On 30 March 2015 at 18:17, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> No, I means something else with that. We can remove the
> tvec_base::running_timer field. Everything that uses that can use
> tbase_running() AFAICT.
Okay, there is one instance which still needs it.
migrate_timers():
BUG_ON(old_base->running_timer);
What I wasn't sure about it is if we get can drop this statement or not.
If we decide not to drop it, then we can convert running_timer into a bool.
> Drop yes, racy not so much I think.
>
>
> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> index 2d3f5c504939..1394f9540348 100644
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -1189,12 +1189,39 @@ static inline void __run_timers(struct tvec_base *base)
> cascade(base, &base->tv5, INDEX(3));
> ++base->timer_jiffies;
> list_replace_init(base->tv1.vec + index, head);
> +
> +again:
> while (!list_empty(head)) {
> void (*fn)(unsigned long);
> unsigned long data;
> bool irqsafe;
>
> - timer = list_first_entry(head, struct timer_list,entry);
> + timer = list_first_entry(head, struct timer_list, entry);
> + if (unlikely(tbase_running(timer))) {
> + /* Only one timer on the list, force wait. */
> + if (unlikely(head->next == head->prev)) {
> + spin_unlock(&base->lock);
> +
> + /*
> + * The only way to get here is if the
> + * handler requeued itself on another
> + * base, this guarantees the timer will
> + * not go away.
> + */
> + while (tbase_running(timer))
> + cpu_relax();
> +
> + spin_lock(&base->lock);
> + } else {
> + /*
> + * Otherwise, rotate the list and try
> + * someone else.
> + */
> + list_move_tail(&timer->entry, head);
> + }
> + goto again;
> + }
> +
> fn = timer->function;
> data = timer->data;
> irqsafe = tbase_get_irqsafe(timer->base);
Yeah, so I have written something similar only. Wasn't sure about what you wrote
earlier. Thanks for the clarification.
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