libvirt/src/util/virhostuptime.c
Tim Wiederhake 2cdbfbe7ac virhostuptime: Fix rounding in uptime calculation
"f + 0.5" does not round correctly for values very close to
".5" for every integer multiple, e.g. "0.499999975".

Found by clang-tidy's "bugprone-incorrect-roundings" check.

Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
2021-02-02 15:00:55 +01:00

152 lines
3.5 KiB
C

/*
* virhostuptime.c: helper APIs for host uptime
*
* Copyright (C) 2019 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see
* <http://www.gnu.org/licenses/>.
*/
#include <config.h>
#ifdef WITH_GETUTXID
# include <utmpx.h>
#endif
#include "virhostuptime.h"
#include "viralloc.h"
#include "virfile.h"
#include "virlog.h"
#include "virstring.h"
#include "virtime.h"
#include "virthread.h"
#include <math.h>
#define VIR_FROM_THIS VIR_FROM_NONE
VIR_LOG_INIT("util.virhostuptime");
static unsigned long long bootTime;
static int bootTimeErrno;
static virOnceControl virHostGetBootTimeOnce = VIR_ONCE_CONTROL_INITIALIZER;
#if defined(__linux__)
# define UPTIME_FILE "/proc/uptime"
static int
virHostGetBootTimeProcfs(unsigned long long *btime)
{
unsigned long long now;
double up;
g_autofree char *buf = NULL;
char *tmp;
if (virTimeMillisNow(&now) < 0)
return -errno;
/* 1KiB limit is more than enough. */
if (virFileReadAll(UPTIME_FILE, 1024, &buf) < 0)
return -errno;
/* buf contains two doubles now:
* $uptime $idle_time
* We're interested only in the first one */
if (!(tmp = strchr(buf, ' '))) {
virReportError(VIR_ERR_INTERNAL_ERROR,
_("uptime file has unexpected format '%s'"),
buf);
return -EINVAL;
}
*tmp = '\0';
if (virStrToDouble(buf, NULL, &up) < 0) {
virReportError(VIR_ERR_INTERNAL_ERROR,
_("Unable to parse uptime value '%s'"),
buf);
return -EINVAL;
}
*btime = llround(now / 1000 - up);
return 0;
}
#endif /* defined(__linux__) */
#if defined(WITH_GETUTXID) || defined(__linux__)
static void
virHostGetBootTimeOnceInit(void)
{
# ifdef WITH_GETUTXID
struct utmpx id = {.ut_type = BOOT_TIME};
struct utmpx *res = NULL;
if (!(res = getutxid(&id))) {
bootTimeErrno = errno;
} else {
bootTime = res->ut_tv.tv_sec;
}
endutxent();
# endif /* WITH_GETUTXID */
# ifdef __linux__
if (bootTimeErrno != 0 || bootTime == 0)
bootTimeErrno = -virHostGetBootTimeProcfs(&bootTime);
# endif /* __linux__ */
}
#else /* !defined(WITH_GETUTXID) && !defined(__linux__) */
static void
virHostGetBootTimeOnceInit(void)
{
bootTimeErrno = ENOSYS;
}
#endif /* !defined(WITH_GETUTXID) && !defined(__linux__) */
/**
* virHostGetBootTime:
* @when: UNIX timestamp of boot time
*
* Get a UNIX timestamp of host boot time and store it at @when.
*
* Return: 0 on success,
* -1 otherwise.
*/
int
virHostGetBootTime(unsigned long long *when)
{
if (virHostBootTimeInit() < 0)
return -1;
if (bootTimeErrno) {
errno = bootTimeErrno;
return -1;
}
*when = bootTime;
return 0;
}
int
virHostBootTimeInit(void)
{
if (virOnce(&virHostGetBootTimeOnce, virHostGetBootTimeOnceInit) < 0)
return -1;
return 0;
}