From 60a74318163968ce3db46c1952ed7bc4f8ce530e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=8C=AF=E6=B7=A6=E7=8E=8B?= <wangzglx@gmail.com>
Date: Tue, 1 Dec 2015 16:37:31 +0800
Subject: [PATCH] ConcurrentModificationException in SyncManager

updateRunningAccounts and dispatchSyncOperation is running in different thread,
and mActiveSyncContexts not synchronization.
If methods occur together,
mActiveSyncContexts change may occur when cycle is running.

Sample:
https://code.google.com/p/android/issues/detail?id=195341

Solution:
Offboard the traversal from the main thread to the handler thread.

Change-Id: Ifb9fbb466a5087186be31f7877c50b8c8b6737e4
Signed-off-by: wangzhengan <wangzglx@gmail.com>
---
 .../android/server/content/SyncManager.java   | 52 ++++++++++++-------
 1 file changed, 33 insertions(+), 19 deletions(-)

diff --git a/services/core/java/com/android/server/content/SyncManager.java b/services/core/java/com/android/server/content/SyncManager.java
index 334bc18b82f28..25192bf355a52 100644
--- a/services/core/java/com/android/server/content/SyncManager.java
+++ b/services/core/java/com/android/server/content/SyncManager.java
@@ -315,25 +315,9 @@ public class SyncManager {
     }
 
     public void updateRunningAccounts() {
-        mRunningAccounts = AccountManagerService.getSingleton().getRunningAccounts();
-
-        if (mBootCompleted) {
-            doDatabaseCleanup();
-        }
-
-        AccountAndUser[] accounts = mRunningAccounts;
-        for (ActiveSyncContext currentSyncContext : mActiveSyncContexts) {
-            if (!containsAccountAndUser(accounts,
-                    currentSyncContext.mSyncOperation.target.account,
-                    currentSyncContext.mSyncOperation.target.userId)) {
-                Log.d(TAG, "canceling sync since the account is no longer running");
-                sendSyncFinishedOrCanceledMessage(currentSyncContext,
-                        null /* no result since this is a cancel */);
-            }
-        }
-        // we must do this since we don't bother scheduling alarms when
-        // the accounts are not set yet
-        sendCheckAlarmsMessage();
+        if (Log.isLoggable(TAG, Log.VERBOSE)) Log.v(TAG, "sending MESSAGE_ACCOUNTS_UPDATED");
+        // Update accounts in handler thread.
+        mSyncHandler.sendEmptyMessage(SyncHandler.MESSAGE_ACCOUNTS_UPDATED);
     }
 
     private void doDatabaseCleanup() {
@@ -2098,6 +2082,7 @@ public class SyncManager {
          * obj: {@link com.android.server.content.SyncManager.ActiveSyncContext}
          */
         private static final int MESSAGE_MONITOR_SYNC = 8;
+        private static final int MESSAGE_ACCOUNTS_UPDATED = 9;
 
         public final SyncNotificationInfo mSyncNotificationInfo = new SyncNotificationInfo();
         private Long mAlarmScheduleTime = null;
@@ -2215,6 +2200,13 @@ public class SyncManager {
                 // to also take into account the periodic syncs.
                 earliestFuturePollTime = scheduleReadyPeriodicSyncs();
                 switch (msg.what) {
+                    case SyncHandler.MESSAGE_ACCOUNTS_UPDATED:
+                        if (Log.isLoggable(TAG, Log.VERBOSE)) {
+                            Log.v(TAG, "handleSyncHandlerMessage: MESSAGE_ACCOUNTS_UPDATED");
+                        }
+                        updateRunningAccountsH();
+                        break;
+
                     case SyncHandler.MESSAGE_CANCEL:
                         SyncStorageEngine.EndPoint endpoint = (SyncStorageEngine.EndPoint) msg.obj;
                         Bundle extras = msg.peekData();
@@ -2763,6 +2755,28 @@ public class SyncManager {
             return nextReadyToRunTime;
         }
 
+        private void updateRunningAccountsH() {
+            mRunningAccounts = AccountManagerService.getSingleton().getRunningAccounts();
+
+            if (mBootCompleted) {
+                doDatabaseCleanup();
+            }
+
+            AccountAndUser[] accounts = mRunningAccounts;
+            for (ActiveSyncContext currentSyncContext : mActiveSyncContexts) {
+                if (!containsAccountAndUser(accounts,
+                        currentSyncContext.mSyncOperation.target.account,
+                        currentSyncContext.mSyncOperation.target.userId)) {
+                    Log.d(TAG, "canceling sync since the account is no longer running");
+                    sendSyncFinishedOrCanceledMessage(currentSyncContext,
+                            null /* no result since this is a cancel */);
+                }
+            }
+            // we must do this since we don't bother scheduling alarms when
+            // the accounts are not set yet
+            sendCheckAlarmsMessage();
+        }
+
         private boolean isSyncNotUsingNetworkH(ActiveSyncContext activeSyncContext) {
             final long bytesTransferredCurrent =
                     getTotalBytesTransferredByUid(activeSyncContext.mSyncAdapterUid);