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[PATCH] lockdep: fix printk recursion logic

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Bug reported and fixed by Tilman Schmidt <tilman@imap.cc>: if lockdep is
enabled then log messages make it to /var/log/messages belatedly.  The
reason is a missed wakeup of klogd.

Initially there was only a lockdep_internal() protection against lockdep
recursion within vprintk() - it grew the 'outer' lockdep_off()/on()
protection only later on.  But that lockdep_off() made the
release_console_sem() within vprintk() always happen under the
lockdep_internal() condition, causing the bug.

The right solution to remove the inner protection against recursion here -
the outer one is enough.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Ingo Molnar 2006-10-11 01:22:08 -07:00 committed by Linus Torvalds
parent 5fcce7432a
commit 256a6b4136
1 changed files with 2 additions and 9 deletions
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11
kernel/printk.c
View file

@ -820,15 +820,8 @@ void release_console_sem(void)
console_locked = 0;
up(&console_sem);
spin_unlock_irqrestore(&logbuf_lock, flags);
if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait)) {
/*
* If we printk from within the lock dependency code,
* from within the scheduler code, then do not lock
* up due to self-recursion:
*/
if (!lockdep_internal())
wake_up_interruptible(&log_wait);
}
if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
wake_up_interruptible(&log_wait);
}
EXPORT_SYMBOL(release_console_sem);