Re: rcu_sched stall while waiting in csd_lock_wait()

From: Marc Zyngier
Date: Wed Aug 02 2017 - 04:44:23 EST

On 02/08/17 09:08, Will Deacon wrote:
> Hi Pratyush,
> On Wed, Aug 02, 2017 at 09:01:19AM +0530, Pratyush Anand wrote:
>> I am observing following rcu_sched stall while executing `perf record -a --
>> sleep 1` with one of the arm64 platform. It looks like that stalled cpu was
>> waiting in csd_lock_wait() from where it never came out,and so the stall.
>> Any help/pointer for further debugging would be very helpful. Problem also
>> reproduced with 4.13.0-rc3.
> When you say "also", which other kernel(s) show the problem? Is this a
> recent regression? Which platform are you running on?
> It would be interesting to know what the other CPUs are doing, in particular
> the target of the cross-call. Either it crashed spectacularly and didn't
> unlock the csd lock, or the IPI somehow wasn't delivered.
> Do you see any other splats if you enable lock debugging?

Also, is that in a guest, or bare metal? If that's a guest, what's the
host's kernel version?


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