InputTracingTest: Fix test flakiness

There was a bug in the logic for tracking when the tracing thread is
idle. The thread can only be idle when the queue is empty, so prevent
it from being marked as idle when there are still events left to be
processed.

Also, a waitForTracerIdle() was missing in the TraceWindowDispatch test.

Bug: 333544493
Test: InputTracingTest passes 10000 times
Change-Id: I90feaeefc80d1a0e43732ee7e75d4074a9634bd7

2 files changed, 8 insertions, 3 deletions

diff --git a/services/inputflinger/dispatcher/trace/ThreadedBackend.cpp b/services/inputflinger/dispatcher/trace/ThreadedBackend.cpp
index c0a98f5e5d..3c3c15a64c 100644
--- a/services/inputflinger/dispatcher/trace/ThreadedBackend.cpp
+++ b/services/inputflinger/dispatcher/trace/ThreadedBackend.cpp
@@ -57,6 +57,7 @@ void ThreadedBackend<Backend>::traceMotionEvent(const TracedMotionEvent& event,
                                                 const TracedEventMetadata& metadata) {
     std::scoped_lock lock(mLock);
     mQueue.emplace_back(event, metadata);
+    setIdleStatus(false);
     mThreadWakeCondition.notify_all();
 }
 
@@ -65,6 +66,7 @@ void ThreadedBackend<Backend>::traceKeyEvent(const TracedKeyEvent& event,
                                              const TracedEventMetadata& metadata) {
     std::scoped_lock lock(mLock);
     mQueue.emplace_back(event, metadata);
+    setIdleStatus(false);
     mThreadWakeCondition.notify_all();
 }
 
@@ -73,6 +75,7 @@ void ThreadedBackend<Backend>::traceWindowDispatch(const WindowDispatchArgs& dis
                                                    const TracedEventMetadata& metadata) {
     std::scoped_lock lock(mLock);
     mQueue.emplace_back(dispatchArgs, metadata);
+    setIdleStatus(false);
     mThreadWakeCondition.notify_all();
 }
 
@@ -84,7 +87,9 @@ void ThreadedBackend<Backend>::threadLoop() {
         std::unique_lock lock(mLock);
         base::ScopedLockAssertion assumeLocked(mLock);
 
-        setIdleStatus(true);
+        if (mQueue.empty()) {
+            setIdleStatus(true);
+        }
 
         // Wait until we need to process more events or exit.
         mThreadWakeCondition.wait(lock,
@@ -94,8 +99,6 @@ void ThreadedBackend<Backend>::threadLoop() {
             return;
         }
 
-        setIdleStatus(false);
-
         mQueue.swap(entries);
     } // release lock
 
diff --git a/services/inputflinger/tests/InputTracingTest.cpp b/services/inputflinger/tests/InputTracingTest.cpp
index fe4d6d9a8f..23fa045f86 100644
--- a/services/inputflinger/tests/InputTracingTest.cpp
+++ b/services/inputflinger/tests/InputTracingTest.cpp
@@ -626,6 +626,8 @@ TEST_F(InputTracingTest, TraceWindowDispatch) {
     consumed = window->consumeMotionEvent(WithMotionAction(ACTION_CANCEL));
     s.expectMotionTraced(Level::NONE, *consumed);
     s.expectDispatchTraced(Level::REDACTED, {*consumed, window});
+
+    waitForTracerIdle();
 }
 
 TEST_F(InputTracingTest, SimultaneousTracingSessions) {