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SubjectRe: ed74ae0342 ("blk-mq: Avoid that a completion can be ignored .."): BUG: kernel hang in test stage
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On 4/24/18 3:00 PM, kernel test robot wrote:
> Greetings,
>
> 0day kernel testing robot got the below dmesg and the first bad commit is
>
> https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-linus
>
> commit ed74ae03424684a6ad8a973c3fa727c6b4162432
> Author: Bart Van Assche <bart.vanassche@wdc.com>
> AuthorDate: Thu Apr 19 09:43:53 2018 -0700
> Commit: Jens Axboe <axboe@kernel.dk>
> CommitDate: Thu Apr 19 14:21:47 2018 -0600
>
> blk-mq: Avoid that a completion can be ignored for BLK_EH_RESET_TIMER
>
> The blk-mq timeout handling code ignores completions that occur after
> blk_mq_check_expired() has been called and before blk_mq_rq_timed_out()
> has reset rq->aborted_gstate. If a block driver timeout handler always
> returns BLK_EH_RESET_TIMER then the result will be that the request
> never terminates.
>
> Fix this race as follows:
> - Use the deadline instead of the request generation to detect whether
> or not a request timer fired after reinitialization of a request.
> - Store the request state in the lowest two bits of the deadline instead
> of the lowest two bits of 'gstate'.
> - Rename MQ_RQ_STATE_MASK into RQ_STATE_MASK and change it from an
> enumeration member into a #define such that its type can be changed
> into unsigned long. That allows to write & ~RQ_STATE_MASK instead of
> ~(unsigned long)RQ_STATE_MASK.
> - Remove all request member variables that became superfluous due to
> this change: gstate, gstate_seq and aborted_gstate_sync.
> - Remove the request state information that became superfluous due to this
> patch, namely RQF_MQ_TIMEOUT_EXPIRED.
> - Remove the code that became superfluous due to this change, namely
> the RCU lock and unlock statements in blk_mq_complete_request() and
> also the synchronize_rcu() call in the timeout handler.

Any chance you can try with the newer version?

https://github.com/bvanassche/linux/commit/4acd555fa13087

--
Jens Axboe

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