From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751937AbdJMIsh (ORCPT ); Fri, 13 Oct 2017 04:48:37 -0400 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:36287 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750722AbdJMIsf (ORCPT ); Fri, 13 Oct 2017 04:48:35 -0400 X-Original-SENDERIP: 156.147.1.126 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Fri, 13 Oct 2017 17:48:26 +0900 From: Byungchul Park To: Peter Zijlstra Cc: Tejun Heo , johannes.berg@intel.com, mingo@kernel.org, tglx@linutronix.de, oleg@redhat.com, linux-kernel@vger.kernel.org, kernel-team@lge.com Subject: Re: [RESEND PATCH v2 2/2] lockdep: Remove unnecessary acquisitions wrt workqueue flush Message-ID: <20171013084826.GO3323@X58A-UD3R> References: <1507618297-27470-1-git-send-email-byungchul.park@lge.com> <1507618297-27470-2-git-send-email-byungchul.park@lge.com> <20171012075435.GK3323@X58A-UD3R> <20171012153817.GQ3301751@devbig577.frc2.facebook.com> <20171012155635.ntljsbmtq4mstb2f@hirez.programming.kicks-ass.net> <20171013075633.GN3323@X58A-UD3R> <20171013082750.nggigrx2hyxtwhl6@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171013082750.nggigrx2hyxtwhl6@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 13, 2017 at 10:27:50AM +0200, Peter Zijlstra wrote: > On Fri, Oct 13, 2017 at 04:56:33PM +0900, Byungchul Park wrote: > > On Thu, Oct 12, 2017 at 05:56:35PM +0200, Peter Zijlstra wrote: > > > On Thu, Oct 12, 2017 at 08:38:17AM -0700, Tejun Heo wrote: > > > > > > > > As long as we have the same level of protection, simpler code is of > > > > course preferable. That said, I haven't followed the discussion > > > > closely and don't want to apply it without Peter's ack. Peter? > > > > > > I'm really tied up atm; and feel we should be addressing the false > > > positives generated by the current code before we start doing new stuff > > > on top. > > > > We can never avoid adding false dependencies as long as we use > > acquisitions in that way the workqueue code does, even though you > > successfully replace write acquisitions with recursive-read ones after > > making them work, as you know. > > Not the point; they still need to get annotated away. The block layer > and xfs are now fairly consistently triggering lockdep splats, that > needs to get sorted. I'm not sure if I can help, since I'm not familiar with that sub-systems, but I want to do something for them if I can. Could you share the issues and test cases? Or I suggest that don't wait for recursive-read work to complete but use 'might' thing to avoid the false annotations. I don't say it to rush you to take my patches, but I do beacuse it does exactly what we need in that case. I believe it would be helpful.