Commit b2a49edd authored Sep 01, 2008 by Vladislav Vaintroub

Bug#37226 Explicit call of my_thread_init() on Windows for every new thread.

Bug#33031 app linked to libmysql.lib crash if run as service in vista under
localsystem

There are some problems using DllMain hook functions on Windows that
automatically do global and per-thread initialization for libmysqld.dll

1)per-thread initialization(DLL_THREAD_ATTACH)
MySQL internally counts number of active threads that and causes a delay in in
my_end() if not all threads are exited. But,there are threads that can be
started either by Windows internally (often in TCP/IP scenarios) or by user
himself - those threads are not necessarily using libmysql.dll functionality,
but nonetheless the contribute to the count of open threads.

2)process-initialization (DLL_PROCESS_ATTACH)
my_init() calls WSAStartup that itself loads DLLs and can lead to a deadlock in
Windows loader.

Fix is to remove dll initialization code from libmysql.dll in general case. I
still leave an environment variable LIBMYSQL_DLLINIT, which if set to any value
will cause the old behavior (DLL init hooks will be called). This env.variable
exists only to prevent breakage of existing Windows-only applications that
don't do mysql_thread_init() and work ok today. Use of LIBMYSQL_DLLINIT is
discouraged and it will be removed in 6.0

parent 7e8c1374

libmysql/dll.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -89,9 +89,20 @@ BOOL APIENTRY LibMain(HANDLE hInst,DWORD ul_reason_being_called,
		UNREFERENCED_PARAMETER(lpReserved);
		} /* LibMain */


		static BOOL do_libmain;
		int __stdcall DllMain(HANDLE hInst,DWORD ul_reason_being_called,LPVOID lpReserved)
		{
		/*
		Unless environment variable LIBMYSQL_DLLINIT is set, do nothing.
		The environment variable is checked once, during the first call to DllMain()
		(in DLL_PROCESS_ATTACH hook).
		*/
		if (ul_reason_being_called == DLL_PROCESS_ATTACH)
		do_libmain = (getenv("LIBMYSQL_DLLINIT") != NULL);
		if (do_libmain)
		return LibMain(hInst,ul_reason_being_called,lpReserved);
		return TRUE;
		}

		#elif defined(WINDOWS)