"Jeremiah Gowdy" <[EMAIL PROTECTED]> wrote on 10/11/2005 03:08:40 AM:
> The Windows DLL is thread safe. You do not have to call my_init()
> and my_thread_init() because Windows DLLs receive events when they
> are attached to a new process and when they are attached to a new
> thread in a process. This is one of the nicer features of Windows
> shared libraries. Other than that, you don't have to do anything
> special. I am a heavy user of libmysql under Win32. You simply
> mysql_init() your MYSQL struct, and then mysql_real_connect() and
> you're ready to mysql_query().
>
> You should not call my_init() or my_thread_init() as the previous
> poster suggested. This could result in memory leaks.
>
>
> From libmysql/dll.c
>
> BOOL APIENTRY LibMain(HANDLE hInst,DWORD ul_reason_being_called,
> LPVOID lpReserved)
> {
> switch (ul_reason_being_called) {
> case DLL_PROCESS_ATTACH: /* case of libentry call in win 3.x */
> if (!inited++)
> {
> s_hModule=hInst;
> libmysql_init();
> main_thread=GetCurrentThreadId();
> }
> break;
> case DLL_THREAD_ATTACH:
> threads++;
> my_thread_init();
> break;
> case DLL_PROCESS_DETACH: /* case of wep call in win 3.x */
> if (!--inited) /* Safety */
> {
> /* my_thread_init() */ /* This may give extra safety */
> my_end(0);
> }
> break;
> case DLL_THREAD_DETACH:
> /* Main thread will free by my_end() */
> threads--;
> if (main_thread != GetCurrentThreadId())
> my_thread_end();
> break;
> default:
> break;
> } /* switch */
> return TRUE;
> UNREFERENCED_PARAMETER(lpReserved);
> } /* LibMain */
>
> ----- Original Message -----
> From: "John McCaskey" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>;
<[email protected]>
> Sent: Friday, October 07, 2005 10:31 AM
> Subject: RE: How thread-safe is mysql_real_connect()?
>
>
> Sean,
>
> First let me thank you for all the great posts and info I've seen you
> put on this list for others.
>
> I've been working in C with MySQL in a very multithreaded environment
> for several years and think I can explain the thread safety issues
> clearly. Rather than try to respond point by point to your question I'm
> going to give a summary and if that doesn't help please respond again
> and I'll answer specific questions.
>
> First, mysql is in fact pretty much threadsafe when using the _r
> library. You definitely do need to use the _r library and not the
> normal one as the SIGPIPE discussion applies to both, the non _r library
> has additional safety issues surrounding mysql_real_connect() and should
> not be used. On windows you don't really need to do anything here I
> believe because "the Windows binaries are by default compiled to be
> thread-safe." (from
> http://dev.mysql.com/doc/mysql/en/threaded-clients.html). To validate
> this in your client code you should in the main() function close to
> startup use mysql_thread_safe() to verify your linked in version is
> thread safe.
>
> The next thing you need to do is initialize mysql globally before
> creating any threads that will use it. Simply call my_init(); in your
> main thread. After this you can go ahead and create any threads. In
> the threads you create you need to call mysql_thread_init(); and when
> you end the thread mysql_thread_end(); in between these calls you can
> just use mysql as normal and the mysql_real_connect function will be
> thread safe, you do not need to perform any locking of your own to make
> only one call at a time or anything along those lines.
>
> Here is some pseudo code of what you need to do:
>
> int main(int argc, char **argv) {
>
> if(!mysql_thread_safe()) {
> fprintf(stderr, "Not Thread safe!!!");
> return 1;
> }
>
> my_init();
>
> // your regular init code
>
> // create the threads that will use mysql
> CreateThread(....);
>
>
> }
>
> void *mysql_thread(void *arg) {
> mysql_thread_init();
>
>
> //regular mysql code and whatever else here
> //use mysql_real_connect and mysql_real_query
> //and whatever without worrying about thread safety
>
>
>
> mysql_thread_end();
> }
>
>
>
>
> John A. McCaskey
> Software Development Engineer
> Klir Technologies, Inc.
> [EMAIL PROTECTED]
> 206.902.2027
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
> Sent: Friday, October 07, 2005 9:01 AM
> To: [EMAIL PROTECTED]; [email protected]
> Subject: How thread-safe is mysql_real_connect()?
>
<snip>
>
> Shawn Green
> Database Administrator
> Unimin Corporation - Spruce Pine
>
Thank you very much!!
Shawn Green
Database Administrator
Unimin Corporation - Spruce Pine
