From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752455AbbKOHwt (ORCPT ); Sun, 15 Nov 2015 02:52:49 -0500 Received: from www.linutronix.de ([62.245.132.108]:35890 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751272AbbKOHws (ORCPT ); Sun, 15 Nov 2015 02:52:48 -0500 Date: Sun, 15 Nov 2015 08:52:08 +0100 (CET) From: Thomas Gleixner To: Linus Torvalds cc: LKML , Andrew Morton , Ingo Molnar , "H. Peter Anvin" Subject: [GIT pull] timer updates for 4.4 Message-ID: User-Agent: Alpine 2.11 (DEB 23 2013-08-11) 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus, please pull the latest timers-urgent-for-linus git tree from: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-urgent-for-linus A single fix for a long standing race versus timers scheduled on a target cpu which got exposed by recent changes in the workqueue implementation. Thanks, tglx ------------------> Tejun Heo (1): timers: Use proper base migration in add_timer_on() kernel/time/timer.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 74591ba9474f..bbc5d1114583 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -977,13 +977,29 @@ EXPORT_SYMBOL(add_timer); */ void add_timer_on(struct timer_list *timer, int cpu) { - struct tvec_base *base = per_cpu_ptr(&tvec_bases, cpu); + struct tvec_base *new_base = per_cpu_ptr(&tvec_bases, cpu); + struct tvec_base *base; unsigned long flags; timer_stats_timer_set_start_info(timer); BUG_ON(timer_pending(timer) || !timer->function); - spin_lock_irqsave(&base->lock, flags); - timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu; + + /* + * If @timer was on a different CPU, it should be migrated with the + * old base locked to prevent other operations proceeding with the + * wrong base locked. See lock_timer_base(). + */ + base = lock_timer_base(timer, &flags); + if (base != new_base) { + timer->flags |= TIMER_MIGRATING; + + spin_unlock(&base->lock); + base = new_base; + spin_lock(&base->lock); + WRITE_ONCE(timer->flags, + (timer->flags & ~TIMER_BASEMASK) | cpu); + } + debug_activate(timer, timer->expires); internal_add_timer(base, timer); spin_unlock_irqrestore(&base->lock, flags);