)]}' { "log": [ { "commit": "ba46df984b8e8114c3cf19c51670fab084bd4196", "tree": "ed41e3a2278dfc22bd7fda59e99d8c74af8f429d", "parents": [ "28c4dadd3a7221f5b9cd5c7d03c499788b193353" ], "author": { "name": "Al Viro", "email": "viro@ftp.linux.org.uk", "time": "Tue Oct 10 22:46:07 2006 +0100" }, "committer": { "name": "Linus Torvalds", "email": "torvalds@g5.osdl.org", "time": "Tue Oct 10 15:37:22 2006 -0700" }, "message": "[PATCH] __user annotations: futex\n\nSigned-off-by: Al Viro \u003cviro@zeniv.linux.org.uk\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n" }, { "commit": "ce2c6b53847afc444c4d0a7a1075c61f499c57a5", "tree": "ad7e920292169f1febcf0cdc12375a8473d75337", "parents": [ "2b8de5f50e4a302b83ebcd5b0120621336d50bd6" ], "author": { "name": "Thomas Gleixner", "email": "tglx@linutronix.de", "time": "Sat Aug 05 12:15:15 2006 -0700" }, "committer": { "name": "Linus Torvalds", "email": "torvalds@g5.osdl.org", "time": "Sun Aug 06 08:57:49 2006 -0700" }, "message": "[PATCH] futex: Apply recent futex fixes to futex_compat\n\nThe recent fixups in futex.c need to be applied to futex_compat.c too. Fixes\na hang reported by Olaf.\n\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nCc: Olaf Hering \u003colh@suse.de\u003e\nSigned-off-by: Andrew Morton \u003cakpm@osdl.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n" }, { "commit": "e3f2ddeac718c768fdac4b7fe69d465172f788a8", "tree": "5428532dc6c87710c35a71858425f6d726f0e44c", "parents": [ "627371d73cdd04ed23fe098755b4f855138ad9e0" ], "author": { "name": "Ingo Molnar", "email": "mingo@elte.hu", "time": "Sat Jul 29 05:17:57 2006 +0200" }, "committer": { "name": "Linus Torvalds", "email": "torvalds@g5.osdl.org", "time": "Fri Jul 28 21:02:00 2006 -0700" }, "message": "[PATCH] pi-futex: robust-futex exit\n\nFix robust PI-futexes to be properly unlocked on unexpected exit.\n\nFor this to work the kernel has to know whether a futex is a PI or a\nnon-PI one, because the semantics are different. Since the space in\nrelevant glibc data structures is extremely scarce, the best solution is\nto encode the \u0027PI\u0027 information in bit 0 of the robust list pointer.\nExisting (non-PI) glibc robust futexes have this bit always zero, so the\nABI is kept. New glibc with PI-robust-futexes will set this bit.\n\nFurther fixes from Thomas Gleixner \u003ctglx@linutronix.de\u003e\n\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\nSigned-off-by: Ulrich Drepper \u003cdrepper@redhat.com\u003e\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n" }, { "commit": "c87e2837be82df479a6bae9f155c43516d2feebc", "tree": "ad6ab35f0b78f71abaa7b05185e9e3f97809c6de", "parents": [ "0cdbee9920fb37eb2dc49b860c2b28862d647adc" ], "author": { "name": "Ingo Molnar", "email": "mingo@elte.hu", "time": "Tue Jun 27 02:54:58 2006 -0700" }, "committer": { "name": "Linus Torvalds", "email": "torvalds@g5.osdl.org", "time": "Tue Jun 27 17:32:47 2006 -0700" }, "message": "[PATCH] pi-futex: futex_lock_pi/futex_unlock_pi support\n\nThis adds the actual pi-futex implementation, based on rt-mutexes.\n\n[dino@in.ibm.com: fix an oops-causing race]\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Arjan van de Ven \u003carjan@linux.intel.com\u003e\nSigned-off-by: Dinakar Guniguntala \u003cdino@in.ibm.com\u003e\nSigned-off-by: Andrew Morton \u003cakpm@osdl.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n" }, { "commit": "e2970f2fb6950183a34e8545faa093eb49d186e1", "tree": "a4035274368d846488a3b0152925502c06b064b0", "parents": [ "66e5393a78b3fcca63e7748e38221dcca61c4aab" ], "author": { "name": "Ingo Molnar", "email": "mingo@elte.hu", "time": "Tue Jun 27 02:54:47 2006 -0700" }, "committer": { "name": "Linus Torvalds", "email": "torvalds@g5.osdl.org", "time": "Tue Jun 27 17:32:46 2006 -0700" }, "message": "[PATCH] pi-futex: futex code cleanups\n\nWe are pleased to announce \"lightweight userspace priority inheritance\" (PI)\nsupport for futexes. The following patchset and glibc patch implements it,\nontop of the robust-futexes patchset which is included in 2.6.16-mm1.\n\nWe are calling it lightweight for 3 reasons:\n\n - in the user-space fastpath a PI-enabled futex involves no kernel work\n (or any other PI complexity) at all. No registration, no extra kernel\n calls - just pure fast atomic ops in userspace.\n\n - in the slowpath (in the lock-contention case), the system call and\n scheduling pattern is in fact better than that of normal futexes, due to\n the \u0027integrated\u0027 nature of FUTEX_LOCK_PI. [more about that further down]\n\n - the in-kernel PI implementation is streamlined around the mutex\n abstraction, with strict rules that keep the implementation relatively\n simple: only a single owner may own a lock (i.e. no read-write lock\n support), only the owner may unlock a lock, no recursive locking, etc.\n\n Priority Inheritance - why, oh why???\n -------------------------------------\n\nMany of you heard the horror stories about the evil PI code circling Linux for\nyears, which makes no real sense at all and is only used by buggy applications\nand which has horrible overhead. Some of you have dreaded this very moment,\nwhen someone actually submits working PI code ;-)\n\nSo why would we like to see PI support for futexes?\n\nWe\u0027d like to see it done purely for technological reasons. We dont think it\u0027s\na buggy concept, we think it\u0027s useful functionality to offer to applications,\nwhich functionality cannot be achieved in other ways. We also think it\u0027s the\nright thing to do, and we think we\u0027ve got the right arguments and the right\nnumbers to prove that. We also believe that we can address all the\ncounter-arguments as well. For these reasons (and the reasons outlined below)\nwe are submitting this patch-set for upstream kernel inclusion.\n\nWhat are the benefits of PI?\n\n The short reply:\n ----------------\n\nUser-space PI helps achieving/improving determinism for user-space\napplications. In the best-case, it can help achieve determinism and\nwell-bound latencies. Even in the worst-case, PI will improve the statistical\ndistribution of locking related application delays.\n\n The longer reply:\n -----------------\n\nFirstly, sharing locks between multiple tasks is a common programming\ntechnique that often cannot be replaced with lockless algorithms. As we can\nsee it in the kernel [which is a quite complex program in itself], lockless\nstructures are rather the exception than the norm - the current ratio of\nlockless vs. locky code for shared data structures is somewhere between 1:10\nand 1:100. Lockless is hard, and the complexity of lockless algorithms often\nendangers to ability to do robust reviews of said code. I.e. critical RT\napps often choose lock structures to protect critical data structures, instead\nof lockless algorithms. Furthermore, there are cases (like shared hardware,\nor other resource limits) where lockless access is mathematically impossible.\n\nMedia players (such as Jack) are an example of reasonable application design\nwith multiple tasks (with multiple priority levels) sharing short-held locks:\nfor example, a highprio audio playback thread is combined with medium-prio\nconstruct-audio-data threads and low-prio display-colory-stuff threads. Add\nvideo and decoding to the mix and we\u0027ve got even more priority levels.\n\nSo once we accept that synchronization objects (locks) are an unavoidable fact\nof life, and once we accept that multi-task userspace apps have a very fair\nexpectation of being able to use locks, we\u0027ve got to think about how to offer\nthe option of a deterministic locking implementation to user-space.\n\nMost of the technical counter-arguments against doing priority inheritance\nonly apply to kernel-space locks. But user-space locks are different, there\nwe cannot disable interrupts or make the task non-preemptible in a critical\nsection, so the \u0027use spinlocks\u0027 argument does not apply (user-space spinlocks\nhave the same priority inversion problems as other user-space locking\nconstructs). Fact is, pretty much the only technique that currently enables\ngood determinism for userspace locks (such as futex-based pthread mutexes) is\npriority inheritance:\n\nCurrently (without PI), if a high-prio and a low-prio task shares a lock [this\nis a quite common scenario for most non-trivial RT applications], even if all\ncritical sections are coded carefully to be deterministic (i.e. all critical\nsections are short in duration and only execute a limited number of\ninstructions), the kernel cannot guarantee any deterministic execution of the\nhigh-prio task: any medium-priority task could preempt the low-prio task while\nit holds the shared lock and executes the critical section, and could delay it\nindefinitely.\n\n Implementation:\n ---------------\n\nAs mentioned before, the userspace fastpath of PI-enabled pthread mutexes\ninvolves no kernel work at all - they behave quite similarly to normal\nfutex-based locks: a 0 value means unlocked, and a value\u003d\u003dTID means locked.\n(This is the same method as used by list-based robust futexes.) Userspace uses\natomic ops to lock/unlock these mutexes without entering the kernel.\n\nTo handle the slowpath, we have added two new futex ops:\n\n FUTEX_LOCK_PI\n FUTEX_UNLOCK_PI\n\nIf the lock-acquire fastpath fails, [i.e. an atomic transition from 0 to TID\nfails], then FUTEX_LOCK_PI is called. The kernel does all the remaining work:\nif there is no futex-queue attached to the futex address yet then the code\nlooks up the task that owns the futex [it has put its own TID into the futex\nvalue], and attaches a \u0027PI state\u0027 structure to the futex-queue. The pi_state\nincludes an rt-mutex, which is a PI-aware, kernel-based synchronization\nobject. The \u0027other\u0027 task is made the owner of the rt-mutex, and the\nFUTEX_WAITERS bit is atomically set in the futex value. Then this task tries\nto lock the rt-mutex, on which it blocks. Once it returns, it has the mutex\nacquired, and it sets the futex value to its own TID and returns. Userspace\nhas no other work to perform - it now owns the lock, and futex value contains\nFUTEX_WAITERS|TID.\n\nIf the unlock side fastpath succeeds, [i.e. userspace manages to do a TID -\u003e\n0 atomic transition of the futex value], then no kernel work is triggered.\n\nIf the unlock fastpath fails (because the FUTEX_WAITERS bit is set), then\nFUTEX_UNLOCK_PI is called, and the kernel unlocks the futex on the behalf of\nuserspace - and it also unlocks the attached pi_state-\u003ert_mutex and thus wakes\nup any potential waiters.\n\nNote that under this approach, contrary to other PI-futex approaches, there is\nno prior \u0027registration\u0027 of a PI-futex. [which is not quite possible anyway,\ndue to existing ABI properties of pthread mutexes.]\n\nAlso, under this scheme, \u0027robustness\u0027 and \u0027PI\u0027 are two orthogonal properties\nof futexes, and all four combinations are possible: futex, robust-futex,\nPI-futex, robust+PI-futex.\n\n glibc support:\n --------------\n\nUlrich Drepper and Jakub Jelinek have written glibc support for PI-futexes\n(and robust futexes), enabling robust and PI (PTHREAD_PRIO_INHERIT) POSIX\nmutexes. (PTHREAD_PRIO_PROTECT support will be added later on too, no\nadditional kernel changes are needed for that). [NOTE: The glibc patch is\nobviously inofficial and unsupported without matching upstream kernel\nfunctionality.]\n\nthe patch-queue and the glibc patch can also be downloaded from:\n\n http://redhat.com/~mingo/PI-futex-patches/\n\nMany thanks go to the people who helped us create this kernel feature: Steven\nRostedt, Esben Nielsen, Benedikt Spranger, Daniel Walker, John Cooper, Arjan\nvan de Ven, Oleg Nesterov and others. Credits for related prior projects goes\nto Dirk Grambow, Inaky Perez-Gonzalez, Bill Huey and many others.\n\nClean up the futex code, before adding more features to it:\n\n - use u32 as the futex field type - that\u0027s the ABI\n - use __user and pointers to u32 instead of unsigned long\n - code style / comment style cleanups\n - rename hash-bucket name from \u0027bh\u0027 to \u0027hb\u0027.\n\nI checked the pre and post futex.o object files to make sure this\npatch has no code effects.\n\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Arjan van de Ven \u003carjan@linux.intel.com\u003e\nCc: Ulrich Drepper \u003cdrepper@redhat.com\u003e\nCc: Jakub Jelinek \u003cjakub@redhat.com\u003e\nSigned-off-by: Andrew Morton \u003cakpm@osdl.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n" }, { "commit": "9741ef964dc8bfeb6520825df9fed8f538c3336e", "tree": "6cc09d6b10a9ea9119a3a73e226300d747008bfe", "parents": [ "d425b274ba83ba4e7746a40446ec0ba3267de51f" ], "author": { "name": "Thomas Gleixner", "email": "tglx@linutronix.de", "time": "Fri Mar 31 02:31:32 2006 -0800" }, "committer": { "name": "Linus Torvalds", "email": "torvalds@g5.osdl.org", "time": "Fri Mar 31 12:18:59 2006 -0800" }, "message": "[PATCH] futex: check and validate timevals\n\nThe futex timeval is not checked for correctness. The change does not\nbreak existing applications as the timeval is supplied by glibc (and glibc\nalways passes a correct value), but the glibc-internal tests for this\nfunctionality fail.\n\nSigned-off-by: Thomas Gleixner \u003ctglx@tglx.de\u003e\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\nSigned-off-by: Andrew Morton \u003cakpm@osdl.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n" }, { "commit": "ec7e15d6486e9d1da1c2f344b670b8388ba7019b", "tree": "479d803ee546b536521dc87095c31781a98a0bb6", "parents": [ "4fa95ef639830ccf0ca1ad42ee9bed87ef642f32" ], "author": { "name": "Andrew Morton", "email": "akpm@osdl.org", "time": "Tue Mar 28 01:56:55 2006 -0800" }, "committer": { "name": "Linus Torvalds", "email": "torvalds@g5.osdl.org", "time": "Tue Mar 28 09:16:09 2006 -0800" }, "message": "[PATCH] compat_sys_futex() warning fix\n\nkernel/futex_compat.c: In function `compat_sys_futex\u0027:\nkernel/futex_compat.c:140: warning: passing arg 1 of `do_futex\u0027 makes integer from pointer without a cast\nkernel/futex_compat.c:140: warning: passing arg 5 of `do_futex\u0027 makes integer from pointer without a cast\n\nNot sure what Ingo was thinking of here. Put the casts back in.\n\nCc: Ingo Molnar \u003cmingo@elte.hu\u003e\nSigned-off-by: Andrew Morton \u003cakpm@osdl.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n" }, { "commit": "8f17d3a5049d32392b79925c73a0cf99ce6d5af0", "tree": "3c2aa0cbe337684d353dd2cfb0c177b4ae15217c", "parents": [ "8fdd6c6df7889dc89df3d9fe0f5bbe6733e39f48" ], "author": { "name": "Ingo Molnar", "email": "mingo@elte.hu", "time": "Mon Mar 27 01:16:27 2006 -0800" }, "committer": { "name": "Linus Torvalds", "email": "torvalds@g5.osdl.org", "time": "Mon Mar 27 08:44:49 2006 -0800" }, "message": "[PATCH] lightweight robust futexes updates\n\n- fix: initialize the robust list(s) to NULL in copy_process.\n\n- doc update\n\n- cleanup: rename _inuser to _inatomic\n\n- __user cleanups and other small cleanups\n\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\nCc: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nCc: Arjan van de Ven \u003carjan@infradead.org\u003e\nCc: Ulrich Drepper \u003cdrepper@redhat.com\u003e\nCc: Andi Kleen \u003cak@muc.de\u003e\nSigned-off-by: Andrew Morton \u003cakpm@osdl.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n" }, { "commit": "34f192c6527f20c47ccec239e7d51a27691b93fc", "tree": "6c80416cf6a170a193f829e414051cc618b15ee3", "parents": [ "2eec9ad91f71a3dbacece5c4fb5adc09fad53a96" ], "author": { "name": "Ingo Molnar", "email": "mingo@elte.hu", "time": "Mon Mar 27 01:16:24 2006 -0800" }, "committer": { "name": "Linus Torvalds", "email": "torvalds@g5.osdl.org", "time": "Mon Mar 27 08:44:49 2006 -0800" }, "message": "[PATCH] lightweight robust futexes: compat\n\n32-bit syscall compatibility support. (This patch also moves all futex\nrelated compat functionality into kernel/futex_compat.c.)\n\nSigned-off-by: Ingo Molnar \u003cmingo@elte.hu\u003e\nSigned-off-by: Thomas Gleixner \u003ctglx@linutronix.de\u003e\nSigned-off-by: Arjan van de Ven \u003carjan@infradead.org\u003e\nAcked-by: Ulrich Drepper \u003cdrepper@redhat.com\u003e\nSigned-off-by: Andrew Morton \u003cakpm@osdl.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n" } ] }