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sleep.c revision 1.13 
      1 /*	$NetBSD: sleep.c,v 1.13 1995/10/26 22:07:00 pk Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1989, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 #if 0
     38 static char sccsid[] = "@(#)sleep.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 static char rcsid[] = "$NetBSD: sleep.c,v 1.13 1995/10/26 22:07:00 pk Exp $";
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include <sys/time.h>
     45 #include <signal.h>
     46 #include <unistd.h>
     47 
     48 static volatile int ringring;
     49 
     50 unsigned int
     51 sleep(seconds)
     52 	unsigned int seconds;
     53 {
     54 	struct itimerval itv, oitv;
     55 	struct sigaction act, oact;
     56 	struct timeval diff;
     57 	sigset_t set, oset;
     58 	static void sleephandler();
     59 
     60 	if (!seconds)
     61 		return 0;
     62 
     63 	sigemptyset(&set);
     64 	sigaddset(&set, SIGALRM);
     65 	sigprocmask(SIG_BLOCK, &set, &oset);
     66 
     67 	act.sa_handler = sleephandler;
     68 	act.sa_flags = 0;
     69 	sigemptyset(&act.sa_mask);
     70 	sigaction(SIGALRM, &act, &oact);
     71 
     72 	timerclear(&itv.it_interval);
     73 	itv.it_value.tv_sec = seconds;
     74 	itv.it_value.tv_usec = 0;
     75 	timerclear(&diff);
     76 	setitimer(ITIMER_REAL, &itv, &oitv);
     77 
     78 	if (timerisset(&oitv.it_value)) {
     79 		if (timercmp(&oitv.it_value, &itv.it_value, >)) {
     80 			timersub(&oitv.it_value, &itv.it_value, &oitv.it_value);
     81 		} else {
     82 			/*
     83 			 * The existing timer was scheduled to fire
     84 			 * before ours, so we compute the time diff
     85 			 * so we can add it back in the end.
     86 			 */
     87 			timersub(&itv.it_value, &oitv.it_value, &diff);
     88 			itv.it_value = oitv.it_value;
     89 			/*
     90 			 * This is a hack, but we must have time to return
     91 			 * from the setitimer after the alarm or else it'll
     92 			 * be restarted.  And, anyway, sleep never did
     93 			 * anything more than this before.
     94 			 */
     95 			oitv.it_value.tv_sec  = 1;
     96 			oitv.it_value.tv_usec = 0;
     97 
     98 			setitimer(ITIMER_REAL, &itv, NULL);
     99 		}
    100 	}
    101 
    102 	set = oset;
    103 	sigdelset(&set, SIGALRM);
    104 	ringring = 0;
    105  	(void) sigsuspend(&set);
    106 
    107 	if (ringring) {
    108 		/* Our alarm went off; timer is not currently running */
    109 		sigaction(SIGALRM, &oact, NULL);
    110 		sigprocmask(SIG_SETMASK, &oset, NULL);
    111 		(void) setitimer(ITIMER_REAL, &oitv, &itv);
    112 	} else {
    113 		struct itimerval nulltv;
    114 		/*
    115 		 * Interrupted by other signal; allow for pending
    116 		 * SIGALRM to be processed before resetting handler,
    117 		 * after first turning off the timer.
    118 		 */
    119 		timerclear(&nulltv.it_interval);
    120 		timerclear(&nulltv.it_value);
    121 		(void) setitimer(ITIMER_REAL, &nulltv, &itv);
    122 		sigprocmask(SIG_SETMASK, &oset, NULL);
    123 		sigaction(SIGALRM, &oact, NULL);
    124 		(void) setitimer(ITIMER_REAL, &oitv, NULL);
    125 	}
    126 
    127 	if (timerisset(&diff))
    128 		timeradd(&itv.it_value, &diff, &itv.it_value);
    129 
    130 	return (itv.it_value.tv_sec);
    131 }
    132 
    133 static void
    134 sleephandler()
    135 {
    136 	ringring = 1;
    137 }
    138