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.

1 files changed, 6 insertions, 0 deletions

diff --git a/sql/log.h b/sql/log.h
index 25bcbd6c62d..d92e0117bcc 100644
--- a/sql/log.h
+++ b/sql/log.h
@@ -600,6 +600,12 @@ public:
     else
       return NULL;
   }
+  bool is_privileged_thread(THD *thd)
+  {
+    return thd == get_general_log_thd() ||
+           thd == get_slow_log_thd() ||
+           thd == get_privileged_thread();
+  }
 };
 
 enum enum_binlog_format {