:52 2010 +0100"
      },
      "message": "rcu: Fix accelerated grace periods for last non-dynticked CPU\n\nIt is invalid to invoke __rcu_process_callbacks() with irqs\ndisabled, so do it indirectly via raise_softirq().  This\nrequires a state-machine implementation to cycle through the\ngrace-period machinery the required number of times.\n\nLocated-by: Ingo Molnar \u003cmingo@elte.hu\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c1267231138-27856-1-git-send-email-paulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "1ed509a225008c9e8c0644fbd22168e09a7383a0",
      "tree": "db65a58258bb968e7bc922dab14f4f0714a7667e",
      "parents": [
        "6155fec92e85f07d99e9746234496215443ffb0d"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Feb 22 17:05:05 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Feb 25 10:35:02 2010 +0100"
      },
      "message": "rcu: Add RCU_CPU_STALL_VERBOSE to dump detailed per-task information\n\nWhen RCU detects a grace-period stall, it currently just prints\nout the PID of any tasks doing the stalling.  This patch adds\nRCU_CPU_STALL_VERBOSE, which enables the more-verbose reporting\nfrom sched_show_task().\n\nSuggested-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c1266887105-1528-21-git-send-email-paulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "1304afb225288a2e250d6a7495462c28e5509cbb",
      "tree": "1ba76e304f718f7ce89532e1c4d276b4af439c07",
      "parents": [
        "20133cfce7d0bbdcc0c398301030c091f5675c88"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Feb 22 17:05:02 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Feb 25 10:34:58 2010 +0100"
      },
      "message": "rcu: Convert to raw_spinlocks\n\nThe spinlocks in rcutree need to be real spinlocks in\npreempt-rt. Convert them to raw_spinlocks.\n\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c1266887105-1528-18-git-send-email-paulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "20133cfce7d0bbdcc0c398301030c091f5675c88",
      "tree": "337f242bfc89f5880cf86234fa6b574f52a2f0a5",
      "parents": [
        "1bd22e374b20c2f0ba1d2723c1f585acab2251c5"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Feb 22 17:05:01 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Feb 25 10:34:57 2010 +0100"
      },
      "message": "rcu: Stop overflowing signed integers\n\nThe C standard does not specify the result of an operation that\noverflows a signed integer, so such operations need to be\navoided.  This patch changes the type of several fields from\n\"long\" to \"unsigned long\" and adjusts operations as needed.\nULONG_CMP_GE() and ULONG_CMP_LT() macros are introduced to do\nthe modular comparisons that are appropriate given that overflow\nis an expected event.\n\nAcked-by: Mathieu Desnoyers \u003cmathieu.desnoyers@efficios.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c1266887105-1528-17-git-send-email-paulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "017c426138122c8e9b9f5057fbd0567c37b35247",
      "tree": "648d35f773bc08e83d06f0c02a68cae02c46a4cd",
      "parents": [
        "4c54005ca438a8b46dd542b497d4f0dc2ca375e8"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Jan 14 16:10:58 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sat Jan 16 10:25:22 2010 +0100"
      },
      "message": "rcu: Fix sparse warnings\n\nRename local variable \"i\" in rcu_init() to avoid conflict with\nRCU_INIT_FLAVOR(), restrict the scope of RCU_TREE_NONCORE, and\nmake __synchronize_srcu() static.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c12635142581560-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "46a1e34eda805501a8b32f26394faa435149f6d1",
      "tree": "56359434e348fce6ffc8701fb4948dee1cb4c91f",
      "parents": [
        "45f014c52eef022873b19d6a20eb0ec9668f2b09"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jan 04 15:09:09 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Wed Jan 13 09:06:05 2010 +0100"
      },
      "message": "rcu: Make force_quiescent_state() start grace period if needed\n\nGrace periods cannot be started while force_quiescent_state() is\nactive.  This is OK in that the affected CPUs will try again\nlater, but it does induce needless grace-period delays.  This\npatch causes rcu_start_gp() to record a failed attempt to start\na grace period. When force_quiescent_state() prepares to return,\nit then starts the grace period if there was such a failed\nattempt.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c12626465501854-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "ee47eb9f4da6f44af965d6d049e77ee8c8a4b822",
      "tree": "bc500b12150bd47afd34b24fd1db90939f5fec3b",
      "parents": [
        "0f10dc826646134dce3e5751512b87d30f3903e4"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jan 04 15:09:07 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Wed Jan 13 09:06:04 2010 +0100"
      },
      "message": "rcu: Remove leg of force_quiescent_state() switch statement\n\nThe comparisons of rsp-\u003egpnum nad rsp-\u003ecompleted in\nrcu_process_dyntick() and force_quiescent_state() can be\nreplaced by the much more clear rcu_gp_in_progress() predicate\nfunction.  After doing this, it becomes clear that the\nRCU_SAVE_COMPLETED leg of the force_quiescent_state() function\u0027s\nswitch statement is almost completely a no-op.  A small change\nto the RCU_SAVE_DYNTICK leg renders it a complete no-op, after\nwhich it can be removed.  Doing so also eliminates the forcenow\nlocal variable from force_quiescent_state().\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c12626465501781-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "39c0bbfc07c6e28db7346d0e11106f2d045d3035",
      "tree": "82f0fdacb1eea0334e76e0adb8b9d5beec66f2a7",
      "parents": [
        "f3a8b5c6aa543bd87764418d63632eb65b80e2f6"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jan 04 15:09:04 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Wed Jan 13 09:06:03 2010 +0100"
      },
      "message": "rcu: Eliminate local variable lastcomp from force_quiescent_state()\n\nBecause rsp-\u003efqs_active is set to 1 across\nforce_quiescent_state()\u0027s switch statement, rcu_start_gp() will\nrefrain from starting a new grace period during this time.\nTherefore, rsp-\u003egpnum is constant, and can be propagated to all\nuses of lastcomp, eliminating this local variable.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c12626465502985-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "07079d5357a4d53c2b13126c4a38fb40e6e04966",
      "tree": "1a97552a220a9bbdfceb1cda01c1ee5b92ce75bd",
      "parents": [
        "559569acf94f538b56bd6eead80b439d6a78cdff"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jan 04 15:09:02 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Wed Jan 13 09:06:02 2010 +0100"
      },
      "message": "rcu: Prohibit starting new grace periods while forcing quiescent states\n\nReduce the number and variety of race conditions by prohibiting\nthe start of a new grace period while force_quiescent_state() is\nactive. A new fqs_active flag in the rcu_state structure is used\nto trace whether or not force_quiescent_state() is active, and\nthis new flag is tested by rcu_start_gp().  If the CPU that\nclosed out the last grace period needs another grace period,\nthis new grace period may be delayed up to one scheduling-clock\ntick, but it will eventually get started.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c126264655052-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "d9a3da0699b24a589b27a61e1a5b5bd30d9db669",
      "tree": "f7440e396a6c818f3cef514ccc31ab55d88025ef",
      "parents": [
        "cf244dc01bf68e1ad338b82447f8686d24ea4435"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Dec 02 12:10:15 2009 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Dec 03 11:35:25 2009 +0100"
      },
      "message": "rcu: Add expedited grace-period support for preemptible RCU\n\nImplement an synchronize_rcu_expedited() for preemptible RCU\nthat actually is expedited.  This uses\nsynchronize_sched_expedited() to force all threads currently\nrunning in a preemptible-RCU read-side critical section onto the\nappropriate -\u003eblocked_tasks[] list, then takes a snapshot of all\nof these lists and waits for them to drain.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c1259784616158-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "cf244dc01bf68e1ad338b82447f8686d24ea4435",
      "tree": "dc2aebb60ef1eddf92d7e23b72ec2f6c08797684",
      "parents": [
        "d3f6bad3911736e44ba11f3f3f6ac4e8c837fdfc"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Dec 02 12:10:14 2009 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Dec 03 11:34:53 2009 +0100"
      },
      "message": "rcu: Enable fourth level of TREE_RCU hierarchy\n\nEnable a fourth level of rcu_node hierarchy for TREE_RCU and\nTREE_PREEMPT_RCU.  This is for stress-testing and experiemental\npurposes only, although in theory this would enable 16,777,216\nCPUs on 64-bit systems, though only 1,048,576 CPUs on 32-bit\nsystems. Normal experimental use of this fourth level will\nnormally set CONFIG_RCU_FANOUT\u003d2, requiring a 16-CPU system,\nthough the more adventurous (and more fortunate) experimenters\nmay wish to chose CONFIG_RCU_FANOUT\u003d3 for 81-CPU systems or even\nCONFIG_RCU_FANOUT\u003d4 for 256-CPU systems.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nAcked-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\nAcked-by: Lai Jiangshan \u003claijs@cn.fujitsu.com\u003e\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c12597846161257-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "d3f6bad3911736e44ba11f3f3f6ac4e8c837fdfc",
      "tree": "55b0c2e11ab3ec02e9065cf3d46ffd20386dfed2",
      "parents": [
        "6ebb237bece23275d1da149b61a342f0d4d06a08"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Dec 02 12:10:13 2009 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Dec 03 11:34:26 2009 +0100"
      },
      "message": "rcu: Rename \"quiet\" functions\n\nThe number of \"quiet\" functions has grown recently, and the\nnames are no longer very descriptive.  The point of all of these\nfunctions is to do some portion of the task of reporting a\nquiescent state, so rename them accordingly:\n\no\tcpu_quiet() becomes rcu_report_qs_rdp(), which reports a\n\tquiescent state to the per-CPU rcu_data structure.  If this\n\tturns out to be a new quiescent state for this grace period,\n\tthen rcu_report_qs_rnp() will be invoked to propagate the\n\tquiescent state up the rcu_node hierarchy.\n\no\tcpu_quiet_msk() becomes rcu_report_qs_rnp(), which reports\n\ta quiescent state for a given CPU (or possibly a set of CPUs)\n\tup the rcu_node hierarchy.\n\no\tcpu_quiet_msk_finish() becomes rcu_report_qs_rsp(), which\n\treports a full set of quiescent states to the global rcu_state\n\tstructure.\n\no\ttask_quiet() becomes rcu_report_unblock_qs_rnp(), which reports\n\ta quiescent state due to a task exiting an RCU read-side critical\n\tsection that had previously blocked in that same critical section.\n\tAs indicated by the new name, this type of quiescent state is\n\treported up the rcu_node hierarchy (using rcu_report_qs_rnp()\n\tto do so).\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nAcked-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\nAcked-by: Lai Jiangshan \u003claijs@cn.fujitsu.com\u003e\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c12597846163698-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "b668c9cf3e58739dac54a1d6f42f2b4bdd980b3e",
      "tree": "c0165d39532a2314f8187d765f3c8ddf88b72831",
      "parents": [
        "2f51f9884f6a36b0fe9636d5a1937e5cbd25723b"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Nov 22 08:53:48 2009 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sun Nov 22 18:58:15 2009 +0100"
      },
      "message": "rcu: Fix grace-period-stall bug on large systems with CPU hotplug\n\nWhen the last CPU of a given leaf rcu_node structure goes\noffline, all of the tasks queued on that leaf rcu_node structure\n(due to having blocked in their current RCU read-side critical\nsections) are requeued onto the root rcu_node structure.  This\nrequeuing is carried out by rcu_preempt_offline_tasks().\nHowever, it is possible that these queued tasks are the only\nthing preventing the leaf rcu_node structure from reporting a\nquiescent state up the rcu_node hierarchy.  Unfortunately, the\nold code would fail to do this reporting, resulting in a\ngrace-period stall given the following sequence of events:\n\n1.\tKernel built for more than 32 CPUs on 32-bit systems or for more\n\tthan 64 CPUs on 64-bit systems, so that there is more than one\n\trcu_node structure.  (Or CONFIG_RCU_FANOUT is artificially set\n\tto a number smaller than CONFIG_NR_CPUS.)\n\n2.\tThe kernel is built with CONFIG_TREE_PREEMPT_RCU.\n\n3.\tA task running on a CPU associated with a given leaf rcu_node\n\tstructure blocks while in an RCU read-side critical section\n\t-and- that CPU has not yet passed through a quiescent state\n\tfor the current RCU grace period.  This will cause the task\n\tto be queued on the leaf rcu_node\u0027s blocked_tasks[] array, in\n\tparticular, on the element of this array corresponding to the\n\tcurrent grace period.\n\n4.\tEach of the remaining CPUs corresponding to this same leaf rcu_node\n\tstructure pass through a quiescent state.  However, the task is\n\tstill in its RCU read-side critical section, so these quiescent\n\tstates cannot be reported further up the rcu_node hierarchy.\n\tNevertheless, all bits in the leaf rcu_node structure\u0027s -\u003eqsmask\n\tfield are now zero.\n\n5.\tEach of the remaining CPUs go offline.  (The events in step\n\t#4 and #5 can happen in any order as long as each CPU passes\n\tthrough a quiescent state before going offline.)\n\n6.\tWhen the last CPU goes offline, __rcu_offline_cpu() will invoke\n\trcu_preempt_offline_tasks(), which will move the task to the\n\troot rcu_node structure, but without reporting a quiescent state\n\tup the rcu_node hierarchy (and this failure to report a quiescent\n\tstate is the bug).\n\n\tBut because this leaf rcu_node structure\u0027s -\u003eqsmask field is\n\talready zero and its -\u003eblock_tasks[] entries are all empty,\n\tforce_quiescent_state() will skip this rcu_node structure.\n\n\tTherefore, grace periods are now hung.\n\nThis patch abstracts some code out of rcu_read_unlock_special(),\ncalling the result task_quiet() by analogy with cpu_quiet(), and\ninvokes task_quiet() from both rcu_read_lock_special() and\n__rcu_offline_cpu().  Invoking task_quiet() from\n__rcu_offline_cpu() reports the quiescent state up the rcu_node\nhierarchy, fixing the bug.  This ends up requiring a separate\nlock_class_key per level of the rcu_node hierarchy, which this\npatch also provides.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c12589088301770-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    }
  ],
  "next": "4bcfe055030d9e953945def3864f7e6997b27782"
}