On Saturday, January 22, 2011, Linus Torvalds wrote:
> On Sat, Jan 22, 2011 at 7:11 AM, Linus Torvalds
> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > Hmm. I can certainly believe in the "BIOS is confused" idea, but I
> > don't see where that gets us.
>
> So, trying to get some more hints in what is going on, I started
> getting creative, and I have a few more clues, I think.
>
> First off, I think I've already noted that I don't think I get lockups
> with the usual "echo mem > /sys/power/state". So I've mentioned that
> maybe it's something about the lid event messing things up.
>
> However, I figured out that I _can_ trigger the lockup from the
> command line, by using "pm-suspend" instead. So while the normal
> (well, normal for me, since it's the "real kernel interface", not
> normal in general) "echo mem" thing seems stable, it doesn't seem like
> it's the lid event per se that confuses anything, and it seems that
> it's just that the lid event uses "pm-suspend" which runs all those
> hacky scripts just before suspending.
>
> I also _think_ (and this is where it gets a bit speculative, because
> my trials so far have been pretty limited) that I can work around the
> problem by doing that "echo mem" suspend once, and after that the
> "pm-suspend" approach works.
>
> IOW, the whole "it fails the first time after boot" does seem to hold
> true, and there seems to be some initialization issue. But the
> initialization issue is apparently _triggered_ by the pm-suspend
> scripts.
>
> Personally, I'm inclined to blame the crazy fbdev/video save/restore
> code, and I'm hereby adding some of the i915 people to the mix.
> Because one of the main things that the pm-suspend scripts do is
> things like
>
> local con
> for con in /sys/class/graphics/*/state; do
> [ -f $con ] || continue
> echo 1 >"${con}"
> done
>
> etc. I disabled that particular part (all of "99video" in fedora, in
> fact), but there are other strange things going on there.
>
> Of course, it could be all the NetworkManager stuff too, and some
> interaction with the network drivers. But the lockup happens with both
> wired and wireless connections, so I don't think that's it.
>
> I wonder what else differs between pm-suspend and just the final "echo
> mem"? But I do wonder if some of the i915 code is getting confused by
> being touched both as fbcon and then with the "real" suspend code..
Hmm. If there is s2ram on your system and it's actually being used, it's
better to disable it completely. I'm not sure how you are supposed to do
that on Fedora, but for openSUSE it's sufficient to clear the "executable" bit
on /usr/sbin/s2ram.
Rafael
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