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tsc_get_timecount(): cover the backwards check by DIAGNOSTIC since it has 

proven the point by now.
This commit is contained in:
ad 2023-09-09 18:37:03 +00:00
parent e5756b164f
commit e5d38798d7
1 changed files with 13 additions and 15 deletions
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28
sys/arch/x86/x86/tsc.c
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@ -1,4 +1,4 @@
/* $NetBSD: tsc.c,v 1.57 2021/10/15 18:12:48 jmcneill Exp $ */
/* $NetBSD: tsc.c,v 1.58 2023/09/09 18:37:03 ad Exp $ */
/*-
* Copyright (c) 2008, 2020 The NetBSD Foundation, Inc.
@ -27,7 +27,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tsc.c,v 1.57 2021/10/15 18:12:48 jmcneill Exp $");
__KERNEL_RCSID(0, "$NetBSD: tsc.c,v 1.58 2023/09/09 18:37:03 ad Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@ -406,7 +406,7 @@ tsc_delay(unsigned int us)
static u_int
tsc_get_timecount(struct timecounter *tc)
{
#ifdef _LP64 /* requires atomic 64-bit store */
#if defined(_LP64) && defined(DIAGNOSTIC) /* requires atomic 64-bit store */
static __cpu_simple_lock_t lock = __SIMPLELOCK_UNLOCKED;
static int lastwarn;
uint64_t cur, prev;
@ -421,19 +421,17 @@ tsc_get_timecount(struct timecounter *tc)
*/
prev = l->l_md.md_tsc;
cur = cpu_counter();
if (__predict_false(cur < prev)) {
if ((cur >> 63) == (prev >> 63) &&
__cpu_simple_lock_try(&lock)) {
ticks = getticks();
if (ticks - lastwarn >= hz) {
printf(
"WARNING: TSC time went backwards by %u - "
"change sysctl(7) kern.timecounter?\n",
(unsigned)(prev - cur));
lastwarn = ticks;
}
__cpu_simple_unlock(&lock);
if (__predict_false(cur < prev) && (cur >> 63) == (prev >> 63) &&
__cpu_simple_lock_try(&lock)) {
ticks = getticks();
if (ticks - lastwarn >= hz) {
printf(
"WARNING: %s TSC went backwards by %u - "
"change sysctl(7) kern.timecounter?\n",
cpu_name(curcpu()), (unsigned)(prev - cur));
lastwarn = ticks;
}
__cpu_simple_unlock(&lock);
}
l->l_md.md_tsc = cur;
return (uint32_t)cur;