From a2e850b8296cf8fb6bf1f60b47605a14657333dd Mon Sep 17 00:00:00 2001
From: bluhm <bluhm@openbsd.org>
Date: Fri, 28 Apr 2023 12:53:42 +0000
Subject: [PATCH] Add a membar_consumer() for the taskq_create() in sosplice().
  Membar producer and consumer must come in pair and the latter was missing.
 Also move the code a bit to make clear which check is needed for what. OK
 mvs@

---
 sys/kern/uipc_socket.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index 3c8d08b774a..0c3b5bb52a5 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uipc_socket.c,v 1.302 2023/04/24 09:20:09 mvs Exp $	*/
+/*	$OpenBSD: uipc_socket.c,v 1.303 2023/04/28 12:53:42 bluhm Exp $	*/
 /*	$NetBSD: uipc_socket.c,v 1.21 1996/02/04 02:17:52 christos Exp $	*/
 
 /*
@@ -1258,14 +1258,19 @@ sosplice(struct socket *so, int fd, off_t max, struct timeval *tv)
 		if (sosplice_taskq == NULL) {
 			tq = taskq_create("sosplice", 1, IPL_SOFTNET,
 			    TASKQ_MPSAFE);
+			if (tq == NULL) {
+				rw_exit_write(&sosplice_lock);
+				return (ENOMEM);
+			}
 			/* Ensure the taskq is fully visible to other CPUs. */
 			membar_producer();
 			sosplice_taskq = tq;
 		}
 		rw_exit_write(&sosplice_lock);
+	} else {
+		/* Ensure the taskq is fully visible on this CPU. */
+		membar_consumer();
 	}
-	if (sosplice_taskq == NULL)
-		return (ENOMEM);
 
 	if ((so->so_proto->pr_flags & PR_SPLICE) == 0)
 		return (EPROTONOSUPPORT);
-- 
2.20.1