From 7fab871d8c286b59928cba454a398fc8f65d5ab6 Mon Sep 17 00:00:00 2001
From: David Xu <davidxu@FreeBSD.org>
Date: Mon, 17 Dec 2007 08:09:37 +0000
Subject: [PATCH] Check NULL pointer.

---
 sys/kern/kern_umtx.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c
index 0857366dbb1f..6fa6beffc5aa 100644
--- a/sys/kern/kern_umtx.c
+++ b/sys/kern/kern_umtx.c
@@ -1407,8 +1407,17 @@ umtx_pi_adjust_locked(struct thread *td, u_char oldpri)
 void
 umtx_pi_adjust(struct thread *td, u_char oldpri)
 {
+	struct umtx_q *uq;
+	struct umtx_pi *pi;
+
+	uq = td->td_umtxq;
 	mtx_lock_spin(&umtx_lock);
-	umtx_pi_adjust_locked(td, oldpri);
+	/*
+	 * Pick up the lock that td is blocked on.
+	 */
+	pi = uq->uq_pi_blocked;
+	if (pi != NULL)
+		umtx_pi_adjust_locked(td, oldpri);
 	mtx_unlock_spin(&umtx_lock);
 }