On 07/18, Jeremy Katz wrote:
>
> On Wed, 18 Jul 2007, Oleg Nesterov wrote:
>
> >Jeremy, I agree with Thomas that your patch should not be right, but it
> >does make a difference. Perhaps this is just the timing, but who knows.
> >Could you add some printk's to be sure that lock_timer() actually fails
> >while it never should?
>
> Agreed.
>
> Unfortunately, adding any significant output appears to alter the
> situation to the point where the issue either does not occur, or takes
> significantly longer to surface.
No, no, I didn't mean any significant output. You changed itimer_delete()
> - spin_lock_irqsave(&timer->it_lock, flags);
> + /* timer already deleted? */
> + if (lock_timer(timer->it_id, &flags) == NULL)
> + return;
This change should not help, lock_timer() should always succeed here.
But since it makes a difference, we can make something like
if (lock_timer(timer->it_id, &flags) == NULL) {
printk("Impossible! but it happened.\n");
return;
}
The same for posix_timer_fn().
I still can't believe we have a double-free problem, this looks imposiible.
Do you see the
"idr_remove called for id=%d which is not allocated.\n"
in syslog?
Could you try the patch below? Perhaps we have some wierd problem with
->sigq corruption.
Oleg.
--- t/kernel/posix-timers.c~ 2007-06-29 14:45:04.000000000 +0400
+++ t/kernel/posix-timers.c 2007-07-20 18:07:59.000000000 +0400
@@ -443,13 +443,16 @@ static struct k_itimer * alloc_posix_tim
#define IT_ID_NOT_SET 0
static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
{
+ sigqueue_free(tmr->sigq);
+ tmr->sigq = NULL;
+
if (it_id_set) {
unsigned long flags;
spin_lock_irqsave(&idr_lock, flags);
idr_remove(&posix_timers_id, tmr->it_id);
spin_unlock_irqrestore(&idr_lock, flags);
}
- sigqueue_free(tmr->sigq);
+
if (unlikely(tmr->it_process) &&
tmr->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
put_task_struct(tmr->it_process);
@@ -615,6 +618,7 @@ static struct k_itimer * lock_timer(time
} else
spin_unlock_irqrestore(&idr_lock, *flags);
+ BUG_ON(timr && !timr->sigq);
return timr;
}
-
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