差異處

這裏顯示兩個版本的差異處。

--- cpp:sc:queryservicelockstatus [2016/04/19 11:35]
tony [Introduction]
+++ cpp:sc:queryservicelockstatus [2023/06/25 09:48] (目前版本)
@@ 行 1: / 行 1: @@
-{{tag>cpp Windows}}
+{{tag>cpp Windows SCM}}
 ====== QueryServiceLockStatus  ======
 ===== Introduction =====
 某些third-party api會在runtime去新增service，以減少使用者在安裝上的負擔。然而在系統重新啟動時，SCM會lock service database，如果新增service將會造成block。此源自: [[https://msdn.microsoft.com/zh-tw/library/windows/desktop/ms686321(v=vs.85).aspx|link]]
 <code>
-A service cannot call StartService during initialization. The reason is that the SCM locks the service control database during initialization, so a call to StartService will block. After the service reports to the SCM that it has successfully started, it can call StartService.
+A service cannot call StartService during initialization. The reason is that the SCM locks the'
+service control database during initialization, so a call to StartService will block. After the
+service reports to the SCM that it has successfully started, it can call StartService.
 </code>
+因此，我們可以先檢查SCM database是否lock，再決定我們接下來該怎麼做。
 ===== How to? =====
+要解決這問題，可以使用:
+  * API: QueryServiceLockStatus。
+  * Command line: sc querylock。
+首先來看看QueryServiceLockStatus:
+<code cpp>
+BOOL IsSCMRelease(){
+	SC_HANDLE hSCManager;
+	LPQUERY_SERVICE_LOCK_STATUS hStatus;
+	DWORD dwBytesNeeded;
+	BOOL ret;
+	hSCManager=OpenSCManager(NULL, NULL, SC_MANAGER_QUERY_LOCK_STATUS);
+	if (hSCManager) {
+		hStatus = (LPQUERY_SERVICE_LOCK_STATUS) LocalAlloc(LPTR, sizeof(QUERY_SERVICE_LOCK_STATUS)+256);
+		if( hStatus == NULL ) {
+			clog << "LocalAlloc failed. Error: " << GetLastError() << endl;
+			return FALSE;
+		}
+		if( !QueryServiceLockStatus( hSCManager, hStatus, sizeof(QUERY_SERVICE_LOCK_STATUS)+256, &dwBytesNeeded)){
+			clog << "Can't query lock status. Error: " << GetLastError() << endl;
+			ret = FALSE;
+		} else {
+			ret = hStatus->fIsLocked == 0;
+		}
+		CloseServiceHandle(hSCManager);
+		LocalFree(hStatus);
+		return ret;
+	}
+	clog << "Can't open SCManager." << endl;
+	return FALSE;
+}
+</code>
+若透過command line:
+<code bash>
+C:\Users\tonylin>chcp 437 & sc querylock
+Active code page: 437
+[SC] QueryServiceLockStatus SUCCESS
+        IsLocked      : FALSE
+        LockOwner     :
+        LockDuration  : 0 (seconds since acquired)
+</code>
 ===== Reference =====
   * [[https://msdn.microsoft.com/zh-tw/library/windows/desktop/ms684938(v=vs.85).aspx|MSDN - QueryServiceLockStatus]]
   * [[https://msdn.microsoft.com/zh-tw/library/windows/desktop/ms686321(v=vs.85).aspx|MSDN - StartService]]
   * [[https://msdn.microsoft.com/zh-tw/library/windows/desktop/ms685104(v=vs.85).aspx|MSDN - SCM Handles]]
+  * [[http://www.tenouk.com/cpluscodesnippet/changewindowserviceconfig.html|sample code]]
+  * [[https://technet.microsoft.com/zh-tw/sqlserver/ms684953|QUERY_SERVICE_LOCK_STATUS structure]]
 =====    =====
 ----
 \\
 ~~DISQUS~~