From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750794AbWH3J7d (ORCPT ); Wed, 30 Aug 2006 05:59:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750767AbWH3J7d (ORCPT ); Wed, 30 Aug 2006 05:59:33 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:14273 "EHLO ogre.sisk.pl") by vger.kernel.org with ESMTP id S1750794AbWH3J7c (ORCPT ); Wed, 30 Aug 2006 05:59:32 -0400 From: "Rafael J. Wysocki" To: Andrew Morton Subject: Re: [PATCH -mm] PM: Add pm_trace switch Date: Wed, 30 Aug 2006 12:02:59 +0200 User-Agent: KMail/1.9.3 Cc: LKML , Pavel Machek , Greg KH References: <200608291309.57404.rjw@sisk.pl> <20060829134648.451971a1.akpm@osdl.org> In-Reply-To: <20060829134648.451971a1.akpm@osdl.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200608301202.59300.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 29 August 2006 22:46, Andrew Morton wrote: > On Tue, 29 Aug 2006 13:09:57 +0200 > "Rafael J. Wysocki" wrote: > > > +int pm_trace_enabled; > > + > > +static ssize_t pm_trace_show(struct subsystem * subsys, char * buf) > > +{ > > + return sprintf(buf, "%d\n", pm_trace_enabled); > > +} > > + > > +static ssize_t > > +pm_trace_store(struct subsystem * subsys, const char * buf, size_t n) > > +{ > > + int val; > > + > > + if (sscanf(buf, "%d", &val) == 1) { > > + pm_trace_enabled = !!val; > > + return n; > > + } > > + return -EINVAL; > > +} > > + > > +power_attr(pm_trace); > > Well, this is the most difficult part. ;-) Signed-off-by: Rafael J. Wysocki --- Documentation/power/interface.txt | 15 +++++++++++++++ 1 file changed, 15 insertions(+) Index: linux-2.6.18-rc4-mm3/Documentation/power/interface.txt =================================================================== --- linux-2.6.18-rc4-mm3.orig/Documentation/power/interface.txt 2006-06-18 03:49:35.000000000 +0200 +++ linux-2.6.18-rc4-mm3/Documentation/power/interface.txt 2006-08-30 11:59:31.000000000 +0200 @@ -52,3 +52,18 @@ suspend image will be as small as possib Reading from this file will display the current image size limit, which is set to 500 MB by default. + +/sys/power/pm_trace controls the code which saves the last PM event point in +the RTC across reboots, so that you can debug a machine that just hangs +during suspend (or more commonly, during resume). Namely, the RTC is only +used to save the last PM event point if this file contains '1'. Initially it +contains '0' which may be changed to '1' by writing a string representing a +nonzero integer into it. + +To use this debugging feature you should attempt to suspend the machine, then +reboot it and run + + dmesg -s 1000000 | grep 'hash matches' + +CAUTION: Using it will cause your machine's real-time (CMOS) clock to be +set to a random invalid time after a resume.