From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753012AbcA2KPb (ORCPT ); Fri, 29 Jan 2016 05:15:31 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:33105 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750914AbcA2KP0 (ORCPT ); Fri, 29 Jan 2016 05:15:26 -0500 Date: Fri, 29 Jan 2016 11:15:22 +0100 From: Peter Zijlstra To: Jan Stancek Cc: alex shi , guz fnst , mingo@redhat.com, jolsa@redhat.com, riel@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [BUG] scheduler doesn't balance thread to idle cpu for 3 seconds Message-ID: <20160129101522.GF6357@twins.programming.kicks-ass.net> References: <56A8D994.6050205@redhat.com> <56AA39D6.4070509@redhat.com> <20160128174903.GV6356@twins.programming.kicks-ass.net> <333246323.13611103.1454006593261.JavaMail.zimbra@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <333246323.13611103.1454006593261.JavaMail.zimbra@redhat.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 28, 2016 at 01:43:13PM -0500, Jan Stancek wrote: > > How long should I have to wait for a fail? > > It's about 1000-2000 iterations for me, which I think you covered > by now in those 2 hours. So I've been running: while ! ./pthread_cond_wait_1 ; do sleep 1; done overnight on the machine, and have yet to hit a wobbly -- that is, its still running. Also note that I don't think failing this test is a bug per se. Undesirable maybe, but within spec, since SIGALRM is process wide, so it being delivered to the SCHED_OTHER task is accepted, and SCHED_OTHER has no timeliness guarantees. That said; if I could reliably reproduce I'd have a go at fixing this, I suspect there's a 'fun' problem at the bottom of this.