Re: 2.6.25-rc7/8: Another resume regression

From: Mark Lord
Date: Tue Apr 08 2008 - 11:35:20 EST


Rafael J. Wysocki wrote:
On Monday, 7 of April 2008, Mark Lord wrote:
Rafael J. Wysocki wrote:
On Saturday, 5 of April 2008, Mark Lord wrote:
Mark Lord wrote:
Hi,

Okay, USB now works fine on resume after fixing the iaa_watchdog issue.

But twice now, once before that fix, and again just a minute ago,
my machine has failed completely to resume after suspend-to-RAM.

Again, resume here is 100% reliable in 2.6.24 and earlier.

Symptoms: the usual:

-- 2.6.25-rc8 (and -rc7 earlier), plus USB fix.
-- not reproduceable on demand.
-- black screen of death -- no backlight, no kernel messages.
-- no hard drive activity.
-- no alt-sysrq-anything.
-- 5 second hold of the power button to poweroff and then recover.

Not much info to go on, but it's worth knowing there's an issue here somewhere.
..

Mmmm... Now that 2.6.25-rc* is usable here, there's another symptom
that's been happening regularly enough that it's got to be a regression
of some sort.

This machine has an ATI X1400 video card, which doesn't work with any
open source X server that I know of. Maybe latest RadeonHD would work
but it didn't when I tried it in January.

So I'm using the ATI binary fglrx X server, but without their kernel module,
so no 3D acceleration (fine.. only affects Google Earth, really).

Now.. on 2.6.25, after a suspend/resume cycle (or three), the framebuffer
frequently starts going wonky. "snowy" pixels appear, and stay.
Just a moment ago here, the entire background changed to zebra stripes.

And so on.. Peculiar stuff.

I'm wondering if something to do with video mode switching,
or video register save/restore, has changed since 2.6.24.
Because it's broken in 2.6.25, yet works fine in all earlier kernels.
Yes, that's probably related.

However, I'm unable to reproduce the breakage. If you can do that, it would
probably help a lot if you identified the commit causing that to happen.
..

Well, it would help then if you identified the commits which hacked
at the video mode switching. Then I can revert those and see what happens.
There's probably not many commits there, and since it doesn't do it consistently
(and sometimes the machine just doesn't resume at all with 2.6.25), it is tricky to bisect.

Works perfectly in 2.6.24, though, which is what I'm now running again.

I guess this is related to http://bugzilla.kernel.org/show_bug.cgi?id=10319 .

I have no idea what can cause that to happen. It apparently is not related to
CONFIG_DRM (that actually may help if you have an Intel graphics adapter),
so it looks like an ACPI issue.
..

Something's weird there. I poked at my suspend/resume script again this morning,
and discovered that it did have some vbetool hacks to deal with textmode on earlier
kernels.

So I wrapped those vbetool hacks with some logic to prevent them on 2.6.25,
and for now suspend/resume seem to be working with good video on -rc8.
It'll take a bit longer to know for sure, but by the end of today we'll see.

cheers
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