Re: [Qemu-devel] qemu 2.0, deadlock in block-commit

[Marcin Gibuła]

> I see that you have a mix of aio=native and aio=threads. I can't say
> much about the aio=native disks (perhaps try to reproduce without
> them?), but there are definitely no worker threads for the other disks
> that bdrv_drain_all() would have to wait for.

True. But I/O was being done only qcow2 disk with threads backend. And 
snapshot was made on this disk.

I'll try to reproduce with all 'threads'.

> bdrv_requests_pending(), called by bdrv_requests_pending_all(), is the
> function that determines for each of the disks in your VM if it still
> has requests in flight that need to be completed. This function must
> have returned true even though there is nothing to wait for.
>
> Can you check which of its conditions led to this behaviour, and for
> which disk it did? Either by setting a breakpoint there and
> singlestepping through the function the next time it is called (if the
> poll even has a timeout), or by inspecting the conditions manually in
> gdb.

I'm on it.

--
mg