Module Name: src
Committed By: martin
Date: Mon Jul 31 14:48:07 UTC 2023
Modified Files:
src/sys/kern [netbsd-9]: kern_rwlock.c
Log Message:
Pull up following revision(s) (requested by riastradh in ticket #1678):
sys/kern/kern_rwlock.c: revision 1.68 (patch)
rwlock(9): Fix membars.
rw_downgrade must be a release operation, and rw_tryupgrade must be
an acquire operation. membar_producer is not enough -- need to use
membar_release and membar_acquire.
Discussed on tech-kern:
https://mail-index.netbsd.org/tech-kern/2023/02/22/msg028726.html
To generate a diff of this commit:
cvs rdiff -u -r1.54.2.1 -r1.54.2.2 src/sys/kern/kern_rwlock.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/kern_rwlock.c
diff -u src/sys/kern/kern_rwlock.c:1.54.2.1 src/sys/kern/kern_rwlock.c:1.54.2.2
--- src/sys/kern/kern_rwlock.c:1.54.2.1 Mon Jul 31 14:40:04 2023
+++ src/sys/kern/kern_rwlock.c Mon Jul 31 14:48:07 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_rwlock.c,v 1.54.2.1 2023/07/31 14:40:04 martin Exp $ */
+/* $NetBSD: kern_rwlock.c,v 1.54.2.2 2023/07/31 14:48:07 martin Exp $ */
/*-
* Copyright (c) 2002, 2006, 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -38,7 +38,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rwlock.c,v 1.54.2.1 2023/07/31 14:40:04 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rwlock.c,v 1.54.2.2 2023/07/31 14:48:07 martin Exp $");
#define __RWLOCK_PRIVATE
@@ -594,8 +594,7 @@ rw_downgrade(krwlock_t *rw)
__USE(curthread);
#endif
-
- membar_producer();
+ membar_exit();
owner = rw->rw_owner;
if ((owner & RW_HAS_WAITERS) == 0) {
/*
@@ -691,7 +690,7 @@ rw_tryupgrade(krwlock_t *rw)
newown = curthread | RW_WRITE_LOCKED | (owner & ~RW_THREAD);
next = rw_cas(rw, owner, newown);
if (__predict_true(next == owner)) {
- membar_producer();
+ membar_enter(); /* XXX membar_acquire */
break;
}
}
