commit fc690e2a2d1d3cf08d71a02c4ecd14665c0f2039
author Cheng Shi <shicheng@xiaomi.corp-partner.google.com> Fri Oct 22 08:53:11 2021 +0000
committer Cheng Shi <shicheng@xiaomi.corp-partner.google.com> Tue Nov 02 06:07:23 2021 +0000
tree 5f544acfda56e768309fb124b5c73dbc0825084d
parent 5f852b9c9bca236b01f8d59853d29fb6b6ee89b6

Dispatch vsync when receiving vsync timeout to handle vsync loss.

Currently we do not have a mechanism to guarantee the arrival of the vsync signal. The vsync signal loss may occur when the renderNodeAnimator is running. The render thread took a long time to perform drawing without time to read the pipe, and the pipe was filled with other signals like configChanged, causing surfaceflinger to miss a vsync signal.
If a vsync lost, causing DisplayEventDispatcher::mWaitingForVsync to be true, resulting in DisplayEventDispatcher::scheduleVsync can no longer schedule another vsync. So we need to dispatch vsync when receiving vsync timeout.

Bug: 204097701
Test: Manual
Change-Id: Ibfa7a301ea17ebd58cae6b790a61d66c3d2e43fd
Signed-off-by: shicheng <shicheng@xiaomi.com>

libs/gui/DisplayEventDispatcher.cpp

diff --git a/libs/gui/DisplayEventDispatcher.cpp b/libs/gui/DisplayEventDispatcher.cpp
index e1b1efc..46800f2 100644
--- a/libs/gui/DisplayEventDispatcher.cpp
+++ b/libs/gui/DisplayEventDispatcher.cpp
@@ -33,10 +33,13 @@
 // using just a few large reads.
 static const size_t EVENT_BUFFER_SIZE = 100;
 
+static constexpr nsecs_t WAITING_FOR_VSYNC_TIMEOUT = ms2ns(300);
+
 DisplayEventDispatcher::DisplayEventDispatcher(
         const sp<Looper>& looper, ISurfaceComposer::VsyncSource vsyncSource,
         ISurfaceComposer::EventRegistrationFlags eventRegistration)
-      : mLooper(looper), mReceiver(vsyncSource, eventRegistration), mWaitingForVsync(false) {
+      : mLooper(looper), mReceiver(vsyncSource, eventRegistration), mWaitingForVsync(false),
+        mLastVsyncCount(0), mLastScheduleVsyncTime(0) {
     ALOGV("dispatcher %p ~ Initializing display event dispatcher.", this);
 }
 
@@ -86,6 +89,7 @@
         }
 
         mWaitingForVsync = true;
+        mLastScheduleVsyncTime = systemTime(SYSTEM_TIME_MONOTONIC);
     }
     return OK;
 }
@@ -124,9 +128,21 @@
               this, ns2ms(vsyncTimestamp), to_string(vsyncDisplayId).c_str(), vsyncCount,
               vsyncEventData.id);
         mWaitingForVsync = false;
+        mLastVsyncCount = vsyncCount;
         dispatchVsync(vsyncTimestamp, vsyncDisplayId, vsyncCount, vsyncEventData);
     }
 
+    if (mWaitingForVsync) {
+        const nsecs_t currentTime = systemTime(SYSTEM_TIME_MONOTONIC);
+        const nsecs_t vsyncScheduleDelay = currentTime - mLastScheduleVsyncTime;
+        if (vsyncScheduleDelay > WAITING_FOR_VSYNC_TIMEOUT) {
+            ALOGW("Vsync time out! vsyncScheduleDelay=%" PRId64 "ms", ns2ms(vsyncScheduleDelay));
+            mWaitingForVsync = false;
+            dispatchVsync(currentTime, vsyncDisplayId /* displayId is not used */,
+                          ++mLastVsyncCount, vsyncEventData /* empty data */);
+        }
+    }
+
     return 1; // keep the callback
 }