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[140.211.169.12]) by mx.google.com with ESMTPS id q77si5786278pfi.220.2019.02.12.12.56.36 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Feb 2019 12:56:36 -0800 (PST) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) client-ip=140.211.169.12; Authentication-Results: mx.google.com; spf=pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 2EB90E5C0; Tue, 12 Feb 2019 20:56:36 +0000 (UTC) Date: Tue, 12 Feb 2019 12:56:35 -0800 From: Andrew Morton To: Michal Hocko Cc: Tetsuo Handa , David Rientjes , Johannes Weiner , Linus Torvalds , Yong-Taek Lee , , LKML , Michal Hocko , Tetsuo Handa Subject: Re: [PATCH] proc, oom: do not report alien mms when setting oom_score_adj Message-Id: <20190212125635.27742b5741e92a0d47690c53@linux-foundation.org> In-Reply-To: <20190212102129.26288-1-mhocko@kernel.org> References: <20190212102129.26288-1-mhocko@kernel.org> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Tue, 12 Feb 2019 11:21:29 +0100 Michal Hocko wrote: > Tetsuo has reported that creating a thousands of processes sharing MM > without SIGHAND (aka alien threads) and setting > /proc//oom_score_adj will swamp the kernel log and takes ages [1] > to finish. This is especially worrisome that all that printing is done > under RCU lock and this can potentially trigger RCU stall or softlockup > detector. > > The primary reason for the printk was to catch potential users who might > depend on the behavior prior to 44a70adec910 ("mm, oom_adj: make sure > processes sharing mm have same view of oom_score_adj") but after more > than 2 years without a single report I guess it is safe to simply remove > the printk altogether. > > The next step should be moving oom_score_adj over to the mm struct and > remove all the tasks crawling as suggested by [2] > > [1] http://lkml.kernel.org/r/97fce864-6f75-bca5-14bc-12c9f890e740@i-love.sakura.ne.jp > [2] http://lkml.kernel.org/r/20190117155159.GA4087@dhcp22.suse.cz I think I'll put a cc:stable on this. Deleting a might-trigger debug printk is safe and welcome.