SurfaceFlinger: Disable early-release on multi displays

The current logic for handling multiple calls to onLayerDisplayed is
insufficient. For example if we did HWC comp followed by GL comp
on a single layer in a single compose cycle, FOLLOWING a previous
compose cycle in which we had done the same thing. The first time
we would enter the first conditional and clear the fence, but then the second
time we would enter the first conditional and keep it. We can't do this
though since the buffer was just used for HWC comp and we can't early
release it. To simplify things we only allow a single call to
onLayerDisplayed otherwise we disable the optimization. We can improve
this to re-enable the optimization with mirroring in the future
by tracking the state more carefully.

Bug: 221894151
Test: Run screenrecord and look for glitches
Change-Id: I73b5adac00d30750d4d79d0cbba9152df638d0e5

3 files changed, 11 insertions, 11 deletions

diff --git a/services/surfaceflinger/BufferLayer.cpp b/services/surfaceflinger/BufferLayer.cpp
index 0aca24ae70..0b23a5a5bb 100644
--- a/services/surfaceflinger/BufferLayer.cpp
+++ b/services/surfaceflinger/BufferLayer.cpp
@@ -362,6 +362,8 @@ void BufferLayer::onPostComposition(const DisplayDevice* display,
     // composition.
     if (!mBufferInfo.mFrameLatencyNeeded) return;
 
+    mAlreadyDisplayedThisCompose = false;
+
     // Update mFrameEventHistory.
     {
         Mutex::Autolock lock(mFrameEventHistoryMutex);
diff --git a/services/surfaceflinger/BufferStateLayer.cpp b/services/surfaceflinger/BufferStateLayer.cpp
index e6a76e8ea9..bcae8d9564 100644
--- a/services/surfaceflinger/BufferStateLayer.cpp
+++ b/services/surfaceflinger/BufferStateLayer.cpp
@@ -75,17 +75,15 @@ BufferStateLayer::~BufferStateLayer() {
 // -----------------------------------------------------------------------
 void BufferStateLayer::onLayerDisplayed(
         std::shared_future<renderengine::RenderEngineResult> futureRenderEngineResult) {
-    // If a layer has been displayed again we may need to clear
-    // the mLastClientComposition fence that we use for early release in setBuffer
-    // (as we now have a new fence which won't pass through the client composition path in some cases
-    //  e.g. screenshot). We expect one call to onLayerDisplayed after receiving the GL comp fence
-    // from a single composition cycle, and want to clear on the second call
-    // (which we track with mLastClientCompositionDisplayed)
-   if (mLastClientCompositionDisplayed) {
+    // If we are displayed on multiple displays in a single composition cycle then we would
+    // need to do careful tracking to enable the use of the mLastClientCompositionFence.
+    //  For example we can only use it if all the displays are client comp, and we need
+    //  to merge all the client comp fences. We could do this, but for now we just
+    // disable the optimization when a layer is composed on multiple displays.
+    if (mAlreadyDisplayedThisCompose) {
         mLastClientCompositionFence = nullptr;
-        mLastClientCompositionDisplayed = false;
-    } else if (mLastClientCompositionFence) {
-        mLastClientCompositionDisplayed = true;
+    } else {
+        mAlreadyDisplayedThisCompose = true;
     }
 
     // The previous release fence notifies the client that SurfaceFlinger is done with the previous
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 2b5e337095..0fb16f2f12 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -1049,7 +1049,7 @@ protected:
     mutable bool mDrawingStateModified = false;
 
     sp<Fence> mLastClientCompositionFence;
-    bool mLastClientCompositionDisplayed = false;
+    bool mAlreadyDisplayedThisCompose = false;
 private:
     virtual void setTransformHint(ui::Transform::RotationFlags) {}