Fast scrolling causes X hang

Can you indicate what release of Ubuntu this issue happens and if it still persists on the current Dapper release?

Yes - it still happens in Dapper, and it started after upgrade to Dapper. I'm running fully updated system.
However it is becoming less frequent. I can hardly reproduce it now, but I hit it once a week or so. I've got a feeling that it almost stopped showing after one of Aixgl updates, but Aixgl alone wasn't the cause of it, as it happened many times on standard X, before I started playing with Xgl.
It's always triggered by fast scrolling though. Typically if I try to scroll a window that is still loading / is changing content - it's almost always loading page in FF.

Stanislaw,

thank you for the bug report!

you mention aiglx on your last comment. By any chance, have you installed aiglx or Xgl from external repositories? External aiglx/Xgl repositories are known to be unstable on Dapper, and are not supported.

Yes - i've got it from xgl.compiz.info, but as I said before - it happens on clean xorg too - not that frequently, but still.

There was an update to font rendering in gnome today, it may solve the problem. Besides, an advice would be to turn off font hinting in gdm. It triggers some payload on cpu and if you are fast scrolling on a f.ex. Pentium III class system, it may go "out of sync" with refreshing screen and crash X. Smoothing may be ok, hinting doesn't much improve overall look, but is taking up system resources.

I can confirm that the bug existed and is gone with the latest security update libxfont 1:1.0.0-0ubuntu3.1 from 6 Sept. That overflow also might have happened, when cpu was "too busy" when scrolling. Crashes were often, especially when scrolling GNOME Terminal window. Test system was P III 733, NVidia GF 5200 with restricted driver 87.74. Does anyone still experience such crashes?

Could this be related to my bug #61250?
https://launchpad.net/distros/ubuntu/+source/xorg/+bug/61250

grepping through my dpkg.log shows I upgraded libxfont to libxfont1 1:1.0.0-0ubuntu3.2 and xorg started consuming 99.9% CPU and hanging pretty soon after.
will try backing out the upgrade to the previous working version and see if that fixes it....

I don't think so. The problem you described is rather related to video memory timing. It look like as if an extra wait state were needed when the system is accessing video memory directly, where in fact it's accessing part of system RAM assigned to video. Perhaps it could be fixed in BIOS (something like AGP write 0 WS, AGP fast writes, etc. - disable it). You may also try NVIDIA binary driver and see if it behaves in a different way.

Thank you for taking the time to report this bug and helping to make Ubuntu better. You reported this bug a while ago and there hasn't been any activity in it recently. We were wondering is this still an issue for you? Thanks in advance.

We are closing this bug report because it lacks the information we need to investigate the problem, as described in the previous comments. Please reopen it if you can give us the missing information, and don't hesitate to submit bug reports in the future. To reopen the bug report you can click on the current status, under the Status column, and change the Status back to "New". Thanks again!