From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755115AbbA3Aaj (ORCPT ); Thu, 29 Jan 2015 19:30:39 -0500 Received: from v094114.home.net.pl ([79.96.170.134]:52918 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751609AbbA3Aai (ORCPT ); Thu, 29 Jan 2015 19:30:38 -0500 From: "Rafael J. Wysocki" To: Pavel Machek Cc: "Liu, Chuansheng" , "Fu, Zhonghui" , "Brown, Len" , Greg Kroah-Hartman , "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , trivial@kernel.org Subject: Re: Change behaviour when tracing ... nasty trap (was Re: [PATCH] PM/Trace: get rid of synchronous resume limit during PM trace) Date: Fri, 30 Jan 2015 01:53:25 +0100 Message-ID: <6553656.pcJl3UFpb6@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/3.16.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20150126134304.GA7889@amd> References: <54C5CB77.4000109@linux.intel.com> <2718950.eck1siDzqK@vostro.rjw.lan> <20150126134304.GA7889@amd> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, January 26, 2015 02:43:04 PM Pavel Machek wrote: > Document pm_tracing actually affecting suspend in non-trivial way. > > > Signed-off-by: Pavel Machek > > --- > > On Mon 2015-01-26 14:41:02, Rafael J. Wysocki wrote: > > On Monday, January 26, 2015 12:05:16 PM Pavel Machek wrote: > > > On Mon 2015-01-26 10:39:04, Liu, Chuansheng wrote: > > > > > > > @@ -517,8 +517,7 @@ static int device_resume_noirq(struct device *dev, > > > > > pm_message_t state, bool asyn > > > > > > > > > > > > static bool is_async(struct device *dev) > > > > > > { > > > > > > - return dev->power.async_suspend && pm_async_enabled > > > > > > - && !pm_trace_is_enabled(); > > > > > > + return dev->power.async_suspend && pm_async_enabled; > > > > > > } > > > > > > > > > > > > > > > > Actually... whoever did the original patch was evil person. Changing > > > > > behaviour when tracing is requested is evil, evil, evil. Git blame > > > > > tells me > > > > > > > > > > Signed-off-by: Chuansheng Liu > > > > > > > > > > went to the dark side. > > > > > > > > Although I didn't get where is something wrong, but the is_async() is not created by my commit, > > > > it is from commit (PM: Start asynchronous resume threads upfront), I just moved it ahead. > > > > > > > > And like other phases, I added it into resum/suspend_noirq()... > > > > > > I see, blame blamed wrong person. It looks like Rafael is evil: > > > > > > commit 97df8c12995c5bac73e3bfeea4c5be155c1f4401 > > > Author: Rafael J. Wysocki > > > Date: Sat Jan 23 22:25:31 2010 +0100 > > > > > > PM: Start asynchronous resume threads upfront > > > > This only means we won't use asyc suspend/resume at all when the RTC-based > > resume debug is enabled, because it wouldn't make sense (the RTC-based > > debug requires strict ordering of callbacks between devices or we may find > > that device A hanged the resume while actually device B that was running in > > parallel with A did that). > > > > And I shouldn't even need to explain this ... Sad. > > Well, I forgot that pm_trace_is_enabled() is the simple, RTC based > one, and believe it would be worth a comment... A comment won't hurt. :-) Applied, thanks! > diff --git a/Documentation/power/s2ram.txt b/Documentation/power/s2ram.txt > index 1bdfa04..4685aee 100644 > --- a/Documentation/power/s2ram.txt > +++ b/Documentation/power/s2ram.txt > @@ -69,6 +69,10 @@ Reason for this is that the RTC is the only reliably available piece of > hardware during resume operations where a value can be set that will > survive a reboot. > > +pm_trace is not compatible with asynchronous suspend, so it turns > +asynchronous suspend off (which may work around timing or > +ordering-sensitive bugs). > + > Consequence is that after a resume (even if it is successful) your system > clock will have a value corresponding to the magic number instead of the > correct date/time! It is therefore advisable to use a program like ntp-date > > > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.