Re: [PATCH v2] blk-mq: Fix race between resetting the timer and completion handling

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On Wed, 2018-02-07 at 09:06 -0800, Tejun Heo wrote:
> Can you see whether by any chance the following patch fixes the issue?
> If not, can you share the repro case?
> 
> Thanks.
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index df93102..651d18c 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -836,8 +836,8 @@ static void blk_mq_rq_timed_out(struct request *req, bool reserved)
>  		 * ->aborted_gstate is set, this may lead to ignored
>  		 * completions and further spurious timeouts.
>  		 */
> -		blk_mq_rq_update_aborted_gstate(req, 0);
>  		blk_add_timer(req);
> +		blk_mq_rq_update_aborted_gstate(req, 0);
>  		break;
>  	case BLK_EH_NOT_HANDLED:
>  		break;

Hello Tejun,

I tried the above patch but already during the first iteration of the test I
noticed that the test hung, probably due to the following request that got stuck:

$ (cd /sys/kernel/debug/block && grep -aH . */*/*/rq_list)
00000000a98cff60 {.op=SCSI_IN, .cmd_flags=, .rq_flags=MQ_INFLIGHT|PREEMPT|QUIET|IO_STAT|PM,
 .state=idle, .tag=22, .internal_tag=-1, .cmd=Synchronize Cache(10) 35 00 00 00 00 00, .retries=0,
 .result = 0x0, .flags=TAGGED, .timeout=60.000, allocated 872.690 s ago}

Thanks,

Bart.






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