Fix ViewRootImpl traversal issue after SurfaceSyncGroup timeout

ViewRootImpl traversal is blocked from the time a sync is requested
to when the sync is successfully added to a SurfaceSyncGroup.
If the ViewRootImpl draw timeouts, the ViewRootImpl's
SurfaceSyncGroup is marked as ready. If there is another
sync request on the ViewRootImpl before the traversal path,
we can get in a state where we will never draw again.

Fix this by updating cleaning up the ViewRootImpl state
when the SurfaceSyncGroup is marked as ready.

Flag: EXEMPT bug fix
Bug: 362513091
Test: presubmit (coming in future cl)
Change-Id: I6c0ac8f96914d231cc9dc695f6fc8975ba2c5864

2 files changed, 43 insertions, 8 deletions

diff --git a/core/java/android/view/ViewRootImpl.java b/core/java/android/view/ViewRootImpl.java
index d46e1f29597e..4602e90dc01e 100644
--- a/core/java/android/view/ViewRootImpl.java
+++ b/core/java/android/view/ViewRootImpl.java
@@ -6971,9 +6971,7 @@ public final class ViewRootImpl implements ViewParent,
                     handleScrollCaptureRequest((IScrollCaptureResponseListener) msg.obj);
                     break;
                 case MSG_PAUSED_FOR_SYNC_TIMEOUT:
-                    Log.e(mTag, "Timedout waiting to unpause for sync");
-                    mNumPausedForSync = 0;
-                    scheduleTraversals();
+                    resumeAfterSyncTimeout();
                     break;
                 case MSG_CHECK_INVALIDATION_IDLE: {
                     long delta;
@@ -12766,6 +12764,15 @@ public final class ViewRootImpl implements ViewParent,
         activeSurfaceSyncGroup.addTransaction(t);
     }
 
+    /**
+     * Resume rendering after being paused for sync due to a timeout.
+     */
+    private void resumeAfterSyncTimeout() {
+        Log.e(mTag, "Timedout waiting to unpause for sync mNumPausedForSync=" + mNumPausedForSync);
+        mNumPausedForSync = 0;
+        scheduleTraversals();
+    }
+
     @Override
     public SurfaceSyncGroup getOrCreateSurfaceSyncGroup() {
         boolean newSyncGroup = false;
@@ -12793,6 +12800,16 @@ public final class ViewRootImpl implements ViewParent,
                 }
             });
             newSyncGroup = true;
+
+            // If the sync group is marked ready by a timeout, check if rendering is paused and
+            // if it is, resume rendering and trigger a traversal.
+            mActiveSurfaceSyncGroup.addSyncCompleteCallback(mExecutor, () -> {
+                if (mActiveSurfaceSyncGroup != null
+                        && mActiveSurfaceSyncGroup.isComplete() && mNumPausedForSync > 0) {
+                    mHandler.removeMessages(MSG_PAUSED_FOR_SYNC_TIMEOUT);
+                    resumeAfterSyncTimeout();
+                }
+            });
         }
 
         Trace.instant(Trace.TRACE_TAG_VIEW,
@@ -12807,12 +12824,20 @@ public final class ViewRootImpl implements ViewParent,
             }
         }
 
-        mNumPausedForSync++;
-        mHandler.removeMessages(MSG_PAUSED_FOR_SYNC_TIMEOUT);
-        mHandler.sendEmptyMessageDelayed(MSG_PAUSED_FOR_SYNC_TIMEOUT,
-                1000 * Build.HW_TIMEOUT_MULTIPLIER);
+        // The sync group can be marked ready by a timeout. This makes incrementing
+        // mNumPausedForSync racy. Here we check if the sync group is complete and
+        // if it is then we don't pause for syncing.
+        if (!mActiveSurfaceSyncGroup.isComplete()) {
+            mNumPausedForSync++;
+            mHandler.removeMessages(MSG_PAUSED_FOR_SYNC_TIMEOUT);
+            mHandler.sendEmptyMessageDelayed(MSG_PAUSED_FOR_SYNC_TIMEOUT,
+                    1000 * Build.HW_TIMEOUT_MULTIPLIER);
+        } else {
+            Log.d(mTag, "Active sync group is already completed "
+                    + mActiveSurfaceSyncGroup.getName());
+        }
         return mActiveSurfaceSyncGroup;
-    };
+    }
 
     private final Executor mSimpleExecutor = Runnable::run;
 
diff --git a/core/java/android/window/SurfaceSyncGroup.java b/core/java/android/window/SurfaceSyncGroup.java
index 5d14698c82b3..a68bdc05e20e 100644
--- a/core/java/android/window/SurfaceSyncGroup.java
+++ b/core/java/android/window/SurfaceSyncGroup.java
@@ -839,6 +839,16 @@ public final class SurfaceSyncGroup {
     }
 
     /**
+     * Returns true if the SurfaceSyncGroup has completed its sync.
+     * @hide
+     */
+    public boolean isComplete() {
+        synchronized (mLock) {
+            return mFinished;
+        }
+    }
+
+    /**
      * A frame callback that is used to synchronize SurfaceViews. The owner of the SurfaceView must
      * implement onFrameStarted when trying to sync the SurfaceView. This is to ensure the sync
      * knows when the frame is ready to add to the sync.