On 01/13/2017 09:00 AM, Jens Axboe wrote:

On 01/13/2017 08:59 AM, Hannes Reinecke wrote:

quoted

On 01/13/2017 04:34 PM, Jens Axboe wrote:

quoted

On 01/13/2017 08:33 AM, Hannes Reinecke wrote:

[ .. ]

quoted

quoted

Ah, indeed.
There is an ominous udev rule here, trying to switch to 'deadline'.

# cat 60-ssd-scheduler.rules
# do not edit this file, it will be overwritten on update

ACTION!="add", GOTO="ssd_scheduler_end"
SUBSYSTEM!="block", GOTO="ssd_scheduler_end"

IMPORT{cmdline}="elevator"
ENV{elevator}=="*?", GOTO="ssd_scheduler_end"

KERNEL=="sd*[!0-9]", ATTR{queue/rotational}=="0",
ATTR{queue/scheduler}="deadline"

LABEL="ssd_scheduler_end"

Still shouldn't crash the kernel, though ...

Of course not, and it's not a given that it does, it could just be
triggering after the device load and failing like expected. But just in
case, can you try and disable that rule and see if it still crashes with
MQ_DEADLINE set as the default?

Yes, it does.
Same stacktrace as before.

Alright, that's as expected. I've tried with your rule and making
everything modular, but it still boots fine for me. Very odd. Can you
send me your .config? And are all the SCSI disks hanging off ahci? Or
sdb specifically, is that ahci or something else?

Also, would be great if you could pull:

git://git.kernel.dk/linux-block blk-mq-sched

into current 'master' and see if it still reproduces. I expect that it
will, but just want to ensure that it's a problem in the current code
base as well.

-- 
Jens Axboe