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MDEV-33748 get rid of pthread_(get_/set_)specific, use thread_local

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Apart from better performance when accessing thread local variables,
we'll get rid of things that depend on initialization/cleanup of
pthread_key_t variables.

Where appropriate, use compiler-dependent pre-C++11 thread-local
equivalents, where it makes sense, to avoid initialization check overhead
that non-static thread_local can suffer from.
This commit is contained in:
Vladislav Vaintroub
2024-06-07 16:20:10 +02:00
parent 68fed7e785
commit 7c5fdc9b6a
26 changed files with 93 additions and 234 deletions
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21
sql/sql_class.cc
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@@ -5151,23 +5151,22 @@ void destroy_thd(MYSQL_THD thd)
like for example, evaluation of virtual function in innodb
purge.
*/
extern "C" pthread_key(struct st_my_thread_var *, THR_KEY_mysys);
MYSQL_THD create_background_thd()
{
auto save_thd = current_thd;
set_current_thd(nullptr);
auto save_mysysvar= pthread_getspecific(THR_KEY_mysys);
auto save_mysysvar= my_thread_var;
/*
Allocate new mysys_var specifically new THD,
so that e.g safemalloc, DBUG etc are happy.
*/
pthread_setspecific(THR_KEY_mysys, 0);
set_mysys_var(nullptr);
my_thread_init();
auto thd_mysysvar= pthread_getspecific(THR_KEY_mysys);
auto thd_mysysvar= my_thread_var;
auto thd= new THD(0);
pthread_setspecific(THR_KEY_mysys, save_mysysvar);
set_mysys_var(save_mysysvar);
thd->set_psi(nullptr);
set_current_thd(save_thd);
@@ -5200,8 +5199,8 @@ void *thd_attach_thd(MYSQL_THD thd)
DBUG_ASSERT(!current_thd);
DBUG_ASSERT(thd && thd->mysys_var);
auto save_mysysvar= pthread_getspecific(THR_KEY_mysys);
pthread_setspecific(THR_KEY_mysys, thd->mysys_var);
auto save_mysysvar= my_thread_var;
set_mysys_var(thd->mysys_var);
thd->thread_stack= (char *) &thd;
thd->store_globals();
return save_mysysvar;
@@ -5214,7 +5213,7 @@ void *thd_attach_thd(MYSQL_THD thd)
void thd_detach_thd(void *mysysvar)
{
/* Restore mysys_var that is changed when THD was attached.*/
pthread_setspecific(THR_KEY_mysys, mysysvar);
set_mysys_var((st_my_thread_var *)mysysvar);
/* Restore the THD (we assume it was NULL during attach).*/
set_current_thd(0);
}
@@ -5227,7 +5226,7 @@ void destroy_background_thd(MYSQL_THD thd)
{
DBUG_ASSERT(!current_thd);
auto thd_mysys_var= thd->mysys_var;
auto save_mysys_var= thd_attach_thd(thd);
auto save_mysys_var= (st_my_thread_var *)thd_attach_thd(thd);
DBUG_ASSERT(thd_mysys_var != save_mysys_var);
/*
Workaround the adverse effect decrementing thread_count on THD()
@@ -5249,9 +5248,9 @@ void destroy_background_thd(MYSQL_THD thd)
auto save_psi_thread= PSI_CALL_get_thread();
#endif
PSI_CALL_set_thread(0);
pthread_setspecific(THR_KEY_mysys, thd_mysys_var);
set_mysys_var(thd_mysys_var);
my_thread_end();
pthread_setspecific(THR_KEY_mysys, save_mysys_var);
set_mysys_var(save_mysys_var);
PSI_CALL_set_thread(save_psi_thread);
}