Re: [PATCH v3 0/3] qrwlock: Introducing a queue read/write lock implementation

[Waiman Long]

On 08/14/2013 06:20 AM, Ingo Molnar wrote:
> * Waiman Long<waiman.long@xxxxxx>  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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