From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752702AbbEHJ03 (ORCPT ); Fri, 8 May 2015 05:26:29 -0400 Received: from terminus.zytor.com ([198.137.202.10]:45335 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752117AbbEHJ0Y (ORCPT ); Fri, 8 May 2015 05:26:24 -0400 Date: Fri, 8 May 2015 02:25:09 -0700 From: tip-bot for Thomas Gleixner Message-ID: Cc: linux-arm-kernel@lists.infradead.org, bp@alien8.de, linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, horms@verge.net.au, magnus.damm@gmail.com, peterz@infradead.org, tglx@linutronix.de Reply-To: linux-kernel@vger.kernel.org, hpa@zytor.com, bp@alien8.de, linux-arm-kernel@lists.infradead.org, tglx@linutronix.de, magnus.damm@gmail.com, peterz@infradead.org, horms@verge.net.au, mingo@kernel.org In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:timers/core] nohz: Fix !HIGH_RES_TIMERS hang Git-Commit-ID: 6b442bc81337913eb775965a67ffdb8a36935422 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 6b442bc81337913eb775965a67ffdb8a36935422 Gitweb: http://git.kernel.org/tip/6b442bc81337913eb775965a67ffdb8a36935422 Author: Thomas Gleixner AuthorDate: Thu, 7 May 2015 14:35:59 +0200 Committer: Ingo Molnar CommitDate: Thu, 7 May 2015 16:15:50 +0200 nohz: Fix !HIGH_RES_TIMERS hang Simon Horman reported this crash on a system with high-res timers disabled but nohz enabled: > ------------[ cut here ]------------ > kernel BUG at kernel/irq_work.c:135! BUG_ON(!irqs_disabled()); So something enabled interrupts in the periodic tick handling machinery, and that code path indeed has a local_irq_disable()/enable pair in tick_nohz_switch_to_nohz() which causes havoc. Fix it. This patch also fixes a +nohz -hrtimers hang reported by Ingo Molnar. Reported-by: Simon Horman Reported-by: Ingo Molnar Tested-by: Simon Horman Signed-off-by: Thomas Gleixner Cc: Borislav Petkov Cc: H. Peter Anvin Cc: LAK Cc: Magnus Damm Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1505071425520.4225@nanos Signed-off-by: Ingo Molnar --- kernel/time/tick-sched.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 753c211..812f7a3 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -967,11 +967,9 @@ static void tick_nohz_switch_to_nohz(void) if (!tick_nohz_enabled) return; - local_irq_disable(); - if (tick_switch_to_oneshot(tick_nohz_handler)) { - local_irq_enable(); + if (tick_switch_to_oneshot(tick_nohz_handler)) return; - } + tick_nohz_active = 1; ts->nohz_mode = NOHZ_MODE_LOWRES; @@ -986,7 +984,6 @@ static void tick_nohz_switch_to_nohz(void) hrtimer_forward_now(&ts->sched_timer, tick_period); hrtimer_set_expires(&ts->sched_timer, next); tick_program_event(next, 1); - local_irq_enable(); } /* @@ -1171,7 +1168,7 @@ void tick_oneshot_notify(void) * Called cyclic from the hrtimer softirq (driven by the timer * softirq) allow_nohz signals, that we can switch into low-res nohz * mode, because high resolution timers are disabled (either compile - * or runtime). + * or runtime). Called with interrupts disabled. */ int tick_check_oneshot_change(int allow_nohz) {