[PATCH v2] winegstreamer: Do not block forever if EOS races with command queue.

[Zebediah Figura (she/her)]

On 2/22/22 15:09, Nikolay Sivov wrote:
> 
> 
> On 2/9/22 11:40, Giovanni Mascellani wrote:
>> Currently, the winegstreamer media source checks for EOS when
>> RequestSample() is called, but doesn't handle the cases when EOS
>> is detected between the RequestSample() call and the moment when
>> the request is popped from the command queue and serviced. This
>> can result in the media source waiting forever for a sample and
>> get stuck.
>>
>> This commit fixes the bug by adding a check for EOS in
>> wait_for_event().
>>
>> This commit fixes Medieval Dynasty hanging on developer logos on
>> the Steam Deck.
>>
>> Signed-off-by: Giovanni Mascellani <gmascellani at codeweavers.com>
>> ---
>>   dlls/winegstreamer/media_source.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/dlls/winegstreamer/media_source.c
>> b/dlls/winegstreamer/media_source.c
>> index 85ec31d2498..ca8f92b07ea 100644
>> --- a/dlls/winegstreamer/media_source.c
>> +++ b/dlls/winegstreamer/media_source.c
>> @@ -534,6 +534,12 @@ static void wait_on_sample(struct media_stream
>> *stream, IUnknown *token)
>>         TRACE("%p, %p\n", stream, token);
>>   +    if (stream->eos)
>> +    {
>> +        IMFMediaEventQueue_QueueEventParamVar(stream->event_queue,
>> MEError, &GUID_NULL, MF_E_END_OF_STREAM, &empty_var);
>> +        return;
>> +    }
>> +
>>       for (;;)
>>       {
>>           if (!wg_parser_stream_get_event(stream->wg_stream, &event))
> Sorry, I missed this one. What I don't understand about this is why
> wg_parser_stream_get_event() can't simply return for streams that
> reached eos. It seems it should be able to track such state differences.
> There is already eos flag in wg_parser_stream(), but I see it means
> something else, and is never reset (I think).

The current design of winegstreamer has wg_parser_stream_get_event()
only returning an EOS event once. The DirectShow frontend actually
depends on this design. I'm currently working on reorganizing things so
that it doesn't, though, at which point we could allow that function to
never block on EOS, and probably make things easier.
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