Roman,
I looked up the exact problem again.
On Sun, 2006-03-12 at 14:26 +0100, Roman Zippel wrote:
> > softirq runs on CPU0
> > base->lock()
> >
> > remove_timer(timer);
> >
> > base->unlock()
> > signal of previous expiry is delivered on CPU1
> > timer is reqeued.
-------> sig_ignore is set
> > requeue = timer->fn();
> >
> > base->lock()
> >
> > if (requeue)
> > enqueue_timer(timer)
> >
> > --> OOPS
> >
> > We can not wait in the signal delivery path until the callback has been
> > executed, as we hold the posix-timer->lock and this would deadlock
> > timer->fn().
>
> posix_timer either restarts the timer directly or via signal delivery, but
> never both, so this case can't happen (unless there is a bug in the
> posix_timer).
It took quite a time to track this down. Its unlikely, but it _CAN_
happen !
tglx
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