Do not crash when server channel has closed

If the publisher has been destroyed (or, equivalently, if the server
channel was closed), the consumer should not crash. Instead, we should
allow consumer to exit gracefully.

In this CL, we specifically check for DEAD_OBJECT and drain the queue,
printing all of the events that will never be delivered to the publisher
for useful debugging purposes.

Bug: 305165753
Test: TEST=libinput_tests; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST
Flag: EXEMPT bugfix

Change-Id: I00973ebb87e0f59bfd3c0f58edf7355b28988c15

Author: vishniakou

libs/input/InputConsumerNoResampling.cpp

@@ -169,6 +169,12 @@ InputMessage createTimelineMessage(int32_t inputEventId, nsecs_t gpuCompletedTim
     msg.body.timeline.graphicsTimeline[GraphicsTimeline::PRESENT_TIME] = presentTime;
     return msg;
 }
+
+std::ostream& operator<<(std::ostream& out, const InputMessage& msg) {
+    out << ftl::enum_string(msg.header.type);
+    return out;
+}
+
 } // namespace
 
 // --- InputConsumerNoResampling ---
@@ -272,6 +278,15 @@ void InputConsumerNoResampling::processOutboundEvents() {
             return; // try again later
         }
 
+        if (result == DEAD_OBJECT) {
+            // If there's no one to receive events in the channel, there's no point in sending them.
+            // Drop all outbound events.
+            LOG(INFO) << "Channel " << mChannel->getName() << " died. Dropping outbound event "
+                      << outboundMsg;
+            mOutboundQueue.pop();
+            setFdEvents(0);
+            continue;
+        }
         // Some other error. Give up
         LOG(FATAL) << "Failed to send outbound event on channel '" << mChannel->getName()
                    << "'.  status=" << statusToString(result) << "(" << result << ")";

libs/input/tests/InputPublisherAndConsumerNoResampling_test.cpp

@@ -319,6 +319,8 @@ class InputPublisherAndConsumerNoResamplingTest : public testing::Test,
 
 protected:
     // Interaction with the looper thread
+    void blockLooper();
+    void unblockLooper();
     enum class LooperMessage : int {
         CALL_PROBABLY_HAS_INPUT,
         CREATE_CONSUMER,
@@ -389,6 +391,26 @@ class InputPublisherAndConsumerNoResamplingTest : public testing::Test,
     };
 };
 
+void InputPublisherAndConsumerNoResamplingTest::blockLooper() {
+    {
+        std::scoped_lock l(mLock);
+        mLooperMayProceed = false;
+    }
+    sendMessage(LooperMessage::BLOCK_LOOPER);
+    {
+        std::unique_lock l(mLock);
+        mNotifyLooperWaiting.wait(l, [this] { return mLooperIsBlocked; });
+    }
+}
+
+void InputPublisherAndConsumerNoResamplingTest::unblockLooper() {
+    {
+        std::scoped_lock l(mLock);
+        mLooperMayProceed = true;
+    }
+    mNotifyLooperMayProceed.notify_all();
+}
+
 void InputPublisherAndConsumerNoResamplingTest::sendMessage(LooperMessage message) {
     Message msg{ftl::to_underlying(message)};
     mLooper->sendMessage(mMessageHandler, msg);
@@ -600,15 +622,7 @@ void InputPublisherAndConsumerNoResamplingTest::publishAndConsumeSinglePointerMu
     std::queue<uint32_t> publishedSequenceNumbers;
 
     // Block Looper to increase the chance of batching events
-    {
-        std::scoped_lock l(mLock);
-        mLooperMayProceed = false;
-    }
-    sendMessage(LooperMessage::BLOCK_LOOPER);
-    {
-        std::unique_lock l(mLock);
-        mNotifyLooperWaiting.wait(l, [this] { return mLooperIsBlocked; });
-    }
+    blockLooper();
 
     uint32_t firstSampleId;
     for (size_t i = 0; i < nSamples; ++i) {
@@ -629,12 +643,7 @@ void InputPublisherAndConsumerNoResamplingTest::publishAndConsumeSinglePointerMu
 
     std::vector<MotionEvent> singleSampledMotionEvents;
 
-    // Unblock Looper
-    {
-        std::scoped_lock l(mLock);
-        mLooperMayProceed = true;
-    }
-    mNotifyLooperMayProceed.notify_all();
+    unblockLooper();
 
     // We have no control over the socket behavior, so the consumer can receive
     // the motion as a batched event, or as a sequence of multiple single-sample MotionEvents (or a
@@ -809,6 +818,15 @@ void InputPublisherAndConsumerNoResamplingTest::publishAndConsumeTouchModeEvent(
     verifyFinishedSignal(*mPublisher, seq, publishTime);
 }
 
+/**
+ * If the publisher has died, consumer should not crash when trying to send an outgoing message.
+ */
+TEST_F(InputPublisherAndConsumerNoResamplingTest, ConsumerWritesAfterPublisherDies) {
+    mPublisher.reset(); // The publisher has died
+    mReportTimelineArgs.emplace(/*inputEventId=*/10, /*gpuCompletedTime=*/20, /*presentTime=*/30);
+    sendMessage(LooperMessage::CALL_REPORT_TIMELINE);
+}
+
 TEST_F(InputPublisherAndConsumerNoResamplingTest, SendTimeline) {
     const int32_t inputEventId = 20;
     const nsecs_t gpuCompletedTime = 30;