linux-kernel - Re: rcu_sched stall while waiting in csd_lock

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Date:   Wed, 2 Aug 2017 10:14:37 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Pratyush Anand <panand@...hat.com>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        Will Deacon <will.deacon@....com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: rcu_sched stall while waiting in csd_lock_wait()

On Wed, Aug 02, 2017 at 09:01:19AM +0530, Pratyush Anand wrote:
> Hi,
> 
> 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.

I'm sitting on this patch:

  https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?h=locking/core&id=15377ef4fe0c86eb7fa1099575b2e86357d99e42

please give that a spin.