common/syscall/alarm.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*  Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */


/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/param.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/signal.h>
#include <sys/proc.h>
#include <sys/time.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>

static void
sigalarm2proc(void *arg)
{
    proc_t *p = arg;

    mutex_enter(&p->p_lock);
    p->p_alarmid = 0;
    sigtoproc(p, NULL, SIGALRM);
    mutex_exit(&p->p_lock);
}

int
alarm(int deltat)
{
    proc_t *p = ttoproc(curthread);
    clock_t del = 0;
    clock_t ret;
    timeout_id_t tmp_id;
    clock_t delta = (uint_t)deltat;

    /*
     * We must single-thread this code relative to other
     * lwps in the same process also performing an alarm().
     * The mutex dance in the while loop is necessary because
     * we cannot call untimeout() while holding a lock that
     * is grabbed by the timeout function, sigalarm2proc().
     * We can, however, hold p->p_lock across realtime_timeout().
     */
    mutex_enter(&p->p_lock);
    while ((tmp_id = p->p_alarmid) != 0) {
        p->p_alarmid = 0;
        mutex_exit(&p->p_lock);
        del = untimeout(tmp_id);
        mutex_enter(&p->p_lock);
    }

    if (del < 0)
        ret = 0;
    else
        ret = (del + hz - 1) / hz;  /* convert to seconds */

    /*
     * Our implementation defined limit for alarm is
     * LONG_MAX / hz. Anything larger gets truncated
     * to that limit. If delta is negative we can
     * assume a wrap has occurred so peg delta in
     * that case too. 64 bit platforms have higher limit.
     */
    if (delta > (LONG_MAX / hz) || delta < 0)
        delta = LONG_MAX / hz;

    if (delta)
        p->p_alarmid = realtime_timeout(sigalarm2proc, p, delta * hz);
    mutex_exit(&p->p_lock);
    return (ret);
}