usleep.c revision 28192 
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 <errno.h>
39#include <sys/time.h>
40#include <signal.h>
41#include <unistd.h>
42#ifdef  _THREAD_SAFE
43#include <pthread.h>
44#include "pthread_private.h"
45#endif
46
47#ifndef _THREAD_SAFE
48static int alarm_termination;
49
50static void
51sleephandler()
52{
53	alarm_termination++;
54}
55#endif	/* _THREAD_SAFE */
56
57
58void
59usleep(useconds)
60	unsigned int useconds;
61{
62#ifdef _THREAD_SAFE
63	struct timespec time_to_sleep;
64	struct timespec time_remaining;
65
66	if (useconds) {
67		time_to_sleep.tv_nsec = (useconds % 1000000) * 1000;
68		time_to_sleep.tv_sec = useconds / 1000000;
69		do {
70			(void)nanosleep(&time_to_sleep, &time_remaining);
71			time_to_sleep = time_remaining;
72		} while (!errno || errno == EINTR ||
73			 time_to_sleep.tv_sec != 0 ||
74			 time_to_sleep.tv_nsec != 0);
75	}
76#else
77	struct timespec time_to_sleep;
78	struct timespec time_remaining;
79	struct sigaction act, oact;
80	sigset_t mask, omask;
81	int alarm_blocked;
82
83	if (useconds != 0) {
84		time_to_sleep.tv_nsec = (useconds % 1000000) * 1000;
85		time_to_sleep.tv_sec = useconds / 1000000;
86
87		/* Block SIGALRM while fiddling with it */
88		sigemptyset(&mask);
89		sigaddset(&mask, SIGALRM);
90		if (sigprocmask(SIG_BLOCK, &mask, &omask))
91			return;
92
93		alarm_termination = 0;
94
95		/* Was SIGALRM blocked already? */
96		alarm_blocked = sigismember(&omask, SIGALRM);
97
98		if (!alarm_blocked) {
99			/*
100			 * Set up handler to interrupt signanosleep only if
101			 * SIGALRM was unblocked. (Save some syscalls)
102			 */
103			memset(&act, 0, sizeof(act));
104			act.sa_handler = sleephandler;
105			if (sigaction(SIGALRM, &act, &oact)) {
106				(void)sigprocmask(SIG_SETMASK, &omask,
107						  (sigset_t *)0);
108				return;
109			}
110		}
111
112  		/*
113  		 * signanosleep() uses the given mask for the lifetime of
114  		 * the syscall only - it resets on return.  Note that the
115		 * old sleep() explicitly unblocks SIGALRM during the sleep,
116		 * we don't do that now since we don't depend on SIGALRM
117		 * to end the timeout.  If the process blocks SIGALRM, it
118		 * gets what it asks for.
119  		 */
120		do {
121			(void)signanosleep(&time_to_sleep, &time_remaining,
122					   &omask);
123			time_to_sleep = time_remaining;
124		} while (!alarm_termination &&
125			 (!errno || errno == EINTR ||
126			  time_to_sleep.tv_sec != 0 ||
127			  time_to_sleep.tv_nsec != 0));
128
129		if (!alarm_blocked) {
130			/* Unwind */
131			(void)sigaction(SIGALRM, &oact, (struct sigaction *)0);
132			(void)sigprocmask(SIG_SETMASK, &omask, (sigset_t *)0);
133		}
134	}
135#endif	/* _THREAD_SAFE */
136}
137