[src/trunk]: src/sys/kern timecounter(9): Ward off interrupts during time_sec...

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

details:   https://anonhg.NetBSD.org/src/rev/3aa5b57a9028
branches:  trunk
changeset: 377561:3aa5b57a9028
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Mon Jul 17 13:35:07 2023 +0000

description:
timecounter(9): Ward off interrupts during time_second/uptime update.

Only relevant during 32-bit wraparound, so the potential performance
impact of using splhigh here is negligible; indeed, we would have to
go out of our way to exercise this in tests before it will ever
happen in the next century.

diffstat:

 sys/kern/kern_tc.c |  7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diffs (42 lines):

diff -r 39879d996306 -r 3aa5b57a9028 sys/kern/kern_tc.c
--- a/sys/kern/kern_tc.c        Mon Jul 17 13:29:12 2023 +0000
+++ b/sys/kern/kern_tc.c        Mon Jul 17 13:35:07 2023 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_tc.c,v 1.64 2023/07/17 13:29:12 riastradh Exp $ */
+/* $NetBSD: kern_tc.c,v 1.65 2023/07/17 13:35:07 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 1.64 2023/07/17 13:29:12 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_tc.c,v 1.65 2023/07/17 13:35:07 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ntp.h"
@@ -172,6 +172,7 @@ setrealuptime(time_t second, time_t upti
 {
        uint32_t seclo = second & 0xffffffff, sechi = second >> 32;
        uint32_t uplo = uptime & 0xffffffff, uphi = uptime >> 32;
+       int s;
 
        KDASSERT(mutex_owned(&timecounter_lock));
 
@@ -186,6 +187,7 @@ setrealuptime(time_t second, time_t upti
                return;
        }
 
+       s = splhigh();
        atomic_store_relaxed(&time__second32.hi, 0xffffffff);
        atomic_store_relaxed(&time__uptime32.hi, 0xffffffff);
        membar_producer();
@@ -194,6 +196,7 @@ setrealuptime(time_t second, time_t upti
        membar_producer();
        atomic_store_relaxed(&time__second32.hi, sechi);
        atomic_store_relaxed(&time__uptime32.hi, uphi);
+       splx(s);
 }
 
 time_t