Re: QEMU's tests/unit/test-iov times out on NetBSD and OpenBSD

[Thomas Huth <thuth@redhat.com>]

On 19/01/2024 17.07, Daniel P. Berrangé wrote:
> On Fri, Jan 19, 2024 at 03:55:49PM +0000, Thomas Huth wrote:
>>
>>   Hi,
>>
>> since we recently introduced test timouts in QEMU's meson set up, I noticed
>> that the tests/unit/test-iov times out when doing "make vm-build-netbsd
>> BUILD_TARGET=check-unit" (or vm-build-openbsd).
>>
>> And indeed, when increasing the timeout, you can see that the test-iov runs
>> for multiple minutes on these BSDs while it finishes within few seconds on
>> Linux.
>>
>> I had a closer look at the test, and the problem seems to be the
>>
>>   usleep(g_test_rand_int_range(0, 30));
>>
>> in the test_io() function. If I get that right, the usleep() seems to be
>> more or less precise on (modern) Linux, but it seems like it sleeps for
>> multiple milliseconds (not microseconds) on the BSDs. Since it is used in a
>> nested loop, these milliseconds add up to a long time in total during the
>> test.
>>
>> Does anybody have an idea how to fix that? Is there a more precise (but stil
>> portable) way to sleep less long here? Or could we maybe remove the usleep()
>> here completely (it does not seem to have a real benefit for testing as far
>> as I can see)?
> 
> 'g_usleep' has the same API contract, but is implemented in terms
> of 'nanosleep' on *NIX. So as a quick test, try switching usleep
> to g_usleep and see if we get lucky.

No, that seems to behave the same way, unfortunately.

Do you see a reason why we'd really need the usleep() here at all? 
Otherwise, I think I'll send a patch to simply remove it...

  Thomas