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lockdep: Fix lock_is_held() on recursion

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The main lock_is_held() user is lockdep_assert_held(), avoid false
assertions in lockdep_off() sections by unconditionally reporting the
lock is taken.

[ the reason this is important is a lockdep_assert_held() in ttwu()
  which triggers a warning under lockdep_off() as in printk() which
  can trigger another wakeup and lock up due to spinlock
  recursion, as reported and heroically debugged by Arne Jansen ]

Reported-and-tested-by: Arne Jansen <lists@die-jansens.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/1307398759.2497.966.camel@laptop
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2011-06-06 12:32:43 +02:00 committed by Ingo Molnar
parent f339b9dc1f
commit f2513cde93
1 changed files with 1 additions and 1 deletions
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2
kernel/lockdep.c
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@ -3426,7 +3426,7 @@ int lock_is_held(struct lockdep_map *lock)
int ret = 0;
if (unlikely(current->lockdep_recursion))
return ret;
return 1; /* avoid false negative lockdep_assert_held() */
raw_local_irq_save(flags);
check_flags(flags);