source: rtems-libbsd/freebsd/sys/kern/kern_timeout.c @ 3c967ca

#include <machine/rtems-bsd-kernel-space.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.
 * 3. 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_callout_profiling.h>
#include <rtems/bsd/local/opt_ddb.h>
#if defined(__arm__) || defined(__rtems__)
#include <rtems/bsd/local/opt_timer.h>
#endif
#include <rtems/bsd/local/opt_rss.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/callout.h>
#include <sys/file.h>
#include <sys/interrupt.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <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 DDB
#include <ddb/ddb.h>
#include <machine/_inttypes.h>
#endif

#ifdef SMP
#include <machine/cpu.h>
#endif

#ifndef NO_EVENTTIMERS
DPCPU_DECLARE(sbintime_t, hardclocktime);
#endif

SDT_PROVIDER_DEFINE(callout_execute);
SDT_PROBE_DEFINE1(callout_execute, , , callout__start, "struct callout *");
SDT_PROBE_DEFINE1(callout_execute, , , callout__end, "struct callout *");

#ifdef CALLOUT_PROFILING
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");
static int avg_depth_dir;
SYSCTL_INT(_debug, OID_AUTO, to_avg_depth_dir, CTLFLAG_RD, &avg_depth_dir, 0,
    "Average number of direct callouts examined per callout_process call. "
    "Units = 1/1000");
static int avg_lockcalls_dir;
SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls_dir, CTLFLAG_RD,
    &avg_lockcalls_dir, 0, "Average number of lock direct callouts made per "
    "callout_process call. Units = 1/1000");
static int avg_mpcalls_dir;
SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls_dir, CTLFLAG_RD, &avg_mpcalls_dir,
    0, "Average number of MP direct callouts made per callout_process call. "
    "Units = 1/1000");
#endif

#ifndef __rtems__
static int ncallout;
SYSCTL_INT(_kern, OID_AUTO, ncallout, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &ncallout, 0,
    "Number of entries in callwheel and size of timeout() preallocation");
#else /* __rtems__ */
#define ncallout 16
#endif /* __rtems__ */

#ifdef  RSS
static int pin_default_swi = 1;
static int pin_pcpu_swi = 1;
#else
static int pin_default_swi = 0;
static int pin_pcpu_swi = 0;
#endif

SYSCTL_INT(_kern, OID_AUTO, pin_default_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_default_swi,
    0, "Pin the default (non-per-cpu) swi (shared with PCPU 0 swi)");
SYSCTL_INT(_kern, OID_AUTO, pin_pcpu_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_pcpu_swi,
    0, "Pin the per-CPU swis (except PCPU 0, which is also default");

/*
 * TODO:
 *      allocate more timeout table slots when table overflows.
 */
u_int callwheelsize, callwheelmask;

/*
 * The callout cpu exec entities represent informations necessary for
 * describing the state of callouts currently running on the CPU and the ones
 * necessary for migrating callouts to the new callout cpu. In particular,
 * the first entry of the array cc_exec_entity holds informations for callout
 * running in SWI thread context, while the second one holds informations
 * for callout running directly from hardware interrupt context.
 * The cached informations are very important for deferring migration when
 * the migrating callout is already running.
 */
struct cc_exec {
        struct callout          *cc_curr;
        void                    (*cc_drain)(void *);
#ifdef SMP
        void                    (*ce_migration_func)(void *);
        void                    *ce_migration_arg;
        int                     ce_migration_cpu;
        sbintime_t              ce_migration_time;
        sbintime_t              ce_migration_prec;
#endif
        bool                    cc_cancel;
        bool                    cc_waiting;
};

/*
 * There is one struct callout_cpu per cpu, holding all relevant
 * state for the callout processing thread on the individual CPU.
 */
struct callout_cpu {
        struct mtx_padalign     cc_lock;
        struct cc_exec          cc_exec_entity[2];
        struct callout          *cc_next;
        struct callout          *cc_callout;
        struct callout_list     *cc_callwheel;
#ifndef __rtems__
        struct callout_tailq    cc_expireq;
#endif /* __rtems__ */
        struct callout_slist    cc_callfree;
        sbintime_t              cc_firstevent;
        sbintime_t              cc_lastscan;
        void                    *cc_cookie;
        u_int                   cc_bucket;
        u_int                   cc_inited;
        char                    cc_ktr_event_name[20];
};

#define callout_migrating(c)    ((c)->c_iflags & CALLOUT_DFRMIGRATION)

#define cc_exec_curr(cc, dir)           cc->cc_exec_entity[dir].cc_curr
#define cc_exec_drain(cc, dir)          cc->cc_exec_entity[dir].cc_drain
#define cc_exec_next(cc)                cc->cc_next
#define cc_exec_cancel(cc, dir)         cc->cc_exec_entity[dir].cc_cancel
#define cc_exec_waiting(cc, dir)        cc->cc_exec_entity[dir].cc_waiting
#ifdef SMP
#define cc_migration_func(cc, dir)      cc->cc_exec_entity[dir].ce_migration_func
#define cc_migration_arg(cc, dir)       cc->cc_exec_entity[dir].ce_migration_arg
#define cc_migration_cpu(cc, dir)       cc->cc_exec_entity[dir].ce_migration_cpu
#define cc_migration_time(cc, dir)      cc->cc_exec_entity[dir].ce_migration_time
#define cc_migration_prec(cc, dir)      cc->cc_exec_entity[dir].ce_migration_prec

struct callout_cpu cc_cpu[MAXCPU];
#define CPUBLOCK        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)
#define CC_LOCK_ASSERT(cc)      mtx_assert(&(cc)->cc_lock, MA_OWNED)

static int timeout_cpu;

static void     callout_cpu_init(struct callout_cpu *cc, int cpu);
static void     softclock_call_cc(struct callout *c, struct callout_cpu *cc,
#ifdef CALLOUT_PROFILING
                    int *mpcalls, int *lockcalls, int *gcalls,
#endif
                    int direct);

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

/**
 * Locked by cc_lock:
 *   cc_curr         - If a callout is in progress, it is cc_curr.
 *                     If cc_curr 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 cc_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
 *                     cc_lock is successfully acquired.
 *   cc_waiting      - If a thread is waiting in callout_drain(), then
 *                     callout_wait is nonzero.  Set only when
 *                     cc_curr is non-NULL.
 */

/*
 * Resets the execution entity tied to a specific callout cpu.
 */
static void
cc_cce_cleanup(struct callout_cpu *cc, int direct)
{

        cc_exec_curr(cc, direct) = NULL;
        cc_exec_cancel(cc, direct) = false;
        cc_exec_waiting(cc, direct) = false;
#ifdef SMP
        cc_migration_cpu(cc, direct) = CPUBLOCK;
        cc_migration_time(cc, direct) = 0;
        cc_migration_prec(cc, direct) = 0;
        cc_migration_func(cc, direct) = NULL;
        cc_migration_arg(cc, direct) = NULL;
#endif
}

/*
 * Checks if migration is requested by a specific callout cpu.
 */
static int
cc_cce_migrating(struct callout_cpu *cc, int direct)
{

#ifdef SMP
        return (cc_migration_cpu(cc, direct) != CPUBLOCK);
#else
        return (0);
#endif
}

/*
 * Kernel low level callwheel initialization
 * called on cpu0 during kernel startup.
 */
#ifdef __rtems__
static void rtems_bsd_timeout_init_early(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_process(sbinuptime());
}

static void
rtems_bsd_timeout_init_late(void *unused)
{
        rtems_status_code sc;
        rtems_id id;

        (void) unused;

        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);
}

SYSINIT(rtems_bsd_timeout_early, SI_SUB_VM, SI_ORDER_FIRST,
    rtems_bsd_timeout_init_early, NULL);

SYSINIT(rtems_bsd_timeout_late, SI_SUB_LAST, SI_ORDER_FIRST,
    rtems_bsd_timeout_init_late, NULL);

static void
rtems_bsd_timeout_init_early(void *dummy)
#else /* __rtems__ */
static void
callout_callwheel_init(void *dummy)
#endif /* __rtems__ */
{
        struct callout_cpu *cc;
#ifdef __rtems__
        (void) dummy;
#endif /* __rtems__ */

        /*
         * Calculate the size of the callout wheel and the preallocated
         * timeout() structures.
         * XXX: Clip callout to result of previous function of maxusers
         * maximum 384.  This is still huge, but acceptable.
         */
        memset(CC_CPU(0), 0, sizeof(cc_cpu));
#ifndef __rtems__
        ncallout = imin(16 + maxproc + maxfiles, 18508);
        TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
#endif /* __rtems__ */

        /*
         * Calculate callout wheel size, should be next power of two higher
         * than 'ncallout'.
         */
        callwheelsize = 1 << fls(ncallout);
        callwheelmask = callwheelsize - 1;

#ifndef __rtems__
        /*
         * Fetch whether we're pinning the swi's or not.
         */
        TUNABLE_INT_FETCH("kern.pin_default_swi", &pin_default_swi);
        TUNABLE_INT_FETCH("kern.pin_pcpu_swi", &pin_pcpu_swi);
#endif /* __rtems__ */

        /*
         * Only cpu0 handles timeout(9) and receives a preallocation.
         *
         * XXX: Once all timeout(9) consumers are converted this can
         * be removed.
         */
        timeout_cpu = PCPU_GET(cpuid);
        cc = CC_CPU(timeout_cpu);
        cc->cc_callout = malloc(ncallout * sizeof(struct callout),
            M_CALLOUT, M_WAITOK);
        callout_cpu_init(cc, timeout_cpu);
}
#ifndef __rtems__
SYSINIT(callwheel_init, SI_SUB_CPU, SI_ORDER_ANY, callout_callwheel_init, NULL);
#endif /* __rtems__ */

/*
 * Initialize the per-cpu callout structures.
 */
static void
callout_cpu_init(struct callout_cpu *cc, int cpu)
{
        struct callout *c;
        int i;

        mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
        SLIST_INIT(&cc->cc_callfree);
        cc->cc_inited = 1;
        cc->cc_callwheel = malloc(sizeof(struct callout_list) * callwheelsize,
            M_CALLOUT, M_WAITOK);
        for (i = 0; i < callwheelsize; i++)
                LIST_INIT(&cc->cc_callwheel[i]);
#ifndef __rtems__
        TAILQ_INIT(&cc->cc_expireq);
#endif /* __rtems__ */
        cc->cc_firstevent = SBT_MAX;
        for (i = 0; i < 2; i++)
                cc_cce_cleanup(cc, i);
        snprintf(cc->cc_ktr_event_name, sizeof(cc->cc_ktr_event_name),
            "callwheel cpu %d", cpu);
        if (cc->cc_callout == NULL)     /* Only cpu0 handles timeout(9) */
                return;
        for (i = 0; i < ncallout; i++) {
                c = &cc->cc_callout[i];
                callout_init(c, 0);
                c->c_iflags = CALLOUT_LOCAL_ALLOC;
                SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
        }
}

#ifdef SMP
/*
 * Switches the cpu tied to a specific callout.
 * The function expects a locked incoming callout cpu and returns with
 * locked outcoming callout cpu.
 */
static struct callout_cpu *
callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
{
        struct callout_cpu *new_cc;

        MPASS(c != NULL && cc != NULL);
        CC_LOCK_ASSERT(cc);

        /*
         * Avoid interrupts and preemption firing after the callout cpu
         * is blocked in order to avoid deadlocks as the new thread
         * may be willing to acquire the callout cpu lock.
         */
        c->c_cpu = CPUBLOCK;
        spinlock_enter();
        CC_UNLOCK(cc);
        new_cc = CC_CPU(new_cpu);
        CC_LOCK(new_cc);
        spinlock_exit();
        c->c_cpu = new_cpu;
        return (new_cc);
}
#endif

#ifndef __rtems__
/*
 * Start standard softclock thread.
 */
static void
start_softclock(void *dummy)
{
        struct callout_cpu *cc;
        char name[MAXCOMLEN];
#ifdef SMP
        int cpu;
        struct intr_event *ie;
#endif

        cc = CC_CPU(timeout_cpu);
        snprintf(name, sizeof(name), "clock (%d)", timeout_cpu);
        if (swi_add(&clk_intr_event, name, softclock, cc, SWI_CLOCK,
            INTR_MPSAFE, &cc->cc_cookie))
                panic("died while creating standard software ithreads");
        if (pin_default_swi &&
            (intr_event_bind(clk_intr_event, timeout_cpu) != 0)) {
                printf("%s: timeout clock couldn't be pinned to cpu %d\n",
                    __func__,
                    timeout_cpu);
        }

#ifdef SMP
        CPU_FOREACH(cpu) {
                if (cpu == timeout_cpu)
                        continue;
                cc = CC_CPU(cpu);
                cc->cc_callout = NULL;  /* Only cpu0 handles timeout(9). */
                callout_cpu_init(cc, cpu);
                snprintf(name, sizeof(name), "clock (%d)", cpu);
                ie = NULL;
                if (swi_add(&ie, name, softclock, cc, SWI_CLOCK,
                    INTR_MPSAFE, &cc->cc_cookie))
                        panic("died while creating standard software ithreads");
                if (pin_pcpu_swi && (intr_event_bind(ie, cpu) != 0)) {
                        printf("%s: per-cpu clock couldn't be pinned to "
                            "cpu %d\n",
                            __func__,
                            cpu);
                }
        }
#endif
}
SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
#endif /* __rtems__ */

#define CC_HASH_SHIFT   8

static inline u_int
callout_hash(sbintime_t sbt)
{

        return (sbt >> (32 - CC_HASH_SHIFT));
}

static inline u_int
callout_get_bucket(sbintime_t sbt)
{

        return (callout_hash(sbt) & callwheelmask);
}

void
callout_process(sbintime_t now)
{
        struct callout *tmp, *tmpn;
        struct callout_cpu *cc;
        struct callout_list *sc;
        sbintime_t first, last, max, tmp_max;
        uint32_t lookahead;
        u_int firstb, lastb, nowb;
#ifdef CALLOUT_PROFILING
        int depth_dir = 0, mpcalls_dir = 0, lockcalls_dir = 0;
#endif

        cc = CC_SELF();
        mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);

        /* Compute the buckets of the last scan and present times. */
        firstb = callout_hash(cc->cc_lastscan);
        cc->cc_lastscan = now;
        nowb = callout_hash(now);

        /* Compute the last bucket and minimum time of the bucket after it. */
        if (nowb == firstb)
                lookahead = (SBT_1S / 16);
        else if (nowb - firstb == 1)
                lookahead = (SBT_1S / 8);
        else
                lookahead = (SBT_1S / 2);
        first = last = now;
        first += (lookahead / 2);
        last += lookahead;
        last &= (0xffffffffffffffffLLU << (32 - CC_HASH_SHIFT));
        lastb = callout_hash(last) - 1;
        max = last;

        /*
         * Check if we wrapped around the entire wheel from the last scan.
         * In case, we need to scan entirely the wheel for pending callouts.
         */
        if (lastb - firstb >= callwheelsize) {
                lastb = firstb + callwheelsize - 1;
                if (nowb - firstb >= callwheelsize)
                        nowb = lastb;
        }

        /* Iterate callwheel from firstb to nowb and then up to lastb. */
        do {
                sc = &cc->cc_callwheel[firstb & callwheelmask];
                tmp = LIST_FIRST(sc);
                while (tmp != NULL) {
                        /* Run the callout if present time within allowed. */
                        if (tmp->c_time <= now) {
#ifndef __rtems__
                                /*
                                 * Consumer told us the callout may be run
                                 * directly from hardware interrupt context.
                                 */
                                if (tmp->c_iflags & CALLOUT_DIRECT) {
#endif /* __rtems__ */
#ifdef CALLOUT_PROFILING
                                        ++depth_dir;
#endif
                                        cc_exec_next(cc) =
                                            LIST_NEXT(tmp, c_links.le);
                                        cc->cc_bucket = firstb & callwheelmask;
                                        LIST_REMOVE(tmp, c_links.le);
                                        softclock_call_cc(tmp, cc,
#ifdef CALLOUT_PROFILING
                                            &mpcalls_dir, &lockcalls_dir, NULL,
#endif
                                            1);
                                        tmp = cc_exec_next(cc);
                                        cc_exec_next(cc) = NULL;
#ifndef __rtems__
                                } else {
                                        tmpn = LIST_NEXT(tmp, c_links.le);
                                        LIST_REMOVE(tmp, c_links.le);
                                        TAILQ_INSERT_TAIL(&cc->cc_expireq,
                                            tmp, c_links.tqe);
                                        tmp->c_iflags |= CALLOUT_PROCESSED;
                                        tmp = tmpn;
                                }
#endif /* __rtems__ */
                                continue;
                        }
                        /* Skip events from distant future. */
                        if (tmp->c_time >= max)
                                goto next;
                        /*
                         * Event minimal time is bigger than present maximal
                         * time, so it cannot be aggregated.
                         */
                        if (tmp->c_time > last) {
                                lastb = nowb;
                                goto next;
                        }
                        /* Update first and last time, respecting this event. */
                        if (tmp->c_time < first)
                                first = tmp->c_time;
                        tmp_max = tmp->c_time + tmp->c_precision;
                        if (tmp_max < last)
                                last = tmp_max;
next:
                        tmp = LIST_NEXT(tmp, c_links.le);
                }
                /* Proceed with the next bucket. */
                firstb++;
                /*
                 * Stop if we looked after present time and found
                 * some event we can't execute at now.
                 * Stop if we looked far enough into the future.
                 */
        } while (((int)(firstb - lastb)) <= 0);
        cc->cc_firstevent = last;
#ifndef NO_EVENTTIMERS
        cpu_new_callout(curcpu, last, first);
#endif
#ifdef CALLOUT_PROFILING
        avg_depth_dir += (depth_dir * 1000 - avg_depth_dir) >> 8;
        avg_mpcalls_dir += (mpcalls_dir * 1000 - avg_mpcalls_dir) >> 8;
        avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
#endif
        mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
#ifndef __rtems__
        /*
         * swi_sched acquires the thread lock, so we don't want to call it
         * with cc_lock held; incorrect locking order.
         */
        if (!TAILQ_EMPTY(&cc->cc_expireq))
                swi_sched(cc->cc_cookie, 0);
#endif /* __rtems__ */
}

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

        for (;;) {
                cpu = c->c_cpu;
#ifdef SMP
                if (cpu == CPUBLOCK) {
                        while (c->c_cpu == CPUBLOCK)
                                cpu_spinwait();
                        continue;
                }
#endif
                cc = CC_CPU(cpu);
                CC_LOCK(cc);
                if (cpu == c->c_cpu)
                        break;
                CC_UNLOCK(cc);
        }
        return (cc);
}

static void
callout_cc_add(struct callout *c, struct callout_cpu *cc,
    sbintime_t sbt, sbintime_t precision, void (*func)(void *),
    void *arg, int cpu, int flags)
{
        int bucket;

        CC_LOCK_ASSERT(cc);
        if (sbt < cc->cc_lastscan)
                sbt = cc->cc_lastscan;
        c->c_arg = arg;
        c->c_iflags |= CALLOUT_PENDING;
        c->c_iflags &= ~CALLOUT_PROCESSED;
        c->c_flags |= CALLOUT_ACTIVE;
        if (flags & C_DIRECT_EXEC)
                c->c_iflags |= CALLOUT_DIRECT;
        c->c_func = func;
        c->c_time = sbt;
        c->c_precision = precision;
        bucket = callout_get_bucket(c->c_time);
        CTR3(KTR_CALLOUT, "precision set for %p: %d.%08x",
            c, (int)(c->c_precision >> 32),
            (u_int)(c->c_precision & 0xffffffff));
        LIST_INSERT_HEAD(&cc->cc_callwheel[bucket], c, c_links.le);
        if (cc->cc_bucket == bucket)
                cc_exec_next(cc) = c;
#ifndef NO_EVENTTIMERS
        /*
         * Inform the eventtimers(4) subsystem there's a new callout
         * that has been inserted, but only if really required.
         */
        if (SBT_MAX - c->c_time < c->c_precision)
                c->c_precision = SBT_MAX - c->c_time;
        sbt = c->c_time + c->c_precision;
        if (sbt < cc->cc_firstevent) {
                cc->cc_firstevent = sbt;
                cpu_new_callout(cpu, sbt, c->c_time);
        }
#endif
}

static void
callout_cc_del(struct callout *c, struct callout_cpu *cc)
{

        if ((c->c_iflags & CALLOUT_LOCAL_ALLOC) == 0)
                return;
        c->c_func = NULL;
        SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
}

static void
softclock_call_cc(struct callout *c, struct callout_cpu *cc,
#ifdef CALLOUT_PROFILING
    int *mpcalls, int *lockcalls, int *gcalls,
#endif
    int direct)
{
#ifndef __rtems__
        struct rm_priotracker tracker;
#endif /* __rtems__ */
        void (*c_func)(void *);
        void *c_arg;
        struct lock_class *class;
        struct lock_object *c_lock;
        uintptr_t lock_status;
        int c_iflags;
#ifdef SMP
        struct callout_cpu *new_cc;
        void (*new_func)(void *);
        void *new_arg;
        int flags, new_cpu;
        sbintime_t new_prec, new_time;
#endif
#if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING) 
        sbintime_t sbt1, sbt2;
        struct timespec ts2;
        static sbintime_t maxdt = 2 * SBT_1MS;  /* 2 msec */
        static timeout_t *lastfunc;
#endif

        KASSERT((c->c_iflags & CALLOUT_PENDING) == CALLOUT_PENDING,
            ("softclock_call_cc: pend %p %x", c, c->c_iflags));
        KASSERT((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE,
            ("softclock_call_cc: act %p %x", c, c->c_flags));
        class = (c->c_lock != NULL) ? LOCK_CLASS(c->c_lock) : NULL;
        lock_status = 0;
        if (c->c_flags & CALLOUT_SHAREDLOCK) {
#ifndef __rtems__
                if (class == &lock_class_rm)
                        lock_status = (uintptr_t)&tracker;
                else
#endif /* __rtems__ */
                        lock_status = 1;
        }
        c_lock = c->c_lock;
        c_func = c->c_func;
        c_arg = c->c_arg;
        c_iflags = c->c_iflags;
        if (c->c_iflags & CALLOUT_LOCAL_ALLOC)
                c->c_iflags = CALLOUT_LOCAL_ALLOC;
        else
                c->c_iflags &= ~CALLOUT_PENDING;
        
        cc_exec_curr(cc, direct) = c;
        cc_exec_cancel(cc, direct) = false;
        cc_exec_drain(cc, direct) = NULL;
        CC_UNLOCK(cc);
        if (c_lock != NULL) {
                class->lc_lock(c_lock, lock_status);
                /*
                 * The callout may have been cancelled
                 * while we switched locks.
                 */
                if (cc_exec_cancel(cc, direct)) {
                        class->lc_unlock(c_lock);
                        goto skip;
                }
                /* The callout cannot be stopped now. */
                cc_exec_cancel(cc, direct) = true;
                if (c_lock == &Giant.lock_object) {
#ifdef CALLOUT_PROFILING
                        (*gcalls)++;
#endif
                        CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
                            c, c_func, c_arg);
                } else {
#ifdef CALLOUT_PROFILING
                        (*lockcalls)++;
#endif
                        CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
                            c, c_func, c_arg);
                }
        } else {
#ifdef CALLOUT_PROFILING
                (*mpcalls)++;
#endif
                CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
                    c, c_func, c_arg);
        }
        KTR_STATE3(KTR_SCHED, "callout", cc->cc_ktr_event_name, "running",
            "func:%p", c_func, "arg:%p", c_arg, "direct:%d", direct);
#if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
        sbt1 = sbinuptime();
#endif
#ifndef __rtems__
        THREAD_NO_SLEEPING();
        SDT_PROBE1(callout_execute, , , callout__start, c);
#endif /* __rtems__ */
        c_func(c_arg);
#ifndef __rtems__
        SDT_PROBE1(callout_execute, , , callout__end, c);
        THREAD_SLEEPING_OK();
#endif /* __rtems__ */
#if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
        sbt2 = sbinuptime();
        sbt2 -= sbt1;
        if (sbt2 > maxdt) {
                if (lastfunc != c_func || sbt2 > maxdt * 2) {
                        ts2 = sbttots(sbt2);
                        printf(
                "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
                            c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
                }
                maxdt = sbt2;
                lastfunc = c_func;
        }
#endif
        KTR_STATE0(KTR_SCHED, "callout", cc->cc_ktr_event_name, "idle");
        CTR1(KTR_CALLOUT, "callout %p finished", c);
        if ((c_iflags & CALLOUT_RETURNUNLOCKED) == 0)
                class->lc_unlock(c_lock);
skip:
        CC_LOCK(cc);
        KASSERT(cc_exec_curr(cc, direct) == c, ("mishandled cc_curr"));
        cc_exec_curr(cc, direct) = NULL;
        if (cc_exec_drain(cc, direct)) {
                void (*drain)(void *);
                
                drain = cc_exec_drain(cc, direct);
                cc_exec_drain(cc, direct) = NULL;
                CC_UNLOCK(cc);
                drain(c_arg);
                CC_LOCK(cc);
        }
        if (cc_exec_waiting(cc, direct)) {
                /*
                 * There is someone waiting for the
                 * callout to complete.
                 * If the callout was scheduled for
                 * migration just cancel it.
                 */
                if (cc_cce_migrating(cc, direct)) {
                        cc_cce_cleanup(cc, direct);

                        /*
                         * It should be assert here that the callout is not
                         * destroyed but that is not easy.
                         */
                        c->c_iflags &= ~CALLOUT_DFRMIGRATION;
                }
                cc_exec_waiting(cc, direct) = false;
                CC_UNLOCK(cc);
                wakeup(&cc_exec_waiting(cc, direct));
                CC_LOCK(cc);
        } else if (cc_cce_migrating(cc, direct)) {
                KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0,
                    ("Migrating legacy callout %p", c));
#ifdef SMP
                /*
                 * If the callout was scheduled for
                 * migration just perform it now.
                 */
                new_cpu = cc_migration_cpu(cc, direct);
                new_time = cc_migration_time(cc, direct);
                new_prec = cc_migration_prec(cc, direct);
                new_func = cc_migration_func(cc, direct);
                new_arg = cc_migration_arg(cc, direct);
                cc_cce_cleanup(cc, direct);

                /*
                 * It should be assert here that the callout is not destroyed
                 * but that is not easy.
                 *
                 * As first thing, handle deferred callout stops.
                 */
                if (!callout_migrating(c)) {
                        CTR3(KTR_CALLOUT,
                             "deferred cancelled %p func %p arg %p",
                             c, new_func, new_arg);
                        callout_cc_del(c, cc);
                        return;
                }
                c->c_iflags &= ~CALLOUT_DFRMIGRATION;

                new_cc = callout_cpu_switch(c, cc, new_cpu);
                flags = (direct) ? C_DIRECT_EXEC : 0;
                callout_cc_add(c, new_cc, new_time, new_prec, new_func,
                    new_arg, new_cpu, flags);
                CC_UNLOCK(new_cc);
                CC_LOCK(cc);
#else
                panic("migration should not happen");
#endif
        }
        /*
         * 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_iflags because
         * if it was not local, then it's not safe to deref the
         * callout pointer.
         */
        KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0 ||
            c->c_iflags == CALLOUT_LOCAL_ALLOC,
            ("corrupted callout"));
        if (c_iflags & CALLOUT_LOCAL_ALLOC)
                callout_cc_del(c, 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.
 */

#ifndef __rtems__
/*
 * Software (low priority) clock interrupt.
 * Run periodic events from timeout queue.
 */
void
softclock(void *arg)
{
        struct callout_cpu *cc;
        struct callout *c;
#ifdef CALLOUT_PROFILING
        int depth = 0, gcalls = 0, lockcalls = 0, mpcalls = 0;
#endif

        cc = (struct callout_cpu *)arg;
        CC_LOCK(cc);
        while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
                TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
                softclock_call_cc(c, cc,
#ifdef CALLOUT_PROFILING
                    &mpcalls, &lockcalls, &gcalls,
#endif
                    0);
#ifdef CALLOUT_PROFILING
                ++depth;
#endif
        }
#ifdef CALLOUT_PROFILING
        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;
#endif
        CC_UNLOCK(cc);
}
#endif /* __rtems__ */

/*
 * 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(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(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;
}

void
callout_when(sbintime_t sbt, sbintime_t precision, int flags,
    sbintime_t *res, sbintime_t *prec_res)
{
        sbintime_t to_sbt, to_pr;

        if ((flags & (C_ABSOLUTE | C_PRECALC)) != 0) {
                *res = sbt;
                *prec_res = precision;
                return;
        }
        if ((flags & C_HARDCLOCK) != 0 && sbt < tick_sbt)
                sbt = tick_sbt;
        if ((flags & C_HARDCLOCK) != 0 ||
#ifdef NO_EVENTTIMERS
            sbt >= sbt_timethreshold) {
                to_sbt = getsbinuptime();

                /* Add safety belt for the case of hz > 1000. */
                to_sbt += tc_tick_sbt - tick_sbt;
#else
            sbt >= sbt_tickthreshold) {
                /*
                 * Obtain the time of the last hardclock() call on
                 * this CPU directly from the kern_clocksource.c.
                 * This value is per-CPU, but it is equal for all
                 * active ones.
                 */
#ifdef __LP64__
                to_sbt = DPCPU_GET(hardclocktime);
#else
                spinlock_enter();
                to_sbt = DPCPU_GET(hardclocktime);
                spinlock_exit();
#endif
#endif
                if (cold && to_sbt == 0)
                        to_sbt = sbinuptime();
                if ((flags & C_HARDCLOCK) == 0)
                        to_sbt += tick_sbt;
        } else
                to_sbt = sbinuptime();
        if (SBT_MAX - to_sbt < sbt)
                to_sbt = SBT_MAX;
        else
                to_sbt += sbt;
        *res = to_sbt;
        to_pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
            sbt >> C_PRELGET(flags));
        *prec_res = to_pr > precision ? to_pr : precision;
}

/*
 * 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_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t prec,
    void (*ftn)(void *), void *arg, int cpu, int flags)
{
        sbintime_t to_sbt, precision;
        struct callout_cpu *cc;
        int cancelled, direct;
        int ignore_cpu=0;

        cancelled = 0;
        if (cpu == -1) {
                ignore_cpu = 1;
        } else if ((cpu >= MAXCPU) ||
                   ((CC_CPU(cpu))->cc_inited == 0)) {
                /* Invalid CPU spec */
                panic("Invalid CPU in callout %d", cpu);
        }
        callout_when(sbt, prec, flags, &to_sbt, &precision);

        /* 
         * This flag used to be added by callout_cc_add, but the
         * first time you call this we could end up with the
         * wrong direct flag if we don't do it before we add.
         */
        if (flags & C_DIRECT_EXEC) {
                direct = 1;
        } else {
                direct = 0;
        }
        KASSERT(!direct || c->c_lock == NULL,
            ("%s: direct callout %p has lock", __func__, c));
        cc = callout_lock(c);
        /*
         * Don't allow migration of pre-allocated callouts lest they
         * become unbalanced or handle the case where the user does
         * not care. 
         */
        if ((c->c_iflags & CALLOUT_LOCAL_ALLOC) ||
            ignore_cpu) {
                cpu = c->c_cpu;
        }

        if (cc_exec_curr(cc, direct) == 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_exec_cancel(cc, direct))
                        cancelled = cc_exec_cancel(cc, direct) = true;
                if (cc_exec_waiting(cc, direct) || cc_exec_drain(cc, direct)) {
                        /*
                         * 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);
                }
#ifdef SMP
                if (callout_migrating(c)) {
                        /* 
                         * This only occurs when a second callout_reset_sbt_on
                         * is made after a previous one moved it into
                         * deferred migration (below). Note we do *not* change
                         * the prev_cpu even though the previous target may
                         * be different.
                         */
                        cc_migration_cpu(cc, direct) = cpu;
                        cc_migration_time(cc, direct) = to_sbt;
                        cc_migration_prec(cc, direct) = precision;
                        cc_migration_func(cc, direct) = ftn;
                        cc_migration_arg(cc, direct) = arg;
                        cancelled = 1;
                        CC_UNLOCK(cc);
                        return (cancelled);
                }
#endif
        }
        if (c->c_iflags & CALLOUT_PENDING) {
#ifndef __rtems__
                if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
#endif /* __rtems__ */
                        if (cc_exec_next(cc) == c)
                                cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
                        LIST_REMOVE(c, c_links.le);
#ifndef __rtems__
                } else {
                        TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
                }
#endif /* __rtems__ */
                cancelled = 1;
                c->c_iflags &= ~ CALLOUT_PENDING;
                c->c_flags &= ~ CALLOUT_ACTIVE;
        }

#ifdef SMP
        /*
         * If the callout must migrate try to perform it immediately.
         * If the callout is currently running, just defer the migration
         * to a more appropriate moment.
         */
        if (c->c_cpu != cpu) {
                if (cc_exec_curr(cc, direct) == c) {
                        /* 
                         * Pending will have been removed since we are
                         * actually executing the callout on another
                         * CPU. That callout should be waiting on the
                         * lock the caller holds. If we set both
                         * active/and/pending after we return and the
                         * lock on the executing callout proceeds, it
                         * will then see pending is true and return.
                         * At the return from the actual callout execution
                         * the migration will occur in softclock_call_cc
                         * and this new callout will be placed on the 
                         * new CPU via a call to callout_cpu_switch() which
                         * will get the lock on the right CPU followed
                         * by a call callout_cc_add() which will add it there.
                         * (see above in softclock_call_cc()).
                         */
                        cc_migration_cpu(cc, direct) = cpu;
                        cc_migration_time(cc, direct) = to_sbt;
                        cc_migration_prec(cc, direct) = precision;
                        cc_migration_func(cc, direct) = ftn;
                        cc_migration_arg(cc, direct) = arg;
                        c->c_iflags |= (CALLOUT_DFRMIGRATION | CALLOUT_PENDING);
                        c->c_flags |= CALLOUT_ACTIVE;
                        CTR6(KTR_CALLOUT,
                    "migration of %p func %p arg %p in %d.%08x to %u deferred",
                            c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
                            (u_int)(to_sbt & 0xffffffff), cpu);
                        CC_UNLOCK(cc);
                        return (cancelled);
                }
                cc = callout_cpu_switch(c, cc, cpu);
        }
#endif

        callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
        CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
            cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
            (u_int)(to_sbt & 0xffffffff));
        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(struct callout *c, int flags, void (*drain)(void *))
{
        struct callout_cpu *cc, *old_cc;
        struct lock_class *class;
        int direct, sq_locked, use_lock;
        int cancelled, not_on_a_list;
#ifdef __rtems__
        (void)old_cc;
        (void)sq_locked;
#endif /* __rtems__ */

        if ((flags & CS_DRAIN) != 0)
                WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
                    "calling %s", __func__);

        /*
         * Some old subsystems don't hold Giant while running a callout_stop(),
         * so just discard this check for the moment.
         */
        if ((flags & CS_DRAIN) == 0 && 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;
        if (c->c_iflags & CALLOUT_DIRECT) {
                direct = 1;
        } else {
                direct = 0;
        }

#ifndef __rtems__
        sq_locked = 0;
        old_cc = NULL;
again:
#endif /* __rtems__ */
        cc = callout_lock(c);

        if ((c->c_iflags & (CALLOUT_DFRMIGRATION | CALLOUT_PENDING)) ==
            (CALLOUT_DFRMIGRATION | CALLOUT_PENDING) &&
            ((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE)) {
                /*
                 * Special case where this slipped in while we
                 * were migrating *as* the callout is about to
                 * execute. The caller probably holds the lock
                 * the callout wants.
                 *
                 * Get rid of the migration first. Then set
                 * the flag that tells this code *not* to
                 * try to remove it from any lists (its not
                 * on one yet). When the callout wheel runs,
                 * it will ignore this callout.
                 */
                c->c_iflags &= ~CALLOUT_PENDING;
                c->c_flags &= ~CALLOUT_ACTIVE;
                not_on_a_list = 1;
        } else {
                not_on_a_list = 0;
        }

#ifndef __rtems__
        /*
         * If the callout was migrating while the callout cpu lock was
         * dropped,  just drop the sleepqueue lock and check the states
         * again.
         */
        if (sq_locked != 0 && cc != old_cc) {
#ifdef SMP
                CC_UNLOCK(cc);
                sleepq_release(&cc_exec_waiting(old_cc, direct));
                sq_locked = 0;
                old_cc = NULL;
                goto again;
#else
                panic("migration should not happen");
#endif
        }
#endif /* __rtems__ */

        /*
         * If the callout is running, try to stop it or drain it.
         */
        if (cc_exec_curr(cc, direct) == c) {
                /*
                 * Succeed we to stop it or not, we must clear the
                 * active flag - this is what API users expect.  If we're
                 * draining and the callout is currently executing, first wait
                 * until it finishes.
                 */
                if ((flags & CS_DRAIN) == 0)
                        c->c_flags &= ~CALLOUT_ACTIVE;

                if ((flags & CS_DRAIN) != 0) {
                        /*
                         * 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_exec_curr(cc, direct) == 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_exec_waiting(cc, direct));
                                        sq_locked = 1;
                                        old_cc = cc;
                                        goto again;
                                }

                                /*
                                 * Migration could be cancelled here, but
                                 * as long as it is still not sure when it
                                 * will be packed up, just let softclock()
                                 * take care of it.
                                 */
                                cc_exec_waiting(cc, direct) = true;
                                DROP_GIANT();
                                CC_UNLOCK(cc);
                                sleepq_add(
                                    &cc_exec_waiting(cc, direct),
                                    &cc->cc_lock.lock_object, "codrain",
                                    SLEEPQ_SLEEP, 0);
                                sleepq_wait(
                                    &cc_exec_waiting(cc, direct),
                                             0);
                                sq_locked = 0;
                                old_cc = NULL;

                                /* Reacquire locks previously released. */
                                PICKUP_GIANT();
                                CC_LOCK(cc);
#else /* __rtems__ */
                                /*
                                 * On RTEMS the LOR problem above does not
                                 * exist since here we do not use
                                 * sleepq_set_timeout() and instead use the
                                 * RTEMS watchdog.
                                 */
                                cc_exec_waiting(cc, direct) = true;
                                msleep_spin(&cc_exec_waiting(cc, direct),
                                    &cc->cc_lock, "codrain", 0);
#endif /* __rtems__ */
                        }
                        c->c_flags &= ~CALLOUT_ACTIVE;
                } else if (use_lock &&
                           !cc_exec_cancel(cc, direct) && (drain == NULL)) {
                        
                        /*
                         * 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(). This *only* works with a
                         * callout_stop() *not* callout_drain() or
                         * callout_async_drain().
                         */
                        cc_exec_cancel(cc, direct) = true;
                        CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
                            c, c->c_func, c->c_arg);
                        KASSERT(!cc_cce_migrating(cc, direct),
                            ("callout wrongly scheduled for migration"));
                        if (callout_migrating(c)) {
                                c->c_iflags &= ~CALLOUT_DFRMIGRATION;
#ifdef SMP
                                cc_migration_cpu(cc, direct) = CPUBLOCK;
                                cc_migration_time(cc, direct) = 0;
                                cc_migration_prec(cc, direct) = 0;
                                cc_migration_func(cc, direct) = NULL;
                                cc_migration_arg(cc, direct) = NULL;
#endif
                        }
                        CC_UNLOCK(cc);
#ifndef __rtems__
                        KASSERT(!sq_locked, ("sleepqueue chain locked"));
#endif /* __rtems__ */
                        return (1);
                } else if (callout_migrating(c)) {
                        /*
                         * The callout is currently being serviced
                         * and the "next" callout is scheduled at
                         * its completion with a migration. We remove
                         * the migration flag so it *won't* get rescheduled,
                         * but we can't stop the one thats running so
                         * we return 0.
                         */
                        c->c_iflags &= ~CALLOUT_DFRMIGRATION;
#ifdef SMP
                        /* 
                         * We can't call cc_cce_cleanup here since
                         * if we do it will remove .ce_curr and
                         * its still running. This will prevent a
                         * reschedule of the callout when the 
                         * execution completes.
                         */
                        cc_migration_cpu(cc, direct) = CPUBLOCK;
                        cc_migration_time(cc, direct) = 0;
                        cc_migration_prec(cc, direct) = 0;
                        cc_migration_func(cc, direct) = NULL;
                        cc_migration_arg(cc, direct) = NULL;
#endif
                        CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
                            c, c->c_func, c->c_arg);
                        if (drain) {
                                cc_exec_drain(cc, direct) = drain;
                        }
                        CC_UNLOCK(cc);
                        return ((flags & CS_EXECUTING) != 0);
                }
                CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
                    c, c->c_func, c->c_arg);
                if (drain) {
                        cc_exec_drain(cc, direct) = drain;
                }
#ifndef __rtems__
                KASSERT(!sq_locked, ("sleepqueue chain still locked"));
#endif /* __rtems__ */
                cancelled = ((flags & CS_EXECUTING) != 0);
        } else
                cancelled = 1;

#ifndef __rtems__
        if (sq_locked)
                sleepq_release(&cc_exec_waiting(cc, direct));
#endif /* __rtems__ */

        if ((c->c_iflags & CALLOUT_PENDING) == 0) {
                CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
                    c, c->c_func, c->c_arg);
                /*
                 * For not scheduled and not executing callout return
                 * negative value.
                 */
                if (cc_exec_curr(cc, direct) != c)
                        cancelled = -1;
                CC_UNLOCK(cc);
                return (cancelled);
        }

        c->c_iflags &= ~CALLOUT_PENDING;
        c->c_flags &= ~CALLOUT_ACTIVE;

        CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
            c, c->c_func, c->c_arg);
        if (not_on_a_list == 0) {
#ifndef __rtems__
                if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
#endif /* __rtems__ */
                        if (cc_exec_next(cc) == c)
                                cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
                        LIST_REMOVE(c, c_links.le);
#ifndef __rtems__
                } else {
                        TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
                }
#endif /* __rtems__ */
        }
        callout_cc_del(c, cc);
        CC_UNLOCK(cc);
        return (cancelled);
}

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

void
_callout_init_lock(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_iflags = 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 independent on whether the suspend was 2 hours or
 * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 */
void
adjust_timeout_calltodo(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 = howmany(time_change->tv_sec * 1000000 +
                    time_change->tv_usec, tick) + 1;
        else if (time_change->tv_sec <= LONG_MAX / hz)
                delta_ticks = time_change->tv_sec * hz +
                    howmany(time_change->tv_usec, 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 */

static int
flssbt(sbintime_t sbt)
{

        sbt += (uint64_t)sbt >> 1;
        if (sizeof(long) >= sizeof(sbintime_t))
                return (flsl(sbt));
        if (sbt >= SBT_1S)
                return (flsl(((uint64_t)sbt) >> 32) + 32);
        return (flsl(sbt));
}

/*
 * Dump immediate statistic snapshot of the scheduled callouts.
 */
static int
sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
{
        struct callout *tmp;
        struct callout_cpu *cc;
        struct callout_list *sc;
        sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
        int ct[64], cpr[64], ccpbk[32];
        int error, val, i, count, tcum, pcum, maxc, c, medc;
#ifdef SMP
        int cpu;
#endif

        val = 0;
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        count = maxc = 0;
        st = spr = maxt = maxpr = 0;
        bzero(ccpbk, sizeof(ccpbk));
        bzero(ct, sizeof(ct));
        bzero(cpr, sizeof(cpr));
        now = sbinuptime();
#ifdef SMP
        CPU_FOREACH(cpu) {
                cc = CC_CPU(cpu);
#else
                cc = CC_CPU(timeout_cpu);
#endif
                CC_LOCK(cc);
                for (i = 0; i < callwheelsize; i++) {
                        sc = &cc->cc_callwheel[i];
                        c = 0;
                        LIST_FOREACH(tmp, sc, c_links.le) {
                                c++;
                                t = tmp->c_time - now;
                                if (t < 0)
                                        t = 0;
                                st += t / SBT_1US;
                                spr += tmp->c_precision / SBT_1US;
                                if (t > maxt)
                                        maxt = t;
                                if (tmp->c_precision > maxpr)
                                        maxpr = tmp->c_precision;
                                ct[flssbt(t)]++;
                                cpr[flssbt(tmp->c_precision)]++;
                        }
                        if (c > maxc)
                                maxc = c;
                        ccpbk[fls(c + c / 2)]++;
                        count += c;
                }
                CC_UNLOCK(cc);
#ifdef SMP
        }
#endif

        for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
                tcum += ct[i];
        medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
        for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
                pcum += cpr[i];
        medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
        for (i = 0, c = 0; i < 32 && c < count / 2; i++)
                c += ccpbk[i];
        medc = (i >= 2) ? (1 << (i - 2)) : 0;

        printf("Scheduled callouts statistic snapshot:\n");
        printf("  Callouts: %6d  Buckets: %6d*%-3d  Bucket size: 0.%06ds\n",
            count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
        printf("  C/Bk: med %5d         avg %6d.%06jd  max %6d\n",
            medc,
            count / callwheelsize / mp_ncpus,
            (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
            maxc);
        printf("  Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
            medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
            (st / count) / 1000000, (st / count) % 1000000,
            maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
        printf("  Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
            medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
            (spr / count) / 1000000, (spr / count) % 1000000,
            maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
        printf("  Distribution:       \tbuckets\t   time\t   tcum\t"
            "   prec\t   pcum\n");
        for (i = 0, tcum = pcum = 0; i < 64; i++) {
                if (ct[i] == 0 && cpr[i] == 0)
                        continue;
                t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
                tcum += ct[i];
                pcum += cpr[i];
                printf("  %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
                    t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
                    i - 1 - (32 - CC_HASH_SHIFT),
                    ct[i], tcum, cpr[i], pcum);
        }
        return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
    0, 0, sysctl_kern_callout_stat, "I",
    "Dump immediate statistic snapshot of the scheduled callouts");

#ifdef DDB
static void
_show_callout(struct callout *c)
{

        db_printf("callout %p\n", c);
#define C_DB_PRINTF(f, e)       db_printf("   %s = " f "\n", #e, c->e);
        db_printf("   &c_links = %p\n", &(c->c_links));
        C_DB_PRINTF("%" PRId64, c_time);
        C_DB_PRINTF("%" PRId64, c_precision);
        C_DB_PRINTF("%p",       c_arg);
        C_DB_PRINTF("%p",       c_func);
        C_DB_PRINTF("%p",       c_lock);
        C_DB_PRINTF("%#x",      c_flags);
        C_DB_PRINTF("%#x",      c_iflags);
        C_DB_PRINTF("%d",       c_cpu);
#undef  C_DB_PRINTF
}

DB_SHOW_COMMAND(callout, db_show_callout)
{

        if (!have_addr) {
                db_printf("usage: show callout <struct callout *>\n");
                return;
        }

        _show_callout((struct callout *)addr);
}
#endif /* DDB */