Hi Jens,

my colleague Eduardo is sporadically seeing an Oops in blk-mq while
running continuous virtio_blk hot-plug/hot-unplug tests with I/O to the
device within an x86_64 QEMU/KVM 2.0 Debian Wheezy VM.

Please find the call trace attached and the full log here:
http://paste.ubuntu.com/9691873/

The kernel image has been taken from here and is the mainline kernel
from tag v3.18:
http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.18-vivid/

Is there still an issue with block queue freezing?

We are seeing a similar issue with v3.16 but more often as some block
queue freezing fixes have been added in v3.17.

All kernels without blk-mq used by virtio_blk (< v3.13) work fine.

Cheers,
Sebastian