diff --git a/kernel/process.c b/kernel/process.c
index 3dc4214a..a3efedce 100644
--- a/kernel/process.c
+++ b/kernel/process.c
@@ -17,7 +17,7 @@
 #endif
 
 
-#define USER_STACK_NR_PAGES 512
+#define USER_STACK_NR_PAGES 4096
 #define KERNEL_STACK_NR_PAGES 16
 
 extern long do_arch_prctl(unsigned long code, unsigned long address);
@@ -26,6 +26,9 @@ void init_process_vm(struct process_vm *vm)
 {
 	int i;
 
+	aal_mc_spinlock_init(&vm->memory_range_lock);
+	aal_mc_spinlock_init(&vm->page_table_lock);
+
 	aal_atomic_set(&vm->refcount, 1);
 	INIT_LIST_HEAD(&vm->vm_range_list);
 	vm->page_table = aal_mc_pt_create();