From e8a5fa7b28f13aaabdc4ee58078d26f364a199b9 Mon Sep 17 00:00:00 2001
From: mpi <mpi@openbsd.org>
Date: Mon, 18 Dec 2017 10:05:43 +0000
Subject: [PATCH] Make rw_exit() always succeed after a panic.

Prevents a deadlock in if_downall() when rw_enter() succeed without
really grabbing the lock.

Reported by and ok phessler@
---
 sys/kern/kern_rwlock.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sys/kern/kern_rwlock.c b/sys/kern/kern_rwlock.c
index 399c352f396..88228a224a1 100644
--- a/sys/kern/kern_rwlock.c
+++ b/sys/kern/kern_rwlock.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_rwlock.c,v 1.32 2017/10/24 08:53:15 mpi Exp $	*/
+/*	$OpenBSD: kern_rwlock.c,v 1.33 2017/12/18 10:05:43 mpi Exp $	*/
 
 /*
  * Copyright (c) 2002, 2003 Artur Grabowski <art@openbsd.org>
@@ -287,6 +287,10 @@ _rw_exit(struct rwlock *rwl LOCK_FL_VARS)
 	int wrlock = owner & RWLOCK_WRLOCK;
 	unsigned long set;
 
+	/* Avoid deadlocks after panic */
+	if (panicstr)
+		return;
+
 	if (wrlock)
 		rw_assert_wrlock(rwl);
 	else
-- 
2.20.1