From: Oleg Nesterov 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 Signed-off-by: Andrew Morton --- 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); { _