From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id 647196B0261 for ; Mon, 12 Sep 2016 07:51:12 -0400 (EDT) Received: by mail-wm0-f70.google.com with SMTP id 1so56976975wmz.2 for ; Mon, 12 Sep 2016 04:51:12 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id yi10si3345536wjb.227.2016.09.12.04.51.11 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 12 Sep 2016 04:51:11 -0700 (PDT) Date: Mon, 12 Sep 2016 13:51:10 +0200 From: Michal Hocko Subject: Re: [PATCH] mm: Don't emit warning from pagefault_out_of_memory() Message-ID: <20160912115104.GJ14524@dhcp22.suse.cz> References: <1473442120-7246-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20160912071651.GB14524@dhcp22.suse.cz> <201609122032.GCI56728.OJFHFtMLVOQSOF@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201609122032.GCI56728.OJFHFtMLVOQSOF@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: linux-mm@kvack.org, akpm@linux-foundation.org, rientjes@google.com, hannes@cmpxchg.org On Mon 12-09-16 20:32:13, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Sat 10-09-16 02:28:40, Tetsuo Handa wrote: > > > Commit c32b3cbe0d067a9c ("oom, PM: make OOM detection in the freezer path > > > raceless") inserted a WARN_ON() into pagefault_out_of_memory() in order > > > to warn when we raced with disabling the OOM killer. But emitting same > > > backtrace forever after the OOM killer/reaper are disabled is pointless > > > because the system is already OOM livelocked. > > > > How that would that be forever? Pagefaults are not GFP_NOFAIL and the > > killed task would just enter the exit path. > > Indeed, there is > > /* Avoid allocations with no watermarks from looping endlessly */ > if (test_thread_flag(TIF_MEMDIE) && !(gfp_mask & __GFP_NOFAIL)) > goto nopage; > > check. > > I don't know if pagefaults can happen after entering do_exit(). It can via g-u-p but callers should be able to handle the failure. [...] > Subject: [PATCH v2] mm: Don't emit warning from pagefault_out_of_memory() > Date: Sat, 10 Sep 2016 02:28:40 +0900 > Message-Id: <1473442120-7246-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> > > Commit c32b3cbe0d067a9c ("oom, PM: make OOM detection in the freezer path > raceless") inserted a WARN_ON() into pagefault_out_of_memory() in order > to warn when we raced with disabling the OOM killer. > > Now, patch "oom, suspend: fix oom_killer_disable vs. pm suspend properly" > introduced a timeout for oom_killer_disable(). Even if we raced with > disabling the OOM killer and the system is OOM livelocked, the OOM killer > will be enabled eventually (in 20 seconds by default) and the OOM livelock > will be solved. Therefore, we no longer need to warn when we raced with > disabling the OOM killer. > > Signed-off-by: Tetsuo Handa > Cc: Michal Hocko > Cc: David Rientjes > Cc: Johannes Weiner Acked-by: Michal Hocko Thanks! > --- > mm/oom_kill.c | 12 +----------- > 1 file changed, 1 insertion(+), 11 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 0034baf..f284e92 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -1069,16 +1069,6 @@ void pagefault_out_of_memory(void) > > if (!mutex_trylock(&oom_lock)) > return; > - > - if (!out_of_memory(&oc)) { > - /* > - * There shouldn't be any user tasks runnable while the > - * OOM killer is disabled, so the current task has to > - * be a racing OOM victim for which oom_killer_disable() > - * is waiting for. > - */ > - WARN_ON(test_thread_flag(TIF_MEMDIE)); > - } > - > + out_of_memory(&oc); > mutex_unlock(&oom_lock); > } > -- > 1.8.3.1 -- Michal Hocko SUSE Labs -- 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