Re: [patch 61/66] timers: Convert to hotplug state machine

From	Jon Hunter <jonathanh@nvidia.com>
Newsgroups	linux.kernel
Subject	Re: [patch 61/66] timers: Convert to hotplug state machine
Date	2016-07-26 20:20 +0200
Message-ID	<rZf7r-5rm-7@gated-at.bofh.it> (permalink)
References	<rTIFb-70u-3@gated-at.bofh.it> <rTIFd-70u-69@gated-at.bofh.it> <rYPwn-5P2-41@gated-at.bofh.it> <rZcMi-3It-17@gated-at.bofh.it>
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Hi Richard,

On 26/07/16 16:42, rcochran@linutronix.de wrote:
> Jon,
> 
> On Mon, Jul 25, 2016 at 03:56:48PM +0100, Jon Hunter wrote:
>>> When tearing down, call timers_dead_cpu before notify_dead.
>>> There is a hidden dependency between:
>>>
>>> - timers
>>> - Block multiqueue
>>> - rcutree
>>>
>>> If timers_dead_cpu() comes later than blk_mq_queue_reinit_notify()
>>> that latter function causes a RCU stall.
>>
>> After this change is applied I am seeing RCU stalls during suspend
>> on Tegra. I guess I am hitting the case mentioned above? How should
>> this be avoided?
> 
> Contrary to the commit message, this callback ended up in the wrong
> place within the sequence.  (It was correct in an earlier version, but
> the series has been through many changes.)
> 
> Can you try this patch to see if it avoids the stall, please?

I have included the patch and I am no longer seeing any RCU stalls and
so this does look like it fixed it.

Thanks!
Jon

-- 
nvpublic

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Re: [patch 61/66] timers: Convert to hotplug state machine rcochran@linutronix.de - 2016-07-26 17:50 +0200
  Re: [patch 61/66] timers: Convert to hotplug state machine Jon Hunter <jonathanh@nvidia.com> - 2016-07-26 20:20 +0200

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