[src/trunk]: src/sys/kern Get rid of MUTEX_RECEIVE/MUTEX_GIVE.

[ad <ad%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/a9f2b44d619a
branches:  trunk
changeset: 846713:a9f2b44d619a
user:      ad <ad%NetBSD.org@localhost>
date:      Fri Nov 29 19:44:59 2019 +0000

description:
Get rid of MUTEX_RECEIVE/MUTEX_GIVE.

diffstat:

 sys/kern/kern_mutex.c |  21 ++++++++++++++++-----
 1 files changed, 16 insertions(+), 5 deletions(-)

diffs (63 lines):

diff -r 29b5ec86bc2e -r a9f2b44d619a sys/kern/kern_mutex.c
--- a/sys/kern/kern_mutex.c     Fri Nov 29 18:29:45 2019 +0000
+++ b/sys/kern/kern_mutex.c     Fri Nov 29 19:44:59 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_mutex.c,v 1.79 2019/05/09 05:00:31 ozaki-r Exp $  */
+/*     $NetBSD: kern_mutex.c,v 1.80 2019/11/29 19:44:59 ad Exp $       */
 
 /*-
  * Copyright (c) 2002, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -40,7 +40,7 @@
 #define        __MUTEX_PRIVATE
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.79 2019/05/09 05:00:31 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.80 2019/11/29 19:44:59 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -168,6 +168,17 @@
 } while (/* CONSTCOND */ 0)
 
 /*
+ * Memory barriers.
+ */
+#ifdef __HAVE_ATOMIC_AS_MEMBAR
+#define        MUTEX_MEMBAR_ENTER()
+#define        MUTEX_MEMBAR_EXIT()
+#else
+#define        MUTEX_MEMBAR_ENTER()            membar_enter()
+#define        MUTEX_MEMBAR_EXIT()             membar_exit()
+#endif
+
+/*
  * For architectures that provide 'simple' mutexes: they provide a
  * CAS function that is either MP-safe, or does not need to be MP
  * safe.  Adaptive mutexes on these architectures do not require an
@@ -225,7 +236,7 @@
        MUTEX_INHERITDEBUG(oldown, mtx->mtx_owner);
        MUTEX_INHERITDEBUG(newown, oldown);
        rv = MUTEX_CAS(&mtx->mtx_owner, oldown, newown);
-       MUTEX_RECEIVE(mtx);
+       MUTEX_MEMBAR_ENTER();
        return rv;
 }
 
@@ -234,7 +245,7 @@
 {
        int rv;
        rv = MUTEX_CAS(&mtx->mtx_owner, owner, owner | MUTEX_BIT_WAITERS);
-       MUTEX_RECEIVE(mtx);
+       MUTEX_MEMBAR_ENTER();
        return rv;
 }
 
@@ -243,7 +254,7 @@
 {
        uintptr_t newown;
 
-       MUTEX_GIVE(mtx);
+       MUTEX_MEMBAR_EXIT();
        newown = 0;
        MUTEX_INHERITDEBUG(newown, mtx->mtx_owner);
        mtx->mtx_owner = newown;