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SubjectRe: [PATCH V2] smp: Give WARN()ing when calling smp_call_function_many()/single() in serving irq
On Fri, Jul 05, 2013 at 04:37:14PM +0200, Thomas Gleixner wrote:
> Hmm, even there it matters, because of the following scenario:
>
> CPU 0
> smp_call_function_single(CPU 1)
> csd_lock(CPU 1)

No, smpl_call_function_single(CPU 1)
will csd_lock(CPU 0), not csd_lock(CPU 1)

> irq_enter()
> irq_exit()
> __do_softirq()
> smp_call_function_many()
> setup csd (CPU 1)
> csd_lock(CPU 1) ==> CPU 0 deadlocked itself.
>

maybe below is the scenario:
irq_enter()
irq_exit()
__do_softirq()
smp_call_function_single()
setup csd (CPU 1)
csd_lock(CPU 0) ==> CPU 0 deadlocked itself.


> And this is even more likely to happen than the lock issue.
>
> Thanks,
>
> tglx
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