From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E3EAC433DF for ; Mon, 6 Jul 2020 13:34:39 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1B9C720702 for ; Mon, 6 Jul 2020 13:34:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1B9C720702 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 933436B0005; Mon, 6 Jul 2020 09:34:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8E1FA6B000E; Mon, 6 Jul 2020 09:34:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7D0956B0010; Mon, 6 Jul 2020 09:34:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0121.hostedemail.com [216.40.44.121]) by kanga.kvack.org (Postfix) with ESMTP id 6656D6B0005 for ; Mon, 6 Jul 2020 09:34:38 -0400 (EDT) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id DFC66180AD807 for ; Mon, 6 Jul 2020 13:34:37 +0000 (UTC) X-FDA: 77007745794.30.fall81_100c58126eac Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin30.hostedemail.com (Postfix) with ESMTP id BCA53180B3C8B for ; Mon, 6 Jul 2020 13:34:37 +0000 (UTC) X-HE-Tag: fall81_100c58126eac X-Filterd-Recvd-Size: 3227 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Mon, 6 Jul 2020 13:34:36 +0000 (UTC) IronPort-SDR: pczSgLUU7cSXtdulhErsUHfzRLlV6DS7VIfkASTXbEPXnlgemygyfKtMIXmb/uNZb2FFpRF77+ dCek+dlaTGQw== X-IronPort-AV: E=McAfee;i="6000,8403,9673"; a="232263069" X-IronPort-AV: E=Sophos;i="5.75,320,1589266800"; d="scan'208";a="232263069" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jul 2020 06:34:35 -0700 IronPort-SDR: uza9DKlu1Z8lPzS8c68lYnD2oxSCVKGcigfaAZ2U+t+swpOmjFFQIY5mca5nC3svAa256Qkl3u CSNECqWL3ImQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,320,1589266800"; d="scan'208";a="483134004" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.7.201.21]) by fmsmga005.fm.intel.com with ESMTP; 06 Jul 2020 06:34:34 -0700 Received: by tassilo.localdomain (Postfix, from userid 1000) id 76DF1301BE3; Mon, 6 Jul 2020 06:34:34 -0700 (PDT) Date: Mon, 6 Jul 2020 06:34:34 -0700 From: Andi Kleen To: Feng Tang Cc: Qian Cai , Andrew Morton , Dennis Zhou , Tejun Heo , Christoph Lameter , kernel test robot , Michal Hocko , Johannes Weiner , Matthew Wilcox , Mel Gorman , Kees Cook , Luis Chamberlain , Iurii Zaikin , tim.c.chen@intel.com, dave.hansen@intel.com, ying.huang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, lkp@lists.01.org Subject: Re: [mm] 4e2c82a409: ltp.overcommit_memory01.fail Message-ID: <20200706133434.GA3483883@tassilo.jf.intel.com> References: <20200705044454.GA90533@shbuild999.sh.intel.com> <20200705125854.GA66252@shbuild999.sh.intel.com> <20200705155232.GA608@lca.pw> <20200706014313.GB66252@shbuild999.sh.intel.com> <20200706023614.GA1231@lca.pw> <20200706132443.GA34488@shbuild999.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200706132443.GA34488@shbuild999.sh.intel.com> X-Rspamd-Queue-Id: BCA53180B3C8B X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: > ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); > - if (ret == 0 && write) > + if (ret == 0 && write) { > + if (sysctl_overcommit_memory == OVERCOMMIT_NEVER) > + schedule_on_each_cpu(sync_overcommit_as); The schedule_on_each_cpu is not atomic, so the problem could still happen in that window. I think it may be ok if it eventually resolves, but certainly needs a comment explaining it. Can you do some stress testing toggling the policy all the time on different CPUs and running the test on other CPUs and see if the test fails? The other alternative would be to define some intermediate state for the sysctl variable and only switch to never once the schedule_on_each_cpu returned. But that's more complexity. -Andi