Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933903Ab3CLXKS (ORCPT ); Tue, 12 Mar 2013 19:10:18 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:60227 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755862Ab3CLWdF (ORCPT ); Tue, 12 Mar 2013 18:33:05 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Frederic Weisbecker , Peter Zijlstra , Ingo Molnar , Linus Torvalds , Thomas Gleixner Subject: [ 038/100] nohz: Make tick_nohz_irq_exit() irq safe Date: Tue, 12 Mar 2013 15:31:23 -0700 Message-Id: <20130312223127.097863883@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.rc1.5.g7e0651a In-Reply-To: <20130312223122.884099393@linuxfoundation.org> References: <20130312223122.884099393@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2429 Lines: 73 3.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Frederic Weisbecker commit e5ab012c3271990e8457055c25cafddc1ae8aa6b upstream. As it stands, irq_exit() may or may not be called with irqs disabled, depending on __ARCH_IRQ_EXIT_IRQS_DISABLED that the arch can define. It makes tick_nohz_irq_exit() unsafe. For example two interrupts can race in tick_nohz_stop_sched_tick(): the inner most one computes the expiring time on top of the timer list, then it's interrupted right before reprogramming the clock. The new interrupt enqueues a new timer list timer, it reprogram the clock to take it into account and it exits. The CPUs resumes the inner most interrupt and performs the clock reprogramming without considering the new timer list timer. This regression has been introduced by: 280f06774afedf849f0b34248ed6aff57d0f6908 ("nohz: Separate out irq exit and idle loop dyntick logic") Let's fix it right now with the appropriate protections. A saner long term solution will be to remove __ARCH_IRQ_EXIT_IRQS_DISABLED and mandate that irq_exit() is called with interrupts disabled. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1361373336-11337-1-git-send-email-fweisbec@gmail.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- kernel/time/tick-sched.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -564,14 +564,19 @@ void tick_nohz_idle_enter(void) */ void tick_nohz_irq_exit(void) { + unsigned long flags; struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); if (!ts->inidle) return; - /* Cancel the timer because CPU already waken up from the C-states*/ + local_irq_save(flags); + + /* Cancel the timer because CPU already waken up from the C-states */ menu_hrtimer_cancel(); __tick_nohz_idle_enter(ts); + + local_irq_restore(flags); } /** -- 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/