Re: [RFC PATCH] timer: Improve itimers scalability

[Jason Low]

On Wed, 2015-08-05 at 11:37 +0200, Peter Zijlstra wrote:
> On Tue, Aug 04, 2015 at 05:29:44PM -0700, Jason Low wrote:
> 
> > @@ -1137,6 +1148,13 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
> >  	if (READ_ONCE(sig->cputimer.running)) {
> 
> Maybe make that:
> 
> 	if (READ_ONCE(sig->cputimer.running) &&
> 	    !READ_ONCE(sig->cputimer.is_checking_timer)) {

Yes, I think it would be better if the check is done here.

And perhaps the comment can be modified to:

/*
 * Check if thread group timers expired. This is skipped if the cputimer
 * is not running or if another thread in the group is already checking
 * for thread group cputimers.
 */

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