From 58206c6863f6b861a5e2fa6d3599e487294ded63 Mon Sep 17 00:00:00 2001 From: Siddhesh Poyarekar Date: Thu, 13 Jun 2013 09:54:35 +0530 Subject: [PATCH] Improve precision of clock() function on Linux Resolves #12515. Use CLOCK_PROCESS_CPUTIME_ID instead of times to get better precision in the value returned by clock. --- ChangeLog | 6 ++++++ NEWS | 22 +++++++++++--------- sysdeps/unix/sysv/linux/clock.c | 36 +++++++++++++++------------------ 3 files changed, 34 insertions(+), 30 deletions(-) diff --git a/ChangeLog b/ChangeLog index d08f0a6b2e..0452a7c739 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2013-06-13 Siddhesh Poyarekar + + [BZ #12515] + * sysdeps/unix/sysv/linux/clock.c (clock): Use result from + CLOCK_PROCESS_CPUTIME_ID clock instead of __times. + 2013-06-11 Adhemerval Zanella [BZ #15605] diff --git a/NEWS b/NEWS index 782010d157..354db75cf8 100644 --- a/NEWS +++ b/NEWS @@ -10,16 +10,16 @@ Version 2.18 * The following bugs are resolved with this release: 2546, 2560, 5159, 6809, 10060, 10062, 10357, 10686, 11120, 11561, 12387, - 12723, 13550, 13889, 13951, 13988, 14142, 14176, 14200, 14256, 14280, - 14293, 14317, 14327, 14478, 14496, 14582, 14686, 14812, 14888, 14894, - 14908, 14920, 14952, 14964, 14981, 14982, 14985, 14991, 14994, 14996, - 15000, 15003, 15006, 15007, 15014, 15020, 15023, 15036, 15054, 15055, - 15062, 15078, 15084, 15085, 15086, 15100, 15160, 15214, 15221, 15232, - 15234, 15283, 15285, 15287, 15304, 15305, 15307, 15309, 15327, 15330, - 15335, 15336, 15337, 15339, 15342, 15346, 15359, 15361, 15366, 15380, - 15381, 15394, 15395, 15405, 15406, 15409, 15416, 15418, 15419, 15423, - 15424, 15426, 15429, 15441, 15442, 15448, 15465, 15480, 15485, 15488, - 15490, 15493, 15497, 15506, 15529, 15536, 15553, 15577, 15583. + 12515, 12723, 13550, 13889, 13951, 13988, 14142, 14176, 14200, 14256, + 14280, 14293, 14317, 14327, 14478, 14496, 14582, 14686, 14812, 14888, + 14894, 14908, 14920, 14952, 14964, 14981, 14982, 14985, 14991, 14994, + 14996, 15000, 15003, 15006, 15007, 15014, 15020, 15023, 15036, 15054, + 15055, 15062, 15078, 15084, 15085, 15086, 15100, 15160, 15214, 15221, + 15232, 15234, 15283, 15285, 15287, 15304, 15305, 15307, 15309, 15327, + 15330, 15335, 15336, 15337, 15339, 15342, 15346, 15359, 15361, 15366, + 15380, 15381, 15394, 15395, 15405, 15406, 15409, 15416, 15418, 15419, + 15423, 15424, 15426, 15429, 15441, 15442, 15448, 15465, 15480, 15485, + 15488, 15490, 15493, 15497, 15506, 15529, 15536, 15553, 15577, 15583. * CVE-2013-0242 Buffer overrun in regexp matcher has been fixed (Bugzilla #15078). @@ -41,6 +41,8 @@ Version 2.18 * New macro named issignaling to check for a signaling NaN (sNaN). It is based on draft TS 18661 and currently enabled as a GNU extension. + +* Improved precision of the clock() function on Linux. Version 2.17 diff --git a/sysdeps/unix/sysv/linux/clock.c b/sysdeps/unix/sysv/linux/clock.c index 5268d33c73..16036bd139 100644 --- a/sysdeps/unix/sysv/linux/clock.c +++ b/sysdeps/unix/sysv/linux/clock.c @@ -1,4 +1,5 @@ -/* Copyright (C) 1991-2013 Free Software Foundation, Inc. +/* Return the time used by the program so far (user time + system time). + Copyright (C) 1991-2013 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -19,26 +20,21 @@ #include #include -/* Return the time used by the program so far (user time + system time). */ +#if CLOCKS_PER_SEC != 1000000l +# error "CLOCKS_PER_SEC should be 1000000" +#endif + clock_t clock (void) { - struct tms buf; - long clk_tck = __sysconf (_SC_CLK_TCK); - - /* We don't check for errors here. The only error the kernel - returns is EFAULT if the value cannot be written to the struct we - pass a pointer to. Otherwise the kernel returns an `unsigned - long' value which is the number of jiffies since system start. - But this number can be negative (when read as `long') when the - system is up for some time. Ignoring errors should therefore - have no negative impacts but solve the problem. */ - __times (&buf); - - return - (clk_tck <= CLOCKS_PER_SEC) - ? ((unsigned long) buf.tms_utime + buf.tms_stime) * (CLOCKS_PER_SEC - / clk_tck) - : ((unsigned long) buf.tms_utime + buf.tms_stime) / (clk_tck - / CLOCKS_PER_SEC); + struct timespec ts; + + /* clock_gettime shouldn't fail here since CLOCK_PROCESS_CPUTIME_ID is + supported since 2.6.12. Check the return value anyway in case the kernel + barfs on us for some reason. */ + if (__glibc_unlikely (__clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &ts) != 0)) + return (clock_t) -1; + + return (ts.tv_sec * CLOCKS_PER_SEC + + ts.tv_nsec / (1000000000 / CLOCKS_PER_SEC)); } -- 2.43.5