Migrate Tethering#dump to use runWithScissorsForDump
This change includes:
1. Refactor the logic in Tethering#dump into utils class.
2. Move the utils class to a common place which could be referenced
from other sub-modules.
3. Add @MonitorThreadLeak annotation to enforce
there is no thread leak problem.
Test: atest FrameworksNetTests NetworkStaticLibTests
Test: atest ConnectivityCoverageTests:com.android.networkstack.tethering.TetheringTest#testDumpTetheringLog
Test: adb shell dumpsys tethering (with hardcoded exception)
Fix: 312669345
Change-Id: Ia6fdfeeec2110afa0ec9e056e9db3843748845c3
diff --git a/staticlibs/Android.bp b/staticlibs/Android.bp
index 9f1debc..04eb15c 100644
--- a/staticlibs/Android.bp
+++ b/staticlibs/Android.bp
@@ -43,6 +43,7 @@
"device/com/android/net/module/util/SharedLog.java",
"device/com/android/net/module/util/SocketUtils.java",
"device/com/android/net/module/util/FeatureVersions.java",
+ "device/com/android/net/module/util/HandlerUtils.java",
// This library is used by system modules, for which the system health impact of Kotlin
// has not yet been evaluated. Annotations may need jarjar'ing.
// "src_devicecommon/**/*.kt",
diff --git a/staticlibs/device/com/android/net/module/util/HandlerUtils.java b/staticlibs/device/com/android/net/module/util/HandlerUtils.java
new file mode 100644
index 0000000..c620368
--- /dev/null
+++ b/staticlibs/device/com/android/net/module/util/HandlerUtils.java
@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.net.module.util;
+
+import android.annotation.NonNull;
+import android.os.Handler;
+import android.os.Looper;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+
+/**
+ * Helper class for Handler related utilities.
+ *
+ * @hide
+ */
+public class HandlerUtils {
+ /**
+ * Runs the specified task synchronously for dump method.
+ * <p>
+ * If the current thread is the same as the handler thread, then the runnable
+ * runs immediately without being enqueued. Otherwise, posts the runnable
+ * to the handler and waits for it to complete before returning.
+ * </p><p>
+ * This method is dangerous! Improper use can result in deadlocks.
+ * Never call this method while any locks are held or use it in a
+ * possibly re-entrant manner.
+ * </p><p>
+ * This method is made to let dump method access members on the handler thread to
+ * avoid concurrent access problems or races.
+ * </p><p>
+ * If timeout occurs then this method returns <code>false</code> but the runnable
+ * will remain posted on the handler and may already be in progress or
+ * complete at a later time.
+ * </p><p>
+ * When using this method, be sure to use {@link Looper#quitSafely} when
+ * quitting the looper. Otherwise {@link #runWithScissorsForDump} may hang indefinitely.
+ * (TODO: We should fix this by making MessageQueue aware of blocking runnables.)
+ * </p>
+ *
+ * @param h The target handler.
+ * @param r The Runnable that will be executed synchronously.
+ * @param timeout The timeout in milliseconds, or 0 to not wait at all.
+ *
+ * @return Returns true if the Runnable was successfully executed.
+ * Returns false on failure, usually because the
+ * looper processing the message queue is exiting.
+ *
+ * @hide
+ */
+ public static boolean runWithScissorsForDump(@NonNull Handler h, @NonNull Runnable r,
+ long timeout) {
+ if (r == null) {
+ throw new IllegalArgumentException("runnable must not be null");
+ }
+ if (timeout < 0) {
+ throw new IllegalArgumentException("timeout must be non-negative");
+ }
+ if (Looper.myLooper() == h.getLooper()) {
+ r.run();
+ return true;
+ }
+
+ final CountDownLatch latch = new CountDownLatch(1);
+
+ // Don't crash in the handler if something in the runnable throws an exception,
+ // but try to propagate the exception to the caller.
+ AtomicReference<RuntimeException> exceptionRef = new AtomicReference<>();
+ h.post(() -> {
+ try {
+ r.run();
+ } catch (RuntimeException e) {
+ exceptionRef.set(e);
+ }
+ latch.countDown();
+ });
+
+ try {
+ if (!latch.await(timeout, TimeUnit.MILLISECONDS)) {
+ return false;
+ }
+ } catch (InterruptedException e) {
+ exceptionRef.compareAndSet(null, new IllegalStateException("Thread interrupted", e));
+ }
+
+ final RuntimeException e = exceptionRef.get();
+ if (e != null) throw e;
+ return true;
+ }
+}
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/HandlerUtilsTest.kt b/staticlibs/tests/unit/src/com/android/net/module/util/HandlerUtilsTest.kt
new file mode 100644
index 0000000..f2c902f
--- /dev/null
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/HandlerUtilsTest.kt
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.net.module.util
+
+import android.os.HandlerThread
+import com.android.testutils.DevSdkIgnoreRunner
+import com.android.testutils.DevSdkIgnoreRunner.MonitorThreadLeak
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import org.junit.After
+import org.junit.Test
+import org.junit.runner.RunWith
+
+const val THREAD_BLOCK_TIMEOUT_MS = 1000L
+const val TEST_REPEAT_COUNT = 100
+
+@MonitorThreadLeak
+@RunWith(DevSdkIgnoreRunner::class)
+class HandlerUtilsTest {
+ val handlerThread = HandlerThread("HandlerUtilsTestHandlerThread").also {
+ it.start()
+ }
+ val handler = handlerThread.threadHandler
+
+ @Test
+ fun testRunWithScissors() {
+ // Repeat the test a fair amount of times to ensure that it does not pass by chance.
+ repeat(TEST_REPEAT_COUNT) {
+ var result = false
+ HandlerUtils.runWithScissorsForDump(handler, {
+ assertEquals(Thread.currentThread(), handlerThread)
+ result = true
+ }, THREAD_BLOCK_TIMEOUT_MS)
+ // Assert that the result is modified on the handler thread, but can also be seen from
+ // the current thread. The assertion should pass if the runWithScissors provides
+ // the guarantee where the assignment happens-before the assertion.
+ assertTrue(result)
+ }
+ }
+
+ @After
+ fun tearDown() {
+ handlerThread.quitSafely()
+ handlerThread.join()
+ }
+}