Commit 256a6b41 authored Oct 11, 2006 by Ingo Molnar Committed by Linus Torvalds Oct 11, 2006

[PATCH] lockdep: fix printk recursion logic



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>

parent 5fcce743

kernel/printk.c

+2 −9

Original line number	Diff line number	Diff line
		@@ -820,16 +820,9 @@ 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())
		if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
		wake_up_interruptible(&log_wait);
		}
		}
		EXPORT_SYMBOL(release_console_sem);

		/**

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