On 02/11/18 23:35, Paolo Valente wrote:

Also this smells a little bit like some spurious elevator call.
Unfortunately I have no clue on the cause.  To go on, I need at least
to reproduce it.  In this respect: Bart, could you please tell me how
to setup the offending configuration, and to cause the failure?
Possibly with just one, or at most two PCs.  I don't have fancier hw
at the moment.

Hello Paolo,

Although I expect that it is possible to reproduce this with an 
unmodified v4.16-rc1 kernel, this is how I ran into this issue:
* Clone the for-next branch of https://github.com/bvanassche/linux.
* Build and install that kernel in a virtual machine.
* Clone https://github.com/bvanassche/srp-test.
* Run the following command:
   srp-test/run_tests -c -d -r 10 -t 02-mq -e bfq

Thanks,

Bart.