usleep.c revision 26385 
1/*
2 * Copyright (c) 1989, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#if defined(LIBC_SCCS) && !defined(lint)
35static char sccsid[] = "@(#)usleep.c	8.1 (Berkeley) 6/4/93";
36#endif /* LIBC_SCCS and not lint */
37
38#include <sys/time.h>
39#include <signal.h>
40#include <unistd.h>
41#ifdef  _THREAD_SAFE
42#include <pthread.h>
43#include "pthread_private.h"
44#endif
45
46#ifndef _THREAD_SAFE
47static void
48sleephandler()
49{
50	return;
51}
52#endif	/* _THREAD_SAFE */
53
54
55void
56usleep(useconds)
57	unsigned int useconds;
58{
59#ifdef _THREAD_SAFE
60	struct timespec time_to_sleep;
61	struct timespec time_remaining;
62
63	if (useconds) {
64		time_to_sleep.tv_nsec = (useconds % 1000000) * 1000;
65		time_to_sleep.tv_sec = useconds / 1000000;
66		do {
67			nanosleep(&time_to_sleep, &time_remaining);
68			time_to_sleep = time_remaining;
69		} while (time_to_sleep.tv_sec != 0 &&
70			 time_to_sleep.tv_nsec != 0);
71	}
72#else
73	struct timespec time_to_sleep;
74	struct timespec time_remaining;
75	struct sigaction act, oact;
76	sigset_t mask, omask;
77	int alarm_blocked;
78
79	if (useconds != 0) {
80		time_to_sleep.tv_nsec = (useconds % 1000000) * 1000;
81		time_to_sleep.tv_sec = useconds / 1000000;
82
83		/* Block SIGALRM while fiddling with it */
84		sigemptyset(&mask);
85		sigaddset(&mask, SIGALRM);
86		sigprocmask(SIG_BLOCK, &mask, &omask);
87
88		/* Was SIGALRM blocked already? */
89		alarm_blocked = sigismember(&omask, SIGALRM);
90
91		if (!alarm_blocked) {
92			/*
93			 * Set up handler to interrupt signanosleep only if
94			 * SIGALRM was unblocked. (Save some syscalls)
95			 */
96			memset(&act, 0, sizeof(act));
97			act.sa_handler = sleephandler;
98			sigaction(SIGALRM, &act, &oact);
99		}
100
101		/*
102		 * signanosleep() uses the given mask for the lifetime of
103		 * the syscall only - it resets on return.  Note that the
104		 * Old sleep explicitly unblocks SIGALRM during the sleep,
105		 * we don't do that now since we don't depend on SIGALRM
106		 * to end the timout.  If the process blocks SIGALRM, it
107		 * gets what it asks for.
108		 */
109
110		do {
111			signanosleep(&time_to_sleep, &time_remaining, &mask);
112			time_to_sleep = time_remaining;
113		} while (time_to_sleep.tv_sec != 0 &&
114			 time_to_sleep.tv_nsec != 0);
115
116		if (!alarm_blocked) {
117			/* Unwind */
118			sigaction(SIGALRM, &oact, (struct sigaction *)0);
119			sigprocmask(SIG_SETMASK, &omask, (sigset_t *)0);
120		}
121	}
122#endif	/* _THREAD_SAFE */
123}
124