Automatically trace messages on shared loopers.

There are a handful of looper threads in the system_process that
are shared by dozens of different internal services.  To help track
down what these operations are, tag the processing of each message
with a string that tries describing where it originated from: the
class name of the Handler, and the message number or class name of the
Runnable.

Bug: 28046299
Change-Id: I409ec43fea8daaae4fd70df05d4fed929a7249ae

core/java/android/os/Handler.java

@@ -231,6 +231,18 @@ public class Handler {
         mAsynchronous = async;
     }
 
+    /** {@hide} */
+    public String getTraceName(Message message) {
+        final StringBuilder sb = new StringBuilder();
+        sb.append(getClass().getName()).append(": ");
+        if (message.callback != null) {
+            sb.append(message.callback.getClass().getName());
+        } else {
+            sb.append("#").append(message.what);
+        }
+        return sb.toString();
+    }
+
     /**
      * Returns a string representing the name of the specified message.
      * The default implementation will either return the class name of the
@@ -739,8 +751,8 @@ public class Handler {
         message.callback.run();
     }
 
-    final MessageQueue mQueue;
     final Looper mLooper;
+    final MessageQueue mQueue;
     final Callback mCallback;
     final boolean mAsynchronous;
     IMessenger mMessenger;

core/java/android/os/Looper.java

@@ -72,6 +72,7 @@ public final class Looper {
     final Thread mThread;
 
     private Printer mLogging;
+    private long mTraceTag;
 
      /** Initialize the current thread as a looper.
       * This gives you a chance to create handlers that then reference
@@ -139,13 +140,23 @@ public final class Looper {
             }
 
             // This must be in a local variable, in case a UI event sets the logger
-            Printer logging = me.mLogging;
+            final Printer logging = me.mLogging;
             if (logging != null) {
                 logging.println(">>>>> Dispatching to " + msg.target + " " +
                         msg.callback + ": " + msg.what);
             }
 
-            msg.target.dispatchMessage(msg);
+            final long traceTag = me.mTraceTag;
+            if (traceTag != 0) {
+                Trace.traceBegin(traceTag, msg.target.getTraceName(msg));
+            }
+            try {
+                msg.target.dispatchMessage(msg);
+            } finally {
+                if (traceTag != 0) {
+                    Trace.traceEnd(traceTag);
+                }
+            }
 
             if (logging != null) {
                 logging.println("<<<<< Finished to " + msg.target + " " + msg.callback);
@@ -208,6 +219,11 @@ public final class Looper {
         mLogging = printer;
     }
 
+    /** {@hide} */
+    public void setTraceTag(long traceTag) {
+        mTraceTag = traceTag;
+    }
+
     /**
      * Quits the looper.
      * <p>

core/java/com/android/internal/os/BackgroundThread.java

@@ -18,6 +18,7 @@ package com.android.internal.os;
 
 import android.os.Handler;
 import android.os.HandlerThread;
+import android.os.Trace;
 
 /**
  * Shared singleton background thread for each process.
@@ -34,6 +35,7 @@ public final class BackgroundThread extends HandlerThread {
         if (sInstance == null) {
             sInstance = new BackgroundThread();
             sInstance.start();
+            sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER);
             sHandler = new Handler(sInstance.getLooper());
         }
     }

services/core/java/com/android/server/DisplayThread.java

@@ -17,6 +17,7 @@
 package com.android.server;
 
 import android.os.Handler;
+import android.os.Trace;
 
 /**
  * Shared singleton foreground thread for the system.  This is a thread for
@@ -36,6 +37,7 @@ public final class DisplayThread extends ServiceThread {
         if (sInstance == null) {
             sInstance = new DisplayThread();
             sInstance.start();
+            sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER);
             sHandler = new Handler(sInstance.getLooper());
         }
     }

services/core/java/com/android/server/FgThread.java

@@ -17,6 +17,7 @@
 package com.android.server;
 
 import android.os.Handler;
+import android.os.Trace;
 
 /**
  * Shared singleton foreground thread for the system.  This is a thread for regular
@@ -38,6 +39,7 @@ public final class FgThread extends ServiceThread {
         if (sInstance == null) {
             sInstance = new FgThread();
             sInstance.start();
+            sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER);
             sHandler = new Handler(sInstance.getLooper());
         }
     }

services/core/java/com/android/server/IoThread.java

@@ -17,6 +17,7 @@
 package com.android.server;
 
 import android.os.Handler;
+import android.os.Trace;
 
 /**
  * Shared singleton I/O thread for the system.  This is a thread for non-background
@@ -35,6 +36,7 @@ public final class IoThread extends ServiceThread {
         if (sInstance == null) {
             sInstance = new IoThread();
             sInstance.start();
+            sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER);
             sHandler = new Handler(sInstance.getLooper());
         }
     }

services/core/java/com/android/server/UiThread.java

@@ -17,6 +17,7 @@
 package com.android.server;
 
 import android.os.Handler;
+import android.os.Trace;
 
 /**
  * Shared singleton thread for showing UI.  This is a foreground thread, and in
@@ -35,6 +36,7 @@ public final class UiThread extends ServiceThread {
         if (sInstance == null) {
             sInstance = new UiThread();
             sInstance.start();
+            sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER);
             sHandler = new Handler(sInstance.getLooper());
         }
     }