A fix for Bug#7209 "Client error with "Access Denied" on updates

when high concurrency": remove HASH::current_record and make it
an external search parameter, so that it can not be the cause of a 
race condition under high concurrent load.
The bug was in a race condition in table_hash_search,
when column_priv_hash.current_record was overwritten simultaneously
by multiple threads, causing the search for a suitable grant record
to fail.
No test case as the bug is repeatable only under concurrent load.


include/hash.h:
  - remove current_record from HASH, instead modify hash_first,
  hash_next to accept HASH_SEARCH_STATE as an IN/OUT parameter
mysys/hash.c:
  - remove HASH::current_record
  - change declarations of functions that use HASH in read-only mode
    to accept const HASH * instead of HASH *. 
  - implement hash_search; move the old implementation of hash_search
  to hash_first
mysys/testhash.c:
  - adjust the test case to changed function declarations
sql/lock.cc:
  - adjust to changed declarations of hash_search, hash_next
sql/sql_acl.cc:
  - adjust to changed declarations of hash_search, hash_next
sql/sql_base.cc:
  - adjust to changed declarations of hash_search, hash_nex
sql/sql_cache.cc:
  - adjust to a changed declaration of hash_replace

1 files changed, 10 insertions, 4 deletions

diff --git a/include/hash.h b/include/hash.h
index 9a6d91036e1..8f5ff21ae5e 100644
--- a/include/hash.h
+++ b/include/hash.h
@@ -33,7 +33,7 @@ typedef void (*hash_free_key)(void *);
 
 typedef struct st_hash {
   uint key_offset,key_length;		/* Length of key if const length */
-  uint records,blength,current_record;
+  uint records, blength;
   uint flags;
   DYNAMIC_ARRAY array;				/* Place for hash_keys */
   hash_get_key get_key;
@@ -41,6 +41,9 @@ typedef struct st_hash {
   CHARSET_INFO *charset;
 } HASH;
 
+/* A search iterator state */
+typedef uint HASH_SEARCH_STATE;
+
 #define hash_init(A,B,C,D,E,F,G,H) _hash_init(A,B,C,D,E,F,G, H CALLER_INFO)
 my_bool _hash_init(HASH *hash, CHARSET_INFO *charset,
 		   uint default_array_elements, uint key_offset,
@@ -49,12 +52,15 @@ my_bool _hash_init(HASH *hash, CHARSET_INFO *charset,
 void hash_free(HASH *tree);
 void my_hash_reset(HASH *hash);
 byte *hash_element(HASH *hash,uint idx);
-gptr hash_search(HASH *info,const byte *key,uint length);
-gptr hash_next(HASH *info,const byte *key,uint length);
+gptr hash_search(const HASH *info, const byte *key, uint length);
+gptr hash_first(const HASH *info, const byte *key, uint length,
+                HASH_SEARCH_STATE *state);
+gptr hash_next(const HASH *info, const byte *key, uint length,
+               HASH_SEARCH_STATE *state);
 my_bool my_hash_insert(HASH *info,const byte *data);
 my_bool hash_delete(HASH *hash,byte *record);
 my_bool hash_update(HASH *hash,byte *record,byte *old_key,uint old_key_length);
-void hash_replace(HASH *hash, uint idx, byte *new_row);
+void hash_replace(HASH *hash, HASH_SEARCH_STATE *state, byte *new_row);
 my_bool hash_check(HASH *hash);			/* Only in debug library */
 
 #define hash_clear(H) bzero((char*) (H),sizeof(*(H)))