Messages in this thread Patch in this message | | | From | Paul Gortmaker <> | Subject | [34-longterm 052/179] lockdep: Fix lock_is_held() on recursion | Date | Mon, 14 May 2012 22:12:28 -0400 |
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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. -------------------
commit f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d upstream.
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> Link: http://lkml.kernel.org/r/1307398759.2497.966.camel@laptop Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> --- kernel/lockdep.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 2594e1c..1571452 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -3240,7 +3240,7 @@ 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); -- 1.7.9.6
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