linux-kernel - Re: PATCH V4 0/5 nvme-pci: fixes on nvme_timeout and nvme_dev

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Date:   Thu, 19 Apr 2018 09:51:16 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     keith.busch@...el.com, sagi@...mberg.me,
        linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        axboe@...com, hch@....de
Subject: Re: PATCH V4 0/5 nvme-pci: fixes on nvme_timeout and nvme_dev_disable

Hi Ming

Thanks for your kindly response.

On 04/18/2018 11:40 PM, Ming Lei wrote:
>> Regarding to this patchset, it is mainly to fix the dependency between
>> nvme_timeout and nvme_dev_disable, as your can see:
>> nvme_timeout will invoke nvme_dev_disable, and nvme_dev_disable have to
>> depend on nvme_timeout when controller no response.
> Do you mean nvme_disable_io_queues()? If yes, this one has been handled
> by wait_for_completion_io_timeout() already, and looks the block timeout
> can be disabled simply. Or are there others?
> 
Here is one possible scenario currently

nvme_dev_disable // hold shutdown_lock             nvme_timeout
  -> nvme_set_host_mem                               -> nvme_dev_disable
    -> nvme_submit_sync_cmd                            -> try to require shutdown_lock 
      -> __nvme_submit_sync_cmd
        -> blk_execute_rq
          //if sysctl_hung_task_timeout_secs == 0
          -> wait_for_completion_io
And maybe nvme_dev_disable need to issue other commands in the future.

Even if we could fix these kind of issues as nvme_disable_io_queues, 
it is still a risk I think.

Thanks
Jianchao