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

[Ingo Molnar]

* Waiman Long <waiman.long@xxxxxx> wrote:

> 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.

Could be a CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE=1 kernel?

Thanks,

	Ingo
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