[vlc-devel] [RFC] core: player: make the lock optionally reentrant

[Rémi Denis-Courmont]

Hi,

I don't see the point in adding a parameter here. If you want to use libpulse-like semantics, just make the lock recursive.

But in any case, this won't provide backward compatibility.

Le 13 mai 2019 15:47:36 GMT+03:00, Romain Vimont <rom1v at videolabs.io> a écrit :
>This will allow to implement the old libvlc API using the new player.
>
><https://mailman.videolan.org/pipermail/vlc-devel/2019-May/124461.html>
>---
> include/vlc_player.h  | 25 ++++++++++++++++++++++++-
> src/input/player.c    | 12 ++++++++----
> src/playlist/player.c |  3 ++-
> 3 files changed, 34 insertions(+), 6 deletions(-)
>
>diff --git a/include/vlc_player.h b/include/vlc_player.h
>index 1aa5f8e687..d4c49fa89d 100644
>--- a/include/vlc_player.h
>+++ b/include/vlc_player.h
>@@ -331,6 +331,29 @@ enum vlc_player_subtitle_sync
>     VLC_PLAYER_SUBTITLE_SYNC_APPLY,
> };
> 
>+/**
>+ * Player lock type (normal or reentrant)
>+ */
>+enum vlc_player_lock_type
>+{
>+    /**
>+     * Normal lock
>+     *
>+     * If the player is already locked, subsequent calls to
>vlc_player_Lock()
>+     * will deadlock.
>+     */
>+    VLC_PLAYER_LOCK_NORMAL,
>+
>+    /**
>+     * Reentrant lock
>+     *
>+     * If the player is already locked, subsequent calls to
>vlc_player_Lock()
>+     * will still succeed. To unlock the player, one call to
>+     * vlc_player_Unlock() per vlc_player_Lock() is necessary.
>+     */
>+    VLC_PLAYER_LOCK_REENTRANT,
>+};
>+
> /** Player capability: can seek */
> #define VLC_PLAYER_CAP_SEEK (1<<0)
> /** Player capability: can pause */
>@@ -1005,7 +1028,7 @@ vlc_player_title_list_GetAt(vlc_player_title_list
>*titles, size_t idx);
>* @return a pointer to a valid player instance or NULL in case of error
>  */
> VLC_API vlc_player_t *
>-vlc_player_New(vlc_object_t *parent,
>+vlc_player_New(vlc_object_t *parent, enum vlc_player_lock_type
>lock_type,
>                const struct vlc_player_media_provider *media_provider,
>                void *media_provider_data);
> 
>diff --git a/src/input/player.c b/src/input/player.c
>index da02375a66..e01701ba65 100644
>--- a/src/input/player.c
>+++ b/src/input/player.c
>@@ -3367,9 +3367,13 @@ vlc_player_vout_Snapshot(vlc_player_t *player)
> }
> 
> static void
>-vlc_player_InitLocks(vlc_player_t *player)
>+vlc_player_InitLocks(vlc_player_t *player, enum vlc_player_lock_type
>lock_type)
> {
>-    vlc_mutex_init(&player->lock);
>+    if (lock_type == VLC_PLAYER_LOCK_REENTRANT)
>+        vlc_mutex_init_recursive(&player->lock);
>+    else
>+        vlc_mutex_init(&player->lock);
>+
>     vlc_mutex_init(&player->vout_listeners_lock);
>     vlc_mutex_init(&player->aout_listeners_lock);
>     vlc_cond_init(&player->start_delay_cond);
>@@ -3426,7 +3430,7 @@ vlc_player_Delete(vlc_player_t *player)
> }
> 
> vlc_player_t *
>-vlc_player_New(vlc_object_t *parent,
>+vlc_player_New(vlc_object_t *parent, enum vlc_player_lock_type
>lock_type,
>                const struct vlc_player_media_provider *media_provider,
>                void *media_provider_data)
> {
>@@ -3514,7 +3518,7 @@ vlc_player_New(vlc_object_t *parent,
>     }
> 
>     player->deleting = false;
>-    vlc_player_InitLocks(player);
>+    vlc_player_InitLocks(player, lock_type);
> 
>if (vlc_clone(&player->destructor.thread, vlc_player_destructor_Thread,
>                   player, VLC_THREAD_PRIORITY_LOW) != 0)
>diff --git a/src/playlist/player.c b/src/playlist/player.c
>index bbdc39ba0e..8e3d94e2e8 100644
>--- a/src/playlist/player.c
>+++ b/src/playlist/player.c
>@@ -123,7 +123,8 @@ static const struct vlc_player_cbs player_callbacks
>= {
> bool
>vlc_playlist_PlayerInit(vlc_playlist_t *playlist, vlc_object_t *parent)
> {
>-    playlist->player = vlc_player_New(parent, &player_media_provider,
>playlist);
>+    playlist->player = vlc_player_New(parent, VLC_PLAYER_LOCK_NORMAL,
>+                                      &player_media_provider,
>playlist);
>     if (unlikely(!playlist->player))
>         return false;
> 
>-- 
>2.20.1
>
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