[vlc-devel] [PATCH] decoder_helpers: fix clean order

[Rémi Denis-Courmont]

Hi,

As a general rule, a module is responsible for completing any pending work before it returns from its deactivate function'

The actual unmapping of plugins happens only when LibVLC terminates.

Le 20 février 2019 11:08:54 GMT+02:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>On 19/02/2019 13:24, Thomas Guillem wrote:
>> The module need to be unloaded before the dec struct is cleaned.
>>
>> This fixes an undefined behavior with threaded decoders like avcodec
>when they
>> called decoder_UpdateVideoFormat()/dec_NewPicture() from an other
>thread just
>> before they were unloaded.
>
>Are there cases where the decoder is still calling 
>decoder_UpdateVideoFormat() and decoder_NewPicture() while being about 
>to be unloaded ? I don't see how this can work if one thread of the 
>decoder is calling decoder_UpdateVideoFormat() while another thread is 
>unloading the decoder DLLs. If that can happen I think the undefined 
>behavior is the least of our problem.
>
>AFAIK lavc always call decoder_UpdateVideoFormat()/decoder_NewPicture()
>
>from the same (decoder?) thread.
>
>This is an important thing because the decoder pool will be released 
>there as well as the video context reference count.
>
>> ---
>>   src/input/decoder_helpers.c | 11 ++++++-----
>>   1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/src/input/decoder_helpers.c
>b/src/input/decoder_helpers.c
>> index 3cc02de8d6..b0a7c1890a 100644
>> --- a/src/input/decoder_helpers.c
>> +++ b/src/input/decoder_helpers.c
>> @@ -48,6 +48,12 @@ void decoder_Init( decoder_t *p_dec, const
>es_format_t *restrict p_fmt )
>>   
>>   void decoder_Clean( decoder_t *p_dec )
>>   {
>> +    if ( p_dec->p_module != NULL )
>> +    {
>> +        module_unneed(p_dec, p_dec->p_module);
>> +        p_dec->p_module = NULL;
>> +    }
>> +
>>       es_format_Clean( &p_dec->fmt_in );
>>       es_format_Clean( &p_dec->fmt_out );
>>   
>> @@ -56,11 +62,6 @@ void decoder_Clean( decoder_t *p_dec )
>>           vlc_meta_Delete(p_dec->p_description);
>>           p_dec->p_description = NULL;
>>       }
>> -    if ( p_dec->p_module != NULL )
>> -    {
>> -        module_unneed(p_dec, p_dec->p_module);
>> -        p_dec->p_module = NULL;
>> -    }
>>   }
>>   
>>   void decoder_Destroy( decoder_t *p_dec )
>> -- 
>> 2.20.1
>>
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