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From a3c400a8553b598bc2fd01eb0f63c5748b2147e1 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
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Date: Wed, 8 Nov 2017 17:02:42 +0100
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Subject: [PATCH] Prefer clock_gettime(CLOCK_MONOTONIC)
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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gettimeofday() reports wrong elapsed real time if a time step was
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inserted while running a program. This can happen on initial time
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adjustment from NTP server or by manual adjustement by date command.
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This patch uses clock_gettime(CLOCK_MONOTONIC) instead (if available)
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that does not suffer from the issue.
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<http://lists.gnu.org/archive/html/bug-gnu-utils/2013-09/msg00008.html>
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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configure.ac | 3 +++
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src/resuse.c | 27 +++++++++++++++++++++++++--
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2 files changed, 28 insertions(+), 2 deletions(-)
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diff --git a/configure.ac b/configure.ac
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index ede8fd5..d2950bd 100644
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--- a/configure.ac
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+++ b/configure.ac
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@@ -72,6 +72,9 @@ dnl Checks for library functions.
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AC_FUNC_VPRINTF
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AC_FUNC_WAIT3
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AC_CHECK_FUNCS(strerror)
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+AC_SEARCH_LIBS(clock_gettime, [rt])
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+test "$ac_cv_search_clock_gettime" != "no" && \
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+ AC_DEFINE([HAVE_CLOCK_GETTIME], [1], [System provides clock_gettime() call])
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# What memory units are reported by getrusage(2) ?
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diff --git a/src/resuse.c b/src/resuse.c
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index d2ab870..ec54863 100644
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--- a/src/resuse.c
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+++ b/src/resuse.c
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@@ -26,7 +26,14 @@
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#include <sys/wait.h>
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#include <sys/resource.h>
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-#if !HAVE_WAIT3
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+#if HAVE_WAIT3
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+# if HAVE_CLOCK_GETTIME
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+# ifndef _POSIX_C_SOURCE
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+# define _POSIX_C_SOURCE 199309L
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+# endif
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+# include <time.h>
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+# endif
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+#else
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# include <sys/times.h>
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# ifndef HZ
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# include <sys/param.h>
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@@ -51,7 +58,14 @@ resuse_start (resp)
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RESUSE *resp;
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{
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#if HAVE_WAIT3
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+#if HAVE_CLOCK_GETTIME
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+ struct timespec res;
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+ clock_gettime(CLOCK_MONOTONIC, &res);
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+ resp->start.tv_sec = res.tv_sec;
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+ resp->start.tv_usec = res.tv_nsec / 1000;
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+#else
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gettimeofday (&resp->start, (struct timezone *) 0);
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+#endif /* !HAVE_CLOCK_GETTIME */
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#else
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long value;
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struct tms tms;
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@@ -59,7 +73,7 @@ resuse_start (resp)
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value = times (&tms);
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resp->start.tv_sec = value / HZ;
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resp->start.tv_usec = value % HZ * (1000000 / HZ);
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-#endif
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+#endif /* !HAVE_WAIT3 */
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}
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/* Wait for and fill in data on child process PID.
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@@ -79,6 +93,9 @@ resuse_end (pid, resp)
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int status;
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#if HAVE_WAIT3
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+#if HAVE_CLOCK_GETTIME
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+ struct timespec res;
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+#endif
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pid_t caught;
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/* Ignore signals, but don't ignore the children. When wait3
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@@ -89,7 +106,13 @@ resuse_end (pid, resp)
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return 0;
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}
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+#if HAVE_CLOCK_GETTIME
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+ clock_gettime(CLOCK_MONOTONIC, &res);
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+ resp->elapsed.tv_sec = res.tv_sec;
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+ resp->elapsed.tv_usec = res.tv_nsec / 1000;
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+#else
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gettimeofday (&resp->elapsed, (struct timezone *) 0);
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+#endif
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#else /* !HAVE_WAIT3 */
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long value;
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struct tms tms;
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--
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2.13.6
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