perfschema: use LOCK_thd_kill to "keep THD during materialization"

fixes the failure of

./mtr --ps sys_vars.gtid_slave_pos_grant sysschema.v_session_ssl_status

safe_mutex: Found wrong usage of mutex 'LOCK_thd_data' and 'LOCK_active_mi'

storage/perfschema/pfs_variable.cc

@@ -254,7 +254,7 @@ int PFS_system_variable_cache::do_materialize_all(THD *unsafe_thd)
     }
 
     /* Release lock taken in get_THD(). */
-    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_kill);
 
     m_materialized= true;
     ret= 0;
@@ -354,7 +354,7 @@ int PFS_system_variable_cache::do_materialize_session(PFS_thread *pfs_thread)
     }
 
     /* Release lock taken in get_THD(). */
-    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_kill);
 
     m_materialized= true;
     ret= 0;
@@ -407,7 +407,7 @@ int PFS_system_variable_cache::do_materialize_session(PFS_thread *pfs_thread, ui
     }
 
     /* Release lock taken in get_THD(). */
-    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_kill);
 
     m_materialized= true;
     ret= 0;
@@ -458,7 +458,7 @@ int PFS_system_variable_cache::do_materialize_session(THD *unsafe_thd)
     }
 
     /* Release lock taken in get_THD(). */
-    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_kill);
 
     m_materialized= true;
     ret= 0;
@@ -990,7 +990,7 @@ int PFS_status_variable_cache::do_materialize_all(THD* unsafe_thd)
     manifest(m_safe_thd, m_show_var_array.front(), status_vars, "", false, false);
 
     /* Release lock taken in get_THD(). */
-    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_kill);
 
     m_materialized= true;
     ret= 0;
@@ -1036,7 +1036,7 @@ int PFS_status_variable_cache::do_materialize_session(THD* unsafe_thd)
     manifest(m_safe_thd, m_show_var_array.front(), status_vars, "", false, true);
 
     /* Release lock taken in get_THD(). */
-    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_kill);
 
     m_materialized= true;
     ret= 0;
@@ -1078,7 +1078,7 @@ int PFS_status_variable_cache::do_materialize_session(PFS_thread *pfs_thread)
     manifest(m_safe_thd, m_show_var_array.front(), status_vars, "", false, true);
 
     /* Release lock taken in get_THD(). */
-    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_kill);
 
     m_materialized= true;
     ret= 0;

storage/perfschema/pfs_variable.h

@@ -212,7 +212,7 @@ class Find_THD_variable : public Find_THD_Impl
       return false;
 
     /* Hold this lock to keep THD during materialization. */
-    mysql_mutex_lock(&thd->LOCK_thd_data);
+    mysql_mutex_lock(&thd->LOCK_thd_kill);
     return true;
   }
   void set_unsafe_thd(THD *unsafe_thd) { m_unsafe_thd= unsafe_thd; }