slave start <options> to be able to do

 slave start io_thread 
 slave start sql_thread
same for stop


sql/lex.h:
  slave start <options>
sql/sql_lex.cc:
  slave start <options>
sql/sql_lex.h:
  slave start <options>
sql/sql_repl.cc:
  slave start <options>
sql/sql_yacc.yy:
  slave start <options>

sql/lex.h

@@ -191,6 +191,7 @@ static SYMBOL symbols[] = {
   { "INT4",		SYM(INT_SYM),0,0},
   { "INT8",		SYM(BIGINT),0,0},
   { "INTO",		SYM(INTO),0,0},
+  { "IO_THREAD",        SYM(IO_THREAD),0,0},
   { "IF",		SYM(IF),0,0},
   { "IS",		SYM(IS),0,0},
   { "ISOLATION",	SYM(ISOLATION),0,0},
@@ -327,6 +328,7 @@ static SYMBOL symbols[] = {
   { "SQL_SELECT_LIMIT", SYM(SQL_SELECT_LIMIT),0,0},
   { "SQL_SLAVE_SKIP_COUNTER", SYM(SQL_SLAVE_SKIP_COUNTER),0,0},
   { "SQL_SMALL_RESULT", SYM(SQL_SMALL_RESULT),0,0},
+  { "SQL_THREAD", SYM(SQL_THREAD),0,0},
   { "SQL_WARNINGS",	SYM(SQL_WARNINGS),0,0},
   { "SSL",		SYM(SSL_SYM),0,0},
   { "STRAIGHT_JOIN",	SYM(STRAIGHT_JOIN),0,0},

sql/sql_lex.cc

@@ -150,6 +150,7 @@ LEX *lex_start(THD *thd, uchar *buf,uint length)
   lex->convert_set=(lex->thd=thd)->convert_set;
   lex->yacc_yyss=lex->yacc_yyvs=0;
   lex->ignore_space=test(thd->sql_mode & MODE_IGNORE_SPACE);
+  lex->slave_thd_opt=0;
   return lex;
 }
 

sql/sql_lex.h

@@ -186,7 +186,7 @@ typedef struct st_lex {
   thr_lock_type lock_option;
   bool	drop_primary,drop_if_exists,local_file;
   bool  in_comment,ignore_space,verbose,simple_alter, option_type;
-
+  uint slave_thd_opt;
 } LEX;
 
 

sql/sql_repl.cc

@@ -562,6 +562,8 @@ int start_slave(THD* thd , MASTER_INFO* mi,  bool net_report)
     return 1;
   lock_slave_threads(mi);  // this allows us to cleanly read slave_running
   init_thread_mask(&thread_mask,mi,1 /* inverse */);
+  if (thd->lex.slave_thd_opt)
+    thread_mask &= thd->lex.slave_thd_opt;
   if (thread_mask)
   {
     if (server_id_supplied && (!mi->inited || (mi->inited && *mi->host)))
@@ -602,6 +604,8 @@ int stop_slave(THD* thd, MASTER_INFO* mi, bool net_report )
   int thread_mask;
   lock_slave_threads(mi);
   init_thread_mask(&thread_mask,mi,0 /* not inverse*/);
+  if (thd->lex.slave_thd_opt)
+    thread_mask &= thd->lex.slave_thd_opt;
   slave_errno = (thread_mask) ?
     terminate_slave_threads(mi,thread_mask,
 			    1 /*skip lock */) :    ER_SLAVE_NOT_RUNNING;

sql/sql_yacc.yy

@@ -123,6 +123,8 @@ bool my_yyoverflow(short **a, YYSTYPE **b,int *yystacksize);
 %token  RESET_SYM
 %token  PURGE
 %token  SLAVE
+%token  IO_THREAD
+%token  SQL_THREAD
 %token  START_SYM
 %token  STOP_SYM
 %token	TRUNCATE_SYM
@@ -1256,20 +1258,34 @@ opt_to:
 	| AS		{}
 
 slave:
-	SLAVE START_SYM
+	SLAVE START_SYM slave_thread_opts
          {
 	   LEX *lex=Lex;
            lex->sql_command = SQLCOM_SLAVE_START;
 	   lex->type = 0;
          }
          |
-	SLAVE STOP_SYM
+	SLAVE STOP_SYM slave_thread_opts
          {
 	   LEX *lex=Lex;
            lex->sql_command = SQLCOM_SLAVE_STOP;
 	   lex->type = 0;
          };
 
+slave_thread_opts: slave_thread_opt
+ | slave_thread_opts ',' slave_thread_opt
+
+slave_thread_opt:
+   /*empty*/ {} 
+  | SQL_THREAD
+    {
+      Lex->slave_thd_opt|=SLAVE_SQL;
+    }
+  | IO_THREAD
+    {
+      Lex->slave_thd_opt|=SLAVE_IO;
+    }
+  
 restore:
 	RESTORE_SYM table_or_tables
 	{