Start combining threads in system process.

This introduces four generic thread that services can
use in the system process:

- Background: part of the framework for all processes, for
work that is purely background (no timing constraint).
- UI: for time-critical display of UI.
- Foreground: normal foreground work.
- IO: performing IO operations.

I went through and moved services into these threads in the
places I felt relatively comfortable about understanding what
they are doing.  There are still a bunch more we need to look
at -- lots of networking stuff left, 3 or so different native
daemon connectors which I didn't know how much would block,
audio stuff, etc.

Also updated Watchdog to be aware of and check these new
threads, with a new API for other threads to also participate
in this checking.

Change-Id: Ie2f11061cebde5f018d7383b3a910fbbd11d5e11

1 files changed, 71 insertions, 0 deletions

diff --git a/services/java/com/android/server/UiThread.java b/services/java/com/android/server/UiThread.java
new file mode 100644
index 0000000..60d73aa
--- /dev/null
+++ b/services/java/com/android/server/UiThread.java
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2013 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.server;
+
+import android.os.Handler;
+import android.os.HandlerThread;
+import android.os.StrictMode;
+import android.util.Slog;
+
+/**
+ * Shared singleton thread for showing UI.  This is a foreground thread, and in
+ * additional should not have operations that can take more than a few ms scheduled
+ * on it to avoid UI jank.
+ */
+public final class UiThread extends HandlerThread {
+    private static UiThread sInstance;
+    private static Handler sHandler;
+
+    private UiThread() {
+        super("android.ui", android.os.Process.THREAD_PRIORITY_FOREGROUND);
+    }
+
+    private static void ensureThreadLocked() {
+        if (sInstance == null) {
+            sInstance = new UiThread();
+            sInstance.start();
+            sHandler = new Handler(sInstance.getLooper());
+            sHandler.post(new Runnable() {
+                @Override
+                public void run() {
+                    //Looper.myLooper().setMessageLogging(new LogPrinter(
+                    //        Log.VERBOSE, "WindowManagerPolicy", Log.LOG_ID_SYSTEM));
+                    android.os.Process.setCanSelfBackground(false);
+
+                    // For debug builds, log event loop stalls to dropbox for analysis.
+                    if (StrictMode.conditionallyEnableDebugLogging()) {
+                        Slog.i("UiThread", "Enabled StrictMode logging for UI thread");
+                    }
+                }
+            });
+        }
+    }
+
+    public static UiThread get() {
+        synchronized (UiThread.class) {
+            ensureThreadLocked();
+            return sInstance;
+        }
+    }
+
+    public static Handler getHandler() {
+        synchronized (UiThread.class) {
+            ensureThreadLocked();
+            return sHandler;
+        }
+    }
+}