Layer: Use raw pointers for Current/Drawing parent

We should only be reading/writing this from the main thread
and likewise we only delete layers on the main thread and
so using raw pointers and managing the lifetime from the
Layer destructor will be safe. This significantly decreases
overhead in various code that traverses via parent (getAlpha,
isVisible, etc...).

Test: Existing tests pass. simpleperf
Bug: 186200583
Change-Id: I45745f7c865177ddfe9105d1440a9fa8f3470823

6 files changed, 54 insertions, 42 deletions

diff --git a/services/surfaceflinger/BufferLayer.cpp b/services/surfaceflinger/BufferLayer.cpp
index 8de43e0fe6..82c91e7d30 100644
--- a/services/surfaceflinger/BufferLayer.cpp
+++ b/services/surfaceflinger/BufferLayer.cpp
@@ -223,7 +223,7 @@ std::optional<compositionengine::LayerFE::LayerSettings> BufferLayer::prepareCli
          * of a camera where the buffer remains in native orientation,
          * we want the pixels to always be upright.
          */
-        sp<Layer> p = mDrawingParent.promote();
+        auto p = mDrawingParent;
         if (p != nullptr) {
             const auto parentTransform = p->getTransform();
             tr = tr * inverseOrientation(parentTransform.getOrientation());
diff --git a/services/surfaceflinger/BufferStateLayer.cpp b/services/surfaceflinger/BufferStateLayer.cpp
index 4eeaba154f..ba193c3be2 100644
--- a/services/surfaceflinger/BufferStateLayer.cpp
+++ b/services/surfaceflinger/BufferStateLayer.cpp
@@ -989,7 +989,7 @@ void BufferStateLayer::tracePendingBufferCount(int32_t pendingBuffers) {
  * how to go from screen space back to window space.
  */
 ui::Transform BufferStateLayer::getInputTransform() const {
-    sp<Layer> parent = mDrawingParent.promote();
+    auto parent = mDrawingParent;
     if (parent == nullptr) {
         return ui::Transform();
     }
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 4f4a897084..5707c67a56 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -179,9 +179,23 @@ Layer::~Layer() {
     if (mDrawingState.sidebandStream != nullptr) {
         mFlinger->mTunnelModeEnabledReporter->decrementTunnelModeCount();
     }
+
     if (mHadClonedChild) {
         mFlinger->mNumClones--;
     }
+
+    for (auto const& child : mCurrentChildren) {
+        if (child->mCurrentParent == this) child->mCurrentParent = nullptr;
+        if (child->mDrawingParent == this) {
+            child->mDrawingParent = nullptr;
+        }
+    }
+    for (auto const& child : mDrawingChildren) {
+        if (child->mCurrentParent == this) child->mCurrentParent = nullptr;
+        if (child->mDrawingParent == this) {
+            child->mDrawingParent = nullptr;
+        }
+    }
 }
 
 LayerCreationArgs::LayerCreationArgs(SurfaceFlinger* flinger, sp<Client> client, std::string name,
@@ -237,7 +251,7 @@ void Layer::removeFromCurrentState() {
 }
 
 sp<Layer> Layer::getRootLayer() {
-    sp<Layer> parent = getParent();
+    auto parent = getParent();
     if (parent == nullptr) {
         return this;
     }
@@ -662,7 +676,7 @@ bool Layer::isSecure() const {
         return true;
     }
 
-    const auto p = mDrawingParent.promote();
+    const auto p = mDrawingParent;
     return (p != nullptr) ? p->isSecure() : false;
 }
 
@@ -845,7 +859,7 @@ bool Layer::isTrustedOverlay() const {
     if (getDrawingState().isTrustedOverlay) {
         return true;
     }
-    const auto& p = mDrawingParent.promote();
+    const auto p = mDrawingParent;
     return (p != nullptr) && p->isTrustedOverlay();
 }
 
@@ -1025,7 +1039,7 @@ int32_t Layer::getFrameRateSelectionPriority() const {
         return mDrawingState.frameRateSelectionPriority;
     }
     // If not, search whether its parents have it set.
-    sp<Layer> parent = getParent();
+    auto parent = getParent();
     if (parent != nullptr) {
         return parent->getFrameRateSelectionPriority();
     }
@@ -1038,10 +1052,11 @@ bool Layer::isLayerFocusedBasedOnPriority(int32_t priority) {
 };
 
 ui::LayerStack Layer::getLayerStack() const {
-    if (const auto parent = mDrawingParent.promote()) {
-        return parent->getLayerStack();
+    auto p = mDrawingParent;
+    if (p == nullptr) {
+        return getDrawingState().layerStack;
     }
-    return getDrawingState().layerStack;
+    return mDrawingParent->getLayerStack();
 }
 
 bool Layer::setShadowRadius(float shadowRadius) {
@@ -1086,7 +1101,7 @@ StretchEffect Layer::getStretchEffect() const {
         return mDrawingState.stretchEffect;
     }
 
-    sp<Layer> parent = getParent();
+    auto parent = mDrawingParent;
     if (parent != nullptr) {
         auto effect = parent->getStretchEffect();
         if (effect.hasEffect()) {
@@ -1301,7 +1316,7 @@ Layer::FrameRate Layer::getFrameRateForLayerTree() const {
 
 bool Layer::isHiddenByPolicy() const {
     const State& s(mDrawingState);
-    const auto& parent = mDrawingParent.promote();
+    auto parent = mDrawingParent;
     if (parent != nullptr && parent->isHiddenByPolicy()) {
         return true;
     }
@@ -1348,7 +1363,7 @@ LayerDebugInfo Layer::getLayerDebugInfo(const DisplayDevice* display) const {
     LayerDebugInfo info;
     const State& ds = getDrawingState();
     info.mName = getName();
-    sp<Layer> parent = mDrawingParent.promote();
+    auto parent = mDrawingParent;
     info.mParentName = parent ? parent->getName() : "none"s;
     info.mType = getType();
     info.mTransparentRegion = ds.activeTransparentRegion_legacy;
@@ -1580,7 +1595,7 @@ ssize_t Layer::removeChild(const sp<Layer>& layer) {
 
 void Layer::setChildrenDrawingParent(const sp<Layer>& newParent) {
     for (const sp<Layer>& child : mDrawingChildren) {
-        child->mDrawingParent = newParent;
+        child->mDrawingParent = newParent.get();
         child->computeBounds(newParent->mBounds, newParent->mEffectiveTransform,
                              newParent->mEffectiveShadowRadius);
     }
@@ -1600,7 +1615,7 @@ bool Layer::reparent(const sp<IBinder>& newParentHandle) {
         }
     }
 
-    sp<Layer> parent = getParent();
+    auto parent = getParent();
     if (parent != nullptr) {
         parent->removeChild(this);
     }
@@ -1635,7 +1650,7 @@ bool Layer::setColorTransform(const mat4& matrix) {
 
 mat4 Layer::getColorTransform() const {
     mat4 colorTransform = mat4(getDrawingState().colorTransform);
-    if (sp<Layer> parent = mDrawingParent.promote(); parent != nullptr) {
+    if (auto parent = mDrawingParent; parent != nullptr) {
         colorTransform = parent->getColorTransform() * colorTransform;
     }
     return colorTransform;
@@ -1643,7 +1658,7 @@ mat4 Layer::getColorTransform() const {
 
 bool Layer::hasColorTransform() const {
     bool hasColorTransform = getDrawingState().hasColorTransform;
-    if (sp<Layer> parent = mDrawingParent.promote(); parent != nullptr) {
+    if (auto parent = mDrawingParent; parent != nullptr) {
         hasColorTransform = hasColorTransform || parent->hasColorTransform();
     }
     return hasColorTransform;
@@ -1657,7 +1672,7 @@ bool Layer::isLegacyDataSpace() const {
 }
 
 void Layer::setParent(const sp<Layer>& layer) {
-    mCurrentParent = layer;
+    mCurrentParent = layer.get();
 }
 
 int32_t Layer::getZ(LayerVector::StateSet) const {
@@ -1861,7 +1876,7 @@ ui::Transform Layer::getTransform() const {
 }
 
 half Layer::getAlpha() const {
-    const auto& p = mDrawingParent.promote();
+    auto p = mDrawingParent;
 
     half parentAlpha = (p != nullptr) ? p->getAlpha() : 1.0_hf;
     return parentAlpha * getDrawingState().color.a;
@@ -1872,7 +1887,7 @@ ui::Transform::RotationFlags Layer::getFixedTransformHint() const {
     if (fixedTransformHint != ui::Transform::ROT_INVALID) {
         return fixedTransformHint;
     }
-    const auto& p = mCurrentParent.promote();
+    auto p = mCurrentParent;
     if (!p) return fixedTransformHint;
     return p->getFixedTransformHint();
 }
@@ -1883,7 +1898,7 @@ half4 Layer::getColor() const {
 }
 
 int32_t Layer::getBackgroundBlurRadius() const {
-    const auto& p = mDrawingParent.promote();
+    auto p = mDrawingParent;
 
     half parentAlpha = (p != nullptr) ? p->getAlpha() : 1.0_hf;
     return parentAlpha * getDrawingState().backgroundBlurRadius;
@@ -1901,9 +1916,8 @@ const std::vector<BlurRegion> Layer::getBlurRegions() const {
 Layer::RoundedCornerState Layer::getRoundedCornerState() const {
     // Get parent settings
     RoundedCornerState parentSettings;
-    const auto& parent = mDrawingParent.promote();
-    if (parent != nullptr) {
-        parentSettings = parent->getRoundedCornerState();
+    if (mDrawingParent != nullptr) {
+        parentSettings = mDrawingParent->getRoundedCornerState();
         if (parentSettings.radius > 0) {
             ui::Transform t = getActiveTransform(getDrawingState());
             t = t.inverse();
@@ -2119,7 +2133,7 @@ void Layer::writeToProtoCommonState(LayerProto* layerInfo, LayerVector::StateSet
         LayerProtoHelper::writeToProtoDeprecated(requestedTransform,
                                                  layerInfo->mutable_requested_transform());
 
-        auto parent = useDrawing ? mDrawingParent.promote() : mCurrentParent.promote();
+        auto parent = useDrawing ? mDrawingParent : mCurrentParent;
         if (parent != nullptr) {
             layerInfo->set_parent(parent->sequence);
         } else {
@@ -2266,9 +2280,9 @@ void Layer::fillInputFrameInfo(WindowInfo& info, const ui::Transform& displayTra
 }
 
 void Layer::fillTouchOcclusionMode(WindowInfo& info) {
-    sp<Layer> p = this;
+    Layer* p = this;
     while (p != nullptr && !p->hasInputInfo()) {
-        p = p->mDrawingParent.promote();
+        p = p->mDrawingParent;
     }
     if (p != nullptr) {
         info.touchOcclusionMode = p->mDrawingState.inputInfo.touchOcclusionMode;
@@ -2280,9 +2294,8 @@ gui::DropInputMode Layer::getDropInputMode() const {
     if (mode == gui::DropInputMode::ALL) {
         return mode;
     }
-    sp<Layer> parent = mDrawingParent.promote();
-    if (parent) {
-        gui::DropInputMode parentMode = parent->getDropInputMode();
+    if (mDrawingParent) {
+        gui::DropInputMode parentMode = mDrawingParent->getDropInputMode();
         if (parentMode != gui::DropInputMode::NONE) {
             return parentMode;
         }
@@ -2309,8 +2322,7 @@ void Layer::handleDropInputMode(gui::WindowInfo& info) const {
     }
 
     // Check if the parent has set an alpha on the layer
-    sp<Layer> parent = mDrawingParent.promote();
-    if (parent && parent->getAlpha() != 1.0_hf) {
+    if (mDrawingParent && mDrawingParent->getAlpha() != 1.0_hf) {
         info.inputFeatures |= WindowInfo::Feature::DROP_INPUT;
         ALOGV("Dropping input for %s as requested by policy because alpha=%f", getDebugName(),
               static_cast<float>(getAlpha()));
@@ -2408,10 +2420,10 @@ sp<Layer> Layer::getClonedRoot() {
     if (mClonedChild != nullptr) {
         return this;
     }
-    if (mDrawingParent == nullptr || mDrawingParent.promote() == nullptr) {
+    if (mDrawingParent == nullptr) {
         return nullptr;
     }
-    return mDrawingParent.promote()->getClonedRoot();
+    return mDrawingParent->getClonedRoot();
 }
 
 bool Layer::hasInputInfo() const {
@@ -2598,8 +2610,7 @@ bool Layer::isInternalDisplayOverlay() const {
         return true;
     }
 
-    sp<Layer> parent = mDrawingParent.promote();
-    return parent && parent->isInternalDisplayOverlay();
+    return mDrawingParent && mDrawingParent->isInternalDisplayOverlay();
 }
 
 void Layer::setClonedChild(const sp<Layer>& clonedChild) {
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 8209c51ecb..07b2eb5130 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -795,12 +795,12 @@ public:
     // Returns index if removed, or negative value otherwise
     // for symmetry with Vector::remove
     ssize_t removeChild(const sp<Layer>& layer);
-    sp<Layer> getParent() const { return mCurrentParent.promote(); }
 
     // Should be called with the surfaceflinger statelock held
     bool isAtRoot() const { return mIsAtRoot; }
     void setIsAtRoot(bool isAtRoot) { mIsAtRoot = isAtRoot; }
 
+    Layer* getParent() const { return mCurrentParent; }
     bool hasParent() const { return getParent() != nullptr; }
     Rect getScreenBounds(bool reduceTransparentRegion = true) const;
     bool setChildLayer(const sp<Layer>& childLayer, int32_t z);
@@ -1007,8 +1007,8 @@ protected:
     LayerVector mCurrentChildren{LayerVector::StateSet::Current};
     LayerVector mDrawingChildren{LayerVector::StateSet::Drawing};
 
-    wp<Layer> mCurrentParent;
-    wp<Layer> mDrawingParent;
+    Layer* mCurrentParent = nullptr;
+    Layer* mDrawingParent = nullptr;
 
     // Window types from WindowManager.LayoutParams
     const gui::WindowInfo::Type mWindowType;
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 81f20edca1..acb81dc41c 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -3412,6 +3412,7 @@ status_t SurfaceFlinger::addClientLayer(const sp<Client>& client, const sp<IBind
     states.add(composerState);
 
     lbc->updateTransformHint(mActiveDisplayTransformHint);
+
     if (outTransformHint) {
         *outTransformHint = mActiveDisplayTransformHint;
     }
@@ -3956,7 +3957,7 @@ uint32_t SurfaceFlinger::setClientStateLocked(
     }
     if (what & layer_state_t::eLayerChanged) {
         // NOTE: index needs to be calculated before we update the state
-        const auto& p = layer->getParent();
+        auto p = layer->getParent();
         if (p == nullptr) {
             ssize_t idx = mCurrentState.layersSortedByZ.indexOf(layer);
             if (layer->setLayer(s.z) && idx >= 0) {
@@ -3974,7 +3975,7 @@ uint32_t SurfaceFlinger::setClientStateLocked(
     }
     if (what & layer_state_t::eRelativeLayerChanged) {
         // NOTE: index needs to be calculated before we update the state
-        const auto& p = layer->getParent();
+        auto p = layer->getParent();
         const auto& relativeHandle = s.relativeLayerSurfaceControl ?
                 s.relativeLayerSurfaceControl->getHandle() : nullptr;
         if (p == nullptr) {
@@ -6125,7 +6126,7 @@ status_t SurfaceFlinger::captureLayers(const LayerCaptureArgs& args,
                 return;
             }
 
-            sp<Layer> p = layer;
+            auto p = layer;
             while (p != nullptr) {
                 if (excludeLayers.count(p) != 0) {
                     return;
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index 7072439cea..db3b5722ec 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -289,7 +289,7 @@ public:
     }
 
     static void setLayerDrawingParent(const sp<Layer>& layer, const sp<Layer>& drawingParent) {
-        layer->mDrawingParent = drawingParent;
+        layer->mDrawingParent = drawingParent.get();
     }
 
     /* ------------------------------------------------------------------------