Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935862Ab3DHTvJ (ORCPT ); Mon, 8 Apr 2013 15:51:09 -0400 Received: from mail-oa0-f47.google.com ([209.85.219.47]:40012 "EHLO mail-oa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935775Ab3DHTvH (ORCPT ); Mon, 8 Apr 2013 15:51:07 -0400 Message-ID: <51631FA8.10905@linaro.org> Date: Mon, 08 Apr 2013 12:51:04 -0700 From: John Stultz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: Prarit Bhargava CC: Rik van Riel , linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH] hrtimer, add expiry time overflow check in hrtimer_interrupt References: <1365425235-26191-1-git-send-email-prarit@redhat.com> <5162D9D4.7010500@redhat.com> In-Reply-To: <5162D9D4.7010500@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1637 Lines: 47 On 04/08/2013 07:53 AM, Rik van Riel wrote: > On 04/08/2013 08:47 AM, Prarit Bhargava wrote: > >> When we change the system time to a low value like this, the value of >> timekeeper->offs_real will be a negative value. >> >> It seems that the WARN occurs because an hrtimer has been started in >> the time >> between the releasing of the timekeeper lock and the IPI call (via a >> call to >> on_each_cpu) in clock_was_set() in the do_settimeofday() code. The >> end result >> is that a REALTIME_CLOCK timer has been added with softexpires = >> expires = >> KTIME_MAX. The hrtimer_interrupt() fires/is called and the loop at >> kernel/hrtimer.c:1289 is executed. In this loop the code subtracts the >> clock base's offset (which was set to timekeeper->offs_real in >> do_settimeofday()) from the current hrtimer_cpu_base->expiry value >> (which >> was KTIME_MAX): >> >> KTIME_MAX - (a negative value) = overflow >> >> A simple check for an overflow can resolve this problem. Using >> KTIME_MAX >> instead of the overflow value will result in the hrtimer function >> being run, >> and the reprogramming of the timer after that. > > >> Signed-off-by: Prarit Bhargava >> Cc: Thomas Gleixner >> Cc: John Stultz > > Reviewed-by: Rik van Riel > Queued in my fortglx/3.10/time branch. thanks -john -- 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/