linux-kernel - Re: [PATCH] NVMe: Avoid interrupt disable during queue init.

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Message-ID: <alpine.LNX.2.00.1505221446410.15930@localhost.lm.intel.com>
Date:	Fri, 22 May 2015 14:48:13 +0000 (UTC)
From:	Keith Busch <keith.busch@...el.com>
To:	Parav Pandit <parav.pandit@...gotech.com>
cc:	Keith Busch <keith.busch@...el.com>,
	linux-nvme@...ts.infradead.org,
	Matthew Wilcox <willy@...ux.intel.com>,
	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] NVMe: Avoid interrupt disable during queue init.

On Thu, 21 May 2015, Parav Pandit wrote:
> On Fri, May 22, 2015 at 1:04 AM, Keith Busch <keith.busch@...el.com> wrote:
>> The q_lock is held to protect polling from reading inconsistent data.
>
> ah, yes. I can see the nvme_kthread can poll the CQ while its getting
> created through the nvme_resume().
> I think this opens up other issue.
>
> nvme_kthread() should,
>
> Instead of,
> struct nvme_queue *nvmeq = dev->queues[i];
>
> it should do,
> struct nvme_queue *nvmeq = rcu_dereference(dev->queues[i]);

The rcu protection on nvme queues was removed with the blk-mq conversion
as we rely on that layer for h/w access.
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