Re: [patch] del_timer_sync scalability patch
From: Oleg Nesterov
Date: Sun Mar 13 2005 - 07:08:49 EST
I suspect that del_timer_sync() in its current form is racy.
CPU 0 CPU 1
__run_timers() sets timer->base = NULL
del_timer_sync() starts, calls del_timer(), it returns
because timer->base == NULL.
waits until the run is complete:
while (base->running_timer == timer)
preempt_check_resched();
calls schedule(), or long interrupt happens.
timer reschedules itself, __run_timers()
exits.
base->running_timer == NULL, end of loop.
next timer interrupt, __run_timers() picks
this timer again, sets timer->base = NULL
if (timer_pending(timer)) // no, timer->base == NULL
goto del_again; // not taken
del_timer_sync() returns
timer runs.
No?
Oleg.
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