Hang when running LLVM+clang test suite

[Keith Busch]

On Sun, Jan 21, 2018 at 09:13:27AM -0500, David Zarzycki wrote:
> To my surprise, I think I’ve narrowed down the bug to the block multi-queue layer. Can you please confirm that the following test is reasonable?
> 
> 1) Create a file in /tmp (tmpfs with plenty of RAM and 2x the size needed by the test suite)
> 2) ‘losetup’ the file
> 3) 'cat /sys/block/loop0/queue/scheduler' ("[mq-deadline] none” in this case)
> 4) Create ext4 partition on /dev/loop0 and mount it
> 5) Run stress test in the loopback filesystem

The test looks fair to run. Does your error only happen if using
mq-deadline, or are there problems when using "none"?