[vlc-devel] [PATCH] decoder: read the old p_aout in the lock where we reset it

Thomas Guillem thomas at gllm.fr
Tue Sep 3 14:38:14 CEST 2019


On Tue, Sep 3, 2019, at 14:34, Rémi Denis-Courmont wrote:
> Hi,
> 
> AFAIK, it is, or at least was at some point, safe to read outside the lock because no other thread could write it.

If it safe to read outside the lock from the output thread (vout/aout callbacks). Cf my patch documentation.

> 
> It's silly to maximize lock scope. Lock scope should be minimised.
> 
> Le 3 septembre 2019 11:29:28 GMT+03:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>> It's already done this way for p_vout. Since we're going to lock for writing,
>> we might as well read the value in that lock. src/input/decoder.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>> 
>> diff --git a/src/input/decoder.c b/src/input/decoder.c
>> index 63f858c397..25aa1e0727 100644
>> --- a/src/input/decoder.c
>> +++ b/src/input/decoder.c
>> @@ -220,9 +220,9 @@ static int ReloadDecoder( struct decoder_owner *p_owner, bool b_packetizer,
>>      if( reload == RELOAD_DECODER_AOUT )
>>      {
>>          assert( p_owner->fmt.i_cat == AUDIO_ES );
>> -        audio_output_t *p_aout = p_owner->p_aout;
>>  
>>          vlc_mutex_lock( &p_owner->lock );
>> +        audio_output_t *p_aout = p_owner->p_aout;
>>          p_owner->p_aout = NULL;
>>          vlc_mutex_unlock( &p_owner->lock );
>>          if( p_aout )
>> @@ -301,10 +301,9 @@ static int aout_update_format( decoder_t *p_dec )
>>           p_dec->fmt_out.i_codec != p_dec->fmt_out.audio.i_format ||
>>           p_dec->fmt_out.i_profile != p_owner->fmt.i_profile ) )
>>      {
>> -        audio_output_t *p_aout = p_owner->p_aout;
>> -
>>          /* Parameters changed, restart the aout */
>>          vlc_mutex_lock( &p_owner->lock );
>> +        audio_output_t *p_aout = p_owner->p_aout;
>>          p_owner->p_aout = NULL;
>>          vlc_mutex_unlock( &p_owner->lock );
>>          aout_DecDelete( p_aout );
> 
> -- 
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