Re: Debugging Thinkpad T430s occasional suspend failure.

[Hugh Dickins <hughd@google.com>]

On Tue, 12 Feb 2013, Dave Jones wrote:

> My Thinkpad T430s suspend/resumes fine most of the time. But every so often
> (like one in ten times or so), as soon as I suspend, I get a black screen,
> and a blinking power button.
> 
> (Note: Not the capslock lights like when we panic, this laptop 'conveniently
>  doesn't have those. This is the light surrounding the power button, which afaik
>  isn't even OS controlled, so maybe we're dying somewhere in SMI/BIOS land?)

Me too on T420s, except that is blessed with a blinking CapsLk.

It's so erratic (though I think I see more failures than you do: I'd say
a quick resume never fails, but an overnight resume fails half the time):
I'm afraid I didn't have the patience to embark on pm_trace at all.

I did try to bisect it during the -rc5 week.  I'm not sure, but I have
no record of seeing it on -rc1 or -rc2, but definitely saw it on -rc3.
So I tried bisecting between -rc2 and -rc3, persisting for a day if it
looked good; but the bisection didn't seem to be converging anywhere
likely when -rc6 came out, and I switched to see if -rc6 solved it.

I had no problem with -rc6; but with -rc7 it happens more than ever.
Though still not on "quick" resumes, the kind you want to do when
bisecting.

Sharing these anecdotes in case they match or diverge from your
experience and others, and might help towards finding the cause.
Not-to-be-trusted bisection log appended: of course the bads are
reliable, but perhaps none of the goods.

Hugh

> 
> I tried debugging this with pm_trace, which told me..
> 
> [    4.576035]   Magic number: 0:455:740
> [    4.576037]   hash matches drivers/base/power/main.c:645
> 
> Which points me at..
> 
>  642  Complete:
>  643         complete_all(&dev->power.completion);
>  644 
>  645         TRACE_RESUME(error);
>  646 
>  647         return error;
>  648 }
> 
> The only thing interesting here I think is that this is the resume path.
> So perhaps something failed to suspend, and we tried to back out of suspending,
> but something was too screwed up to abort cleanly ?
> 
> I've tried hooking up a serial console, and even tried console_noblank, 
> which yielded no additional info at all. (I'm guessing the consoles are suspended
> at the time of panic)
> 
> I also tried unloading all the modules I have loaded before the suspend, which
> seemed to reduce the chances of it happening, but eventually it reoccurred.
> 
> Any ideas on how I can further debug this ?
> 
> 	Dave

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