diff --git a/include/linux/pid.h b/include/linux/pid.h
new file mode 100644
index 0000000..5b2fcb1
--- /dev/null
+++ b/include/linux/pid.h
@@ -0,0 +1,55 @@
+#ifndef _LINUX_PID_H
+#define _LINUX_PID_H
+
+enum pid_type
+{
+	PIDTYPE_PID,
+	PIDTYPE_TGID,
+	PIDTYPE_PGID,
+	PIDTYPE_SID,
+	PIDTYPE_MAX
+};
+
+struct pid
+{
+	/* Try to keep pid_chain in the same cacheline as nr for find_pid */
+	int nr;
+	struct hlist_node pid_chain;
+	/* list of pids with the same nr, only one of them is in the hash */
+	struct list_head pid_list;
+};
+
+#define pid_task(elem, type) \
+	list_entry(elem, struct task_struct, pids[type].pid_list)
+
+/*
+ * attach_pid() and detach_pid() must be called with the tasklist_lock
+ * write-held.
+ */
+extern int FASTCALL(attach_pid(struct task_struct *task, enum pid_type type, int nr));
+
+extern void FASTCALL(detach_pid(struct task_struct *task, enum pid_type));
+
+/*
+ * look up a PID in the hash table. Must be called with the tasklist_lock
+ * held.
+ */
+extern struct pid *FASTCALL(find_pid(enum pid_type, int));
+
+extern int alloc_pidmap(void);
+extern void FASTCALL(free_pidmap(int));
+extern void switch_exec_pids(struct task_struct *leader, struct task_struct *thread);
+
+#define do_each_task_pid(who, type, task)				\
+	if ((task = find_task_by_pid_type(type, who))) {		\
+		prefetch((task)->pids[type].pid_list.next);		\
+		do {
+
+#define while_each_task_pid(who, type, task)				\
+		} while (task = pid_task((task)->pids[type].pid_list.next,\
+						type),			\
+			prefetch((task)->pids[type].pid_list.next),	\
+			hlist_unhashed(&(task)->pids[type].pid_chain));	\
+	}								\
+
+#endif /* _LINUX_PID_H */