From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934446AbaE3Q7N (ORCPT ); Fri, 30 May 2014 12:59:13 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:54723 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754104AbaE3Q7I (ORCPT ); Fri, 30 May 2014 12:59:08 -0400 Message-ID: <5388B8D7.1020907@wwwdotorg.org> Date: Fri, 30 May 2014 10:59:03 -0600 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Vlastimil Babka , Shawn Guo , Kevin Hilman , Andrew Morton CC: Joonsoo Kim , David Rientjes , Hugh Dickins , Greg Thelen , LKML , linux-mm@kvack.org, Minchan Kim , Mel Gorman , Bartlomiej Zolnierkiewicz , Michal Nazarewicz , Christoph Lameter , Rik van Riel , Olof Johansson , linux-arm-kernel Subject: Re: [PATCH v2] mm, compaction: properly signal and act upon lock and need_sched() contention References: <1399904111-23520-1-git-send-email-vbabka@suse.cz> <1400233673-11477-1-git-send-email-vbabka@suse.cz> <537F082F.50501@suse.cz> In-Reply-To: <537F082F.50501@suse.cz> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/23/2014 02:34 AM, Vlastimil Babka wrote: > On 05/23/2014 04:48 AM, Shawn Guo wrote: >> On 23 May 2014 07:49, Kevin Hilman wrote: >>> On Fri, May 16, 2014 at 2:47 AM, Vlastimil Babka wrote: >>>> Compaction uses compact_checklock_irqsave() function to periodically check for >>>> lock contention and need_resched() to either abort async compaction, or to >>>> free the lock, schedule and retake the lock. When aborting, cc->contended is >>>> set to signal the contended state to the caller. Two problems have been >>>> identified in this mechanism. >>> >>> This patch (or later version) has hit next-20140522 (in the form >>> commit 645ceea9331bfd851bc21eea456dda27862a10f4) and according to my >>> bisect, appears to be the culprit of several boot failures on ARM >>> platforms. >> >> On i.MX6 where CMA is enabled, the commit causes the drivers calling >> dma_alloc_coherent() fail to probe. Tracing it a little bit, it seems >> dma_alloc_from_contiguous() always return page as NULL after this >> commit. >> >> Shawn >> > > Really sorry, guys :/ > > -----8<----- > From: Vlastimil Babka > Date: Fri, 23 May 2014 10:18:56 +0200 > Subject: mm-compaction-properly-signal-and-act-upon-lock-and-need_sched-contention-fix2 > > Step 1: Change function name and comment between v1 and v2 so that the return > value signals the opposite thing. > Step 2: Change the call sites to reflect the opposite return value. > Step 3: ??? > Step 4: Make a complete fool of yourself. Tested-by: Stephen Warren This fix doesn't seem to be in linux-next yet:-( From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oa0-f49.google.com (mail-oa0-f49.google.com [209.85.219.49]) by kanga.kvack.org (Postfix) with ESMTP id 2CF6D6B0035 for ; Fri, 30 May 2014 12:59:09 -0400 (EDT) Received: by mail-oa0-f49.google.com with SMTP id eb12so2115343oac.36 for ; Fri, 30 May 2014 09:59:08 -0700 (PDT) Received: from avon.wwwdotorg.org (avon.wwwdotorg.org. [70.85.31.133]) by mx.google.com with ESMTPS id zc3si8981749obb.26.2014.05.30.09.59.08 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Fri, 30 May 2014 09:59:08 -0700 (PDT) Message-ID: <5388B8D7.1020907@wwwdotorg.org> Date: Fri, 30 May 2014 10:59:03 -0600 From: Stephen Warren MIME-Version: 1.0 Subject: Re: [PATCH v2] mm, compaction: properly signal and act upon lock and need_sched() contention References: <1399904111-23520-1-git-send-email-vbabka@suse.cz> <1400233673-11477-1-git-send-email-vbabka@suse.cz> <537F082F.50501@suse.cz> In-Reply-To: <537F082F.50501@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka , Shawn Guo , Kevin Hilman , Andrew Morton Cc: Joonsoo Kim , David Rientjes , Hugh Dickins , Greg Thelen , LKML , linux-mm@kvack.org, Minchan Kim , Mel Gorman , Bartlomiej Zolnierkiewicz , Michal Nazarewicz , Christoph Lameter , Rik van Riel , Olof Johansson , linux-arm-kernel On 05/23/2014 02:34 AM, Vlastimil Babka wrote: > On 05/23/2014 04:48 AM, Shawn Guo wrote: >> On 23 May 2014 07:49, Kevin Hilman wrote: >>> On Fri, May 16, 2014 at 2:47 AM, Vlastimil Babka wrote: >>>> Compaction uses compact_checklock_irqsave() function to periodically check for >>>> lock contention and need_resched() to either abort async compaction, or to >>>> free the lock, schedule and retake the lock. When aborting, cc->contended is >>>> set to signal the contended state to the caller. Two problems have been >>>> identified in this mechanism. >>> >>> This patch (or later version) has hit next-20140522 (in the form >>> commit 645ceea9331bfd851bc21eea456dda27862a10f4) and according to my >>> bisect, appears to be the culprit of several boot failures on ARM >>> platforms. >> >> On i.MX6 where CMA is enabled, the commit causes the drivers calling >> dma_alloc_coherent() fail to probe. Tracing it a little bit, it seems >> dma_alloc_from_contiguous() always return page as NULL after this >> commit. >> >> Shawn >> > > Really sorry, guys :/ > > -----8<----- > From: Vlastimil Babka > Date: Fri, 23 May 2014 10:18:56 +0200 > Subject: mm-compaction-properly-signal-and-act-upon-lock-and-need_sched-contention-fix2 > > Step 1: Change function name and comment between v1 and v2 so that the return > value signals the opposite thing. > Step 2: Change the call sites to reflect the opposite return value. > Step 3: ??? > Step 4: Make a complete fool of yourself. Tested-by: Stephen Warren This fix doesn't seem to be in linux-next yet:-( -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 From: swarren@wwwdotorg.org (Stephen Warren) Date: Fri, 30 May 2014 10:59:03 -0600 Subject: [PATCH v2] mm, compaction: properly signal and act upon lock and need_sched() contention In-Reply-To: <537F082F.50501@suse.cz> References: <1399904111-23520-1-git-send-email-vbabka@suse.cz> <1400233673-11477-1-git-send-email-vbabka@suse.cz> <537F082F.50501@suse.cz> Message-ID: <5388B8D7.1020907@wwwdotorg.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 05/23/2014 02:34 AM, Vlastimil Babka wrote: > On 05/23/2014 04:48 AM, Shawn Guo wrote: >> On 23 May 2014 07:49, Kevin Hilman wrote: >>> On Fri, May 16, 2014 at 2:47 AM, Vlastimil Babka wrote: >>>> Compaction uses compact_checklock_irqsave() function to periodically check for >>>> lock contention and need_resched() to either abort async compaction, or to >>>> free the lock, schedule and retake the lock. When aborting, cc->contended is >>>> set to signal the contended state to the caller. Two problems have been >>>> identified in this mechanism. >>> >>> This patch (or later version) has hit next-20140522 (in the form >>> commit 645ceea9331bfd851bc21eea456dda27862a10f4) and according to my >>> bisect, appears to be the culprit of several boot failures on ARM >>> platforms. >> >> On i.MX6 where CMA is enabled, the commit causes the drivers calling >> dma_alloc_coherent() fail to probe. Tracing it a little bit, it seems >> dma_alloc_from_contiguous() always return page as NULL after this >> commit. >> >> Shawn >> > > Really sorry, guys :/ > > -----8<----- > From: Vlastimil Babka > Date: Fri, 23 May 2014 10:18:56 +0200 > Subject: mm-compaction-properly-signal-and-act-upon-lock-and-need_sched-contention-fix2 > > Step 1: Change function name and comment between v1 and v2 so that the return > value signals the opposite thing. > Step 2: Change the call sites to reflect the opposite return value. > Step 3: ??? > Step 4: Make a complete fool of yourself. Tested-by: Stephen Warren This fix doesn't seem to be in linux-next yet:-(