kernel/syscall/alarm.c

   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 }