[src/trunk]: src/sys/rump/librump/rumpkern rump: Nix membar_enter/exit after/...

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

details:   https://anonhg.NetBSD.org/src/rev/0f98bf94a05e
branches:  trunk
changeset: 373642:0f98bf94a05e
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Wed Feb 22 21:44:45 2023 +0000

description:
rump: Nix membar_enter/exit after/before RUMPUSER_LWP_CREATE/DESTROY.

These make no sense and are obviously not needed for any of the
rumpuser implementations in-tree.  (For single-threaded fiber and
pth_dummy, no barriers needed; for pth, RUMPUSER_LWP_CREATE/DESTROY
use pthread_mutex so don't need any barriers.)

It _might_ make sense to do membar_release/acquire around just
RUMPUSER_LWP_DESTROY, perhaps if there's some reference-counting
business involved.  But if a rumpuser implementation really needs
that it can do it itself.

diffstat:

 sys/rump/librump/rumpkern/lwproc.c |  6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diffs (34 lines):

diff -r cd60f018baf3 -r 0f98bf94a05e sys/rump/librump/rumpkern/lwproc.c
--- a/sys/rump/librump/rumpkern/lwproc.c        Wed Feb 22 21:44:33 2023 +0000
+++ b/sys/rump/librump/rumpkern/lwproc.c        Wed Feb 22 21:44:45 2023 +0000
@@ -1,4 +1,4 @@
-/*      $NetBSD: lwproc.c,v 1.53 2023/02/22 21:44:33 riastradh Exp $   */
+/*      $NetBSD: lwproc.c,v 1.54 2023/02/22 21:44:45 riastradh Exp $   */
 
 /*
  * Copyright (c) 2010, 2011 Antti Kantee.  All Rights Reserved.
@@ -28,7 +28,7 @@
 #define RUMP__CURLWP_PRIVATE
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: lwproc.c,v 1.53 2023/02/22 21:44:33 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: lwproc.c,v 1.54 2023/02/22 21:44:45 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -334,7 +334,6 @@
        lwp_finispecific(l);
 
        lwproc_curlwpop(RUMPUSER_LWP_DESTROY, l);
-       membar_exit();
        kmem_free(l, sizeof(*l));
 
        if (p->p_stat == SDEAD)
@@ -379,7 +378,6 @@
        lwp_initspecific(l);
        PSREF_DEBUG_INIT_LWP(l);
 
-       membar_enter();
        lwproc_curlwpop(RUMPUSER_LWP_CREATE, l);
        if (doswitch) {
                rump_lwproc_switch(l);