regression: 2.6.27-4 does not always update screen after suspend

[Henrik Rydberg]

The problem seems to only occur after resume from suspend to ram. The key strokes are never lost, only strangely not displayed on the screen. Typing in an xterm for intance, it happens every now and then that nothing is seen, until either return or backspace is pressed (works 50%), or a change to and back from another window is made with Alt-Tab (works 100%). It seems the problem is related to drm and/or the i915 modules, because:

1. kill `pgrep gdm`; gdm: problem persists
2. kill `pgrep gdm`; rmmod i915; gdm: problem goes away for a while, but eventually comes back
3. kill `pgrep gdm`; rmmod i915 drm; gdm: problem goes away

I can see nothing in dmesg that indicates an error. I am running Intrepid with kernel 2.6.27-4-generic, on a Macbook Air 1,1. The problem is not present in Hardy with kernel 2.6.24-19.

[Henrik Rydberg (rydberg)]

The problem went away after upgrading to 2.6.27-5-generic.

[Henrik Rydberg (rydberg)]

With 90% certainty, the problem *was* gone, but came back with the updates betwen 06OCT2008 and 07OCT2008. The set includes an update to 2.6.27-5-generic.

[Henrik Rydberg (rydberg)]

Problem persists with the latest 2.6.27-6-generic kernel and companion updates.

[Henrik Rydberg (rydberg)]

The problem has gotten worse. This is the first time I have noticed the problem immediately after cold-booting. Killing gdm and the drm module does not help, so my initial assumption as to the culprit seems wrong. The problem is getting severe, however.

[Henrik Rydberg (rydberg)]

It seems this is a problem xterm, or xterm and gnome-terminal repond differently to a common problem. Test case:

1. Do a suspend and resume

2. Open an xterm and a gnome-terminal window

3. In the xterm window, hold down a key (I used p), and observe the key stream being output. Every now and then there is a halt in the output, which can last for many seconds.

4. In the gnome-terminal window, do the same thing. The keys are output normally.

[Henrik Rydberg (rydberg)]

The same discrepancy is seen between gnu emacs and gedit.

[Henrik Rydberg (rydberg)]

The 17OCT2008 updates seems to have fixed the problem! Test case now passing. As to the reason... who knows.