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SubjectRe: [PATCH v3 0/3] qrwlock: Introducing a queue read/write lock implementation
On 08/14/2013 06:20 AM, Ingo Molnar wrote:
> * Waiman Long<waiman.long@hp.com> wrote:
>
>>
>> I would like to share with you a rwlock related system crash that I
>> encountered during my testing with hackbench on an 80-core DL980. The
>> kernel crash because of a "watchdog detected hard lockup on cpu 79". The
>> crashing CPU was running "write_lock_irq(&tasklist_lock)" in
>> forget_original_parent() of the exit code path when I interrupted the
>> hackbench which was spawning thousands of processes. Apparently, the
>> remote CPU was not able to get the lock for a sufficient long time due
>> to the unfairness of the rwlock which I think my version of queue rwlock
>> will be able to alleviate this issue.
>>
>> So far, I was not able to reproduce the crash. I will try to see if I
>> could more consistently reproduce it.
> Was it an actual crash/lockup, or a longish hang followed by a lock
> detector splat followed by the system eventually recovering back to
> working order?
>
> Thanks,
>
> Ingo

It was an actual crash initiated by the NMI handler. I think the system
was in a halt state after that.

Regards,
Longman


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