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 automaticly 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:
-Fixed test cases that depends on changes for LOCK_grant
-Added thread_safe_decrement32() and thread_safe_increment32()
-Removed sql_rnd_with_mutex() and get_thread_running()
-In check_table_access() don't lock LOCK_grant if we can resolve the grant with user or db level grants (the normal case).
-Don't use a lock for setting THD->query_id.
-Fixed bug where thd->set_query_id() could be set to same value by multiple threads.

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
mysql-test/suite/perfschema/t/func_mutex.test:
  Test for LOCK_system_variables_hash instead of LOCK_grant, as LOCK_grant is not anymore always taken for SELECT's.
mysys/my_gethwaddr.c:
  More DBUG
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
  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()
  next_query_id() should return the original value for global_query_id, not the next one.
  (Bug introduced with MySQL 5.5 merge).
sql/sql_acl.cc:
  In check_table_access() don't lock LOCK_grant if we can resolve the grant with user or db level grants (the normal case).
sql/sql_class.cc:
  Removed thd_lock_thread_count() and thd_unlock_thread_count()
  Initialize random generator without locks
  Don't use a lock for setting THD->query_id.
  (This is only accessed by thread owning the THD)
sql/sql_class.h:
  Don't use a lock for setting THD->query_id.
sql/sql_insert.cc:
  Changed thread_count to be automically incremented
sql/sql_parse.cc:
  Changed thread_count to be automically incremented
  Fixed bug where thd->set_query_id() could be set to same value by multiple threads.
vio/vio.c:
  Don't generate 'desc' with sprintf/strmov. Assign a pointer instead.
  (Good enough as this is just for debugging)

include/violite.h

@@ -216,7 +216,7 @@ struct st_vio
   struct sockaddr_storage	remote;		/* Remote internet address */
   int addrLen;                          /* Length of remote address */
   enum enum_vio_type	type;		/* Type of connection */
-  char			desc[30];	/* String description */
+  const char		*desc;		/* String description */
   char                  *read_buffer;   /* buffer for vio_read_buff */
   char                  *read_pos;      /* start of unfetched data in the
                                            read buffer */

mysql-test/suite/perfschema/r/all_instances.result

@@ -64,6 +64,7 @@ wait/synch/mutex/sql/LOCK_server_started
 wait/synch/mutex/sql/LOCK_slave_list
 wait/synch/mutex/sql/LOCK_stats
 wait/synch/mutex/sql/LOCK_status
+wait/synch/mutex/sql/LOCK_thread_cache
 wait/synch/mutex/sql/LOCK_thread_count
 wait/synch/mutex/sql/LOCK_user_conn
 wait/synch/mutex/sql/LOCK_user_locks

mysql-test/suite/perfschema/r/func_mutex.result

@@ -70,52 +70,34 @@ Success
 TRUNCATE TABLE performance_schema.events_waits_history_long;
 TRUNCATE TABLE performance_schema.events_waits_history;
 TRUNCATE TABLE performance_schema.events_waits_current;
-SELECT * FROM t1 WHERE id = 1;
-id	b
-1	initial value
+show variables like "%not_found%";
+Variable_name	Value
 SET @before_count = (SELECT SUM(TIMER_WAIT)
 FROM performance_schema.events_waits_history_long
-WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_grant'));
-SELECT * FROM t1;
-id	b
-1	initial value
-2	initial value
-3	initial value
-4	initial value
-5	initial value
-6	initial value
-7	initial value
-8	initial value
+WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_system_variables_hash'));
+show variables like "%not_found%";
+Variable_name	Value
 SET @after_count = (SELECT SUM(TIMER_WAIT)
 FROM performance_schema.events_waits_history_long
-WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_grant'));
+WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_system_variables_hash'));
 SELECT IF((@after_count - @before_count) > 0, 'Success', 'Failure') test_fm1_rw_timed;
 test_fm1_rw_timed
 Success
 UPDATE performance_schema.setup_instruments SET enabled = 'NO'
-WHERE NAME = 'wait/synch/rwlock/sql/LOCK_grant';
+WHERE NAME = 'wait/synch/rwlock/sql/LOCK_system_variables_hash';
 TRUNCATE TABLE performance_schema.events_waits_history_long;
 TRUNCATE TABLE performance_schema.events_waits_history;
 TRUNCATE TABLE performance_schema.events_waits_current;
-SELECT * FROM t1 WHERE id = 1;
-id	b
-1	initial value
+show variables like "%not_found%";
+Variable_name	Value
 SET @before_count = (SELECT SUM(TIMER_WAIT)
 FROM performance_schema.events_waits_history_long
-WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_grant'));
-SELECT * FROM t1;
-id	b
-1	initial value
-2	initial value
-3	initial value
-4	initial value
-5	initial value
-6	initial value
-7	initial value
-8	initial value
+WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_system_variables_hash'));
+show variables like "%not_found%";
+Variable_name	Value
 SET @after_count = (SELECT SUM(TIMER_WAIT)
 FROM performance_schema.events_waits_history_long
-WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_grant'));
+WHERE (EVENT_NAME = 'LOCK_system_variables_hash'));
 SELECT IF((COALESCE(@after_count, 0) - COALESCE(@before_count, 0)) = 0, 'Success', 'Failure') test_fm2_rw_timed;
 test_fm2_rw_timed
 Success

mysql-test/suite/perfschema/t/func_mutex.test

@@ -87,38 +87,38 @@ TRUNCATE TABLE performance_schema.events_waits_history_long;
 TRUNCATE TABLE performance_schema.events_waits_history;
 TRUNCATE TABLE performance_schema.events_waits_current;
 
-SELECT * FROM t1 WHERE id = 1;
+show variables like "%not_found%";
 
 SET @before_count = (SELECT SUM(TIMER_WAIT)
                      FROM performance_schema.events_waits_history_long
-                     WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_grant'));
+                     WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_system_variables_hash'));
 
-SELECT * FROM t1;
+show variables like "%not_found%";
 
 SET @after_count = (SELECT SUM(TIMER_WAIT)
                     FROM performance_schema.events_waits_history_long
-                    WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_grant'));
+                    WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_system_variables_hash'));
 
 SELECT IF((@after_count - @before_count) > 0, 'Success', 'Failure') test_fm1_rw_timed;
 
 UPDATE performance_schema.setup_instruments SET enabled = 'NO'
-WHERE NAME = 'wait/synch/rwlock/sql/LOCK_grant';
+WHERE NAME = 'wait/synch/rwlock/sql/LOCK_system_variables_hash';
 
 TRUNCATE TABLE performance_schema.events_waits_history_long;
 TRUNCATE TABLE performance_schema.events_waits_history;
 TRUNCATE TABLE performance_schema.events_waits_current;
 
-SELECT * FROM t1 WHERE id = 1;
+show variables like "%not_found%";
 
 SET @before_count = (SELECT SUM(TIMER_WAIT)
                      FROM performance_schema.events_waits_history_long
-                     WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_grant'));
+                     WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_system_variables_hash'));
 
-SELECT * FROM t1;
+show variables like "%not_found%";
 
 SET @after_count = (SELECT SUM(TIMER_WAIT)
                     FROM performance_schema.events_waits_history_long
-                    WHERE (EVENT_NAME = 'wait/synch/rwlock/sql/LOCK_grant'));
+                    WHERE (EVENT_NAME = 'LOCK_system_variables_hash'));
 
 SELECT IF((COALESCE(@after_count, 0) - COALESCE(@before_count, 0)) = 0, 'Success', 'Failure') test_fm2_rw_timed;
 

mysys/my_gethwaddr.c

@@ -87,13 +87,17 @@ my_bool my_gethwaddr(uchar *to)
   int fd, res= 1;
   struct ifreq ifr[32];
   struct ifconf ifc;
+  DBUG_ENTER("my_gethwaddr");
 
   ifc.ifc_req= ifr;
   ifc.ifc_len= sizeof(ifr);
 
   fd = socket(AF_INET, SOCK_DGRAM, 0);
   if (fd < 0)
+  {
+    DBUG_PRINT("error", ("socket() call failed with %d", errno));
     goto err;
+  }
 
   if (ioctl(fd, SIOCGIFCONF, (char*)&ifc) >= 0)
   {
@@ -106,8 +110,8 @@ my_bool my_gethwaddr(uchar *to)
                              ETHER_ADDR_LEN);
 #else
       /*
-        A bug in OpenSolaris used to prevent non-root from getting a mac address:
-        {no url. Oracle killed the old OpenSolaris bug database}
+        A bug in OpenSolaris used to prevent non-root from getting a mac
+        address: {no url. Oracle killed the old OpenSolaris bug database}
 
         Thus, we'll use an alternative method and extract the address from the
         arp table.
@@ -124,7 +128,7 @@ my_bool my_gethwaddr(uchar *to)
 
   close(fd);
 err:
-  return res;
+  DBUG_RETURN(res);
 }
 
 #elif defined(_WIN32)

mysys/my_rnd.c

@@ -45,11 +45,20 @@ void my_rnd_init(struct my_rnd_struct *rand_st, ulong seed1, ulong seed2)
     
   RETURN VALUE
     generated pseudo random number
+
+  NOTE:
+    This is codes so that it can be called by two threads at the same time
+    with minimum impact.
+    (As the number is supposed to be random, it doesn't matter much if
+    rand->seed1 or rand->seed2 are updated with slightly wrong numbers or
+    if two threads gets the same number.
 */
 
 double my_rnd(struct my_rnd_struct *rand_st)
 {
-  rand_st->seed1=(rand_st->seed1*3+rand_st->seed2) % rand_st->max_value;
-  rand_st->seed2=(rand_st->seed1+rand_st->seed2+33) % rand_st->max_value;
-  return (((double) rand_st->seed1)/rand_st->max_value_dbl);
+  unsigned long seed1;
+  seed1= (rand_st->seed1*3+rand_st->seed2) % rand_st->max_value;
+  rand_st->seed2=(seed1+rand_st->seed2+33) % rand_st->max_value;
+  rand_st->seed1= seed1;
+  return (((double) seed1)/rand_st->max_value_dbl);
 }

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);

sql/mysqld.h

@@ -56,6 +56,7 @@ void kill_mysql(void);
 void close_connection(THD *thd, uint sql_errno= 0);
 void handle_connection_in_main_thread(THD *thd);
 void create_thread_to_handle_connection(THD *thd);
+void delete_running_thd(THD *thd);
 void unlink_thd(THD *thd);
 bool one_thread_per_connection_end(THD *thd, bool put_in_cache);
 void flush_thread_cache();
@@ -89,7 +90,6 @@ extern bool opt_ignore_builtin_innodb;
 extern my_bool opt_character_set_client_handshake;
 extern bool volatile abort_loop;
 extern bool in_bootstrap;
-extern uint volatile thread_count;
 extern uint connection_count;
 extern my_bool opt_safe_user_create;
 extern my_bool opt_safe_show_db, opt_local_infile, opt_myisam_use_mmap;
@@ -352,7 +352,8 @@ extern mysql_rwlock_t LOCK_system_variables_hash;
 extern mysql_cond_t COND_thread_count;
 extern mysql_cond_t COND_manager;
 extern int32 thread_running;
-extern my_atomic_rwlock_t thread_running_lock;
+extern int32 thread_count;
+extern my_atomic_rwlock_t thread_running_lock, thread_count_lock;
 
 extern char *opt_ssl_ca, *opt_ssl_capath, *opt_ssl_cert, *opt_ssl_cipher,
             *opt_ssl_key;
@@ -449,7 +450,7 @@ inline query_id_t next_query_id()
   my_atomic_rwlock_wrlock(&global_query_id_lock);
   id= my_atomic_add64(&global_query_id, 1);
   my_atomic_rwlock_wrunlock(&global_query_id_lock);
-  return (id+1);
+  return (id);
 }
 
 inline query_id_t get_query_id()
@@ -479,42 +480,30 @@ inline void table_case_convert(char * name, uint length)
                                      name, length, name, length);
 }
 
-inline ulong sql_rnd_with_mutex()
+inline void thread_safe_increment32(int32 *value, my_atomic_rwlock_t *lock)
 {
-  mysql_mutex_lock(&LOCK_thread_count);
-  ulong tmp=(ulong) (my_rnd(&sql_rand) * 0xffffffff); /* make all bits random */
-  mysql_mutex_unlock(&LOCK_thread_count);
-  return tmp;
+  my_atomic_rwlock_wrlock(lock);
+  (void) my_atomic_add32(value, 1);
+  my_atomic_rwlock_wrunlock(lock);
 }
 
-inline int32
-inc_thread_running()
+inline void thread_safe_decrement32(int32 *value, my_atomic_rwlock_t *lock)
 {
-  int32 num_thread_running;
-  my_atomic_rwlock_wrlock(&thread_running_lock);
-  num_thread_running= my_atomic_add32(&thread_running, 1);
-  my_atomic_rwlock_wrunlock(&thread_running_lock);
-  return (num_thread_running+1);
+  my_atomic_rwlock_wrlock(lock);
+  (void) my_atomic_add32(value, -1);
+  my_atomic_rwlock_wrunlock(lock);
 }
 
-inline int32
-dec_thread_running()
+inline void
+inc_thread_running()
 {
-  int32 num_thread_running;
-  my_atomic_rwlock_wrlock(&thread_running_lock);
-  num_thread_running= my_atomic_add32(&thread_running, -1);
-  my_atomic_rwlock_wrunlock(&thread_running_lock);
-  return (num_thread_running-1);
+  thread_safe_increment32(&thread_running, &thread_running_lock);
 }
 
-inline int32
-get_thread_running()
+inline void
+dec_thread_running()
 {
-  int32 num_thread_running;
-  my_atomic_rwlock_wrlock(&thread_running_lock);
-  num_thread_running= my_atomic_load32(&thread_running);
-  my_atomic_rwlock_wrunlock(&thread_running_lock);
-  return num_thread_running;
+  thread_safe_decrement32(&thread_running, &thread_running_lock);
 }
 
 void set_server_version(void);

sql/sql_acl.cc

@@ -4530,12 +4530,16 @@ end:
   @see check_access
   @see check_table_access
 
-  @note This functions assumes that either number of tables to be inspected
+  @note
+     This functions assumes that either number of tables to be inspected
      by it is limited explicitly (i.e. is is not UINT_MAX) or table list
      used and thd->lex->query_tables_own_last value correspond to each
      other (the latter should be either 0 or point to next_global member
      of one of elements of this table list).
 
+     We delay locking of LOCK_grant until we really need it as we assume that
+     most privileges be resolved with user or db level accesses.
+
    @return Access status
      @retval FALSE Access granted; But column privileges might need to be
       checked.
@@ -4552,6 +4556,8 @@ bool check_grant(THD *thd, ulong want_access, TABLE_LIST *tables,
   Security_context *sctx= thd->security_ctx;
   uint i;
   ulong orig_want_access= want_access;
+  my_bool locked= 0;
+  GRANT_TABLE *grant_table;
   DBUG_ENTER("check_grant");
   DBUG_ASSERT(number > 0);
 
@@ -4575,11 +4581,9 @@ bool check_grant(THD *thd, ulong want_access, TABLE_LIST *tables,
     */
     tl->grant.orig_want_privilege= (want_access & ~SHOW_VIEW_ACL);
   }
+  number= i;
 
-  mysql_rwlock_rdlock(&LOCK_grant);
-  for (tl= tables;
-       tl && number-- && tl != first_not_own_table;
-       tl= tl->next_global)
+  for (tl= tables; number-- ; tl= tl->next_global)
   {
     sctx = test(tl->security_ctx) ? tl->security_ctx : thd->security_ctx;
 
@@ -4632,13 +4636,18 @@ bool check_grant(THD *thd, ulong want_access, TABLE_LIST *tables,
       }
       continue;
     }
-    GRANT_TABLE *grant_table= table_hash_search(sctx->host, sctx->ip,
+
+    if (!locked)
+    {
+      locked= 1;
+      mysql_rwlock_rdlock(&LOCK_grant);
+    }
+
+    if (!(grant_table= table_hash_search(sctx->host, sctx->ip,
                                          tl->get_db_name(),
                                          sctx->priv_user,
                                          tl->get_table_name(),
-                                                FALSE);
-
-    if (!grant_table)
+                                         FALSE)))
     {
       want_access &= ~tl->grant.privilege;
       goto err;					// No grants
@@ -4665,10 +4674,12 @@ bool check_grant(THD *thd, ulong want_access, TABLE_LIST *tables,
       goto err;					// impossible
     }
   }
+  if (locked)
     mysql_rwlock_unlock(&LOCK_grant);
   DBUG_RETURN(FALSE);
 
 err:
+  if (locked)
     mysql_rwlock_unlock(&LOCK_grant);
   if (!no_errors)				// Not a silent skip of table
   {

sql/sql_class.cc

@@ -349,29 +349,6 @@ void thd_set_thread_stack(THD *thd, char *stack_start)
   thd->thread_stack= stack_start;
 }
 
-/**
-  Lock connection data for the set of connections this connection
-  belongs to
-
-  @param thd                       THD object
-*/
-void thd_lock_thread_count(THD *)
-{
-  mysql_mutex_lock(&LOCK_thread_count);
-}
-
-/**
-  Lock connection data for the set of connections this connection
-  belongs to
-
-  @param thd                       THD object
-*/
-void thd_unlock_thread_count(THD *)
-{
-  mysql_cond_broadcast(&COND_thread_count);
-  mysql_mutex_unlock(&LOCK_thread_count);
-}
-
 /**
   Close the socket used by this connection
 
@@ -947,7 +924,14 @@ THD::THD()
   protocol_binary.init(this);
 
   tablespace_op=FALSE;
-  tmp= sql_rnd_with_mutex();
+
+  /*
+    Initialize the random generator. We call my_rnd() without a lock as
+    it's not really critical if two threads modifies the structure at the
+    same time.  We ensure that we have an unique number foreach thread
+    by adding the address of the stack.
+  */
+  tmp= (ulong) (my_rnd(&sql_rand) * 0xffffffff);
   my_rnd_init(&rand, tmp + (ulong) &rand, tmp + (ulong) ::global_query_id);
   substitute_null_with_insert_id = FALSE;
   thr_lock_info_init(&lock_info); /* safety: will be reset after start */
@@ -4342,17 +4326,8 @@ void THD::set_query_and_id(char *query_arg, uint32 query_length_arg,
 {
   mysql_mutex_lock(&LOCK_thd_data);
   set_query_inner(query_arg, query_length_arg, cs);
-  query_id= new_query_id;
   mysql_mutex_unlock(&LOCK_thd_data);
-}
-
-/** Assign a new value to thd->query_id.  */
-
-void THD::set_query_id(query_id_t new_query_id)
-{
-  mysql_mutex_lock(&LOCK_thd_data);
   query_id= new_query_id;
-  mysql_mutex_unlock(&LOCK_thd_data);
 }
 
 /** Assign a new value to thd->mysys_var.  */

sql/sql_class.h

@@ -3076,7 +3076,10 @@ public:
   { set_query(CSET_STRING()); }
   void set_query_and_id(char *query_arg, uint32 query_length_arg,
                         CHARSET_INFO *cs, query_id_t new_query_id);
-  void set_query_id(query_id_t new_query_id);
+  void set_query_id(query_id_t new_query_id)
+  {
+    query_id= new_query_id;
+  }
   void set_open_tables(TABLE *open_tables_arg)
   {
     mysql_mutex_lock(&LOCK_thd_data);

sql/sql_insert.cc

@@ -2038,9 +2038,9 @@ public:
     thd.unlink();				// Must be unlinked under lock
     my_free(thd.query());
     thd.security_ctx->user= thd.security_ctx->host=0;
-    thread_count--;
     delayed_insert_threads--;
     mysql_mutex_unlock(&LOCK_thread_count);
+    thread_safe_decrement32(&thread_count, &thread_count_lock);
     mysql_cond_broadcast(&COND_thread_count); /* Tell main we are ready */
   }
 
@@ -2175,9 +2175,9 @@ bool delayed_get_table(THD *thd, MDL_request *grl_protection_request,
     {
       if (!(di= new Delayed_insert()))
         goto end_create;
-      mysql_mutex_lock(&LOCK_thread_count);
-      thread_count++;
-      mysql_mutex_unlock(&LOCK_thread_count);
+
+      thread_safe_increment32(&thread_count, &thread_count_lock);
+
       /*
         Annotating delayed inserts is not supported.
       */

sql/sql_parse.cc

@@ -645,9 +645,10 @@ end:
   delete thd;
 
 #ifndef EMBEDDED_LIBRARY
-  mysql_mutex_lock(&LOCK_thread_count);
-  thread_count--;
+  thread_safe_decrement32(&thread_count, &thread_count_lock);
   in_bootstrap= FALSE;
+
+  mysql_mutex_lock(&LOCK_thread_count);
   mysql_cond_broadcast(&COND_thread_count);
   mysql_mutex_unlock(&LOCK_thread_count);
   my_thread_end();
@@ -930,9 +931,16 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
   thd->query_plan_flags= QPLAN_INIT;
   thd->lex->sql_command= SQLCOM_END; /* to avoid confusing VIEW detectors */
   thd->set_time();
-  thd->set_query_id(get_query_id());
   if (!(server_command_flags[command] & CF_SKIP_QUERY_ID))
-    next_query_id();
+    thd->set_query_id(next_query_id());
+  else
+  {
+    /*
+      ping, get statistics or similar stateless command.
+      No reason to increase query id here.
+    */
+    thd->set_query_id(get_query_id());
+  }
   inc_thread_running();
 
   if (!(server_command_flags[command] & CF_SKIP_QUESTIONS))
@@ -5021,6 +5029,10 @@ check_access(THD *thd, ulong want_access, const char *db, ulong *save_priv,
 
   if ((db != NULL) && (db != any_db))
   {
+    /*
+      Check if this is reserved database, like information schema or
+      performance schema
+    */
     const ACL_internal_schema_access *access;
     access= get_cached_schema_access(grant_internal_info, db);
     if (access)

vio/vio.c

@@ -213,9 +213,7 @@ Vio *vio_new(my_socket sd, enum enum_vio_type type, uint flags)
   if ((vio = (Vio*) my_malloc(sizeof(*vio),MYF(MY_WME))))
   {
     vio_init(vio, type, sd, 0, flags);
-    sprintf(vio->desc,
-	    (vio->type == VIO_TYPE_SOCKET ? "socket (%d)" : "TCP/IP (%d)"),
-	    vio->sd);
+    vio->desc= (vio->type == VIO_TYPE_SOCKET ? "socket" : "TCP/IP");
 #if !defined(__WIN__)
 #if !defined(NO_FCNTL_NONBLOCK)
     /*
@@ -257,7 +255,7 @@ Vio *vio_new_win32pipe(HANDLE hPipe)
   if ((vio = (Vio*) my_malloc(sizeof(Vio),MYF(MY_WME))))
   {
     vio_init(vio, VIO_TYPE_NAMEDPIPE, 0, hPipe, VIO_LOCALHOST);
-    strmov(vio->desc, "named pipe");
+    vio->desc= "named pipe";
   }
   DBUG_RETURN(vio);
 }
@@ -282,7 +280,7 @@ Vio *vio_new_win32shared_memory(HANDLE handle_file_map, HANDLE handle_map,
     vio->event_conn_closed= event_conn_closed;
     vio->shared_memory_remain= 0;
     vio->shared_memory_pos= handle_map;
-    strmov(vio->desc, "shared memory");
+    vio->desc= "shared memory";
   }
   DBUG_RETURN(vio);
 }