Fix flaky notifyPowerBoostNotifiesTouchEvent test

This patch fixes the flaky notifyPowerBoostNotifiesTouchEvent test by
forcing all operations to happen in a deterministic order, avoiding
races.

Bug: 332875603
Test: atest libsurfaceflinger_unittest:DisplayTransactionTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:0fd347a02ea101c3557083ccb935342e42bc977c)
Merged-In: I882c8cce57f071ec0c4c4e59f1b00dcca090c650
Change-Id: I882c8cce57f071ec0c4c4e59f1b00dcca090c650

2 files changed, 43 insertions, 11 deletions

diff --git a/services/surfaceflinger/tests/unittests/SurfaceFlinger_NotifyPowerBoostTest.cpp b/services/surfaceflinger/tests/unittests/SurfaceFlinger_NotifyPowerBoostTest.cpp
index 22b72f98e5..f2e2c8a76f 100644
--- a/services/surfaceflinger/tests/unittests/SurfaceFlinger_NotifyPowerBoostTest.cpp
+++ b/services/surfaceflinger/tests/unittests/SurfaceFlinger_NotifyPowerBoostTest.cpp
@@ -33,24 +33,45 @@ using aidl::android::hardware::power::Boost;
 TEST_F(DisplayTransactionTest, notifyPowerBoostNotifiesTouchEvent) {
     using namespace std::chrono_literals;
 
+    std::mutex timerMutex;
+    std::condition_variable cv;
+
     injectDefaultInternalDisplay([](FakeDisplayDeviceInjector&) {});
 
-    mFlinger.scheduler()->replaceTouchTimer(100);
-    std::this_thread::sleep_for(10ms);                  // wait for callback to be triggered
+    std::unique_lock lock(timerMutex);
+    bool didReset = false; // keeps track of what the most recent call was
+
+    auto waitForTimerReset = [&] { cv.wait_for(lock, 100ms, [&] { return didReset; }); };
+    auto waitForTimerExpired = [&] { cv.wait_for(lock, 100ms, [&] { return !didReset; }); };
+
+    // Add extra logic to unblock the test when the timer callbacks get called
+    mFlinger.scheduler()->replaceTouchTimer(10, [&](bool isReset) {
+        {
+            std::unique_lock lock(timerMutex); // guarantee we're waiting on the cv
+            didReset = isReset;
+        }
+        cv.notify_one();                   // wake the cv
+        std::unique_lock lock(timerMutex); // guarantee we finished the cv logic
+    });
+
+    waitForTimerReset();
     EXPECT_TRUE(mFlinger.scheduler()->isTouchActive()); // Starting timer activates touch
 
-    std::this_thread::sleep_for(110ms); // wait for reset touch timer to expire and trigger callback
-    EXPECT_FALSE(mFlinger.scheduler()->isTouchActive());
+    waitForTimerExpired();
+    EXPECT_FALSE(mFlinger.scheduler()->isTouchActive()); // Stopping timer deactivates touch
 
     EXPECT_EQ(NO_ERROR, mFlinger.notifyPowerBoost(static_cast<int32_t>(Boost::CAMERA_SHOT)));
-    std::this_thread::sleep_for(10ms); // wait for callback to maybe be triggered
-    EXPECT_FALSE(mFlinger.scheduler()->isTouchActive());
 
-    std::this_thread::sleep_for(110ms); // wait for reset touch timer to expire and trigger callback
+    EXPECT_FALSE(mFlinger.scheduler()->isTouchActive());
+    // Wait for the timer to start just in case
+    waitForTimerReset();
+    EXPECT_FALSE(mFlinger.scheduler()->isTouchActive());
+    // Wait for the timer to stop, again just in case
+    waitForTimerExpired();
     EXPECT_FALSE(mFlinger.scheduler()->isTouchActive());
 
     EXPECT_EQ(NO_ERROR, mFlinger.notifyPowerBoost(static_cast<int32_t>(Boost::INTERACTION)));
-    std::this_thread::sleep_for(10ms); // wait for callback to be triggered.
+    waitForTimerReset();
     EXPECT_TRUE(mFlinger.scheduler()->isTouchActive());
 }
 
diff --git a/services/surfaceflinger/tests/unittests/TestableScheduler.h b/services/surfaceflinger/tests/unittests/TestableScheduler.h
index 2a1b88e6fa..c0255d3e98 100644
--- a/services/surfaceflinger/tests/unittests/TestableScheduler.h
+++ b/services/surfaceflinger/tests/unittests/TestableScheduler.h
@@ -136,14 +136,25 @@ public:
         return mLayerHistory.mActiveLayerInfos.size();
     }
 
-    void replaceTouchTimer(int64_t millis) {
+    void replaceTouchTimer(int64_t millis,
+                           std::function<void(bool isReset)>&& testCallback = nullptr) {
         if (mTouchTimer) {
             mTouchTimer.reset();
         }
         mTouchTimer.emplace(
                 "Testable Touch timer", std::chrono::milliseconds(millis),
-                [this] { touchTimerCallback(TimerState::Reset); },
-                [this] { touchTimerCallback(TimerState::Expired); });
+                [this, testCallback] {
+                    touchTimerCallback(TimerState::Reset);
+                    if (testCallback != nullptr) {
+                        testCallback(true);
+                    }
+                },
+                [this, testCallback] {
+                    touchTimerCallback(TimerState::Expired);
+                    if (testCallback != nullptr) {
+                        testCallback(false);
+                    }
+                });
         mTouchTimer->start();
     }