commit 4340607f5f5c277eb031fdd1424fc8a1a69924e2
author Robert Carr <racarr@google.com> Wed Sep 19 13:22:47 2018 -0700
committer Robert Carr <racarr@google.com> Mon Oct 01 18:14:10 2018 -0700
tree 4f24cd346424d7bf107daa34da761d7aaacbe15a
parent 3fe5ead7632d6f9cb8ba7e06758faf836f4bea39

SurfaceFlinger: Allows Surfaces to outlive their parents.

Currently the only strong reference to a Layer is held by
their parent or the containing layer stack. This has a few
undesirable implications. Firstly, it means that we can not
create a SurfaceControl with a null parent. For example, a
media decoding library may wish to offer an unparented SurfaceControl
representing the decoding Surface, and allow the consumer to parent
it between various SurfaceControls as they wish. Secondly it requires
lifetime coordination between various levels of the hierarchy, when adding
a child you have to be careful to observe the lifetime of the parent because
your BufferQueue may become suddenly abandoned at any point. In this change
we switch to a reference counted model, such that the Layer remains valid
as long as there is a handle to it. We also end the behavior of passing on
BufferQueue abandon to children. Layers are only abandoned/disposed when
an explicit call to remove is made, or the last reference is dropped.

Bug: 62536731
Bug: 111373437
Bug: 111297488
Test: Transaction_test.cpp
Change-Id: I04cbc2368a1049b8ebd8913673ed4bfe05a26280

services/surfaceflinger/Layer.cpp

diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index f9bc1e7..63a010d 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -118,12 +118,6 @@
         c->detachLayer(this);
     }
 
-    for (auto& point : mRemoteSyncPoints) {
-        point->setTransactionApplied();
-    }
-    for (auto& point : mLocalSyncPoints) {
-        point->setFrameAvailable();
-    }
     mFrameTracker.logAndResetStats(mName);
 }
 
@@ -141,8 +135,6 @@
 void Layer::onRemovedFromCurrentState() {
     // the layer is removed from SF mCurrentState to mLayersPendingRemoval
 
-    mPendingRemoval = true;
-
     if (mCurrentState.zOrderRelativeOf != nullptr) {
         sp<Layer> strongRelative = mCurrentState.zOrderRelativeOf.promote();
         if (strongRelative != nullptr) {
@@ -151,7 +143,7 @@
         }
         mCurrentState.zOrderRelativeOf = nullptr;
     }
-
+    
     for (const auto& child : mCurrentChildren) {
         child->onRemovedFromCurrentState();
     }
@@ -163,8 +155,13 @@
 
     destroyAllHwcLayers();
 
-    for (const auto& child : mCurrentChildren) {
-        child->onRemoved();
+    mRemoved = true;
+
+    for (auto& point : mRemoteSyncPoints) {
+        point->setTransactionApplied();
+    }
+    for (auto& point : mLocalSyncPoints) {
+        point->setFrameAvailable();
     }
 }