Fix VibratorCallbackScheduler destructor lock

The VibratorCallbackScheduler destructor joins on the scheduler
thread to wait for the main loop to finish, but the conditional variable
is waiting indefinitely without a predicate, which can cause it
sometimes to miss the notify call from the destructor and get stuck.

Adding a predicate condition fixes the VibratorCallbackSchedulerTest
flakiness for the timeout "No test results." failures.

Bug: 293603710
Bug: 293623689
Test: atest --rerun-until-failure 1000 VibratorCallbackSchedulerTest
Change-Id: Id9501c10fe5209003d9b74b0f39f2bcf87de05c2

2 files changed, 9 insertions, 7 deletions

diff --git a/services/vibratorservice/VibratorCallbackScheduler.cpp b/services/vibratorservice/VibratorCallbackScheduler.cpp
index 7eda9ef0c7..b2b1988d97 100644
--- a/services/vibratorservice/VibratorCallbackScheduler.cpp
+++ b/services/vibratorservice/VibratorCallbackScheduler.cpp
@@ -87,13 +87,13 @@ void CallbackScheduler::loop() {
             lock.lock();
         }
         if (mQueue.empty()) {
-            // Wait until a new callback is scheduled.
-            mCondition.wait(mMutex);
+            // Wait until a new callback is scheduled or destructor was called.
+            mCondition.wait(lock, [this] { return mFinished || !mQueue.empty(); });
         } else {
-            // Wait until next callback expires, or a new one is scheduled.
+            // Wait until next callback expires or a new one is scheduled.
             // Use the monotonic steady clock to wait for the measured delay interval via wait_for
             // instead of using a wall clock via wait_until.
-            mCondition.wait_for(mMutex, mQueue.top().getWaitForExpirationDuration());
+            mCondition.wait_for(lock, mQueue.top().getWaitForExpirationDuration());
         }
     }
 }
diff --git a/services/vibratorservice/test/test_utils.h b/services/vibratorservice/test/test_utils.h
index bf13aa7487..715c2215c4 100644
--- a/services/vibratorservice/test/test_utils.h
+++ b/services/vibratorservice/test/test_utils.h
@@ -90,13 +90,15 @@ public:
     TestCounter(int32_t init = 0) : mMutex(), mCondVar(), mCount(init) {}
 
     int32_t get() {
-        std::unique_lock<std::mutex> lock(mMutex);
+        std::lock_guard<std::mutex> lock(mMutex);
         return mCount;
     }
 
     void increment() {
-        std::unique_lock<std::mutex> lock(mMutex);
-        mCount += 1;
+        {
+            std::lock_guard<std::mutex> lock(mMutex);
+            mCount += 1;
+        }
         mCondVar.notify_all();
     }