Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750985AbaJEE5R (ORCPT ); Sun, 5 Oct 2014 00:57:17 -0400 Received: from p02c12o148.mxlogic.net ([208.65.145.81]:44852 "EHLO p02c12o148.mxlogic.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750801AbaJEE5Q (ORCPT ); Sun, 5 Oct 2014 00:57:16 -0400 X-MXL-Hash: 5430cfac44ca99be-7441046d956502a9bc72d78054766dae6a50c1e1 X-MXL-Hash: 5430cfa41039f34f-18ff46a9c5b475198c130b005cffb8aaf6af936c From: Joe Lawrence To: CC: , , , Joe Lawrence Subject: [PATCH] workqueue: add quiescent state between work items Date: Sun, 5 Oct 2014 00:56:40 -0400 Message-ID: <1412485000-5669-1-git-send-email-joe.lawrence@stratus.com> X-Mailer: git-send-email 1.7.10.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [134.111.199.152] X-AnalysisOut: [v=2.1 cv=VN/Jnr/X c=1 sm=1 tr=0 a=o2bo05G+d1rlxuoNbFVhCw==] X-AnalysisOut: [:117 a=o2bo05G+d1rlxuoNbFVhCw==:17 a=_KQqW7t0BisA:10 a=Cdz] X-AnalysisOut: [KgOd8jloA:10 a=BLceEmwcHowA:10 a=uelBKuKpAAAA:8 a=YlVTAMxI] X-AnalysisOut: [AAAA:8 a=VwQbUJbxAAAA:8 a=55vktE7HwCub9vLaWSAA:9 a=kSViFEB] X-AnalysisOut: [My1sA:10] X-Spam: [F=0.5000000000; CM=0.500; MH=0.500(2014100423); S=0.200(2014051901)] X-MAIL-FROM: X-SOURCE-IP: [134.111.1.18] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 with cond_resched_rcu_qs. 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 --- kernel/workqueue.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 5dbe22a..09b685d 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2043,9 +2043,10 @@ __acquires(&pool->lock) * kernels, where a requeueing work item waiting for something to * happen could deadlock with stop_machine as such work item could * indefinitely requeue itself while all other CPUs are trapped in - * stop_machine. + * stop_machine. At the same time, report a quiescent RCU state so + * the same condition doesn't freeze RCU. */ - cond_resched(); + cond_resched_rcu_qs(); spin_lock_irq(&pool->lock); -- 1.7.10.4 -- 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/