From 298a146754e35cbc650aa991ebff1a41eefdbe80 Mon Sep 17 00:00:00 2001
From: Tom Cherry <tomcherry@google.com>
Date: Tue, 28 Feb 2017 14:07:09 -0800
Subject: Check for spurious wake ups

Condition::wait() can spuriously wake up, so we must guard it with
another check to ensure that a given wake was truly due to having
been signaled.

Bug: 34592766
Test: Boot bullhead
Change-Id: Iaa5a0ca6186aea50c51e2c402ef95d7ba861be92
---
 libs/hwui/renderthread/RenderProxy.cpp  | 4 +++-
 libs/hwui/renderthread/RenderTask.cpp   | 1 +
 libs/hwui/renderthread/RenderTask.h     | 4 +++-
 libs/hwui/renderthread/RenderThread.cpp | 4 +++-
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/libs/hwui/renderthread/RenderProxy.cpp b/libs/hwui/renderthread/RenderProxy.cpp
index a734401a2be6..ce13ebc5e054 100644
--- a/libs/hwui/renderthread/RenderProxy.cpp
+++ b/libs/hwui/renderthread/RenderProxy.cpp
@@ -685,7 +685,9 @@ void* RenderProxy::postAndWait(MethodInvokeRenderTask* task) {
     SignalingRenderTask syncTask(task, &mSyncMutex, &mSyncCondition);
     AutoMutex _lock(mSyncMutex);
     mRenderThread.queue(&syncTask);
-    mSyncCondition.wait(mSyncMutex);
+    while (!syncTask.hasRun()) {
+        mSyncCondition.wait(mSyncMutex);
+    }
     return retval;
 }
 
diff --git a/libs/hwui/renderthread/RenderTask.cpp b/libs/hwui/renderthread/RenderTask.cpp
index b14f580791c5..928a4ef7fb53 100644
--- a/libs/hwui/renderthread/RenderTask.cpp
+++ b/libs/hwui/renderthread/RenderTask.cpp
@@ -26,6 +26,7 @@ namespace renderthread {
 void SignalingRenderTask::run() {
     mTask->run();
     mLock->lock();
+    mHasRun = true;
     mSignal->signal();
     mLock->unlock();
 }
diff --git a/libs/hwui/renderthread/RenderTask.h b/libs/hwui/renderthread/RenderTask.h
index 9ea671be5b86..a7acf91cbdb1 100644
--- a/libs/hwui/renderthread/RenderTask.h
+++ b/libs/hwui/renderthread/RenderTask.h
@@ -60,13 +60,15 @@ class SignalingRenderTask : public RenderTask {
 public:
     // Takes ownership of task, caller owns lock and signal
     SignalingRenderTask(RenderTask* task, Mutex* lock, Condition* signal)
-            : mTask(task), mLock(lock), mSignal(signal) {}
+            : mTask(task), mLock(lock), mSignal(signal), mHasRun(false) {}
     virtual void run() override;
+    bool hasRun() const { return mHasRun; }
 
 private:
     RenderTask* mTask;
     Mutex* mLock;
     Condition* mSignal;
+    bool mHasRun;
 };
 
 typedef void* (*RunnableMethod)(void* data);
diff --git a/libs/hwui/renderthread/RenderThread.cpp b/libs/hwui/renderthread/RenderThread.cpp
index 9c10c4fdbad1..f383adc9f644 100644
--- a/libs/hwui/renderthread/RenderThread.cpp
+++ b/libs/hwui/renderthread/RenderThread.cpp
@@ -345,7 +345,9 @@ void RenderThread::queueAndWait(RenderTask* task) {
 
     AutoMutex _lock(mutex);
     queue(&syncTask);
-    condition.wait(mutex);
+    while (!syncTask.hasRun()) {
+        condition.wait(mutex);
+    }
 }
 
 void RenderThread::queueAtFront(RenderTask* task) {
-- 
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