WARNING triggers at blk_mq_update_nr_hw_queues during nvme_reset_work

[axboe@kernel.dk (Jens Axboe)]

On 05/30/2017 11:55 AM, Keith Busch wrote:
> On Tue, May 30, 2017@02:00:44PM -0300, Gabriel Krisman Bertazi wrote:
>> Since the merge window for 4.12, one of the machines in Intel's CI
>> started to hit the WARN_ON below at blk_mq_update_nr_hw_queues during an
>> nvme_reset_work.  The issue persists with the latest 4.12-rc3, and full
>> dmesg from boot, up to the moment where the WARN_ON triggers is
>> available at the following link:
>>
>> https://intel-gfx-ci.01.org/CI/CI_DRM_2672/fi-kbl-7500u/igt at kms_pipe_crc_basic@suspend-read-crc-pipe-a.html
>>
>> Please notice that the test we do in the CI involves putting the
>> machine to sleep (PM), and the issue triggers when resuming execution.
>>
>> I have not been able to get my hands on the machine yet to do an actual
>> bisect, but I'm wondering if you guys might have an idea of what is
>> wrong.
>>
>> Any help is appreciated :)
> 
> Hi Gabriel,
> 
> This appears to be new behavior in blk-mq's tag set update with commit
> 705cda97e. This is asserting a lock is held, but none of the drivers
> that call the export are take that lock.

Ugh yes, that was a little sloppy... Would you mind sending this as
a proper patch? Then I'll queue it up for 4.12.

-- 
Jens Axboe