[vlc-devel] [vlc-commits] Revert "lib: media: Use an atomic refcounter"

[Steve Lhomme]

On 2020-11-18 9:53, Hugo Beauzée-Luyssen wrote:
> On Mon, Oct 28, 2019, at 11:34 AM, Hugo Beauzée-Luyssen wrote:
>> vlc | branch: master | Hugo Beauzée-Luyssen <hugo at beauzee.fr> | Thu Oct
>> 24 10:28:35 2019 +0200| [cf14bc8f63bc19092f19354d93f99c289d00afb4] |
>> committer: Hugo Beauzée-Luyssen
>>
>> Revert "lib: media: Use an atomic refcounter"
>>
>> This reverts commit 1b07eaa8612eb77a28178a8739a1a23d4dc16cef.
>>
>>> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=cf14bc8f63bc19092f19354d93f99c289d00afb4
>> ---
>>
>>   lib/media.c          | 8 +++++---
>>   lib/media_internal.h | 3 +--
>>   2 files changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/lib/media.c b/lib/media.c
>> index 36dee3b9e5..d4e3ba7a62 100644
>> --- a/lib/media.c
>> +++ b/lib/media.c
>> @@ -394,7 +394,7 @@ libvlc_media_t * libvlc_media_new_from_input_item(
>>   
>>       p_md->p_libvlc_instance = p_instance;
>>       p_md->p_input_item      = p_input_item;
>> -    vlc_atomic_rc_init(&p_md->refcount);
>> +    p_md->i_refcount        = 1;
>>   
>>       vlc_cond_init(&p_md->parsed_cond);
>>       vlc_mutex_init(&p_md->parsed_lock);
>> @@ -547,7 +547,9 @@ void libvlc_media_release( libvlc_media_t *p_md )
>>       if (!p_md)
>>           return;
>>   
>> -    if(!vlc_atomic_rc_dec( &p_md->refcount ))
>> +    p_md->i_refcount--;
>> +
>> +    if( p_md->i_refcount > 0 )
>>           return;
>>   
>>       uninstall_input_item_observer( p_md );
>> @@ -583,7 +585,7 @@ void libvlc_media_release( libvlc_media_t *p_md )
>>   void libvlc_media_retain( libvlc_media_t *p_md )
>>   {
>>       assert (p_md);
>> -    vlc_atomic_rc_inc(&p_md->refcount);
>> +    p_md->i_refcount++;
>>   }
>>   
>>   /**************************************************************************
>> diff --git a/lib/media_internal.h b/lib/media_internal.h
>> index cfeb056178..aefc731c68 100644
>> --- a/lib/media_internal.h
>> +++ b/lib/media_internal.h
>> @@ -29,13 +29,12 @@
>>   
>>   #include <vlc_common.h>
>>   #include <vlc_input.h>
>> -#include <vlc_atomic.h>
>>   
>>   struct libvlc_media_t
>>   {
>>       libvlc_event_manager_t event_manager;
>>       input_item_t      *p_input_item;
>> -    vlc_atomic_rc_t   refcount;
>> +    int                i_refcount;
>>       libvlc_instance_t *p_libvlc_instance;
>>       libvlc_state_t     state;
>>       VLC_FORWARD_DECLARE_OBJECT(libvlc_media_list_t*) p_subitems; /* A
>> media descriptor can have Sub items. This is the only dependancy we
>> really have on media_list */
>>
> 
> I can't find back the rational for reverting this commit, but with a708c988091d6bc770212f5deeaba45e2395f4b2 it seems to be required, since the refcount will be accessed from the preparser thread & the libvlc_media_parse_with_options thread, as can be seen here: https://code.videolan.org/videolan/medialibrary/-/jobs/487725

There's this thread
https://mailman.videolan.org/pipermail/vlc-devel/2019-October/128362.html

> Any objection in re-introducing this commit?

No objection.