Re: hard-lock with CPU spinning

On 2007-06-17 19:32, Giorgos Keramidas <keramida_at_freebsd.org> wrote:
>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]

Finally, more progress :)

This seems to kick in only when I use:

    % xset +dpms
    % xset s on
    % xset b 100 800 20

By disabling DPMS with '-dpms' there is no CPU-eating behavior
even after leaving my laptop on for hours.

So this seems to be a bug in the +dpms part of X11 :-)