Re: [PATCH 1/9] timer locking optimization

[Oleg Nesterov]

Roman Zippel wrote:
> 
>  int __mod_timer(struct timer_list *timer, unsigned long expires)
> @@ -210,6 +203,7 @@ int __mod_timer(struct timer_list *timer
> 
>         BUG_ON(!timer->function);
> 
> +restart:
>         base = lock_timer_base(timer, &flags);
> 
>         if (timer_pending(timer)) {

Another problem. __mode_timer() does:

	if (timer_pending(timer)) {
		detach_timer(timer, 0);

Note that 'clear_pending' parameter == 0. This means that detach_timer()
will remove the timer from list, but won't clear 'pending' status. So
this will crash after 'goto restart' (or in case of concurrent del_timer()).

Oleg.
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