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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Jul 19, 2017 at 03:51:48PM +0800, Junxiao Bi wrote:
> 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?

Could you kindly repost it with the updated tags _and_ against Linus's latest
branch?

I get:
[konrad@char linux]$ git am -s < /tmp/a
Applying: xen-blkfront: fix mq start/stop race
error: patch failed: drivers/block/xen-blkfront.c:912
error: drivers/block/xen-blkfront.c: patch does not apply
Patch failed at 0001 xen-blkfront: fix mq start/stop race
The copy of the patch that failed is found in: .git/rebase-apply/patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".


> 
> Thanks,
> Junxiao.
> > 
> > Roger.
> > 
> 

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