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
