BUG#31024: STOP SLAVE does not stop attempted connect()s

Problem: if the IO slave thread is attempting to connect,
STOP SLAVE waits for the attempt to finish. 
It may take a long time.
Fix: don't wait, stop the slave immediately.


sql/slave.cc:
  Send a SIGALRM signal to the slave thread when stopping it (using
  pthread_kill()). This breaks current socket(), connect(), poll() etc.
  calls, and makes the subsequent thd->awake() call effective.
  
  Also, move the definition of KICK_SLAVE to slave.cc.
sql/sql_repl.h:
  Removed KICK_SLAVE and inlined it in slave.cc because:
   - it was only called once, so better to make it local to where it is used
   - it needed to include a preprocessor conditional in the middle

sql/slave.cc

@@ -699,7 +699,20 @@ int terminate_slave_thread(THD* thd, pthread_mutex_t* term_lock,
   while (*slave_running)			// Should always be true
   {
     DBUG_PRINT("loop", ("killing slave thread"));
-    KICK_SLAVE(thd);
+
+    pthread_mutex_lock(&thd->LOCK_delete);
+#ifndef DONT_USE_THR_ALARM
+    /*
+      Error codes from pthread_kill are:
+      EINVAL: invalid signal number (can't happen)
+      ESRCH: thread already killed (can happen, should be ignored)
+    */
+    IF_DBUG(int err= ) pthread_kill(thd->real_id, thr_client_alarm);
+    DBUG_ASSERT(err != EINVAL);
+#endif
+    thd->awake(THD::NOT_KILLED);
+    pthread_mutex_unlock(&thd->LOCK_delete);
+
     /*
       There is a small chance that slave thread might miss the first
       alarm. To protect againts it, resend the signal until it reacts

sql/sql_repl.h

@@ -35,12 +35,6 @@ extern I_List<i_string> binlog_do_db, binlog_ignore_db;
 extern int max_binlog_dump_events;
 extern my_bool opt_sporadic_binlog_dump_fail;
 
-#define KICK_SLAVE(thd) do {                                            \
-                          pthread_mutex_lock(&(thd)->LOCK_delete);      \
-                          (thd)->awake(THD::NOT_KILLED);                \
-                          pthread_mutex_unlock(&(thd)->LOCK_delete);    \
-                        } while(0)
-
 int start_slave(THD* thd, MASTER_INFO* mi, bool net_report);
 int stop_slave(THD* thd, MASTER_INFO* mi, bool net_report);
 bool change_master(THD* thd, MASTER_INFO* mi);