linux-kernel - Re: NVME regression in all kernels after 4.4.x for NVME in M2 slot for laptop?

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Date:	Fri, 5 Aug 2016 16:50:53 -0400
From:	Keith Busch <keith.busch@...el.com>
To:	Marc MERLIN <marc@...lins.org>
Cc:	axboe@...com, linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: NVME regression in all kernels after 4.4.x for NVME in M2 slot
 for laptop?

On Fri, Aug 05, 2016 at 12:03:23PM -0700, Marc MERLIN wrote:
> Would this patch make sense as being the reason why I can't S3 sleep
> anymore and would you have a test patch against 4.5, 4.6, or 4.7 I can
> try to see if it fixes the problem?

Hi Marc,

It might be blk-mq's hot cpu notifier is invoked during suspend and
waiting for nvme's queues to freeze, which may not happen if a request
is waiting on a stopped queue. The patch you biseceted doesn't
necessarilly fix that, but the window for when a request could get queued
like that was much shorter.

Assuming that is the problem, S3 suspends PCI hardware before IO
tasks. I'll see if I can reproduce on one of my machines and look into
a fix.

Thanks,
Keith