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printk: avoid double lock acquire 

Commit 4f2a8d3cf5 ("printk: Fix console_sem vs logbuf_lock unlock race")
introduced another silly bug where we would want to acquire an already
held lock.  Avoid this.

Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Zijlstra 2011-12-08 14:34:13 -08:00 committed by Linus Torvalds
parent c193c82f05
commit 09dc3cf93f
1 changed files with 2 additions and 1 deletions
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3
kernel/printk.c
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@ -1293,10 +1293,11 @@ void console_unlock(void)
raw_spin_lock(&logbuf_lock);
if (con_start != log_end)
retry = 1;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
if (retry && console_trylock())
goto again;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
if (wake_klogd)
wake_up_klogd();
}