Add skeleton for perf_event_open.

kernel/process.c

@@ -96,6 +96,7 @@ init_process(struct process *proc, struct process *parent)
 	INIT_LIST_HEAD(&proc->ptraced_children_list);
 	mcs_rwlock_init(&proc->threads_lock);
 	mcs_rwlock_init(&proc->children_lock);
+	ihk_mc_spinlock_init(&proc->mckfd_lock);
 	waitq_init(&proc->waitpid_q);
 	ihk_atomic_set(&proc->refcount, 2);
 }