Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751549AbcKGTal (ORCPT ); Mon, 7 Nov 2016 14:30:41 -0500 Received: from resqmta-ch2-11v.sys.comcast.net ([69.252.207.43]:38396 "EHLO resqmta-ch2-11v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751277AbcKGTak (ORCPT ); Mon, 7 Nov 2016 14:30:40 -0500 Date: Mon, 7 Nov 2016 13:30:15 -0600 (CST) From: Christoph Lameter X-X-Sender: cl@east.gentwo.org To: Steven Rostedt cc: Daniel Bristot de Oliveira , Ingo Molnar , Peter Zijlstra , linux-rt-users , LKML Subject: Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature In-Reply-To: <20161107133207.4282de69@gandalf.local.home> Message-ID: References: <20161107133207.4282de69@gandalf.local.home> Content-Type: text/plain; charset=US-ASCII X-CMAE-Envelope: MS4wfPaSbmr8fTS9fACpd1p+3pTd8kUShauwH0pu0CYy7NHQ9xN5VmjDLvF0+oc+SRNNaNbKnjbTu3kAnb3K29wD6g/lScXFps3ldlxymQolNCq6juSVsR8J uAZhl/RVrwQ2VyFxcH9AA850HQfk5t1/15lIcpujXs845soirxDpJvqLxJ8J93KQ12svlNbq1QKAuki+L5tzrWI9O84YshYLzFJBbsT9Jh7EVXW9/y7ht5hm 0NluaPwFcHXMO04CtCJYBxTfBo+tM/G/DT/EFnnlfFyfEv+R96foSItn8wfnTWIbe36Q2DjfHz584mxJaBzDM0vM87/YczqHY0lrcs6s0Jw= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 999 Lines: 24 On Mon, 7 Nov 2016, Steven Rostedt wrote: > On Mon, 7 Nov 2016 10:55:38 -0600 (CST) > Christoph Lameter wrote: > > > On Mon, 7 Nov 2016, Daniel Bristot de Oliveira wrote: > > > > > With these two options set, the user will guarantee some runtime > > > for non-rt-tasks on all CPUs, while keeping real-time tasks running > > > as much as possible. > > > > Excellent this would improve the situation with deadlocks as a result of > > cgroup_locks not being released due to lack of workqueue processing. > > ?? What deadlocks do you see? I mean, can you show the situation that > throttling RT tasks will cause deadlock? > > Sorry, but I'm just not seeing it. SCHED_RR tasks alternately running on on cpu can cause endless deferral of kworker threads. With the global effect of the OS processing reserved it may be the case that the processor we are executing never gets any time. And if that kworker threads role is releasing a mutex (like the cgroup_lock) then deadlocks can result.