maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, 김경남!

You need to call

  my_thread_init()
  
as early as possible in your new thread. And

  my_thread_end()

Just before your thread ends.

Regards,
Sergei

On Mar 30, 김경남 wrote:
> Hi,
> I'm writing mariadb daemon type plugin. 
> I hava a question. 
> 
> In a daemon thread, I want to use THD instance. for example,
> 
> ------------------------------------------------------------------------
> -----------
> class THD;
> static int plugin_init() {
> ...
> pthread_create(&id,&attr,my_func,...);
> }
> 
> void my_func(void* p) 
> {
> THD* thd = new THD;
> thd->thread_stack= (char*) &thd;
> thd->store_globals();
> tables.init_one_table("performance_schema", 18,
> "events_statements_current", 25, "events_statements_current", TL_READ);
> open_and_lock_tables(thd, &tables, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT);
> ...
> }
> 
> ------------------------------------------------------------------------
> --------------------
> but In my_func(), new THD cause error. I guess thread problem. 
> 
> So I moved that code to plugin_init() for test as below
> 
> --------------------------------------------------------------
> class THD;
> static int plugin_init() {
> ...
> pthread_create(&id,&attr,my_func,...);
> THD* thd = new THD;
> thd->thread_stack= (char*) &thd;
> thd->store_globals();
> tables.init_one_table("performance_schema", 18,
> "events_statements_current", 25, "events_statements_current", TL_READ);
> open_and_lock_tables(thd, &tables, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT);
> ...
> }
> ------------------------------------------------------------------------
> -----
> and then there is no problem. but I need a daemon thread. 
> I think that the reason of this error is assertion of thread. So I
> changed my code as below. 
> 
> ------------------------------------------------------------------------
> ---------
> class THD;
> THD* thd;
> static int plugin_init() {
> ...
> pthread_create(&id,&attr,my_func,...);
> THD* thd = new THD;  // moved here from my_func() for avoiding error.
> }
> 
> void my_func(void* p) 
> {
> thd->thread_stack= (char*) &thd;
> thd->store_globals();
> tables.init_one_table("performance_schema", 18,
> "events_statements_current", 25, "events_statements_current", TL_READ);
> open_and_lock_tables(thd, &tables, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT);
> ...
> 
> }
> ------------------------------------------------------------------------
> -----------------
> At this time, thd->store_globals() cause error. 
> In sql_class.cc , mysys_var->id= thread_id    cause error because
> mysys_var is null.
> 
> 
> Let me know how to use THD instance in daemon thread. 
> 
> Regards,
> Kyungnam
>