Bug#30294 blackhole engine causes 100% with 2 alter table statements running

Implement neccessary shared lock structure for table locks.
This is the backport of bug26241 fix.


sql/ha_blackhole.cc:
  Implement neccessary shared lock structure for table locks.
sql/ha_blackhole.h:
  Declare shared structure for table locks
sql/handler.cc:
  added BLACKHOLE_DB case

1 files changed, 16 insertions, 2 deletions

diff --git a/sql/ha_blackhole.h b/sql/ha_blackhole.h
index 4dcb37c637d..45ed0351457 100644
--- a/sql/ha_blackhole.h
+++ b/sql/ha_blackhole.h
@@ -17,6 +17,18 @@
 #pragma interface			/* gcc class implementation */
 #endif
 
+
+/*
+  Shared structure for correct LOCK operation
+*/
+struct st_blackhole_share {
+  THR_LOCK lock;
+  uint use_count;
+  uint table_name_length;
+  char table_name[1];
+};
+
+
 /*
   Class definition for the blackhole storage engine
   "Dumbest named feature ever"
@@ -24,7 +36,7 @@
 class ha_blackhole: public handler
 {
   THR_LOCK_DATA lock;      /* MySQL lock */
-  THR_LOCK thr_lock;
+  st_blackhole_share *share;
 
 public:
   ha_blackhole(TABLE *table_arg);
@@ -76,10 +88,12 @@ public:
   void position(const byte *record);
   int info(uint flag);
   int external_lock(THD *thd, int lock_type);
-  uint lock_count(void) const;
   int create(const char *name, TABLE *table_arg,
              HA_CREATE_INFO *create_info);
   THR_LOCK_DATA **store_lock(THD *thd,
                              THR_LOCK_DATA **to,
                              enum thr_lock_type lock_type);
 };
+
+bool blackhole_db_init(void);
+bool blackhole_db_end(void);