From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw0-f198.google.com (mail-yw0-f198.google.com [209.85.161.198]) by kanga.kvack.org (Postfix) with ESMTP id 041F26B0005 for ; Thu, 14 Jul 2016 08:29:37 -0400 (EDT) Received: by mail-yw0-f198.google.com with SMTP id i12so135617010ywa.0 for ; Thu, 14 Jul 2016 05:29:37 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id u197si896892ywu.234.2016.07.14.05.29.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Jul 2016 05:29:36 -0700 (PDT) Date: Thu, 14 Jul 2016 08:29:32 -0400 (EDT) From: Mikulas Patocka Subject: Re: System freezes after OOM In-Reply-To: <201607142001.BJD07258.SMOHFOJVtLFOQF@I-love.SAKURA.ne.jp> Message-ID: References: <20160713133955.GK28723@dhcp22.suse.cz> <20160713145638.GM28723@dhcp22.suse.cz> <201607142001.BJD07258.SMOHFOJVtLFOQF@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: rientjes@google.com, mhocko@kernel.org, okozina@redhat.com, jmarchan@redhat.com, skozina@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com On Thu, 14 Jul 2016, Tetsuo Handa wrote: > Michal Hocko wrote: > > OK, this is the part I have missed. I didn't realize that the swapout > > path, which is indeed PF_MEMALLOC, can get down to blk code which uses > > mempools. A quick code travers shows that at least > > make_request_fn = blk_queue_bio > > blk_queue_bio > > get_request > > __get_request > > > > might do that. And in that case I agree that the above mentioned patch > > has unintentional side effects and should be re-evaluated. David, what > > do you think? An obvious fixup would be considering TIF_MEMDIE in > > mempool_alloc explicitly. > > TIF_MEMDIE is racy. Since the OOM killer sets TIF_MEMDIE on only one thread, > there is no guarantee that TIF_MEMDIE is set to the thread which is looping > inside mempool_alloc(). If the device mapper subsystem is not returning objects to the mempool, it should be investigated as a bug in the device mapper. There is no need to add workarounds to mempool_alloc to work around that bug. Mikulas > And since __GFP_NORETRY is used (regardless of > f9054c70d28bc214), out_of_memory() is not called via __alloc_pages_may_oom(). > This means that the thread which is looping inside mempool_alloc() can't > get TIF_MEMDIE unless TIF_MEMDIE is set by the OOM killer. > > Maybe set __GFP_NOMEMALLOC by default at mempool_alloc() and remove it > at mempool_alloc() when fatal_signal_pending() is true? But that behavior > can OOM-kill somebody else when current was not OOM-killed. Sigh... > > David Rientjes wrote: > > On Wed, 13 Jul 2016, Mikulas Patocka wrote: > > > > > What are the real problems that f9054c70d28bc214b2857cf8db8269f4f45a5e23 > > > tries to fix? > > > > > > > It prevents the whole system from livelocking due to an oom killed process > > stalling forever waiting for mempool_alloc() to return. No other threads > > may be oom killed while waiting for it to exit. > > Is that concern still valid? We have the OOM reaper for CONFIG_MMU=y case. > -- 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