From: Ming Lei <ming.lei@redhat.com>
To: Alban Browaeys <alban.browaeys@gmail.com>,
Paolo Valente <paolo.valente@linaro.org>
Cc: Jens Axboe <axboe@fb.com>, linux-block@vger.kernel.org
Subject: Re: blk-mq + bfq: udevd hang on usb2 storages
Date: Mon, 4 Dec 2017 18:57:21 +0800 [thread overview]
Message-ID: <20171204105720.GA6884@ming.t460p> (raw)
In-Reply-To: <1512147869.8698.21.camel@gmail.com>
On Fri, Dec 01, 2017 at 06:04:29PM +0100, Alban Browaeys wrote:
> I initially reported as https://bugzilla.kernel.org/show_bug.cgi?id=198
> 023 .
>
> I have now bisected this issue to commit a6a252e6491443c1c1 "blk-mq-
> sched: decide how to handle flush rq via RQF_FLUSH_SEQ".
>
> This is with an USB stick Sandisk Cruzer (USB Version: 2.10) I
> regressed with.
> systemctl restart systemd-udevd restores sanity.
>
> PS: With an USB3 Lexar (USB Version: 3.00) I get more severe an issue
> (not bisected) where I find no way out of reboot. My report to bugzilla
> has logs when I was swapping between the these keys. The logs attached
> there mixes what looks like two different behaviors.
Hi Paolo,
>From both Alban's trace and my trace, looks this issue is in BFQ,
since request can't be retrieved via e->type->ops.mq.dispatch_request()
in blk_mq_do_dispatch_sched() after it is inserted into BFQ's queue.
https://bugzilla.kernel.org/show_bug.cgi?id=198023#c4
https://marc.info/?l=linux-block&m=151214241518562&w=2
BTW, I have tried to reproduce the issue with scsi_debug, but not succeed,
and it can't be reproduced with other schedulers(mq-deadline, none) too.
So could you take a look?
Thanks,
Ming
next prev parent reply other threads:[~2017-12-04 10:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-01 17:04 blk-mq + bfq: udevd hang on usb2 storages Alban Browaeys
2017-12-01 17:29 ` Ming Lei
2017-12-04 10:57 ` Ming Lei [this message]
2017-12-07 18:04 ` Paolo Valente
2017-12-08 1:28 ` Ming Lei
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