From: Oleg Nesterov <oleg@tv-sign.ru>
del_timer() and __run_timers() use smp_wmb() before clearing timer's pending
flag. It was needed because __mod_timer() did not locked old_base if the
timer is not pending, so __mod_timer()->internal_add_timer() can race with
del_timer()->list_del().
With the previous patch these functions are serialized through base->lock, so
the barrier can be killed.
Still needed in del_timer_sync(), because it clears ->_base.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/kernel/timer.c | 3 ---
1 files changed, 3 deletions(-)
diff -puN kernel/timer.c~timers-remove-memory-barriers kernel/timer.c
--- 25/kernel/timer.c~timers-remove-memory-barriers 2005-03-19 14:19:57.000000000 -0800
+++ 25-akpm/kernel/timer.c 2005-03-19 14:19:57.000000000 -0800
@@ -337,8 +337,6 @@ repeat:
goto repeat;
}
list_del(&timer->entry);
- /* Need to make sure that anybody who sees a NULL base also sees the list ops */
- smp_wmb();
__set_base(timer, base, 0);
spin_unlock_irqrestore(&base->lock, flags);
@@ -496,7 +494,6 @@ repeat:
list_del(&timer->entry);
set_running_timer(base, timer);
- smp_wmb();
__set_base(timer, base, 0);
spin_unlock_irq(&base->lock);
{
_