Comment 2 for bug 1168967
Revision history for this message
| Greg Ward (gward) wrote Re: regression: no video after upgrading kernel, mesa, libc, and several other packages (ThinkPad T500) | #2 |
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a60fb26
(Get the code!)
This is starting to look very much like a kernel bug, although I'm still confused about several things. My main evidence is that I'm having similar problems with System Rescue CD, a Gentoo-based rescue distro that boots from CD or USB stick.
In particular, System Rescue CD 3.4.1 (kernel 3.4.32) works fine, but System Rescue CD 3.4.2 (kernel 3.4.35) does not. "Works fine" means that during boot, it switches from 80x25 text mode to high-res text mode just fine -- I presume this is kernel video mode setting in action? But System Rescue CD 3.4.2 fails that mode switch: the screen just goes black. That's not the exact same manifestation as I'm seeing in Ubuntu, but of course Ubuntu and System Rescue CD have different boot procedures.
More data points:
* if I boot System Rescue CD 3.4.2 (kernel 3.4.35) using its "framebuffer console in high resolution" option, everything is fine (although X is painfully slow)
* if I boot System Rescue CD 3.4.2 using its "alt kernel" option (kernel 3.7.10), everything works fine
Summary:
* I'm seeing similar behaviour in two different distros (Ubuntu 12.10 and System Rescue CD 3.4.2)
* I can dodge the bug with System Rescue CD either by a) using framebuffer console or b) booting a newer kernel
This makes me strongly suspect that it's a kernel bug, specifically related to kernel video mode setting.
The one thing that I don't understand: why is the bug still there if I boot an older Ubuntu kernel, e.g. 3.5.0-26 or 3.5.0-21 rather than 3.5.0-27? Very strange.
It looks like there are no linux-image packages in quantal-backports, so trying a newer kernel will be tricky. I guess I'll repartition and try installing raring in the new partition.