Merge "Track the last release fence per layer stack" into main

3 files changed, 25 insertions, 28 deletions

diff --git a/libs/ui/include/ui/LayerStack.h b/libs/ui/include/ui/LayerStack.h
index d6ffeb7fad..f4c8ba250e 100644
--- a/libs/ui/include/ui/LayerStack.h
+++ b/libs/ui/include/ui/LayerStack.h
@@ -55,6 +55,10 @@ inline bool operator>(LayerStack lhs, LayerStack rhs) {
     return lhs.id > rhs.id;
 }
 
+inline bool operator<(LayerStack lhs, LayerStack rhs) {
+    return lhs.id < rhs.id;
+}
+
 // A LayerFilter determines if a layer is included for output to a display.
 struct LayerFilter {
     LayerStack layerStack;
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 4cc2f9e1e7..80eee15cea 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -15,7 +15,7 @@
  */
 
 // TODO(b/129481165): remove the #pragma below and fix conversion issues
-#include "TransactionCallbackInvoker.h"
+
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wconversion"
 
@@ -24,8 +24,6 @@
 #define LOG_TAG "Layer"
 #define ATRACE_TAG ATRACE_TAG_GRAPHICS
 
-#include "Layer.h"
-
 #include <android-base/properties.h>
 #include <android-base/stringprintf.h>
 #include <binder/IPCThreadState.h>
@@ -73,10 +71,12 @@
 #include "FrameTracer/FrameTracer.h"
 #include "FrontEnd/LayerCreationArgs.h"
 #include "FrontEnd/LayerHandle.h"
+#include "Layer.h"
 #include "LayerProtoHelper.h"
 #include "MutexUtils.h"
 #include "SurfaceFlinger.h"
 #include "TimeStats/TimeStats.h"
+#include "TransactionCallbackInvoker.h"
 #include "TunnelModeEnabledReporter.h"
 #include "Utils/FenceUtils.h"
 
@@ -2889,26 +2889,13 @@ void Layer::prepareReleaseCallbacks(ftl::Future<FenceResult> futureFenceResult,
         ch->previousReleaseFences.emplace_back(std::move(futureFenceResult));
         ch->name = mName;
     } else {
-        // If we didn't get a release callback yet, e.g. some scenarios when capturing
-        // screenshots asynchronously, then make sure we don't drop the fence.
-        mAdditionalPreviousReleaseFences.emplace_back(std::move(futureFenceResult));
-        std::vector<ftl::Future<FenceResult>> mergedFences;
-        sp<Fence> prevFence = nullptr;
-        // For a layer that's frequently screenshotted, try to merge fences to make sure we
-        // don't grow unbounded.
-        for (auto& futureReleaseFence : mAdditionalPreviousReleaseFences) {
-            auto result = futureReleaseFence.wait_for(0s);
-            if (result != std::future_status::ready) {
-                mergedFences.emplace_back(std::move(futureReleaseFence));
-                continue;
-            }
-            mergeFence(getDebugName(), futureReleaseFence.get().value_or(Fence::NO_FENCE),
-                       prevFence);
-        }
-        if (prevFence != nullptr) {
-            mergedFences.emplace_back(ftl::yield(FenceResult(std::move(prevFence))));
-        }
-        mAdditionalPreviousReleaseFences.swap(mergedFences);
+        // If we didn't get a release callback yet (e.g. some scenarios when capturing
+        // screenshots asynchronously) then make sure we don't drop the fence.
+        // Older fences for the same layer stack can be dropped when a new fence arrives.
+        // An assumption here is that RenderEngine performs work sequentially, so an
+        // incoming fence will not fire before an existing fence.
+        mAdditionalPreviousReleaseFences.emplace_or_replace(layerStack,
+                                                            std::move(futureFenceResult));
     }
 
     if (mBufferInfo.mBuffer) {
@@ -3458,10 +3445,10 @@ bool Layer::setTransactionCompletedListeners(const std::vector<sp<CallbackHandle
             handle->previousFrameNumber = mDrawingState.previousFrameNumber;
             if (FlagManager::getInstance().ce_fence_promise() &&
                 mPreviousReleaseBufferEndpoint == handle->listener) {
-                // Add fences from previous screenshots now so that they can be dispatched to the
+                // Add fence from previous screenshot now so that it can be dispatched to the
                 // client.
-                for (auto& futureReleaseFence : mAdditionalPreviousReleaseFences) {
-                    handle->previousReleaseFences.emplace_back(std::move(futureReleaseFence));
+                for (auto& [_, future] : mAdditionalPreviousReleaseFences) {
+                    handle->previousReleaseFences.emplace_back(std::move(future));
                 }
                 mAdditionalPreviousReleaseFences.clear();
             } else if (FlagManager::getInstance().screenshot_fence_preservation() &&
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index edf2ae260b..c094aa1656 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -18,6 +18,7 @@
 
 #include <android/gui/DropInputMode.h>
 #include <android/gui/ISurfaceComposerClient.h>
+#include <ftl/small_map.h>
 #include <gui/BufferQueue.h>
 #include <gui/LayerState.h>
 #include <gui/WindowInfo.h>
@@ -25,9 +26,11 @@
 #include <math/vec4.h>
 #include <sys/types.h>
 #include <ui/BlurRegion.h>
+#include <ui/DisplayMap.h>
 #include <ui/FloatRect.h>
 #include <ui/FrameStats.h>
 #include <ui/GraphicBuffer.h>
+#include <ui/LayerStack.h>
 #include <ui/PixelFormat.h>
 #include <ui/Region.h>
 #include <ui/StretchEffect.h>
@@ -952,8 +955,11 @@ public:
     // screenshots asynchronously. There may be no buffer update for the
     // layer, but the layer will still be composited on the screen in every
     // frame. Kepping track of these fences ensures that they are not dropped
-    // and can be dispatched to the client at a later time.
-    std::vector<ftl::Future<FenceResult>> mAdditionalPreviousReleaseFences;
+    // and can be dispatched to the client at a later time. Older fences are
+    // dropped when a layer stack receives a new fence.
+    // TODO(b/300533018): Track fence per multi-instance RenderEngine
+    ftl::SmallMap<ui::LayerStack, ftl::Future<FenceResult>, ui::kDisplayCapacity>
+            mAdditionalPreviousReleaseFences;
 
     // Exposed so SurfaceFlinger can assert that it's held
     const sp<SurfaceFlinger> mFlinger;