From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752573AbbEHFYL (ORCPT ); Fri, 8 May 2015 01:24:11 -0400 Received: from mail-ig0-f180.google.com ([209.85.213.180]:35102 "EHLO mail-ig0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752477AbbEHFYI (ORCPT ); Fri, 8 May 2015 01:24:08 -0400 Date: Thu, 7 May 2015 22:24:04 -0700 From: Dmitry Torokhov To: Doug Anderson Cc: wim@iguana.be, linux@roeck-us.net, jszhang@marvell.com, linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/2] watchdog: dw_wdt: keepalive the watchdog at write time Message-ID: <20150508052404.GB18159@dtor-ws> References: <1431059265-9204-1-git-send-email-dianders@chromium.org> <1431059265-9204-2-git-send-email-dianders@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1431059265-9204-2-git-send-email-dianders@chromium.org> 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 Thu, May 07, 2015 at 09:27:45PM -0700, Doug Anderson wrote: > If you've got code that does this in a tight loop > 1. Open watchdog > 2. Send 'expect close' > 3. Close watchdog > ...you'll eventually trigger a watchdog reset. You can reproduce this > by using daisydog (1) and running: > while true; do daisydog -c > /dev/null; done > > The problem is that each time you write to the watchdog for 'expect > close' it moves the timer .5 seconds out. The timer thus never fires > and never pats the watchdog for you. > > 1: http://git.chromium.org/gitweb/?p=chromiumos/third_party/daisydog.git > > Signed-off-by: Doug Anderson > Reviewed-by: Guenter Roeck > Tested-by: Jisheng Zhang Reviewed-by: Dmitry Torokhov > --- > Changes in v2: None > > drivers/watchdog/dw_wdt.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c > index a284abd..6ea0634 100644 > --- a/drivers/watchdog/dw_wdt.c > +++ b/drivers/watchdog/dw_wdt.c > @@ -215,6 +215,7 @@ static ssize_t dw_wdt_write(struct file *filp, const char __user *buf, > } > > dw_wdt_set_next_heartbeat(); > + dw_wdt_keepalive(); > mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); > > return len; > -- > 2.2.0.rc0.207.ga3a616c > -- Dmitry