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Subject: Re: bug in tag handling in blk-mq?
To:     Mike Galbraith <efault@gmx.de>,
        Paolo Valente <paolo.valente@linaro.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        linux-block <linux-block@vger.kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Oleksandr Natalenko <oleksandr@natalenko.name>
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From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <3692ce7d-a767-72e6-65ae-6178b6c2e7d8@kernel.dk>
Date:   Tue, 8 May 2018 14:37:52 -0600
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On 5/8/18 10:42 AM, Mike Galbraith wrote:
> On Tue, 2018-05-08 at 08:55 -0600, Jens Axboe wrote:
>>
>> All the block debug files are empty...
> 
> Sigh.  Take 2, this time cat debug files, having turned block tracing
> off before doing anything else (so trace bits in dmesg.txt should end
> AT the stall).

OK, that's better. What I see from the traces:

- You have regular IO and some non-fs IO (from scsi_execute()). This mix
  may be key.

- sdd has nothing pending, yet has 6 active waitqueues.

I'm going to see if I can reproduce this. Paolo, what kind of attempts
to reproduce this have you done?

-- 
Jens Axboe