From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f172.google.com (mail-pf0-f172.google.com [209.85.192.172]) by kanga.kvack.org (Postfix) with ESMTP id 891ED6B0005 for ; Fri, 11 Mar 2016 17:01:11 -0500 (EST) Received: by mail-pf0-f172.google.com with SMTP id u190so63113908pfb.3 for ; Fri, 11 Mar 2016 14:01:11 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id b14si1913289pat.152.2016.03.11.14.01.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 11 Mar 2016 14:01:10 -0800 (PST) Date: Fri, 11 Mar 2016 14:01:09 -0800 From: Greg Kroah-Hartman Subject: Re: [PATCH] android,lowmemorykiller: Don't abuse TIF_MEMDIE. Message-ID: <20160311220109.GD11274@kroah.com> References: <1457434892-12642-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20160308141858.GJ13542@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160308141858.GJ13542@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Tetsuo Handa , devel@driverdev.osuosl.org, linux-mm@kvack.org, Arve Hjonnevag , Riley Andrews On Tue, Mar 08, 2016 at 03:18:59PM +0100, Michal Hocko wrote: > On Tue 08-03-16 20:01:32, Tetsuo Handa wrote: > > Currently, lowmemorykiller (LMK) is using TIF_MEMDIE for two purposes. > > One is to remember processes killed by LMK, and the other is to > > accelerate termination of processes killed by LMK. > > > > But since LMK is invoked as a memory shrinker function, there still > > should be some memory available. It is very likely that memory > > allocations by processes killed by LMK will succeed without using > > ALLOC_NO_WATERMARKS via TIF_MEMDIE. Even if their allocations cannot > > escape from memory allocation loop unless they use ALLOC_NO_WATERMARKS, > > lowmem_deathpending_timeout can guarantee forward progress by choosing > > next victim process. > > > > On the other hand, mark_oom_victim() assumes that it must be called with > > oom_lock held and it must not be called after oom_killer_disable() was > > called. But LMK is calling it without holding oom_lock and checking > > oom_killer_disabled. It is possible that LMK calls mark_oom_victim() > > due to allocation requests by kernel threads after current thread > > returned from oom_killer_disabled(). This will break synchronization > > for PM/suspend. > > > > This patch introduces per a task_struct flag for remembering processes > > killed by LMK, and replaces TIF_MEMDIE with that flag. By applying this > > patch, assumption by mark_oom_victim() becomes true. > > Thanks for looking into this. A separate flag sounds like a better way > to go (assuming that the flags are not scarce which doesn't seem to be > the case here). > > The LMK cannot kill the frozen tasks now but this shouldn't be a big deal > because this is not strictly necessary for the system to move on. We are > not OOM. > > > Signed-off-by: Tetsuo Handa > > Cc: Michal Hocko > > Cc: Greg Kroah-Hartman > > Cc: Arve Hjonnevag > > Cc: Riley Andrews > > Acked-by: Michal Hocko So, any objection for me taking this through the staging tree? thanks, greg k-h -- 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