bug#21965 - replication

  fix deadlock if master switches log file in parallell with "show master logs"
  

sql/log.cc

@@ -409,13 +409,18 @@ shutdown the MySQL server and restart it.", log_name, errno);
 int MYSQL_LOG::get_current_log(LOG_INFO* linfo)
 {
   pthread_mutex_lock(&LOCK_log);
+  int ret = raw_get_current_log(linfo);
+  pthread_mutex_unlock(&LOCK_log);
+  return ret;
+}
+
+int MYSQL_LOG::raw_get_current_log(LOG_INFO* linfo)
+{
   strmake(linfo->log_file_name, log_file_name, sizeof(linfo->log_file_name)-1);
   linfo->pos = my_b_tell(&log_file);
-  pthread_mutex_unlock(&LOCK_log);
   return 0;
 }
 
-
 /*
   Move all data up in a file in an filename index file
 

sql/sql_class.h

@@ -177,6 +177,7 @@ public:
 		   bool need_mutex);
   int find_next_log(LOG_INFO* linfo, bool need_mutex);
   int get_current_log(LOG_INFO* linfo);
+  int raw_get_current_log(LOG_INFO* linfo);
   uint next_file_id();
   inline bool is_open() { return log_type != LOG_CLOSED; }
   inline char* get_index_fname() { return index_file_name;}

sql/sql_repl.cc

@@ -1359,10 +1359,14 @@ int show_binlogs(THD* thd)
                                            MYSQL_TYPE_LONGLONG));
   if (protocol->send_fields(&field_list, 1))
     DBUG_RETURN(1);
+  
+  pthread_mutex_lock(mysql_bin_log.get_log_lock());
   mysql_bin_log.lock_index();
   index_file=mysql_bin_log.get_index_file();
-
-  mysql_bin_log.get_current_log(&cur);
+  
+  mysql_bin_log.raw_get_current_log(&cur); // dont take mutex
+  pthread_mutex_unlock(mysql_bin_log.get_log_lock()); // lockdep, OK
+  
   cur_dir_len= dirname_length(cur.log_file_name);
 
   reinit_io_cache(index_file, READ_CACHE, (my_off_t) 0, 0, 0);