linux-sg2042/kernel/locking
Thomas Gleixner 397335f004 rtmutex: Fix deadlock detector for real
The current deadlock detection logic does not work reliably due to the
following early exit path:

	/*
	 * Drop out, when the task has no waiters. Note,
	 * top_waiter can be NULL, when we are in the deboosting
	 * mode!
	 */
	if (top_waiter && (!task_has_pi_waiters(task) ||
			   top_waiter != task_top_pi_waiter(task)))
		goto out_unlock_pi;

So this not only exits when the task has no waiters, it also exits
unconditionally when the current waiter is not the top priority waiter
of the task.

So in a nested locking scenario, it might abort the lock chain walk
and therefor miss a potential deadlock.

Simple fix: Continue the chain walk, when deadlock detection is
enabled.

We also avoid the whole enqueue, if we detect the deadlock right away
(A-A). It's an optimization, but also prevents that another waiter who
comes in after the detection and before the task has undone the damage
observes the situation and detects the deadlock and returns
-EDEADLOCK, which is wrong as the other task is not in a deadlock
situation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20140522031949.725272460@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-28 17:28:13 +02:00
..
Makefile lglock: map to spinlock when !CONFIG_SMP 2014-04-07 16:36:14 -07:00
lglock.c locking: Move the lglocks code to kernel/locking/ 2013-11-06 09:24:20 +01:00
lockdep.c asmlinkage: Add explicit __visible to drivers/*, lib/*, kernel/* 2014-05-05 16:07:46 -07:00
lockdep_internals.h locking: Move the lockdep code to kernel/locking/ 2013-11-06 07:55:08 +01:00
lockdep_proc.c lockdep/proc: Fix lock-time avg computation 2013-11-11 12:41:34 +01:00
lockdep_states.h locking: Move the lockdep code to kernel/locking/ 2013-11-06 07:55:08 +01:00
locktorture.c rcutorture: Add a lock_busted to test the test 2014-02-23 09:04:43 -08:00
mcs_spinlock.c locking/mutexes: Introduce cancelable MCS lock for adaptive spinning 2014-03-11 12:14:56 +01:00
mcs_spinlock.h locking/mutexes: Introduce cancelable MCS lock for adaptive spinning 2014-03-11 12:14:56 +01:00
mutex-debug.c locking/mutex: Fix debug_mutexes 2014-04-11 10:40:35 +02:00
mutex-debug.h
mutex.c Merge branch 'x86-asmlinkage-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-03-31 14:13:25 -07:00
mutex.h
percpu-rwsem.c locking: Move the percpu-rwsem code to kernel/locking/ 2013-11-06 09:24:22 +01:00
rtmutex-debug.c rtmutex: Turn the plist into an rb-tree 2014-01-13 13:41:50 +01:00
rtmutex-debug.h locking: Move the rtmutex code to kernel/locking/ 2013-11-06 09:23:59 +01:00
rtmutex-tester.c locking: Move the rtmutex code to kernel/locking/ 2013-11-06 09:23:59 +01:00
rtmutex.c rtmutex: Fix deadlock detector for real 2014-05-28 17:28:13 +02:00
rtmutex.h locking: Move the rtmutex code to kernel/locking/ 2013-11-06 09:23:59 +01:00
rtmutex_common.h sched/deadline: Add SCHED_DEADLINE inheritance logic 2014-01-13 13:42:56 +01:00
rwsem-spinlock.c locking: Move the rwsem code to kernel/locking/ 2013-11-06 09:24:18 +01:00
rwsem-xadd.c asmlinkage: Mark rwsem functions that can be called from assembler asmlinkage 2014-02-13 18:13:37 -08:00
rwsem.c locking: Move the rwsem code to kernel/locking/ 2013-11-06 09:24:18 +01:00
semaphore.c locking: Move the semaphore core to kernel/locking/ 2013-11-06 07:55:22 +01:00
spinlock.c locking: Move the spinlock code to kernel/locking/ 2013-11-06 07:55:21 +01:00
spinlock_debug.c locking: Move the spinlock code to kernel/locking/ 2013-11-06 07:55:21 +01:00