From 84f2a8a4b4a8267d50bf3fe4c1af50b5f7d5ece3 Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Sat, 13 Jan 2018 00:05:31 +0000
Subject: [PATCH] rwlock: try regular read unlock even in the hard path

Saves on turnstile trips if the lock got more readers.
---
 sys/kern/kern_rwlock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sys/kern/kern_rwlock.c b/sys/kern/kern_rwlock.c
index 025ced411fd0..7459cde5e283 100644
--- a/sys/kern/kern_rwlock.c
+++ b/sys/kern/kern_rwlock.c
@@ -771,9 +771,9 @@ __rw_runlock_hard(struct rwlock *rw, struct thread *td, uintptr_t v
 		turnstile_chain_lock(&rw->lock_object);
 		v = RW_READ_VALUE(rw);
 retry_ts:
-		if (__predict_false(RW_READERS(v) > 1)) {
+		if (__rw_runlock_try(rw, td, &v)) {
 			turnstile_chain_unlock(&rw->lock_object);
-			continue;
+			break;
 		}
 
 		v &= (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);