Effects: Add atomic_wp<T>, update setThread.

atomic_wp<T> is used to allow concurrent read and write to the wp<>.
We use this to fix EffectCallback::setThread to resolve multithreaded
access to the wp<T>.

Note that setThread is used for EffectChain migration between
PlaybackThreads; we also need to refine higher level transactional
locking to ensure enable/disable of effect is done consistently
during migration.

Test: basic audio works
Test: atest media_synchronization_tests
Test: AudioEffectTest AudioPreProcessingTest BassBoostTest
Test: EnvReverbTest EqualizerTest LoudnessEnhancerTest
Test: PresetReverbTest VirtualizerTest VisualizerTest
Bug: 161341295
Change-Id: If80ee4373859c832d6fd10fec0385d69064f50c6
diff --git a/media/utils/tests/Android.bp b/media/utils/tests/Android.bp
new file mode 100644
index 0000000..bb413c3
--- /dev/null
+++ b/media/utils/tests/Android.bp
@@ -0,0 +1,19 @@
+cc_test {
+    name: "media_synchronization_tests",
+
+    cflags: [
+        "-Wall",
+        "-Werror",
+        "-Wextra",
+    ],
+
+    shared_libs: [
+        "liblog",
+        "libmediautils",
+        "libutils",
+    ],
+
+    srcs: [
+        "media_synchronization_tests.cpp",
+    ],
+}
diff --git a/media/utils/tests/media_synchronization_tests.cpp b/media/utils/tests/media_synchronization_tests.cpp
new file mode 100644
index 0000000..169768e
--- /dev/null
+++ b/media/utils/tests/media_synchronization_tests.cpp
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "media_synchronization_tests"
+
+#include <mediautils/Synchronization.h>
+
+#include <gtest/gtest.h>
+#include <utils/Log.h>
+
+using namespace android;
+using namespace android::mediautils;
+
+// Simple Test Class
+template <typename T>
+class MyObject : public RefBase {
+    T value_;
+  public:
+    MyObject(const T& value) : value_(value) {}
+    MyObject(const MyObject<T>& mo) : value_(mo.get()) {}
+    T get() const { return value_; }
+    void set(const T& value) { value_ = value; }
+};
+
+TEST(media_synchronization_tests, atomic_wp) {
+  sp<MyObject<int>> refobj = new MyObject<int>(20);
+  atomic_wp<MyObject<int>> wpobj = refobj;
+
+  // we can promote.
+  ASSERT_EQ(20, wpobj.load().promote()->get());
+
+  // same underlying object for sp and atomic_wp.
+  ASSERT_EQ(refobj.get(), wpobj.load().promote().get());
+
+  // behavior is consistent with same underlying object.
+  wpobj.load().promote()->set(10);
+  ASSERT_EQ(10, refobj->get());
+  refobj->set(5);
+  ASSERT_EQ(5, wpobj.load().promote()->get());
+
+  // we can clear our weak ptr.
+  wpobj = nullptr;
+  ASSERT_EQ(nullptr, wpobj.load().promote());
+
+  // didn't affect our original obj.
+  ASSERT_NE(nullptr, refobj.get());
+}
+
+TEST(media_synchronization_tests, atomic_sp) {
+  sp<MyObject<int>> refobj = new MyObject<int>(20);
+  atomic_sp<MyObject<int>> spobj = refobj;
+
+  // same underlying object for sp and atomic_sp.
+  ASSERT_EQ(refobj.get(), spobj.load().get());
+
+  // behavior is consistent with same underlying object.
+  ASSERT_EQ(20, spobj.load()->get());
+  spobj.load()->set(10);
+  ASSERT_EQ(10, refobj->get());
+  refobj->set(5);
+  ASSERT_EQ(5, spobj.load()->get());
+
+  // we can clear spobj.
+  spobj = nullptr;
+  ASSERT_EQ(nullptr, spobj.load().get());
+
+  // didn't affect our original obj.
+  ASSERT_NE(nullptr, refobj.get());
+}