Fix for bug #26380: LOCK TABLES + FLUSH LOGS causes deadlock

The log tables are by nature PERFORMANCE_SCHEMA tables,
which should not be affected by SET GLOBAL READ_ONLY or FLUSH TABLES
WITH READ LOCK.

The implementation of FLUSH TABLES WITH READ LOCK already ignored log tables.
Now with this patch, the implementation of LOCK TABLE also ignore a
global read lock for log tables, which was the missing symmetry.


mysql-test/r/flush.result:
  Fix for bug #26380: LOCK TABLES + FLUSH LOGS causes deadlock
    - test result.
mysql-test/t/flush.test:
  Fix for bug #26380: LOCK TABLES + FLUSH LOGS causes deadlock
    - test case.
sql/lock.cc:
  Fix for bug #26380: LOCK TABLES + FLUSH LOGS causes deadlock
    - logger.is_privileged_thread() used.
sql/log.h:
  Fix for bug #26380: LOCK TABLES + FLUSH LOGS causes deadlock
    - LOGGER::is_privileged_thread() introduced that returns TRUE if a given thread 
      is either a general_log or a slow_log or a privileged thread.
sql/sql_base.cc:
  Fix for bug #26380: LOCK TABLES + FLUSH LOGS causes deadlock
    - pass MYSQL_LOCK_IGNORE_GLOBAL_READ_LOCK to the mysql_lock_tables() in case of 
      call from a logger in order not to honor the GLOBAL READ LOCK 
      and to avoid possible deadlocks.

1 files changed, 25 insertions, 1 deletions

diff --git a/mysql-test/t/flush.test b/mysql-test/t/flush.test
index 3a4f2f2f5f2..d58d038c3ea 100644
--- a/mysql-test/t/flush.test
+++ b/mysql-test/t/flush.test
@@ -133,4 +133,28 @@ disconnect con3;
 connection default;
 drop table t1, t2;
 
-# End of 5.0 tests
+--echo End of 5.0 tests
+
+#
+# Bug #26380: LOCK TABLES + FLUSH LOGS causes deadlock
+#
+set @old_general_log= @@general_log;
+set @old_read_only= @@read_only;
+set global general_log= on;
+
+flush tables with read lock;
+flush logs;
+unlock tables;
+
+set global read_only=1;
+flush logs;
+unlock tables;
+
+flush tables with read lock;
+flush logs;
+unlock tables;
+
+set global general_log= @old_general_log;
+set global read_only= @old_read_only;
+
+--echo End of 5.1 tests