From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qa0-f52.google.com (mail-qa0-f52.google.com [209.85.216.52]) by kanga.kvack.org (Postfix) with ESMTP id 9957C6B0035 for ; Tue, 29 Jul 2014 11:39:27 -0400 (EDT) Received: by mail-qa0-f52.google.com with SMTP id j15so9464324qaq.39 for ; Tue, 29 Jul 2014 08:39:27 -0700 (PDT) Received: from qmta12.emeryville.ca.mail.comcast.net (qmta12.emeryville.ca.mail.comcast.net. [2001:558:fe2d:44:76:96:27:227]) by mx.google.com with ESMTPS id u3si38363211qge.31.2014.07.29.08.39.26 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 29 Jul 2014 08:39:26 -0700 (PDT) Date: Tue, 29 Jul 2014 10:39:03 -0500 (CDT) From: Christoph Lameter Subject: Re: vmstat: On demand vmstat workers V8 In-Reply-To: <20140729151415.GF4791@htj.dyndns.org> Message-ID: References: <53D31101.8000107@oracle.com> <20140729075637.GA19379@twins.programming.kicks-ass.net> <20140729120525.GA28366@mtj.dyndns.org> <20140729122303.GA3935@laptop> <20140729131226.GS7462@htj.dyndns.org> <20140729151415.GF4791@htj.dyndns.org> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Peter Zijlstra , Sasha Levin , akpm@linux-foundation.org, Gilad Ben-Yossef , Thomas Gleixner , John Stultz , Mike Frysinger , Minchan Kim , Hakan Akkan , Max Krasnyansky , Frederic Weisbecker , "Paul E. McKenney" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, hughd@google.com, viresh.kumar@linaro.org, hpa@zytor.com, mingo@kernel.org, Lai Jiangshan On Tue, 29 Jul 2014, Tejun Heo wrote: > Hmmm, well, then it's something else. Either a bug in workqueue or in > the caller. Given the track record, the latter is more likely. > e.g. it looks kinda suspicious that the work func is cleared after > cancel_delayed_work_sync() is called. What happens if somebody tries > to schedule it inbetween? Here is yet another patch to also address this idea: Subject: vmstat: Clear the work.func before cancelling delayed work Looks strange to me but Tejun thinks this could do some good. If this really is the right thing to do then cancel_delayed_work should zap the work func itselt I think. Signed-off-by: Christoph Lameter Index: linux/mm/vmstat.c =================================================================== --- linux.orig/mm/vmstat.c 2014-07-29 10:22:45.073884943 -0500 +++ linux/mm/vmstat.c 2014-07-29 10:34:45.083369228 -0500 @@ -1277,8 +1277,8 @@ static int vmstat_cpuup_callback(struct break; case CPU_DOWN_PREPARE: case CPU_DOWN_PREPARE_FROZEN: - cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu)); per_cpu(vmstat_work, cpu).work.func = NULL; + cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu)); break; case CPU_DOWN_FAILED: case CPU_DOWN_FAILED_FROZEN: -- 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