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SubjectRE: kdump: crash_kexec()-smp_send_stop() race in panic
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Hello Seiji,

On Mon, 2011-10-24 at 18:24 -0400, Seiji Aguchi wrote:
> Hi,
>
> >> >>> 1st CPU:
> >> >>> panic()->crash_kexec()->mutex_trylock(&kexec_mutex)-> do kdump
> >> >>>
> >> >>> 2nd CPU:
> >> >>> panic()->crash_kexec()->kexec_mutex already held by 1st CPU
> >> >>> ->smp_send_stop()-> stop CPU 1 (stop kdump)
> >> >>>
> >> >>> How should we fix this problem? One possibility could be to do
> >> >>> smp_send_stop() before we call crash_kexec().
>
> http://lkml.org/lkml/2010/9/16/353
>
> I developed a patch solving this issue one year ago.
> (Just adding local_irq_disable in kexec path.)

This won't work (at least on s390) because smp_send_stop() will also
stop CPUs that have interrupts disabled.

Michael



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