Re: [Qemu-devel] [Qemu-block] [PATCH v5 6/6] iotests: extend sleeping time under Valgrind

[Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>]

On 27/08/2019 22:42, John Snow wrote:
> 
> 
> On 8/23/19 11:27 AM, Vladimir Sementsov-Ogievskiy wrote:
>> 16.08.2019 4:01, John Snow wrote:
>>>
>>>
>>> On 7/19/19 12:30 PM, Andrey Shinkevich wrote:
>>>> To synchronize the time when QEMU is running longer under the Valgrind,
>>>> increase the sleeping time in the test 247.
>>>>
>>>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
>>>> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>>> ---
>>>>    tests/qemu-iotests/247 | 6 +++++-
>>>>    1 file changed, 5 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/tests/qemu-iotests/247 b/tests/qemu-iotests/247
>>>> index 546a794..c853b73 100755
>>>> --- a/tests/qemu-iotests/247
>>>> +++ b/tests/qemu-iotests/247
>>>> @@ -57,7 +57,11 @@ TEST_IMG="$TEST_IMG.4" _make_test_img $size
>>>>    {"execute":"block-commit",
>>>>     "arguments":{"device":"format-4", "top-node": "format-2", "base-node":"format-0", "job-id":"job0"}}
>>>>    EOF
>>>> -sleep 1
>>>> +if [ "${VALGRIND_QEMU}" == "y" ]; then
>>>> +    sleep 10
>>>> +else
>>>> +    sleep 1
>>>> +fi
>>>>    echo '{"execute":"quit"}'
>>>>    ) | $QEMU -qmp stdio -nographic -nodefaults \
>>>>        -blockdev file,node-name=file-0,filename=$TEST_IMG.0,auto-read-only=on \
>>>>
>>>
>>> This makes me nervous, though. Won't this race terribly? (Wait, why
>>> doesn't it race already?)
>>>
>>
>> Hmm, however it works somehow. I'm afraid that everything with "sleep" is definitely racy..
>> Or what do you mean?
>>
> 
> Right -- anything with a sleep is already at risk for racing.
> 
> What I am picking up on here is that with valgrind, there is an even
> greater computational overhead that's much harder to predict, so I was
> wondering how these values were determined.
> 

I just followed the trend and extended the sleeping time with a grater 
tolerance so that the test could pass on systems where the 'sleep 1' 
command helps to pass without Valgrind. We could rewrite the test 247 in 
Python in a separate series, shall we?

Andrey

> (I wouldn't withhold an RB for that alone -- the sleeps are existing
> problems.)
> 
> What I moved on to wondering in particular is why test 247 doesn't
> already have race problems, because it looks quite fragile.
> 
> Neither of these are really Andrey's problems; I was just surprised
> momentarily that I don't see 247 fail more often already, as-is.
> 
> --js
> 

-- 
With the best regards,
Andrey Shinkevich