From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932089AbbFHPMH (ORCPT ); Mon, 8 Jun 2015 11:12:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59653 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752141AbbFHPL6 (ORCPT ); Mon, 8 Jun 2015 11:11:58 -0400 Date: Mon, 8 Jun 2015 17:10:59 +0200 From: Oleg Nesterov To: Peter Zijlstra Cc: umgwanakikbuti@gmail.com, mingo@elte.hu, ktkhai@parallels.com, rostedt@goodmis.org, tglx@linutronix.de, juri.lelli@gmail.com, pang.xunlei@linaro.org, wanpeng.li@linux.intel.com, linux-kernel@vger.kernel.org Subject: [PATCH 1/3] hrtimer: kill HRTIMER_STATE_MIGRATE, fix the race with hrtimer_is_queued() Message-ID: <20150608151059.GB23138@redhat.com> References: <20150605084836.364306429@infradead.org> <20150605085205.723058588@infradead.org> <20150607223317.GA5193@redhat.com> <20150608091417.GM19282@twins.programming.kicks-ass.net> <20150608141709.GX18673@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150608141709.GX18673@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org migrate_hrtimer_list() sets HRTIMER_STATE_MIGRATE to avoid the race with hrtimer_active(), but this can't avoid the same race with hrtimer_is_queued(). Kill HRTIMER_STATE_MIGRATE, we can simply use STATE_ENQUEUED. --- include/linux/hrtimer.h | 6 +----- kernel/time/hrtimer.c | 7 ++----- 2 files changed, 3 insertions(+), 10 deletions(-) diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 05f6df1..44810bc 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -70,17 +70,13 @@ enum hrtimer_restart { * the handling of the timer. * * The HRTIMER_STATE_ENQUEUED bit is always or'ed to the current state - * to preserve the HRTIMER_STATE_CALLBACK in the above scenario. This - * also affects HRTIMER_STATE_MIGRATE where the preservation is not - * necessary. HRTIMER_STATE_MIGRATE is cleared after the timer is - * enqueued on the new cpu. + * to preserve the HRTIMER_STATE_CALLBACK in the above scenario. * * All state transitions are protected by cpu_base->lock. */ #define HRTIMER_STATE_INACTIVE 0x00 #define HRTIMER_STATE_ENQUEUED 0x01 #define HRTIMER_STATE_CALLBACK 0x02 -#define HRTIMER_STATE_MIGRATE 0x04 /** * struct hrtimer - the basic hrtimer structure diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 76d4bd9..005fd44 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1640,11 +1640,11 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base, debug_deactivate(timer); /* - * Mark it as STATE_MIGRATE not INACTIVE otherwise the + * Mark it as ENQUEUED not INACTIVE otherwise the * timer could be seen as !active and just vanish away * under us on another CPU */ - __remove_hrtimer(timer, old_base, HRTIMER_STATE_MIGRATE, 0); + __remove_hrtimer(timer, old_base, HRTIMER_STATE_ENQUEUED, 0); timer->base = new_base; /* * Enqueue the timers on the new cpu. This does not @@ -1655,9 +1655,6 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base, * event device. */ enqueue_hrtimer(timer, new_base); - - /* Clear the migration state bit */ - timer->state &= ~HRTIMER_STATE_MIGRATE; } } -- 1.5.5.1