[src/trunk]: src/sys/kern timecounter(9): Use atomic_store_release/load_consu...

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

details:   https://anonhg.NetBSD.org/src/rev/2e9ca98a3723
branches:  trunk
changeset: 377571:2e9ca98a3723
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Mon Jul 17 21:51:30 2023 +0000

description:
timecounter(9): Use atomic_store_release/load_consume for timehands.

This probably fixes real bugs on Alpha and makes the synchronization
pattern clearer everywhere.

diffstat:

 sys/kern/kern_tc.c |  23 +++++++++++------------
 1 files changed, 11 insertions(+), 12 deletions(-)

diffs (100 lines):

diff -r 276efc6b80d9 -r 2e9ca98a3723 sys/kern/kern_tc.c
--- a/sys/kern/kern_tc.c        Mon Jul 17 21:51:20 2023 +0000
+++ b/sys/kern/kern_tc.c        Mon Jul 17 21:51:30 2023 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_tc.c,v 1.71 2023/07/17 21:51:20 riastradh Exp $ */
+/* $NetBSD: kern_tc.c,v 1.72 2023/07/17 21:51:30 riastradh Exp $ */
 
 /*-
  * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@@ -40,7 +40,7 @@
 
 #include <sys/cdefs.h>
 /* __FBSDID("$FreeBSD: src/sys/kern/kern_tc.c,v 1.166 2005/09/19 22:16:31 andre Exp $"); */
-__KERNEL_RCSID(0, "$NetBSD: kern_tc.c,v 1.71 2023/07/17 21:51:20 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_tc.c,v 1.72 2023/07/17 21:51:30 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ntp.h"
@@ -466,7 +466,7 @@ binuptime(struct bintime *bt)
        __insn_barrier();
 
        do {
-               th = timehands;
+               th = atomic_load_consume(&timehands);
                gen = th->th_generation;
                *bt = th->th_offset;
                bintime_addx(bt, th->th_scale * tc_delta(th));
@@ -535,7 +535,7 @@ getbinuptime(struct bintime *bt)
 
        TC_COUNT(ngetbinuptime);
        do {
-               th = timehands;
+               th = atomic_load_consume(&timehands);
                gen = th->th_generation;
                *bt = th->th_offset;
        } while (gen == 0 || gen != th->th_generation);
@@ -549,7 +549,7 @@ getnanouptime(struct timespec *tsp)
 
        TC_COUNT(ngetnanouptime);
        do {
-               th = timehands;
+               th = atomic_load_consume(&timehands);
                gen = th->th_generation;
                bintime2timespec(&th->th_offset, tsp);
        } while (gen == 0 || gen != th->th_generation);
@@ -563,7 +563,7 @@ getmicrouptime(struct timeval *tvp)
 
        TC_COUNT(ngetmicrouptime);
        do {
-               th = timehands;
+               th = atomic_load_consume(&timehands);
                gen = th->th_generation;
                bintime2timeval(&th->th_offset, tvp);
        } while (gen == 0 || gen != th->th_generation);
@@ -578,7 +578,7 @@ getbintime(struct bintime *bt)
 
        TC_COUNT(ngetbintime);
        do {
-               th = timehands;
+               th = atomic_load_consume(&timehands);
                gen = th->th_generation;
                *bt = th->th_offset;
        } while (gen == 0 || gen != th->th_generation);
@@ -594,7 +594,7 @@ dogetnanotime(struct timespec *tsp)
 
        TC_COUNT(ngetnanotime);
        do {
-               th = timehands;
+               th = atomic_load_consume(&timehands);
                gen = th->th_generation;
                *tsp = th->th_nanotime;
        } while (gen == 0 || gen != th->th_generation);
@@ -624,7 +624,7 @@ getmicrotime(struct timeval *tvp)
 
        TC_COUNT(ngetmicrotime);
        do {
-               th = timehands;
+               th = atomic_load_consume(&timehands);
                gen = th->th_generation;
                *tvp = th->th_microtime;
        } while (gen == 0 || gen != th->th_generation);
@@ -839,7 +839,7 @@ uint64_t
 tc_getfrequency(void)
 {
 
-       return timehands->th_counter->tc_frequency;
+       return atomic_load_consume(&timehands)->th_counter->tc_frequency;
 }
 
 /*
@@ -1015,8 +1015,7 @@ tc_windup(void)
         * globally visible before changing.
         */
        setrealuptime(th->th_microtime.tv_sec, th->th_offset.sec);
-       membar_producer();
-       timehands = th;
+       atomic_store_release(&timehands, th);
 
        /*
         * Force users of the old timehand to move on.  This is