From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 8BA2A6B0494 for ; Thu, 27 Jul 2017 10:45:48 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id z48so33504856wrc.4 for ; Thu, 27 Jul 2017 07:45:48 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id e204si7298675wme.193.2017.07.27.07.45.47 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 27 Jul 2017 07:45:47 -0700 (PDT) Date: Thu, 27 Jul 2017 16:45:44 +0200 From: Michal Hocko Subject: Re: [PATCH 2/2] mm: replace TIF_MEMDIE checks by tsk_is_oom_victim Message-ID: <20170727144544.GC31031@dhcp22.suse.cz> References: <20170727090357.3205-1-mhocko@kernel.org> <20170727090357.3205-3-mhocko@kernel.org> <201707272301.EII82876.tOOJOFLMHFQSFV@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201707272301.EII82876.tOOJOFLMHFQSFV@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: akpm@linux-foundation.org, rientjes@google.com, hannes@cmpxchg.org, guro@fb.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu 27-07-17 23:01:05, Tetsuo Handa wrote: > Michal Hocko wrote: > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 544d47e5cbbd..86a48affb938 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -1896,7 +1896,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, > > * bypass the last charges so that they can exit quickly and > > * free their memory. > > */ > > - if (unlikely(test_thread_flag(TIF_MEMDIE) || > > + if (unlikely(tsk_is_oom_victim(current) || > > fatal_signal_pending(current) || > > current->flags & PF_EXITING)) > > goto force; > > Did we check http://lkml.kernel.org/r/20160909140508.GO4844@dhcp22.suse.cz ? OK, so your concern was > Does this test_thread_flag(TIF_MEMDIE) (or tsk_is_oom_victim(current)) make sense? > > If current thread is OOM-killed, SIGKILL must be pending before arriving at > do_exit() and PF_EXITING must be set after arriving at do_exit(). > But I can't find locations which do memory allocation between clearing > SIGKILL and setting PF_EXITING. I can't find them either and maybe there are none. But why do we care in this particular patch which merely replaces TIF_MEMDIE check by tsk_is_oom_victim? The code will surely not become less valid. If you believe this check is redundant then send a patch with the clear justification. But I would say, at least from the robustness point of view I would just keep it there. We do not really have any control on what happens between clearing signals and setting PF_EXITING. -- 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