linux-kernel - [REGRESSION] Black screen after switching desktop session (was: Re: Linux 4.10-rc5)

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Date:   Wed, 25 Jan 2017 13:10:26 +0100
From:   Martin Steigerwald <martin@...htvoll.de>
To:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Intel Gfx Mailing List <intel-gfx@...edesktop.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>
Subject: [REGRESSION] Black screen after switching desktop session (was: Re: Linux 4.10-rc5)

Am Sonntag, 22. Januar 2017, 13:32:08 CET schrieb Linus Torvalds:
> Things seem to be calming down a bit, and everything looks nominal.
> 
> There's only been about 250 changes (not counting merges) in the last
> week, and the diffstat touches less than 300 files (with drivers and
> architecture updates being the bulk, but there's tooling, networking
> and filesystems in there too).
> 
> So keep testing, and I think we'll have a regular release schedule.

Testing this is no fun:

Bug 99533 - black screen after switching session
https://bugs.freedesktop.org/99533

This after GPU hang/lockups with Kernel 4.9 reported as for example:

Bug 98922 - [snb] GPU hang on PlaneShift
https://bugs.freedesktop.org/98922

Which may be a duplicate of #98747, #98794, #98860, #98891, #98288.

I am back at kernel 4.8.15 as I need this machine for production work.

Sometimes I wish for a microkernel that might be able to reincarnate drivers 
that hang or do wierd things like that. That may at least give a way to 
actually do some debugging or even get the desktop session back without 
loosing its state. Especially for graphics drivers and hibernating/resuming 
from hibernations which also occasionally fails – again without leaving a way 
to interact with the machine to do further debugging. Linux kernel usually 
just crashes completely, not even a ping or ssh possible, or it at least stuck 
with a black display without any way to restart the graphics driver cause it 
seems to be in some undefined state. Combined with occasionally happening bugs 
this makes triaging bugs time consuming and risky. I do like to help testing, 
but maybe its time to just switch to distro kernels and be done about it, as I 
regularily come across bugs that are too expensive for me to triage.

Please understand that I am not willing to bisect these occasionally happening 
bugs with have the potential to cause data loss due to having to switch off 
the machine forcefully. Fortunately at least KMail saves a mail I write from 
time to time and also Kate does swap files.

I am also a bit unwilling to do further debugging of this one as I usually use 
two sessions when I am at work and I risk loosing data I work on. But… at 
least with this issue it seems I would have a way to SSH into the machine 
before kicking it.

I am dissatisfied with the state of the Intel graphics driver on this ThinkPad 
T520 with Sandybridge since kernel 4.9 and wonder whether you guys at Intel 
really test things with older hardware versions.

Thanks,
-- 
Martin