Re: [RFC PATCH] timer: Improve itimers scalability

[Peter Zijlstra]

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)) {

>  		struct task_cputime group_sample;
>  
> +		/*
> +		 * If another thread in the group is already checking
> +		 * for the thread group cputimer, then we will skip that.
> +		 */
> +		if (READ_ONCE(sig->cputimer.is_checking_timer))
> +			return 0;
> +
>  		sample_cputime_atomic(&group_sample, &sig->cputimer.cputime_atomic);
>  
>  		if (task_cputime_expired(&group_sample, &sig->cputime_expires))


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