Android EGL: Synchronize calls to eglSwapBuffers and eglMakeCurrent

webrtc/api/java/android/org/webrtc/EglBase14.java

Index: webrtc/api/java/android/org/webrtc/EglBase14.java
diff --git a/webrtc/api/java/android/org/webrtc/EglBase14.java b/webrtc/api/java/android/org/webrtc/EglBase14.java
index 5b377e0bad1a073800f7f2c9dc25d304004868a9..6ac61d062ca9baa36599197cb7d0d520cff8756c 100644
--- a/webrtc/api/java/android/org/webrtc/EglBase14.java
+++ b/webrtc/api/java/android/org/webrtc/EglBase14.java
@@ -168,17 +168,21 @@ public final class EglBase14 extends EglBase {
     if (eglSurface == EGL14.EGL_NO_SURFACE) {
       throw new RuntimeException("No EGLSurface - can't make current");
     }
-    if (!EGL14.eglMakeCurrent(eglDisplay, eglSurface, eglSurface, eglContext)) {
-      throw new RuntimeException("eglMakeCurrent failed");
+    synchronized (EglBase.lock) {
+      if (!EGL14.eglMakeCurrent(eglDisplay, eglSurface, eglSurface, eglContext)) {
+        throw new RuntimeException("eglMakeCurrent failed");
+      }
     }
   }
 
   // Detach the current EGL context, so that it can be made current on another thread.
   @Override
   public void detachCurrent() {
-    if (!EGL14.eglMakeCurrent(
-        eglDisplay, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_CONTEXT)) {
-      throw new RuntimeException("eglMakeCurrent failed");
+    synchronized (EglBase.lock) {
+      if (!EGL14.eglMakeCurrent(
+          eglDisplay, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_CONTEXT)) {
+        throw new RuntimeException("eglDetachCurrent failed");
+      }
     }
   }
 
@@ -188,7 +192,9 @@ public final class EglBase14 extends EglBase {
     if (eglSurface == EGL14.EGL_NO_SURFACE) {
       throw new RuntimeException("No EGLSurface - can't swap buffers");
     }
-    EGL14.eglSwapBuffers(eglDisplay, eglSurface);
+    synchronized (EglBase.lock) {
+      EGL14.eglSwapBuffers(eglDisplay, eglSurface);
+    }
   }
 
   public void swapBuffers(long timeStampNs) {
@@ -196,9 +202,11 @@ public final class EglBase14 extends EglBase {
     if (eglSurface == EGL14.EGL_NO_SURFACE) {
       throw new RuntimeException("No EGLSurface - can't swap buffers");
     }
-    // See https://android.googlesource.com/platform/frameworks/native/+/tools_r22.2/opengl/specs/EGL_ANDROID_presentation_time.txt
-    EGLExt.eglPresentationTimeANDROID(eglDisplay, eglSurface, timeStampNs);
-    EGL14.eglSwapBuffers(eglDisplay, eglSurface);
+    synchronized (EglBase.lock) {
+      // See https://android.googlesource.com/platform/frameworks/native/+/tools_r22.2/opengl/specs/EGL_ANDROID_presentation_time.txt
+      EGLExt.eglPresentationTimeANDROID(eglDisplay, eglSurface, timeStampNs);
+      EGL14.eglSwapBuffers(eglDisplay, eglSurface);
+    }
   }
 
   // Return an EGLDisplay, or die trying.