add comment for BUG 672

sql/sql_parse.cc

@@ -1160,7 +1160,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
       pos = uint4korr(packet);
       flags = uint2korr(packet + 4);
       thd->server_id=0; /* avoid suicide */
-      if ((slave_server_id= uint4korr(packet+6)))
+      if ((slave_server_id= uint4korr(packet+6))) // mysqlbinlog.server_id==0
 	kill_zombie_dump_threads(slave_server_id);
       thd->server_id = slave_server_id;
       mysql_binlog_send(thd, thd->strdup(packet + 10), (my_off_t) pos, flags);

sql/sql_repl.cc

@@ -522,7 +522,7 @@ Increase max_allowed_packet on master";
 
 	case LOG_READ_EOF:
 	  DBUG_PRINT("wait",("waiting for data in binary log"));
-	  if (thd->server_id==0)
+	  if (thd->server_id==0) // for mysqlbinlog (mysqlbinlog.server_id==0)
 	  {
 	    pthread_mutex_unlock(log_lock);
 	    goto end;