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usleep.c revision 1.11 
      1 /*	$NetBSD: usleep.c,v 1.11 1997/07/13 19:41:46 christos 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 #include <sys/cdefs.h>
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 #if 0
     39 static char sccsid[] = "@(#)usleep.c	8.1 (Berkeley) 6/4/93";
     40 #else
     41 __RCSID("$NetBSD: usleep.c,v 1.11 1997/07/13 19:41:46 christos Exp $");
     42 #endif
     43 #endif /* LIBC_SCCS and not lint */
     44 
     45 #include <sys/time.h>
     46 #include <signal.h>
     47 #include <unistd.h>
     48 
     49 #define	TICK	10000		/* system clock resolution in microseconds */
     50 
     51 static volatile int ringring;
     52 static void sleephandler __P((int));
     53 
     54 void
     55 usleep(useconds)
     56 	unsigned int useconds;
     57 {
     58 	struct itimerval itv, oitv;
     59 	struct sigaction act, oact;
     60 	sigset_t set, oset;
     61 
     62 	if (!useconds)
     63 		return;
     64 
     65 	sigemptyset(&set);
     66 	sigaddset(&set, SIGALRM);
     67 	sigprocmask(SIG_BLOCK, &set, &oset);
     68 
     69 	act.sa_handler = sleephandler;
     70 	act.sa_flags = 0;
     71 	sigemptyset(&act.sa_mask);
     72 	sigaction(SIGALRM, &act, &oact);
     73 
     74 	timerclear(&itv.it_interval);
     75 	itv.it_value.tv_sec = useconds / 1000000;
     76 	itv.it_value.tv_usec = useconds % 1000000;
     77 	setitimer(ITIMER_REAL, &itv, &oitv);
     78 
     79 	if (timerisset(&oitv.it_value)) {
     80 		if (timercmp(&oitv.it_value, &itv.it_value, >)) {
     81 			timersub(&oitv.it_value, &itv.it_value, &oitv.it_value);
     82 		} else {
     83 			itv.it_value = oitv.it_value;
     84 			/*
     85 			 * This is a hack, but we must have time to return
     86 			 * from the setitimer after the alarm or else it'll
     87 			 * be restarted.  And, anyway, sleep never did
     88 			 * anything more than this before.
     89 			 */
     90 			oitv.it_value.tv_sec = 0;
     91 			oitv.it_value.tv_usec = 2 * TICK;
     92 
     93 			setitimer(ITIMER_REAL, &itv, NULL);
     94 		}
     95 	}
     96 
     97 	set = oset;
     98 	sigdelset(&set, SIGALRM);
     99 	ringring = 0;
    100  	(void) sigsuspend(&set);
    101 
    102 	if (!ringring) {
    103 		struct itimerval nulltv;
    104 		/*
    105 		 * Interrupted by other signal; allow for pending
    106 		 * SIGALRM to be processed before resetting handler,
    107 		 * after first turning off the timer.
    108 		 */
    109 		timerclear(&nulltv.it_interval);
    110 		timerclear(&nulltv.it_value);
    111 		(void) setitimer(ITIMER_REAL, &nulltv, NULL);
    112 	}
    113 	sigprocmask(SIG_SETMASK, &oset, NULL);
    114 	sigaction(SIGALRM, &oact, NULL);
    115 	(void) setitimer(ITIMER_REAL, &oitv, NULL);
    116 }
    117 
    118 static void
    119 sleephandler(n)
    120 	int n;
    121 {
    122 	ringring = 1;
    123 }
    124