commit 904323885a4ef72dcf0fe743cf086a2e9e9a09d8
Author: Mateusz Guzik <mjguzik@gmail.com>
Date:   Thu Aug 6 17:52:23 2020 -0400

    meh fixup

diff --git a/sys/kern/kern_obm.c b/sys/kern/kern_obm.c
index d999ed0e5fd6..9f98971d1128 100644
--- a/sys/kern/kern_obm.c
+++ b/sys/kern/kern_obm.c
@@ -69,41 +69,41 @@ obm_init(obm_lock_t *obm)
 }
 
 void
-obm_lock_slow(obm_lock_t *obm, struct lock_object *lo)
+obm_lock_slow(obm_lock_t *obm, struct lock_object *lo, uint8_t v)
 {
 	struct turnstile *ts;
 	struct lock_delay_arg lda;
-	uint8_t v;
 
 #ifdef OBM_DEBUG
 	atomic_add_long(&obm_slow_lock, 1);
 #endif
 	lock_delay_arg_init(&lda, &locks_delay);
-	lock_delay(&lda);
 	for (;;) {
-		v = atomic_load_8(&obm->lk);
 		if (v == OBM_UNLOCKED) {
 			if (atomic_fcmpset_acq_char(&obm->lk, &v, OBM_LOCKED) != 0)
 				break;
+			continue;
+		}
+
+		if ((v & OBM_CONTESTED) == 0) {
 			lock_delay(&lda);
+			v = atomic_load_8(&obm->lk);
 			continue;
 		}
 
 		ts = turnstile_trywait(lo);
 		v = atomic_load_8(&obm->lk);
+retry_ts:
 		if (v == OBM_UNLOCKED) {
 			turnstile_cancel(ts);
-			if (atomic_fcmpset_acq_8(&obm->lk, &v, OBM_LOCKED) != 0)
-				break;
-			lock_delay(&lda);
 			continue;
 		}
 		if ((v & OBM_CONTESTED) == 0 &&
 		    atomic_fcmpset_8(&obm->lk, &v, v | OBM_CONTESTED) == 0) {
-			turnstile_cancel(ts);
-			continue;
+			goto retry_ts;
 		}
 		turnstile_wait(ts, NULL, TS_SHARED_QUEUE);
+		v = atomic_load_8(&obm->lk);
 	}
 	TD_LOCKS_INC(curthread);
 }
diff --git a/sys/sys/obm.h b/sys/sys/obm.h
index d14039358ec2..2ccfe34945d3 100644
--- a/sys/sys/obm.h
+++ b/sys/sys/obm.h
@@ -46,7 +46,7 @@
 
 void	obm_init_lo(struct lock_object *lo, const char *name);
 void	obm_init(obm_lock_t *obm);
-void	obm_lock_slow(obm_lock_t *obm, struct lock_object *lo);
+void	obm_lock_slow(obm_lock_t *obm, struct lock_object *lo, uint8_t v);
 void	obm_unlock_slow(obm_lock_t *obm, struct lock_object *lo);
 
 __used static void
@@ -81,7 +81,7 @@ obm_lock(obm_lock_t *obm, struct lock_object *lo)
 	} else {
 		MPASS(v == OBM_LOCKED || v == (OBM_LOCKED | OBM_CONTESTED) ||
 		    v == OBM_UNLOCKED);
-		obm_lock_slow(obm, lo);
+		obm_lock_slow(obm, lo, v);
 	}
 }