user/sven/linux.git/kernel/locking, branch v4.4.265

rtmutex: Remove unused argument from rt_mutex_proxy_unlock()

2021-02-10T08:07:25Z

From: Thomas Gleixner [ Upstream commit 2156ac1934166d6deb6cd0f6ffc4c1076ec63697 ] Nothing uses the argument. Remove it as preparation to use pi_state_update_owner(). Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

futex: Avoid violating the 10th rule of futex

2021-02-10T08:07:25Z

From: Peter Zijlstra commit c1e2f0eaf015fb7076d51a339011f2383e6dd389 upstream. Julia reported futex state corruption in the following scenario: waiter waker stealer (prio > waiter) futex(WAIT_REQUEUE_PI, uaddr, uaddr2, timeout=[N ms]) futex_wait_requeue_pi() futex_wait_queue_me() freezable_schedule() futex(LOCK_PI, uaddr2) futex(CMP_REQUEUE_PI, uaddr, uaddr2, 1, 0) /* requeues waiter to uaddr2 */ futex(UNLOCK_PI, uaddr2) wake_futex_pi() cmp_futex_value_locked(uaddr2, waiter) wake_up_q() task> futex(LOCK_PI, uaddr2) __rt_mutex_start_proxy_lock() try_to_take_rt_mutex() /* steals lock */ rt_mutex_set_owner(lock, stealer) rt_mutex_wait_proxy_lock() __rt_mutex_slowlock() try_to_take_rt_mutex() /* fails, lock held by stealer */ if (timeout && !timeout->task) return -ETIMEDOUT; fixup_owner() /* lock wasn't acquired, so, fixup_pi_state_owner skipped */ return -ETIMEDOUT; /* At this point, we've returned -ETIMEDOUT to userspace, but the * futex word shows waiter to be the owner, and the pi_mutex has * stealer as the owner */ futex_lock(LOCK_PI, uaddr2) -> bails with EDEADLK, futex word says we're owner. And suggested that what commit: 73d786bd043e ("futex: Rework inconsistent rt_mutex/futex_q state") removes from fixup_owner() looks to be just what is needed. And indeed it is -- I completely missed that requeue_pi could also result in this case. So we need to restore that, except that subsequent patches, like commit: 16ffa12d7425 ("futex: Pull rt_mutex_futex_unlock() out from under hb->lock") changed all the locking rules. Even without that, the sequence: - if (rt_mutex_futex_trylock(&q->pi_state->pi_mutex)) { - locked = 1; - goto out; - } - raw_spin_lock_irq(&q->pi_state->pi_mutex.wait_lock); - owner = rt_mutex_owner(&q->pi_state->pi_mutex); - if (!owner) - owner = rt_mutex_next_owner(&q->pi_state->pi_mutex); - raw_spin_unlock_irq(&q->pi_state->pi_mutex.wait_lock); - ret = fixup_pi_state_owner(uaddr, q, owner); already suggests there were races; otherwise we'd never have to look at next_owner. So instead of doing 3 consecutive wait_lock sections with who knows what races, we do it all in a single section. Additionally, the usage of pi_state->owner in fixup_owner() was only safe because only the rt_mutex owner would modify it, which this additional case wrecks. Luckily the values can only change away and not to the value we're testing, this means we can do a speculative test and double check once we have the wait_lock. Fixes: 73d786bd043e ("futex: Rework inconsistent rt_mutex/futex_q state") Reported-by: Julia Cartwright Reported-by: Gratian Crisan Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Tested-by: Julia Cartwright Tested-by: Gratian Crisan Cc: Darren Hart Link: https://lkml.kernel.org/r/20171208124939.7livp7no2ov65rrc@hirez.programming.kicks-ass.net Signed-off-by: Greg Kroah-Hartman [Lee: Back-ported to solve a dependency] Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

futex: Remove rt_mutex_deadlock_account_*()

2021-02-10T08:07:25Z

From: Peter Zijlstra These are unused and clutter up the code. 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/20170322104151.652692478@infradead.org Signed-off-by: Thomas Gleixner [Lee: Back-ported to solve a dependency] Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

futex,rt_mutex: Provide futex specific rt_mutex API

2021-02-10T08:07:25Z

From: Peter Zijlstra [ Upstream commit 5293c2efda37775346885c7e924d4ef7018ea60b ] Part of what makes futex_unlock_pi() intricate is that rt_mutex_futex_unlock() -> rt_mutex_slowunlock() can drop rt_mutex::wait_lock. This means it cannot rely on the atomicy of wait_lock, which would be preferred in order to not rely on hb->lock so much. The reason rt_mutex_slowunlock() needs to drop wait_lock is because it can race with the rt_mutex fastpath, however futexes have their own fast path. Since futexes already have a bunch of separate rt_mutex accessors, complete that set and implement a rt_mutex variant without fastpath for them. 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/20170322104151.702962446@infradead.org Signed-off-by: Thomas Gleixner [Lee: Back-ported to solve a dependency] Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

locking/lockdep: Fix overflow in presentation of average lock-time

2020-09-03T09:19:24Z

[ Upstream commit a7ef9b28aa8d72a1656fa6f0a01bbd1493886317 ] Though the number of lock-acquisitions is tracked as unsigned long, this is passed as the divisor to div_s64() which interprets it as a s32, giving nonsense values with more than 2 billion acquisitons. E.g. acquisitions holdtime-min holdtime-max holdtime-total holdtime-avg ------------------------------------------------------------------------- 2350439395 0.07 353.38 649647067.36 0.-32 Signed-off-by: Chris Wilson Signed-off-by: Ingo Molnar Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20200725185110.11588-1-chris@chris-wilson.co.uk Signed-off-by: Sasha Levin

locktorture: Print ratio of acquisitions, not failures

2020-04-24T05:57:26Z

commit 80c503e0e68fbe271680ab48f0fe29bc034b01b7 upstream. The __torture_print_stats() function in locktorture.c carefully initializes local variable "min" to statp[0].n_lock_acquired, but then compares it to statp[i].n_lock_fail. Given that the .n_lock_fail field should normally be zero, and given the initialization, it seems reasonable to display the maximum and minimum number acquisitions instead of miscomputing the maximum and minimum number of failures. This commit therefore switches from failures to acquisitions. And this turns out to be not only a day-zero bug, but entirely my own fault. I hate it when that happens! Fixes: 0af3fe1efa53 ("locktorture: Add a lock-torture kernel module") Reported-by: Will Deacon Signed-off-by: Paul E. McKenney Acked-by: Will Deacon Cc: Davidlohr Bueso Cc: Josh Triplett Cc: Peter Zijlstra Signed-off-by: Greg Kroah-Hartman

locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps()

2020-04-24T05:57:07Z

[ Upstream commit 25016bd7f4caf5fc983bbab7403d08e64cba3004 ] Qian Cai reported a bug when PROVE_RCU_LIST=y, and read on /proc/lockdep triggered a warning: [ ] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled) ... [ ] Call Trace: [ ] lock_is_held_type+0x5d/0x150 [ ] ? rcu_lockdep_current_cpu_online+0x64/0x80 [ ] rcu_read_lock_any_held+0xac/0x100 [ ] ? rcu_read_lock_held+0xc0/0xc0 [ ] ? __slab_free+0x421/0x540 [ ] ? kasan_kmalloc+0x9/0x10 [ ] ? __kmalloc_node+0x1d7/0x320 [ ] ? kvmalloc_node+0x6f/0x80 [ ] __bfs+0x28a/0x3c0 [ ] ? class_equal+0x30/0x30 [ ] lockdep_count_forward_deps+0x11a/0x1a0 The warning got triggered because lockdep_count_forward_deps() call __bfs() without current->lockdep_recursion being set, as a result a lockdep internal function (__bfs()) is checked by lockdep, which is unexpected, and the inconsistency between the irq-off state and the state traced by lockdep caused the warning. Apart from this warning, lockdep internal functions like __bfs() should always be protected by current->lockdep_recursion to avoid potential deadlocks and data inconsistency, therefore add the current->lockdep_recursion on-and-off section to protect __bfs() in both lockdep_count_forward_deps() and lockdep_count_backward_deps() Reported-by: Qian Cai Signed-off-by: Boqun Feng Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200312151258.128036-1-boqun.feng@gmail.com Signed-off-by: Sasha Levin

locking/spinlock/debug: Fix various data races

2020-01-12T10:22:46Z

[ Upstream commit 1a365e822372ba24c9da0822bc583894f6f3d821 ] This fixes various data races in spinlock_debug. By testing with KCSAN, it is observable that the console gets spammed with data races reports, suggesting these are extremely frequent. Example data race report: read to 0xffff8ab24f403c48 of 4 bytes by task 221 on cpu 2: debug_spin_lock_before kernel/locking/spinlock_debug.c:85 [inline] do_raw_spin_lock+0x9b/0x210 kernel/locking/spinlock_debug.c:112 __raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline] _raw_spin_lock+0x39/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] get_partial_node.isra.0.part.0+0x32/0x2f0 mm/slub.c:1873 get_partial_node mm/slub.c:1870 [inline] write to 0xffff8ab24f403c48 of 4 bytes by task 167 on cpu 3: debug_spin_unlock kernel/locking/spinlock_debug.c:103 [inline] do_raw_spin_unlock+0xc9/0x1a0 kernel/locking/spinlock_debug.c:138 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:159 [inline] _raw_spin_unlock_irqrestore+0x2d/0x50 kernel/locking/spinlock.c:191 spin_unlock_irqrestore include/linux/spinlock.h:393 [inline] free_debug_processing+0x1b3/0x210 mm/slub.c:1214 __slab_free+0x292/0x400 mm/slub.c:2864 As a side-effect, with KCSAN, this eventually locks up the console, most likely due to deadlock, e.g. .. -> printk lock -> spinlock_debug -> KCSAN detects data race -> kcsan_print_report() -> printk lock -> deadlock. This fix will 1) avoid the data races, and 2) allow using lock debugging together with KCSAN. Reported-by: Qian Cai Signed-off-by: Marco Elver 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/20191120155715.28089-1-elver@google.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

locking/lockdep: Add debug_locks check in __lock_downgrade()

2019-10-05T10:27:39Z

[ Upstream commit 513e1073d52e55b8024b4f238a48de7587c64ccf ] 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(). 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: Sasha Levin

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