Peter Zijlstra d7bc3197b4 lockdep: Make print_lock() robust against concurrent release ...

During sysrq's show-held-locks command it is possible that
hlock_class() returns NULL for a given lock. The result is then (after
the warning):

	|BUG: unable to handle kernel NULL pointer dereference at 0000001c
	|IP: [<c1088145>] get_usage_chars+0x5/0x100
	|Call Trace:
	| [<c1088263>] print_lock_name+0x23/0x60
	| [<c1576b57>] print_lock+0x5d/0x7e
	| [<c1088314>] lockdep_print_held_locks+0x74/0xe0
	| [<c1088652>] debug_show_all_locks+0x132/0x1b0
	| [<c1315c48>] sysrq_handle_showlocks+0x8/0x10

This *might* happen because the thread on the other CPU drops the lock
after we are looking ->lockdep_depth and ->held_locks points no longer
to a lock that is held.

The fix here is to simply ignore it and continue.

Reported-by: Andreas Messerschmid <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

2015-04-17 09:42:14 +02:00

..

lglock.c

locking: Move the lglocks code to kernel/locking/

2013-11-06 09:24:20 +01:00

lockdep_internals.h

lockdep: Increase static allocations

2014-04-18 14:20:50 +02:00

lockdep_proc.c

lockdep/proc: Fix lock-time avg computation

2013-11-11 12:41:34 +01:00

lockdep_states.h

…

lockdep.c

lockdep: Make print_lock() robust against concurrent release

2015-04-17 09:42:14 +02:00

locktorture.c

locktorture: Cleanup header usage

2014-09-30 00:10:02 -07:00

Makefile

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2015-02-11 17:42:32 -08:00

mcs_spinlock.h

locking: Remove ACCESS_ONCE() usage

2015-02-24 08:44:16 +01:00

mutex-debug.c

mutex: Always clear owner field upon mutex_unlock()

2015-01-09 11:20:39 +01:00

mutex-debug.h

…

mutex.c

locking/mutex: Further simplify mutex_spin_on_owner()

2015-04-09 08:10:23 +02:00

mutex.h

locking/mutexes: Use MUTEX_SPIN_ON_OWNER when appropriate

2014-08-13 10:32:02 +02:00

osq_lock.c

locking: Remove ACCESS_ONCE() usage

2015-02-24 08:44:16 +01:00

percpu-rwsem.c

locking: Move the percpu-rwsem code to kernel/locking/

2013-11-06 09:24:22 +01:00

qrwlock.c

arch, locking: Ciao arch_mutex_cpu_relax()

2014-07-17 12:32:47 +02:00

rtmutex_common.h

rtmutex: Cleanup deadlock detector debug logic

2014-06-21 22:05:30 +02:00

rtmutex-debug.c

rtmutex: Cleanup deadlock detector debug logic

2014-06-21 22:05:30 +02:00

rtmutex-debug.h

rtmutex: Cleanup deadlock detector debug logic

2014-06-21 22:05:30 +02:00

rtmutex-tester.c

locking: Move the rtmutex code to kernel/locking/

2013-11-06 09:23:59 +01:00

rtmutex.c

Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2015-04-13 10:27:28 -07:00

rtmutex.h

rtmutex: Cleanup deadlock detector debug logic

2014-06-21 22:05:30 +02:00

rwsem-spinlock.c

locking/rwsem: Document barrier need when waking tasks

2015-02-18 16:57:10 +01:00

rwsem-xadd.c

locking/rwsem: Fix lock optimistic spinning when owner is not running

2015-03-07 09:50:49 +01:00

rwsem.c

locking/rwsem: Set lock ownership ASAP

2015-02-18 16:57:13 +01:00

rwsem.h

locking/rwsem: Set lock ownership ASAP

2015-02-18 16:57:13 +01:00

semaphore.c

locking/semaphore: Resolve some shadow warnings

2014-09-04 07:17:24 +02:00

spinlock_debug.c

locking: Move the spinlock code to kernel/locking/

2013-11-06 07:55:21 +01:00

spinlock.c

spinlock: Add spin_lock_bh_nested()

2015-01-03 14:32:57 -05:00