Re: [Qemu-devel] Consistency of iotests 093 and 136

[Alberto Garcia]

On Thu 24 Jan 2019 07:07:47 PM CET, Eric Blake wrote:
>>>> 093 and 136 seem really flaky to me.  I can reproduce that by
>>>> running:
>>>
>>> That's interesting, I can make 093 fail quite easily now (I haven't
>>> tested the other one yet), but I don't think this happened
>>> earlier. I'll try to figure out what's going on.
>> 
>> I bisected this and it seems that 093 started to fail after this:
>> 
>> 8258292e monitor: Remove "x-oob", offer capability "oob" unconditionally
>> 
>> I'm not familiar with that option so I need to investigate.
>
> We've got several tests failing after making x-oob unconditional; here's
> another thread:
>
> https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg05587.html
>
> Could it be that the test was using some sort of QMP command as an
> attempt to synchronize state, but the OOB handling is now making it not
> a reliable sync point?

093 submits several I/O requests using aio_read and aio_write with
hmp_qemu_io(), then advances the clock using clock_step and finally
calls query-blockstats to see how much of the I/O has been completed
(it's an I/O throttling test).

The expectation is that by the time query-blockstats is called all
submitted I/O requests have been processed (up to the amount allowed by
the throttling limits).

Are the QMP (hmp_qemu_io, query-blockstats) and qtest (clock_step)
sockets maybe running in different threads?

Berto