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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 8845EC19759 for ; Thu, 1 Aug 2019 18:41:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 669132080C for ; Thu, 1 Aug 2019 18:41:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732408AbfHASlg (ORCPT ); Thu, 1 Aug 2019 14:41:36 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:37660 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727899AbfHASlf (ORCPT ); Thu, 1 Aug 2019 14:41:35 -0400 Received: from pd9ef1cb8.dip0.t-ipconnect.de ([217.239.28.184] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1htG0x-0007Ns-FW; Thu, 01 Aug 2019 20:41:23 +0200 Date: Thu, 1 Aug 2019 20:41:22 +0200 (CEST) From: Thomas Gleixner To: Oleg Nesterov cc: LKML , x86@kernel.org, Peter Zijlstra , Ingo Molnar , Sebastian Siewior , Anna-Maria Gleixner , Steven Rostedt , Julia Cartwright , Paul McKenney , Frederic Weisbecker , John Stultz , Andy Lutomirski , "Paul E. McKenney" , kvm@vger.kernel.org, Radim Krcmar , Paolo Bonzini Subject: Re: [patch 4/5] posix-cpu-timers: Defer timer handling to task_work In-Reply-To: <20190801153936.GD31538@redhat.com> Message-ID: References: <20190801143250.370326052@linutronix.de> <20190801143658.074833024@linutronix.de> <20190801153936.GD31538@redhat.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 1 Aug 2019, Oleg Nesterov wrote: > On 08/01, Thomas Gleixner wrote: > > > > +static void __run_posix_cpu_timers(struct task_struct *tsk) > > +{ > > + /* FIXME: Init it proper in fork or such */ > > + init_task_work(&tsk->cpu_timer_work, posix_cpu_timers_work); > > + task_work_add(tsk, &tsk->cpu_timer_work, true); > > +} > > What if update_process_times/run_posix_cpu_timers is called again before > this task does task_work_run() ? > > somehow it should check that ->cpu_timer_work is not already queued... Right. > Or suppose that this is called when task_work_run() executes this > cpu_timer_work. Looks like you need another flag checked by > __run_posix_cpu_timers() and cleare in posix_cpu_timers_work() ? That's a non issue. The only thing which can happen is that it runs through the task_work once more to figure out there is nothing to do. Thanks, tglx