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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
     22 /*	  All Rights Reserved	*/
     23 
     24 
     25 /*
     26  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
     27  * Use is subject to license terms.
     28  */
     29 
     30 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     31 
     32 #include <sys/param.h>
     33 #include <sys/types.h>
     34 #include <sys/sysmacros.h>
     35 #include <sys/systm.h>
     36 #include <sys/errno.h>
     37 #include <sys/signal.h>
     38 #include <sys/proc.h>
     39 #include <sys/time.h>
     40 #include <sys/cmn_err.h>
     41 #include <sys/debug.h>
     42 
     43 static void
     44 sigalarm2proc(void *arg)
     45 {
     46 	proc_t *p = arg;
     47 
     48 	mutex_enter(&p->p_lock);
     49 	p->p_alarmid = 0;
     50 	sigtoproc(p, NULL, SIGALRM);
     51 	mutex_exit(&p->p_lock);
     52 }
     53 
     54 int
     55 alarm(int deltat)
     56 {
     57 	proc_t *p = ttoproc(curthread);
     58 	clock_t del = 0;
     59 	clock_t ret;
     60 	timeout_id_t tmp_id;
     61 	clock_t delta = (uint_t)deltat;
     62 
     63 	/*
     64 	 * We must single-thread this code relative to other
     65 	 * lwps in the same process also performing an alarm().
     66 	 * The mutex dance in the while loop is necessary because
     67 	 * we cannot call untimeout() while holding a lock that
     68 	 * is grabbed by the timeout function, sigalarm2proc().
     69 	 * We can, however, hold p->p_lock across realtime_timeout().
     70 	 */
     71 	mutex_enter(&p->p_lock);
     72 	while ((tmp_id = p->p_alarmid) != 0) {
     73 		p->p_alarmid = 0;
     74 		mutex_exit(&p->p_lock);
     75 		del = untimeout(tmp_id);
     76 		mutex_enter(&p->p_lock);
     77 	}
     78 
     79 	if (del < 0)
     80 		ret = 0;
     81 	else
     82 		ret = (del + hz - 1) / hz;	/* convert to seconds */
     83 
     84 	/*
     85 	 * Our implementation defined limit for alarm is
     86 	 * LONG_MAX / hz. Anything larger gets truncated
     87 	 * to that limit. If delta is negative we can
     88 	 * assume a wrap has occurred so peg delta in
     89 	 * that case too. 64 bit platforms have higher limit.
     90 	 */
     91 	if (delta > (LONG_MAX / hz) || delta < 0)
     92 		delta = LONG_MAX / hz;
     93 
     94 	if (delta)
     95 		p->p_alarmid = realtime_timeout(sigalarm2proc, p, delta * hz);
     96 	mutex_exit(&p->p_lock);
     97 	return (ret);
     98 }
     99