hard-lock with CPU spinning

[Giorgos Keramidas]

On 2007-06-14 20:02, Giorgos Keramidas <keramida at ceid.upatras.gr> wrote:
>On 2007-06-14 18:36, Attilio Rao <attilio at freebsd.org> wrote:
>>2007/6/14, Giorgos Keramidas <keramida at ceid.upatras.gr>:
>>> If I leave my laptop idle for a long period of time, it tends to lock up
>>> with the CPU fan spinning fast (presumambly because some part of the
>>> kernel tries to acquire a lock and spins constantly for it).
>>>
>>> Unfortunately, this happens when X11 is running and I can't break into
>>> DDB to snoop around.

Hi Attilio,

thanks for the eagerness to help, but I was too quick in assuming this
was a hard-lock.  The kernel hasn't deadlocked, but the laptop is almost
unresponsive because the X server eats up an enormous amount of CPU.

I left an xterm window running:

    > cd /home/keramida
    > ( while true ; do \
            uptime ; ps xaur | head -20 ; \
            sleep 5 ; echo ; \
        done ) 2>&1 | tee logfile

and when hte CPU fan started spinning fast, I managed to shutdown
normally by pressing the laptop's power-off button and waiting long
enough for the X process to die.

The ~/logfile file contains near its end entries like:

%  6:43PM  up  2:05, 1 user, load averages: 0.76, 0.39, 0.24
% USER       PID %CPU %MEM   VSZ   RSS  TT  STAT STARTED      TIME COMMAND
% root      1234 97.8  4.2 285648 21428  v1  R     4:41PM   3:22.41 X :0 -dpi 96 (Xorg)
% root        12 97.1  0.0     0     8  ??  RL    4:37PM 112:19.80 [idle: cpu0]
% root        11  2.2  0.0     0     8  ??  RL    4:37PM 110:16.80 [idle: cpu1]
%
%  6:43PM  up  2:06, 1 user, load averages: 0.78, 0.40, 0.25
% USER       PID %CPU %MEM   VSZ   RSS  TT  STAT STARTED      TIME COMMAND
% root      1234 98.1  4.2 285648 21428  v1  R     4:41PM   3:27.51 X :0 -dpi 96 (Xorg)
% root        12 97.3  0.0     0     8  ??  RL    4:37PM 112:24.75 [idle: cpu0]
% root        11  1.7  0.0     0     8  ??  RL    4:37PM 110:16.83 [idle: cpu1]
%
%  6:43PM  up  2:06, 1 user, load averages: 0.80, 0.41, 0.25
% USER       PID %CPU %MEM   VSZ   RSS  TT  STAT STARTED      TIME COMMAND
% root      1234 98.4  4.2 285648 21428  v1  R     4:41PM   3:32.51 X :0 -dpi 96 (Xorg)
% root        12 97.5  0.0     0     8  ??  RL    4:37PM 112:29.71 [idle: cpu0]
% root        11  1.3  0.0     0     8  ??  RL    4:37PM 110:16.84 [idle: cpu1]

Apparently, there's a bug in my xorg 7.2 installation.  Please don't
spend time looking for a locking issue, until I verify that this is not
a local installation problem.