Making FLUSH TABLES WITH READ LOCK block COMMITs of existing transactions,

in a deadlock-free manner. This splits locking the global read lock in two steps.
This fixes a consequence of this bug, known as:
BUG#4953 'mysqldump --master-data may report incorrect binlog position if using InnoDB'
And a test.


sql/handler.cc:
  making COMMIT wait if FLUSH TABLES WITH READ LOCK happened.
sql/lock.cc:
  an additional stage so that FLUSH TABLES WITH READ LOCK blocks COMMIT:
  make_global_read_lock_block_commit():
  taking the global read lock is TWO steps (2nd step is optional; without
  it, COMMIT of existing transactions will be allowed):
  lock_global_read_lock() THEN make_global_read_lock_block_commit().
sql/mysql_priv.h:
  new argument to wait_if_global_read_lock()
sql/sql_class.h:
  THD::global_read_lock now an uint to reflect the 2 steps of global read lock (does not block COMMIT / does)
sql/sql_db.cc:
  update for new prototype
sql/sql_parse.cc:
  implementing the two steps of global read lock so that FLUSH TABLES WITH READ LOCK can block COMMIT without deadlocking with COMMITs.

1 files changed, 2 insertions, 2 deletions

diff --git a/sql/sql_class.h b/sql/sql_class.h
index 3c968c6a8ae..30947041b7d 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -478,7 +478,7 @@ public:
   ulong	     rand_saved_seed1, rand_saved_seed2;
   long	     dbug_thread_id;
   pthread_t  real_id;
-  uint	     current_tablenr,tmp_table,cond_count;
+  uint	     current_tablenr,tmp_table,cond_count,global_read_lock;
   uint	     server_status,open_options,system_thread;
   uint32     query_length;
   uint32     db_length;
@@ -489,7 +489,7 @@ public:
   bool	     set_query_id,locked,count_cuted_fields,some_tables_deleted;
   bool	     no_errors, allow_sum_func, password, fatal_error;
   bool	     query_start_used,last_insert_id_used,insert_id_used,rand_used;
-  bool	     in_lock_tables,global_read_lock;
+  bool	     in_lock_tables;
   bool       query_error, bootstrap, cleanup_done;
   bool	     safe_to_cache_query;
   bool	     volatile killed;