ha_innodb.h, ha_innodb.cc:

  Fix bug #10359 : the critical AUTO-INC bug in InnoDB; since reading of the auto-inc counter in an INSERT was not protected by the AUTO-INC table lock of InnoDB, two inserted rows could get the same value for the auto-inc counter, leading to a duplicate key error

sql/ha_innodb.cc

@@ -3170,12 +3170,28 @@ no_commit:
 			prebuilt->sql_stat_start = TRUE;
 		}
 
-		/*
-                  We must use the handler code to update the auto-increment
-                  value to be sure that increment it correctly.
-                */
+		/* We have to use the transactional lock mechanism on the
+		auto-inc counter of the table to ensure that replication and
+		roll-forward of the binlog exactly imitates also the given
+		auto-inc values. The lock is released at each SQL statement's
+		end. This lock also prevents a race where two threads would
+		call ::get_auto_increment() simultaneously. */
+
+		error = row_lock_table_autoinc_for_mysql(prebuilt);
+
+		if (error != DB_SUCCESS) {
+			/* Deadlock or lock wait timeout */
+
+			error = convert_error_code_to_mysql(error, user_thd);
+
+			goto func_exit;
+		}
+
+		/* We must use the handler code to update the auto-increment
+                value to be sure that we increment it correctly. */
+
     		update_auto_increment();
-                auto_inc_used= 1;
+                auto_inc_used = 1;
 
 	}
 
@@ -3198,24 +3214,15 @@ no_commit:
           	auto_inc = table->next_number_field->val_int();
 
           	if (auto_inc != 0) {
-			/* This call will calculate the max of the current
-			value and the value supplied by the user and
-			update the counter accordingly */
-
-			/* We have to use the transactional lock mechanism
-			on the auto-inc counter of the table to ensure
-			that replication and roll-forward of the binlog
-			exactly imitates also the given auto-inc values.
-			The lock is released at each SQL statement's
-			end. */
-
-            		error = row_lock_table_autoinc_for_mysql(prebuilt);
+			/* This call will update the counter according to the
+			value that was inserted in the table */
 
             		if (error != DB_SUCCESS) {
               			error = convert_error_code_to_mysql(error,
 								user_thd);
               			goto func_exit;
             		}
+
             		dict_table_autoinc_update(prebuilt->table, auto_inc);
           	}
         }
@@ -5795,7 +5802,6 @@ ha_innobase::start_stmt(
 	    	read_view_close_for_mysql(trx);
 	}
 
-	auto_inc_counter_for_this_stat = 0;
 	prebuilt->sql_stat_start = TRUE;
 	prebuilt->hint_need_to_fetch_extra_cols = 0;
 	prebuilt->read_just_key = 0;
@@ -5985,7 +5991,7 @@ ha_innobase::external_lock(
 
 	trx->n_mysql_tables_in_use--;
 	prebuilt->mysql_has_locked = FALSE;
-	auto_inc_counter_for_this_stat = 0;
+
 	if (trx->n_lock_table_exp) {
 		row_unlock_tables_for_mysql(trx);
 	}
@@ -6505,7 +6511,7 @@ ha_innobase::store_lock(
 /***********************************************************************
 This function initializes the auto-inc counter if it has not been
 initialized yet. This function does not change the value of the auto-inc
-counter if it already has been initialized. In paramete ret returns
+counter if it already has been initialized. In parameter ret returns
 the value of the auto-inc counter. */
 
 int
@@ -6624,7 +6630,14 @@ ha_innobase::get_auto_increment()
 	error = innobase_read_and_init_auto_inc(&nr);
 
 	if (error) {
+		/* This should never happen in the current (5.0.6) code, since
+		we call this function only after the counter has been
+		initialized. */
 	
+		ut_print_timestamp(stderr);
+		fprintf(stderr,
+		"  InnoDB: Error: error %lu in ::get_auto_increment()\n",
+						(ulong)error);
           	return(~(ulonglong) 0);
 	}
 

sql/ha_innodb.h

@@ -70,7 +70,6 @@ class ha_innobase: public handler
 					ROW_SEL_EXACT, ROW_SEL_EXACT_PREFIX,
 					or undefined */
 	uint		num_write_row;	/* number of write_row() calls */
-	longlong	auto_inc_counter_for_this_stat;
 	ulong max_supported_row_length(const byte *buf);
 
 	uint store_key_val_for_row(uint keynr, char* buff, uint buff_len,