[vlc-devel] [PATCH 5/5] libvlc: player: use vlc_player

[Romain Vimont]

On Fri, May 10, 2019 at 11:41:09AM +0200, Romain Vimont wrote:
> On Thu, May 09, 2019 at 07:48:56PM +0300, Rémi Denis-Courmont wrote:
> > Le torstaina 9. toukokuuta 2019, 18.56.58 EEST Romain Vimont a écrit :
> > > @@ -340,16 +332,13 @@ int libvlc_audio_set_volume( libvlc_media_player_t
> > > *mp, int volume )
> > > ***************************************************************************
> > > **/ int libvlc_audio_get_track_count( libvlc_media_player_t *p_mi )
> > >  {
> > > -    input_thread_t *p_input_thread = libvlc_get_input_thread( p_mi );
> > > -    int i_track_count;
> > > +    vlc_player_t *player = p_mi->player;
> > > +    vlc_player_Lock(player);
> > > 
> > > -    if( !p_input_thread )
> > > -        return -1;
> > > +    int ret = vlc_player_GetTrackCount(p_mi->player, AUDIO_ES);
> > > 
> > > -    i_track_count = var_CountChoices( p_input_thread, "audio-es" );
> > > -
> > > -    input_Release(p_input_thread);
> > > -    return i_track_count;
> > > +    vlc_player_Unlock(player);
> > > +    return ret;
> > >  }
> > 
> > Application should (still) be allowed to call this, and most* other functions 
> > further down the patch, from within event callbacks. But this leads to 
> > deadlock or abort depending on build type.
> 
> Yes.
> 
> But we want to keep the libvlc API (which does not expose the lock to
> the client) unchanged, and we need to lock the player. So the lock must
> be recursive in some way:
>  1. always make the core vlc_player lock recursive;
>  2. make the vlc_player lock recursive on demand (a flag on creation);
>  3. use a wrapper in libvlc to expose a recursive lock from the
>     non-recursive vlc_player lock (using a thread-local storage bool).

s/bool/int/

But in fact, this may not work with a simple int, it would require one
thread-local variable per libvlc_media_player instance.

> I suggest 3.
> 
> What do you think?
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