Merge "SurfaceFlinger: VSyncPredictor should be robust with inconsistent vsyncs"

2 files changed, 20 insertions, 2 deletions

diff --git a/services/surfaceflinger/Scheduler/VSyncPredictor.cpp b/services/surfaceflinger/Scheduler/VSyncPredictor.cpp
index 61f3fbbdf1..708a5b87be 100644
--- a/services/surfaceflinger/Scheduler/VSyncPredictor.cpp
+++ b/services/surfaceflinger/Scheduler/VSyncPredictor.cpp
@@ -78,8 +78,12 @@ bool VSyncPredictor::addVsyncTimestamp(nsecs_t timestamp) {
 
     if (!validate(timestamp)) {
         // VSR could elect to ignore the incongruent timestamp or resetModel(). If ts is ignored,
-        // don't insert this ts into mTimestamps ringbuffer.
-        if (!mTimestamps.empty()) {
+        // don't insert this ts into mTimestamps ringbuffer. If we are still
+        // in the learning phase we should just clear all timestamps and start
+        // over.
+        if (mTimestamps.size() < kMinimumSamplesForPrediction) {
+            clearTimestamps();
+        } else if (!mTimestamps.empty()) {
             mKnownTimestamp =
                     std::max(timestamp, *std::max_element(mTimestamps.begin(), mTimestamps.end()));
         } else {
diff --git a/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp b/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp
index d4cd11dbe1..5e5d51c994 100644
--- a/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp
+++ b/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp
@@ -450,6 +450,20 @@ TEST_F(VSyncPredictorTest, aPhoneThatHasBeenAroundAWhileCanStillComputePeriod) {
     EXPECT_THAT(intercept, Eq(0));
 }
 
+TEST_F(VSyncPredictorTest, InconsistentVsyncValueIsFlushedEventually) {
+    EXPECT_TRUE(tracker.addVsyncTimestamp(600));
+    EXPECT_TRUE(tracker.needsMoreSamples());
+
+    EXPECT_FALSE(tracker.addVsyncTimestamp(mNow += mPeriod));
+
+    for (auto i = 0u; i < kMinimumSamplesForPrediction; i++) {
+        EXPECT_TRUE(tracker.needsMoreSamples());
+        EXPECT_TRUE(tracker.addVsyncTimestamp(mNow += mPeriod));
+    }
+
+    EXPECT_FALSE(tracker.needsMoreSamples());
+}
+
 } // namespace android::scheduler
 
 // TODO(b/129481165): remove the #pragma below and fix conversion issues