BUG# 20798617 - MYSQL CALLS EXIT(MYSQLD_ABORT_EXIT) WITHOUT

                SHUTTING DOWN INNODB.

The test innodb.log_file can occasionally crash due to an error
in the startup error handling. In test step 12 of the innodb.
log_file cause mysqld startup to abort by calling exit.Thus
InnoDB is not shutdown properly with some InnoDB threads being
active causing sporadic test case failure.
The fix is to exit via unireg_abort which does InnoDB to gracefully
shutdown. Also move the start of signal handler thread before bootstrap
in the initialization sequence. Terminate signal handler thread when
SIGTERM and SIGQUIT irrespective of whether abort_loop is set or unset.

Author: thayumanavar77

sql/mysqld.cc

@@ -2199,7 +2199,7 @@ static void start_signal_handler()
 }
 
 
-/** This threads handles all signals and alarms. */
+/** This thread handles SIGTERM, SIGQUIT and SIGHUP signals. */
 /* ARGSUSED */
 extern "C" void *signal_hand(void *arg __attribute__((unused)))
 {
@@ -2276,10 +2276,10 @@ extern "C" void *signal_hand(void *arg __attribute__((unused)))
         mysql_mutex_unlock(&LOCK_socket_listener_active);
 
         close_connections();
-        my_thread_end();
-        my_thread_exit(0);
-        return NULL;  // Avoid compiler warnings
       }
+      my_thread_end();
+      my_thread_exit(0);
+      return NULL;  // Avoid compiler warnings
       break;
     case SIGHUP:
       if (!abort_loop)
@@ -4878,16 +4878,8 @@ int mysqld_main(int argc, char **argv)
   my_str_free= &my_str_free_mysqld;
   my_str_realloc= &my_str_realloc_mysqld;
 
-  /*
-    init signals & alarm
-    After this we can't quit by a simple unireg_abort
-  */
   error_handler_hook= my_message_sql;
 
-#ifndef _WIN32
-  start_signal_handler();
-#endif
-
   /* Save pid of this process in a file */
   if (!opt_bootstrap)
     create_pid_file();
@@ -4902,18 +4894,15 @@ int mysqld_main(int argc, char **argv)
   {
     abort_loop= true;
 
-#ifndef _WIN32
-    (void) pthread_kill(signal_thread_id.thread, SIGTERM);
-#endif
-
     delete_pid_file(MYF(MY_WME));
 
     if (mysqld_socket_acceptor != NULL)
     {
       delete mysqld_socket_acceptor;
       mysqld_socket_acceptor= NULL;
     }
-    exit(MYSQLD_ABORT_EXIT);
+
+    unireg_abort(MYSQLD_ABORT_EXIT);
   }
 
   if (!opt_noacl)
@@ -4972,6 +4961,11 @@ int mysqld_main(int argc, char **argv)
   if (Events::init(opt_noacl || opt_bootstrap))
     unireg_abort(MYSQLD_ABORT_EXIT);
 
+#ifndef _WIN32
+  //  Start signal handler thread.
+  start_signal_handler();
+#endif
+
   if (opt_bootstrap)
   {
     start_processing_signals();