SF: add a backdoor to introduce a janky frame to HWC

Bug: 346503493
Test: adb shell service call SurfaceFlinger 1046 i32 3Test: adb root && adb shell service call SurfaceFlinger 1046 i32 3
Flag: EXEMPT bugfix
Change-Id: Ic4a837ef06aca40a24db9c1121e19e3e1a1e0d80

Author: adyabr

services/surfaceflinger/CompositionEngine/src/Output.cpp

@@ -895,6 +895,12 @@ void Output::writeCompositionState(const compositionengine::CompositionRefreshAr
                                          })) {
         editState().earliestPresentTime = frameTargetPtrOpt->get()->earliestPresentTime();
         editState().expectedPresentTime = frameTargetPtrOpt->get()->expectedPresentTime().ns();
+        const auto debugPresentDelay = frameTargetPtrOpt->get()->debugPresentDelay();
+        if (debugPresentDelay) {
+            SFTRACE_FORMAT_INSTANT("DEBUG delaying presentation by %.2fms",
+                                   debugPresentDelay->ns() / 1e6f);
+            editState().expectedPresentTime += debugPresentDelay->ns();
+        }
     }
     editState().frameInterval = refreshArgs.frameInterval;
     editState().powerCallback = refreshArgs.powerCallback;

services/surfaceflinger/Scheduler/Scheduler.cpp

@@ -203,12 +203,16 @@ void Scheduler::run() {
 
 void Scheduler::onFrameSignal(ICompositor& compositor, VsyncId vsyncId,
                               TimePoint expectedVsyncTime) {
+    const auto debugPresentDelay = mDebugPresentDelay.load();
+    mDebugPresentDelay.store(std::nullopt);
+
     const FrameTargeter::BeginFrameArgs beginFrameArgs =
             {.frameBeginTime = SchedulerClock::now(),
              .vsyncId = vsyncId,
              .expectedVsyncTime = expectedVsyncTime,
              .sfWorkDuration = mVsyncModulator->getVsyncConfig().sfWorkDuration,
-             .hwcMinWorkDuration = mVsyncConfiguration->getCurrentConfigs().hwcMinWorkDuration};
+             .hwcMinWorkDuration = mVsyncConfiguration->getCurrentConfigs().hwcMinWorkDuration,
+             .debugPresentTimeDelay = debugPresentDelay};
 
     ftl::NonNull<const Display*> pacesetterPtr = pacesetterPtrLocked();
     pacesetterPtr->targeterPtr->beginFrame(beginFrameArgs, *pacesetterPtr->schedulePtr);

services/surfaceflinger/Scheduler/Scheduler.h

@@ -337,6 +337,8 @@ class Scheduler : public IEventThreadCallback, android::impl::MessageQueue {
     // recovery should begin.
     void addBufferStuffedUids(BufferStuffingMap bufferStuffedUids);
 
+    void setDebugPresentDelay(TimePoint delay) { mDebugPresentDelay = delay; }
+
 private:
     friend class TestableScheduler;
 
@@ -602,6 +604,8 @@ class Scheduler : public IEventThreadCallback, android::impl::MessageQueue {
 
     FrameRateOverrideMappings mFrameRateOverrideMappings;
     SmallAreaDetectionAllowMappings mSmallAreaDetectionAllowMappings;
+
+    std::atomic<std::optional<TimePoint>> mDebugPresentDelay;
 };
 
 } // namespace scheduler

services/surfaceflinger/Scheduler/include/scheduler/FrameTargeter.h

@@ -53,6 +53,8 @@ class FrameTarget {
 
     TimePoint expectedPresentTime() const { return mExpectedPresentTime; }
 
+    std::optional<TimePoint> debugPresentDelay() const { return mDebugPresentTimeDelay; }
+
     std::optional<TimePoint> earliestPresentTime() const { return mEarliestPresentTime; }
 
     // Equivalent to `expectedSignaledPresentFence` unless running N VSYNCs ahead.
@@ -84,6 +86,7 @@ class FrameTarget {
     TimePoint mFrameBeginTime;
     TimePoint mExpectedPresentTime;
     std::optional<TimePoint> mEarliestPresentTime;
+    std::optional<TimePoint> mDebugPresentTimeDelay;
 
     TracedOrdinal<bool> mFramePending;
     TracedOrdinal<bool> mFrameMissed;
@@ -135,6 +138,7 @@ class FrameTargeter final : private FrameTarget {
         TimePoint expectedVsyncTime;
         Duration sfWorkDuration;
         Duration hwcMinWorkDuration;
+        std::optional<TimePoint> debugPresentTimeDelay; // used to introduce jank for testing
     };
 
     void beginFrame(const BeginFrameArgs&, const IVsyncSource&);

services/surfaceflinger/Scheduler/src/FrameTargeter.cpp

@@ -86,6 +86,7 @@ void FrameTargeter::beginFrame(const BeginFrameArgs& args, const IVsyncSource& v
                                IsFencePendingFuncPtr isFencePendingFuncPtr) {
     mVsyncId = args.vsyncId;
     mFrameBeginTime = args.frameBeginTime;
+    mDebugPresentTimeDelay = args.debugPresentTimeDelay;
 
     // The `expectedVsyncTime`, which was predicted when this frame was scheduled, is normally in
     // the future relative to `frameBeginTime`, but may not be for delayed frames. Adjust

services/surfaceflinger/SurfaceFlinger.cpp

@@ -6263,7 +6263,7 @@ status_t SurfaceFlinger::CheckTransactCodeCredentials(uint32_t code) {
     }
     // Numbers from 1000 to 1045 are currently used for backdoors. The code
     // in onTransact verifies that the user is root, and has access to use SF.
-    if (code >= 1000 && code <= 1045) {
+    if (code >= 1000 && code <= 1046) {
         ALOGV("Accessing SurfaceFlinger through backdoor code: %u", code);
         return OK;
     }
@@ -6796,6 +6796,15 @@ status_t SurfaceFlinger::onTransact(uint32_t code, const Parcel& data, Parcel* r
                 }
                 return err;
             }
+            // Introduce jank to HWC
+            case 1046: {
+                int32_t jankDelayMs = 0;
+                if (data.readInt32(&jankDelayMs) != NO_ERROR) {
+                    return BAD_VALUE;
+                }
+                mScheduler->setDebugPresentDelay(TimePoint::fromNs(ms2ns(jankDelayMs)));
+                return NO_ERROR;
+            }
         }
     }
     return err;