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169 lines
4.5 KiB
169 lines
4.5 KiB
From af01dd6fa3eb458e2fbb272703b0cae37ea54a9b Mon Sep 17 00:00:00 2001
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From: Marcin Jurkowski <marcin1j@gmail.com>
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Date: Tue, 11 Jul 2017 15:00:25 +0200
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Subject: [PATCH] uptime plugin: don't cache boot time and simplify Linux code
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Caching boottime on startup yields incorrect uptime values if system
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date changes after the daemon is started.
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This is almost certain to happen on embedded systems without RTC, where
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clock is set from NTP server at some point after boot process.
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On Linux, we can retrieve uptime directly by either reading /proc/uptime
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(it's sufficient to read a few bytes) or calling sysinfo() function.
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Use the latter since it's the most efficient way in speed, memory
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requirements and code simplicity terms.
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---
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src/uptime.c | 71 ++++++++++++++++--------------------------------------------
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1 file changed, 19 insertions(+), 52 deletions(-)
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--- a/src/uptime.c
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+++ b/src/uptime.c
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@@ -25,8 +25,7 @@
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#include "plugin.h"
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#if KERNEL_LINUX
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-#define STAT_FILE "/proc/stat"
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-/* Using /proc filesystem to retrieve the boot time, Linux only. */
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+#include <sys/sysinfo.h>
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/* #endif KERNEL_LINUX */
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#elif HAVE_LIBKSTAT
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@@ -53,8 +52,6 @@
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/*
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* Global variables
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*/
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-/* boottime always used, no OS distinction */
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-static time_t boottime;
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#if HAVE_LIBKSTAT
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extern kstat_ctl_t *kc;
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@@ -72,8 +69,6 @@ static void uptime_submit(gauge_t value)
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plugin_dispatch_values(&vl);
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}
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-static int uptime_init(void) /* {{{ */
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-{
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/*
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* On most unix systems the uptime is calculated by looking at the boot
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* time (stored in unix time, since epoch) and the current one. We are
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@@ -84,48 +79,21 @@ static int uptime_init(void) /* {{{ */
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* the boot time, the plugin is unregistered and there is no chance to
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* try again later. Nevertheless, this is very unlikely to happen.
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*/
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-
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+static time_t uptime_get_sys(void) { /* {{{ */
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+ time_t result;
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#if KERNEL_LINUX
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- unsigned long starttime;
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- char buffer[1024];
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- int ret;
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- FILE *fh;
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-
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- ret = 0;
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-
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- fh = fopen(STAT_FILE, "r");
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+ struct sysinfo info;
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+ int status;
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- if (fh == NULL) {
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+ status = sysinfo(&info);
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+ if (status != 0) {
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char errbuf[1024];
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- ERROR("uptime plugin: Cannot open " STAT_FILE ": %s",
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+ ERROR("uptime plugin: Error calling sysinfo: %s",
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sstrerror(errno, errbuf, sizeof(errbuf)));
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return (-1);
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}
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- while (fgets(buffer, 1024, fh) != NULL) {
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- /* look for the btime string and read the value */
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- ret = sscanf(buffer, "btime %lu", &starttime);
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- /* avoid further loops if btime has been found and read
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- * correctly (hopefully) */
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- if (ret == 1)
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- break;
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- }
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-
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- fclose(fh);
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-
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- /* loop done, check if no value has been found/read */
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- if (ret != 1) {
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- ERROR("uptime plugin: No value read from " STAT_FILE "");
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- return (-1);
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- }
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-
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- boottime = (time_t)starttime;
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-
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- if (boottime == 0) {
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- ERROR("uptime plugin: btime read from " STAT_FILE ", "
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- "but `boottime' is zero!");
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- return (-1);
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- }
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+ result = (time_t)info.uptime;
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/* #endif KERNEL_LINUX */
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#elif HAVE_LIBKSTAT
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@@ -159,13 +127,13 @@ static int uptime_init(void) /* {{{ */
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return (-1);
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}
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- boottime = (time_t)knp->value.ui32;
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-
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- if (boottime == 0) {
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+ if (knp->value.ui32 == 0) {
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ERROR("uptime plugin: kstat_data_lookup returned success, "
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"but `boottime' is zero!");
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return (-1);
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}
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+
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+ result = time(NULL) - (time_t)knp->value.ui32;
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/* #endif HAVE_LIBKSTAT */
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#elif HAVE_SYS_SYSCTL_H
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@@ -186,13 +154,13 @@ static int uptime_init(void) /* {{{ */
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return (-1);
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}
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- boottime = boottv.tv_sec;
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-
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- if (boottime == 0) {
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+ if (boottv.tv_sec == 0) {
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ERROR("uptime plugin: sysctl(3) returned success, "
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"but `boottime' is zero!");
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return (-1);
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}
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+
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+ result = time(NULL) - boottv.tv_sec;
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/* #endif HAVE_SYS_SYSCTL_H */
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#elif HAVE_PERFSTAT
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@@ -212,18 +180,18 @@ static int uptime_init(void) /* {{{ */
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if (hertz <= 0)
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hertz = HZ;
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- boottime = time(NULL) - cputotal.lbolt / hertz;
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+ result = cputotal.lbolt / hertz;
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#endif /* HAVE_PERFSTAT */
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- return (0);
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-} /* }}} int uptime_init */
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+ return result;
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+} /* }}} int uptime_get_sys */
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static int uptime_read(void) {
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gauge_t uptime;
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time_t elapsed;
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/* calculate the amount of time elapsed since boot, AKA uptime */
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- elapsed = time(NULL) - boottime;
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+ elapsed = uptime_get_sys();
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uptime = (gauge_t)elapsed;
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@@ -233,6 +201,5 @@ static int uptime_read(void) {
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}
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void module_register(void) {
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- plugin_register_init("uptime", uptime_init);
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plugin_register_read("uptime", uptime_read);
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} /* void module_register */
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