Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932522AbaGIWVo (ORCPT ); Wed, 9 Jul 2014 18:21:44 -0400 Received: from mail-we0-f178.google.com ([74.125.82.178]:42077 "EHLO mail-we0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932352AbaGIWVl (ORCPT ); Wed, 9 Jul 2014 18:21:41 -0400 Date: Thu, 10 Jul 2014 00:21:33 +0200 From: Frederic Weisbecker To: Viresh Kumar Cc: tglx@linutronix.de, linaro-kernel@lists.linaro.org, linux-kernel@vger.kernel.org, arvind.chauhan@arm.com, preeti@linux.vnet.ibm.com, khilman@linaro.org Subject: Re: [RFC 1/7] hrtimer: Warn if hrtimer_start*() failed to enqueue hrtimer Message-ID: <20140709222131.GD23881@localhost.localdomain> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 09, 2014 at 12:25:33PM +0530, Viresh Kumar wrote: > hrtimer_start*() family never fails to enqueue a hrtimer to a clock-base. The > only special case is when the hrtimer was in past. If it is getting enqueued to > local CPUs's clock-base, we raise a softirq and exit, else we handle that on > next interrupt on remote CPU. > > At several places in kernel we check if hrtimer is enqueued properly with > hrtimer_active(). This isn't required and can be dropped. > > Before fixing that, lets make sure hrtimer is always enqueued properly by adding > > WARN_ON_ONCE(!hrtimer_active(timer)); > > towards the end of __hrtimer_start_range_ns(). > > Suggested-by: Frederic Weisbecker > Signed-off-by: Viresh Kumar > --- > kernel/hrtimer.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c > index 3ab2899..cf40209 100644 > --- a/kernel/hrtimer.c > +++ b/kernel/hrtimer.c > @@ -1037,6 +1037,8 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, > > unlock_hrtimer_base(timer, &flags); > > + /* Make sure timer is enqueued */ > + WARN_ON_ONCE(!hrtimer_active(timer)); Hmm, after reading Thomas reply, I think it's possible that the hrtimer expires right after we unlock it and, if we are unlucky enough, before the hrtimer_active() check. In this case we might hit a false positive. > return ret; > } > EXPORT_SYMBOL_GPL(__hrtimer_start_range_ns); > -- > 2.0.0.rc2 > -- 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/