Use ThreadPrioritySetter to set thread priority

Use ThreadPrioritySetter registered in Android runtime to set thread
priority.

Bug: 139521784
Test: CtsLibcoreTestCases, device boot to home, thread priority set
      as expected.
Change-Id: I71c5052beb171f966eba97401159306b87e397b7

2 files changed, 60 insertions, 0 deletions

diff --git a/dalvik/src/main/java/dalvik/system/RuntimeHooks.java b/dalvik/src/main/java/dalvik/system/RuntimeHooks.java
index 320ea28253..f1af86790c 100644
--- a/dalvik/src/main/java/dalvik/system/RuntimeHooks.java
+++ b/dalvik/src/main/java/dalvik/system/RuntimeHooks.java
@@ -16,10 +16,15 @@
 
 package dalvik.system;
 
+import dalvik.system.ThreadPrioritySetter;
+
 import java.util.Objects;
 import java.util.TimeZone;
 import java.util.function.Supplier;
 
+import libcore.util.NonNull;
+import libcore.util.Nullable;
+
 /**
  * Provides lifecycle methods and other hooks for an Android runtime "container" to call into the
  * runtime and core libraries during initialization. For example, from
@@ -35,6 +40,10 @@ public final class RuntimeHooks {
 
     private static Supplier<String> zoneIdSupplier;
 
+    // BEGIN Android-added: Customize behavior of Thread.setPriority(). http://b/139521784
+    private static volatile ThreadPrioritySetter threadPrioritySetter;
+    // END Android-added: Customize behavior of Thread.setPriority(). http://b/139521784
+
     private RuntimeHooks() {
         // No need to construct an instance. All methods are static.
     }
@@ -77,4 +86,27 @@ public final class RuntimeHooks {
             Thread.UncaughtExceptionHandler uncaughtExceptionHandler) {
         Thread.setUncaughtExceptionPreHandler(uncaughtExceptionHandler);
     }
+
+    // BEGIN Android-added: Customize behavior of Thread.setPriority(). http://b/139521784
+    /**
+     * Sets a {@link ThreadPrioritySetter} that will be invoked instead of
+     * the default implementation during {@link Thread.setPriority(int)}.
+     * @hide
+     */
+    @libcore.api.CorePlatformApi
+    public static void setThreadPrioritySetter(@NonNull ThreadPrioritySetter threadPrioritySetter) {
+        RuntimeHooks.threadPrioritySetter = Objects.requireNonNull(threadPrioritySetter);
+    }
+
+    /**
+     * Returns the last {@code ThreadPrioritySetter} that has been
+     * {@code #setThreadPrioritySetter(ThreadPrioritySetter) set}, or
+     * null if the setter has not yet been called.
+     * @hide
+     */
+    @libcore.api.CorePlatformApi
+    public static @Nullable ThreadPrioritySetter getThreadPrioritySetter() {
+        return threadPrioritySetter;
+    }
+    // END Android-added: Customize behavior of Thread.setPriority(). http://b/139521784
 }
diff --git a/dalvik/src/main/java/dalvik/system/ThreadPrioritySetter.java b/dalvik/src/main/java/dalvik/system/ThreadPrioritySetter.java
new file mode 100644
index 0000000000..f1d5e7211a
--- /dev/null
+++ b/dalvik/src/main/java/dalvik/system/ThreadPrioritySetter.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2019 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 dalvik.system;
+
+/**
+ * Interface for hooking to thread priority runtime setting
+ * @hide
+ */
+@libcore.api.CorePlatformApi
+@FunctionalInterface
+public interface ThreadPrioritySetter {
+    @libcore.api.CorePlatformApi
+    void setPriority(int priority);
+}