Re: oom-killer causes lockups in cpuset_excl_nodes_overlap()

[Kirill Korotaev <dev@sw.ru>]

yes, we found the same problem while looking at the code.
and this is not the only cpuset function which might sleep, but is 
called from atomic context... :(

> The oom-killer causes lockups because it calls
> cpuset_excl_nodes_overlap() with tasklist_lock read-locked.
> cpuset_excl_nodes_overlap() gets cpuset_sem (or callback_sem in
> later linux versions) semaphore, which might_sleep even if the
> semaphore could be down without sleeping.  If processes call
> exit() or fork() when the oom-killer sleeps in the down(), they
> lockup because they call write_lock_irq(&tasklist_lock).
>
> The lockup occurred on linux-2.6.14.  The problem also seems to exist
> in linux-2.6.15-rc5-mm3 and linux-2.6.15-rc7.
>
> Regards,
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