From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932427AbdHVJhJ (ORCPT ); Tue, 22 Aug 2017 05:37:09 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:37404 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932205AbdHVJhI (ORCPT ); Tue, 22 Aug 2017 05:37:08 -0400 Date: Tue, 22 Aug 2017 11:37:03 +0200 From: Peter Zijlstra To: Byungchul Park Cc: Dave Chinner , mingo@kernel.org, linux-kernel@vger.kernel.org, kernel-team@lge.com, Arnaldo Carvalho de Melo , Tejun Heo , Boqun Feng Subject: Re: [PATCH v3 1/3] lockdep: Make LOCKDEP_CROSSRELEASE configs all part of PROVE_LOCKING Message-ID: <20170822093703.vuuxvxaytna5im33@hirez.programming.kicks-ass.net> References: <1502960261-16206-1-git-send-email-byungchul.park@lge.com> <20170821154600.asyzqs2zg6w6o4pg@hirez.programming.kicks-ass.net> <20170822054603.GT10621@dastard> <20170822090603.vufl5ncoequ5ag6x@hirez.programming.kicks-ass.net> <20170822092236.GI20323@X58A-UD3R> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170822092236.GI20323@X58A-UD3R> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 22, 2017 at 06:22:36PM +0900, Byungchul Park wrote: > On Tue, Aug 22, 2017 at 11:06:03AM +0200, Peter Zijlstra wrote: > > So I did the below little hack, which basically wipes the entire lock > > history when we start a work and thereby disregards/looses the > > dependency on the work 'lock'. > > > > It makes my test box able to boot and build a kernel on XFS, so while I > > see what you're saying (I think), it doesn't appear to instantly show. > > > > Should I run xfstests or something to further verify things are OK? Does > > that need a scratch partition (I keep forgetting how to run that stuff > > :/). > > > > --- > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > > index 66011c9f5df3..de91cdce9460 100644 > > --- a/kernel/locking/lockdep.c > > +++ b/kernel/locking/lockdep.c > > @@ -4756,10 +4756,14 @@ void crossrelease_hist_start(enum xhlock_context_t c) > > { > > struct task_struct *cur = current; > > > > - if (cur->xhlocks) { > > - cur->xhlock_idx_hist[c] = cur->xhlock_idx; > > - cur->hist_id_save[c] = cur->hist_id; > > - } > > + if (!cur->xhlocks) > > + return; > > + > > + if (c == XHLOCK_PROC) > > + invalidate_xhlock(&xhlock(cur->xhlock_idx)); > > We have to detect dependecies if it exists, even in the following case: > > oooooooiiiiiiiiiiiiiiiiiii......... > |<- range for commit ->| > > where > o: acquisition outside of each work, > i: acquisition inside of each work, > > With yours, we can never detect dependecies wrt 'o'. There really shouldn't be any o's when you call crossrelease_hist_start(XHLOCK_PROC), it should denote the bottom of a context, see: https://lkml.kernel.org/r/20170301104328.GD6515@twins.programming.kicks-ass.net And in that respect you placed the calls wrongly in process_one_work(), except it now works out nicely to disregard these fake locks.