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Re: [Xen-devel] [PATCH] xen-blkfront: fix mq start/stop race

Hi Konrad,

On 07/19/2017 03:37 PM, Roger Pau Monné wrote:
> On Wed, Jul 19, 2017 at 09:19:49AM +0800, Junxiao Bi wrote:
>> Hi Roger,
>> On 06/23/2017 08:57 PM, Roger Pau Monné wrote:
>>> On Thu, Jun 22, 2017 at 09:36:52AM +0800, Junxiao Bi wrote:
>>>> When ring buf full, hw queue will be stopped. While blkif interrupt consume
>>>> request and make free space in ring buf, hw queue will be started again.
>>>> But since start queue is protected by spin lock while stop not, that will
>>>> cause a race.
>>>> interrupt:                                      process:
>>>> blkif_interrupt()                               blkif_queue_rq()
>>>>  kick_pending_request_queues_locked()
>>>>   blk_mq_start_stopped_hw_queues()
>>>>    clear_bit(BLK_MQ_S_STOPPED, &hctx->state)
>>>>                                                  blk_mq_stop_hw_queue(hctx)
>>>>    blk_mq_run_hw_queue(hctx, async)
>>>> If ring buf is made empty in this case, interrupt will never come, then the
>>>> hw queue will be stopped forever, all processes waiting for the pending io
>>>> in the queue will hung.
>>>> Signed-off-by: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
>>>> Reviewed-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
>>> Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> Looks patch not in mainline. Can you please help merge it?
> I'm afraid this needs to be done by Konrad or one of the Linux
> maintainers, I don't have an account on kernel.org in order to send
> pull requests to Jens.
Can you pls help merge it?

> Roger.

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