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

[Romain Vimont]

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