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Date: Thu, 2 Mar 2017 15:38:41 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: Peter Zijlstra <peterz@...radead.org> Cc: Ingo Molnar <mingo@...nel.org>, LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH] sched/rt: Document why has_pushable_tasks() isn't called with a runqueue lock On Wed, 1 Mar 2017 09:37:01 +0100 Peter Zijlstra <peterz@...radead.org> wrote: > On Tue, Feb 28, 2017 at 04:48:56PM -0500, Steven Rostedt wrote: > > > + /* > > + * Normally, has_pushable_tasks() would be performed within the > > + * runqueue lock being held. But if it was not set when entering > > "not set" what? I'm having trouble parsing this. I always forgot that with documentation, pronouns should be avoided. "But if has_pushable_tasks is false when entering" > > > + * this hard interrupt handler function, then to have it set would ", then to have it set to true would" > > + * require a wake up. A wake up of an RT task will either cause a > > + * schedule if the woken task is higher priority than the running > > + * task, or it would try to do a push from the CPU doing the wake > > + * up. Grabbing the runqueue lock in such a case would more likely > > + * just cause unnecessary contention. > > + */ > > if (has_pushable_tasks(rq)) { > > raw_spin_lock(&rq->lock); > > push_rt_task(rq);
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