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[김경남 <knamkim@xxxxxxxxx>]

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



 

 

 





  김경남 부책임연구원
    
   솔루션사업본부 정보기술 연구원 
   신기술개발팀
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