xnu-4570.1.46.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/waitq.h>
#include <kern/ledger.h>
#include <kern/policy_internal.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 <kern/timer_queue.h>

#include <sys/kdebug.h>
#if CONFIG_DTRACE
#include <mach/sdt.h>
#endif
#include <machine/machine_routines.h>

static zone_t                   thread_call_zone;
static struct waitq             daemon_waitq;

typedef enum {
        TCF_ABSOLUTE    = 0,
        TCF_CONTINUOUS  = 1,
        TCF_COUNT       = 2,
} thread_call_flavor_t;

typedef enum {
        TCG_NONE                = 0x0,
        TCG_PARALLEL            = 0x1,
        TCG_DEALLOC_ACTIVE      = 0x2,
} thread_call_group_flags_t;

static struct thread_call_group {
        const char *            tcg_name;

        queue_head_t            pending_queue;
        uint32_t                pending_count;

        queue_head_t            delayed_queues[TCF_COUNT];
        timer_call_data_t       delayed_timers[TCF_COUNT];

        timer_call_data_t       dealloc_timer;

        struct waitq            idle_waitq;
        uint32_t                idle_count, active_count, blocked_count;

        uint32_t                tcg_thread_pri;
        uint32_t                target_thread_count;
        uint64_t                idle_timestamp;

        thread_call_group_flags_t flags;

} thread_call_groups[THREAD_CALL_INDEX_MAX] = {
        [THREAD_CALL_INDEX_HIGH] = {
                .tcg_name               = "high",
                .tcg_thread_pri         = BASEPRI_PREEMPT_HIGH,
                .target_thread_count    = 4,
                .flags                  = TCG_NONE,
        },
        [THREAD_CALL_INDEX_KERNEL] = {
                .tcg_name               = "kernel",
                .tcg_thread_pri         = BASEPRI_KERNEL,
                .target_thread_count    = 1,
                .flags                  = TCG_PARALLEL,
        },
        [THREAD_CALL_INDEX_USER] = {
                .tcg_name               = "user",
                .tcg_thread_pri         = BASEPRI_DEFAULT,
                .target_thread_count    = 1,
                .flags                  = TCG_PARALLEL,
        },
        [THREAD_CALL_INDEX_LOW] = {
                .tcg_name               = "low",
                .tcg_thread_pri         = MAXPRI_THROTTLE,
                .target_thread_count    = 1,
                .flags                  = TCG_PARALLEL,
        },
        [THREAD_CALL_INDEX_KERNEL_HIGH] = {
                .tcg_name               = "kernel-high",
                .tcg_thread_pri         = BASEPRI_PREEMPT,
                .target_thread_count    = 2,
                .flags                  = TCG_NONE,
        },
        [THREAD_CALL_INDEX_QOS_UI] = {
                .tcg_name               = "qos-ui",
                .tcg_thread_pri         = BASEPRI_FOREGROUND,
                .target_thread_count    = 1,
                .flags                  = TCG_NONE,
        },
        [THREAD_CALL_INDEX_QOS_IN] = {
                .tcg_name               = "qos-in",
                .tcg_thread_pri         = BASEPRI_USER_INITIATED,
                .target_thread_count    = 1,
                .flags                  = TCG_NONE,
        },
        [THREAD_CALL_INDEX_QOS_UT] = {
                .tcg_name               = "qos-ut",
                .tcg_thread_pri         = BASEPRI_UTILITY,
                .target_thread_count    = 1,
                .flags                  = TCG_NONE,
        },
};

typedef struct thread_call_group        *thread_call_group_t;

#define INTERNAL_CALL_COUNT             768
#define THREAD_CALL_DEALLOC_INTERVAL_NS (5 * NSEC_PER_MSEC) /* 5 ms */
#define THREAD_CALL_ADD_RATIO           4
#define THREAD_CALL_MACH_FACTOR_CAP     3
#define THREAD_CALL_GROUP_MAX_THREADS   500

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;
int                                             thread_call_internal_queue_count = 0;
static uint64_t                 thread_call_dealloc_interval_abs;

static __inline__ thread_call_t _internal_call_allocate(thread_call_func_t func, thread_call_param_t param0);
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 boolean_t                _delayed_call_enqueue(thread_call_t call, thread_call_group_t group,
                                                      uint64_t deadline, thread_call_flavor_t flavor);
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 void                     thread_call_daemon(void *arg);
static void                     thread_call_thread(thread_call_group_t group, wait_result_t wres);
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);
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, spl_t s);
static boolean_t                thread_call_wait_once_locked(thread_call_t call, spl_t s);

static boolean_t                thread_call_enter_delayed_internal(thread_call_t call,
                                                thread_call_func_t alt_func, thread_call_param_t alt_param0,
                                                thread_call_param_t param1, uint64_t deadline,
                                                uint64_t leeway, unsigned int flags);

/* non-static so dtrace can find it rdar://problem/31156135&31379348 */
extern void thread_call_delayed_timer(timer_call_param_t p0, timer_call_param_t p1);

lck_grp_t               thread_call_lck_grp;
lck_mtx_t               thread_call_lock_data;

#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)

#define tc_deadline tc_call.deadline

extern boolean_t        mach_timer_coalescing_enabled;

static inline spl_t
disable_ints_and_lock(void)
{
        spl_t s = splsched();
        thread_call_lock_spin();

        return s;
}

static inline void
enable_ints_and_unlock(spl_t s)
{
        thread_call_unlock();
        splx(s);
}

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)
{
        if ((group->active_count + group->blocked_count + group->idle_count) >= THREAD_CALL_GROUP_MAX_THREADS) {
                panic("thread_call group '%s' reached max thread cap (%d): active: %d, blocked: %d, idle: %d",
                      group->tcg_name, THREAD_CALL_GROUP_MAX_THREADS,
                      group->active_count, group->blocked_count, group->idle_count);
        }

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

                return FALSE;
        }

        if (group->pending_count > 0) {
                if (group->idle_count > 0) {
                        return FALSE;
                }

                uint32_t 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;
}

/* Lock held */
static inline thread_call_group_t
thread_call_get_group(thread_call_t call)
{
        thread_call_index_t index = call->tc_index;

        assert(index >= 0 && index < THREAD_CALL_INDEX_MAX);

        return &thread_call_groups[index];
}

/* Lock held */
static inline thread_call_flavor_t
thread_call_get_flavor(thread_call_t call)
{
        return (call->tc_flags & THREAD_CALL_CONTINUOUS) ? TCF_CONTINUOUS : TCF_ABSOLUTE;
}

static void
thread_call_group_setup(thread_call_group_t group)
{
        queue_init(&group->pending_queue);
        queue_init(&group->delayed_queues[TCF_ABSOLUTE]);
        queue_init(&group->delayed_queues[TCF_CONTINUOUS]);

        /* TODO: Consolidate to one hard timer for each group */
        timer_call_setup(&group->delayed_timers[TCF_ABSOLUTE],   thread_call_delayed_timer, group);
        timer_call_setup(&group->delayed_timers[TCF_CONTINUOUS], thread_call_delayed_timer, group);
        timer_call_setup(&group->dealloc_timer, thread_call_dealloc_timer, group);

        /* Reverse the wait order so we re-use the most recently parked thread from the pool */
        waitq_init(&group->idle_waitq, SYNC_POLICY_REVERSED|SYNC_POLICY_DISABLE_IRQ);
}

/*
 * 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;

        int thread_pri = group->tcg_thread_pri;

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

        if (thread_pri <= BASEPRI_KERNEL) {
                /*
                 * THREAD_CALL_PRIORITY_KERNEL and lower don't get to run to completion
                 * in kernel if there are higher priority threads available.
                 */
                thread_set_eager_preempt(thread);
        }

        char name[MAXTHREADNAMESIZE] = "";

        int group_thread_count = group->idle_count + group->active_count + group->blocked_count;

        snprintf(name, sizeof(name), "thread call %s #%d", group->tcg_name, group_thread_count);
        thread_set_thread_name(thread, name);

        thread_deallocate(thread);
        return KERN_SUCCESS;
}

/*
 *      thread_call_initialize:
 *
 *      Initialize this module, called
 *      early during system initialization.
 */
void
thread_call_initialize(void)
{
        int tc_size = sizeof (thread_call_data_t);
        thread_call_zone = zinit(tc_size, 4096 * tc_size, 16 * tc_size, "thread_call");
        zone_change(thread_call_zone, Z_CALLERACCT, FALSE);
        zone_change(thread_call_zone, Z_NOENCRYPT, TRUE);

        lck_grp_init(&thread_call_lck_grp, "thread_call", LCK_GRP_ATTR_NULL);
        lck_mtx_init(&thread_call_lock_data, &thread_call_lck_grp, LCK_ATTR_NULL);

        nanotime_to_absolutetime(0, THREAD_CALL_DEALLOC_INTERVAL_NS, &thread_call_dealloc_interval_abs);
        waitq_init(&daemon_waitq, SYNC_POLICY_DISABLE_IRQ | SYNC_POLICY_FIFO);

        for (uint32_t i = 0; i < THREAD_CALL_INDEX_MAX; i++)
                thread_call_group_setup(&thread_call_groups[i]);

        spl_t s = disable_ints_and_lock();

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

                enqueue_tail(&thread_call_internal_queue, &call->tc_call.q_link);
                thread_call_internal_queue_count++;
        }

        thread_call_daemon_awake = TRUE;

        enable_ints_and_unlock(s);

        thread_t thread;
        kern_return_t result;

        result = kernel_thread_start_priority((thread_continue_t)thread_call_daemon,
                                              NULL, BASEPRI_PREEMPT_HIGH + 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);

        /* Thread calls default to the HIGH group unless otherwise specified */
        call->tc_index = THREAD_CALL_INDEX_HIGH;

        /* THREAD_CALL_ALLOC not set, memory owned by caller */
}

/*
 *      _internal_call_allocate:
 *
 *      Allocate an internal callout entry.
 *
 *      Called with thread_call_lock held.
 */
static __inline__ thread_call_t
_internal_call_allocate(thread_call_func_t func, thread_call_param_t param0)
{
    thread_call_t               call;
    
    if (queue_empty(&thread_call_internal_queue))
        panic("_internal_call_allocate");

        call = qe_dequeue_head(&thread_call_internal_queue, struct thread_call, tc_call.q_link);

    thread_call_internal_queue_count--;

    thread_call_setup(call, func, param0);
    call->tc_refs = 0;
    call->tc_flags = 0; /* THREAD_CALL_ALLOC not set, do not free back to zone */

    return (call);
}

/*
 *      _internal_call_release:
 *
 *      Release an internal callout entry which
 *      is no longer pending (or delayed). This is
 *      safe to call on a non-internal entry, in which
 *      case nothing happens.
 *
 *      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]) {
                assert((call->tc_flags & THREAD_CALL_ALLOC) == 0);
                enqueue_head(&thread_call_internal_queue, &call->tc_call.q_link);
                thread_call_internal_queue_count++;
        }
}

/*
 *      _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)
{
        if ((THREAD_CALL_ONCE | THREAD_CALL_RUNNING)
          == (call->tc_flags & (THREAD_CALL_ONCE | THREAD_CALL_RUNNING))) {
                call->tc_deadline = 0;

                uint32_t flags = call->tc_flags;
                call->tc_flags |= THREAD_CALL_RESCHEDULE;

                if ((flags & THREAD_CALL_RESCHEDULE) != 0)
                        return (TRUE);
                else
                        return (FALSE);
        }

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

        if (old_queue == NULL) {
                call->tc_submit_count++;
        } else if (old_queue != &group->pending_queue &&
                   old_queue != &group->delayed_queues[TCF_ABSOLUTE] &&
                   old_queue != &group->delayed_queues[TCF_CONTINUOUS]) {
                panic("tried to move a thread call (%p) between groups (old_queue: %p)", call, old_queue);
        }

        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 boolean_t
_delayed_call_enqueue(
        thread_call_t           call,
        thread_call_group_t     group,
        uint64_t                deadline,
        thread_call_flavor_t    flavor)
{
        if ((THREAD_CALL_ONCE | THREAD_CALL_RUNNING)
          == (call->tc_flags & (THREAD_CALL_ONCE | THREAD_CALL_RUNNING))) {
                call->tc_deadline = deadline;

                uint32_t flags = call->tc_flags;
                call->tc_flags |= THREAD_CALL_RESCHEDULE;

                if ((flags & THREAD_CALL_RESCHEDULE) != 0)
                        return (TRUE);
                else
                        return (FALSE);
        }

        queue_head_t *old_queue = call_entry_enqueue_deadline(CE(call),
                                                              &group->delayed_queues[flavor],
                                                              deadline);

        if (old_queue == &group->pending_queue) {
                group->pending_count--;
        } else if (old_queue == NULL) {
                call->tc_submit_count++;
        } else if (old_queue == &group->delayed_queues[TCF_ABSOLUTE] ||
                   old_queue == &group->delayed_queues[TCF_CONTINUOUS]) {
                /* TODO: if it's in the other delayed queue, that might not be OK */
                // we did nothing, and that's fine
        } else {
                panic("tried to move a thread call (%p) between groups (old_queue: %p)", call, old_queue);
        }

        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) {
                assert(old_queue == &group->pending_queue ||
                       old_queue == &group->delayed_queues[TCF_ABSOLUTE] ||
                       old_queue == &group->delayed_queues[TCF_CONTINUOUS]);

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

        return (old_queue != NULL);
}

/*
 * _arm_delayed_call_timer:
 *
 * Check if the timer needs to be armed for this flavor,
 * and if so, arm it.
 *
 * If call is non-NULL, only re-arm the timer if the specified call
 * is the first in the queue.
 *
 * Returns true if the timer was armed/re-armed, false if it was left unset
 * Caller should cancel the timer if need be.
 *
 * Called with thread_call_lock held.
 */
static bool
_arm_delayed_call_timer(thread_call_t           new_call,
                        thread_call_group_t     group,
                        thread_call_flavor_t    flavor)
{
        /* No calls implies no timer needed */
        if (queue_empty(&group->delayed_queues[flavor]))
                return false;

        thread_call_t call = qe_queue_first(&group->delayed_queues[flavor], struct thread_call, tc_call.q_link);

        /* We only need to change the hard timer if this new call is the first in the list */
        if (new_call != NULL && new_call != call)
                return false;

        assert((call->tc_soft_deadline != 0) && ((call->tc_soft_deadline <= call->tc_call.deadline)));

        uint64_t fire_at = call->tc_soft_deadline;

        if (flavor == TCF_CONTINUOUS) {
                assert((call->tc_flags & THREAD_CALL_CONTINUOUS) == THREAD_CALL_CONTINUOUS);
                fire_at = continuoustime_to_absolutetime(fire_at);
        } else {
                assert((call->tc_flags & THREAD_CALL_CONTINUOUS) == 0);
        }

        /*
         * Note: This picks the soonest-deadline call's leeway as the hard timer's leeway,
         * which does not take into account later-deadline timers with a larger leeway.
         * This is a valid coalescing behavior, but masks a possible window to
         * fire a timer instead of going idle.
         */
        uint64_t leeway = call->tc_call.deadline - call->tc_soft_deadline;

        timer_call_enter_with_leeway(&group->delayed_timers[flavor], (timer_call_param_t)flavor,
            fire_at, leeway,
            TIMER_CALL_SYS_CRITICAL|TIMER_CALL_LEEWAY,
            ((call->tc_flags & THREAD_CALL_RATELIMITED) == THREAD_CALL_RATELIMITED));

        return true;
}

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

        qe_foreach_element_safe(call, queue, tc_call.q_link) {
                if (call->tc_call.func   != func ||
                    call->tc_call.param0 != param0) {
                        continue;
                }

                _call_dequeue(call, group);

                _internal_call_release(call);

                call_removed = TRUE;
                if (!remove_all)
                        break;
        }

        return (call_removed);
}

/*
 *      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)
{
        (void)thread_call_enter_delayed_internal(NULL, func, param, 0, deadline, 0, 0);
}

/*
 * thread_call_func_delayed_with_leeway:
 *
 * Same as thread_call_func_delayed(), but with
 * leeway/flags threaded through.
 */

void
thread_call_func_delayed_with_leeway(
        thread_call_func_t              func,
        thread_call_param_t             param,
        uint64_t                deadline,
        uint64_t                leeway,
        uint32_t                flags)
{
        (void)thread_call_enter_delayed_internal(NULL, func, param, 0, deadline, leeway, flags);
}

/*
 *      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.
 *
 *      This iterates all of the pending or delayed thread calls in the group,
 *      which is really inefficient.  Switch to an allocated thread call instead.
 */
boolean_t
thread_call_func_cancel(
                thread_call_func_t              func,
                thread_call_param_t             param,
                boolean_t                       cancel_all)
{
        boolean_t       result;

        assert(func != NULL);

        spl_t s = disable_ints_and_lock();

        /* Function-only thread calls are only kept in the default HIGH group */
        thread_call_group_t group = &thread_call_groups[THREAD_CALL_INDEX_HIGH];

        if (cancel_all) {
                /* exhaustively search every queue, and return true if any search found something */
                result = _cancel_func_from_queue(func, param, group, cancel_all, &group->pending_queue) |
                         _cancel_func_from_queue(func, param, group, cancel_all, &group->delayed_queues[TCF_ABSOLUTE])  |
                         _cancel_func_from_queue(func, param, group, cancel_all, &group->delayed_queues[TCF_CONTINUOUS]);
        } else {
                /* early-exit as soon as we find something, don't search other queues */
                result = _cancel_func_from_queue(func, param, group, cancel_all, &group->pending_queue) ||
                         _cancel_func_from_queue(func, param, group, cancel_all, &group->delayed_queues[TCF_ABSOLUTE]) ||
                         _cancel_func_from_queue(func, param, group, cancel_all, &group->delayed_queues[TCF_CONTINUOUS]);
        }

        enable_ints_and_unlock(s);

        return (result);
}

/*
 * Allocate a thread call with a given priority.  Importances other than
 * THREAD_CALL_PRIORITY_HIGH or THREAD_CALL_PRIORITY_KERNEL_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)
{
        return thread_call_allocate_with_options(func, param0, pri, 0);
}

thread_call_t
thread_call_allocate_with_options(
                thread_call_func_t              func,
                thread_call_param_t             param0,
                thread_call_priority_t          pri,
                thread_call_options_t           options)
{
        thread_call_t call = thread_call_allocate(func, param0);

        switch (pri) {
                case THREAD_CALL_PRIORITY_HIGH:
                        call->tc_index = THREAD_CALL_INDEX_HIGH;
                        break;
                case THREAD_CALL_PRIORITY_KERNEL:
                        call->tc_index = THREAD_CALL_INDEX_KERNEL;
                        break;
                case THREAD_CALL_PRIORITY_USER:
                        call->tc_index = THREAD_CALL_INDEX_USER;
                        break;
                case THREAD_CALL_PRIORITY_LOW:
                        call->tc_index = THREAD_CALL_INDEX_LOW;
                        break;
                case THREAD_CALL_PRIORITY_KERNEL_HIGH:
                        call->tc_index = THREAD_CALL_INDEX_KERNEL_HIGH;
                        break;
                default:
                        panic("Invalid thread call pri value: %d", pri);
                        break;
        }

        if (options & THREAD_CALL_OPTIONS_ONCE) {
            call->tc_flags |= THREAD_CALL_ONCE;
        }
        if (options & THREAD_CALL_OPTIONS_SIGNAL) {
            call->tc_flags |= THREAD_CALL_SIGNAL | THREAD_CALL_ONCE;
        }

        return call;
}

thread_call_t
thread_call_allocate_with_qos(thread_call_func_t        func,
                              thread_call_param_t       param0,
                              int                       qos_tier,
                              thread_call_options_t     options)
{
        thread_call_t call = thread_call_allocate(func, param0);

        switch (qos_tier) {
                case THREAD_QOS_UNSPECIFIED:
                        call->tc_index = THREAD_CALL_INDEX_HIGH;
                        break;
                case THREAD_QOS_LEGACY:
                        call->tc_index = THREAD_CALL_INDEX_USER;
                        break;
                case THREAD_QOS_MAINTENANCE:
                case THREAD_QOS_BACKGROUND:
                        call->tc_index = THREAD_CALL_INDEX_LOW;
                        break;
                case THREAD_QOS_UTILITY:
                        call->tc_index = THREAD_CALL_INDEX_QOS_UT;
                        break;
                case THREAD_QOS_USER_INITIATED:
                        call->tc_index = THREAD_CALL_INDEX_QOS_IN;
                        break;
                case THREAD_QOS_USER_INTERACTIVE:
                        call->tc_index = THREAD_CALL_INDEX_QOS_UI;
                        break;
                default:
                        panic("Invalid thread call qos value: %d", qos_tier);
                        break;
        }

        if (options & THREAD_CALL_OPTIONS_ONCE)
                call->tc_flags |= THREAD_CALL_ONCE;

        /* does not support THREAD_CALL_OPTIONS_SIGNAL */

        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.
 *
 *      If the callout is currently armed to fire again, then
 *      freeing is not allowed and returns FALSE.  The
 *      client must have canceled the pending invocation before freeing.
 */
boolean_t
thread_call_free(
                thread_call_t           call)
{
        spl_t s = disable_ints_and_lock();

        if (call->tc_call.queue != NULL ||
           ((call->tc_flags & THREAD_CALL_RESCHEDULE) != 0)) {
                thread_call_unlock();
                splx(s);

                return (FALSE);
        }

        int32_t refs = --call->tc_refs;
        if (refs < 0) {
                panic("Refcount negative: %d\n", refs);
        }

        if ((THREAD_CALL_SIGNAL | THREAD_CALL_RUNNING)
          == ((THREAD_CALL_SIGNAL | THREAD_CALL_RUNNING) & call->tc_flags)) {
                thread_call_wait_once_locked(call, s);
                /* thread call lock has been unlocked */
        } else {
                enable_ints_and_unlock(s);
        }

        if (refs == 0) {
                assert(call->tc_finish_count == call->tc_submit_count);
                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)
{
        return thread_call_enter1(call, 0);
}

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

        assert(call->tc_call.func != NULL);

        assert((call->tc_flags & THREAD_CALL_SIGNAL) == 0);

        group = thread_call_get_group(call);

        spl_t s = disable_ints_and_lock();

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

        call->tc_call.param1 = param1;

        enable_ints_and_unlock(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)
{
        assert(call != NULL);
        return thread_call_enter_delayed_internal(call, NULL, 0, 0, deadline, 0, 0);
}

boolean_t
thread_call_enter1_delayed(
                thread_call_t                   call,
                thread_call_param_t             param1,
                uint64_t                        deadline)
{
        assert(call != NULL);
        return thread_call_enter_delayed_internal(call, NULL, 0, param1, deadline, 0, 0);
}

boolean_t
thread_call_enter_delayed_with_leeway(
                thread_call_t           call,
                thread_call_param_t     param1,
                uint64_t                deadline,
                uint64_t                leeway,
                unsigned int            flags)
{
        assert(call != NULL);
        return thread_call_enter_delayed_internal(call, NULL, 0, param1, deadline, leeway, flags);
}


/*
 * thread_call_enter_delayed_internal:
 * enqueue a callout entry to occur at the stated time
 *
 * Returns True if the call was already on a queue
 * params:
 * call     - structure encapsulating state of the callout
 * alt_func/alt_param0 - if call is NULL, allocate temporary storage using these parameters
 * deadline - time deadline in nanoseconds
 * leeway   - timer slack represented as delta of deadline.
 * flags    - THREAD_CALL_DELAY_XXX : classification of caller's desires wrt timer coalescing.
 *            THREAD_CALL_DELAY_LEEWAY : value in leeway is used for timer coalescing.
 *            THREAD_CALL_CONTINUOUS: thread call will be called according to mach_continuous_time rather
 *                                                                        than mach_absolute_time
 */
boolean_t
thread_call_enter_delayed_internal(
                thread_call_t           call,
                thread_call_func_t      alt_func,
                thread_call_param_t     alt_param0,
                thread_call_param_t     param1,
                uint64_t                deadline,
                uint64_t                leeway,
                unsigned int            flags)
{
        boolean_t               result = TRUE;
        thread_call_group_t     group;
        uint64_t                now, sdeadline, slop;
        uint32_t                urgency;

        thread_call_flavor_t flavor = (flags & THREAD_CALL_CONTINUOUS) ? TCF_CONTINUOUS : TCF_ABSOLUTE;

        /* direct mapping between thread_call, timer_call, and timeout_urgency values */
        urgency = (flags & TIMEOUT_URGENCY_MASK);

        spl_t s = disable_ints_and_lock();

        if (call == NULL) {
                /* allocate a structure out of internal storage, as a convenience for BSD callers */
                call = _internal_call_allocate(alt_func, alt_param0);
        }

        assert(call->tc_call.func != NULL);
        group = thread_call_get_group(call);

        /* TODO: assert that call is not enqueued before flipping the flag */
        if (flavor == TCF_CONTINUOUS) {
                now = mach_continuous_time();
                call->tc_flags |= THREAD_CALL_CONTINUOUS;
        } else {
                now = mach_absolute_time();
                call->tc_flags &= ~THREAD_CALL_CONTINUOUS;
        }

        call->tc_flags |= THREAD_CALL_DELAYED;

        call->tc_soft_deadline = sdeadline = deadline;

        boolean_t ratelimited = FALSE;
        slop = timer_call_slop(deadline, now, urgency, current_thread(), &ratelimited);

        if ((flags & THREAD_CALL_DELAY_LEEWAY) != 0 && leeway > slop)
                slop = leeway;

        if (UINT64_MAX - deadline <= slop)
                deadline = UINT64_MAX;
        else
                deadline += slop;

        if (ratelimited) {
                call->tc_flags |= TIMER_CALL_RATELIMITED;
        } else {
                call->tc_flags &= ~TIMER_CALL_RATELIMITED;
        }

        call->tc_call.param1 = param1;

        call->tc_ttd = (sdeadline > now) ? (sdeadline - now) : 0;

        result = _delayed_call_enqueue(call, group, deadline, flavor);

        _arm_delayed_call_timer(call, group, flavor);

#if CONFIG_DTRACE
        DTRACE_TMR5(thread_callout__create, thread_call_func_t, call->tc_call.func,
                    uint64_t, (deadline - sdeadline), uint64_t, (call->tc_ttd >> 32),
                    (unsigned) (call->tc_ttd & 0xFFFFFFFF), call);
#endif

        enable_ints_and_unlock(s);

        return (result);
}

/*
 * Remove a callout entry from the queue
 * Called with thread_call_lock held
 */
static boolean_t
thread_call_cancel_locked(thread_call_t call)
{
        boolean_t canceled = (0 != (THREAD_CALL_RESCHEDULE & call->tc_flags));
        call->tc_flags &= ~THREAD_CALL_RESCHEDULE;

        if (canceled) {
                /* if reschedule was set, it must not have been queued */
                assert(call->tc_call.queue == NULL);
        } else {
                boolean_t do_cancel_callout = FALSE;

                thread_call_flavor_t flavor = thread_call_get_flavor(call);
                thread_call_group_t  group  = thread_call_get_group(call);

                if ((call->tc_call.deadline != 0) &&
                    (call == qe_queue_first(&group->delayed_queues[flavor], struct thread_call, tc_call.q_link))) {
                        assert(call->tc_call.queue == &group->delayed_queues[flavor]);
                        do_cancel_callout = TRUE;
                }

                canceled = _call_dequeue(call, group);

                if (do_cancel_callout) {
                        if (_arm_delayed_call_timer(NULL, group, flavor) == false)
                                timer_call_cancel(&group->delayed_timers[flavor]);
                }
        }

#if CONFIG_DTRACE
        DTRACE_TMR4(thread_callout__cancel, thread_call_func_t, call->tc_call.func,
                    0, (call->tc_ttd >> 32), (unsigned) (call->tc_ttd & 0xFFFFFFFF));
#endif

        return canceled;
}

/*
 *      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)
{
        spl_t s = disable_ints_and_lock();

        boolean_t result = thread_call_cancel_locked(call);

        enable_ints_and_unlock(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)
{
        if ((call->tc_flags & THREAD_CALL_ALLOC) == 0)
                panic("thread_call_cancel_wait: can't wait on thread call whose storage I don't own");

        if (!ml_get_interrupts_enabled())
                panic("unsafe thread_call_cancel_wait");

        if (current_thread()->thc_state.thc_call == call)
                panic("thread_call_cancel_wait: deadlock waiting on self from inside call: %p to function %p",
                      call, call->tc_call.func);

        spl_t s = disable_ints_and_lock();

        boolean_t canceled = thread_call_cancel_locked(call);

        if ((call->tc_flags & THREAD_CALL_ONCE) == THREAD_CALL_ONCE) {
                /*
                 * A cancel-wait on a 'once' call will both cancel
                 * the pending call and wait for the in-flight call
                 */

                thread_call_wait_once_locked(call, s);
                /* thread call lock unlocked */
        } else {
                /*
                 * A cancel-wait on a normal call will only wait for the in-flight calls
                 * if it did not cancel the pending call.
                 *
                 * TODO: This seems less than useful - shouldn't it do the wait as well?
                 */

                if (canceled == FALSE) {
                        thread_call_wait_locked(call, s);
                        /* thread call lock unlocked */
                } else {
                        enable_ints_and_unlock(s);
                }
        }

        return canceled;
}


/*
 *      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 (waitq_wakeup64_one(&group->idle_waitq, NO_EVENT64,
                                       THREAD_AWAKENED, WAITQ_ALL_PRIORITIES) == 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;
                                waitq_wakeup64_one(&daemon_waitq, NO_EVENT64,
                                                   THREAD_AWAKENED, WAITQ_ALL_PRIORITIES);
                        }
                }
        }
}

/*
 *      sched_call_thread:
 *
 *      Call out invoked by the scheduler.
 */
static void
sched_call_thread(
                int                             type,
                thread_t                thread)
{
        thread_call_group_t             group;

        group = thread->thc_state.thc_group;
        assert((group - &thread_call_groups[0]) < THREAD_CALL_INDEX_MAX);

        thread_call_lock_spin();

        switch (type) {

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

                case SCHED_CALL_UNBLOCK:
                        assert(group->blocked_count);
                        --group->blocked_count;
                        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 boolean_t
thread_call_finish(thread_call_t call, thread_call_group_t group, spl_t *s)
{
        uint64_t  time;
        uint32_t  flags;
        boolean_t signal;
        boolean_t dowake = FALSE;
        boolean_t repend = FALSE;

        call->tc_finish_count++;
        flags = call->tc_flags;
        signal = ((THREAD_CALL_SIGNAL & flags) != 0);

    if (!signal) {
                /* The thread call thread owns a ref until the call is finished */
                if (call->tc_refs <= 0)
                        panic("thread_call_finish: detected over-released thread call: %p", call);
                call->tc_refs--;
    }

        call->tc_flags &= ~(THREAD_CALL_RESCHEDULE | THREAD_CALL_RUNNING | THREAD_CALL_WAIT);

        if ((call->tc_refs != 0) && ((flags & THREAD_CALL_RESCHEDULE) != 0)) {
                assert(flags & THREAD_CALL_ONCE);
                thread_call_flavor_t flavor = thread_call_get_flavor(call);

                if (THREAD_CALL_DELAYED & flags) {
                        time =  mach_absolute_time();
                        if (flavor == TCF_CONTINUOUS) {
                                time =  absolutetime_to_continuoustime(time);
                        }
                        if (call->tc_soft_deadline <= time) {
                                call->tc_flags &= ~(THREAD_CALL_DELAYED | TIMER_CALL_RATELIMITED);
                                call->tc_deadline = 0;
                        }
                }
                if (call->tc_deadline) {
                        _delayed_call_enqueue(call, group, call->tc_deadline, flavor);
                        if (!signal) {
                                _arm_delayed_call_timer(call, group, flavor);
                        }
                } else if (signal) {
                        call->tc_submit_count++;
                        repend = TRUE;
                } else {
                        _pending_call_enqueue(call, group);
                }
        }

        if ((flags & THREAD_CALL_WAIT) != 0) {
                dowake = TRUE;

                /* 
                 * 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();
                /* THREAD_CALL_SIGNAL call may have been freed */
        }

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

                assert(call->tc_finish_count == call->tc_submit_count);

                enable_ints_and_unlock(*s);

                zfree(thread_call_zone, call);

                *s = disable_ints_and_lock();
        }

        return (repend);
}

/*
 * thread_call_invoke
 *
 * Invoke the function provided for this thread call
 *
 * Note that the thread call object can be deallocated by the function if we do not control its storage.
 */
static void __attribute__((noinline))
thread_call_invoke(thread_call_func_t func, thread_call_param_t param0, thread_call_param_t param1, thread_call_t call)
{
        current_thread()->thc_state.thc_call = call;

#if DEVELOPMENT || DEBUG
        KERNEL_DEBUG_CONSTANT(
                              MACHDBG_CODE(DBG_MACH_SCHED,MACH_CALLOUT) | DBG_FUNC_START,
                              VM_KERNEL_UNSLIDE(func), VM_KERNEL_ADDRHIDE(param0), VM_KERNEL_ADDRHIDE(param1), 0, 0);
#endif /* DEVELOPMENT || DEBUG */

#if CONFIG_DTRACE
        uint64_t tc_ttd = call->tc_ttd;
        boolean_t is_delayed = call->tc_flags & THREAD_CALL_DELAYED;
        DTRACE_TMR6(thread_callout__start, thread_call_func_t, func, int, 0, int, (tc_ttd >> 32),
                    (unsigned) (tc_ttd & 0xFFFFFFFF), is_delayed, call);
#endif

        (*func)(param0, param1);

#if CONFIG_DTRACE
        DTRACE_TMR6(thread_callout__end, thread_call_func_t, func, int, 0, int, (tc_ttd >> 32),
                    (unsigned) (tc_ttd & 0xFFFFFFFF), is_delayed, call);
#endif

#if DEVELOPMENT || DEBUG
        KERNEL_DEBUG_CONSTANT(
                              MACHDBG_CODE(DBG_MACH_SCHED,MACH_CALLOUT) | DBG_FUNC_END,
                              VM_KERNEL_UNSLIDE(func), 0, 0, 0, 0);
#endif /* DEVELOPMENT || DEBUG */

        current_thread()->thc_state.thc_call = NULL;
}

/*
 *      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;

        if ((thread_get_tag_internal(self) & THREAD_TAG_CALLOUT) == 0)
                (void)thread_set_tag_internal(self, THREAD_TAG_CALLOUT);

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

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

        spl_t s = disable_ints_and_lock();

        self->thc_state.thc_group = group;
        thread_sched_call(self, sched_call_thread);

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

                call = qe_dequeue_head(&group->pending_queue, struct thread_call, tc_call.q_link);
                assert(call != NULL);
                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_flags |= THREAD_CALL_RUNNING;
                        call->tc_refs++;        /* Delay free until we're done */
                } else
                        canwait = FALSE;

                enable_ints_and_unlock(s);

                thread_call_invoke(func, param0, param1, call);

                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);
                }

                s = disable_ints_and_lock();

                if (canwait) {
                        /* Frees if so desired */
                        thread_call_finish(call, group, &s);
                }
        }

        thread_sched_call(self, NULL);
        group->active_count--;
        
        if (self->callout_woken_from_icontext && !self->callout_woke_thread) {
                ledger_credit(self->t_ledger, task_ledgers.interrupt_wakeups, 1);
                if (self->callout_woken_from_platform_idle)
                        ledger_credit(self->t_ledger, task_ledgers.platform_idle_wakeups, 1);
        }
        
        self->callout_woken_from_icontext = FALSE;
        self->callout_woken_from_platform_idle = FALSE;
        self->callout_woke_thread = FALSE;

        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 = waitq_assert_wait64(&group->idle_waitq, NO_EVENT64, THREAD_INTERRUPTIBLE, 0);
                if (wres != THREAD_WAITING) {
                        panic("kcall worker unable to assert wait?");
                }   

                enable_ints_and_unlock(s);

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

                        waitq_assert_wait64(&group->idle_waitq, NO_EVENT64, THREAD_UNINT, 0); /* Interrupted means to exit */

                        enable_ints_and_unlock(s);

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

        enable_ints_and_unlock(s);

        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)
{
        spl_t s = disable_ints_and_lock();

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

                        enable_ints_and_unlock(s);

                        kern_return_t 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 */
                                s = disable_ints_and_lock();
                                goto out;
                        }

                        s = disable_ints_and_lock();
                }
        }

out:
        thread_call_daemon_awake = FALSE;
        waitq_assert_wait64(&daemon_waitq, NO_EVENT64, THREAD_UNINT, 0);

        enable_ints_and_unlock(s);

        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_set_thread_name(self, "thread_call_daemon");

        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?");
        }   
}

/* non-static so dtrace can find it rdar://problem/31156135&31379348 */
void
thread_call_delayed_timer(timer_call_param_t p0, timer_call_param_t p1)
{
        thread_call_group_t  group  = (thread_call_group_t)  p0;
        thread_call_flavor_t flavor = (thread_call_flavor_t) p1;

        thread_call_t   call;
        uint64_t        now;
        boolean_t       restart;
        boolean_t       repend;

        thread_call_lock_spin();

        if (flavor == TCF_CONTINUOUS)
                now = mach_continuous_time();
        else if (flavor == TCF_ABSOLUTE)
                now = mach_absolute_time();
        else
                panic("invalid timer flavor: %d", flavor);

    do {
                restart = FALSE;
                qe_foreach_element_safe(call, &group->delayed_queues[flavor], tc_call.q_link) {
                        if (flavor == TCF_CONTINUOUS)
                                assert((call->tc_flags & THREAD_CALL_CONTINUOUS) == THREAD_CALL_CONTINUOUS);
                        else
                                assert((call->tc_flags & THREAD_CALL_CONTINUOUS) == 0);

                        /*
                         * if we hit a call that isn't yet ready to expire,
                         * then we're done for now
                         * TODO: The next timer in the list could have a larger leeway
                         *       and therefore be ready to expire.
                         *       Sort by deadline then by soft deadline to avoid this
                         */
                        if (call->tc_soft_deadline > now)
                                break;

                        /*
                         * If we hit a rate-limited timer, don't eagerly wake it up.
                         * Wait until it reaches the end of the leeway window.
                         *
                         * TODO: What if the next timer is not rate-limited?
                         *       Have a separate rate-limited queue to avoid this
                         */
                        if ((call->tc_flags & THREAD_CALL_RATELIMITED) &&
                            (call->tc_call.deadline > now) &&
                            (ml_timer_forced_evaluation() == FALSE)) {
                                break;
                        }

                        if (THREAD_CALL_SIGNAL & call->tc_flags) {
                                __assert_only queue_head_t *old_queue;
                                old_queue = call_entry_dequeue(&call->tc_call);
                                assert(old_queue == &group->delayed_queues[flavor]);

                do {
                                        thread_call_func_t  func   = call->tc_call.func;
                                        thread_call_param_t param0 = call->tc_call.param0;
                                        thread_call_param_t param1 = call->tc_call.param1;

                                        call->tc_flags |= THREAD_CALL_RUNNING;
                                        thread_call_unlock();
                                        thread_call_invoke(func, param0, param1, call);
                                        thread_call_lock_spin();

                                        repend = thread_call_finish(call, group, NULL);
                } while (repend);

                                /* call may have been freed */
                                restart = TRUE;
                                break;
                        } else {
                                _pending_call_enqueue(call, group);
                        }
                }
        } while (restart);

        _arm_delayed_call_timer(call, group, flavor);

        thread_call_unlock();
}

static void
thread_call_delayed_timer_rescan(thread_call_group_t group,
                                 thread_call_flavor_t flavor)
{
        thread_call_t call;
        uint64_t now;

        spl_t s = disable_ints_and_lock();

        assert(ml_timer_forced_evaluation() == TRUE);

        if (flavor == TCF_CONTINUOUS) {
                now = mach_continuous_time();
        } else {
                now = mach_absolute_time();
        }

        qe_foreach_element_safe(call, &group->delayed_queues[flavor], tc_call.q_link) {
                if (call->tc_soft_deadline <= now) {
                        _pending_call_enqueue(call, group);
                } else {
                        uint64_t skew = call->tc_call.deadline - call->tc_soft_deadline;
                        assert (call->tc_call.deadline >= call->tc_soft_deadline);
                        /*
                         * On a latency quality-of-service level change,
                         * re-sort potentially rate-limited callout. The platform
                         * layer determines which timers require this.
                         */
                        if (timer_resort_threshold(skew)) {
                                _call_dequeue(call, group);
                                _delayed_call_enqueue(call, group, call->tc_soft_deadline, flavor);
                        }
                }
        }

        _arm_delayed_call_timer(NULL, group, flavor);

        enable_ints_and_unlock(s);
}

void
thread_call_delayed_timer_rescan_all(void) {
        for (int i = 0; i < THREAD_CALL_INDEX_MAX; i++) {
                thread_call_delayed_timer_rescan(&thread_call_groups[i], TCF_ABSOLUTE);
                thread_call_delayed_timer_rescan(&thread_call_groups[i], TCF_CONTINUOUS);
        }
}

/*
 * 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 = waitq_wakeup64_one(&group->idle_waitq, NO_EVENT64,
                                                 THREAD_INTERRUPTED, WAITQ_ALL_PRIORITIES);
                        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 the invocation of the thread call to complete
 * We know there's only one in flight because of the 'once' flag.
 *
 * If a subsequent invocation comes in before we wake up, that's OK
 *
 * TODO: Here is where we will add priority inheritance to the thread executing
 * the thread call in case it's lower priority than the current thread
 *      <rdar://problem/30321792> Priority inheritance for thread_call_wait_once
 *
 * Takes the thread call lock locked, returns unlocked
 *      This lets us avoid a spurious take/drop after waking up from thread_block
 */
static boolean_t
thread_call_wait_once_locked(thread_call_t call, spl_t s)
{
        assert(call->tc_flags & THREAD_CALL_ALLOC);
        assert(call->tc_flags & THREAD_CALL_ONCE);

        if ((call->tc_flags & THREAD_CALL_RUNNING) == 0) {
                enable_ints_and_unlock(s);
                return FALSE;
        }

        /* call is running, so we have to wait for it */
        call->tc_flags |= THREAD_CALL_WAIT;

        wait_result_t res = assert_wait(call, THREAD_UNINT);
        if (res != THREAD_WAITING)
                panic("Unable to assert wait: %d", res);

        enable_ints_and_unlock(s);

        res = thread_block(THREAD_CONTINUE_NULL);
        if (res != THREAD_AWAKENED)
                panic("Awoken with %d?", res);

        /* returns unlocked */
        return TRUE;
}

/*
 * Wait for an in-flight invocation to complete
 * Does NOT try to cancel, so the client doesn't need to hold their
 * lock while calling this function.
 *
 * Returns whether or not it had to wait.
 *
 * Only works for THREAD_CALL_ONCE calls.
 */
boolean_t
thread_call_wait_once(thread_call_t call)
{
        if ((call->tc_flags & THREAD_CALL_ALLOC) == 0)
                panic("thread_call_wait_once: can't wait on thread call whose storage I don't own");

        if ((call->tc_flags & THREAD_CALL_ONCE) == 0)
                panic("thread_call_wait_once: can't wait_once on a non-once call");

        if (!ml_get_interrupts_enabled())
                panic("unsafe thread_call_wait_once");

        if (current_thread()->thc_state.thc_call == call)
                panic("thread_call_wait_once: deadlock waiting on self from inside call: %p to function %p",
                      call, call->tc_call.func);

        spl_t s = disable_ints_and_lock();

        boolean_t waited = thread_call_wait_once_locked(call, s);
        /* thread call lock unlocked */

        return waited;
}


/*
 * 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.
 *
 * Called with thread_call_lock held.  Returns with lock released.
 */
static void
thread_call_wait_locked(thread_call_t call, spl_t s)
{
        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: %d", res);

                enable_ints_and_unlock(s);

                res = thread_block(THREAD_CONTINUE_NULL);
                if (res != THREAD_AWAKENED)
                        panic("Awoken with %d?", res);

                s = disable_ints_and_lock();
        }

        enable_ints_and_unlock(s);
}

/*
 * 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;

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

        return active;
}

/*
 * adjust_cont_time_thread_calls
 * on wake, reenqueue delayed call timer for continuous time thread call groups
 */
void
adjust_cont_time_thread_calls(void)
{
        spl_t s = disable_ints_and_lock();

        for (int i = 0; i < THREAD_CALL_INDEX_MAX; i++) {
                thread_call_group_t group = &thread_call_groups[i];

                /* only the continuous timers need to be re-armed */

                _arm_delayed_call_timer(NULL, group, TCF_CONTINUOUS);
        }

        enable_ints_and_unlock(s);
}