Most recent kernel where this bug did not occur: unsure, mabe 2.6.12 Distribution: Gentoo Hardware Environment: x86, tvcard: pv951 (V4L number 42, tuner 8) Software Environment: gcc-3.3.6-hardened-nopiessp, GNU, Xorg, KDE Problem Description: Sometimes KDEtv running as a unprivileged user crashes in sutch a way that ps ax will hang. Steps to reproduce: Whatch TV using KDEtv, to be root is not needed. Switch between fullscreen and a window, between X and the terminals (using ctrl-alt-f[something]), and between channels, all randomly combined. This will make the crash more likely.
w will also crash, when the bug is active.
Would it be possible for you to capture the crash/oops output via screenshot or serial console?
All that happens is that the program (ps or w) freezes in the middle of printing. There is no message. It just stops in the middle, and becomes unkillable using eiather ctrl+c or kill -9 processid. (Other consolls and the rest of the system works fine)
Doesn't the dmesg has some oops? ps and w maybe be crashing while trying to scan the /proc directory of a task that has oopsed somewhere, so the real bug should be the oopsing task
Please view http://lkml.org/lkml/2007/9/9/138 http://bugs.kde.org/show_bug.cgi?id=148119 http://forums.gentoo.org/viewtopic.php?t=629024 for a lot more information on this issue. Serveral call traces available. According to the message from the LKML it seems to be a possible kernel deadlock in the videobuf code, triggered by accessing it through different threads from the same application. At this time, only KDETV is known to do so. The problem PERSISTS on recent kernel versions, as far as I can tell up to 2.6.23 Who is going to care about this? Some comments would be rather appreciated.
It looks like the bug is still present. Copying to Mauro, it seems to implicate bttv driver every time.
There were several changes on videobuf code and its lock handing. Those changes are at the latest 2.6.25-rc. There are also some other programmed fixes. Could you please test the latest v4l-dvb development tree, available at: http://linuxtv.org/hg/v4l-dvb