From: Vladislav Vaintroub
Date: September 1 2008 9:47pm
Subject: bzr commit into mysql-5.1-bugteam branch (vvaintroub:2675) Bug#33031
 Bug#37226
List-Archive: http://lists.mysql.com/commits/53026
X-Bug: 33031,37226
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#At file:///home/vlad/bzr/bt5/

 2675 Vladislav Vaintroub	2008-09-01
      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
modified:
  libmysql/dll.c

=== modified file 'libmysql/dll.c'
--- a/libmysql/dll.c	2004-08-18 17:57:55 +0000
+++ b/libmysql/dll.c	2008-09-01 21:46:37 +0000
@@ -89,9 +89,20 @@ BOOL APIENTRY LibMain(HANDLE hInst,DWORD
   UNREFERENCED_PARAMETER(lpReserved);
 } /* LibMain */
 
+
+static BOOL do_libmain;
 int __stdcall DllMain(HANDLE hInst,DWORD ul_reason_being_called,LPVOID lpReserved)
 {
-  return LibMain(hInst,ul_reason_being_called,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)