--- sys/kern/subr_epoch.c.orig
+++ sys/kern/subr_epoch.c
@@ -325,24 +325,20 @@
 			 */
 			critical_enter();
 			thread_unlock(td);
-			owner = turnstile_lock(ts, &lock);
-			/*
-			 * The owner pointer indicates that the lock succeeded. Only
-			 * in case we hold the lock and the turnstile we locked is still
-			 * the one that curwaittd is blocked on can we continue. Otherwise
-			 * The turnstile pointer has been changed out from underneath
-			 * us, as in the case where the lock holder has signalled curwaittd,
-			 * and we need to continue.
-			 */
-			if (owner != NULL && ts == curwaittd->td_blocked) {
-				MPASS(TD_IS_INHIBITED(curwaittd) && TD_ON_LOCK(curwaittd));
-				critical_exit();
-				turnstile_wait(ts, owner, curwaittd->td_tsqueue);
-				counter_u64_add(turnstile_count, 1);
-				thread_lock(td);
-				return;
-			} else if (owner != NULL)
+
+			if (turnstile_lock(ts, &lock, &owner)) {
+				if (ts == curwaittd->td_blocked) {
+					MPASS(TD_IS_INHIBITED(curwaittd) &&
+					    TD_ON_LOCK(curwaittd));
+					critical_exit();
+					turnstile_wait(ts, owner,
+					    curwaittd->td_tsqueue);
+					counter_u64_add(turnstile_count, 1);
+					thread_lock(td);
+					return;
+				}
 				turnstile_unlock(ts, lock);
+			}
 			thread_lock(td);
 			critical_exit();
 			KASSERT(td->td_locks == locksheld,
--- sys/kern/subr_turnstile.c.orig
+++ sys/kern/subr_turnstile.c
@@ -566,14 +566,15 @@
 	return (ts);
 }
 
-struct thread *
-turnstile_lock(struct turnstile *ts, struct lock_object **lockp)
+bool
+turnstile_lock(struct turnstile *ts, struct lock_object **lockp,
+    struct thread **tdp)
 {
 	struct turnstile_chain *tc;
 	struct lock_object *lock;
 
 	if ((lock = ts->ts_lockobj) == NULL)
-		return (NULL);
+		return (false);
 	tc = TC_LOOKUP(lock);
 	mtx_lock_spin(&tc->tc_lock);
 	mtx_lock_spin(&ts->ts_lock);
@@ -580,10 +581,11 @@
 	if (__predict_false(lock != ts->ts_lockobj)) {
 		mtx_unlock_spin(&tc->tc_lock);
 		mtx_unlock_spin(&ts->ts_lock);
-		return (NULL);
+		return (false);
 	}
 	*lockp = lock;
-	return (ts->ts_owner);
+	*tdp = ts->ts_owner;
+	return (true);
 }
 
 void
--- sys/sys/turnstile.h.orig
+++ sys/sys/turnstile.h
@@ -100,7 +100,8 @@
 struct turnstile *turnstile_trywait(struct lock_object *);
 void	turnstile_unpend(struct turnstile *);
 void	turnstile_wait(struct turnstile *, struct thread *, int);
-struct thread *turnstile_lock(struct turnstile *, struct lock_object **);
+bool	turnstile_lock(struct turnstile *, struct lock_object **,
+	    struct thread **);
 void	turnstile_unlock(struct turnstile *, struct lock_object *);
 void	turnstile_assert(struct turnstile *);
 #endif	/* _KERNEL */