From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754242AbdDMOiR (ORCPT ); Thu, 13 Apr 2017 10:38:17 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:47778 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752498AbdDMOiO (ORCPT ); Thu, 13 Apr 2017 10:38:14 -0400 Date: Thu, 13 Apr 2017 16:38:07 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: LKML , Ingo Molnar , Andrew Morton , "Paul E. McKenney" , Thomas Gleixner Subject: Re: [PATCH v2] sched: Have do_idle() call __schedule() without enabling preemption Message-ID: <20170413143807.gukvroojodipwuvg@hirez.programming.kicks-ass.net> References: <20170412142744.6ff07236@gandalf.local.home> <20170413084453.ad4falb7kc53viri@hirez.programming.kicks-ass.net> <20170413094840.347b9829@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170413094840.347b9829@gandalf.local.home> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 13, 2017 at 09:48:40AM -0400, Steven Rostedt wrote: > On Thu, 13 Apr 2017 10:44:53 +0200 > Peter Zijlstra wrote: > > > On Wed, Apr 12, 2017 at 02:27:44PM -0400, Steven Rostedt wrote: > > > + * schedule_idle() is similar to schedule_preempt_disable() except > > > + * that it never enables preemption. > > > > That's not right. The primary distinction is that it doesn't call > > sched_submit_work(). > > That has nothing to do with fixing synchronize_rcu_tasks(), which is > the entire point of my patch, thus it is *not* the primary distinction. It is. The only reason you _can_ avoid that preemption window is by not doing sched_submit_work(). The moment you need to call that, the preemption window comes back.