xnu-2050.22.13.tar.gz

[apple/xnu.git] / osfmk / kern / thread_call.c

/*
 * Copyright (c) 1993-1995, 1999-2008 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
 
#include <mach/mach_types.h>
#include <mach/thread_act.h>

#include <kern/kern_types.h>
#include <kern/zalloc.h>
#include <kern/sched_prim.h>
#include <kern/clock.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/wait_queue.h>

#include <vm/vm_pageout.h>

#include <kern/thread_call.h>
#include <kern/call_entry.h>
#include <kern/timer_call.h>

#include <libkern/OSAtomic.h>

#include <sys/kdebug.h>


static zone_t                   thread_call_zone;
static struct wait_queue        daemon_wqueue;

struct thread_call_group {
        queue_head_t            pending_queue;
        uint32_t                pending_count;

        queue_head_t            delayed_queue;
        uint32_t                delayed_count;

        timer_call_data_t       delayed_timer;
        timer_call_data_t       dealloc_timer;

        struct wait_queue       idle_wqueue;
        uint32_t                idle_count, active_count;

        integer_t               pri;
        uint32_t                target_thread_count;
        uint64_t                idle_timestamp;

        uint32_t                flags;
        sched_call_t            sched_call;
};

typedef struct thread_call_group        *thread_call_group_t;

#define TCG_PARALLEL            0x01
#define TCG_DEALLOC_ACTIVE      0x02

#define THREAD_CALL_GROUP_COUNT         4
#define THREAD_CALL_THREAD_MIN          4
#define INTERNAL_CALL_COUNT             768
#define THREAD_CALL_DEALLOC_INTERVAL_NS (5 * 1000 * 1000) /* 5 ms */
#define THREAD_CALL_ADD_RATIO           4
#define THREAD_CALL_MACH_FACTOR_CAP     3

static struct thread_call_group thread_call_groups[THREAD_CALL_GROUP_COUNT];
static boolean_t                thread_call_daemon_awake;
static thread_call_data_t       internal_call_storage[INTERNAL_CALL_COUNT];
static queue_head_t             thread_call_internal_queue;
static uint64_t                 thread_call_dealloc_interval_abs;

static __inline__ thread_call_t _internal_call_allocate(void);
static __inline__ void          _internal_call_release(thread_call_t call);
static __inline__ boolean_t     _pending_call_enqueue(thread_call_t call, thread_call_group_t group);
static __inline__ boolean_t     _delayed_call_enqueue(thread_call_t call, thread_call_group_t group, uint64_t deadline);
static __inline__ boolean_t     _call_dequeue(thread_call_t call, thread_call_group_t group);
static __inline__ void          thread_call_wake(thread_call_group_t group);
static __inline__ void          _set_delayed_call_timer(thread_call_t call, thread_call_group_t group);
static boolean_t                _remove_from_pending_queue(thread_call_func_t func, thread_call_param_t param0, boolean_t remove_all);
static boolean_t                _remove_from_delayed_queue(thread_call_func_t func, thread_call_param_t param0, boolean_t remove_all);
static void                     thread_call_daemon(void *arg);
static void                     thread_call_thread(thread_call_group_t group, wait_result_t wres);
extern void                     thread_call_delayed_timer(timer_call_param_t p0, timer_call_param_t p1);
static void                     thread_call_dealloc_timer(timer_call_param_t p0, timer_call_param_t p1);
static void                     thread_call_group_setup(thread_call_group_t group, thread_call_priority_t pri, uint32_t target_thread_count, boolean_t parallel);
static void                     sched_call_thread(int type, thread_t thread);
static void                     thread_call_start_deallocate_timer(thread_call_group_t group);
static void                     thread_call_wait_locked(thread_call_t call);

#define qe(x)           ((queue_entry_t)(x))
#define TC(x)           ((thread_call_t)(x))


lck_grp_t               thread_call_queues_lck_grp;
lck_grp_t               thread_call_lck_grp;
lck_attr_t              thread_call_lck_attr;
lck_grp_attr_t          thread_call_lck_grp_attr;

#if defined(__i386__) || defined(__x86_64__)
lck_mtx_t               thread_call_lock_data;
#else
lck_spin_t              thread_call_lock_data;
#endif


#define thread_call_lock_spin()                 \
        lck_mtx_lock_spin_always(&thread_call_lock_data)

#define thread_call_unlock()                    \
        lck_mtx_unlock_always(&thread_call_lock_data)


static inline spl_t
disable_ints_and_lock(void)
{
        spl_t s;

        s = splsched();
        thread_call_lock_spin();

        return s;
}

static inline void 
enable_ints_and_unlock(void)
{
        thread_call_unlock();
        (void)spllo();
}


static inline boolean_t
group_isparallel(thread_call_group_t group)
{
        return ((group->flags & TCG_PARALLEL) != 0);
}

static boolean_t
thread_call_group_should_add_thread(thread_call_group_t group) 
{
        uint32_t thread_count;

        if (!group_isparallel(group)) {
                if (group->pending_count > 0 && group->active_count == 0) {
                        return TRUE;
                }

                return FALSE;
        }

        if (group->pending_count > 0) {
                if (group->idle_count > 0) {
                        panic("Pending work, but threads are idle?");
                }

                thread_count = group->active_count;

                /*
                 * Add a thread if either there are no threads,
                 * the group has fewer than its target number of
                 * threads, or the amount of work is large relative
                 * to the number of threads.  In the last case, pay attention
                 * to the total load on the system, and back off if 
         * it's high.
                 */
                if ((thread_count == 0) ||
                        (thread_count < group->target_thread_count) ||
                        ((group->pending_count > THREAD_CALL_ADD_RATIO * thread_count) && 
                         (sched_mach_factor < THREAD_CALL_MACH_FACTOR_CAP))) {
                        return TRUE;
                }
        }
                        
        return FALSE;
}

static inline integer_t
thread_call_priority_to_sched_pri(thread_call_priority_t pri) 
{
        switch (pri) {
        case THREAD_CALL_PRIORITY_HIGH:
                return BASEPRI_PREEMPT;
        case THREAD_CALL_PRIORITY_KERNEL:
                return BASEPRI_KERNEL;
        case THREAD_CALL_PRIORITY_USER:
                return BASEPRI_DEFAULT;
        case THREAD_CALL_PRIORITY_LOW:
                return DEPRESSPRI;
        default:
                panic("Invalid priority.");
        }

        return 0;
}

/* Lock held */
static inline thread_call_group_t
thread_call_get_group(
                thread_call_t call)
{
        thread_call_priority_t  pri = call->tc_pri;

        assert(pri == THREAD_CALL_PRIORITY_LOW ||
                        pri == THREAD_CALL_PRIORITY_USER ||
                        pri == THREAD_CALL_PRIORITY_KERNEL ||
                        pri == THREAD_CALL_PRIORITY_HIGH);

        return &thread_call_groups[pri];
}

static void
thread_call_group_setup(
                thread_call_group_t             group, 
                thread_call_priority_t          pri,
                uint32_t                        target_thread_count,
                boolean_t                       parallel)
{
        queue_init(&group->pending_queue);
        queue_init(&group->delayed_queue);

        timer_call_setup(&group->delayed_timer, thread_call_delayed_timer, group);
        timer_call_setup(&group->dealloc_timer, thread_call_dealloc_timer, group);

        wait_queue_init(&group->idle_wqueue, SYNC_POLICY_FIFO);

        group->target_thread_count = target_thread_count;
        group->pri = thread_call_priority_to_sched_pri(pri);

        group->sched_call = sched_call_thread; 
        if (parallel) {
                group->flags |= TCG_PARALLEL;
                group->sched_call = NULL;
        } 
}

/*
 * Simple wrapper for creating threads bound to 
 * thread call groups.
 */
static kern_return_t
thread_call_thread_create(
                thread_call_group_t             group)
{
        thread_t thread;
        kern_return_t result;

        result = kernel_thread_start_priority((thread_continue_t)thread_call_thread, group, group->pri, &thread);
        if (result != KERN_SUCCESS) {
                return result;
        }

        if (group->pri < BASEPRI_PREEMPT) {
                /*
                 * New style doesn't get to run to completion in 
                 * kernel if there are higher priority threads 
                 * available.
                 */
                thread_set_eager_preempt(thread);
        }

        thread_deallocate(thread);
        return KERN_SUCCESS;
}

/*
 *      thread_call_initialize:
 *
 *      Initialize this module, called
 *      early during system initialization.
 */
void
thread_call_initialize(void)
{
        thread_call_t                   call;
        kern_return_t                   result;
        thread_t                        thread;
        int                             i;

        i = sizeof (thread_call_data_t);
        thread_call_zone = zinit(i, 4096 * i, 16 * i, "thread_call");
        zone_change(thread_call_zone, Z_CALLERACCT, FALSE);
        zone_change(thread_call_zone, Z_NOENCRYPT, TRUE);

        lck_attr_setdefault(&thread_call_lck_attr);
        lck_grp_attr_setdefault(&thread_call_lck_grp_attr);
        lck_grp_init(&thread_call_queues_lck_grp, "thread_call_queues", &thread_call_lck_grp_attr);
        lck_grp_init(&thread_call_lck_grp, "thread_call", &thread_call_lck_grp_attr);

#if defined(__i386__) || defined(__x86_64__)
        lck_mtx_init(&thread_call_lock_data, &thread_call_lck_grp, &thread_call_lck_attr);
#else
        lck_spin_init(&thread_call_lock_data, &thread_call_lck_grp, &thread_call_lck_attr);
#endif

        nanotime_to_absolutetime(0, THREAD_CALL_DEALLOC_INTERVAL_NS, &thread_call_dealloc_interval_abs);
        wait_queue_init(&daemon_wqueue, SYNC_POLICY_FIFO);

        thread_call_group_setup(&thread_call_groups[THREAD_CALL_PRIORITY_LOW], THREAD_CALL_PRIORITY_LOW, 0, TRUE);
        thread_call_group_setup(&thread_call_groups[THREAD_CALL_PRIORITY_USER], THREAD_CALL_PRIORITY_USER, 0, TRUE);
        thread_call_group_setup(&thread_call_groups[THREAD_CALL_PRIORITY_KERNEL], THREAD_CALL_PRIORITY_KERNEL, 1, TRUE);
        thread_call_group_setup(&thread_call_groups[THREAD_CALL_PRIORITY_HIGH], THREAD_CALL_PRIORITY_HIGH, THREAD_CALL_THREAD_MIN, FALSE);

        disable_ints_and_lock();

        queue_init(&thread_call_internal_queue);
        for (
                        call = internal_call_storage;
                        call < &internal_call_storage[INTERNAL_CALL_COUNT];
                        call++) {

                enqueue_tail(&thread_call_internal_queue, qe(call));
        }

        thread_call_daemon_awake = TRUE;

        enable_ints_and_unlock();

        result = kernel_thread_start_priority((thread_continue_t)thread_call_daemon, NULL, BASEPRI_PREEMPT + 1, &thread);
        if (result != KERN_SUCCESS)
                panic("thread_call_initialize");

        thread_deallocate(thread);
}

void
thread_call_setup(
        thread_call_t                   call,
        thread_call_func_t              func,
        thread_call_param_t             param0)
{
        bzero(call, sizeof(*call));
        call_entry_setup((call_entry_t)call, func, param0);
        call->tc_pri = THREAD_CALL_PRIORITY_HIGH; /* Default priority */
}

/*
 *      _internal_call_allocate:
 *
 *      Allocate an internal callout entry.
 *
 *      Called with thread_call_lock held.
 */
static __inline__ thread_call_t
_internal_call_allocate(void)
{
    thread_call_t               call;
    
    if (queue_empty(&thread_call_internal_queue))
        panic("_internal_call_allocate");
        
    call = TC(dequeue_head(&thread_call_internal_queue));
    
    return (call);
}

/*
 *      _internal_call_release:
 *
 *      Release an internal callout entry which
 *      is no longer pending (or delayed).
 *
 *      Called with thread_call_lock held.
 */
static __inline__ void
_internal_call_release(
    thread_call_t               call)
{
    if (    call >= internal_call_storage                                               &&
                    call < &internal_call_storage[INTERNAL_CALL_COUNT]          )
                enqueue_head(&thread_call_internal_queue, qe(call));
}

/*
 *      _pending_call_enqueue:
 *
 *      Place an entry at the end of the
 *      pending queue, to be executed soon.
 *
 *      Returns TRUE if the entry was already
 *      on a queue.
 *
 *      Called with thread_call_lock held.
 */
static __inline__ boolean_t
_pending_call_enqueue(
    thread_call_t               call,
        thread_call_group_t     group)
{
        queue_head_t            *old_queue;

        old_queue = call_entry_enqueue_tail(CE(call), &group->pending_queue);

        if (old_queue == NULL) {
                call->tc_submit_count++;
        }

        group->pending_count++;

        thread_call_wake(group);

        return (old_queue != NULL);
}

/*
 *      _delayed_call_enqueue:
 *
 *      Place an entry on the delayed queue,
 *      after existing entries with an earlier
 *      (or identical) deadline.
 *
 *      Returns TRUE if the entry was already
 *      on a queue.
 *
 *      Called with thread_call_lock held.
 */
static __inline__ boolean_t
_delayed_call_enqueue(
        thread_call_t           call,
        thread_call_group_t     group,
        uint64_t                deadline)
{
        queue_head_t            *old_queue;

        old_queue = call_entry_enqueue_deadline(CE(call), &group->delayed_queue, deadline);

        if (old_queue == &group->pending_queue)
                group->pending_count--;
        else if (old_queue == NULL) 
                call->tc_submit_count++;

        return (old_queue != NULL);
}

/*
 *      _call_dequeue:
 *
 *      Remove an entry from a queue.
 *
 *      Returns TRUE if the entry was on a queue.
 *
 *      Called with thread_call_lock held.
 */
static __inline__ boolean_t
_call_dequeue(
        thread_call_t           call,
        thread_call_group_t     group)
{
        queue_head_t            *old_queue;

        old_queue = call_entry_dequeue(CE(call));

        if (old_queue != NULL) {
                call->tc_finish_count++;
                if (old_queue == &group->pending_queue)
                        group->pending_count--;
        }

        return (old_queue != NULL);
}

/*
 *      _set_delayed_call_timer:
 *
 *      Reset the timer so that it
 *      next expires when the entry is due.
 *
 *      Called with thread_call_lock held.
 */
static __inline__ void
_set_delayed_call_timer(
    thread_call_t               call,
        thread_call_group_t     group)
{
    timer_call_enter(&group->delayed_timer, call->tc_call.deadline, 0);
}

/*
 *      _remove_from_pending_queue:
 *
 *      Remove the first (or all) matching
 *      entries from the pending queue.
 *
 *      Returns TRUE if any matching entries
 *      were found.
 *
 *      Called with thread_call_lock held.
 */
static boolean_t
_remove_from_pending_queue(
    thread_call_func_t          func,
    thread_call_param_t         param0,
    boolean_t                           remove_all)
{
        boolean_t                               call_removed = FALSE;
        thread_call_t                   call;
        thread_call_group_t             group = &thread_call_groups[THREAD_CALL_PRIORITY_HIGH];

        call = TC(queue_first(&group->pending_queue));

        while (!queue_end(&group->pending_queue, qe(call))) {
                if (call->tc_call.func == func &&
                                call->tc_call.param0 == param0) {
                        thread_call_t   next = TC(queue_next(qe(call)));

                        _call_dequeue(call, group);

                        _internal_call_release(call);

                        call_removed = TRUE;
                        if (!remove_all)
                                break;

                        call = next;
                }
                else    
                        call = TC(queue_next(qe(call)));
        }

        return (call_removed);
}

/*
 *      _remove_from_delayed_queue:
 *
 *      Remove the first (or all) matching
 *      entries from the delayed queue.
 *
 *      Returns TRUE if any matching entries
 *      were found.
 *
 *      Called with thread_call_lock held.
 */
static boolean_t
_remove_from_delayed_queue(
    thread_call_func_t          func,
    thread_call_param_t         param0,
    boolean_t                           remove_all)
{
        boolean_t                       call_removed = FALSE;
        thread_call_t                   call;
        thread_call_group_t             group = &thread_call_groups[THREAD_CALL_PRIORITY_HIGH];

        call = TC(queue_first(&group->delayed_queue));

        while (!queue_end(&group->delayed_queue, qe(call))) {
                if (call->tc_call.func == func  &&
                                call->tc_call.param0 == param0) {
                        thread_call_t   next = TC(queue_next(qe(call)));

                        _call_dequeue(call, group);

                        _internal_call_release(call);

                        call_removed = TRUE;
                        if (!remove_all)
                                break;

                        call = next;
                }
                else    
                        call = TC(queue_next(qe(call)));
        }

        return (call_removed);
}

#ifndef __LP64__

/*
 *      thread_call_func:
 *
 *      Enqueue a function callout.
 *
 *      Guarantees { function, argument }
 *      uniqueness if unique_call is TRUE.
 */
void
thread_call_func(
    thread_call_func_t          func,
    thread_call_param_t         param,
    boolean_t                           unique_call)
{
        thread_call_t           call;
        thread_call_group_t     group = &thread_call_groups[THREAD_CALL_PRIORITY_HIGH];
        spl_t                   s;

        s = splsched();
        thread_call_lock_spin();

        call = TC(queue_first(&group->pending_queue));

        while (unique_call && !queue_end(&group->pending_queue, qe(call))) {
                if (call->tc_call.func == func && call->tc_call.param0 == param) {
                        break;
                }

                call = TC(queue_next(qe(call)));
        }

        if (!unique_call || queue_end(&group->pending_queue, qe(call))) {
                call = _internal_call_allocate();
                call->tc_call.func      = func;
                call->tc_call.param0    = param;
                call->tc_call.param1    = NULL;

                _pending_call_enqueue(call, group);
        }

        thread_call_unlock();
        splx(s);
}

#endif  /* __LP64__ */

/*
 *      thread_call_func_delayed:
 *
 *      Enqueue a function callout to
 *      occur at the stated time.
 */
void
thread_call_func_delayed(
                thread_call_func_t              func,
                thread_call_param_t             param,
                uint64_t                        deadline)
{
        thread_call_t           call;
        thread_call_group_t     group = &thread_call_groups[THREAD_CALL_PRIORITY_HIGH];
        spl_t                   s;

        s = splsched();
        thread_call_lock_spin();

        call = _internal_call_allocate();
        call->tc_call.func      = func;
        call->tc_call.param0    = param;
        call->tc_call.param1    = 0;

        _delayed_call_enqueue(call, group, deadline);

        if (queue_first(&group->delayed_queue) == qe(call))
                _set_delayed_call_timer(call, group);

        thread_call_unlock();
        splx(s);
}

/*
 *      thread_call_func_cancel:
 *
 *      Dequeue a function callout.
 *
 *      Removes one (or all) { function, argument }
 *      instance(s) from either (or both)
 *      the pending and the delayed queue,
 *      in that order.
 *
 *      Returns TRUE if any calls were cancelled.
 */
boolean_t
thread_call_func_cancel(
                thread_call_func_t              func,
                thread_call_param_t             param,
                boolean_t                       cancel_all)
{
        boolean_t       result;
        spl_t           s;

        s = splsched();
        thread_call_lock_spin();

        if (cancel_all)
                result = _remove_from_pending_queue(func, param, cancel_all) |
                        _remove_from_delayed_queue(func, param, cancel_all);
        else
                result = _remove_from_pending_queue(func, param, cancel_all) ||
                        _remove_from_delayed_queue(func, param, cancel_all);

        thread_call_unlock();
        splx(s);

        return (result);
}

/*
 * Allocate a thread call with a given priority.  Importances
 * other than THREAD_CALL_PRIORITY_HIGH will be run in threads
 * with eager preemption enabled (i.e. may be aggressively preempted
 * by higher-priority threads which are not in the normal "urgent" bands).
 */
thread_call_t
thread_call_allocate_with_priority(
                thread_call_func_t              func,
                thread_call_param_t             param0,
                thread_call_priority_t          pri)
{
        thread_call_t call;

        if (pri > THREAD_CALL_PRIORITY_LOW) {
                panic("Invalid pri: %d\n", pri);
        }

        call = thread_call_allocate(func, param0);
        call->tc_pri = pri;

        return call;
}

/*
 *      thread_call_allocate:
 *
 *      Allocate a callout entry.
 */
thread_call_t
thread_call_allocate(
                thread_call_func_t              func,
                thread_call_param_t             param0)
{
        thread_call_t   call = zalloc(thread_call_zone);

        thread_call_setup(call, func, param0);
        call->tc_refs = 1;
        call->tc_flags = THREAD_CALL_ALLOC;

        return (call);
}

/*
 *      thread_call_free:
 *
 *      Release a callout.  If the callout is currently
 *      executing, it will be freed when all invocations
 *      finish.
 */
boolean_t
thread_call_free(
                thread_call_t           call)
{
        spl_t   s;
        int32_t refs;

        s = splsched();
        thread_call_lock_spin();

        if (call->tc_call.queue != NULL) {
                thread_call_unlock();
                splx(s);

                return (FALSE);
        }

        refs = --call->tc_refs;
        if (refs < 0) {
                panic("Refcount negative: %d\n", refs);
        }       

        thread_call_unlock();
        splx(s);

        if (refs == 0) {
                zfree(thread_call_zone, call);
        }

        return (TRUE);
}

/*
 *      thread_call_enter:
 *
 *      Enqueue a callout entry to occur "soon".
 *
 *      Returns TRUE if the call was
 *      already on a queue.
 */
boolean_t
thread_call_enter(
                thread_call_t           call)
{
        boolean_t               result = TRUE;
        thread_call_group_t     group;
        spl_t                   s;

        group = thread_call_get_group(call);

        s = splsched();
        thread_call_lock_spin();

        if (call->tc_call.queue != &group->pending_queue) {
                result = _pending_call_enqueue(call, group);
        }

        call->tc_call.param1 = 0;

        thread_call_unlock();
        splx(s);

        return (result);
}

boolean_t
thread_call_enter1(
                thread_call_t                   call,
                thread_call_param_t             param1)
{
        boolean_t               result = TRUE;
        thread_call_group_t     group;
        spl_t                   s;

        group = thread_call_get_group(call);

        s = splsched();
        thread_call_lock_spin();

        if (call->tc_call.queue != &group->pending_queue) {
                result = _pending_call_enqueue(call, group);
        }

        call->tc_call.param1 = param1;

        thread_call_unlock();
        splx(s);

        return (result);
}

/*
 *      thread_call_enter_delayed:
 *
 *      Enqueue a callout entry to occur
 *      at the stated time.
 *
 *      Returns TRUE if the call was
 *      already on a queue.
 */
boolean_t
thread_call_enter_delayed(
                thread_call_t           call,
                uint64_t                        deadline)
{
        boolean_t               result = TRUE;
        thread_call_group_t     group;
        spl_t                   s;
        
        group = thread_call_get_group(call);

        s = splsched();
        thread_call_lock_spin();

        result = _delayed_call_enqueue(call, group, deadline);

        if (queue_first(&group->delayed_queue) == qe(call))
                _set_delayed_call_timer(call, group);

        call->tc_call.param1 = 0;

        thread_call_unlock();
        splx(s);

        return (result);
}

boolean_t
thread_call_enter1_delayed(
                thread_call_t                   call,
                thread_call_param_t             param1,
                uint64_t                        deadline)
{
        boolean_t               result = TRUE;
        thread_call_group_t     group;
        spl_t                   s;

        group = thread_call_get_group(call);

        s = splsched();
        thread_call_lock_spin();

        result = _delayed_call_enqueue(call, group, deadline);

        if (queue_first(&group->delayed_queue) == qe(call))
                _set_delayed_call_timer(call, group);

        call->tc_call.param1 = param1;

        thread_call_unlock();
        splx(s);

        return (result);
}

/*
 *      thread_call_cancel:
 *
 *      Dequeue a callout entry.
 *
 *      Returns TRUE if the call was
 *      on a queue.
 */
boolean_t
thread_call_cancel(
                thread_call_t           call)
{
        boolean_t               result;
        thread_call_group_t     group;
        spl_t                   s;

        group = thread_call_get_group(call);

        s = splsched();
        thread_call_lock_spin();

        result = _call_dequeue(call, group);

        thread_call_unlock();
        splx(s);

        return (result);
}

/*
 * Cancel a thread call.  If it cannot be cancelled (i.e.
 * is already in flight), waits for the most recent invocation
 * to finish.  Note that if clients re-submit this thread call,
 * it may still be pending or in flight when thread_call_cancel_wait
 * returns, but all requests to execute this work item prior
 * to the call to thread_call_cancel_wait will have finished.
 */
boolean_t
thread_call_cancel_wait(
                thread_call_t           call)
{
        boolean_t               result;
        thread_call_group_t     group;

        if ((call->tc_flags & THREAD_CALL_ALLOC) == 0) {
                panic("%s: Can't wait on thread call whose storage I don't own.", __FUNCTION__);
        }

        group = thread_call_get_group(call);

        (void) splsched();
        thread_call_lock_spin();

        result = _call_dequeue(call, group);
        if (result == FALSE) {
                thread_call_wait_locked(call);
        }

        thread_call_unlock();
        (void) spllo();

        return result;
}


#ifndef __LP64__

/*
 *      thread_call_is_delayed:
 *
 *      Returns TRUE if the call is
 *      currently on a delayed queue.
 *
 *      Optionally returns the expiration time.
 */
boolean_t
thread_call_is_delayed(
        thread_call_t           call,
        uint64_t                        *deadline)
{
        boolean_t                       result = FALSE;
        thread_call_group_t             group;
        spl_t                           s;

        group = thread_call_get_group(call);

        s = splsched();
        thread_call_lock_spin();

        if (call->tc_call.queue == &group->delayed_queue) {
                if (deadline != NULL)
                        *deadline = call->tc_call.deadline;
                result = TRUE;
        }

        thread_call_unlock();
        splx(s);

        return (result);
}

#endif  /* __LP64__ */

/*
 *      thread_call_wake:
 *
 *      Wake a call thread to service
 *      pending call entries.  May wake
 *      the daemon thread in order to
 *      create additional call threads.
 *
 *      Called with thread_call_lock held.
 *
 *      For high-priority group, only does wakeup/creation if there are no threads
 *      running.
 */
static __inline__ void
thread_call_wake(
        thread_call_group_t             group)
{
        /* 
         * New behavior: use threads if you've got 'em.
         * Traditional behavior: wake only if no threads running.
         */
        if (group_isparallel(group) || group->active_count == 0) {
                if (wait_queue_wakeup_one(&group->idle_wqueue, NO_EVENT, THREAD_AWAKENED, -1) == KERN_SUCCESS) {
                        group->idle_count--; group->active_count++;

                        if (group->idle_count == 0) {
                                timer_call_cancel(&group->dealloc_timer);
                                group->flags &= TCG_DEALLOC_ACTIVE;
                        }
                } else {
                        if (!thread_call_daemon_awake && thread_call_group_should_add_thread(group)) {
                                thread_call_daemon_awake = TRUE;
                                wait_queue_wakeup_one(&daemon_wqueue, NO_EVENT, THREAD_AWAKENED, -1);
                        }
                }
        }
}

/*
 *      sched_call_thread:
 *
 *      Call out invoked by the scheduler.  Used only for high-priority
 *      thread call group.
 */
static void
sched_call_thread(
                int                             type,
                __unused        thread_t                thread)
{
        thread_call_group_t             group;

        group = &thread_call_groups[THREAD_CALL_PRIORITY_HIGH]; /* XXX */

        thread_call_lock_spin();

        switch (type) {

                case SCHED_CALL_BLOCK:
                        --group->active_count;
                        if (group->pending_count > 0)
                                thread_call_wake(group);
                        break;

                case SCHED_CALL_UNBLOCK:
                        group->active_count++;
                        break;
        }

        thread_call_unlock();
}

/* 
 * Interrupts disabled, lock held; returns the same way. 
 * Only called on thread calls whose storage we own.  Wakes up
 * anyone who might be waiting on this work item and frees it
 * if the client has so requested.
 */
static void
thread_call_finish(thread_call_t call)
{
        boolean_t dowake = FALSE;

        call->tc_finish_count++;
        call->tc_refs--;

        if ((call->tc_flags & THREAD_CALL_WAIT) != 0) {
                dowake = TRUE;
                call->tc_flags &= ~THREAD_CALL_WAIT;

                /* 
                 * Dropping lock here because the sched call for the 
                 * high-pri group can take the big lock from under
                 * a thread lock.
                 */
                thread_call_unlock();
                thread_wakeup((event_t)call);
                thread_call_lock_spin();
        }

        if (call->tc_refs == 0) {
                if (dowake) {
                        panic("Someone waiting on a thread call that is scheduled for free: %p\n", call->tc_call.func);
                }

                enable_ints_and_unlock();

                zfree(thread_call_zone, call);

                (void)disable_ints_and_lock();
        }

}

/*
 *      thread_call_thread:
 */
static void
thread_call_thread(
                thread_call_group_t             group,
                wait_result_t                   wres)
{
        thread_t        self = current_thread();
        boolean_t       canwait;

        /*
         * A wakeup with THREAD_INTERRUPTED indicates that 
         * we should terminate.
         */
        if (wres == THREAD_INTERRUPTED) {
                thread_terminate(self);

                /* NOTREACHED */
                panic("thread_terminate() returned?");
        }

        (void)disable_ints_and_lock();

        thread_sched_call(self, group->sched_call);

        while (group->pending_count > 0) {
                thread_call_t                   call;
                thread_call_func_t              func;
                thread_call_param_t             param0, param1;

                call = TC(dequeue_head(&group->pending_queue));
                group->pending_count--;

                func = call->tc_call.func;
                param0 = call->tc_call.param0;
                param1 = call->tc_call.param1;

                call->tc_call.queue = NULL;

                _internal_call_release(call);

                /*
                 * Can only do wakeups for thread calls whose storage
                 * we control.
                 */
                if ((call->tc_flags & THREAD_CALL_ALLOC) != 0) {
                        canwait = TRUE;
                        call->tc_refs++;        /* Delay free until we're done */
                } else
                        canwait = FALSE;

                enable_ints_and_unlock();

                KERNEL_DEBUG_CONSTANT(
                                MACHDBG_CODE(DBG_MACH_SCHED,MACH_CALLOUT) | DBG_FUNC_NONE,
                                VM_KERNEL_UNSLIDE(func), param0, param1, 0, 0);

                (*func)(param0, param1);

                if (get_preemption_level() != 0) {
                        int pl = get_preemption_level();
                        panic("thread_call_thread: preemption_level %d, last callout %p(%p, %p)",
                                        pl, (void *)VM_KERNEL_UNSLIDE(func), param0, param1);
                }

                (void)thread_funnel_set(self->funnel_lock, FALSE);              /* XXX */

                (void) disable_ints_and_lock();
                
                if (canwait) {
                        /* Frees if so desired */
                        thread_call_finish(call);
                }
        }

        thread_sched_call(self, NULL);
        group->active_count--;

        if (group_isparallel(group)) {
                /*
                 * For new style of thread group, thread always blocks. 
                 * If we have more than the target number of threads,
                 * and this is the first to block, and it isn't active 
                 * already, set a timer for deallocating a thread if we 
                 * continue to have a surplus.
                 */
                group->idle_count++;

                if (group->idle_count == 1) {
                        group->idle_timestamp = mach_absolute_time();
                }   

                if (((group->flags & TCG_DEALLOC_ACTIVE) == 0) &&
                                ((group->active_count + group->idle_count) > group->target_thread_count)) {
                        group->flags |= TCG_DEALLOC_ACTIVE;
                        thread_call_start_deallocate_timer(group);
                }   

                /* Wait for more work (or termination) */
                wres = wait_queue_assert_wait(&group->idle_wqueue, NO_EVENT, THREAD_INTERRUPTIBLE, 0); 
                if (wres != THREAD_WAITING) {
                        panic("kcall worker unable to assert wait?");
                }   

                enable_ints_and_unlock();

                thread_block_parameter((thread_continue_t)thread_call_thread, group);
        } else {
                if (group->idle_count < group->target_thread_count) {
                        group->idle_count++;

                        wait_queue_assert_wait(&group->idle_wqueue, NO_EVENT, THREAD_UNINT, 0); /* Interrupted means to exit */

                        enable_ints_and_unlock();

                        thread_block_parameter((thread_continue_t)thread_call_thread, group);
                        /* NOTREACHED */
                }
        }

        enable_ints_and_unlock();

        thread_terminate(self);
        /* NOTREACHED */
}

/*
 *      thread_call_daemon: walk list of groups, allocating
 *      threads if appropriate (as determined by 
 *      thread_call_group_should_add_thread()).  
 */
static void
thread_call_daemon_continue(__unused void *arg)
{
        int             i;
        kern_return_t   kr;
        thread_call_group_t group;

        (void)disable_ints_and_lock();

        /* Starting at zero happens to be high-priority first. */
        for (i = 0; i < THREAD_CALL_GROUP_COUNT; i++) {
                group = &thread_call_groups[i];
                while (thread_call_group_should_add_thread(group)) {
                        group->active_count++;

                        enable_ints_and_unlock();

                        kr = thread_call_thread_create(group);
                        if (kr != KERN_SUCCESS) {
                                /*
                                 * On failure, just pause for a moment and give up. 
                                 * We can try again later.
                                 */
                                delay(10000); /* 10 ms */
                                (void)disable_ints_and_lock();
                                goto out;
                        }

                        (void)disable_ints_and_lock();
                }
        }

out:
        thread_call_daemon_awake = FALSE;
        wait_queue_assert_wait(&daemon_wqueue, NO_EVENT, THREAD_UNINT, 0);

        enable_ints_and_unlock();

        thread_block_parameter((thread_continue_t)thread_call_daemon_continue, NULL);
        /* NOTREACHED */
}

static void
thread_call_daemon(
                __unused void    *arg)
{
        thread_t        self = current_thread();

        self->options |= TH_OPT_VMPRIV;
        vm_page_free_reserve(2);        /* XXX */

        thread_call_daemon_continue(NULL);
        /* NOTREACHED */
}

/*
 * Schedule timer to deallocate a worker thread if we have a surplus 
 * of threads (in excess of the group's target) and at least one thread
 * is idle the whole time.
 */
static void
thread_call_start_deallocate_timer(
                thread_call_group_t group)
{
        uint64_t deadline;
        boolean_t onqueue;

        assert(group->idle_count > 0);

        group->flags |= TCG_DEALLOC_ACTIVE;
        deadline = group->idle_timestamp + thread_call_dealloc_interval_abs;
        onqueue = timer_call_enter(&group->dealloc_timer, deadline, 0); 

        if (onqueue) {
                panic("Deallocate timer already active?");
        }   
}

void
thread_call_delayed_timer(
                timer_call_param_t              p0,
                __unused timer_call_param_t     p1
)
{
        thread_call_t                   call;
        thread_call_group_t             group = p0;
        uint64_t                                timestamp;

        thread_call_lock_spin();

        timestamp = mach_absolute_time();

        call = TC(queue_first(&group->delayed_queue));

        while (!queue_end(&group->delayed_queue, qe(call))) {
                if (call->tc_call.deadline <= timestamp) {
                        _pending_call_enqueue(call, group);
                }
                else
                        break;

                call = TC(queue_first(&group->delayed_queue));
        }

        if (!queue_end(&group->delayed_queue, qe(call)))
                _set_delayed_call_timer(call, group);

        thread_call_unlock();
}

/*
 * Timer callback to tell a thread to terminate if
 * we have an excess of threads and at least one has been
 * idle for a long time.
 */
static void
thread_call_dealloc_timer(
                timer_call_param_t              p0,
                __unused timer_call_param_t     p1)
{
        thread_call_group_t group = (thread_call_group_t)p0;
        uint64_t now;
        kern_return_t res;
        boolean_t terminated = FALSE;
        
        thread_call_lock_spin();

        now = mach_absolute_time();
        if (group->idle_count > 0) {
                if (now > group->idle_timestamp + thread_call_dealloc_interval_abs) {
                        terminated = TRUE;
                        group->idle_count--;
                        res = wait_queue_wakeup_one(&group->idle_wqueue, NO_EVENT, THREAD_INTERRUPTED, -1);
                        if (res != KERN_SUCCESS) {
                                panic("Unable to wake up idle thread for termination?");
                        }
                }

        }

        /*
         * If we still have an excess of threads, schedule another
         * invocation of this function.
         */
        if (group->idle_count > 0 && (group->idle_count + group->active_count > group->target_thread_count)) {
                /*
                 * If we killed someone just now, push out the
                 * next deadline.
                 */
                if (terminated) {
                        group->idle_timestamp = now;
                }

                thread_call_start_deallocate_timer(group);
        } else {
                group->flags &= ~TCG_DEALLOC_ACTIVE;
        }

        thread_call_unlock();
}

/*
 * Wait for all requested invocations of a thread call prior to now
 * to finish.  Can only be invoked on thread calls whose storage we manage.  
 * Just waits for the finish count to catch up to the submit count we find
 * at the beginning of our wait.
 */
static void
thread_call_wait_locked(thread_call_t call)
{
        uint64_t submit_count;
        wait_result_t res;

        assert(call->tc_flags & THREAD_CALL_ALLOC);

        submit_count = call->tc_submit_count;

        while (call->tc_finish_count < submit_count) {
                call->tc_flags |= THREAD_CALL_WAIT;

                res = assert_wait(call, THREAD_UNINT);
                if (res != THREAD_WAITING) {
                        panic("Unable to assert wait?");
                }

                thread_call_unlock();
                (void) spllo();

                res = thread_block(NULL);
                if (res != THREAD_AWAKENED) {
                        panic("Awoken with %d?", res);
                }
        
                (void) splsched();
                thread_call_lock_spin();
        }
}

/*
 * Determine whether a thread call is either on a queue or
 * currently being executed.
 */
boolean_t
thread_call_isactive(thread_call_t call) 
{
        boolean_t active;

        disable_ints_and_lock();
        active = (call->tc_submit_count > call->tc_finish_count);
        enable_ints_and_unlock();

        return active;
}