Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753953AbbFIVko (ORCPT ); Tue, 9 Jun 2015 17:40:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49744 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752119AbbFIVkg (ORCPT ); Tue, 9 Jun 2015 17:40:36 -0400 Date: Tue, 9 Jun 2015 23:39:35 +0200 From: Oleg Nesterov To: Peter Zijlstra Cc: umgwanakikbuti@gmail.com, mingo@elte.hu, ktkhai@parallels.com, rostedt@goodmis.org, tglx@linutronix.de, juri.lelli@gmail.com, pang.xunlei@linaro.org, wanpeng.li@linux.intel.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 08/14] hrtimer: Allow hrtimer::function() to free the timer Message-ID: <20150609213935.GA14225@redhat.com> References: <20150605084836.364306429@infradead.org> <20150605085205.723058588@infradead.org> <20150607223317.GA5193@redhat.com> <20150608091417.GM19282@twins.programming.kicks-ass.net> <20150608124234.GW18673@twins.programming.kicks-ass.net> <20150609213318.GA12436@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150609213318.GA12436@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 769 Lines: 24 Damn, On 06/09, Oleg Nesterov wrote: > > Yes, we only have this 2nd write_seqcount_begin/end if the timer re- > arms itself, but otherwise we do not race. If another thread does > hrtime_start() in between we can pretend that hrtimer_active() hits > the "inactive". ^^^^^^^^^^^^^^^ I meant, hits the "inactive" window we can't avoid. Even if another thread does this _before_ __run_hrtimer() clears ->running, we can't distinguish from the case when it does this right _after_ the timer becomes "inactive". Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/