Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 256a6b41 authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds
Browse files

[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: default avatarIngo Molnar <mingo@elte.hu>
Cc: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus 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);



/**