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

@@ -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;
 }
 

libs/hwui/renderthread/RenderTask.cpp

@@ -26,6 +26,7 @@ namespace renderthread {
 void SignalingRenderTask::run() {
     mTask->run();
     mLock->lock();
+    mHasRun = true;
     mSignal->signal();
     mLock->unlock();
 }

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);

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) {