From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932206AbcFCIlt (ORCPT ); Fri, 3 Jun 2016 04:41:49 -0400 Received: from outbound-smtp10.blacknight.com ([46.22.139.15]:51080 "EHLO outbound-smtp10.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932109AbcFCIlq (ORCPT ); Fri, 3 Jun 2016 04:41:46 -0400 Date: Fri, 3 Jun 2016 09:41:42 +0100 From: Mel Gorman To: Geert Uytterhoeven Cc: Andrew Morton , Vlastimil Babka , Linux Kernel Mailing List , Linux MM , linux-m68k Subject: Re: BUG: scheduling while atomic: cron/668/0x10c9a0c0 Message-ID: <20160603084142.GY2527@techsingularity.net> References: <20160530155644.GP2527@techsingularity.net> <574E05B8.3060009@suse.cz> <20160601091921.GT2527@techsingularity.net> <574EB274.4030408@suse.cz> <20160602103936.GU2527@techsingularity.net> <0eb1f112-65d4-f2e5-911e-697b21324b9f@suse.cz> <20160602121936.GV2527@techsingularity.net> <20160602114341.e3b974640fc3f8cbcb54898b@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 03, 2016 at 09:57:22AM +0200, Geert Uytterhoeven wrote: > Hi Andrew, Mel, > > On Thu, Jun 2, 2016 at 8:43 PM, Andrew Morton wrote: > > On Thu, 2 Jun 2016 13:19:36 +0100 Mel Gorman wrote: > >> > >Signed-off-by: Mel Gorman > >> > > >> > Acked-by: Vlastimil Babka > >> > > >> > >> Thanks. > > > > I queued this. A tested-by:Geert would be nice? > > > > > > From: Mel Gorman > > Subject: mm, page_alloc: recalculate the preferred zoneref if the context can ignore memory policies > > > > The optimistic fast path may use cpuset_current_mems_allowed instead of of > > a NULL nodemask supplied by the caller for cpuset allocations. The > > preferred zone is calculated on this basis for statistic purposes and as a > > starting point in the zonelist iterator. > > > > However, if the context can ignore memory policies due to being atomic or > > being able to ignore watermarks then the starting point in the zonelist > > iterator is no longer correct. This patch resets the zonelist iterator in > > the allocator slowpath if the context can ignore memory policies. This > > will alter the zone used for statistics but only after it is known that it > > makes sense for that context. Resetting it before entering the slowpath > > would potentially allow an ALLOC_CPUSET allocation to be accounted for > > against the wrong zone. Note that while nodemask is not explicitly set to > > the original nodemask, it would only have been overwritten if > > cpuset_enabled() and it was reset before the slowpath was entered. > > > > Link: http://lkml.kernel.org/r/20160602103936.GU2527@techsingularity.net > > Fixes: c33d6c06f60f710 ("mm, page_alloc: avoid looking up the first zone in a zonelist twice") > > My understanding was that this was an an additional patch, not fixing > the problem in-se? > It doesn't fix the problem you had, it is a follow-on patch that potentially affects. > Indeed, after applying this patch (without the other one that added > "z = ac->preferred_zoneref;" to the reset_fair block of > get_page_from_freelist()) I still get crashes... > The patch you have is the only one required for the crash. This patch handles a corner case with atomic allocations that can ignore memory policies. > Now testing with both applied... Thanks. -- Mel Gorman SUSE Labs