[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>

1 files changed, 2 insertions, 9 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 771f5e861bcd..f7d427ef5038 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -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);