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Subject: Re: [PATCH BUGFIX V3] block, bfq: add requeue-request hook
From: Mike Galbraith <efault@gmx.de>
To: Paolo Valente <paolo.valente@linaro.org>
Cc: Oleksandr Natalenko <oleksandr@natalenko.name>,
        Jens Axboe <axboe@kernel.dk>, stable <stable@vger.kernel.org>
Date: Wed, 14 Feb 2018 08:15:12 +0100
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On Wed, 2018-02-14 at 08:04 +0100, Mike Galbraith wrote:
> 
> And _of course_, roughly two minutes later, IO stalled.

P.S.

crash> bt 19117
PID: 19117  TASK: ffff8803d2dcd280  CPU: 7   COMMAND: "kworker/7:2"
 #0 [ffff8803f7207bb8] __schedule at ffffffff81595e18
 #1 [ffff8803f7207c40] schedule at ffffffff81596422
 #2 [ffff8803f7207c50] io_schedule at ffffffff8108a832
 #3 [ffff8803f7207c60] blk_mq_get_tag at ffffffff8129cd1e
 #4 [ffff8803f7207cc0] blk_mq_get_request at ffffffff812987cc
 #5 [ffff8803f7207d00] blk_mq_alloc_request at ffffffff81298a9a
 #6 [ffff8803f7207d38] blk_get_request_flags at ffffffff8128e674
 #7 [ffff8803f7207d60] scsi_execute at ffffffffa0025b58 [scsi_mod]
 #8 [ffff8803f7207d98] scsi_test_unit_ready at ffffffffa002611c [scsi_mod]
 #9 [ffff8803f7207df8] sd_check_events at ffffffffa0212747 [sd_mod]
#10 [ffff8803f7207e20] disk_check_events at ffffffff812a0f85
#11 [ffff8803f7207e78] process_one_work at ffffffff81079867
#12 [ffff8803f7207eb8] worker_thread at ffffffff8107a127
#13 [ffff8803f7207f10] kthread at ffffffff8107ef48
#14 [ffff8803f7207f50] ret_from_fork at ffffffff816001a5
crash>