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SubjectRe: [patch] CFS scheduler, -v18

* Willy Tarreau <w@1wt.eu> wrote:

> Ingo,
>
> I've accidentally discovered a problem with -v18.
>
> Some time ago, I wrote a small program to prevent my laptop from
> entering low-power mode, and noticed that after upgrading my laptop's
> kernel from 2.4.20.9+cfs-v6 to 2.4.20.14+cfs-v18, it completely
> freezes if I run this program.
>
> The program is trivial, it just sets its prio to nice +20 and forks a
> busy loop. I've added the ability to stop the loop after a
> user-definable number of iterations, and I can confirm that it
> unfreezes when the loop ends. I'm not even root when I run it.

hm, i tried your test-app and it causes no problems here. (which is not
a surprise - your app starts a nice +19 busy loop, which is one of the
common tests i do here too.)

To further debug this, could you try to create a 'high priority shell'
on a text console (i.e. not under X) that is SCHED_FIFO prio 98?
Something like:

chrt -f -p 98 $$

should do the trick. And then run this script:

http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh

before the test, during the test and after the test, from the high-prio
shell session. (the shell runs at SCHED_FIFO, so the expectation would
be for that it will be able to run during the test too) Then please send
me the resulting 3 debug files. Thanks,

Ingo
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