Watchdog: Improvement of debuggability

If the watchdog detects a problem the system server process
is killed, that is followed by a crash. Because the crash is
done after the system server process is killed, the crash
don't contain info about the system server.
This improvement will make sure that the system is crashed
before the system server process is killed.
Behavior is only changed for eng and userdebug builds.

Change-Id: I9f1c8fd8b03d0114032ed44fb582705ad0b49733

Author: rikard dahlman

services/java/com/android/server/Watchdog.java

@@ -25,6 +25,7 @@
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.os.Build;
 import android.os.Debug;
 import android.os.Handler;
 import android.os.Message;
@@ -38,6 +39,8 @@
 import android.util.Slog;
 
 import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Calendar;
 
@@ -428,11 +431,10 @@ public void run() {
             }
 
             // If we got here, that means that the system is most likely hung.
-            // First collect stack traces from all threads of the system process.
-            // Then kill this process so that the system will restart.
 
             final String name = (mCurrentMonitor != null) ?
                     mCurrentMonitor.getClass().getName() : "null";
+            Slog.w(TAG, "WATCHDOG PROBLEM IN SYSTEM SERVER: " + name);
             EventLog.writeEvent(EventLogTags.WATCHDOG, name);
 
             ArrayList<Integer> pids = new ArrayList<Integer>();
@@ -467,11 +469,15 @@ public void run() {
                 dropboxThread.join(2000);  // wait up to 2 seconds for it to return.
             } catch (InterruptedException ignored) {}
 
-            // Only kill the process if the debugger is not attached.
+            // Only kill/crash the process if the debugger is not attached.
             if (!Debug.isDebuggerConnected()) {
                 Slog.w(TAG, "*** WATCHDOG KILLING SYSTEM PROCESS: " + name);
-                Process.killProcess(Process.myPid());
-                System.exit(10);
+                if (!Build.TYPE.equals("user")) {
+                    forceCrashDump();
+                } else {
+                    Process.killProcess(Process.myPid());
+                    System.exit(10);
+                }
             } else {
                 Slog.w(TAG, "Debugger connected: Watchdog is *not* killing the system process");
             }
@@ -480,6 +486,50 @@ public void run() {
         }
     }
 
+    private void forceCrashDump() {
+        /* Sync file system to flash the data which is written just before the
+         * crash.
+         */
+        java.lang.Process p = null;
+        try {
+            p = Runtime.getRuntime().exec("sync");
+            if (p != null) {
+                // It is not necessary to check the exit code, here.
+                // 'sync' command always succeeds, and this function returns 0.
+                p.waitFor();
+            } else {
+                Slog.e(TAG, "Failed to execute 'sync' command. (no process handle)");
+            }
+        } catch (Exception e) {
+            // This code is an emergency path to crash MUT. The system already
+            // caused fatal error, and then calls this function to create a
+            // crash dump. This function must run the code below to force a
+            // crash, even if the sync command failed.
+            // Therefore, ignore all exceptions, here.
+            Slog.e(TAG, "Failed to execute 'sync' command prior to forcing crash: " + e);
+        } finally {
+            if (p != null) {
+                p.destroy();
+            }
+        }
+
+        FileWriter out = null;
+        try {
+            out = new FileWriter("/proc/sysrq-trigger");
+            out.write("c");
+        } catch (IOException e) {
+            Slog.e(TAG, "Failed to write to sysrq-trigger while triggering crash: " + e);
+        } finally {
+            if (out != null) {
+                try {
+                    out.close();
+                } catch (IOException e) {
+                    Slog.e(TAG, "Failed to close sysrq-trigger while triggering crash: " + e);
+                }
+            }
+        }
+    }
+
     private File dumpKernelStackTraces() {
         String tracesPath = SystemProperties.get("dalvik.vm.stack-trace-file", null);
         if (tracesPath == null || tracesPath.length() == 0) {