Re: bdrv_drained_begin deadlock with io-threads

[Dietmar Maurer]

> It seems to fix it, yes. Now I don't get any hangs any more. 

I just tested using your configuration, and a recent centos8 image
running dd loop inside it:

# while dd if=/dev/urandom of=testfile.raw bs=1M count=100; do sync; done

With that, I am unable to trigger the bug.

Would you mind running the test using a Debian Buster image running "stress-ng 
-d 5" inside?
I (and to other people here) can trigger the bug quite reliable with that.

On Debian, you can easily install stress-ng using apt:

# apt update
# apt install stress-ng

Seems stress-ng uses a different write pattern which can trigger the bug 
more reliable.