- 28 2月, 2017 2 次提交
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由 Manfred Spraul 提交于
sysv sem has two lock modes: One with per-semaphore locks, one lock mode with a single global lock for the whole array. When switching from the per-semaphore locks to the global lock, all per-semaphore locks must be scanned for ongoing operations. The patch adds a hysteresis for switching from the global lock to the per semaphore locks. This reduces how often the per-semaphore locks must be scanned. Compared to the initial patch, this is a simplified solution: Setting USE_GLOBAL_LOCK_HYSTERESIS to 1 restores the current behavior. In theory, a workload with exactly 10 simple sops and then one complex op now scales a bit worse, but this is pure theory: If there is concurrency, the it won't be exactly 10:1:10:1:10:1:... If there is no concurrency, then there is no need for scalability. Link: http://lkml.kernel.org/r/1476851896-3590-3-git-send-email-manfred@colorfullife.comSigned-off-by: NManfred Spraul <manfred@colorfullife.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: H. Peter Anvin <hpa@zytor.com> Cc: <1vier1@web.de> Cc: kernel test robot <xiaolong.ye@intel.com> Cc: <felixh@informatik.uni-bremen.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Manfred Spraul 提交于
a) The ACQUIRE in spin_lock() applies to the read, not to the store, at least for powerpc. This forces to add a smp_mb() into the fast path. b) The memory barrier provided by spin_unlock_wait() is right now arch dependent. Therefore: Use spin_lock()/spin_unlock() instead of spin_unlock_wait(). Advantage: faster single op semop calls(), observed +8.9% on x86. (the other solution would be arch dependencies in ipc/sem). Disadvantage: slower complex op semop calls, if (and only if) there are no sleeping operations. The next patch adds hysteresis, this further reduces the probability that the slow path is used. Link: http://lkml.kernel.org/r/1476851896-3590-2-git-send-email-manfred@colorfullife.comSigned-off-by: NManfred Spraul <manfred@colorfullife.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: H. Peter Anvin <hpa@zytor.com> Cc: <1vier1@web.de> Cc: kernel test robot <xiaolong.ye@intel.com> Cc: <felixh@informatik.uni-bremen.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 11 1月, 2017 1 次提交
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由 Manfred Spraul 提交于
Based on the syzcaller test case from dvyukov: https://gist.githubusercontent.com/dvyukov/d0e5efefe4d7d6daed829f5c3ca26a40/raw/08d0a261fe3c987bed04fbf267e08ba04bd533ea/gistfile1.txt The slow (i.e.: failure to acquire) syscall exit from semtimedop() incorrectly assumed that the the same lock is acquired as it was at the initial syscall entry. This is wrong: - thread A: single semop semop(), sleeps - thread B: multi semop semop(), sleeps - thread A: woken up by signal/timeout With this sequence, the initial sem_lock() call locks the per-semaphore spinlock, and it is unlocked with sem_unlock(). The call at the syscall return locks the global spinlock. Because locknum is not updated, the following sem_unlock() call unlocks the per-semaphore spinlock, which is actually not locked. The fix is trivial: Use the return value from sem_lock. Fixes: 370b262c ("ipc/sem: avoid idr tree lookup for interrupted semop") Link: http://lkml.kernel.org/r/1482215645-22328-1-git-send-email-manfred@colorfullife.comSigned-off-by: NManfred Spraul <manfred@colorfullife.com> Reported-by: NDmitry Vyukov <dvyukov@google.com> Reported-by: NJohanna Abrahamsson <johanna@mjao.org> Tested-by: NJohanna Abrahamsson <johanna@mjao.org> Acked-by: NDavidlohr Bueso <dave@stgolabs.net> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 15 12月, 2016 7 次提交
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由 Davidlohr Bueso 提交于
We can avoid the idr tree lookup (albeit possibly avoiding idr_find_fast()) when being awoken in EINTR, as the semid will not change in this context while blocked. Use the sma pointer directly and take the sem_lock, then re-check for RMID races. We continue to re-check the queue.status with the lock held such that we can detect situations where we where are dealing with a spurious wakeup but another task that holds the sem_lock updated the queue.status while we were spinning for it. Once we take the lock it obviously won't change again. Being the only caller, get rid of sem_obtain_lock() altogether. Link: http://lkml.kernel.org/r/1478708774-28826-3-git-send-email-dave@stgolabs.netSigned-off-by: NDavidlohr Bueso <dbueso@suse.de> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
Instead of using the reverse goto, we can simplify the flow and make it more language natural by just doing do-while instead. One would hope this is the standard way (or obviously just with a while bucle) that we do wait/wakeup handling in the kernel. The exact same logic is kept, just more indented. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/1478708774-28826-2-git-send-email-dave@stgolabs.netSigned-off-by: NDavidlohr Bueso <dbueso@suse.de> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
... saves some LoC and looks cleaner than re-implementing the calls. Link: http://lkml.kernel.org/r/1474225896-10066-6-git-send-email-dave@stgolabs.netSigned-off-by: NDavidlohr Bueso <dbueso@suse.de> Acked-by: NManfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
The compiler already does this, but make it explicit. This helper is really small and also used in update_queue's main loop, which is O(N^2) scanning. Inline and avoid the function overhead. Link: http://lkml.kernel.org/r/1474225896-10066-5-git-send-email-dave@stgolabs.netSigned-off-by: NDavidlohr Bueso <dbueso@suse.de> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
This is the main workhorse that deals with semop user calls such that the waitforzero or semval update operations, on the set, can complete on not as the sma currently stands. Currently, the set is iterated twice (setting semval, then backwards for the sempid value). Slowpaths, and particularly SEM_UNDO calls, must undo any altered sem when it is detected that the caller must block or has errored-out. With larger sets, there can occur situations where this involves a lot of cycles and can obviously be a suboptimal use of cached resources in shared memory. Ie, discarding CPU caches that are also calling semop and have the sembuf cached (and can complete), while the current lock holder doing the semop will block, error, or does a waitforzero operation. This patch proposes still iterating the set twice, but the first scan is read-only, and we perform the actual updates afterward, once we know that the call will succeed. In order to not suffer from the overhead of dealing with sops that act on the same sem_num, such (rare) cases use perform_atomic_semop_slow(), which is exactly what we have now. Duplicates are detected before grabbing sem_lock, and uses simple a 32/64-bit hash array variable to based on the sem_num we are working on. In addition add some comments to when we expect to the caller to block. [akpm@linux-foundation.org: coding-style fixes] [colin.king@canonical.com: ensure we left shift a ULL rather than a 32 bit integer] Link: http://lkml.kernel.org/r/20161028181129.7311-1-colin.king@canonical.com Link: http://lkml.kernel.org/r/20160921194603.GB21438@linux-80c1.suseSigned-off-by: NDavidlohr Bueso <dbueso@suse.de> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NColin Ian King <colin.king@canonical.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
Our sysv sems have been using the notion of lockless wakeups for a while, ever since commit 0a2b9d4c ("ipc/sem.c: move wake_up_process out of the spinlock section"), in order to reduce the sem_lock hold times. This in-house pending queue can be replaced by wake_q (just like all the rest of ipc now), in that it provides the following advantages: o Simplifies and gets rid of unnecessary code. o We get rid of the IN_WAKEUP complexities. Given that wake_q_add() grabs reference to the task, if awoken due to an unrelated event, between the wake_q_add() and wake_up_q() window, we cannot race with sys_exit and the imminent call to wake_up_process(). o By not spinning IN_WAKEUP, we no longer need to disable preemption. In consequence, the wakeup paths (after schedule(), that is) must acknowledge an external signal/event, as well spurious wakeup occurring during the pending wakeup window. Obviously no changes in semantics that could be visible to the user. The fastpath is _only_ for when we know for sure that we were awoken due to a the waker's successful semop call (queue.status is not -EINTR). On a 48-core Haswell, running the ipcscale 'waitforzero' test, the following is seen with increasing thread counts: v4.8-rc5 v4.8-rc5 semopv2 Hmean sembench-sem-2 574733.00 ( 0.00%) 578322.00 ( 0.62%) Hmean sembench-sem-8 811708.00 ( 0.00%) 824689.00 ( 1.59%) Hmean sembench-sem-12 842448.00 ( 0.00%) 845409.00 ( 0.35%) Hmean sembench-sem-21 933003.00 ( 0.00%) 977748.00 ( 4.80%) Hmean sembench-sem-48 935910.00 ( 0.00%) 1004759.00 ( 7.36%) Hmean sembench-sem-79 937186.00 ( 0.00%) 983976.00 ( 4.99%) Hmean sembench-sem-234 974256.00 ( 0.00%) 1060294.00 ( 8.83%) Hmean sembench-sem-265 975468.00 ( 0.00%) 1016243.00 ( 4.18%) Hmean sembench-sem-296 991280.00 ( 0.00%) 1042659.00 ( 5.18%) Hmean sembench-sem-327 975415.00 ( 0.00%) 1029977.00 ( 5.59%) Hmean sembench-sem-358 1014286.00 ( 0.00%) 1049624.00 ( 3.48%) Hmean sembench-sem-389 972939.00 ( 0.00%) 1043127.00 ( 7.21%) Hmean sembench-sem-420 981909.00 ( 0.00%) 1056747.00 ( 7.62%) Hmean sembench-sem-451 990139.00 ( 0.00%) 1051609.00 ( 6.21%) Hmean sembench-sem-482 965735.00 ( 0.00%) 1040313.00 ( 7.72%) [akpm@linux-foundation.org: coding-style fixes] [sfr@canb.auug.org.au: merge fix for WAKE_Q to DEFINE_WAKE_Q rename] Link: http://lkml.kernel.org/r/20161122210410.5eca9fc2@canb.auug.org.au Link: http://lkml.kernel.org/r/1474225896-10066-3-git-send-email-dave@stgolabs.netSigned-off-by: NDavidlohr Bueso <dbueso@suse.de> Acked-by: NManfred Spraul <manfred@colorfullife.com> Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
ipc/sem: do not call wake_sem_queue_do() prematurely ... as this call should obviously be paired with its _prepare() counterpart. At least whenever possible, as there is no harm in calling it bogusly as we do now in a few places. Immediate error semop(2) paths that are far from ever having the task block can be simplified and avoid a few unnecessary loads on their way out of the call as it is not deeply nested. Link: http://lkml.kernel.org/r/1474225896-10066-2-git-send-email-dave@stgolabs.netSigned-off-by: NDavidlohr Bueso <dbueso@suse.de> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 12 10月, 2016 2 次提交
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由 Nikolay Borisov 提交于
In CONFIG_PREEMPT=n kernel a softlockup was observed while the for loop in exit_sem. Apparently it's possible for the loop to take quite a long time and it doesn't have a scheduling point in it. Since the codes is executing under an rcu read section this may also cause rcu stalls, which in turn block synchronize_rcu operations, which more or less de-stabilises the whole system. Fix this by introducing a cond_resched() at the beginning of the loop. So this patch fixes the following: NMI watchdog: BUG: soft lockup - CPU#10 stuck for 23s! [httpd:18119] CPU: 10 PID: 18119 Comm: httpd Tainted: G O 4.4.20-clouder2 #6 Hardware name: Supermicro X10DRi/X10DRi, BIOS 1.1 04/14/2015 task: ffff88348d695280 ti: ffff881c95550000 task.ti: ffff881c95550000 RIP: 0010:[<ffffffff81614bc7>] [<ffffffff81614bc7>] _raw_spin_lock+0x17/0x30 RSP: 0018:ffff881c95553e40 EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffff883161b1eea8 RCX: 000000000000000d RDX: 0000000000000001 RSI: 000000000000000e RDI: ffff883161b1eea4 RBP: ffff881c95553ea0 R08: ffff881c95553e68 R09: ffff883fef376f88 R10: ffff881fffb58c20 R11: ffffea0072556600 R12: ffff883161b1eea0 R13: ffff88348d695280 R14: ffff883dec427000 R15: ffff8831621672a0 FS: 0000000000000000(0000) GS:ffff881fffb40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f3b3723e020 CR3: 0000000001c0a000 CR4: 00000000001406e0 Call Trace: ? exit_sem+0x7c/0x280 do_exit+0x338/0xb40 do_group_exit+0x43/0xd0 SyS_exit_group+0x14/0x20 entry_SYSCALL_64_fastpath+0x16/0x6e Link: http://lkml.kernel.org/r/1475154992-6363-1-git-send-email-kernel@kyup.comSigned-off-by: NNikolay Borisov <kernel@kyup.com> Cc: Herton R. Krzesinski <herton@redhat.com> Cc: Fabian Frederick <fabf@skynet.be> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Manfred Spraul 提交于
Commit 6d07b68c ("ipc/sem.c: optimize sem_lock()") introduced a race: sem_lock has a fast path that allows parallel simple operations. There are two reasons why a simple operation cannot run in parallel: - a non-simple operations is ongoing (sma->sem_perm.lock held) - a complex operation is sleeping (sma->complex_count != 0) As both facts are stored independently, a thread can bypass the current checks by sleeping in the right positions. See below for more details (or kernel bugzilla 105651). The patch fixes that by creating one variable (complex_mode) that tracks both reasons why parallel operations are not possible. The patch also updates stale documentation regarding the locking. With regards to stable kernels: The patch is required for all kernels that include the commit 6d07b68c ("ipc/sem.c: optimize sem_lock()") (3.10?) The alternative is to revert the patch that introduced the race. The patch is safe for backporting, i.e. it makes no assumptions about memory barriers in spin_unlock_wait(). Background: Here is the race of the current implementation: Thread A: (simple op) - does the first "sma->complex_count == 0" test Thread B: (complex op) - does sem_lock(): This includes an array scan. But the scan can't find Thread A, because Thread A does not own sem->lock yet. - the thread does the operation, increases complex_count, drops sem_lock, sleeps Thread A: - spin_lock(&sem->lock), spin_is_locked(sma->sem_perm.lock) - sleeps before the complex_count test Thread C: (complex op) - does sem_lock (no array scan, complex_count==1) - wakes up Thread B. - decrements complex_count Thread A: - does the complex_count test Bug: Now both thread A and thread C operate on the same array, without any synchronization. Fixes: 6d07b68c ("ipc/sem.c: optimize sem_lock()") Link: http://lkml.kernel.org/r/1469123695-5661-1-git-send-email-manfred@colorfullife.com Reported-by: <felixh@informatik.uni-bremen.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: <1vier1@web.de> Cc: <stable@vger.kernel.org> [3.10+] Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 03 8月, 2016 1 次提交
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由 Fabian Frederick 提交于
Commit 53dad6d3 ("ipc: fix race with LSMs") updated ipc_rcu_putref() to receive rcu freeing function but used generic ipc_rcu_free() instead of msg_rcu_free() which does security cleaning. Running LTP msgsnd06 with kmemleak gives the following: cat /sys/kernel/debug/kmemleak unreferenced object 0xffff88003c0a11f8 (size 8): comm "msgsnd06", pid 1645, jiffies 4294672526 (age 6.549s) hex dump (first 8 bytes): 1b 00 00 00 01 00 00 00 ........ backtrace: kmemleak_alloc+0x23/0x40 kmem_cache_alloc_trace+0xe1/0x180 selinux_msg_queue_alloc_security+0x3f/0xd0 security_msg_queue_alloc+0x2e/0x40 newque+0x4e/0x150 ipcget+0x159/0x1b0 SyS_msgget+0x39/0x40 entry_SYSCALL_64_fastpath+0x13/0x8f Manfred Spraul suggested to fix sem.c as well and Davidlohr Bueso to only use ipc_rcu_free in case of security allocation failure in newary() Fixes: 53dad6d3 ("ipc: fix race with LSMs") Link: http://lkml.kernel.org/r/1470083552-22966-1-git-send-email-fabf@skynet.beSigned-off-by: NFabian Frederick <fabf@skynet.be> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: <stable@vger.kernel.org> [3.12+] Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 14 6月, 2016 2 次提交
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由 Peter Zijlstra 提交于
With the modified semantics of spin_unlock_wait() a number of explicit barriers can be removed. Also update the comment for the do_exit() usecase, as that was somewhat stale/obscure. Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: NIngo Molnar <mingo@kernel.org>
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由 Peter Zijlstra 提交于
Introduce smp_acquire__after_ctrl_dep(), this construct is not uncommon, but the lack of this barrier is. Use it to better express smp_rmb() uses in WRITE_ONCE(), the IPC semaphore code and the qspinlock code. Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: NIngo Molnar <mingo@kernel.org>
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- 23 3月, 2016 1 次提交
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由 Davidlohr Bueso 提交于
As indicated by bug#112271, Linux sets the sempid value upon semctl, and not only for semop calls. However, within semctl we only do this for SETVAL, leaving SETALL without updating the field, and therefore rather inconsistent behavior when compared to other Unices. There is really no documentation regarding this and therefore users should not make assumptions. With this patch, along with updating semctl.2 manpages, this scenario should become less ambiguous As such, set sempid on SETALL cmd. Also update some in-code documentation, specifying where the sempid is set. Passes ltp and custom testcase where a child (fork) does SETALL to the set. Signed-off-by: NDavidlohr Bueso <dbueso@suse.de> Reported-by: NPhilip Semanchuk <linux_kernel.20.ick@spamgourmet.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Herton R. Krzesinski <herton@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 23 1月, 2016 1 次提交
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由 Tetsuo Handa 提交于
There are many locations that do if (memory_was_allocated_by_vmalloc) vfree(ptr); else kfree(ptr); but kvfree() can handle both kmalloc()ed memory and vmalloc()ed memory using is_vmalloc_addr(). Unless callers have special reasons, we can replace this branch with kvfree(). Please check and reply if you found problems. Signed-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: NMichal Hocko <mhocko@suse.com> Acked-by: NJan Kara <jack@suse.com> Acked-by: NRussell King <rmk+kernel@arm.linux.org.uk> Reviewed-by: NAndreas Dilger <andreas.dilger@intel.com> Acked-by: N"Rafael J. Wysocki" <rjw@rjwysocki.net> Acked-by: NDavid Rientjes <rientjes@google.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Oleg Drokin <oleg.drokin@intel.com> Cc: Boris Petkov <bp@suse.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 15 8月, 2015 3 次提交
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由 Manfred Spraul 提交于
sem_lock() did not properly pair memory barriers: !spin_is_locked() and spin_unlock_wait() are both only control barriers. The code needs an acquire barrier, otherwise the cpu might perform read operations before the lock test. As no primitive exists inside <include/spinlock.h> and since it seems noone wants another primitive, the code creates a local primitive within ipc/sem.c. With regards to -stable: The change of sem_wait_array() is a bugfix, the change to sem_lock() is a nop (just a preprocessor redefinition to improve the readability). The bugfix is necessary for all kernels that use sem_wait_array() (i.e.: starting from 3.10). Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Reported-by: NOleg Nesterov <oleg@redhat.com> Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Kirill Tkhai <ktkhai@parallels.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: <stable@vger.kernel.org> [3.10+] Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Herton R. Krzesinski 提交于
After we acquire the sma->sem_perm lock in exit_sem(), we are protected against a racing IPC_RMID operation. Also at that point, we are the last user of sem_undo_list. Therefore it isn't required that we acquire or use ulp->lock. Signed-off-by: NHerton R. Krzesinski <herton@redhat.com> Acked-by: NManfred Spraul <manfred@colorfullife.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Rafael Aquini <aquini@redhat.com> CC: Aristeu Rozanski <aris@redhat.com> Cc: David Jeffery <djeffery@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Herton R. Krzesinski 提交于
The current semaphore code allows a potential use after free: in exit_sem we may free the task's sem_undo_list while there is still another task looping through the same semaphore set and cleaning the sem_undo list at freeary function (the task called IPC_RMID for the same semaphore set). For example, with a test program [1] running which keeps forking a lot of processes (which then do a semop call with SEM_UNDO flag), and with the parent right after removing the semaphore set with IPC_RMID, and a kernel built with CONFIG_SLAB, CONFIG_SLAB_DEBUG and CONFIG_DEBUG_SPINLOCK, you can easily see something like the following in the kernel log: Slab corruption (Not tainted): kmalloc-64 start=ffff88003b45c1c0, len=64 000: 6b 6b 6b 6b 6b 6b 6b 6b 00 6b 6b 6b 6b 6b 6b 6b kkkkkkkk.kkkkkkk 010: ff ff ff ff 6b 6b 6b 6b ff ff ff ff ff ff ff ff ....kkkk........ Prev obj: start=ffff88003b45c180, len=64 000: 00 00 00 00 ad 4e ad de ff ff ff ff 5a 5a 5a 5a .....N......ZZZZ 010: ff ff ff ff ff ff ff ff c0 fb 01 37 00 88 ff ff ...........7.... Next obj: start=ffff88003b45c200, len=64 000: 00 00 00 00 ad 4e ad de ff ff ff ff 5a 5a 5a 5a .....N......ZZZZ 010: ff ff ff ff ff ff ff ff 68 29 a7 3c 00 88 ff ff ........h).<.... BUG: spinlock wrong CPU on CPU#2, test/18028 general protection fault: 0000 [#1] SMP Modules linked in: 8021q mrp garp stp llc nf_conntrack_ipv4 nf_defrag_ipv4 ip6t_REJECT nf_reject_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables binfmt_misc ppdev input_leds joydev parport_pc parport floppy serio_raw virtio_balloon virtio_rng virtio_console virtio_net iosf_mbi crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcspkr qxl ttm drm_kms_helper drm snd_hda_codec_generic i2c_piix4 snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd soundcore crc32c_intel virtio_pci virtio_ring virtio pata_acpi ata_generic [last unloaded: speedstep_lib] CPU: 2 PID: 18028 Comm: test Not tainted 4.2.0-rc5+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150318_183358- 04/01/2014 RIP: spin_dump+0x53/0xc0 Call Trace: spin_bug+0x30/0x40 do_raw_spin_unlock+0x71/0xa0 _raw_spin_unlock+0xe/0x10 freeary+0x82/0x2a0 ? _raw_spin_lock+0xe/0x10 semctl_down.clone.0+0xce/0x160 ? __do_page_fault+0x19a/0x430 ? __audit_syscall_entry+0xa8/0x100 SyS_semctl+0x236/0x2c0 ? syscall_trace_leave+0xde/0x130 entry_SYSCALL_64_fastpath+0x12/0x71 Code: 8b 80 88 03 00 00 48 8d 88 60 05 00 00 48 c7 c7 a0 2c a4 81 31 c0 65 8b 15 eb 40 f3 7e e8 08 31 68 00 4d 85 e4 44 8b 4b 08 74 5e <45> 8b 84 24 88 03 00 00 49 8d 8c 24 60 05 00 00 8b 53 04 48 89 RIP [<ffffffff810d6053>] spin_dump+0x53/0xc0 RSP <ffff88003750fd68> ---[ end trace 783ebb76612867a0 ]--- NMI watchdog: BUG: soft lockup - CPU#3 stuck for 22s! [test:18053] Modules linked in: 8021q mrp garp stp llc nf_conntrack_ipv4 nf_defrag_ipv4 ip6t_REJECT nf_reject_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables binfmt_misc ppdev input_leds joydev parport_pc parport floppy serio_raw virtio_balloon virtio_rng virtio_console virtio_net iosf_mbi crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcspkr qxl ttm drm_kms_helper drm snd_hda_codec_generic i2c_piix4 snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd soundcore crc32c_intel virtio_pci virtio_ring virtio pata_acpi ata_generic [last unloaded: speedstep_lib] CPU: 3 PID: 18053 Comm: test Tainted: G D 4.2.0-rc5+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150318_183358- 04/01/2014 RIP: native_read_tsc+0x0/0x20 Call Trace: ? delay_tsc+0x40/0x70 __delay+0xf/0x20 do_raw_spin_lock+0x96/0x140 _raw_spin_lock+0xe/0x10 sem_lock_and_putref+0x11/0x70 SYSC_semtimedop+0x7bf/0x960 ? handle_mm_fault+0xbf6/0x1880 ? dequeue_task_fair+0x79/0x4a0 ? __do_page_fault+0x19a/0x430 ? kfree_debugcheck+0x16/0x40 ? __do_page_fault+0x19a/0x430 ? __audit_syscall_entry+0xa8/0x100 ? do_audit_syscall_entry+0x66/0x70 ? syscall_trace_enter_phase1+0x139/0x160 SyS_semtimedop+0xe/0x10 SyS_semop+0x10/0x20 entry_SYSCALL_64_fastpath+0x12/0x71 Code: 47 10 83 e8 01 85 c0 89 47 10 75 08 65 48 89 3d 1f 74 ff 7e c9 c3 0f 1f 44 00 00 55 48 89 e5 e8 87 17 04 00 66 90 c9 c3 0f 1f 00 <55> 48 89 e5 0f 31 89 c1 48 89 d0 48 c1 e0 20 89 c9 48 09 c8 c9 Kernel panic - not syncing: softlockup: hung tasks I wasn't able to trigger any badness on a recent kernel without the proper config debugs enabled, however I have softlockup reports on some kernel versions, in the semaphore code, which are similar as above (the scenario is seen on some servers running IBM DB2 which uses semaphore syscalls). The patch here fixes the race against freeary, by acquiring or waiting on the sem_undo_list lock as necessary (exit_sem can race with freeary, while freeary sets un->semid to -1 and removes the same sem_undo from list_proc or when it removes the last sem_undo). After the patch I'm unable to reproduce the problem using the test case [1]. [1] Test case used below: #include <stdio.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> #include <sys/wait.h> #include <stdlib.h> #include <time.h> #include <unistd.h> #include <errno.h> #define NSEM 1 #define NSET 5 int sid[NSET]; void thread() { struct sembuf op; int s; uid_t pid = getuid(); s = rand() % NSET; op.sem_num = pid % NSEM; op.sem_op = 1; op.sem_flg = SEM_UNDO; semop(sid[s], &op, 1); exit(EXIT_SUCCESS); } void create_set() { int i, j; pid_t p; union { int val; struct semid_ds *buf; unsigned short int *array; struct seminfo *__buf; } un; /* Create and initialize semaphore set */ for (i = 0; i < NSET; i++) { sid[i] = semget(IPC_PRIVATE , NSEM, 0644 | IPC_CREAT); if (sid[i] < 0) { perror("semget"); exit(EXIT_FAILURE); } } un.val = 0; for (i = 0; i < NSET; i++) { for (j = 0; j < NSEM; j++) { if (semctl(sid[i], j, SETVAL, un) < 0) perror("semctl"); } } /* Launch threads that operate on semaphore set */ for (i = 0; i < NSEM * NSET * NSET; i++) { p = fork(); if (p < 0) perror("fork"); if (p == 0) thread(); } /* Free semaphore set */ for (i = 0; i < NSET; i++) { if (semctl(sid[i], NSEM, IPC_RMID)) perror("IPC_RMID"); } /* Wait for forked processes to exit */ while (wait(NULL)) { if (errno == ECHILD) break; }; } int main(int argc, char **argv) { pid_t p; srand(time(NULL)); while (1) { p = fork(); if (p < 0) { perror("fork"); exit(EXIT_FAILURE); } if (p == 0) { create_set(); goto end; } /* Wait for forked processes to exit */ while (wait(NULL)) { if (errno == ECHILD) break; }; } end: return 0; } [akpm@linux-foundation.org: use normal comment layout] Signed-off-by: NHerton R. Krzesinski <herton@redhat.com> Acked-by: NManfred Spraul <manfred@colorfullife.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Rafael Aquini <aquini@redhat.com> CC: Aristeu Rozanski <aris@redhat.com> Cc: David Jeffery <djeffery@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 01 7月, 2015 1 次提交
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由 Davidlohr Bueso 提交于
... to ipc_obtain_object_idr, which is more meaningful and makes the code slightly easier to follow. Signed-off-by: NDavidlohr Bueso <dbueso@suse.de> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 16 4月, 2015 1 次提交
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由 Joe Perches 提交于
The seq_printf return value, because it's frequently misused, will eventually be converted to void. See: commit 1f33c41c ("seq_file: Rename seq_overflow() to seq_has_overflowed() and make public") Signed-off-by: NJoe Perches <joe@perches.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 18 2月, 2015 1 次提交
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由 Davidlohr Bueso 提交于
Call __set_current_state() instead of assigning the new state directly. These interfaces also aid CONFIG_DEBUG_ATOMIC_SLEEP environments, keeping track of who changed the state. Signed-off-by: NDavidlohr Bueso <dbueso@suse.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 14 12月, 2014 1 次提交
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由 Manfred Spraul 提交于
When I fixed bugs in the sem_lock() logic, I was more conservative than necessary. Therefore it is safe to replace the smp_mb() with smp_rmb(). And: With smp_rmb(), semop() syscalls are up to 10% faster. The race we must protect against is: sem->lock is free sma->complex_count = 0 sma->sem_perm.lock held by thread B thread A: A: spin_lock(&sem->lock) B: sma->complex_count++; (now 1) B: spin_unlock(&sma->sem_perm.lock); A: spin_is_locked(&sma->sem_perm.lock); A: XXXXX memory barrier A: if (sma->complex_count == 0) Thread A must read the increased complex_count value, i.e. the read must not be reordered with the read of sem_perm.lock done by spin_is_locked(). Since it's about ordering of reads, smp_rmb() is sufficient. [akpm@linux-foundation.org: update sem_lock() comment, from Davidlohr] Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Reviewed-by: NDavidlohr Bueso <dave@stgolabs.net> Acked-by: NRafael Aquini <aquini@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 04 12月, 2014 1 次提交
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由 Manfred Spraul 提交于
ipc_addid() makes a new ipc identifier visible to everyone. New objects start as locked, so that the caller can complete the initialization after the call. Within struct sem_array, at least sma->sem_base and sma->sem_nsems are accessed without any locks, therefore this approach doesn't work. Thus: Move the ipc_addid() to the end of the initialization. Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Reported-by: NRik van Riel <riel@redhat.com> Acked-by: NRik van Riel <riel@redhat.com> Acked-by: NDavidlohr Bueso <dave@stgolabs.net> Acked-by: NRafael Aquini <aquini@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 07 6月, 2014 9 次提交
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由 Manfred Spraul 提交于
The actual Linux implementation for semctl(GETNCNT) and semctl(GETZCNT) always (since 0.99.10) reported a thread as sleeping on all semaphores that are listed in the semop() call. The documented behavior (both in the Linux man page and in the Single Unix Specification) is that a task should be reported on exactly one semaphore: The semaphore that caused the thread to got to sleep. This patch adds a pr_info_once() that is triggered if a thread hits the relevant case. The code triggers slightly too often, otherwise it would be necessary to replicate the old code. As there are no known users of GETNCNT or GETZCNT, this is done to prevent unnecessary bloat. The task that triggered is reported with name (tsk->comm) and pid. Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Acked-by: NDavidlohr Bueso <davidlohr@hp.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Joe Perches <joe@perches.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Manfred Spraul 提交于
SUSv4 clearly defines how semncnt and semzcnt must be calculated: A task waits on exactly one semaphore: The semaphore from the first operation in the sop array that cannot proceed. The Linux implementation never followed the standard, it tried to count all semaphores that might be the reason why a task sleeps. This patch fixes that. Note: a) The implementation assumes that GETNCNT and GETZCNT are rare operations, therefore the code counts them only on demand. (If they wouldn't be rare, then the non-compliance would have been found earlier) b) compared to the initial version of the patch, the BUG_ONs were removed and it was clarified that the new behavior conforms to SUS. Back-compatibility concerns: Manfred: : - there is no application in Fedora that uses GETNCNT or GETZCNT. : : - application that use only single-sop semop() are also safe, the : difference only affects complex apps. : : - portable application are also safe, the new behavior is standard : compliant. : : But that's it. The old behavior existed in Linux from 0.99.something : until now. Michael: : * These operations seem to be very little used. Grepping the public : source that is contained Fedora 20 source DVD, there appear to be no : uses. Of course, this says nothing about uses in private / : non-mainstream FOSS code, but it seems likely that the same pattern : is followed there. : : * The existing behavior is hard enough to understand that I suspect : that no one understood it well enough to rely on it anyway : (especially as that behavior contradicted both man page and POSIX). : : So, there's a chance of breakage, but I estimate that it's minute. Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Manfred Spraul 提交于
Preparation for the next patch: In the slow-path of perform_atomic_semop(), store a pointer to the operation that caused the operation to block. Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Manfred Spraul 提交于
Right now, perform_atomic_semop gets the content of sem_queue as individual fields. Changes that, instead pass a pointer to sem_queue. This is a preparation for the next patch: it uses sem_queue to store the reason why a task must sleep. Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Manfred Spraul 提交于
count_semzcnt and count_semncnt are more of less identical. The patch creates a single function that either counts the number of tasks waiting for zero or waiting due to a decrease operation. Compared to the initial version, the BUG_ONs were removed. Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Manfred Spraul 提交于
GETZCNT is supposed to return the number of threads that wait until a semaphore value becomes 0. The current implementation overlooks complex operations that contain both wait-for-zero operation and operations that alter at least one semaphore. The patch fixes that. It's intentionally copy&paste, this will be cleaned up in the next patch. Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Paul McQuade 提交于
trailing whitespace Signed-off-by: NPaul McQuade <paulmcquad@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Paul McQuade 提交于
Use #include <linux/uaccess.h> instead of <asm/uaccess.h> Use #include <linux/types.h> instead of <asm/types.h> Signed-off-by: NPaul McQuade <paulmcquad@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Mathias Krause 提交于
There is no need to recreate the very same ipc_ops structure on every kernel entry for msgget/semget/shmget. Just declare it static and be done with it. While at it, constify it as we don't modify the structure at runtime. Found in the PaX patch, written by the PaX Team. Signed-off-by: NMathias Krause <minipli@googlemail.com> Cc: PaX Team <pageexec@freemail.hu> Cc: Davidlohr Bueso <davidlohr@hp.com> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 28 1月, 2014 6 次提交
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由 Davidlohr Bueso 提交于
Deal with checkpatch messages: WARNING: braces {} are not necessary for single statement blocks Signed-off-by: NDavidlohr Bueso <davidlohr@hp.com> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Cc: Rik van Riel <riel@redhat.com> Acked-by: NManfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
IPC commenting style is all over the place, *specially* in util.c. This patch orders things a bit. Signed-off-by: NDavidlohr Bueso <davidlohr@hp.com> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Cc: Rik van Riel <riel@redhat.com> Acked-by: NManfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Manfred Spraul 提交于
The ipc code does not adhere the typical linux coding style. This patch fixes lots of simple whitespace errors. - mostly autogenerated by scripts/checkpatch.pl -f --fix \ --types=pointer_location,spacing,space_before_tab - one manual fixup (keep structure members tab-aligned) - removal of additional space_before_tab that were not found by --fix Tested with some of my msg and sem test apps. Andrew: Could you include it in -mm and move it towards Linus' tree? Signed-off-by: NManfred Spraul <manfred@colorfullife.com> Suggested-by: NLi Bin <huawei.libin@huawei.com> Cc: Joe Perches <joe@perches.com> Acked-by: NRafael Aquini <aquini@redhat.com> Cc: Davidlohr Bueso <davidlohr@hp.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Rafael Aquini 提交于
struct kern_ipc_perm.deleted is meant to be used as a boolean toggle, and the changes introduced by this patch are just to make the case explicit. Signed-off-by: NRafael Aquini <aquini@redhat.com> Reviewed-by: NRik van Riel <riel@redhat.com> Cc: Greg Thelen <gthelen@google.com> Acked-by: NDavidlohr Bueso <davidlohr@hp.com> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Rafael Aquini 提交于
After the locking semantics for the SysV IPC API got improved, a couple of IPC_RMID race windows were opened because we ended up dropping the 'kern_ipc_perm.deleted' check performed way down in ipc_lock(). The spotted races got sorted out by re-introducing the old test within the racy critical sections. This patch introduces ipc_valid_object() to consolidate the way we cope with IPC_RMID races by using the same abstraction across the API implementation. Signed-off-by: NRafael Aquini <aquini@redhat.com> Acked-by: NRik van Riel <riel@redhat.com> Acked-by: NGreg Thelen <gthelen@google.com> Reviewed-by: NDavidlohr Bueso <davidlohr@hp.com> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Petr Mladek 提交于
When trying to understand semop code, I found a small mistake in the check for semadj (undo) value overflow. The new undo value is not stored immediately and next potential checks are done against the old value. The failing scenario is not much practical. One semop call has to do more operations on the same semaphore. Also semval and semadj must have different values, so there has to be some operations without SEM_UNDO flag. For example: struct sembuf depositor_op[1]; struct sembuf collector_op[2]; depositor_op[0].sem_num = 0; depositor_op[0].sem_op = 20000; depositor_op[0].sem_flg = 0; collector_op[0].sem_num = 0; collector_op[0].sem_op = -10000; collector_op[0].sem_flg = SEM_UNDO; collector_op[1].sem_num = 0; collector_op[1].sem_op = -10000; collector_op[1].sem_flg = SEM_UNDO; if (semop(semid, depositor_op, 1) == -1) { perror("Failed to do 1st deposit"); return 1; } if (semop(semid, collector_op, 2) == -1) { perror("Failed to do 1st collect"); return 1; } if (semop(semid, depositor_op, 1) == -1) { perror("Failed to do 2nd deposit"); return 1; } if (semop(semid, collector_op, 2) == -1) { perror("Failed to do 2nd collect"); return 1; } return 0; It passes without error now but the semadj value has overflown in the 2nd collector operation. [akpm@linux-foundation.org: restore lessened scope of local `undo'] [davidlohr@hp.com: correct header comment for perform_atomic_semop] Signed-off-by: NPetr Mladek <pmladek@suse.cz> Acked-by: NDavidlohr Bueso <davidlohr@hp.com> Acked-by: NManfred Spraul <manfred@colorfullife.com> Cc: Jiri Kosina <jkosina@suse.cz> Signed-off-by: NDavidlohr Bueso <davidlohr@hp.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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