Merge "Actually do not hold WM lock while closing transaction" into oc-dev

2 files changed, 20 insertions, 1 deletions

diff --git a/services/core/java/com/android/server/wm/WindowAnimator.java b/services/core/java/com/android/server/wm/WindowAnimator.java
index aabf2bed1dd4..fe5b7f23d5e0 100644
--- a/services/core/java/com/android/server/wm/WindowAnimator.java
+++ b/services/core/java/com/android/server/wm/WindowAnimator.java
@@ -228,7 +228,10 @@ public class WindowAnimator {
             Slog.wtf(TAG, "Unhandled exception in Window Manager", e);
         } finally {
             if (transactionOpen) {
-                mService.closeSurfaceTransaction();
+
+                // Do not hold window manager lock while closing the transaction, as this might be
+                // blocking until the next frame, which can lead to total lock starvation.
+                mService.closeSurfaceTransaction(false /* withLockHeld */);
                 if (SHOW_TRANSACTIONS) Slog.i(TAG, "<<< CLOSE TRANSACTION animate");
             }
         }
diff --git a/services/core/java/com/android/server/wm/WindowManagerService.java b/services/core/java/com/android/server/wm/WindowManagerService.java
index e826aca5e2a7..947731efc221 100644
--- a/services/core/java/com/android/server/wm/WindowManagerService.java
+++ b/services/core/java/com/android/server/wm/WindowManagerService.java
@@ -893,10 +893,26 @@ public class WindowManagerService extends IWindowManager.Stub
     }
 
     void closeSurfaceTransaction() {
+        closeSurfaceTransaction(true /* withLockHeld */);
+    }
+
+    /**
+     * Closes a surface transaction.
+     *
+     * @param withLockHeld Whether to acquire the window manager while doing so. In some cases
+     *                     holding the lock my lead to starvation in WM in case closeTransaction
+     *                     blocks and we call it repeatedly, like we do for animations.
+     */
+    void closeSurfaceTransaction(boolean withLockHeld) {
         synchronized (mWindowMap) {
             if (mRoot.mSurfaceTraceEnabled) {
                 mRoot.mRemoteEventTrace.closeSurfaceTransaction();
             }
+            if (withLockHeld) {
+                SurfaceControl.closeTransaction();
+            }
+        }
+        if (!withLockHeld) {
             SurfaceControl.closeTransaction();
         }
     }