Re: [RFC] [PATCH] Performance of del_timer_sync

[Ingo Molnar <mingo@elte.hu>]

* Chen, Kenneth W <kenneth.w.chen@intel.com> wrote:

> > +int del_single_shot_timer(struct timer_struct *timer)
> > +{
> > +	if (del_timer(timer))
> > +		del_timer_sync(timer);
> > +}
> >  #endif
> 
> I'm confused, isn't the polarity of del_timer() need to be reversed?
> Also propagate the return value of del_timer_sync()?

indeed. If the removal didnt succeed then we must make sure there's no
timer fn pending. Btw., in that case del_timer_sync() must not succeed -
it would mean the timer fn re-added the timer, which by definition must
not happen here. So i'd go for:

int del_single_shot_timer(struct timer_struct *timer)
{
	int ret = del_timer(timer);

	if (!ret) {
		ret = del_timer_sync(timer);
		BUG_ON(ret);
	}

	return ret;
}

this should catch illegal uses of del_single_shot_timer().

	Ingo