From cb1c79008ee951895ac07a66dff92c6e97ec8066 Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Thu, 19 Oct 2017 00:31:00 +0000
Subject: [PATCH] sysvsem: check if semu_list has anything on it before
 grabbing the lock

This should get a process-specific support instead.

MFC after:	1 week
---
 sys/kern/sysv_sem.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys/kern/sysv_sem.c b/sys/kern/sysv_sem.c
index 60688960e24..116fc437e4b 100644
--- a/sys/kern/sysv_sem.c
+++ b/sys/kern/sysv_sem.c
@@ -1412,6 +1412,8 @@ semexit_myhook(void *arg, struct proc *p)
 	 * Go through the chain of undo vectors looking for one
 	 * associated with this process.
 	 */
+	if (LIST_EMPTY(&semu_list))
+		return;
 	SEMUNDO_LOCK();
 	LIST_FOREACH(suptr, &semu_list, un_next) {
 		if (suptr->un_proc == p)