user/sven/linux.git/kernel/locking, branch v4.4.194

locking/lockdep: Hide unused 'class' variable

2019-08-04T07:34:59Z

[ Upstream commit 68037aa78208f34bda4e5cd76c357f718b838cbb ] The usage is now hidden in an #ifdef, so we need to move the variable itself in there as well to avoid this warning: kernel/locking/lockdep_proc.c:203:21: error: unused variable 'class' [-Werror,-Wunused-variable] Signed-off-by: Arnd Bergmann Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Bart Van Assche Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Qian Cai Cc: Thomas Gleixner Cc: Waiman Long Cc: Will Deacon Cc: Will Deacon Cc: Yuyang Du Cc: frederic@kernel.org Fixes: 68d41d8c94a3 ("locking/lockdep: Fix lock used or unused stats error") Link: https://lkml.kernel.org/r/20190715092809.736834-1-arnd@arndb.de Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

locking/lockdep: Fix lock used or unused stats error

2019-08-04T07:34:59Z

[ Upstream commit 68d41d8c94a31dfb8233ab90b9baf41a2ed2da68 ] The stats variable nr_unused_locks is incremented every time a new lock class is register and decremented when the lock is first used in __lock_acquire(). And after all, it is shown and checked in lockdep_stats. However, under configurations that either CONFIG_TRACE_IRQFLAGS or CONFIG_PROVE_LOCKING is not defined: The commit: 091806515124b20 ("locking/lockdep: Consolidate lock usage bit initialization") missed marking the LOCK_USED flag at IRQ usage initialization because as mark_usage() is not called. And the commit: 886532aee3cd42d ("locking/lockdep: Move mark_lock() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING") further made mark_lock() not defined such that the LOCK_USED cannot be marked at all when the lock is first acquired. As a result, we fix this by not showing and checking the stats under such configurations for lockdep_stats. Reported-by: Qian Cai Signed-off-by: Yuyang Du Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Cc: arnd@arndb.de Cc: frederic@kernel.org Link: https://lkml.kernel.org/r/20190709101522.9117-1-duyuyang@gmail.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

locking/lockdep: Fix merging of hlocks with non-zero references

2019-08-04T07:34:44Z

[ Upstream commit d9349850e188b8b59e5322fda17ff389a1c0cd7d ] The sequence static DEFINE_WW_CLASS(test_ww_class); struct ww_acquire_ctx ww_ctx; struct ww_mutex ww_lock_a; struct ww_mutex ww_lock_b; struct ww_mutex ww_lock_c; struct mutex lock_c; ww_acquire_init(&ww_ctx, &test_ww_class); ww_mutex_init(&ww_lock_a, &test_ww_class); ww_mutex_init(&ww_lock_b, &test_ww_class); ww_mutex_init(&ww_lock_c, &test_ww_class); mutex_init(&lock_c); ww_mutex_lock(&ww_lock_a, &ww_ctx); mutex_lock(&lock_c); ww_mutex_lock(&ww_lock_b, &ww_ctx); ww_mutex_lock(&ww_lock_c, &ww_ctx); mutex_unlock(&lock_c); (*) ww_mutex_unlock(&ww_lock_c); ww_mutex_unlock(&ww_lock_b); ww_mutex_unlock(&ww_lock_a); ww_acquire_fini(&ww_ctx); (**) will trigger the following error in __lock_release() when calling mutex_release() at **: DEBUG_LOCKS_WARN_ON(depth <= 0) The problem is that the hlock merging happening at * updates the references for test_ww_class incorrectly to 3 whereas it should've updated it to 4 (representing all the instances for ww_ctx and ww_lock_[abc]). Fix this by updating the references during merging correctly taking into account that we can have non-zero references (both for the hlock that we merge into another hlock or for the hlock we are merging into). Signed-off-by: Imre Deak Signed-off-by: Peter Zijlstra (Intel) Cc: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Link: https://lkml.kernel.org/r/20190524201509.9199-2-imre.deak@intel.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

Revert "locking/lockdep: Add debug_locks check in __lock_downgrade()"

2019-04-27T07:34:02Z

This reverts commit 4aada79c6793c59e484b69fd4ed591396e2d4b39 which was commit 71492580571467fb7177aade19c18ce7486267f5 upstream. Tetsuo rightly points out that the backport here is incorrect, as it touches the __lock_set_class function instead of the intended __lock_downgrade function. Reported-by: Tetsuo Handa Cc: Waiman Long Cc: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Cc: Ingo Molnar Cc: Sasha Levin Signed-off-by: Greg Kroah-Hartman

locking/lockdep: Add debug_locks check in __lock_downgrade()

2019-04-03T04:23:16Z

commit 71492580571467fb7177aade19c18ce7486267f5 upstream. Tetsuo Handa had reported he saw an incorrect "downgrading a read lock" warning right after a previous lockdep warning. It is likely that the previous warning turned off lock debugging causing the lockdep to have inconsistency states leading to the lock downgrade warning. Fix that by add a check for debug_locks at the beginning of __lock_downgrade(). Debugged-by: Tetsuo Handa Reported-by: Tetsuo Handa Reported-by: syzbot+53383ae265fb161ef488@syzkaller.appspotmail.com Signed-off-by: Waiman Long Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Link: https://lkml.kernel.org/r/1547093005-26085-1-git-send-email-longman@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

futex,rt_mutex: Restructure rt_mutex_finish_proxy_lock()

2019-03-23T07:44:28Z

commit 38d589f2fd08f1296aea3ce62bebd185125c6d81 upstream. With the ultimate goal of keeping rt_mutex wait_list and futex_q waiters consistent it's necessary to split 'rt_mutex_futex_lock()' into finer parts, such that only the actual blocking can be done without hb->lock held. Split split_mutex_finish_proxy_lock() into two parts, one that does the blocking and one that does remove_waiter() when the lock acquire failed. When the rtmutex was acquired successfully the waiter can be removed in the acquisiton path safely, since there is no concurrency on the lock owner. This means that, except for futex_lock_pi(), all wait_list modifications are done with both hb->lock and wait_lock held. [bigeasy@linutronix.de: fix for futex_requeue_pi_signal_restart] Signed-off-by: Peter Zijlstra (Intel) Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170322104152.001659630@infradead.org Signed-off-by: Thomas Gleixner Signed-off-by: Zubin Mithra Signed-off-by: Greg Kroah-Hartman

locking/lockdep: Fix debug_locks off performance problem

2018-11-21T08:27:31Z

[ Upstream commit 9506a7425b094d2f1d9c877ed5a78f416669269b ] It was found that when debug_locks was turned off because of a problem found by the lockdep code, the system performance could drop quite significantly when the lock_stat code was also configured into the kernel. For instance, parallel kernel build time on a 4-socket x86-64 server nearly doubled. Further analysis into the cause of the slowdown traced back to the frequent call to debug_locks_off() from the __lock_acquired() function probably due to some inconsistent lockdep states with debug_locks off. The debug_locks_off() function did an unconditional atomic xchg to write a 0 value into debug_locks which had already been set to 0. This led to severe cacheline contention in the cacheline that held debug_locks. As debug_locks is being referenced in quite a few different places in the kernel, this greatly slow down the system performance. To prevent that trashing of debug_locks cacheline, lock_acquired() and lock_contended() now checks the state of debug_locks before proceeding. The debug_locks_off() function is also modified to check debug_locks before calling __debug_locks_off(). Signed-off-by: Waiman Long Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Link: http://lkml.kernel.org/r/1539913518-15598-1-git-send-email-longman@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

locking/osq_lock: Fix osq_lock queue corruption

2018-09-19T20:48:56Z

commit 50972fe78f24f1cd0b9d7bbf1f87d2be9e4f412e upstream. Fix ordering of link creation between node->prev and prev->next in osq_lock(). A case in which the status of optimistic spin queue is CPU6->CPU2 in which CPU6 has acquired the lock. tail v ,-. <- ,-. |6| |2| `-' -> `-' At this point if CPU0 comes in to acquire osq_lock, it will update the tail count. CPU2 CPU0 ---------------------------------- tail v ,-. <- ,-. ,-. |6| |2| |0| `-' -> `-' `-' After tail count update if CPU2 starts to unqueue itself from optimistic spin queue, it will find an updated tail count with CPU0 and update CPU2 node->next to NULL in osq_wait_next(). unqueue-A tail v ,-. <- ,-. ,-. |6| |2| |0| `-' `-' `-' unqueue-B ->tail != curr && !node->next If reordering of following stores happen then prev->next where prev being CPU2 would be updated to point to CPU0 node: tail v ,-. <- ,-. ,-. |6| |2| |0| `-' `-' -> `-' osq_wait_next() node->next <- 0 xchg(node->next, NULL) tail v ,-. <- ,-. ,-. |6| |2| |0| `-' `-' `-' unqueue-C At this point if next instruction WRITE_ONCE(next->prev, prev); in CPU2 path is committed before the update of CPU0 node->prev = prev then CPU0 node->prev will point to CPU6 node. tail v----------. v ,-. <- ,-. ,-. |6| |2| |0| `-' `-' `-' `----------^ At this point if CPU0 path's node->prev = prev is committed resulting in change of CPU0 prev back to CPU2 node. CPU2 node->next is NULL currently, tail v ,-. <- ,-. <- ,-. |6| |2| |0| `-' `-' `-' `----------^ so if CPU0 gets into unqueue path of osq_lock it will keep spinning in infinite loop as condition prev->next == node will never be true. Signed-off-by: Prateek Sood [ Added pictures, rewrote comments. ] Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: sramana@codeaurora.org Link: http://lkml.kernel.org/r/1500040076-27626-1-git-send-email-prsood@codeaurora.org Signed-off-by: Ingo Molnar Signed-off-by: Amit Pundir Signed-off-by: Greg Kroah-Hartman

locking/rwsem-xadd: Fix missed wakeup due to reordering of load

2018-09-19T20:48:56Z

commit 9c29c31830a4eca724e137a9339137204bbb31be upstream. If a spinner is present, there is a chance that the load of rwsem_has_spinner() in rwsem_wake() can be reordered with respect to decrement of rwsem count in __up_write() leading to wakeup being missed: spinning writer up_write caller --------------- ----------------------- [S] osq_unlock() [L] osq spin_lock(wait_lock) sem->count=0xFFFFFFFF00000001 +0xFFFFFFFF00000000 count=sem->count MB sem->count=0xFFFFFFFE00000001 -0xFFFFFFFF00000001 spin_trylock(wait_lock) return rwsem_try_write_lock(count) spin_unlock(wait_lock) schedule() Reordering of atomic_long_sub_return_release() in __up_write() and rwsem_has_spinner() in rwsem_wake() can cause missing of wakeup in up_write() context. In spinning writer, sem->count and local variable count is 0XFFFFFFFE00000001. It would result in rwsem_try_write_lock() failing to acquire rwsem and spinning writer going to sleep in rwsem_down_write_failed(). The smp_rmb() will make sure that the spinner state is consulted after sem->count is updated in up_write context. Signed-off-by: Prateek Sood Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave@stgolabs.net Cc: longman@redhat.com Cc: parri.andrea@gmail.com Cc: sramana@codeaurora.org Link: http://lkml.kernel.org/r/1504794658-15397-1-git-send-email-prsood@codeaurora.org Signed-off-by: Ingo Molnar Signed-off-by: Amit Pundir Signed-off-by: Greg Kroah-Hartman

locking/lockdep: Do not record IRQ state within lockdep code

2018-08-24T11:26:55Z

[ Upstream commit fcc784be837714a9173b372ff9fb9b514590dad9 ] While debugging where things were going wrong with mapping enabling/disabling interrupts with the lockdep state and actual real enabling and disabling interrupts, I had to silent the IRQ disabling/enabling in debug_check_no_locks_freed() because it was always showing up as it was called before the splat was. Use raw_local_irq_save/restore() for not only debug_check_no_locks_freed() but for all internal lockdep functions, as they hide useful information about where interrupts were used incorrectly last. Signed-off-by: Steven Rostedt (VMware) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Link: https://lkml.kernel.org/lkml/20180404140630.3f4f4c7a@gandalf.local.home Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman