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, 5 insertions, 4 deletions

diff --git a/mysys/testhash.c b/mysys/testhash.c
index 72badffdbcd..d15016113cd 100644
--- a/mysys/testhash.c
+++ b/mysys/testhash.c
@@ -74,7 +74,7 @@ static int do_test()
   bzero((char*) key1,sizeof(key1[0])*1000);
 
   printf("- Creating hash\n");
-  if (hash_init(&hash,recant/2,0,6,0,free_record,0))
+  if (hash_init(&hash, default_charset_info, recant/2, 0, 6, 0, free_record, 0))
     goto err;
   printf("- Writing records:\n");
 
@@ -172,15 +172,16 @@ static int do_test()
       break;
   if (key1[j] > 1)
   {
+    HASH_SEARCH_STATE state;
     printf("- Testing identical read\n");
     sprintf(key,"%6d",j);
     pos=1;
-    if (!(recpos=hash_search(&hash,key,0)))
+    if (!(recpos= hash_first(&hash, key, 0, &state)))
     {
       printf("can't find key1: \"%s\"\n",key);
       goto err;
     }
-    while (hash_next(&hash,key,0) && pos < (ulong) (key1[j]+10))
+    while (hash_next(&hash, key, 0, &state) && pos < (ulong) (key1[j]+10))
       pos++;
     if (pos != (ulong) key1[j])
     {
@@ -189,7 +190,7 @@ static int do_test()
     }
   }
   printf("- Creating output heap-file 2\n");
-  if (hash_init(&hash2,hash.records,0,0,hash2_key,free_record,0))
+  if (hash_init(&hash2, default_charset_info, hash.records, 0, 0, hash2_key, free_record,0))
     goto err;
 
   printf("- Copying and removing records\n");