From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id 505966B0371 for ; Tue, 30 Oct 2018 07:39:19 -0400 (EDT) Received: by mail-ed1-f69.google.com with SMTP id c1-v6so9028862eds.15 for ; Tue, 30 Oct 2018 04:39:19 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id r14-v6si3257893edl.68.2018.10.30.04.39.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 30 Oct 2018 04:39:18 -0700 (PDT) Date: Tue, 30 Oct 2018 12:39:15 +0100 From: Michal Hocko Subject: Re: [RFC PATCH v2 3/3] mm, oom: hand over MMF_OOM_SKIP to exit path if it is guranteed to finish Message-ID: <20181030113915.GB32673@dhcp22.suse.cz> References: <20181025082403.3806-1-mhocko@kernel.org> <20181025082403.3806-4-mhocko@kernel.org> <201810300445.w9U4jMhu076672@www262.sakura.ne.jp> <20181030063136.GU32673@dhcp22.suse.cz> <95cb93ec-2421-3c5d-fd1e-91d9696b0f5a@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <95cb93ec-2421-3c5d-fd1e-91d9696b0f5a@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: linux-mm@kvack.org, Roman Gushchin , David Rientjes , Andrew Morton , LKML On Tue 30-10-18 18:47:43, Tetsuo Handa wrote: > On 2018/10/30 15:31, Michal Hocko wrote: > > On Tue 30-10-18 13:45:22, Tetsuo Handa wrote: > >> Michal Hocko wrote: > >>> @@ -3156,6 +3166,13 @@ void exit_mmap(struct mm_struct *mm) > >>> vma = remove_vma(vma); > >>> } > >>> vm_unacct_memory(nr_accounted); > >>> + > >>> + /* > >>> + * Now that the full address space is torn down, make sure the > >>> + * OOM killer skips over this task > >>> + */ > >>> + if (oom) > >>> + set_bit(MMF_OOM_SKIP, &mm->flags); > >>> } > >>> > >>> /* Insert vm structure into process list sorted by address > >> > >> I don't like setting MMF_OOF_SKIP after remove_vma() loop. 50 users might > >> call vma->vm_ops->close() from remove_vma(). Some of them are doing fs > >> writeback, some of them might be doing GFP_KERNEL allocation from > >> vma->vm_ops->open() with a lock also held by vma->vm_ops->close(). > >> > >> I don't think that waiting for completion of remove_vma() loop is safe. > > > > What do you mean by 'safe' here? > > > > safe = "Does not cause OOM lockup." > > remove_vma() is allowed to sleep, and some users might depend on memory > allocation when the OOM killer is waiting for remove_vma() to complete. But MMF_OOF_SKIP is set after we are done with remove_vma. In fact it is the very last thing in exit_mmap. So I do not follow what you mean. -- Michal Hocko SUSE Labs