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Date: Mon, 31 Oct 2005 12:42:17 -0800
From: Ashok Raj <ashok.raj@intel.com>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org,
       Ashok Raj <ashok.raj@intel.com>, Dave Jones <davej@codemonkey.org.uk>,
       Ingo Molnar <mingo@elte.hu>, linux@brodo.de
Subject: Re: 2.6.14-git3: scheduling while atomic from cpufreq on Athlon64
Message-ID: <20051031124216.A18213@unix-os.sc.intel.com>
References: <200510311606.36615.rjw@sisk.pl> <20051031113413.34a599cd.akpm@osdl.org> <200510312045.32908.rjw@sisk.pl>
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On Mon, Oct 31, 2005 at 08:45:32PM +0100, Rafael J. Wysocki wrote:
> On Monday, 31 of October 2005 20:34, Andrew Morton wrote:
> > "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
> }-- snip --{
> > > scheduling while atomic: swapper/0x00000001/1
> > > 
> > > Call Trace:<ffffffff8035014a>{schedule+122} <ffffffff802e2453>{cpufreq_frequency_table_target+371}
> > >        <ffffffff8011d60c>{powernowk8_target+1916} <ffffffff802dfdb4>{__cpufreq_driver_target+116}
> > >        <ffffffff801be269>{sysfs_new_dirent+41} <ffffffff802e097e>{cpufreq_governor_performance+62}
> > >        <ffffffff802dec8d>{__cpufreq_governor+173} <ffffffff802df417>{__cpufreq_set_policy+551}
> > >        <ffffffff802df5bf>{cpufreq_set_policy+79} <ffffffff802df946>{cpufreq_add_dev+806}
> > >        <ffffffff802df540>{handle_update+0} <ffffffff802ae21a>{sysdev_driver_register+170}
> > >        <ffffffff802df106>{cpufreq_register_driver+198} <ffffffff8010c122>{init+194}
> > >        <ffffffff8010f556>{child_rip+8} <ffffffff8010c060>{init+0}
> > >        <ffffffff8010f54e>{child_rip+0} 
> > 
> > Well I can't find it.  Ingo, didn't you have a debug patch which would help
> > us identify where this atomic section started?
> 
> This is 100% reproducible on my box so I'll try to figure out what's up tomorrow
> (unless someone else does it earlier ;-)).  Now I can only say it did not happen
> with 2.6.14-rc5-mm1.

This could be because of the new patch, i added preempt_disable() instead
of taking cpucontrol lock in __cpufreq_driver_target().

The reason is we now enter the same code path from the cpu_up() and cpu_down()
generated cpu notifier callbacks and ends up trying to lock when the 
call path already has the cpucontrol lock.

Its happening because we do set_cpus_allowed() in powernowk8_target().


> 
> > > Additionally there are some problems with freezing processes by swsusp.
> 
> Once the box has not suspended due to a process refusing to freeze, but I was
> unable to trace the problem at that time.  This does not seem to be readily
> reproducible, however.
> 
> Greetings,
> Rafael

-- 
Cheers,
Ashok Raj
- Open Source Technology Center
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