[src/trunk]: src/sys/arch/alpha/alpha alpha: Use load-acquire/store-release.

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

details:   https://anonhg.NetBSD.org/src/rev/bf6e5a0d6c52
branches:  trunk
changeset: 975938:bf6e5a0d6c52
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue Sep 08 21:41:37 2020 +0000

description:
alpha: Use load-acquire/store-release.

Omit needless membar in pmap_kenter_pa while here -- caller must
ensure pmap_kenter_pa on one CPU happens before use of the VA on
another CPU anyway, so there is no benefit to a membar here.

ok thorpej@

diffstat:

 sys/arch/alpha/alpha/pmap.c |  11 ++++-------
 1 files changed, 4 insertions(+), 7 deletions(-)

diffs (53 lines):

diff -r ca3d470e3281 -r bf6e5a0d6c52 sys/arch/alpha/alpha/pmap.c
--- a/sys/arch/alpha/alpha/pmap.c       Tue Sep 08 19:17:24 2020 +0000
+++ b/sys/arch/alpha/alpha/pmap.c       Tue Sep 08 21:41:37 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.c,v 1.271 2020/09/03 02:09:09 thorpej Exp $ */
+/* $NetBSD: pmap.c,v 1.272 2020/09/08 21:41:37 riastradh Exp $ */
 
 /*-
  * Copyright (c) 1998, 1999, 2000, 2001, 2007, 2008, 2020
@@ -135,7 +135,7 @@
 
 #include <sys/cdefs.h>                 /* RCS ID & Copyright macro defns */
 
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.271 2020/09/03 02:09:09 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.272 2020/09/08 21:41:37 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -979,7 +979,7 @@
                int backoff = SPINLOCK_BACKOFF_MIN;
                u_int spins = 0;
 
-               while (atomic_load_relaxed(&tlb_context) != NULL) {
+               while (atomic_load_acquire(&tlb_context) != NULL) {
                        SPINLOCK_BACKOFF(backoff);
                        if (spins++ > 0x0fffffff) {
                                printf("TLB LOCAL MASK  = 0x%016lx\n",
@@ -994,7 +994,6 @@
                                panic("pmap_tlb_shootnow");
                        }
                }
-               membar_consumer();
        }
        KASSERT(tlb_context == NULL);
 #endif /* MULTIPROCESSOR */
@@ -1025,8 +1024,7 @@
        KASSERT(tlb_context != NULL);
        pmap_tlb_invalidate(tlb_context, ci);
        if (atomic_and_ulong_nv(&tlb_pending, ~(1UL << ci->ci_cpuid)) == 0) {
-               membar_producer();
-               atomic_store_relaxed(&tlb_context, NULL);
+               atomic_store_release(&tlb_context, NULL);
        }
 }
 #endif /* MULTIPROCESSOR */
@@ -2275,7 +2273,6 @@
        /* Set the new PTE. */
        const pt_entry_t opte = atomic_load_relaxed(pte);
        atomic_store_relaxed(pte, npte);
-       PMAP_MP(membar_enter());
 
        PMAP_STAT_INCR(pmap->pm_stats.resident_count, 1);
        PMAP_STAT_INCR(pmap->pm_stats.wired_count, 1);