From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934249AbeEWTU2 (ORCPT ); Wed, 23 May 2018 15:20:28 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:37124 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934090AbeEWTUZ (ORCPT ); Wed, 23 May 2018 15:20:25 -0400 Date: Wed, 23 May 2018 12:10:44 -0700 From: "Paul E. McKenney" To: Tejun Heo Cc: Jens Axboe , linux-kernel@vger.kernel.org, Jan Kara , Andrew Morton , kernel-team@fb.com Subject: Re: [PATCH] bdi: Move cgroup bdi_writeback to a dedicated low concurrency workqueue Reply-To: paulmck@linux.vnet.ibm.com References: <20180523175632.GO1718769@devbig577.frc2.facebook.com> <20180523183907.GZ3803@linux.vnet.ibm.com> <20180523185143.GS1718769@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180523185143.GS1718769@devbig577.frc2.facebook.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18052319-0004-0000-0000-000014255D95 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009073; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000261; SDB=6.01036619; UDB=6.00530319; IPR=6.00815747; MB=3.00021262; MTD=3.00000008; XFM=3.00000015; UTC=2018-05-23 19:20:24 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18052319-0005-0000-0000-000087567014 Message-Id: <20180523191044.GC3803@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-05-23_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1805230188 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 23, 2018 at 11:51:43AM -0700, Tejun Heo wrote: > On Wed, May 23, 2018 at 11:39:07AM -0700, Paul E. McKenney wrote: > > > While this resolves the problem at hand, it might be a good idea to > > > isolate rcu_exp_work to its own workqueue too as it can be used from > > > various paths and is prone to this sort of indirect A-A deadlocks. > > > > Commit ad7c946b35ad4 ("rcu: Create RCU-specific workqueues with rescuers") > > was accepted into mainline this past merge window. Does that do what > > you want, or are you looking for something else? > > Ah, that does it. Sorry, was looking at an older kernel. No worries -- after all, I must confess that I was a bit slow in getting to this. Thanx, Paul