[PATCH 4/5] timers: remove memory barriers
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 <[EMAIL PROTECTED]>
--- 2.6.12-rc1/kernel/timer.c~4_BARR2005-03-19 22:26:50.0 +0300
+++ 2.6.12-rc1/kernel/timer.c 2005-03-19 22:28:34.0 +0300
@@ -337,8 +337,6 @@ repeat:
goto repeat;
}
list_del(>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(>lock, flags);
@@ -496,7 +494,6 @@ repeat:
list_del(>entry);
set_running_timer(base, timer);
- smp_wmb();
__set_base(timer, base, 0);
spin_unlock_irq(>lock);
{
-
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[PATCH 4/5] timers: remove memory barriers
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 [EMAIL PROTECTED]
--- 2.6.12-rc1/kernel/timer.c~4_BARR2005-03-19 22:26:50.0 +0300
+++ 2.6.12-rc1/kernel/timer.c 2005-03-19 22:28:34.0 +0300
@@ -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);
{
-
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Please read the FAQ at http://www.tux.org/lkml/
