From mboxrd@z Thu Jan  1 00:00:00 1970
From: minwoo.im.dev@gmail.com (Minwoo Im)
Date: Tue, 7 May 2019 00:52:34 +0900
Subject: [PATCH] nvme-loop: Fix race between completions and shutdown
In-Reply-To: <20190506151727.GB2164@localhost.localdomain>
References: <20190506145203.2851-1-minwoo.im.dev@gmail.com>
 <20190506145327.GA2164@localhost.localdomain>
 <0db7e312-0ff2-45f2-8ee1-7ad7b6fd3e5a@gmail.com>
 <20190506151727.GB2164@localhost.localdomain>
Message-ID: <1ced3919-af4a-7899-8d49-026b9cc82e2b@gmail.com>

On 5/7/19 12:17 AM, Keith Busch wrote:
> On Tue, May 07, 2019@12:07:47AM +0900, Minwoo Im wrote:
>>
>> If don't mind, can I ask how can blk_mq_tagset_busy_iter() make sure that no
>> more requests are coming into this request_queue during this iteration ?
> 
> If a queue is frozen, there can't be any allocated tags, so calling
> blk_mq_tagset_busy_iter for such a queue is a no-op.
> 
> I'm not sure you actually want to freeze in this path though. That may
> block forever if a request needs to be requeued.
> 

Keith,

I think it's possible to happen in nvme-pci also.  When a CPU is 
handling a request completed with nvme_complete_rq(), the controller 
reset by sysfs can occur.  In this case, blk_mq_tagset_busy_iter() will 
iterate over the requests allocated in nvme_dev_disable().

Does nvme-pci host driver handle this kind of situation ?

Thanks,