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usleep.c revision 1.7.2.1 
      1 /*	$NetBSD: usleep.c,v 1.7.2.1 1995/10/20 17:33:23 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[] = "@(#)usleep.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 static char rcsid[] = "$NetBSD: usleep.c,v 1.7.2.1 1995/10/20 17:33:23 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 #define	TICK	10000		/* system clock resolution in microseconds */
     49 
     50 static volatile int ringring;
     51 
     52 void
     53 usleep(useconds)
     54 	unsigned int useconds;
     55 {
     56 	struct itimerval itv, oitv;
     57 	struct sigaction act, oact;
     58 	sigset_t set, oset;
     59 	static void sleephandler();
     60 
     61 	if (!useconds)
     62 		return;
     63 
     64 	sigemptyset(&set);
     65 	sigaddset(&set, SIGALRM);
     66 	sigprocmask(SIG_BLOCK, &set, &oset);
     67 
     68 	act.sa_handler = sleephandler;
     69 	act.sa_flags = 0;
     70 	sigemptyset(&act.sa_mask);
     71 	sigaction(SIGALRM, &act, &oact);
     72 
     73 	timerclear(&itv.it_interval);
     74 	itv.it_value.tv_sec = useconds / 1000000;
     75 	itv.it_value.tv_usec = useconds % 1000000;
     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 			itv.it_value = oitv.it_value;
     83 			/*
     84 			 * This is a hack, but we must have time to return
     85 			 * from the setitimer after the alarm or else it'll
     86 			 * be restarted.  And, anyway, sleep never did
     87 			 * anything more than this before.
     88 			 */
     89 			oitv.it_value.tv_sec = 0;
     90 			oitv.it_value.tv_usec = 2 * TICK;
     91 
     92 			setitimer(ITIMER_REAL, &itv, NULL);
     93 		}
     94 	}
     95 
     96 	set = oset;
     97 	sigdelset(&set, SIGALRM);
     98 	ringring = 0;
     99  	(void) sigsuspend(&set);
    100 
    101 	if (ringring) {
    102 		/* Our alarm went off; timer is not currently running */
    103 		sigaction(SIGALRM, &oact, NULL);
    104 		sigprocmask(SIG_SETMASK, &oset, NULL);
    105 		(void) setitimer(ITIMER_REAL, &oitv, &itv);
    106 	} else {
    107 		/*
    108 		 * Interrupted by other signal; allow for pending
    109 		 * SIGALRM to be processed before resetting handler.
    110 		 */
    111 		(void) setitimer(ITIMER_REAL, &oitv, &itv);
    112 		sigprocmask(SIG_SETMASK, &oset, NULL);
    113 		sigaction(SIGALRM, &oact, NULL);
    114 	}
    115 }
    116 
    117 static void
    118 sleephandler()
    119 {
    120 	ringring = 1;
    121 }
    122