lockdep, timer: Fix del_timer_sync() annotation

Calling local_bh_enable() will want to actually start processing
softirqs, which isn't a good idea since this can get called with IRQs
disabled.

Cure this by using _local_bh_enable() which doesn't start processing
softirqs, and use raw_local_irq_save() to avoid any softirqs from
happening without letting lockdep think IRQs are in fact disabled.

Reported-by: Nick Bowler <nbowler@elliptictech.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Yong Zhang <yong.zhang0@gmail.com>
LKML-Reference: <20110203141548.039540914@chello.nl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/timer.c b/kernel/timer.c
index 43ca993..d53ce66 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -969,10 +969,14 @@ EXPORT_SYMBOL(try_to_del_timer_sync);
 int del_timer_sync(struct timer_list *timer)
 {
 #ifdef CONFIG_LOCKDEP
+       unsigned long flags;
+
+       raw_local_irq_save(flags);
        local_bh_disable();
        lock_map_acquire(&timer->lockdep_map);
        lock_map_release(&timer->lockdep_map);
-       local_bh_enable();
+       _local_bh_enable();
+       raw_local_irq_restore(flags);
 #endif
        /*
         * don't use it in hardirq context, because it