[vlc-devel] [PATCH 4/4] libvlc: media: use vlc_atomic_rc for refcount

[Alexandre Janniaux]

Hi,

I've seen this but didn't find any issue that could link it
so didn't mention it (it's pretty obvious from the diff).

I don't really see why media would not be thread-safe to
release whereas every other object would be.

Regards,
--
Alexandre Janniaux
Videolabs

On Mon, Nov 23, 2020 at 08:03:19AM +0100, Steve Lhomme wrote:
> This one was not protected by a lock. Is it possible to do the calls from
> different threads now ? Or was it broken ?
>
> On 2020-11-21 13:21, Alexandre Janniaux wrote:
> > ---
> >   lib/media.c          | 9 ++++-----
> >   lib/media_internal.h | 4 +++-
> >   2 files changed, 7 insertions(+), 6 deletions(-)
> >
> > diff --git a/lib/media.c b/lib/media.c
> > index dd4faf0066..6f7911e0a2 100644
> > --- a/lib/media.c
> > +++ b/lib/media.c
> > @@ -37,6 +37,7 @@
> >   #include <vlc_meta.h>
> >   #include <vlc_url.h>
> >   #include <vlc_thumbnailer.h>
> > +#include <vlc_atomic.h>
> >   #include "../src/libvlc.h"
> > @@ -501,7 +502,7 @@ libvlc_media_t * libvlc_media_new_from_input_item(
> >       p_md->p_libvlc_instance = p_instance;
> >       p_md->p_input_item      = p_input_item;
> > -    p_md->i_refcount        = 1;
> > +    vlc_atomic_rc_init(&p_md->rc);
> >       vlc_cond_init(&p_md->parsed_cond);
> >       vlc_mutex_init(&p_md->parsed_lock);
> > @@ -643,9 +644,7 @@ void libvlc_media_release( libvlc_media_t *p_md )
> >       if (!p_md)
> >           return;
> > -    p_md->i_refcount--;
> > -
> > -    if( p_md->i_refcount > 0 )
> > +    if( !vlc_atomic_rc_dec(&p_md->rc) )
> >           return;
> >       uninstall_input_item_observer( p_md );
> > @@ -675,7 +674,7 @@ void libvlc_media_release( libvlc_media_t *p_md )
> >   void libvlc_media_retain( libvlc_media_t *p_md )
> >   {
> >       assert (p_md);
> > -    p_md->i_refcount++;
> > +    vlc_atomic_rc_inc( &p_md->rc );
> >   }
> >   // Duplicate a media descriptor object
> > diff --git a/lib/media_internal.h b/lib/media_internal.h
> > index e4d0d03fae..b8646abce2 100644
> > --- a/lib/media_internal.h
> > +++ b/lib/media_internal.h
> > @@ -35,10 +35,12 @@
> >   struct libvlc_media_t
> >   {
> >       libvlc_event_manager_t event_manager;
> > +
> >       input_item_t      *p_input_item;
> > -    int                i_refcount;
> >       libvlc_instance_t *p_libvlc_instance;
> >       libvlc_state_t     state;
> > +    vlc_atomic_rc_t    rc;
> > +
> >       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 */
> >       void *p_user_data;
> > --
> > 2.29.2
> >
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