quartz: Fix deadlock with transform filter

[Maarten Lankhorst]

Hi Alexandre,

2008/7/7 Alexandre Julliard <julliard at winehq.org>:
> "Maarten Lankhorst" <m.b.lankhorst at gmail.com> writes:
>
>> diff --git a/dlls/quartz/acmwrapper.c b/dlls/quartz/acmwrapper.c
>> index d877930..22bfb87 100644
>> --- a/dlls/quartz/acmwrapper.c
>> +++ b/dlls/quartz/acmwrapper.c
>> @@ -186,7 +186,9 @@ static HRESULT ACMWrapper_ProcessSampleData(TransformFilterImpl* pTransformFilte
>>          }
>>          TRACE("Sample stop time: %u.%03u\n", (DWORD)(tStart/10000000), (DWORD)((tStart/10000)%1000));
>>
>> +        LeaveCriticalSection(&This->tf.csFilter);
>>          hr = OutputPin_SendSample((OutputPin*)This->tf.ppPins[1], pOutSample);
>> +        EnterCriticalSection(&This->tf.csFilter);
>
> This looks very wrong this the lock wasn't grabbed by this function, it
> will violate expectations of the caller. It looks like the locking
> strategy needs some more thought.
 If you look at
It won't violate the locking rules, since this is the way it is
designed. If you look at OutputPin_SendSample, you will see it takes
the critical section to obtain whether the pin is connected to
something, and if it is, it will send the data further. It does a
great job of doing it safely, by obtaining all data under lock and
adding a reference so that it can't die while receiving. The data is
received by the receiving pin which takes a lock while processing the
data, so the code is thread-safe.

Cheers,
Maarten.