diff --git a/sys/kern/kern_condvar.c b/sys/kern/kern_condvar.c
--- a/sys/kern/kern_condvar.c
+++ b/sys/kern/kern_condvar.c
@@ -43,8 +43,9 @@
 #include <sys/sleepqueue.h>
 #include <sys/resourcevar.h>
 #ifdef KTRACE
-#include <sys/uio.h>
 #include <sys/ktrace.h>
+#include <sys/uio.h>
+#include <sys/user.h>
 #endif
 
 /*
@@ -107,6 +108,9 @@
 _cv_wait(struct cv *cvp, struct lock_object *lock)
 {
 	WITNESS_SAVE_DECL(lock_witness);
+#ifdef KTRACE
+	char wmesg[WMESGLEN + 1];
+#endif
 	struct lock_class *class;
 	struct thread *td;
 	uintptr_t lock_state;
@@ -114,8 +118,12 @@
 	td = curthread;
 	lock_state = 0;
 #ifdef KTRACE
-	if (KTRPOINT(td, KTR_CSW))
-		ktrcsw(1, 0, cv_wmesg(cvp));
+	if (KTRPOINT(td, KTR_CSW)) {
+		strlcpy(wmesg, cv_wmesg(cvp), sizeof(wmesg));
+		ktrcsw(1, 0, wmesg);
+	} else {
+		wmesg[0] = '\0';
+	}
 #endif
 	CV_ASSERT(cvp, lock, td);
 	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
@@ -145,7 +153,7 @@
 
 #ifdef KTRACE
 	if (KTRPOINT(td, KTR_CSW))
-		ktrcsw(0, 0, cv_wmesg(cvp));
+		ktrcsw(0, 0, wmesg);
 #endif
 	PICKUP_GIANT();
 	if (lock != &Giant.lock_object) {