1 /* xnanosleep.c -- a more convenient interface to nanosleep
2 Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software Foundation,
16 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
18 /* Mostly written (for sleep.c) by Paul Eggert.
19 Factored out (creating this file) by Jim Meyering. */
25 #include "xnanosleep.h"
32 #include <sys/types.h>
36 #include "gethrxtime.h"
39 /* The extra casts work around common compiler bugs. */
40 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
41 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
42 It is necessary at least when t == time_t. */
43 #define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
44 ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
45 #define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
48 # define TIME_T_MAX TYPE_MAXIMUM (time_t)
51 /* POSIX.1-2001 requires that when a process is suspended, then
52 resumed, nanosleep (A, B) returns -1, sets errno to EINTR, and sets
53 *B to the time remaining at the point of resumption. However, some
54 versions of the Linux kernel incorrectly return the time remaining
55 at the point of suspension. Work around this bug on GNU/Linux
56 hosts by computing the remaining time here after nanosleep returns,
57 rather than by relying on nanosleep's computation. */
59 enum { NANOSLEEP_BUG_WORKAROUND = true };
61 enum { NANOSLEEP_BUG_WORKAROUND = false };
64 /* Sleep until the time (call it WAKE_UP_TIME) specified as
65 SECONDS seconds after the time this function is called.
66 SECONDS must be non-negative. If SECONDS is so large that
67 it is not representable as a `struct timespec', then use
68 the maximum value for that interval. Return -1 on failure
69 (setting errno), 0 on success. */
72 xnanosleep (double seconds)
74 enum { BILLION = 1000000000 };
76 bool overflow = false;
78 struct timespec ts_sleep;
81 assert (0 <= seconds);
83 if (NANOSLEEP_BUG_WORKAROUND)
85 xtime_t now = gethrxtime ();
86 double increment = XTIME_PRECISION * seconds;
87 xtime_t incr = increment;
88 stop = now + incr + (incr < increment);
89 overflow = (stop < now);
92 /* Separate whole seconds from nanoseconds.
93 Be careful to detect any overflow. */
94 ts_sleep.tv_sec = seconds;
95 ns = BILLION * (seconds - ts_sleep.tv_sec);
96 overflow |= ! (ts_sleep.tv_sec <= seconds && 0 <= ns && ns <= BILLION);
97 ts_sleep.tv_nsec = ns;
99 /* Round up to the next whole number, if necessary, so that we
100 always sleep for at least the requested amount of time. Assuming
101 the default rounding mode, we don't have to worry about the
102 rounding error when computing 'ns' above, since the error won't
103 cause 'ns' to drop below an integer boundary. */
104 ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns);
106 /* Normalize the interval length. nanosleep requires this. */
107 if (BILLION <= ts_sleep.tv_nsec)
109 time_t t = ts_sleep.tv_sec + 1;
111 /* Detect integer overflow. */
112 overflow |= (t < ts_sleep.tv_sec);
115 ts_sleep.tv_nsec -= BILLION;
122 ts_sleep.tv_sec = TIME_T_MAX;
123 ts_sleep.tv_nsec = BILLION - 1;
126 if (nanosleep (&ts_sleep, NULL) == 0)
131 if (NANOSLEEP_BUG_WORKAROUND)
133 xtime_t now = gethrxtime ();
138 xtime_t remaining = stop - now;
139 ts_sleep.tv_sec = xtime_nonnegative_sec (remaining);
140 ts_sleep.tv_nsec = xtime_nonnegative_nsec (remaining);