From 9211b13c3268035b0da0c51ed2d6d5a578d45ff3 Mon Sep 17 00:00:00 2001
From: rikard dahlman <rikard.dahlman@sonymobile.com>
Date: Tue, 28 Aug 2012 16:12:38 +0200
Subject: [PATCH] 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
---
 .../java/com/android/server/Watchdog.java     | 60 +++++++++++++++++--
 1 file changed, 55 insertions(+), 5 deletions(-)

diff --git a/services/java/com/android/server/Watchdog.java b/services/java/com/android/server/Watchdog.java
index c2393823bf719..c14e2f6349452 100644
--- a/services/java/com/android/server/Watchdog.java
+++ b/services/java/com/android/server/Watchdog.java
@@ -25,6 +25,7 @@ import android.content.ContentResolver;
 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.Log;
 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 class Watchdog extends Thread {
             }
 
             // 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 class Watchdog extends Thread {
                 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 class Watchdog extends Thread {
         }
     }
 
+    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) {