[vlc-commits] vout: use atomic variables for stats instead of spin lock

[Rémi Denis-Courmont]

vlc | branch: master | Rémi Denis-Courmont <remi at remlab.net> | Fri Nov  9 00:36:33 2012 +0200| [a5e3a954b54587db0a7b47320f94ed7284122763] | committer: Rémi Denis-Courmont

vout: use atomic variables for stats instead of spin lock

> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=a5e3a954b54587db0a7b47320f94ed7284122763
---

 src/video_output/statistic.h    |   40 +++++++++++++++++++++------------------
 src/video_output/video_output.c |    4 ++--
 2 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/src/video_output/statistic.h b/src/video_output/statistic.h
index e17386e..083b0d7 100644
--- a/src/video_output/statistic.h
+++ b/src/video_output/statistic.h
@@ -22,39 +22,43 @@
  *****************************************************************************/
 
 #ifndef LIBVLC_VOUT_STATISTIC_H
-#define LIBVLC_VOUT_STATISTIC_H
+# define LIBVLC_VOUT_STATISTIC_H
+# include <vlc_atomic.h>
 
+/* NOTE: Both statistics are atomic on their own, so one might be older than
+ * the other one. Currently, only one of them is updated at a time, so this
+ * is a non-issue. */
 typedef struct {
-    vlc_spinlock_t spin;
-
-    int displayed;
-    int lost;
+    atomic_uint displayed;
+    atomic_uint lost;
 } vout_statistic_t;
 
 static inline void vout_statistic_Init(vout_statistic_t *stat)
 {
-    vlc_spin_init(&stat->spin);
+    atomic_init(&stat->displayed, 0);
+    atomic_init(&stat->lost, 0);
 }
+
 static inline void vout_statistic_Clean(vout_statistic_t *stat)
 {
-    vlc_spin_destroy(&stat->spin);
+    (void) stat;
 }
+
 static inline void vout_statistic_GetReset(vout_statistic_t *stat, int *displayed, int *lost)
 {
-    vlc_spin_lock(&stat->spin);
-    *displayed = stat->displayed;
-    *lost      = stat->lost;
+    *displayed = atomic_exchange(&stat->displayed, 0);
+    *lost      = atomic_exchange(&stat->lost, 0);
+}
 
-    stat->displayed = 0;
-    stat->lost      = 0;
-    vlc_spin_unlock(&stat->spin);
+static inline void vout_statistic_AddDisplayed(vout_statistic_t *stat,
+                                               int displayed)
+{
+    atomic_fetch_add(&stat->displayed, displayed);
 }
-static inline void vout_statistic_Update(vout_statistic_t *stat, int displayed, int lost)
+
+static inline void vout_statistic_AddLost(vout_statistic_t *stat, int lost)
 {
-    vlc_spin_lock(&stat->spin);
-    stat->displayed += displayed;
-    stat->lost      += lost;
-    vlc_spin_unlock(&stat->spin);
+    atomic_fetch_add(&stat->lost, lost);
 }
 
 #endif
diff --git a/src/video_output/video_output.c b/src/video_output/video_output.c
index 0a68cc8..b83d040 100644
--- a/src/video_output/video_output.c
+++ b/src/video_output/video_output.c
@@ -862,7 +862,7 @@ static int ThreadDisplayPreparePicture(vout_thread_t *vout, bool reuse, bool is_
 
     vlc_mutex_unlock(&vout->p->filter.lock);
 
-    vout_statistic_Update(&vout->p->statistic, 0, lost_count);
+    vout_statistic_AddLost(&vout->p->statistic, lost_count);
     if (!picture)
         return VLC_EGENERIC;
 
@@ -1056,7 +1056,7 @@ static int ThreadDisplayRenderPicture(vout_thread_t *vout, bool is_forced)
                          subpic);
     sys->display.filtered = NULL;
 
-    vout_statistic_Update(&vout->p->statistic, 1, 0);
+    vout_statistic_AddDisplayed(&vout->p->statistic, 1);
 
     return VLC_SUCCESS;
 }