From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: [RFC PATCH] drivers: power: Add watchdog timer to catch drivers which lockup during suspend. Date: Tue, 30 Apr 2013 21:17:31 -0700 Message-ID: <20130501041731.GA24128@kroah.com> References: <1367360914-23389-1-git-send-email-zoran.markovic@linaro.org> <20130430233031.GA32310@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-da0-f45.google.com ([209.85.210.45]:61751 "EHLO mail-da0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750899Ab3EAERg (ORCPT ); Wed, 1 May 2013 00:17:36 -0400 Received: by mail-da0-f45.google.com with SMTP id v40so530489dad.32 for ; Tue, 30 Apr 2013 21:17:35 -0700 (PDT) Content-Disposition: inline In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Colin Cross Cc: Zoran Markovic , lkml , Linux PM list , Benoit Goby , Android Kernel Team , Todd Poynor , San Mehat , John Stultz , Pavel Machek , "Rafael J. Wysocki" , Len Brown On Tue, Apr 30, 2013 at 08:36:21PM -0700, Colin Cross wrote: > On Tue, Apr 30, 2013 at 4:30 PM, Greg Kroah-Hartman > wrote: > > On Tue, Apr 30, 2013 at 03:28:33PM -0700, Zoran Markovic wrote: > >> From: Benoit Goby > >> > >> Below is a patch from android kernel that detects a driver suspend > >> lockup and captures dump in the kernel log. Please review and provide > >> comments. > > > > There's this really cool thing called a watchdog driver that does stuff > > like this :) > > If the watchdog driver worked in this case this patch wouldn't exist. Great, let's fix the watchdog timer then :) What's wrong with it? > >> Rather than hard-lock the kernel, dump the suspend thread stack and > >> BUG() when a driver takes too long to suspend. The timeout is set to > >> 12 seconds to be longer than the usbhid 10 second timeout. > >> > >> Exclude from the watchdog the time spent waiting for children that > >> are resumed asynchronously and time every device, whether or not they > >> resumed synchronously. > > > > No, don't add a driver-core-only timer, use the existing watchdog timers > > if you are worried about the kernel locking up. > > The watchdog timers are useless here. For one, they generally stop > when their driver suspend op is called, so you may not even have one > running when you lock up. But you can fix that, right? > More importantly, the purpose of this patch is to tell you which > driver locked up and hopefully why, and the watchdog driver will > usually result in a silent reset. I thought it was an option as to what the watchdog does when it triggers. > This patch will cause a stack trace of the driver suspend op that is > blocking suspend progress, even if that call does not happen in the > suspend thread. But who can see this, the machine is now dead. greg k-h