Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751301AbdH3FSR (ORCPT ); Wed, 30 Aug 2017 01:18:17 -0400 Received: from mail-pg0-f44.google.com ([74.125.83.44]:38397 "EHLO mail-pg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750895AbdH3FSP (ORCPT ); Wed, 30 Aug 2017 01:18:15 -0400 Date: Wed, 30 Aug 2017 14:20:37 +0900 From: Sergey Senozhatsky To: Byungchul Park Cc: Bart Van Assche , peterz@infradead.org, "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "sergey.senozhatsky.work@gmail.com" , "martin.petersen@oracle.com" , "axboe@kernel.dk" , "linux-scsi@vger.kernel.org" , "sfr@canb.auug.org.au" , "linux-next@vger.kernel.org" , kernel-team@lge.com Subject: Re: possible circular locking dependency detected [was: linux-next: Tree for Aug 22] Message-ID: <20170830052037.GA432@jagdpanzerIV.localdomain> References: <20170822183816.7925e0f8@canb.auug.org.au> <20170822104708.GA491@jagdpanzerIV.localdomain> <1503438234.2508.27.camel@wdc.com> <20170823000304.GK20323@X58A-UD3R> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170823000304.GK20323@X58A-UD3R> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1776 Lines: 60 On (08/23/17 09:03), Byungchul Park wrote: [..] > > Byungchul, did you add the crosslock checks to lockdep? Can you have a look at > > the above report? That report namely doesn't make sense to me. > > The report is talking about the following lockup: > > A work in a worker A task work on exit to user > ------------------ --------------------------- > mutex_lock(&bdev->bd_mutex) > mutext_lock(&bdev->bd_mutex) > blk_execute_rq() > wait_for_completion_io_timeout(&A) > complete(&A) > [..] > To Peterz, > > Anyway I wanted to avoid lockdep reports in the case using a timeout > interface. Do you think it's still worth reporting the kind of lockup? > I'm ok if you do. Byungchul, a quick question. have you measured the performance impact? somehow my linux-next is notably slower than earlier 4.13 linux-next. (e.g. scrolling in vim is irritatingly slow) `time dmesg' shows some difference, but probably that's not a good test. !LOCKDEP LOCKDEP LOCKDEP -CROSSRELEASE -COMPLETIONS real 0m0.661s 0m2.290s 0m1.920s user 0m0.010s 0m0.105s 0m0.000s sys 0m0.636s 0m2.224s 0m1.888s anyone else "sees"/"can confirm" the slow down? it gets back to "usual normal" when I disable CROSSRELEASE and COMPLETIONS. --- diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index b19c491cbc4e..cdc30ef81c5e 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1091,8 +1091,6 @@ config PROVE_LOCKING select DEBUG_MUTEXES select DEBUG_RT_MUTEXES if RT_MUTEXES select DEBUG_LOCK_ALLOC - select LOCKDEP_CROSSRELEASE - select LOCKDEP_COMPLETIONS select TRACE_IRQFLAGS default n help --- -ss