)]}'
{
  "log": [
    {
      "commit": "b8ae30ee26d379db436b0b8c8c3ff1b52f69e5d1",
      "tree": "506aa0b4bdbf90f61e7e9261c7db90aa1452dcce",
      "parents": [
        "4d7b4ac22fbec1a03206c6cde353f2fd6942f828",
        "9c6f7e43b4e02c161b53e97ba913855246876c61"
      ],
      "author": {
        "name": "Linus Torvalds",
        "email": "torvalds@linux-foundation.org",
        "time": "Tue May 18 08:27:54 2010 -0700"
      },
      "committer": {
        "name": "Linus Torvalds",
        "email": "torvalds@linux-foundation.org",
        "time": "Tue May 18 08:27:54 2010 -0700"
      },
      "message": "Merge branch \u0027sched-core-for-linus\u0027 of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip\n\n* \u0027sched-core-for-linus\u0027 of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (49 commits)\n  stop_machine: Move local variable closer to the usage site in cpu_stop_cpu_callback()\n  sched, wait: Use wrapper functions\n  sched: Remove a stale comment\n  ondemand: Make the iowait-is-busy time a sysfs tunable\n  ondemand: Solve a big performance issue by counting IOWAIT time as busy\n  sched: Intoduce get_cpu_iowait_time_us()\n  sched: Eliminate the ts-\u003eidle_lastupdate field\n  sched: Fold updating of the last_update_time_info into update_ts_time_stats()\n  sched: Update the idle statistics in get_cpu_idle_time_us()\n  sched: Introduce a function to update the idle statistics\n  sched: Add a comment to get_cpu_idle_time_us()\n  cpu_stop: add dummy implementation for UP\n  sched: Remove rq argument to the tracepoints\n  rcu: need barrier() in UP synchronize_sched_expedited()\n  sched: correctly place paranioa memory barriers in synchronize_sched_expedited()\n  sched: kill paranoia check in synchronize_sched_expedited()\n  sched: replace migration_thread with cpu_stop\n  stop_machine: reimplement using cpu_stop\n  cpu_stop: implement stop_cpu[s]()\n  sched: Fix select_idle_sibling() logic in select_task_rq_fair()\n  ...\n"
    },
    {
      "commit": "bbad937983147c017c25406860287cb94da9af7c",
      "tree": "57311598c360b92b189c7ec337146e4bc779c73d",
      "parents": [
        "25502a6c13745f4650cc59322bd198194f55e796"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Apr 02 16:17:17 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon May 10 11:08:34 2010 -0700"
      },
      "message": "rcu: slim down rcutiny by removing rcu_scheduler_active and friends\n\nTINY_RCU does not need rcu_scheduler_active unless CONFIG_DEBUG_LOCK_ALLOC.\nSo conditionally compile rcu_scheduler_active in order to slim down\nrcutiny a bit more.  Also gets rid of an EXPORT_SYMBOL_GPL, which is\nresponsible for most of the slimming.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "25502a6c13745f4650cc59322bd198194f55e796",
      "tree": "d76cc659d3ea797c5da4630e219ac363d17c44a6",
      "parents": [
        "99652b54de1ee094236f7171485214071af4ef31"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Apr 01 17:37:01 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon May 10 11:08:33 2010 -0700"
      },
      "message": "rcu: refactor RCU\u0027s context-switch handling\n\nThe addition of preemptible RCU to treercu resulted in a bit of\nconfusion and inefficiency surrounding the handling of context switches\nfor RCU-sched and for RCU-preempt.  For RCU-sched, a context switch\nis a quiescent state, pure and simple, just like it always has been.\nFor RCU-preempt, a context switch is in no way a quiescent state, but\nspecial handling is required when a task blocks in an RCU read-side\ncritical section.\n\nHowever, the callout from the scheduler and the outer loop in ksoftirqd\nstill calls something named rcu_sched_qs(), whose name is no longer\naccurate.  Furthermore, when rcu_check_callbacks() notes an RCU-sched\nquiescent state, it ends up unnecessarily (though harmlessly, aside\nfrom the performance hit) enqueuing the current task if it happens to\nbe running in an RCU-preempt read-side critical section.  This not only\nincreases the maximum latency of scheduler_tick(), it also needlessly\nincreases the overhead of the next outermost rcu_read_unlock() invocation.\n\nThis patch addresses this situation by separating the notion of RCU\u0027s\ncontext-switch handling from that of RCU-sched\u0027s quiescent states.\nThe context-switch handling is covered by rcu_note_context_switch() in\ngeneral and by rcu_preempt_note_context_switch() for preemptible RCU.\nThis permits rcu_sched_qs() to handle quiescent states and only quiescent\nstates.  It also reduces the maximum latency of scheduler_tick(), though\nprobably by much less than a microsecond.  Finally, it means that tasks\nwithin preemptible-RCU read-side critical sections avoid incurring the\noverhead of queuing unless there really is a context switch.\n\nSuggested-by: Lai Jiangshan \u003claijs@cn.fujitsu.com\u003e\nAcked-by: Lai Jiangshan \u003claijs@cn.fujitsu.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: Ingo Molnar \u003cmingo@elte.hu\u003e\nCc: Peter Zijlstra \u003cpeterz@infradead.org\u003e\n"
    },
    {
      "commit": "da848c47bc6e873a54a445ea1960423a495b6b32",
      "tree": "4c0eaef1a5990585730f00caca0cfcba21fe9f9f",
      "parents": [
        "32c141a0a1dfa29e0a07d78bec0c0919fc4b9f88"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Tue Mar 30 15:46:01 2010 -0700"
      },
      "committer": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon May 10 11:08:32 2010 -0700"
      },
      "message": "rcu: shrink rcutiny by making synchronize_rcu_bh() be inline\n\nBecause synchronize_rcu_bh() is identical to synchronize_sched(),\nmake the former a static inline invoking the latter, saving the\noverhead of an EXPORT_SYMBOL_GPL() and the duplicate code.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\n"
    },
    {
      "commit": "969c79215a35b06e5e3efe69b9412f858df7856c",
      "tree": "4256378687c8bc2011ec35a3e28bc3b6473e912c",
      "parents": [
        "3fc1f1e27a5b807791d72e5d992aa33b668a6626"
      ],
      "author": {
        "name": "Tejun Heo",
        "email": "tj@kernel.org",
        "time": "Thu May 06 18:49:21 2010 +0200"
      },
      "committer": {
        "name": "Tejun Heo",
        "email": "tj@kernel.org",
        "time": "Thu May 06 18:49:21 2010 +0200"
      },
      "message": "sched: replace migration_thread with cpu_stop\n\nCurrently migration_thread is serving three purposes - migration\npusher, context to execute active_load_balance() and forced context\nswitcher for expedited RCU synchronize_sched.  All three roles are\nhardcoded into migration_thread() and determining which job is\nscheduled is slightly messy.\n\nThis patch kills migration_thread and replaces all three uses with\ncpu_stop.  The three different roles of migration_thread() are\nsplitted into three separate cpu_stop callbacks -\nmigration_cpu_stop(), active_load_balance_cpu_stop() and\nsynchronize_sched_expedited_cpu_stop() - and each use case now simply\nasks cpu_stop to execute the callback as necessary.\n\nsynchronize_sched_expedited() was implemented with private\npreallocated resources and custom multi-cpu queueing and waiting\nlogic, both of which are provided by cpu_stop.\nsynchronize_sched_expedited_count is made atomic and all other shared\nresources along with the mutex are dropped.\n\nsynchronize_sched_expedited() also implemented a check to detect cases\nwhere not all the callback got executed on their assigned cpus and\nfall back to synchronize_sched().  If called with cpu hotplug blocked,\ncpu_stop already guarantees that and the condition cannot happen;\notherwise, stop_machine() would break.  However, this patch preserves\nthe paranoid check using a cpumask to record on which cpus the stopper\nran so that it can serve as a bisection point if something actually\ngoes wrong theree.\n\nBecause the internal execution state is no longer visible,\nrcu_expedited_torture_stats() is removed.\n\nThis patch also renames cpu_stop threads to from \"stopper/%d\" to\n\"migration/%d\".  The names of these threads ultimately don\u0027t matter\nand there\u0027s no reason to make unnecessary userland visible changes.\n\nWith this patch applied, stop_machine() and sched now share the same\nresources.  stop_machine() is faster without wasting any resources and\nsched migration users are much cleaner.\n\nSigned-off-by: Tejun Heo \u003ctj@kernel.org\u003e\nAcked-by: Peter Zijlstra \u003cpeterz@infradead.org\u003e\nCc: Ingo Molnar \u003cmingo@elte.hu\u003e\nCc: Dipankar Sarma \u003cdipankar@in.ibm.com\u003e\nCc: Josh Triplett \u003cjosh@freedesktop.org\u003e\nCc: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: Oleg Nesterov \u003coleg@redhat.com\u003e\nCc: Dimitri Sivanich \u003csivanich@sgi.com\u003e\n"
    },
    {
      "commit": "d9f1bb6ad7fc53c406706f47858dd5ff030b14a3",
      "tree": "4af519d68b396e372e6a5afbb5e968de3bacd123",
      "parents": [
        "056ba4a9bea5f32781a36b797c562fb731e5eaa6"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Feb 25 14:06:47 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Fri Feb 26 08:20:46 2010 +0100"
      },
      "message": "rcu: Make rcu_read_lock_sched_held() take boot time into account\n\nBefore the scheduler starts, all tasks are non-preemptible by\ndefinition. So, during that time, rcu_read_lock_sched_held()\nneeds to always return \"true\".  This patch makes that be so.\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: \u003c1267135607-7056-2-git-send-email-paulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "bf66f18e79e34c421bbd8f6511e2c556b779df2f",
      "tree": "2348e3bc8392addf7959fbe94003f7e0da2a1c8b",
      "parents": [
        "46a1e34eda805501a8b32f26394faa435149f6d1"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Jan 04 15:09:10 2010 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Wed Jan 13 09:06:05 2010 +0100"
      },
      "message": "rcu: Add force_quiescent_state() testing to rcutorture\n\nAdd force_quiescent_state() testing to rcutorture, with a\nseparate thread that repeatedly invokes force_quiescent_state()\nin bursts. This can greatly increase the probability of\nencountering certain types of race conditions.\n\nSuggested-by: Josh Triplett \u003cjosh@joshtriplett.org\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: \u003c1262646551116-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "234da7bcdc7aaa935846534c3b726dbc79a9cdd5",
      "tree": "a391afd465d6493a9f1bb274c225bab4d303aad0",
      "parents": [
        "416eb39556a03d1c7e52b0791e9052ccd71db241"
      ],
      "author": {
        "name": "Frederic Weisbecker",
        "email": "fweisbec@gmail.com",
        "time": "Wed Dec 16 20:21:05 2009 +0100"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Dec 17 09:46:44 2009 +0100"
      },
      "message": "sched: Teach might_sleep() about preemptible RCU\n\nIn practice, it is harmless to voluntarily sleep in a\nrcu_read_lock() section if we are running under preempt rcu, but\nit is illegal if we build a kernel running non-preemptable rcu.\n\nCurrently, might_sleep() doesn\u0027t notice sleepable operations\nunder rcu_read_lock() sections if we are running under\npreemptable rcu because preempt_count() is left untouched after\nrcu_read_lock() in this case. But we want developers who test\ntheir changes under such config to notice the \"sleeping while\natomic\" issues.\n\nSo we add rcu_read_lock_nesting to prempt_count() in\nmight_sleep() checks.\n\n[ v2: Handle rcu-tiny ]\nSigned-off-by: Frederic Weisbecker \u003cfweisbec@gmail.com\u003e\nReviewed-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: Peter Zijlstra \u003cpeterz@infradead.org\u003e\nLKML-Reference: \u003c1260991265-8451-1-git-send-regression-fweisbec@gmail.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "6ebb237bece23275d1da149b61a342f0d4d06a08",
      "tree": "5f3d99f6ce2e1e98736e5708eecb5bf217f78fde",
      "parents": [
        "9f680ab41485edfdc96331b70afa7513aa0a7720"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Nov 22 08:53:50 2009 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sun Nov 22 18:58:16 2009 +0100"
      },
      "message": "rcu: Re-arrange code to reduce #ifdef pain\n\nRemove #ifdefs from kernel/rcupdate.c and\ninclude/linux/rcupdate.h by moving code to\ninclude/linux/rcutiny.h, include/linux/rcutree.h, and\nkernel/rcutree.c.\n\nAlso remove some definitions that are no longer used.\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: \u003c1258908830885-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "9f680ab41485edfdc96331b70afa7513aa0a7720",
      "tree": "620b34f8129c0ea4ddee033c9875a9f60bfba2ae",
      "parents": [
        "b668c9cf3e58739dac54a1d6f42f2b4bdd980b3e"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Nov 22 08:53:49 2009 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sun Nov 22 18:58:16 2009 +0100"
      },
      "message": "rcu: Eliminate unneeded function wrapping\n\nThe functions rcu_init() is a wrapper for __rcu_init(), and also\nsets up the CPU-hotplug notifier for rcu_barrier_cpu_hotplug().\nBut TINY_RCU doesn\u0027t need CPU-hotplug notification, and the\nrcu_barrier_cpu_hotplug() is a simple wrapper for\nrcu_cpu_notify().\n\nSo push rcu_init() out to kernel/rcutree.c and kernel/rcutiny.c\nand get rid of the wrapper function rcu_barrier_cpu_hotplug().\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: \u003c12589088302320-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "019129d595caaa5bd0b41d128308da1be6a91869",
      "tree": "2db09ada99b0b8ca0a6423626fa85a9c1a7fc141",
      "parents": [
        "37c72e56f6b234ea7387ba530434a80abf2658d8"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Oct 14 10:15:56 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Oct 15 11:17:17 2009 +0200"
      },
      "message": "rcu: Stopgap fix for synchronize_rcu_expedited() for TREE_PREEMPT_RCU\n\nFor the short term, map synchronize_rcu_expedited() to\nsynchronize_rcu() for TREE_PREEMPT_RCU and to\nsynchronize_sched_expedited() for TREE_RCU.\n\nLonger term, there needs to be a real expedited grace period for\nTREE_PREEMPT_RCU, but candidate patches to date are considerably\nmore complex and intrusive.\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\nCc: npiggin@suse.de\nCc: jens.axboe@oracle.com\nLKML-Reference: \u003c12555405592331-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "9b2619aff0332e95ea5eb7a0d75b0208818d871c",
      "tree": "a1aed182c4f1ec511352c0e3cb3eba0e20535263",
      "parents": [
        "1eba8f84380bede3c602bd7758dea96925cead01"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Sep 23 09:50:43 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Wed Sep 23 19:46:30 2009 +0200"
      },
      "message": "rcu: Clean up code to address Ingo\u0027s checkpatch feedback\n\nMove declarations and update storage classes to make checkpatch happy.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\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: \u003c12537246441701-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "1eba8f84380bede3c602bd7758dea96925cead01",
      "tree": "32dd97671016c9fdc24d75be50cc8540e6cc0730",
      "parents": [
        "fc2219d49ef1606e7fd2c88af2b423b01ff3d319"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Sep 23 09:50:42 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Wed Sep 23 19:46:29 2009 +0200"
      },
      "message": "rcu: Clean up code based on review feedback from Josh Triplett, part 2\n\nThese issues identified during an old-fashioned face-to-face code\nreview extending over many hours.\n\no\tAdd comments for tricky parts of code, and correct comments\n\tthat have passed their sell-by date.\n\no\tGet rid of the vestiges of rcu_init_sched(), which is no\n\tlonger needed now that PREEMPT_RCU is gone.\n\no\tMove the #include of rcutree_plugin.h to the end of\n\trcutree.c, which means that, rather than having a random\n\tcollection of forward declarations, the new set of forward\n\tdeclarations document the set of plugins.  The new home for\n\tthis #include also allows __rcu_init_preempt() to move into\n\trcutree_plugin.h.\n\no\tFix rcu_preempt_check_callbacks() to be static.\n\nSuggested-by: Josh Triplett \u003cjosh@joshtriplett.org\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\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: \u003c12537246443924-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\nPeter Zijlstra \u003cpeterz@infradead.org\u003e\n"
    },
    {
      "commit": "fc2219d49ef1606e7fd2c88af2b423b01ff3d319",
      "tree": "1c1cba7e4334898a98cf0e2c992e8cfef4b34979",
      "parents": [
        "0729e196147692d84d4c099fcff056eba2ed61d8"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Sep 23 09:50:41 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Wed Sep 23 19:46:29 2009 +0200"
      },
      "message": "rcu: Clean up code based on review feedback from Josh Triplett\n\nThese issues identified during an old-fashioned face-to-face code\nreview extended over many hours.\n\no\tBury various forms of the \"rsp-\u003ecompleted \u003d\u003d rsp-\u003egpnum\"\n\tcomparison into an rcu_gp_in_progress() function, which has\n\tthe beneficial side-effect of forcing consistent use of\n\tACCESS_ONCE().\n\no\tReplace hand-coded arithmetic with DIV_ROUND_UP().\n\no\tBury several \"!list_empty(\u0026rnp-\u003eblocked_tasks[rnp-\u003egpnum \u0026 0x01])\"\n\tinstances into an rcu_preempted_readers() function, as this\n\texpression indicates that there are no readers blocked\n\twithin RCU read-side critical sections blocking the current\n\tgrace period.  (Though there might well be similar readers\n\tblocking the next grace period.)\n\no\tRemove a dangling rcu_restart_cpu() declaration that has\n\tbeen dangling for almost 20 minor releases of the kernel.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nAcked-by: Peter Zijlstra \u003cpeterz@infradead.org\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\nCc: mathieu.desnoyers@polymtl.ca\nCc: josh@joshtriplett.org\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: rostedt@goodmis.org\nCc: Valdis.Kletnieks@vt.edu\nCc: dhowells@redhat.com\nLKML-Reference: \u003c12537246442687-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "a71fca58b7f4abca551ae2256ac08dd9123a03f9",
      "tree": "55bef0550ff2558a117d768426474e15b081ff4b",
      "parents": [
        "49e291266d0920264471d9d64268fb030e33a99a"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Fri Sep 18 10:28:19 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sat Sep 19 08:53:22 2009 +0200"
      },
      "message": "rcu: Fix whitespace inconsistencies\n\nFix a number of whitespace ^Ierrors in the include/linux/rcu*\nand the kernel/rcu* files.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\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\nLKML-Reference: \u003c20090918172819.GA24405@linux.vnet.ibm.com\u003e\n[ did more checkpatch fixlets ]\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "16e3081191837a6a04733de5cd5d1d1b303140d4",
      "tree": "6b64a4613b9ac57da30518626a259b6aeeef4944",
      "parents": [
        "c3422bea5f09b0e85704f51f2b01271630b8940b"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sun Sep 13 09:15:11 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Fri Sep 18 00:06:53 2009 +0200"
      },
      "message": "rcu: Fix synchronize_rcu() for TREE_PREEMPT_RCU\n\nThe redirection of synchronize_sched() to synchronize_rcu() was\nappropriate for TREE_RCU, but not for TREE_PREEMPT_RCU.\n\nFix this by creating an underlying synchronize_sched().  TREE_RCU\nthen redirects synchronize_rcu() to synchronize_sched(), while\nTREE_PREEMPT_RCU has its own version of synchronize_rcu().\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\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\nLKML-Reference: \u003c12528585111916-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "f41d911f8c49a5d65c86504c19e8204bb605c4fd",
      "tree": "59bcd3048652ef290b3e19d2904409afd5c90eb3",
      "parents": [
        "a157229cabd6dd8cfa82525fc9bf730c94cc9ac2"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat Aug 22 13:56:52 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sun Aug 23 10:32:40 2009 +0200"
      },
      "message": "rcu: Merge preemptable-RCU functionality into hierarchical RCU\n\nCreate a kernel/rcutree_plugin.h file that contains definitions\nfor preemptable RCU (or, under the #else branch of the #ifdef,\nempty definitions for the classic non-preemptable semantics).\nThese definitions fit into plugins defined in kernel/rcutree.c\nfor this purpose.\n\nThis variant of preemptable RCU uses a new algorithm whose\nread-side expense is roughly that of classic hierarchical RCU\nunder CONFIG_PREEMPT. This new algorithm\u0027s update-side expense\nis similar to that of classic hierarchical RCU, and, in absence\nof read-side preemption or blocking, is exactly that of classic\nhierarchical RCU.  Perhaps more important, this new algorithm\nhas a much simpler implementation, saving well over 1,000 lines\nof code compared to mainline\u0027s implementation of preemptable\nRCU, which will hopefully be retired in favor of this new\nalgorithm.\n\nThe simplifications are obtained by maintaining per-task\nnesting state for running tasks, and using a simple\nlock-protected algorithm to handle accounting when tasks block\nwithin RCU read-side critical sections, making use of lessons\nlearned while creating numerous user-level RCU implementations\nover the past 18 months.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\nCc: mathieu.desnoyers@polymtl.ca\nCc: josht@linux.vnet.ibm.com\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nLKML-Reference: \u003c12509746134003-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "a157229cabd6dd8cfa82525fc9bf730c94cc9ac2",
      "tree": "886013efc2f25dab915640acf46151fac7ae57b4",
      "parents": [
        "22f00b69f6a7e1e18e821979a23e8307c2de9888"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat Aug 22 13:56:51 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sun Aug 23 10:32:39 2009 +0200"
      },
      "message": "rcu: Simplify rcu_pending()/rcu_check_callbacks() API\n\nAll calls from outside RCU are of the form:\n\n\tif (rcu_pending(cpu))\n\t\trcu_check_callbacks(cpu, user);\n\nThis is silly, instead we put a call to rcu_pending() in\nrcu_check_callbacks(), and then make the outside calls be to\nrcu_check_callbacks().  This cuts down on the code a bit and\nalso gives the compiler a better chance of optimizing.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\nCc: mathieu.desnoyers@polymtl.ca\nCc: josht@linux.vnet.ibm.com\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nLKML-Reference: \u003c125097461311-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "bc33f24bdca8b6e97376e3a182ab69e6cdefa989",
      "tree": "86b56c35677fe19e6a2f39414526ece3625dcb32",
      "parents": [
        "d6714c22b43fbcbead7e7b706ff270e15f04a791"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat Aug 22 13:56:47 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sun Aug 23 10:32:37 2009 +0200"
      },
      "message": "rcu: Consolidate sparse and lockdep declarations in include/linux/rcupdate.h\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\nCc: mathieu.desnoyers@polymtl.ca\nCc: josht@linux.vnet.ibm.com\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nLKML-Reference: \u003c12509746132349-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "d6714c22b43fbcbead7e7b706ff270e15f04a791",
      "tree": "1dc15e57d982351bed45b7b9768a118f86b88c19",
      "parents": [
        "9f77da9f40045253e91f55c12d4481254b513d2d"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat Aug 22 13:56:46 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sun Aug 23 10:32:37 2009 +0200"
      },
      "message": "rcu: Renamings to increase RCU clarity\n\nMake RCU-sched, RCU-bh, and RCU-preempt be underlying\nimplementations, with \"RCU\" defined in terms of one of the\nthree.  Update the outdated rcu_qsctr_inc() names, as these\nfunctions no longer increment anything.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\nCc: mathieu.desnoyers@polymtl.ca\nCc: josht@linux.vnet.ibm.com\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nLKML-Reference: \u003c12509746132696-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "9f77da9f40045253e91f55c12d4481254b513d2d",
      "tree": "8699c413d1493855ca8b1205e1b63090f568af42",
      "parents": [
        "b560d8ad8583803978aaaeba50ef29dc8e97a610"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Sat Aug 22 13:56:45 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Sun Aug 23 10:32:36 2009 +0200"
      },
      "message": "rcu: Move private definitions from include/linux/rcutree.h to kernel/rcutree.h\n\nSome information hiding that makes it easier to merge\npreemptability into rcutree without descending into #include\nhell.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: laijs@cn.fujitsu.com\nCc: dipankar@in.ibm.com\nCc: akpm@linux-foundation.org\nCc: mathieu.desnoyers@polymtl.ca\nCc: josht@linux.vnet.ibm.com\nCc: dvhltc@us.ibm.com\nCc: niv@us.ibm.com\nCc: peterz@infradead.org\nCc: rostedt@goodmis.org\nLKML-Reference: \u003c1250974613373-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "03b042bf1dc14a268a3d65d38b4ec2a4261e8477",
      "tree": "10e422a1396087d14cec164d8f4962d7ce8bcf2d",
      "parents": [
        "c17ef45342cc033fdf7bdd5b28615e0090f8d2e7"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Jun 25 09:08:16 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Fri Jul 03 10:02:28 2009 +0200"
      },
      "message": "rcu: Add synchronize_sched_expedited() primitive\n\nThis adds the synchronize_sched_expedited() primitive that\nimplements the \"big hammer\" expedited RCU grace periods.\n\nThis primitive is placed in kernel/sched.c rather than\nkernel/rcupdate.c due to its need to interact closely with the\nmigration_thread() kthread.\n\nThe idea is to wake up this kthread with req-\u003etask set to NULL,\nin response to which the kthread reports the quiescent state\nresulting from the kthread having been scheduled.\n\nBecause this patch needs to fallback to the slow versions of\nthe primitives in response to some races with CPU onlining and\nofflining, a new synchronize_rcu_bh() primitive is added as\nwell.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: akpm@linux-foundation.org\nCc: torvalds@linux-foundation.org\nCc: davem@davemloft.net\nCc: dada1@cosmosbay.com\nCc: zbr@ioremap.net\nCc: jeff.chua.linux@gmail.com\nCc: paulus@samba.org\nCc: laijs@cn.fujitsu.com\nCc: jengelh@medozas.de\nCc: r000n@r000n.net\nCc: benh@kernel.crashing.org\nCc: mathieu.desnoyers@polymtl.ca\nLKML-Reference: \u003c12459460982947-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "7ba5c840e64d4a967379f1ae3eca73278180b11d",
      "tree": "b77d70ce2b80f3be27add39fcd3bc7fbfe7a0847",
      "parents": [
        "05cfbd66d07c44865983c8b65ae9d0037d874206"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Apr 13 21:31:17 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Tue Apr 14 11:33:43 2009 +0200"
      },
      "message": "rcu: Add __rcu_pending tracing to hierarchical RCU\n\nAdd tracing to __rcu_pending() to provide information on why RCU\nprocessing was kicked off.  This is helpful for debugging hierarchical\nRCU, and might also be helpful in learning how hierarchical RCU operates.\n\nLocated-by: Anton Blanchard \u003canton@au1.ibm.com\u003e\nTested-by: Anton Blanchard \u003canton@au1.ibm.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: anton@samba.org\nCc: akpm@linux-foundation.org\nCc: dipankar@in.ibm.com\nCc: manfred@colorfullife.com\nCc: cl@linux-foundation.org\nCc: josht@linux.vnet.ibm.com\nCc: schamp@sgi.com\nCc: niv@us.ibm.com\nCc: dvhltc@us.ibm.com\nCc: ego@in.ibm.com\nCc: laijs@cn.fujitsu.com\nCc: rostedt@goodmis.org\nCc: peterz@infradead.org\nCc: penberg@cs.helsinki.fi\nCc: andi@firstfloor.org\nCc: \"Paul E. McKenney\" \u003cpaulmck@linux.vnet.ibm.com\u003e\nLKML-Reference: \u003c1239683479943-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "ef631b0ca01655d24e9ca7e199262c4a46416a26",
      "tree": "0ef86d5b97c6e2de500e639ebb92da8f2ec8c863",
      "parents": [
        "27b19565fe4ca5b0e9d2ae98ce4b81ca728bf445"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Mon Apr 13 21:31:16 2009 -0700"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Tue Apr 14 11:31:50 2009 +0200"
      },
      "message": "rcu: Make hierarchical RCU less IPI-happy\n\nThis patch fixes a hierarchical-RCU performance bug located by Anton\nBlanchard.  The problem stems from a misguided attempt to provide a\nwork-around for jiffies-counter failure.  This work-around uses a per-CPU\nn_rcu_pending counter, which is incremented on each call to rcu_pending(),\nwhich in turn is called from each scheduling-clock interrupt.  Each CPU\nthen treats this counter as a surrogate for the jiffies counter, so\nthat if the jiffies counter fails to advance, the per-CPU n_rcu_pending\ncounter will cause RCU to invoke force_quiescent_state(), which in turn\nwill (among other things) send resched IPIs to CPUs that have thus far\nfailed to pass through an RCU quiescent state.\n\nUnfortunately, each CPU resets only its own counter after sending a\nbatch of IPIs.  This means that the other CPUs will also (needlessly)\nsend -another- round of IPIs, for a full N-squared set of IPIs in the\nworst case every three scheduler-clock ticks until the grace period\nfinally ends.  It is not reasonable for a given CPU to reset each and\nevery n_rcu_pending for all the other CPUs, so this patch instead simply\ndisables the jiffies-counter \"training wheels\", thus eliminating the\nexcessive IPIs.\n\nNote that the jiffies-counter IPIs do not have this problem due to\nthe fact that the jiffies counter is global, so that the CPU sending\nthe IPIs can easily reset things, thus preventing the other CPUs from\nsending redundant IPIs.\n\nNote also that the n_rcu_pending counter remains, as it will continue to\nbe used for tracing.  It may also see use to update the jiffies counter,\nshould an appropriate kick-the-jiffies-counter API appear.\n\nLocated-by: Anton Blanchard \u003canton@au1.ibm.com\u003e\nTested-by: Anton Blanchard \u003canton@au1.ibm.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nCc: anton@samba.org\nCc: akpm@linux-foundation.org\nCc: dipankar@in.ibm.com\nCc: manfred@colorfullife.com\nCc: cl@linux-foundation.org\nCc: josht@linux.vnet.ibm.com\nCc: schamp@sgi.com\nCc: niv@us.ibm.com\nCc: dvhltc@us.ibm.com\nCc: ego@in.ibm.com\nCc: laijs@cn.fujitsu.com\nCc: rostedt@goodmis.org\nCc: peterz@infradead.org\nCc: penberg@cs.helsinki.fi\nCc: andi@firstfloor.org\nCc: \"Paul E. McKenney\" \u003cpaulmck@linux.vnet.ibm.com\u003e\nLKML-Reference: \u003c12396834793575-git-send-email-\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "ac44021fccd8f1f2b267b004f23a2e8d7ef05f7b",
      "tree": "164d43e03bff92e66058a2bd2a57a3af9a4723c2",
      "parents": [
        "a979241c532f07c201fe94e0a632107268f02578"
      ],
      "author": {
        "name": "Eduard - Gabriel Munteanu",
        "email": "eduard.munteanu@linux360.ro",
        "time": "Mon Mar 23 15:12:21 2009 +0200"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Fri Apr 03 12:23:05 2009 +0200"
      },
      "message": "kmemtrace, rcu: don\u0027t include unnecessary headers, allow kmemtrace w/ tracepoints\n\nImpact: cleanup\n\nlinux/percpu.h includes linux/slab.h, which generates circular inclusion\ndependencies when trying to switch kmemtrace to use tracepoints instead\nof markers.\n\nThis patch allows tracing within slab headers\u0027 inline functions.\n\nSigned-off-by: Pekka Enberg \u003cpenberg@cs.helsinki.fi\u003e\nCc: Eduard - Gabriel Munteanu \u003ceduard.munteanu@linux360.ro\u003e\nCc: paulmck@linux.vnet.ibm.com\nLKML-Reference: \u003c1237898630.25315.83.camel@penberg-laptop\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "b1f77b0581b8fd837acb4a973f7d5496cae6efee",
      "tree": "4faa2e4285c31dd70d1d20b4172d1eed55ba7330",
      "parents": [
        "255d11bc910fd38153156a0c5ebb256657290882"
      ],
      "author": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Fri Mar 13 03:20:49 2009 +0100"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Fri Apr 03 12:23:02 2009 +0200"
      },
      "message": "kmemtrace, rcu: fix linux/rcutree.h and linux/rcuclassic.h dependencies\n\nImpact: build fix for all non-x86 architectures\n\nWe want to remove percpu.h from rcuclassic.h/rcutree.h (for upcoming\nkmemtrace changes) but that would break the DECLARE_PER_CPU based\ndeclarations in these files.\n\nMove the quiescent counter management functions to their respective\nRCU implementation .c files - they were slightly above the inlining\nlimit anyway.\n\nCc: Pekka Enberg \u003cpenberg@cs.helsinki.fi\u003e\nCc: Eduard - Gabriel Munteanu \u003ceduard.munteanu@linux360.ro\u003e\nCc: paulmck@linux.vnet.ibm.com\nLKML-Reference: \u003c1237898630.25315.83.camel@penberg-laptop\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "a682604838763981613e42015cd0e39f2989d6bb",
      "tree": "29eae425e484edc494807702696c240ce09ba3f5",
      "parents": [
        "694593e3374a67d95ece6a275a1f181644c2c4d8"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Wed Feb 25 18:03:42 2009 -0800"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Feb 26 04:08:14 2009 +0100"
      },
      "message": "rcu: Teach RCU that idle task is not quiscent state at boot\n\nThis patch fixes a bug located by Vegard Nossum with the aid of\nkmemcheck, updated based on review comments from Nick Piggin,\nIngo Molnar, and Andrew Morton.  And cleans up the variable-name\nand function-name language.  ;-)\n\nThe boot CPU runs in the context of its idle thread during boot-up.\nDuring this time, idle_cpu(0) will always return nonzero, which will\nfool Classic and Hierarchical RCU into deciding that a large chunk of\nthe boot-up sequence is a big long quiescent state.  This in turn causes\nRCU to prematurely end grace periods during this time.\n\nThis patch changes the rcutree.c and rcuclassic.c rcu_check_callbacks()\nfunction to ignore the idle task as a quiescent state until the\nsystem has started up the scheduler in rest_init(), introducing a\nnew non-API function rcu_idle_now_means_idle() to inform RCU of this\ntransition.  RCU maintains an internal rcu_idle_cpu_truthful variable\nto track this state, which is then used by rcu_check_callback() to\ndetermine if it should believe idle_cpu().\n\nBecause this patch has the effect of disallowing RCU grace periods\nduring long stretches of the boot-up sequence, this patch also introduces\nJosh Triplett\u0027s UP-only optimization that makes synchronize_rcu() be a\nno-op if num_online_cpus() returns 1.  This allows boot-time code that\ncalls synchronize_rcu() to proceed normally.  Note, however, that RCU\ncallbacks registered by call_rcu() will likely queue up until later in\nthe boot sequence.  Although rcuclassic and rcutree can also use this\nsame optimization after boot completes, rcupreempt must restrict its\nuse of this optimization to the portion of the boot sequence before the\nscheduler starts up, given that an rcupreempt RCU read-side critical\nsection may be preeempted.\n\nIn addition, this patch takes Nick Piggin\u0027s suggestion to make the\nsystem_state global variable be __read_mostly.\n\nChanges since v4:\n\no\tChanges the name of the introduced function and variable to\n\tbe less emotional.  ;-)\n\nChanges since v3:\n\no\tWARN_ON(nr_context_switches() \u003e 0) to verify that RCU\n\tswitches out of boot-time mode before the first context\n\tswitch, as suggested by Nick Piggin.\n\nChanges since v2:\n\no\tCreated rcu_blocking_is_gp() internal-to-RCU API that\n\tdetermines whether a call to synchronize_rcu() is itself\n\ta grace period.\n\no\tThe definition of rcu_blocking_is_gp() for rcuclassic and\n\trcutree checks to see if but a single CPU is online.\n\no\tThe definition of rcu_blocking_is_gp() for rcupreempt\n\tchecks to see both if but a single CPU is online and if\n\tthe system is still in early boot.\n\n\tThis allows rcupreempt to again work correctly if running\n\ton a single CPU after booting is complete.\n\no\tAdded check to rcupreempt\u0027s synchronize_sched() for there\n\tbeing but one online CPU.\n\nTested all three variants both SMP and !SMP, booted fine, passed a short\nrcutorture test on both x86 and Power.\n\nLocated-by: Vegard Nossum \u003cvegard.nossum@gmail.com\u003e\nTested-by: Vegard Nossum \u003cvegard.nossum@gmail.com\u003e\nTested-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    },
    {
      "commit": "64db4cfff99c04cd5f550357edcc8780f96b54a2",
      "tree": "4856e788d21f0e31ed78a22b70b4521f7237705e",
      "parents": [
        "d110ec3a1e1f522e2e9dfceb9c36d6590c26d2d4"
      ],
      "author": {
        "name": "Paul E. McKenney",
        "email": "paulmck@linux.vnet.ibm.com",
        "time": "Thu Dec 18 21:55:32 2008 +0100"
      },
      "committer": {
        "name": "Ingo Molnar",
        "email": "mingo@elte.hu",
        "time": "Thu Dec 18 21:56:04 2008 +0100"
      },
      "message": "\"Tree RCU\": scalable classic RCU implementation\n\nThis patch fixes a long-standing performance bug in classic RCU that\nresults in massive internal-to-RCU lock contention on systems with\nmore than a few hundred CPUs.  Although this patch creates a separate\nflavor of RCU for ease of review and patch maintenance, it is intended\nto replace classic RCU.\n\nThis patch still handles stress better than does mainline, so I am still\ncalling it ready for inclusion.  This patch is against the -tip tree.\nNevertheless, experience on an actual 1000+ CPU machine would still be\nmost welcome.\n\nMost of the changes noted below were found while creating an rcutiny\n(which should permit ejecting the current rcuclassic) and while doing\ndetailed line-by-line documentation.\n\nUpdates from v9 (http://lkml.org/lkml/2008/12/2/334):\n\no\tFixes from remainder of line-by-line code walkthrough,\n\tincluding comment spelling, initialization, undesirable\n\tnarrowing due to type conversion, removing redundant memory\n\tbarriers, removing redundant local-variable initialization,\n\tand removing redundant local variables.\n\n\tI do not believe that any of these fixes address the CPU-hotplug\n\tissues that Andi Kleen was seeing, but please do give it a whirl\n\tin case the machine is smarter than I am.\n\n\tA writeup from the walkthrough may be found at the following\n\tURL, in case you are suffering from terminal insomnia or\n\tmasochism:\n\n\thttp://www.kernel.org/pub/linux/kernel/people/paulmck/tmp/rcutree-walkthrough.2008.12.16a.pdf\n\no\tMade rcutree tracing use seq_file, as suggested some time\n\tago by Lai Jiangshan.\n\no\tAdded a .csv variant of the rcudata debugfs trace file, to allow\n\tpeople having thousands of CPUs to drop the data into\n\ta spreadsheet.\tTested with oocalc and gnumeric.  Updated\n\tdocumentation to suit.\n\nUpdates from v8 (http://lkml.org/lkml/2008/11/15/139):\n\no\tFix a theoretical race between grace-period initialization and\n\tforce_quiescent_state() that could occur if more than three\n\tjiffies were required to carry out the grace-period\n\tinitialization.  Which it might, if you had enough CPUs.\n\no\tApply Ingo\u0027s printk-standardization patch.\n\no\tSubstitute local variables for repeated accesses to global\n\tvariables.\n\no\tFix comment misspellings and redundant (but harmless) increments\n\tof -\u003en_rcu_pending (this latter after having explicitly added it).\n\no\tApply checkpatch fixes.\n\nUpdates from v7 (http://lkml.org/lkml/2008/10/10/291):\n\no\tFixed a number of problems noted by Gautham Shenoy, including\n\tthe cpu-stall-detection bug that he was having difficulty\n\tconvincing me was real.  ;-)\n\no\tChanged cpu-stall detection to wait for ten seconds rather than\n\tthree in order to reduce false positive, as suggested by Ingo\n\tMolnar.\n\no\tProduced a design document (http://lwn.net/Articles/305782/).\n\tThe act of writing this document uncovered a number of both\n\ttheoretical and \"here and now\" bugs as noted below.\n\no\tFix dynticks_nesting accounting confusion, simplify WARN_ON()\n\tcondition, fix kerneldoc comments, and add memory barriers\n\tin dynticks interface functions.\n\no\tAdd more data to tracing.\n\no\tRemove unused \"rcu_barrier\" field from rcu_data structure.\n\no\tCount calls to rcu_pending() from scheduling-clock interrupt\n\tto use as a surrogate timebase should jiffies stop counting.\n\no\tFix a theoretical race between force_quiescent_state() and\n\tgrace-period initialization.  Yes, initialization does have to\n\tgo on for some jiffies for this race to occur, but given enough\n\tCPUs...\n\nUpdates from v6 (http://lkml.org/lkml/2008/9/23/448):\n\no\tFix a number of checkpatch.pl complaints.\n\no\tApply review comments from Ingo Molnar and Lai Jiangshan\n\ton the stall-detection code.\n\no\tFix several bugs in !CONFIG_SMP builds.\n\no\tFix a misspelled config-parameter name so that RCU now announces\n\tat boot time if stall detection is configured.\n\no\tRun tests on numerous combinations of configurations parameters,\n\twhich after the fixes above, now build and run correctly.\n\nUpdates from v5 (http://lkml.org/lkml/2008/9/15/92, bad subject line):\n\no\tFix a compiler error in the !CONFIG_FANOUT_EXACT case (blew a\n\tchangeset some time ago, and finally got around to retesting\n\tthis option).\n\no\tFix some tracing bugs in rcupreempt that caused incorrect\n\ttotals to be printed.\n\no\tI now test with a more brutal random-selection online/offline\n\tscript (attached).  Probably more brutal than it needs to be\n\ton the people reading it as well, but so it goes.\n\no\tA number of optimizations and usability improvements:\n\n\to\tMake rcu_pending() ignore the grace-period timeout when\n\t\tthere is no grace period in progress.\n\n\to\tMake force_quiescent_state() avoid going for a global\n\t\tlock in the case where there is no grace period in\n\t\tprogress.\n\n\to\tRearrange struct fields to improve struct layout.\n\n\to\tMake call_rcu() initiate a grace period if RCU was\n\t\tidle, rather than waiting for the next scheduling\n\t\tclock interrupt.\n\n\to\tInvoke rcu_irq_enter() and rcu_irq_exit() only when\n\t\tidle, as suggested by Andi Kleen.  I still don\u0027t\n\t\tcompletely trust this change, and might back it out.\n\n\to\tMake CONFIG_RCU_TRACE be the single config variable\n\t\tmanipulated for all forms of RCU, instead of the prior\n\t\tconfusion.\n\n\to\tDocument tracing files and formats for both rcupreempt\n\t\tand rcutree.\n\nUpdates from v4 for those missing v5 given its bad subject line:\n\no\tSeparated dynticks interface so that NMIs and irqs call separate\n\tfunctions, greatly simplifying it.  In particular, this code\n\tno longer requires a proof of correctness.  ;-)\n\no\tSeparated dynticks state out into its own per-CPU structure,\n\tavoiding the duplicated accounting.\n\no\tThe case where a dynticks-idle CPU runs an irq handler that\n\tinvokes call_rcu() is now correctly handled, forcing that CPU\n\tout of dynticks-idle mode.\n\no\tReview comments have been applied (thank you all!!!).\n\tFor but one example, fixed the dynticks-ordering issue that\n\tManfred pointed out, saving me much debugging.  ;-)\n\no\tAdjusted rcuclassic and rcupreempt to handle dynticks changes.\n\nAttached is an updated patch to Classic RCU that applies a hierarchy,\ngreatly reducing the contention on the top-level lock for large machines.\nThis passes 10-hour concurrent rcutorture and online-offline testing on\n128-CPU ppc64 without dynticks enabled, and exposes some timekeeping\nbugs in presence of dynticks (exciting working on a system where\n\"sleep 1\" hangs until interrupted...), which were fixed in the\n2.6.27 kernel.  It is getting more reliable than mainline by some\nmeasures, so the next version will be against -tip for inclusion.\nSee also Manfred Spraul\u0027s recent patches (or his earlier work from\n2004 at http://marc.info/?l\u003dlinux-kernel\u0026m\u003d108546384711797\u0026w\u003d2).\nWe will converge onto a common patch in the fullness of time, but are\ncurrently exploring different regions of the design space.  That said,\nI have already gratefully stolen quite a few of Manfred\u0027s ideas.\n\nThis patch provides CONFIG_RCU_FANOUT, which controls the bushiness\nof the RCU hierarchy.  Defaults to 32 on 32-bit machines and 64 on\n64-bit machines.  If CONFIG_NR_CPUS is less than CONFIG_RCU_FANOUT,\nthere is no hierarchy.  By default, the RCU initialization code will\nadjust CONFIG_RCU_FANOUT to balance the hierarchy, so strongly NUMA\narchitectures may choose to set CONFIG_RCU_FANOUT_EXACT to disable\nthis balancing, allowing the hierarchy to be exactly aligned to the\nunderlying hardware.  Up to two levels of hierarchy are permitted\n(in addition to the root node), allowing up to 16,384 CPUs on 32-bit\nsystems and up to 262,144 CPUs on 64-bit systems.  I just know that I\nam going to regret saying this, but this seems more than sufficient\nfor the foreseeable future.  (Some architectures might wish to set\nCONFIG_RCU_FANOUT\u003d4, which would limit such architectures to 64 CPUs.\nIf this becomes a real problem, additional levels can be added, but I\ndoubt that it will make a significant difference on real hardware.)\n\nIn the common case, a given CPU will manipulate its private rcu_data\nstructure and the rcu_node structure that it shares with its immediate\nneighbors.  This can reduce both lock and memory contention by multiple\norders of magnitude, which should eliminate the need for the strange\nmanipulations that are reported to be required when running Linux on\nvery large systems.\n\nSome shortcomings:\n\no\tMore bugs will probably surface as a result of an ongoing\n\tline-by-line code inspection.\n\n\tPatches will be provided as required.\n\no\tThere are probably hangs, rcutorture failures, \u0026c.  Seems\n\tquite stable on a 128-CPU machine, but that is kind of small\n\tcompared to 4096 CPUs.  However, seems to do better than\n\tmainline.\n\n\tPatches will be provided as required.\n\no\tThe memory footprint of this version is several KB larger\n\tthan rcuclassic.\n\n\tA separate UP-only rcutiny patch will be provided, which will\n\treduce the memory footprint significantly, even compared\n\tto the old rcuclassic.  One such patch passes light testing,\n\tand has a memory footprint smaller even than rcuclassic.\n\tInitial reaction from various embedded guys was \"it is not\n\tworth it\", so am putting it aside.\n\nCredits:\n\no\tManfred Spraul for ideas, review comments, and bugs spotted,\n\tas well as some good friendly competition.  ;-)\n\no\tJosh Triplett, Ingo Molnar, Peter Zijlstra, Mathieu Desnoyers,\n\tLai Jiangshan, Andi Kleen, Andy Whitcroft, and Andrew Morton\n\tfor reviews and comments.\n\no\tThomas Gleixner for much-needed help with some timer issues\n\t(see patches below).\n\no\tJon M. Tollefson, Tim Pepper, Andrew Theurer, Jose R. Santos,\n\tAndy Whitcroft, Darrick Wong, Nishanth Aravamudan, Anton\n\tBlanchard, Dave Kleikamp, and Nathan Lynch for keeping machines\n\talive despite my heavy abuse^Wtesting.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\n"
    }
  ]
}