From a2e2c056d9ce33f6354bea92025837e62f9026ec Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom1v@videolabs.io>
Date: Thu, 8 Jul 2021 16:17:45 +0200
Subject: [PATCH] clock: expose lock

This is a first step to allow the caller to compute an arbitrary
deadline based on vlc_clock_ConvertToSystemLocked() then wait using
vlc_clock_Wait() without race condition.
---
 src/clock/clock.c               | 35 +++++++++++++++++++++++----------
 src/clock/clock.h               | 31 +++++++++++++++++++++++++++--
 src/video_output/video_output.c |  2 ++
 3 files changed, 56 insertions(+), 12 deletions(-)

diff --git a/src/clock/clock.c b/src/clock/clock.c
index 0daf456d22..cd3b07f946 100644
--- a/src/clock/clock.c
+++ b/src/clock/clock.c
@@ -346,11 +346,30 @@ static vlc_tick_t vlc_clock_slave_set_delay(vlc_clock_t *clock, vlc_tick_t delay
     return 0;
 }
 
-void vlc_clock_Wait(vlc_clock_t *clock, vlc_tick_t system_now, vlc_tick_t ts,
-                   double rate, vlc_tick_t max_duration)
+void vlc_clock_Lock(vlc_clock_t *clock)
 {
     vlc_clock_main_t *main_clock = clock->owner;
     vlc_mutex_lock(&main_clock->lock);
+}
+
+void vlc_clock_Unlock(vlc_clock_t *clock)
+{
+    vlc_clock_main_t *main_clock = clock->owner;
+    vlc_mutex_unlock(&main_clock->lock);
+}
+
+static inline void AssertLocked(vlc_clock_t *clock)
+{
+    vlc_clock_main_t *main_clock = clock->owner;
+    vlc_mutex_assert(&main_clock->lock);
+}
+
+void vlc_clock_Wait(vlc_clock_t *clock, vlc_tick_t system_now, vlc_tick_t ts,
+                   double rate, vlc_tick_t max_duration)
+{
+    AssertLocked(clock);
+
+    vlc_clock_main_t *main_clock = clock->owner;
     const vlc_tick_t max_deadline =
         max_duration > 0 ? system_now + max_duration : VLC_TICK_MAX;
     while (!main_clock->abort)
@@ -365,7 +384,6 @@ void vlc_clock_Wait(vlc_clock_t *clock, vlc_tick_t system_now, vlc_tick_t ts,
         if (vlc_cond_timedwait(&main_clock->cond, &main_clock->lock, deadline))
             break;
     }
-    vlc_mutex_unlock(&main_clock->lock);
 }
 
 vlc_clock_main_t *vlc_clock_main_New(struct vlc_logger *parent_logger)
@@ -516,14 +534,11 @@ vlc_tick_t vlc_clock_SetDelay(vlc_clock_t *clock, vlc_tick_t delay)
     return clock->set_delay(clock, delay);
 }
 
-vlc_tick_t vlc_clock_ConvertToSystem(vlc_clock_t *clock, vlc_tick_t system_now,
-                                     vlc_tick_t ts, double rate)
+vlc_tick_t vlc_clock_ConvertToSystemLocked(vlc_clock_t *clock,
+                                           vlc_tick_t system_now, vlc_tick_t ts,
+                                           double rate)
 {
-    vlc_clock_main_t *main_clock = clock->owner;
-    vlc_mutex_lock(&main_clock->lock);
-    vlc_tick_t system = clock->to_system_locked(clock, system_now, ts, rate);
-    vlc_mutex_unlock(&main_clock->lock);
-    return system;
+    return clock->to_system_locked(clock, system_now, ts, rate);
 }
 
 void vlc_clock_ConvertArrayToSystem(vlc_clock_t *clock, vlc_tick_t system_now,
diff --git a/src/clock/clock.h b/src/clock/clock.h
index eff0114f0c..17a5189837 100644
--- a/src/clock/clock.h
+++ b/src/clock/clock.h
@@ -173,18 +173,45 @@ void vlc_clock_Reset(vlc_clock_t *clock);
  */
 vlc_tick_t vlc_clock_SetDelay(vlc_clock_t *clock, vlc_tick_t ts_delay);
 
+/**
+ * Lock the clock mutex
+ */
+void vlc_clock_Lock(vlc_clock_t *clock);
+
+/**
+ * Unlock the clock mutex
+ */
+void vlc_clock_Unlock(vlc_clock_t *clock);
+
 /**
  * Wait for a timestamp expressed in stream time
+ *
+ * The clock mutex must be locked.
  */
 void vlc_clock_Wait(vlc_clock_t *clock, vlc_tick_t system_now, vlc_tick_t ts,
                    double rate, vlc_tick_t max_duration);
 
 /**
  * This function converts a timestamp from stream to system
+ *
+ * The clock mutex must be locked.
+ *
  * @return the valid system time or VLC_TICK_MAX when the clock is paused
  */
-vlc_tick_t vlc_clock_ConvertToSystem(vlc_clock_t *clock, vlc_tick_t system_now,
-                                     vlc_tick_t ts, double rate);
+vlc_tick_t vlc_clock_ConvertToSystemLocked(vlc_clock_t *clock,
+                                           vlc_tick_t system_now, vlc_tick_t ts,
+                                           double rate);
+
+static inline vlc_tick_t
+vlc_clock_ConvertToSystem(vlc_clock_t *clock, vlc_tick_t system_now,
+                          vlc_tick_t ts, double rate)
+{
+    vlc_clock_Lock(clock);
+    vlc_tick_t system =
+        vlc_clock_ConvertToSystemLocked(clock, system_now, ts, rate);
+    vlc_clock_Unlock(clock);
+    return system;
+}
 
 /**
  * This functon converts an array of timestamp from stream to system
diff --git a/src/video_output/video_output.c b/src/video_output/video_output.c
index 5150894a09..494ba1ebf6 100644
--- a/src/video_output/video_output.c
+++ b/src/video_output/video_output.c
@@ -1330,8 +1330,10 @@ static int RenderPicture(vout_thread_sys_t *vout, bool render_now)
         {
             /* Wait to reach system_pts if the plugin doesn't handle
              * asynchronous display */
+            vlc_clock_Lock(sys->clock);
             vlc_clock_Wait(sys->clock, system_now, pts, sys->rate,
                            VOUT_REDISPLAY_DELAY);
+            vlc_clock_Unlock(sys->clock);
 
             /* Don't touch system_pts. Tell the clock that the pts was rendered
              * at the expected date */