source: rtems-libbsd/freebsd/sys/kern/kern_timeout.c @ a9e26f5

#include <machine/rtems-bsd-config.h>

/*-
 * Copyright (c) 1982, 1986, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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.
 * 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.
 *
 *      From: @(#)kern_clock.c  8.5 (Berkeley) 1/21/94
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <rtems/bsd/local/opt_kdtrace.h>

#include <rtems/bsd/sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/callout.h>
#include <sys/condvar.h>
#include <sys/interrupt.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <rtems/bsd/sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sdt.h>
#include <sys/sleepqueue.h>
#include <sys/sysctl.h>
#include <sys/smp.h>

#ifdef __rtems__
int ncallout = 16;
#endif /* __rtems__ */ 
SDT_PROVIDER_DEFINE(callout_execute);
SDT_PROBE_DEFINE(callout_execute, kernel, , callout_start);
SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_start, 0,
    "struct callout *");
SDT_PROBE_DEFINE(callout_execute, kernel, , callout_end); 
SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_end, 0,
    "struct callout *");

static int avg_depth;
SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
    "Average number of items examined per softclock call. Units = 1/1000");
static int avg_gcalls;
SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
    "Average number of Giant callouts made per softclock call. Units = 1/1000");
static int avg_lockcalls;
SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
    "Average number of lock callouts made per softclock call. Units = 1/1000");
static int avg_mpcalls;
SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
    "Average number of MP callouts made per softclock call. Units = 1/1000");
/*
 * TODO:
 *      allocate more timeout table slots when table overflows.
 */
int callwheelsize, callwheelbits, callwheelmask;

/*
 * There is one struct callout_cpu per cpu, holding all relevant
 * state for the callout processing thread on the individual CPU.
 * In particular:
 *      cc_ticks is incremented once per tick in callout_cpu().
 *      It tracks the global 'ticks' but in a way that the individual
 *      threads should not worry about races in the order in which
 *      hardclock() and hardclock_cpu() run on the various CPUs.
 *      cc_softclock is advanced in callout_cpu() to point to the
 *      first entry in cc_callwheel that may need handling. In turn,
 *      a softclock() is scheduled so it can serve the various entries i
 *      such that cc_softclock <= i <= cc_ticks .
 *      XXX maybe cc_softclock and cc_ticks should be volatile ?
 *
 *      cc_ticks is also used in callout_reset_cpu() to determine
 *      when the callout should be served.
 */
struct callout_cpu {
        struct mtx              cc_lock;
        struct callout          *cc_callout;
        struct callout_tailq    *cc_callwheel;
        struct callout_list     cc_callfree;
        struct callout          *cc_next;
        struct callout          *cc_curr;
        void                    *cc_cookie;
        int                     cc_ticks;
        int                     cc_softticks;
        int                     cc_cancel;
        int                     cc_waiting;
};

#ifdef SMP
struct callout_cpu cc_cpu[MAXCPU];
#define CC_CPU(cpu)     (&cc_cpu[(cpu)])
#define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
#else
struct callout_cpu cc_cpu;
#define CC_CPU(cpu)     &cc_cpu
#define CC_SELF()       &cc_cpu
#endif
#define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
#define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)

static int timeout_cpu;

MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");

/**
 * Locked by cc_lock:
 *   cc_curr         - If a callout is in progress, it is curr_callout.
 *                     If curr_callout is non-NULL, threads waiting in
 *                     callout_drain() will be woken up as soon as the
 *                     relevant callout completes.
 *   cc_cancel       - Changing to 1 with both callout_lock and c_lock held
 *                     guarantees that the current callout will not run.
 *                     The softclock() function sets this to 0 before it
 *                     drops callout_lock to acquire c_lock, and it calls
 *                     the handler only if curr_cancelled is still 0 after
 *                     c_lock is successfully acquired.
 *   cc_waiting      - If a thread is waiting in callout_drain(), then
 *                     callout_wait is nonzero.  Set only when
 *                     curr_callout is non-NULL.
 */

/*
 * kern_timeout_callwheel_alloc() - kernel low level callwheel initialization 
 *
 *      This code is called very early in the kernel initialization sequence,
 *      and may be called more then once.
 */
#ifdef __rtems__
static void rtems_bsd_timeout_init(void *);

static void
rtems_bsd_callout_timer(rtems_id id, void *arg)
{
        rtems_status_code sc;

        (void) arg;

        sc = rtems_timer_reset(id);
        BSD_ASSERT(sc == RTEMS_SUCCESSFUL);

        callout_tick();
}

static void callout_cpu_init(struct callout_cpu *);

SYSINIT(rtems_bsd_timeout, SI_SUB_VM, SI_ORDER_FIRST, rtems_bsd_timeout_init,
    NULL);

static void
rtems_bsd_timeout_init(void *unused)
#else /* __rtems__ */
caddr_t
kern_timeout_callwheel_alloc(caddr_t v)
#endif /* __rtems__ */
{
        struct callout_cpu *cc;
#ifdef __rtems__
        rtems_status_code sc;
        rtems_id id;
        caddr_t v;

        (void) unused;
#endif /* __rtems__ */

        timeout_cpu = PCPU_GET(cpuid);
        cc = CC_CPU(timeout_cpu);
        /*
         * Calculate callout wheel size
         */
        for (callwheelsize = 1, callwheelbits = 0;
             callwheelsize < ncallout;
             callwheelsize <<= 1, ++callwheelbits)
                ;
        callwheelmask = callwheelsize - 1;

#ifdef __rtems__
        v = malloc(ncallout * sizeof(*cc->cc_callout) + callwheelsize
            * sizeof(*cc->cc_callwheel), M_CALLOUT, M_ZERO | M_WAITOK);
#endif /* __rtems__ */
        cc->cc_callout = (struct callout *)v;
        v = (caddr_t)(cc->cc_callout + ncallout);
        cc->cc_callwheel = (struct callout_tailq *)v;
        v = (caddr_t)(cc->cc_callwheel + callwheelsize);
#ifndef __rtems__
        return(v);
#else /* __rtems__ */
        callout_cpu_init(cc);

        sc = rtems_timer_create(rtems_build_name('_', 'C', 'L', 'O'), &id);
        BSD_ASSERT(sc == RTEMS_SUCCESSFUL);

        sc = rtems_timer_server_fire_after(id, 1, rtems_bsd_callout_timer, NULL);
        BSD_ASSERT(sc == RTEMS_SUCCESSFUL);
#endif /* __rtems__ */
}

static void
callout_cpu_init(struct callout_cpu *cc)
{
        struct callout *c;
        int i;

        mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
        SLIST_INIT(&cc->cc_callfree);
        for (i = 0; i < callwheelsize; i++) {
                TAILQ_INIT(&cc->cc_callwheel[i]);
        }
        if (cc->cc_callout == NULL)
                return;
        for (i = 0; i < ncallout; i++) {
                c = &cc->cc_callout[i];
                callout_init(c, 0);
                c->c_flags = CALLOUT_LOCAL_ALLOC;
                SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
        }
}

#ifndef __rtems__
/*
 * kern_timeout_callwheel_init() - initialize previously reserved callwheel
 *                                 space.
 *
 *      This code is called just once, after the space reserved for the
 *      callout wheel has been finalized.
 */
void
kern_timeout_callwheel_init(void)
{
        callout_cpu_init(CC_CPU(timeout_cpu));
}
#endif /* __rtems__ */

/*
 * Start standard softclock thread.
 */
void    *softclock_ih;

static void
start_softclock(void *dummy)
{
        struct callout_cpu *cc;
#ifdef SMP
        int cpu;
#endif

        cc = CC_CPU(timeout_cpu);
        if (swi_add(&clk_intr_event, "clock", softclock, cc, SWI_CLOCK,
            INTR_MPSAFE, &softclock_ih))
                panic("died while creating standard software ithreads");
        cc->cc_cookie = softclock_ih;
#ifdef SMP
        for (cpu = 0; cpu <= mp_maxid; cpu++) {
                if (cpu == timeout_cpu)
                        continue;
                if (CPU_ABSENT(cpu))
                        continue;
                cc = CC_CPU(cpu);
                if (swi_add(NULL, "clock", softclock, cc, SWI_CLOCK,
                    INTR_MPSAFE, &cc->cc_cookie))
                        panic("died while creating standard software ithreads");
                cc->cc_callout = NULL;  /* Only cpu0 handles timeout(). */
                cc->cc_callwheel = malloc(
                    sizeof(struct callout_tailq) * callwheelsize, M_CALLOUT,
                    M_WAITOK);
                callout_cpu_init(cc);
        }
#endif
}

SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);

void
callout_tick(void)
{
        struct callout_cpu *cc;
        int need_softclock;
        int bucket;

        /*
         * Process callouts at a very low cpu priority, so we don't keep the
         * relatively high clock interrupt priority any longer than necessary.
         */
        need_softclock = 0;
        cc = CC_SELF();
        mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
        cc->cc_ticks++;
        for (; (cc->cc_softticks - cc->cc_ticks) <= 0; cc->cc_softticks++) {
                bucket = cc->cc_softticks & callwheelmask;
                if (!TAILQ_EMPTY(&cc->cc_callwheel[bucket])) {
                        need_softclock = 1;
                        break;
                }
        }
        mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
        /*
         * swi_sched acquires the thread lock, so we don't want to call it
         * with cc_lock held; incorrect locking order.
         */
        if (need_softclock)
                swi_sched(cc->cc_cookie, 0);
}

static struct callout_cpu *
callout_lock(struct callout *c)
{
        struct callout_cpu *cc;
        int cpu;

        for (;;) {
                cpu = c->c_cpu;
                cc = CC_CPU(cpu);
                CC_LOCK(cc);
                if (cpu == c->c_cpu)
                        break;
                CC_UNLOCK(cc);
        }
        return (cc);
}

/*
 * The callout mechanism is based on the work of Adam M. Costello and 
 * George Varghese, published in a technical report entitled "Redesigning
 * the BSD Callout and Timer Facilities" and modified slightly for inclusion
 * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
 * used in this implementation was published by G. Varghese and T. Lauck in
 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
 * the Efficient Implementation of a Timer Facility" in the Proceedings of
 * the 11th ACM Annual Symposium on Operating Systems Principles,
 * Austin, Texas Nov 1987.
 */

/*
 * Software (low priority) clock interrupt.
 * Run periodic events from timeout queue.
 */
void
softclock(void *arg)
{
        struct callout_cpu *cc;
        struct callout *c;
        struct callout_tailq *bucket;
        int curticks;
        int steps;      /* #steps since we last allowed interrupts */
        int depth;
        int mpcalls;
        int lockcalls;
        int gcalls;
#ifdef DIAGNOSTIC
        struct bintime bt1, bt2;
        struct timespec ts2;
        static uint64_t maxdt = 36893488147419102LL;    /* 2 msec */
        static timeout_t *lastfunc;
#endif

#ifndef MAX_SOFTCLOCK_STEPS
#define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
#endif /* MAX_SOFTCLOCK_STEPS */

        mpcalls = 0;
        lockcalls = 0;
        gcalls = 0;
        depth = 0;
        steps = 0;
        cc = (struct callout_cpu *)arg;
        CC_LOCK(cc);
        while (cc->cc_softticks - 1 != cc->cc_ticks) {
                /*
                 * cc_softticks may be modified by hard clock, so cache
                 * it while we work on a given bucket.
                 */
                curticks = cc->cc_softticks;
                cc->cc_softticks++;
                bucket = &cc->cc_callwheel[curticks & callwheelmask];
                c = TAILQ_FIRST(bucket);
                while (c) {
                        depth++;
                        if (c->c_time != curticks) {
                                c = TAILQ_NEXT(c, c_links.tqe);
                                ++steps;
                                if (steps >= MAX_SOFTCLOCK_STEPS) {
                                        cc->cc_next = c;
                                        /* Give interrupts a chance. */
                                        CC_UNLOCK(cc);
                                        ;       /* nothing */
                                        CC_LOCK(cc);
                                        c = cc->cc_next;
                                        steps = 0;
                                }
                        } else {
                                void (*c_func)(void *);
                                void *c_arg;
                                struct lock_class *class;
                                struct lock_object *c_lock;
                                int c_flags, sharedlock;

                                cc->cc_next = TAILQ_NEXT(c, c_links.tqe);
                                TAILQ_REMOVE(bucket, c, c_links.tqe);
                                class = (c->c_lock != NULL) ?
                                    LOCK_CLASS(c->c_lock) : NULL;
                                sharedlock = (c->c_flags & CALLOUT_SHAREDLOCK) ?
                                    0 : 1;
                                c_lock = c->c_lock;
                                c_func = c->c_func;
                                c_arg = c->c_arg;
                                c_flags = c->c_flags;
                                if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
                                        c->c_flags = CALLOUT_LOCAL_ALLOC;
                                } else {
                                        c->c_flags =
                                            (c->c_flags & ~CALLOUT_PENDING);
                                }
                                cc->cc_curr = c;
                                cc->cc_cancel = 0;
                                CC_UNLOCK(cc);
                                if (c_lock != NULL) {
                                        class->lc_lock(c_lock, sharedlock);
                                        /*
                                         * The callout may have been cancelled
                                         * while we switched locks.
                                         */
                                        if (cc->cc_cancel) {
                                                class->lc_unlock(c_lock);
                                                goto skip;
                                        }
                                        /* The callout cannot be stopped now. */
                                        cc->cc_cancel = 1;

                                        if (c_lock == &Giant.lock_object) {
                                                gcalls++;
                                                CTR3(KTR_CALLOUT,
                                                    "callout %p func %p arg %p",
                                                    c, c_func, c_arg);
                                        } else {
                                                lockcalls++;
                                                CTR3(KTR_CALLOUT, "callout lock"
                                                    " %p func %p arg %p",
                                                    c, c_func, c_arg);
                                        }
                                } else {
                                        mpcalls++;
                                        CTR3(KTR_CALLOUT,
                                            "callout mpsafe %p func %p arg %p",
                                            c, c_func, c_arg);
                                }
#ifdef DIAGNOSTIC
                                binuptime(&bt1);
#endif
#ifndef __rtems__
                                THREAD_NO_SLEEPING();
                                SDT_PROBE(callout_execute, kernel, ,
                                    callout_start, c, 0, 0, 0, 0);
#endif /* __rtems__ */ 
                                c_func(c_arg);
#ifndef __rtems__
                                SDT_PROBE(callout_execute, kernel, ,
                                    callout_end, c, 0, 0, 0, 0);
                                THREAD_SLEEPING_OK();
#endif /* __rtems__ */ 
#ifdef DIAGNOSTIC
                                binuptime(&bt2);
                                bintime_sub(&bt2, &bt1);
                                if (bt2.frac > maxdt) {
                                        if (lastfunc != c_func ||
                                            bt2.frac > maxdt * 2) {
                                                bintime2timespec(&bt2, &ts2);
                                                printf(
                        "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
                                                    c_func, c_arg,
                                                    (intmax_t)ts2.tv_sec,
                                                    ts2.tv_nsec);
                                        }
                                        maxdt = bt2.frac;
                                        lastfunc = c_func;
                                }
#endif
                                CTR1(KTR_CALLOUT, "callout %p finished", c);
                                if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
                                        class->lc_unlock(c_lock);
                        skip:
                                CC_LOCK(cc);
                                /*
                                 * If the current callout is locally
                                 * allocated (from timeout(9))
                                 * then put it on the freelist.
                                 *
                                 * Note: we need to check the cached
                                 * copy of c_flags because if it was not
                                 * local, then it's not safe to deref the
                                 * callout pointer.
                                 */
                                if (c_flags & CALLOUT_LOCAL_ALLOC) {
                                        KASSERT(c->c_flags ==
                                            CALLOUT_LOCAL_ALLOC,
                                            ("corrupted callout"));
                                        c->c_func = NULL;
                                        SLIST_INSERT_HEAD(&cc->cc_callfree, c,
                                            c_links.sle);
                                }
                                cc->cc_curr = NULL;
                                if (cc->cc_waiting) {
                                        /*
                                         * There is someone waiting
                                         * for the callout to complete.
                                         */
                                        cc->cc_waiting = 0;
                                        CC_UNLOCK(cc);
                                        wakeup(&cc->cc_waiting);
                                        CC_LOCK(cc);
                                }
                                steps = 0;
                                c = cc->cc_next;
                        }
                }
        }
        avg_depth += (depth * 1000 - avg_depth) >> 8;
        avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
        avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
        avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
        cc->cc_next = NULL;
        CC_UNLOCK(cc);
}

/*
 * timeout --
 *      Execute a function after a specified length of time.
 *
 * untimeout --
 *      Cancel previous timeout function call.
 *
 * callout_handle_init --
 *      Initialize a handle so that using it with untimeout is benign.
 *
 *      See AT&T BCI Driver Reference Manual for specification.  This
 *      implementation differs from that one in that although an 
 *      identification value is returned from timeout, the original
 *      arguments to timeout as well as the identifier are used to
 *      identify entries for untimeout.
 */
struct callout_handle
timeout(ftn, arg, to_ticks)
        timeout_t *ftn;
        void *arg;
        int to_ticks;
{
        struct callout_cpu *cc;
        struct callout *new;
        struct callout_handle handle;

        cc = CC_CPU(timeout_cpu);
        CC_LOCK(cc);
        /* Fill in the next free callout structure. */
        new = SLIST_FIRST(&cc->cc_callfree);
        if (new == NULL)
                /* XXX Attempt to malloc first */
                panic("timeout table full");
        SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
        callout_reset(new, to_ticks, ftn, arg);
        handle.callout = new;
        CC_UNLOCK(cc);

        return (handle);
}

void
untimeout(ftn, arg, handle)
        timeout_t *ftn;
        void *arg;
        struct callout_handle handle;
{
        struct callout_cpu *cc;

        /*
         * Check for a handle that was initialized
         * by callout_handle_init, but never used
         * for a real timeout.
         */
        if (handle.callout == NULL)
                return;

        cc = callout_lock(handle.callout);
        if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
                callout_stop(handle.callout);
        CC_UNLOCK(cc);
}

void
callout_handle_init(struct callout_handle *handle)
{
        handle->callout = NULL;
}

/*
 * New interface; clients allocate their own callout structures.
 *
 * callout_reset() - establish or change a timeout
 * callout_stop() - disestablish a timeout
 * callout_init() - initialize a callout structure so that it can
 *      safely be passed to callout_reset() and callout_stop()
 *
 * <sys/callout.h> defines three convenience macros:
 *
 * callout_active() - returns truth if callout has not been stopped,
 *      drained, or deactivated since the last time the callout was
 *      reset.
 * callout_pending() - returns truth if callout is still waiting for timeout
 * callout_deactivate() - marks the callout as having been serviced
 */
int
callout_reset_on(struct callout *c, int to_ticks, void (*ftn)(void *),
    void *arg, int cpu)
{
        struct callout_cpu *cc;
        int cancelled = 0;

        /*
         * Don't allow migration of pre-allocated callouts lest they
         * become unbalanced.
         */
        if (c->c_flags & CALLOUT_LOCAL_ALLOC)
                cpu = c->c_cpu;
retry:
        cc = callout_lock(c);
        if (cc->cc_curr == c) {
                /*
                 * We're being asked to reschedule a callout which is
                 * currently in progress.  If there is a lock then we
                 * can cancel the callout if it has not really started.
                 */
                if (c->c_lock != NULL && !cc->cc_cancel)
                        cancelled = cc->cc_cancel = 1;
                if (cc->cc_waiting) {
                        /*
                         * Someone has called callout_drain to kill this
                         * callout.  Don't reschedule.
                         */
                        CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
                            cancelled ? "cancelled" : "failed to cancel",
                            c, c->c_func, c->c_arg);
                        CC_UNLOCK(cc);
                        return (cancelled);
                }
        }
        if (c->c_flags & CALLOUT_PENDING) {
                if (cc->cc_next == c) {
                        cc->cc_next = TAILQ_NEXT(c, c_links.tqe);
                }
                TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c,
                    c_links.tqe);

                cancelled = 1;
                c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
        }
        /*
         * If the lock must migrate we have to check the state again as
         * we can't hold both the new and old locks simultaneously.
         */
        if (c->c_cpu != cpu) {
                c->c_cpu = cpu;
                CC_UNLOCK(cc);
                goto retry;
        }

        if (to_ticks <= 0)
                to_ticks = 1;

        c->c_arg = arg;
        c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
        c->c_func = ftn;
        c->c_time = cc->cc_ticks + to_ticks;
        TAILQ_INSERT_TAIL(&cc->cc_callwheel[c->c_time & callwheelmask], 
                          c, c_links.tqe);
        CTR5(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d",
            cancelled ? "re" : "", c, c->c_func, c->c_arg, to_ticks);
        CC_UNLOCK(cc);

        return (cancelled);
}

/*
 * Common idioms that can be optimized in the future.
 */
int
callout_schedule_on(struct callout *c, int to_ticks, int cpu)
{
        return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
}

int
callout_schedule(struct callout *c, int to_ticks)
{
        return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
}

int
_callout_stop_safe(c, safe)
        struct  callout *c;
        int     safe;
{
        struct callout_cpu *cc;
        struct lock_class *class;
#ifndef __rtems__
        int use_lock, sq_locked;
#else /* __rtems__ */
        int use_lock;
#endif /* __rtems__ */ 

        /*
         * Some old subsystems don't hold Giant while running a callout_stop(),
         * so just discard this check for the moment.
         */
        if (!safe && c->c_lock != NULL) {
                if (c->c_lock == &Giant.lock_object)
                        use_lock = mtx_owned(&Giant);
                else {
                        use_lock = 1;
                        class = LOCK_CLASS(c->c_lock);
                        class->lc_assert(c->c_lock, LA_XLOCKED);
                }
        } else
                use_lock = 0;

#ifndef __rtems__
        sq_locked = 0;
again:
#endif /* __rtems__ */ 
        cc = callout_lock(c);
        /*
         * If the callout isn't pending, it's not on the queue, so
         * don't attempt to remove it from the queue.  We can try to
         * stop it by other means however.
         */
        if (!(c->c_flags & CALLOUT_PENDING)) {
                c->c_flags &= ~CALLOUT_ACTIVE;

                /*
                 * If it wasn't on the queue and it isn't the current
                 * callout, then we can't stop it, so just bail.
                 */
                if (cc->cc_curr != c) {
                        CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
                            c, c->c_func, c->c_arg);
                        CC_UNLOCK(cc);
#ifndef __rtems__
                        if (sq_locked)
                                sleepq_release(&cc->cc_waiting);
#endif /* __rtems__ */ 
                        return (0);
                }

                if (safe) {
                        /*
                         * The current callout is running (or just
                         * about to run) and blocking is allowed, so
                         * just wait for the current invocation to
                         * finish.
                         */
                        while (cc->cc_curr == c) {
#ifndef __rtems__

                                /*
                                 * Use direct calls to sleepqueue interface
                                 * instead of cv/msleep in order to avoid
                                 * a LOR between cc_lock and sleepqueue
                                 * chain spinlocks.  This piece of code
                                 * emulates a msleep_spin() call actually.
                                 *
                                 * If we already have the sleepqueue chain
                                 * locked, then we can safely block.  If we
                                 * don't already have it locked, however,
                                 * we have to drop the cc_lock to lock
                                 * it.  This opens several races, so we
                                 * restart at the beginning once we have
                                 * both locks.  If nothing has changed, then
                                 * we will end up back here with sq_locked
                                 * set.
                                 */
                                if (!sq_locked) {
                                        CC_UNLOCK(cc);
                                        sleepq_lock(&cc->cc_waiting);
                                        sq_locked = 1;
                                        goto again;
                                }
                                cc->cc_waiting = 1;
                                DROP_GIANT();
                                CC_UNLOCK(cc);
                                sleepq_add(&cc->cc_waiting,
                                    &cc->cc_lock.lock_object, "codrain",
                                    SLEEPQ_SLEEP, 0);
                                sleepq_wait(&cc->cc_waiting, 0);
                                sq_locked = 0;

                                /* Reacquire locks previously released. */
                                PICKUP_GIANT();
                                CC_LOCK(cc);
#else /* __rtems__ */
                                BSD_ASSERT(0);
#endif /* __rtems__ */ 
                        }
                } else if (use_lock && !cc->cc_cancel) {
                        /*
                         * The current callout is waiting for its
                         * lock which we hold.  Cancel the callout
                         * and return.  After our caller drops the
                         * lock, the callout will be skipped in
                         * softclock().
                         */
                        cc->cc_cancel = 1;
                        CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
                            c, c->c_func, c->c_arg);
                        CC_UNLOCK(cc);
                        KASSERT(!sq_locked, ("sleepqueue chain locked"));
                        return (1);
                }
                CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
                    c, c->c_func, c->c_arg);
                CC_UNLOCK(cc);
                KASSERT(!sq_locked, ("sleepqueue chain still locked"));
                return (0);
        }
#ifndef __rtems__
        if (sq_locked)
                sleepq_release(&cc->cc_waiting);
#endif /* __rtems__ */ 

        c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);

        if (cc->cc_next == c) {
                cc->cc_next = TAILQ_NEXT(c, c_links.tqe);
        }
        TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c,
            c_links.tqe);

        CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
            c, c->c_func, c->c_arg);

        if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
                c->c_func = NULL;
                SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
        }
        CC_UNLOCK(cc);
        return (1);
}

void
callout_init(c, mpsafe)
        struct  callout *c;
        int mpsafe;
{
        bzero(c, sizeof *c);
        if (mpsafe) {
                c->c_lock = NULL;
                c->c_flags = CALLOUT_RETURNUNLOCKED;
        } else {
                c->c_lock = &Giant.lock_object;
                c->c_flags = 0;
        }
        c->c_cpu = timeout_cpu;
}

void
_callout_init_lock(c, lock, flags)
        struct  callout *c;
        struct  lock_object *lock;
        int flags;
{
        bzero(c, sizeof *c);
        c->c_lock = lock;
        KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
            ("callout_init_lock: bad flags %d", flags));
        KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
            ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
        KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
            (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
            __func__));
        c->c_flags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
        c->c_cpu = timeout_cpu;
}

#ifdef APM_FIXUP_CALLTODO
/* 
 * Adjust the kernel calltodo timeout list.  This routine is used after 
 * an APM resume to recalculate the calltodo timer list values with the 
 * number of hz's we have been sleeping.  The next hardclock() will detect 
 * that there are fired timers and run softclock() to execute them.
 *
 * Please note, I have not done an exhaustive analysis of what code this
 * might break.  I am motivated to have my select()'s and alarm()'s that
 * have expired during suspend firing upon resume so that the applications
 * which set the timer can do the maintanence the timer was for as close
 * as possible to the originally intended time.  Testing this code for a 
 * week showed that resuming from a suspend resulted in 22 to 25 timers 
 * firing, which seemed independant on whether the suspend was 2 hours or
 * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 */
void
adjust_timeout_calltodo(time_change)
    struct timeval *time_change;
{
        register struct callout *p;
        unsigned long delta_ticks;

        /* 
         * How many ticks were we asleep?
         * (stolen from tvtohz()).
         */

        /* Don't do anything */
        if (time_change->tv_sec < 0)
                return;
        else if (time_change->tv_sec <= LONG_MAX / 1000000)
                delta_ticks = (time_change->tv_sec * 1000000 +
                               time_change->tv_usec + (tick - 1)) / tick + 1;
        else if (time_change->tv_sec <= LONG_MAX / hz)
                delta_ticks = time_change->tv_sec * hz +
                              (time_change->tv_usec + (tick - 1)) / tick + 1;
        else
                delta_ticks = LONG_MAX;

        if (delta_ticks > INT_MAX)
                delta_ticks = INT_MAX;

        /* 
         * Now rip through the timer calltodo list looking for timers
         * to expire.
         */

        /* don't collide with softclock() */
        CC_LOCK(cc);
        for (p = calltodo.c_next; p != NULL; p = p->c_next) {
                p->c_time -= delta_ticks;

                /* Break if the timer had more time on it than delta_ticks */
                if (p->c_time > 0)
                        break;

                /* take back the ticks the timer didn't use (p->c_time <= 0) */
                delta_ticks = -p->c_time;
        }
        CC_UNLOCK(cc);

        return;
}
#endif /* APM_FIXUP_CALLTODO */