From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753079AbbFKMx6 (ORCPT ); Thu, 11 Jun 2015 08:53:58 -0400 Received: from casper.infradead.org ([85.118.1.10]:39629 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752301AbbFKMxu (ORCPT ); Thu, 11 Jun 2015 08:53:50 -0400 Message-Id: <20150611124743.175989138@infradead.org> User-Agent: quilt/0.61-1 Date: Thu, 11 Jun 2015 14:46:45 +0200 From: Peter Zijlstra To: umgwanakikbuti@gmail.com, mingo@elte.hu Cc: ktkhai@parallels.com, rostedt@goodmis.org, tglx@linutronix.de, juri.lelli@gmail.com, pang.xunlei@linaro.org, oleg@redhat.com, wanpeng.li@linux.intel.com, linux-kernel@vger.kernel.org, peterz@infradead.org Subject: [PATCH 09/18] hrtimer: Fix hrtimer_is_queued() hole References: <20150611124636.448700267@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-hrtimer-fix-restart.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A queued hrtimer that gets restarted (hrtimer_start*() while hrtimer_is_queued()) will briefly appear as unqueued/inactive, even though the timer has always been active, we just moved it. Close this hole by preserving timer->state in hrtimer_start_range_ns()'s remove_hrtimer() call. Reported-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) --- kernel/time/hrtimer.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -891,10 +891,10 @@ static void __remove_hrtimer(struct hrti * remove hrtimer, called with base lock held */ static inline int -remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base) +remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base, bool restart) { if (hrtimer_is_queued(timer)) { - unsigned long state; + unsigned long state = timer->state; int reprogram; /* @@ -908,12 +908,15 @@ remove_hrtimer(struct hrtimer *timer, st debug_deactivate(timer); timer_stats_hrtimer_clear_start_info(timer); reprogram = base->cpu_base == this_cpu_ptr(&hrtimer_bases); - /* - * We must preserve the CALLBACK state flag here, - * otherwise we could move the timer base in - * switch_hrtimer_base. - */ - state = timer->state & HRTIMER_STATE_CALLBACK; + + if (!restart) { + /* + * We must preserve the CALLBACK state flag here, + * otherwise we could move the timer base in + * switch_hrtimer_base. + */ + state &= HRTIMER_STATE_CALLBACK; + } __remove_hrtimer(timer, base, state, reprogram); return 1; } @@ -938,7 +941,7 @@ void hrtimer_start_range_ns(struct hrtim base = lock_hrtimer_base(timer, &flags); /* Remove an active timer from the queue: */ - remove_hrtimer(timer, base); + remove_hrtimer(timer, base, true); if (mode & HRTIMER_MODE_REL) { tim = ktime_add_safe(tim, base->get_time()); @@ -1007,7 +1010,7 @@ int hrtimer_try_to_cancel(struct hrtimer base = lock_hrtimer_base(timer, &flags); if (!hrtimer_callback_running(timer)) - ret = remove_hrtimer(timer, base); + ret = remove_hrtimer(timer, base, false); unlock_hrtimer_base(timer, &flags);