usr/src/usr.sbin/amd/amd/clock.c

/*
 * Copyright (c) 1989 Jan-Simon Pendry
 * Copyright (c) 1989 Imperial College of Science, Technology & Medicine
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Jan-Simon Pendry at Imperial College, London.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)clock.c     5.3 (Berkeley) 5/12/91
 *
 * $Id: clock.c,v 5.2.1.5 91/05/07 22:17:49 jsp Alpha $
 *
 */

/*
 * Callouts.
 *
 * Modelled on kernel object of the same name.
 * See usual references.
 *
 * Use of a heap-based mechanism was rejected:
 * 1.  more complex implementation needed.
 * 2.  not obvious that a list is too slow for Amd.
 */

#include "am.h"

typedef struct callout callout;
struct callout {
        callout *c_next;                /* List of callouts */
        void    (*c_fn)();              /* Function to call */
        voidp   c_closure;              /* Closure to pass to call */
        time_t  c_time;                 /* Time of call */
        int     c_id;                   /* Unique identifier */
};

static callout callouts;                /* List of pending callouts */
static callout *free_callouts;          /* Cache of free callouts */
static int nfree_callouts;              /* Number on free list */
static int callout_id;                  /* Next free callout identifier */
time_t next_softclock;                  /* Time of next call to softclock() */

/*
 * Number of callout slots we keep on the free list
 */
#define CALLOUT_FREE_SLOP       10

/*
 * Global assumption: valid id's are non-zero.
 */
#define CID_ALLOC()     (++callout_id)
#define CID_UNDEF       (0)

static callout *alloc_callout(P_void);
static callout *alloc_callout()
{
        callout *cp = free_callouts;
        if (cp) {
                --nfree_callouts;
                free_callouts = free_callouts->c_next;
                return cp;
        }
        return ALLOC(callout);
}

static void free_callout P((callout *cp));
static void free_callout(cp)
callout *cp;
{
        if (nfree_callouts > CALLOUT_FREE_SLOP) {
                free((voidp) cp);
        } else {
                cp->c_next = free_callouts;
                free_callouts = cp;
                nfree_callouts++;
        }
}

/*
 * Schedule a callout.
 *
 * (*fn)(closure) will be called at clocktime() + secs
 */
int timeout P((unsigned int secs, void (*fn)(), voidp closure));
int timeout(secs, fn, closure)
unsigned int secs;
void (*fn)();
voidp closure;
{
        callout *cp, *cp2;
        time_t t = clocktime() + secs;

        /*
         * Allocate and fill in a new callout structure
         */
        callout *cpnew = alloc_callout();
        cpnew->c_closure = closure;
        cpnew->c_fn = fn;
        cpnew->c_time = t;
        cpnew->c_id = CID_ALLOC();

        if (t < next_softclock)
                next_softclock = t;

        /*
         * Find the correct place in the list
         */
        for (cp = &callouts; cp2 = cp->c_next; cp = cp2)
                if (cp2->c_time >= t)
                        break;

        /*
         * And link it in
         */
        cp->c_next = cpnew;
        cpnew->c_next = cp2;

        /*
         * Return callout identifier
         */
        return cpnew->c_id;
}

/*
 * De-schedule a callout
 */
void untimeout P((int id));
void untimeout(id)
int id;
{
        callout *cp, *cp2;
        for (cp = &callouts; cp2 = cp->c_next; cp = cp2) {
                if (cp2->c_id == id) {
                        cp->c_next = cp2->c_next;
                        free_callout(cp2);
                        break;
                }
        }
}

/*
 * Reschedule after clock changed
 */
void reschedule_timeouts P((time_t now, time_t then));
void reschedule_timeouts(now, then)
time_t now;
time_t then;
{
        callout *cp;

        for (cp = callouts.c_next; cp; cp = cp->c_next) {
                if (cp->c_time >= now && cp->c_time <= then) {
                        plog(XLOG_WARNING, "job %d rescheduled to run immediately", cp->c_id);
#ifdef DEBUG
                        dlog("rescheduling job %d back %d seconds",
                                cp->c_id, cp->c_time - now);
#endif
                        next_softclock = cp->c_time = now;
                }
        }
}

/*
 * Clock handler
 */
int softclock(P_void);
int softclock()
{
        time_t now;
        callout *cp;

        do {
                if (task_notify_todo)
                        do_task_notify();

                now = clocktime();

                /*
                 * While there are more callouts waiting...
                 */
                while ((cp = callouts.c_next) && cp->c_time <= now) {
                        /*
                         * Extract first from list, save fn & closure and
                         * unlink callout from list and free.
                         * Finally call function.
                         *
                         * The free is done first because
                         * it is quite common that the
                         * function will call timeout()
                         * and try to allocate a callout
                         */
                        void (*fn)() = cp->c_fn;
                        voidp closure = cp->c_closure;

                        callouts.c_next = cp->c_next;
                        free_callout(cp);
#ifdef DEBUG
                        /*dlog("Calling %#x(%#x)", fn, closure);*/
#endif /* DEBUG */
                        (*fn)(closure);
                }

        } while (task_notify_todo);

        /*
         * Return number of seconds to next event,
         * or 0 if there is no event.
         */
        if (cp = callouts.c_next)
                return cp->c_time - now;
        return 0;
}