Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753547AbbFHPOj (ORCPT ); Mon, 8 Jun 2015 11:14:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45250 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752457AbbFHPOc (ORCPT ); Mon, 8 Jun 2015 11:14:32 -0400 Date: Mon, 8 Jun 2015 17:13:33 +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: Re: [PATCH 1/3] hrtimer: kill HRTIMER_STATE_MIGRATE, fix the race with hrtimer_is_queued() Message-ID: <20150608151333.GF23138@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> <20150608151059.GB23138@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150608151059.GB23138@redhat.com> 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 Content-Length: 2683 Lines: 75 Sorry, for double/wrong posting. Please ignore this one, I've resent it in reply to 0/3. On 06/08, Oleg Nesterov wrote: > > 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 > -- 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/