From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751470AbdCAHWc (ORCPT ); Wed, 1 Mar 2017 02:22:32 -0500 Received: from LGEAMRELO13.lge.com ([156.147.23.53]:52682 "EHLO lgeamrelo13.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750968AbdCAHW0 (ORCPT ); Wed, 1 Mar 2017 02:22:26 -0500 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 165.244.249.26 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Wed, 1 Mar 2017 16:21:28 +0900 From: Byungchul Park To: Peter Zijlstra CC: , , , , , , , , , , Subject: Re: [PATCH v5 06/13] lockdep: Implement crossrelease feature Message-ID: <20170301072128.GH11663@X58A-UD3R> References: <1484745459-2055-1-git-send-email-byungchul.park@lge.com> <1484745459-2055-7-git-send-email-byungchul.park@lge.com> <20170228181547.GM5680@worktop> MIME-Version: 1.0 In-Reply-To: <20170228181547.GM5680@worktop> User-Agent: Mutt/1.5.21 (2010-09-15) X-MIMETrack: Itemize by SMTP Server on LGEKRMHUB04/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2017/03/01 16:21:41, Serialize by Router on LGEKRMHUB04/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2017/03/01 16:21:41, Serialize complete at 2017/03/01 16:21:41 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 28, 2017 at 07:15:47PM +0100, Peter Zijlstra wrote: > On Wed, Jan 18, 2017 at 10:17:32PM +0900, Byungchul Park wrote: > > + /* > > + * Each work of workqueue might run in a different context, > > + * thanks to concurrency support of workqueue. So we have to > > + * distinguish each work to avoid false positive. > > + * > > + * TODO: We can also add dependencies between two acquisitions > > + * of different work_id, if they don't cause a sleep so make > > + * the worker stalled. > > + */ > > + unsigned int work_id; > > > +/* > > + * Crossrelease needs to distinguish each work of workqueues. > > + * Caller is supposed to be a worker. > > + */ > > +void crossrelease_work_start(void) > > +{ > > + if (current->xhlocks) > > + current->work_id++; > > +} > > So what you're trying to do with that 'work_id' thing is basically wipe > the entire history when we're at the bottom of a context. Sorry, but I do not understand what you are trying to say. What I was trying to do with the 'work_id' is to distinguish between different works, which will be used to check if history locks were held in the same context as a release one. > Which is a useful operation, but should arguably also be done on the > return to userspace path. Any historical lock from before the current > syscall is irrelevant. Sorry. Could you explain it more? > > (And we should not be returning to userspace with locks held anyway -- > lockdep already has a check for that). Yes right. We should not be returning to userspace without reporting it in that case.