Speed up connection time:

-Change my_rnd() slightly to make it safer if two threads use it at the same time.
-Avoid some sprintf and strmov in vio.
-Changed thread_count to be automically incremented (instead of under LOCK_thread_count).
-Thread cache now uses LOCK_thread_cache instead of LOCK_thread_count.
-Moved delete thd out from LOCK_thread_count.
-Save some mysql_cond_broadcast(&COND_thread_count) calls.
-Removed call to getsockname() during connect.
-Initialize random generator without locks.

Other things:
-Added thread_safe_decrement32() and thread_safe_increment32()
-Removed sql_rnd_with_mutex() and get_thread_running()

Thanks to Yoshinori Matsunobu for the benchmark of connection speed and to
Domas Mituzas for the inspiration for many of the fixes.
 

include/violite.h:
  Change desc to a string pointer
mysql-test/suite/perfschema/r/all_instances.result:
  Added new mutex
mysys/my_rnd.c:
  Change my_rnd() slightly to make it safer if two threads use it at the same time.
sql/event_scheduler.cc:
  Changed thread_count to be automically incremented
  Moved some safe things out from LOCK_thread_count.
  Simplify deleting of THD for running thread.
sql/mysqld.cc:
  Changed thread_count to be automically incremented
  Thread cache now uses LOCK_thread_cache instead of LOCK_thread_count
  Added delete_running_thd()
  Moved delete thd out from LOCK_thread_count
  More DBUG_ENTER
  Only call  mysql_cond_broadcast(&COND_thread_count) if thread_count is 0
  Removed call to getsockname() (old not anymore needed check)
sql/mysqld.h:
  Removed sql_rnd_with_mutex() (not needed anymore)
  Removed not used function get_thread_running()
  Added thread_safe_decrement32() and thread_safe_increment32()
  Simplified dec_thread_running() and inc_thread_running()
sql/sql_class.cc:
  Removed thd_lock_thread_count() and thd_unlock_thread_count()
  Initialize random generator without locks
sql/sql_insert.cc:
  Changed thread_count to be automically incremented
sql/sql_parse.cc:
  Changed thread_count to be automically incremented
vio/vio.c:
  Don't generate 'desc' with sprintf/strmov. Assign a pointer instead.
  (Good enough as this is just for debugging)

sql/event_scheduler.cc

@@ -132,11 +132,11 @@ post_init_event_thread(THD *thd)
     return TRUE;
   }
 
+  thread_safe_increment32(&thread_count, &thread_count_lock);
   mysql_mutex_lock(&LOCK_thread_count);
   threads.append(thd);
-  thread_count++;
-  inc_thread_running();
   mysql_mutex_unlock(&LOCK_thread_count);
+  inc_thread_running();
   return FALSE;
 }
 
@@ -154,12 +154,8 @@ deinit_event_thread(THD *thd)
 {
   thd->proc_info= "Clearing";
   DBUG_PRINT("exit", ("Event thread finishing"));
-  mysql_mutex_lock(&LOCK_thread_count);
-  thread_count--;
-  dec_thread_running();
-  delete thd;
-  mysql_cond_broadcast(&COND_thread_count);
-  mysql_mutex_unlock(&LOCK_thread_count);
+
+  delete_running_thd(thd);
 }
 
 
@@ -436,12 +432,7 @@ Event_scheduler::start()
     ret= TRUE;
 
     new_thd->proc_info= "Clearing";
-    mysql_mutex_lock(&LOCK_thread_count);
-    thread_count--;
-    dec_thread_running();
-    delete new_thd;
-    mysql_cond_broadcast(&COND_thread_count);
-    mysql_mutex_unlock(&LOCK_thread_count);
+    delete_running_thd(new_thd);
   }
 end:
   UNLOCK_DATA();
@@ -570,12 +561,7 @@ error:
   if (new_thd)
   {
     new_thd->proc_info= "Clearing";
-    mysql_mutex_lock(&LOCK_thread_count);
-    thread_count--;
-    dec_thread_running();
-    delete new_thd;
-    mysql_cond_broadcast(&COND_thread_count);
-    mysql_mutex_unlock(&LOCK_thread_count);
+    delete_running_thd(new_thd);
   }
   delete event_name;
   DBUG_RETURN(TRUE);