SWT 重启案例分析（一）

 

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本篇文章主要介绍 Android 开发中的部分知识点，通过阅读本篇文章，您将收获以下内容:

1.MTK AEE Log分析工具
2.AEE Log分析流程
3.system_server 卡死案例分析及解决

本文主要针对 Exception Type: system_server_watchdog , system_server卡死找出的分析以及解决方案。

一、MTK AEE Log分析工具

MTK AEE Log 获取方式：

关注微信公众号： 程序员Android
回复 aee 即可获取解析重启db log的工具。

二、AEE Log分析流程

1. 使用AEE 工具解析 dbg 文件。

使用解析db.fatal.02.SWT.dbg

AEE Log 解析出来的文件

2.分析解析出来的exp_main等文件

exp_main 文件会记录发生重启时候的 log 打印信息。

部分重启异常 Log信息如下：

$** *** *** *** *** *** *** *** Fatal *** *** *** *** *** *** *** **$
Build Info: 'alps-mp-o1.mp7:alps-mp-o1.mp7:mt6765:S01,ACE/AS0618/AS0618:8.1.0/O11019/1548123508:user/release-keys'
Flavor Info: 'None'
Exception Log Time:[Thu Mar 14 14:00:03 CST 2019] [38684.729626]

Exception Class: SWT
Exception Type: system_server_watchdog

Current Executing Process: 
system_server


Trigger time:[2019-03-14 14:00:03.711844] pid:1029

Backtrace: 
Process: system_server
Subject: Blocked in handler on ActivityManager (ActivityManager)
Build: ACE/AS0618/AS0618:8.1.0/O11019/1548123508:user/release-keys

**exp_main 文件解析 **
从开头的Log总体信息概览，我们可以看到 发生重启的时间、类型，触发重启的进程以及PID、系统Blocked 的地方。

结合exp_main以及 trace分析重启 Log
Log分析如下：

// 1.重启触发时间，以及PID 
Trigger time:[2019-03-14 14:00:03.711844] pid:1029
// 2.Blocked 的进程
Backtrace: 
Process: system_server
Subject: Blocked in handler on ActivityManager (ActivityManager)
// 3.根据PID 查看Trace信息
----- pid 1029 at 2019-03-14 13:59:58 -----
Cmd line: system_server

... ...
// 4.根据Backtrace 查看Blocked的信息
"ActivityManager" prio=5 tid=11 Blocked

... ...
// 5.tid=11 等待 tid=106的线程释放资源锁
  - waiting to lock <0x090691f3> (a android.util.ArrayMap) held by thread 106  
... ...

// 6.查看tid = 106 持锁情况
"backup" prio=5 tid=106 Waiting
... ... 

  at java.lang.Object.wait(Native method)
  - waiting on <0x06a44c62> (a com.android.server.am.ContentProviderRecord)
// 7.死锁卡住的地方
  at com.android.server.am.ActivityManagerService.getContentProviderImpl(ActivityManagerService.java:12127)
  - locked <0x06a44c62> (a com.android.server.am.ContentProviderRecord)
  
  ...  ...

"Binder:1029_8" prio=5 tid=107 Blocked
// 8.log中  tid=107 被 106 Blocked 进一步问题的加重
  at com.android.server.notification.RankingHelper.getRecord(RankingHelper.java:258)
  - waiting to lock <0x090691f3> (a android.util.ArrayMap) held by thread 106
  
$** *** *** *** *** *** *** *** Fatal *** *** *** *** *** *** *** **$

Log 分析大致过程截图

完整 log 请在公众号上获取

3.system_server 卡死案例分析及解决

通过 Log 找到卡死原因后，解决此问题。
需要修改ActivityManagerService类。

代码路径如下：alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

解决思路：
避免 provider 长时间持锁触发MTK 60s 的SWT 重启机制，设置超时时间，超过时间就要释放资源锁，避免发生此问题。

diff 修改方案如下：

--- a/[alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=d5e2e1411f3698a829e997d402c7482ec277fa8c;hb=d5e2e1411f3698a829e997d402c7482ec277fa8c)

+++ b/[alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=03208f78a2bf3167b4f0790019326e3939cc5444;hb=03208f78a2bf3167b4f0790019326e3939cc5444)

@@ [-545,7](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=d5e2e1411f3698a829e997d402c7482ec277fa8c;hb=d5e2e1411f3698a829e997d402c7482ec277fa8c#l545) [+545,9](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=03208f78a2bf3167b4f0790019326e3939cc5444;hb=03208f78a2bf3167b4f0790019326e3939cc5444#l545) @@ public class ActivityManagerService extends IActivityManager.Stub

     // How long we wait for an attached process to publish its content providers

     // before we decide it must be hung.

     static final int CONTENT_PROVIDER_PUBLISH_TIMEOUT = 10*1000;

-

+    // How long we wait for provider to be notify before we decide it may be hung.

+    static final int CONTENT_PROVIDER_WAIT_TIMEOUT = 20*1000;

+       

     // How long we wait for a launched process to attach to the activity manager

     // before we decide it's never going to come up for real, when the process was

     // started with a wrapper for instrumentation (such as Valgrind) because it

@@ [-1745,6](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=d5e2e1411f3698a829e997d402c7482ec277fa8c;hb=d5e2e1411f3698a829e997d402c7482ec277fa8c#l1745) [+1747,7](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=03208f78a2bf3167b4f0790019326e3939cc5444;hb=03208f78a2bf3167b4f0790019326e3939cc5444#l1747) @@ public class ActivityManagerService extends IActivityManager.Stub

     static final int PUSH_TEMP_WHITELIST_UI_MSG = 68;

     static final int SERVICE_FOREGROUND_CRASH_MSG = 69;

     static final int DISPATCH_OOM_ADJ_OBSERVER_MSG = 70;

+        static final int CONTENT_PROVIDER_WAIT_TIMEOUT_MSG = 71;

     static final int START_USER_SWITCH_FG_MSG = 712;

     static final int NOTIFY_VR_KEYGUARD_MSG = 74;

@@ [-2108,6](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=d5e2e1411f3698a829e997d402c7482ec277fa8c;hb=d5e2e1411f3698a829e997d402c7482ec277fa8c#l2108) [+2111,12](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=03208f78a2bf3167b4f0790019326e3939cc5444;hb=03208f78a2bf3167b4f0790019326e3939cc5444#l2111) @@ public class ActivityManagerService extends IActivityManager.Stub

                 synchronized (ActivityManagerService.this) {

                     mActivityStarter.doPendingActivityLaunchesLocked(true);

                 }

+            } break;

+                       case CONTENT_PROVIDER_WAIT_TIMEOUT_MSG: {

+                ContentProviderRecord cpr = (ContentProviderRecord)msg.obj;

+                synchronized (ActivityManagerService.this) {

+                    processContentProviderWaitTimedOutLocked(cpr);

+                }

             } break;

             case KILL_APPLICATION_MSG: {

                 synchronized (ActivityManagerService.this) {

@@ [-7029,7](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=d5e2e1411f3698a829e997d402c7482ec277fa8c;hb=d5e2e1411f3698a829e997d402c7482ec277fa8c#l7029) [+7038,31](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=03208f78a2bf3167b4f0790019326e3939cc5444;hb=03208f78a2bf3167b4f0790019326e3939cc5444#l7038) @@ public class ActivityManagerService extends IActivityManager.Stub

         cleanupAppInLaunchingProvidersLocked(app, true);

         removeProcessLocked(app, false, true, "timeout publishing content providers");

     }

+       

+    @GuardedBy("this")

+    private final void processContentProviderWaitTimedOutLocked(ContentProviderRecord cpr) {

+        try {

+            if (mLaunchingProviders.contains(cpr)) {

+                if (DEBUG_MU) Slog.v(TAG_MU,

+                    "Remove from mLaunchingProviders, " + cpr

+                    + " launchingApp=" + cpr.launchingApp);

+                mLaunchingProviders.remove(cpr);

+            }

+            if (DEBUG_MU) Slog.v(TAG_MU,

+                "RemoveMessages CONTENT_PROVIDER_WAIT_TIMEOUT_MSG, " + cpr

+                + " launchingApp=" + cpr.launchingApp);

+            mHandler.removeMessages(CONTENT_PROVIDER_WAIT_TIMEOUT_MSG, cpr);

+            synchronized (cpr) {

+                cpr.notifyAll();

+                cpr.launchingApp = null;

+            }

+        } catch (Exception e) {

+            if (DEBUG_MU) Slog.v(TAG_MU,

+                "processContentProviderWaitTimedOutLocked exception, " + e);

+        }

+    }

+       

     private final void processStartTimedOutLocked(ProcessRecord app) {

         final int pid = app.pid;

         boolean gone = false;

@@ [-12124,11](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=d5e2e1411f3698a829e997d402c7482ec277fa8c;hb=d5e2e1411f3698a829e997d402c7482ec277fa8c#l12124) [+12157,33](http://192.168.11.104/gitweb/?p=alps-mp-o1.mp1-V1.git;a=blob;f=alps/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java;h=03208f78a2bf3167b4f0790019326e3939cc5444;hb=03208f78a2bf3167b4f0790019326e3939cc5444#l12157) @@ public class ActivityManagerService extends IActivityManager.Stub

                     if (conn != null) {

                         conn.waiting = true;

                     }

+                                       // add 20s wait timeout，avoid 

+                    if (!mHandler.hasMessages(CONTENT_PROVIDER_WAIT_TIMEOUT_MSG, cpr)) {

+                        if (DEBUG_MU) Slog.v(TAG_MU,

+                            "SendMessageDelayed CONTENT_PROVIDER_WAIT_TIMEOUT_MSG, " + cpr

+                            + " launchingApp=" + cpr.launchingApp);

+                        Message msg = mHandler.obtainMessage(CONTENT_PROVIDER_WAIT_TIMEOUT_MSG);

+                        msg.obj = cpr;

+                        mHandler.sendMessageDelayed(msg, CONTENT_PROVIDER_WAIT_TIMEOUT);

+                    } else {

+                        if (DEBUG_MU) Slog.v(TAG_MU,

+                            "There is another waiting to start provider " + cpr

+                            + " launchingApp=" + cpr.launchingApp

+                            + ", not send CONTENT_PROVIDER_WAIT_TIMEOUT_MSG again");

+                    }

+                                       

                     cpr.wait();

                 } catch (InterruptedException ex) {

                 } finally {

                     if (conn != null) {

                         conn.waiting = false;

+                    }

+                                       // remove wait time out message

+                    if (mHandler.hasMessages(CONTENT_PROVIDER_WAIT_TIMEOUT_MSG, cpr)) {

+                        if (DEBUG_MU) Slog.v(TAG_MU,

+                            "After wait removeMessages CONTENT_PROVIDER_WAIT_TIMEOUT_MSG, "

+                            + cpr + " launchingApp=" + cpr.launchingApp);

+                            mHandler.removeMessages(CONTENT_PROVIDER_WAIT_TIMEOUT_MSG, cpr);

                     }

                 }

             }

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