commit 194ff39de17ef4596b2b6ce1520516d7cc10fde6
author Josh Gao <jmgao@fb.com> Thu Sep 08 16:19:29 2022 -0700
committer Ying Wei <whisperwing@google.com> Thu Mar 30 18:01:58 2023 +0000
tree c4b412302c8bb831c1d13b95b1a4fa03e72667cb
parent a6e9dd2cb4da7f91f2379b44d3320cdb0f472f7c

SurfaceFlinger: add more thread-safety annotations.

As part of debugging a crash in SurfaceFlinger, we became suspicious of
markLayerPendingRemovalLocked because it wasn't annotated with thread
safety annotations. This ended up being a red herring, because
mStateLock is held on all paths into that function. Add some helpers to
MutexUtils.h to require/assert mutexes, and use them to sprinkle some
thread safety annotations to make things more clear.

Cherry-picked from aosp/2212955

Bug: 271644537
Test: m surfaceflinger
Change-Id: Ib48433765bb6ffcb351ec10cd5bc89e254b48545

services/surfaceflinger/Layer.cpp

diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 755e585..8dec57b 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -75,6 +75,7 @@
 #include "FrontEnd/LayerCreationArgs.h"
 #include "FrontEnd/LayerHandle.h"
 #include "LayerProtoHelper.h"
+#include "MutexUtils.h"
 #include "SurfaceFlinger.h"
 #include "TimeStats/TimeStats.h"
 #include "TunnelModeEnabledReporter.h"
@@ -305,10 +306,12 @@
     auto layersInTree = getRootLayer()->getLayersInTree(LayerVector::StateSet::Current);
     std::sort(layersInTree.begin(), layersInTree.end());
 
-    traverse(LayerVector::StateSet::Current, [&](Layer* layer) {
-        layer->removeFromCurrentState();
-        layer->removeRelativeZ(layersInTree);
-    });
+    REQUIRE_MUTEX(mFlinger->mStateLock);
+    traverse(LayerVector::StateSet::Current,
+             [&](Layer* layer) REQUIRES(layer->mFlinger->mStateLock) {
+                 layer->removeFromCurrentState();
+                 layer->removeRelativeZ(layersInTree);
+             });
 }
 
 void Layer::addToCurrentState() {
@@ -1009,10 +1012,12 @@
         mFlinger->mLayersAdded = true;
         // set up SF to handle added color layer
         if (isRemovedFromCurrentState()) {
+            MUTEX_ALIAS(mFlinger->mStateLock, mDrawingState.bgColorLayer->mFlinger->mStateLock);
             mDrawingState.bgColorLayer->onRemovedFromCurrentState();
         }
         mFlinger->setTransactionFlags(eTransactionNeeded);
     } else if (mDrawingState.bgColorLayer && alpha == 0) {
+        MUTEX_ALIAS(mFlinger->mStateLock, mDrawingState.bgColorLayer->mFlinger->mStateLock);
         mDrawingState.bgColorLayer->reparent(nullptr);
         mDrawingState.bgColorLayer = nullptr;
         return true;