Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754040AbaJGNni (ORCPT ); Tue, 7 Oct 2014 09:43:38 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:49321 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753851AbaJGNnh (ORCPT ); Tue, 7 Oct 2014 09:43:37 -0400 Date: Tue, 7 Oct 2014 06:43:29 -0700 From: "Paul E. McKenney" To: Jiri Pirko Cc: Tejun Heo , Joe Lawrence , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2 1/2] workqueue: add quiescent state between work items Message-ID: <20141007134329.GA4880@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1412529862-17954-1-git-send-email-joe.lawrence@stratus.com> <1412529862-17954-2-git-send-email-joe.lawrence@stratus.com> <20141005192119.GE8549@htj.dyndns.org> <20141005194748.GG8549@htj.dyndns.org> <20141006042158.GW5015@linux.vnet.ibm.com> <20141007072942.GA2088@nanopsycho.orion> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141007072942.GA2088@nanopsycho.orion> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14100713-7164-0000-0000-0000052DF274 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 07, 2014 at 09:29:42AM +0200, Jiri Pirko wrote: > Mon, Oct 06, 2014 at 06:21:58AM CEST, paulmck@linux.vnet.ibm.com wrote: > >On Sun, Oct 05, 2014 at 03:47:48PM -0400, Tejun Heo wrote: > >> On Sun, Oct 05, 2014 at 03:21:19PM -0400, Tejun Heo wrote: > >> > On Sun, Oct 05, 2014 at 01:24:21PM -0400, Joe Lawrence wrote: > >> > > Similar to the stop_machine deadlock scenario on !PREEMPT kernels > >> > > addressed in b22ce2785d97 "workqueue: cond_resched() after processing > >> > > each work item", kworker threads requeueing back-to-back with zero jiffy > >> > > delay can stall RCU. The cond_resched call introduced in that fix will > >> > > yield only iff there are other higher priority tasks to run, so force a > >> > > quiescent RCU state between work items. > >> > > > >> > > Signed-off-by: Joe Lawrence > >> > > Link: https://lkml.kernel.org/r/20140926105227.01325697@jlaw-desktop.mno.stratus.com > >> > > Link: https://lkml.kernel.org/r/20140929115445.40221d8e@jlaw-desktop.mno.stratus.com > >> > > Fixes: b22ce2785d97 ("workqueue: cond_resched() after processing each work item") > >> > > Cc: > >> > > >> > Applied to wq/for-3.17-fixes. If 3.17 comes out before this gets > >> > merged, I'll send it as for-3.18. > >> > >> Oops, the rcu calls aren't in mainline yet. I think it'd be best to > >> route these through the RCU tree. Paul, can you please route these > >> two patches? > >> > >> Acked-by: Tejun Heo > > > >Will do! > > > >I will try 3.17, failing that, 3.18. > > > Paul, Tehun, how do you propose to fix this on older kernels which do > not have rcu_note_voluntary_context_switch? I'm particullary interested > in 3.10. Hello, Jiri, Older kernels can instead use rcu_note_context_switch(). Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/