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[195.135.220.15]) by mx.google.com with ESMTPS id v6si5957837edc.154.2019.02.27.01.21.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Feb 2019 01:21:37 -0800 (PST) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7B6E9ADE2; Wed, 27 Feb 2019 09:21:37 +0000 (UTC) Date: Wed, 27 Feb 2019 10:21:36 +0100 From: Michal Hocko To: Tetsuo Handa Cc: linux-mm@kvack.org Subject: Re: mm: Can we bail out p?d_alloc() loops upon SIGKILL? Message-ID: <20190227092136.GM10588@dhcp22.suse.cz> References: <201902270343.x1R3hpZl029621@www262.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201902270343.x1R3hpZl029621@www262.sakura.ne.jp> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 27-02-19 12:43:51, Tetsuo Handa wrote: > I noticed that when a kdump kernel triggers the OOM killer because a too > small value was given to crashkernel= parameter, the OOM reaper tends to > fail to reclaim memory from OOM victims because they are in dup_mm() from > copy_mm() from copy_process() with mmap_sem held for write. I would presume that a page table allocation would fail for the oom victim as soon as the oom memory reserves get depleted and then copy_page_range would bail out and release the lock. That being said, the oom_reaper might bail out before then but does sprinkling fatal_signal_pending checks into copy_*_range really help reliably? -- Michal Hocko SUSE Labs