row0mysql.c, row0mysql.h, ha_innodb.cc:

  Inside LOCK TABLES, use either LOCK_S or LOCK_X in locking reads; an improvent over the previous patch

innobase/include/row0mysql.h

@@ -507,6 +507,9 @@ struct row_prebuilt_struct {
 	dtuple_t*	clust_ref;	/* prebuilt dtuple used in
 					sel/upd/del */
 	ulint		select_lock_type;/* LOCK_NONE, LOCK_S, or LOCK_X */
+	ulint		stored_select_lock_type;/* inside LOCK TABLES, either
+					LOCK_S or LOCK_X depending on the lock
+					type */
 	ulint		mysql_row_len;	/* length in bytes of a row in the
 					MySQL format */
 	ulint		n_rows_fetched;	/* number of rows fetched after

innobase/row/row0mysql.c

@@ -380,6 +380,7 @@ row_create_prebuilt(
   	prebuilt->clust_pcur = btr_pcur_create_for_mysql();
 
 	prebuilt->select_lock_type = LOCK_NONE;
+	prebuilt->stored_select_lock_type = 99999999;
 
 	prebuilt->sel_graph = NULL;
 

sql/ha_innodb.cc

@@ -4505,16 +4505,38 @@ ha_innobase::start_stmt(
 	  
 	        prebuilt->select_lock_type = LOCK_X;
 	} else {
-		/* For other than temporary tables, we obtain
-		no lock for consistent read (plain SELECT), and
-		an exclusive lock for SELECT ... FOR UPDATE or
-		SELECT ... LOCK IN SHARE MODE. */
-
-		prebuilt->select_lock_type =
-			thd->lex.sql_command == SQLCOM_SELECT
-			&& thd->lex.lock_option == TL_READ
-			? LOCK_NONE
-			: LOCK_X;
+		/* When we first come here after LOCK TABLES,
+		select_lock_type is set to LOCK_S or LOCK_X. Store the value
+		in case we run also consistent reads and need to restore the
+		value later. */
+
+		if (prebuilt->select_lock_type != LOCK_NONE) {
+			prebuilt->stored_select_lock_type =
+					prebuilt->select_lock_type;
+		}
+
+		if (prebuilt->stored_select_lock_type != LOCK_S
+		    && prebuilt->stored_select_lock_type != LOCK_X) {
+			fprintf(stderr,
+"InnoDB: Error: select_lock_type is %lu inside ::start_stmt()!\n",
+			prebuilt->stored_select_lock_type);
+
+			ut_error;
+		}
+
+		if (thd->lex.sql_command == SQLCOM_SELECT
+					&& thd->lex.lock_option == TL_READ) {
+	
+			/* For other than temporary tables, we obtain
+			no lock for consistent read (plain SELECT) */
+
+			prebuilt->select_lock_type = LOCK_NONE;
+		} else {
+			/* Not a consistent read: restore the
+			select_lock_type value */
+			prebuilt->select_lock_type =
+				prebuilt->stored_select_lock_type;
+		}
 	}
 	
 	/* Set the MySQL flag to mark that there is an active transaction */