xnu-3247.1.106.tar.gz

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

/*
 * Copyright (c) 2000-2015 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@
 */
/*
 * @OSF_FREE_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 */
/*
 *      File:   kern/thread.c
 *      Author: Avadis Tevanian, Jr., Michael Wayne Young, David Golub
 *      Date:   1986
 *
 *      Thread management primitives implementation.
 */
/*
 * Copyright (c) 1993 The University of Utah and
 * the Computer Systems Laboratory (CSL).  All rights reserved.
 *
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
 * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSL DISCLAIM ANY LIABILITY OF
 * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * CSL requests users of this software to return to csl-dist@cs.utah.edu any
 * improvements that they make and grant CSL redistribution rights.
 *
 */

#include <mach/mach_types.h>
#include <mach/boolean.h>
#include <mach/policy.h>
#include <mach/thread_info.h>
#include <mach/thread_special_ports.h>
#include <mach/thread_status.h>
#include <mach/time_value.h>
#include <mach/vm_param.h>

#include <machine/thread.h>
#include <machine/pal_routines.h>
#include <machine/limits.h>

#include <kern/kern_types.h>
#include <kern/kalloc.h>
#include <kern/cpu_data.h>
#include <kern/counters.h>
#include <kern/extmod_statistics.h>
#include <kern/ipc_mig.h>
#include <kern/ipc_tt.h>
#include <kern/mach_param.h>
#include <kern/machine.h>
#include <kern/misc_protos.h>
#include <kern/processor.h>
#include <kern/queue.h>
#include <kern/sched.h>
#include <kern/sched_prim.h>
#include <kern/sync_lock.h>
#include <kern/syscall_subr.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/host.h>
#include <kern/zalloc.h>
#include <kern/assert.h>
#include <kern/exc_resource.h>
#include <kern/telemetry.h>
#include <corpses/task_corpse.h>
#if KPC
#include <kern/kpc.h>
#endif

#include <ipc/ipc_kmsg.h>
#include <ipc/ipc_port.h>
#include <bank/bank_types.h>

#include <vm/vm_kern.h>
#include <vm/vm_pageout.h>

#include <sys/kdebug.h>
#include <sys/bsdtask_info.h>
#include <mach/sdt.h>

/*
 * Exported interfaces
 */
#include <mach/task_server.h>
#include <mach/thread_act_server.h>
#include <mach/mach_host_server.h>
#include <mach/host_priv_server.h>
#include <mach/mach_voucher_server.h>

static struct zone                      *thread_zone;
static lck_grp_attr_t           thread_lck_grp_attr;
lck_attr_t                                      thread_lck_attr;
lck_grp_t                                       thread_lck_grp;

struct zone                                     *thread_qos_override_zone;

decl_simple_lock_data(static,thread_stack_lock)
static queue_head_t             thread_stack_queue;

decl_simple_lock_data(static,thread_terminate_lock)
static queue_head_t             thread_terminate_queue;

static queue_head_t             crashed_threads_queue;

static struct thread    thread_template, init_thread;

static void             sched_call_null(
                                        int                     type,
                                        thread_t        thread);

#ifdef MACH_BSD
extern void proc_exit(void *);
extern uint64_t get_dispatchqueue_offset_from_proc(void *);
extern int      proc_selfpid(void);
extern char *   proc_name_address(void *p);
#endif /* MACH_BSD */

extern int disable_exc_resource;
extern int audio_active;
extern int debug_task;
int thread_max = CONFIG_THREAD_MAX;     /* Max number of threads */
int task_threadmax = CONFIG_THREAD_MAX;

static uint64_t         thread_unique_id = 100;

struct _thread_ledger_indices thread_ledgers = { -1 };
static ledger_template_t thread_ledger_template = NULL;
void init_thread_ledgers(void);
int task_disable_cpumon(task_t task);

#if CONFIG_JETSAM
void jetsam_on_ledger_cpulimit_exceeded(void);
#endif

/*
 * Level (in terms of percentage of the limit) at which the CPU usage monitor triggers telemetry.
 *
 * (ie when any thread's CPU consumption exceeds 70% of the limit, start taking user
 *  stacktraces, aka micro-stackshots)
 */
#define CPUMON_USTACKSHOTS_TRIGGER_DEFAULT_PCT 70

int cpumon_ustackshots_trigger_pct; /* Percentage. Level at which we start gathering telemetry. */
void __attribute__((noinline)) THIS_THREAD_IS_CONSUMING_TOO_MUCH_CPU__SENDING_EXC_RESOURCE(void);

/*
 * The smallest interval over which we support limiting CPU consumption is 1ms
 */
#define MINIMUM_CPULIMIT_INTERVAL_MS 1

void
thread_bootstrap(void)
{
        /*
         *      Fill in a template thread for fast initialization.
         */

        thread_template.runq = PROCESSOR_NULL;

        thread_template.ref_count = 2;

        thread_template.reason = AST_NONE;
        thread_template.at_safe_point = FALSE;
        thread_template.wait_event = NO_EVENT64;
        thread_template.waitq = NULL;
        thread_template.wait_result = THREAD_WAITING;
        thread_template.options = THREAD_ABORTSAFE;
        thread_template.state = TH_WAIT | TH_UNINT;
        thread_template.wake_active = FALSE;
        thread_template.continuation = THREAD_CONTINUE_NULL;
        thread_template.parameter = NULL;

        thread_template.importance = 0;
        thread_template.sched_mode = TH_MODE_NONE;
        thread_template.sched_flags = 0;
        thread_template.saved_mode = TH_MODE_NONE;
        thread_template.safe_release = 0;

        thread_template.sfi_class = SFI_CLASS_UNSPECIFIED;
        thread_template.sfi_wait_class = SFI_CLASS_UNSPECIFIED;

        thread_template.active = 0;
        thread_template.started = 0;
        thread_template.static_param = 0;
        thread_template.policy_reset = 0;

        thread_template.base_pri = 0;
        thread_template.sched_pri = 0;
        thread_template.max_priority = 0;
        thread_template.task_priority = 0;
        thread_template.promotions = 0;
        thread_template.pending_promoter_index = 0;
        thread_template.pending_promoter[0] = NULL;
        thread_template.pending_promoter[1] = NULL;
        thread_template.rwlock_count = 0;

#if MACH_ASSERT
        thread_template.SHARE_COUNT = 0;
        thread_template.BG_COUNT = 0;
#endif /* MACH_ASSERT */        

        thread_template.realtime.deadline = UINT64_MAX;

        thread_template.quantum_remaining = 0;
        thread_template.last_run_time = 0;
        thread_template.last_made_runnable_time = 0;

        thread_template.computation_metered = 0;
        thread_template.computation_epoch = 0;

#if defined(CONFIG_SCHED_TIMESHARE_CORE)
        thread_template.sched_stamp = 0;
        thread_template.pri_shift = INT8_MAX;
        thread_template.sched_usage = 0;
        thread_template.cpu_usage = thread_template.cpu_delta = 0;
#endif
        thread_template.c_switch = thread_template.p_switch = thread_template.ps_switch = 0;

        thread_template.bound_processor = PROCESSOR_NULL;
        thread_template.last_processor = PROCESSOR_NULL;

        thread_template.sched_call = sched_call_null;

        timer_init(&thread_template.user_timer);
        timer_init(&thread_template.system_timer);
        thread_template.user_timer_save = 0;
        thread_template.system_timer_save = 0;
        thread_template.vtimer_user_save = 0;
        thread_template.vtimer_prof_save = 0;
        thread_template.vtimer_rlim_save = 0;

#if CONFIG_SCHED_SFI
        thread_template.wait_sfi_begin_time = 0;
#endif

        thread_template.wait_timer_is_set = FALSE;
        thread_template.wait_timer_active = 0;

        thread_template.depress_timer_active = 0;

        thread_template.recover = (vm_offset_t)NULL;
        
        thread_template.map = VM_MAP_NULL;

#if CONFIG_DTRACE
        thread_template.t_dtrace_predcache = 0;
        thread_template.t_dtrace_vtime = 0;
        thread_template.t_dtrace_tracing = 0;
#endif /* CONFIG_DTRACE */

#if KPC
        thread_template.kpc_buf = NULL;
#endif

#if HYPERVISOR
        thread_template.hv_thread_target = NULL;
#endif /* HYPERVISOR */

        thread_template.t_chud = 0;

#if (DEVELOPMENT || DEBUG)
        thread_template.t_page_creation_throttled_hard = 0;
        thread_template.t_page_creation_throttled_soft = 0;
#endif /* DEVELOPMENT || DEBUG */
        thread_template.t_page_creation_throttled = 0;
        thread_template.t_page_creation_count = 0;
        thread_template.t_page_creation_time = 0;

        thread_template.affinity_set = NULL;
        
        thread_template.syscalls_unix = 0;
        thread_template.syscalls_mach = 0;

        thread_template.t_ledger = LEDGER_NULL;
        thread_template.t_threadledger = LEDGER_NULL;
#ifdef CONFIG_BANK
        thread_template.t_bankledger = LEDGER_NULL;
        thread_template.t_deduct_bank_ledger_time = 0;
#endif

        thread_template.requested_policy = default_task_requested_policy;
        thread_template.effective_policy = default_task_effective_policy;
        thread_template.pended_policy    = default_task_pended_policy;

        bzero(&thread_template.overrides, sizeof(thread_template.overrides));

        thread_template.iotier_override = THROTTLE_LEVEL_NONE;
        thread_template.thread_io_stats = NULL;
        thread_template.thread_callout_interrupt_wakeups = thread_template.thread_callout_platform_idle_wakeups = 0;

        thread_template.thread_timer_wakeups_bin_1 = thread_template.thread_timer_wakeups_bin_2 = 0;
        thread_template.callout_woken_from_icontext = thread_template.callout_woken_from_platform_idle = 0;

        thread_template.thread_tag = 0;

        thread_template.ith_voucher_name = MACH_PORT_NULL;
        thread_template.ith_voucher = IPC_VOUCHER_NULL;

        thread_template.work_interval_id = 0;

        init_thread = thread_template;
        machine_set_current_thread(&init_thread);
}

extern boolean_t allow_qos_policy_set;

void
thread_init(void)
{
        thread_zone = zinit(
                        sizeof(struct thread),
                        thread_max * sizeof(struct thread),
                        THREAD_CHUNK * sizeof(struct thread),
                        "threads");

        thread_qos_override_zone = zinit(
                sizeof(struct thread_qos_override),
                4 * thread_max * sizeof(struct thread_qos_override),
                PAGE_SIZE,
                "thread qos override");
        zone_change(thread_qos_override_zone, Z_EXPAND, TRUE);
        zone_change(thread_qos_override_zone, Z_COLLECT, TRUE);
        zone_change(thread_qos_override_zone, Z_CALLERACCT, FALSE);
        zone_change(thread_qos_override_zone, Z_NOENCRYPT, TRUE);

        lck_grp_attr_setdefault(&thread_lck_grp_attr);
        lck_grp_init(&thread_lck_grp, "thread", &thread_lck_grp_attr);
        lck_attr_setdefault(&thread_lck_attr);
        
        stack_init();

        /*
         *      Initialize any machine-dependent
         *      per-thread structures necessary.
         */
        machine_thread_init();

        if (!PE_parse_boot_argn("cpumon_ustackshots_trigger_pct", &cpumon_ustackshots_trigger_pct,
                sizeof (cpumon_ustackshots_trigger_pct))) {
                cpumon_ustackshots_trigger_pct = CPUMON_USTACKSHOTS_TRIGGER_DEFAULT_PCT;
        }

        PE_parse_boot_argn("-qos-policy-allow", &allow_qos_policy_set, sizeof(allow_qos_policy_set));   

        init_thread_ledgers();
}

static void
thread_terminate_continue(void)
{
        panic("thread_terminate_continue");
        /*NOTREACHED*/
}

/*
 *      thread_terminate_self:
 */
void
thread_terminate_self(void)
{
        thread_t                thread = current_thread();
        task_t                  task;
        spl_t                   s;
        int threadcnt;

        pal_thread_terminate_self(thread);

        DTRACE_PROC(lwp__exit);

        thread_mtx_lock(thread);

        ipc_thread_disable(thread);
        
        thread_mtx_unlock(thread);

        s = splsched();
        thread_lock(thread);

        assert_thread_sched_count(thread);

        /*
         *      Cancel priority depression, wait for concurrent expirations
         *      on other processors.
         */
        if (thread->sched_flags & TH_SFLAG_DEPRESSED_MASK) {
                thread->sched_flags &= ~TH_SFLAG_DEPRESSED_MASK;

                /* If our priority was low because of a depressed yield, restore it in case we block below */
                thread_recompute_sched_pri(thread, FALSE);

                if (timer_call_cancel(&thread->depress_timer))
                        thread->depress_timer_active--;
        }

        while (thread->depress_timer_active > 0) {
                thread_unlock(thread);
                splx(s);

                delay(1);

                s = splsched();
                thread_lock(thread);
        }

        thread_sched_call(thread, NULL);

        thread_unlock(thread);
        splx(s);


        thread_mtx_lock(thread);

        thread_policy_reset(thread);

        thread_mtx_unlock(thread);

        task = thread->task;
        uthread_cleanup(task, thread->uthread, task->bsd_info, thread->inspection == 1 ? TRUE : FALSE);
        threadcnt = hw_atomic_sub(&task->active_thread_count, 1);

        /*
         * If we are the last thread to terminate and the task is
         * associated with a BSD process, perform BSD process exit.
         */
        if (threadcnt == 0 && task->bsd_info != NULL) {
                proc_exit(task->bsd_info);
                /*
                 * if there is crash info in task
                 * then do the deliver action since this is
                 * last thread for this task.
                 */
                if (task->corpse_info) {
                        task_deliver_crash_notification(task);
                }
        }
        uthread_cred_free(thread->uthread);

        s = splsched();
        thread_lock(thread);

        /*
         *      Cancel wait timer, and wait for
         *      concurrent expirations.
         */
        if (thread->wait_timer_is_set) {
                thread->wait_timer_is_set = FALSE;

                if (timer_call_cancel(&thread->wait_timer))
                        thread->wait_timer_active--;
        }

        while (thread->wait_timer_active > 0) {
                thread_unlock(thread);
                splx(s);

                delay(1);

                s = splsched();
                thread_lock(thread);
        }

        /*
         *      If there is a reserved stack, release it.
         */
        if (thread->reserved_stack != 0) {
                stack_free_reserved(thread);
                thread->reserved_stack = 0;
        }

        /*
         *      Mark thread as terminating, and block.
         */
        thread->state |= TH_TERMINATE;
        thread_mark_wait_locked(thread, THREAD_UNINT);
        assert((thread->sched_flags & TH_SFLAG_PROMOTED) == 0);
        assert(thread->promotions == 0);
        assert(!(thread->sched_flags & TH_SFLAG_WAITQ_PROMOTED));
        assert(thread->rwlock_count == 0);
        thread_unlock(thread);
        /* splsched */

        thread_block((thread_continue_t)thread_terminate_continue);
        /*NOTREACHED*/
}

/* Drop a thread refcount that definitely isn't the last one. */
void
thread_deallocate_safe(thread_t thread)
{
        if (__improbable(hw_atomic_sub(&(thread)->ref_count, 1) == 0))
                panic("bad thread refcount!");
}

void
thread_deallocate(
        thread_t                        thread)
{
        task_t                          task;

        if (thread == THREAD_NULL)
                return;

        if (__probable(hw_atomic_sub(&(thread)->ref_count, 1) > 0))
                return;

        if(!(thread->state & TH_TERMINATE2))
                panic("thread_deallocate: thread not properly terminated\n");

        assert(thread->runq == PROCESSOR_NULL);

#if KPC
        kpc_thread_destroy(thread);
#endif

        ipc_thread_terminate(thread);

        proc_thread_qos_deallocate(thread);

        task = thread->task;

#ifdef MACH_BSD 
        {
                void *ut = thread->uthread;

                thread->uthread = NULL;
                uthread_zone_free(ut);
        }
#endif  /* MACH_BSD */   

        if (thread->t_ledger)
                ledger_dereference(thread->t_ledger);
        if (thread->t_threadledger)
                ledger_dereference(thread->t_threadledger);

        if (IPC_VOUCHER_NULL != thread->ith_voucher)
                ipc_voucher_release(thread->ith_voucher);

        if (thread->thread_io_stats)
                kfree(thread->thread_io_stats, sizeof(struct io_stat_info));

        if (thread->kernel_stack != 0)
                stack_free(thread);

        lck_mtx_destroy(&thread->mutex, &thread_lck_grp);
        machine_thread_destroy(thread);

        task_deallocate(task);

        zfree(thread_zone, thread);
}

/*
 *      thread_terminate_daemon:
 *
 *      Perform final clean up for terminating threads.
 */
static void
thread_terminate_daemon(void)
{
        thread_t        self, thread;
        task_t          task;

        self = current_thread();
        self->options |= TH_OPT_SYSTEM_CRITICAL;

        (void)splsched();
        simple_lock(&thread_terminate_lock);

        while ((thread = (thread_t)dequeue_head(&thread_terminate_queue)) != THREAD_NULL) {

                /* 
                 * if marked for crash reporting, skip reaping. 
                 * The corpse delivery thread will clear bit and enqueue 
                 * for reaping when done
                 */
                if (thread->inspection){
                        enqueue_tail(&crashed_threads_queue, (queue_entry_t)thread);
                        continue;
                }

                simple_unlock(&thread_terminate_lock);
                (void)spllo();

                assert(thread->SHARE_COUNT == 0);
                assert(thread->BG_COUNT == 0);

                task = thread->task;

                task_lock(task);
                task->total_user_time += timer_grab(&thread->user_timer);
                if (thread->precise_user_kernel_time) {
                        task->total_system_time += timer_grab(&thread->system_timer);
                } else {
                        task->total_user_time += timer_grab(&thread->system_timer);
                }

                task->c_switch += thread->c_switch;
                task->p_switch += thread->p_switch;
                task->ps_switch += thread->ps_switch;

                task->syscalls_unix += thread->syscalls_unix;
                task->syscalls_mach += thread->syscalls_mach;

                task->task_timer_wakeups_bin_1 += thread->thread_timer_wakeups_bin_1;
                task->task_timer_wakeups_bin_2 += thread->thread_timer_wakeups_bin_2;
                task->task_gpu_ns += ml_gpu_stat(thread);
                
                thread_update_qos_cpu_time(thread, FALSE);
                queue_remove(&task->threads, thread, thread_t, task_threads);
                task->thread_count--;

                /* 
                 * If the task is being halted, and there is only one thread
                 * left in the task after this one, then wakeup that thread.
                 */
                if (task->thread_count == 1 && task->halting)
                        thread_wakeup((event_t)&task->halting);

                task_unlock(task);

                lck_mtx_lock(&tasks_threads_lock);
                queue_remove(&threads, thread, thread_t, threads);
                threads_count--;
                lck_mtx_unlock(&tasks_threads_lock);

                thread_deallocate(thread);

                (void)splsched();
                simple_lock(&thread_terminate_lock);
        }

        assert_wait((event_t)&thread_terminate_queue, THREAD_UNINT);
        simple_unlock(&thread_terminate_lock);
        /* splsched */

        self->options &= ~TH_OPT_SYSTEM_CRITICAL;
        thread_block((thread_continue_t)thread_terminate_daemon);
        /*NOTREACHED*/
}

/*
 *      thread_terminate_enqueue:
 *
 *      Enqueue a terminating thread for final disposition.
 *
 *      Called at splsched.
 */
void
thread_terminate_enqueue(
        thread_t                thread)
{
        KERNEL_DEBUG_CONSTANT(TRACE_DATA_THREAD_TERMINATE | DBG_FUNC_NONE, thread->thread_id, 0, 0, 0, 0);

        simple_lock(&thread_terminate_lock);
        enqueue_tail(&thread_terminate_queue, (queue_entry_t)thread);
        simple_unlock(&thread_terminate_lock);

        thread_wakeup((event_t)&thread_terminate_queue);
}

/*
 * thread_terminate_crashed_threads:
 * walk the list of crashed therds and put back set of threads
 * who are no longer being inspected.
 */
void
thread_terminate_crashed_threads()
{
        thread_t th_iter, th_remove;
        boolean_t should_wake_terminate_queue = FALSE;

        simple_lock(&thread_terminate_lock);
        /*
         * loop through the crashed threads queue
         * to put any threads that are not being inspected anymore
         */
        th_iter = (thread_t)queue_first(&crashed_threads_queue);
        while (!queue_end(&crashed_threads_queue, (queue_entry_t)th_iter)) {
                th_remove = th_iter;
                th_iter = (thread_t)queue_next(&th_iter->links);

                /* make sure current_thread is never in crashed queue */
                assert(th_remove != current_thread());
                if (th_remove->inspection != TRUE){
                        remque((queue_entry_t)th_remove);
                        enqueue_tail(&thread_terminate_queue, (queue_entry_t)th_remove);
                        should_wake_terminate_queue = TRUE;
                }
        }

        simple_unlock(&thread_terminate_lock);
        if (should_wake_terminate_queue == TRUE) {
                thread_wakeup((event_t)&thread_terminate_queue);
        }
}

/*
 *      thread_stack_daemon:
 *
 *      Perform stack allocation as required due to
 *      invoke failures.
 */
static void
thread_stack_daemon(void)
{
        thread_t                thread;
        spl_t                   s;

        s = splsched();
        simple_lock(&thread_stack_lock);

        while ((thread = (thread_t)dequeue_head(&thread_stack_queue)) != THREAD_NULL) {
                simple_unlock(&thread_stack_lock);
                splx(s);

                /* allocate stack with interrupts enabled so that we can call into VM */
                stack_alloc(thread);

                KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED,MACH_STACK_WAIT) | DBG_FUNC_END, thread_tid(thread), 0, 0, 0, 0);
                
                s = splsched();
                thread_lock(thread);
                thread_setrun(thread, SCHED_PREEMPT | SCHED_TAILQ);
                thread_unlock(thread);

                simple_lock(&thread_stack_lock);
        }

        assert_wait((event_t)&thread_stack_queue, THREAD_UNINT);
        simple_unlock(&thread_stack_lock);
        splx(s);

        thread_block((thread_continue_t)thread_stack_daemon);
        /*NOTREACHED*/
}

/*
 *      thread_stack_enqueue:
 *
 *      Enqueue a thread for stack allocation.
 *
 *      Called at splsched.
 */
void
thread_stack_enqueue(
        thread_t                thread)
{
        KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED,MACH_STACK_WAIT) | DBG_FUNC_START, thread_tid(thread), 0, 0, 0, 0);

        simple_lock(&thread_stack_lock);
        enqueue_tail(&thread_stack_queue, (queue_entry_t)thread);
        simple_unlock(&thread_stack_lock);

        thread_wakeup((event_t)&thread_stack_queue);
}

void
thread_daemon_init(void)
{
        kern_return_t   result;
        thread_t        thread = NULL;

        simple_lock_init(&thread_terminate_lock, 0);
        queue_init(&thread_terminate_queue);
        queue_init(&crashed_threads_queue);

        result = kernel_thread_start_priority((thread_continue_t)thread_terminate_daemon, NULL, MINPRI_KERNEL, &thread);
        if (result != KERN_SUCCESS)
                panic("thread_daemon_init: thread_terminate_daemon");

        thread_deallocate(thread);

        simple_lock_init(&thread_stack_lock, 0);
        queue_init(&thread_stack_queue);

        result = kernel_thread_start_priority((thread_continue_t)thread_stack_daemon, NULL, BASEPRI_PREEMPT, &thread);
        if (result != KERN_SUCCESS)
                panic("thread_daemon_init: thread_stack_daemon");

        thread_deallocate(thread);
}

#define TH_OPTION_NONE          0x00
#define TH_OPTION_NOCRED        0x01
#define TH_OPTION_NOSUSP        0x02
/*
 * Create a new thread.
 * Doesn't start the thread running.
 *
 * Task and tasks_threads_lock are returned locked on success.
 */
static kern_return_t
thread_create_internal(
        task_t                                  parent_task,
        integer_t                               priority,
        thread_continue_t               continuation,
        int                                             options,
        thread_t                                *out_thread)
{
        thread_t                                new_thread;
        static thread_t                 first_thread;

        /*
         *      Allocate a thread and initialize static fields
         */
        if (first_thread == THREAD_NULL)
                new_thread = first_thread = current_thread();
        else
                new_thread = (thread_t)zalloc(thread_zone);
        if (new_thread == THREAD_NULL)
                return (KERN_RESOURCE_SHORTAGE);

        if (new_thread != first_thread)
                *new_thread = thread_template;

#ifdef MACH_BSD
        new_thread->uthread = uthread_alloc(parent_task, new_thread, (options & TH_OPTION_NOCRED) != 0);
        if (new_thread->uthread == NULL) {
                zfree(thread_zone, new_thread);
                return (KERN_RESOURCE_SHORTAGE);
        }
#endif  /* MACH_BSD */

        if (machine_thread_create(new_thread, parent_task) != KERN_SUCCESS) {
#ifdef MACH_BSD
                void *ut = new_thread->uthread;

                new_thread->uthread = NULL;
                /* cred free may not be necessary */
                uthread_cleanup(parent_task, ut, parent_task->bsd_info, FALSE);
                uthread_cred_free(ut);
                uthread_zone_free(ut);
#endif  /* MACH_BSD */

                zfree(thread_zone, new_thread);
                return (KERN_FAILURE);
        }

        new_thread->task = parent_task;

        thread_lock_init(new_thread);
        wake_lock_init(new_thread);

        lck_mtx_init(&new_thread->mutex, &thread_lck_grp, &thread_lck_attr);

        ipc_thread_init(new_thread);

        new_thread->continuation = continuation;

        /* Allocate I/O Statistics structure */
        new_thread->thread_io_stats = (io_stat_info_t)kalloc(sizeof(struct io_stat_info));
        assert(new_thread->thread_io_stats != NULL);
        bzero(new_thread->thread_io_stats, sizeof(struct io_stat_info));

#if CONFIG_IOSCHED
        /* Clear out the I/O Scheduling info for AppleFSCompression */
        new_thread->decmp_upl = NULL;
#endif /* CONFIG_IOSCHED */ 

        lck_mtx_lock(&tasks_threads_lock);
        task_lock(parent_task);

        if (    !parent_task->active || parent_task->halting ||
                        ((options & TH_OPTION_NOSUSP) != 0 &&
                                parent_task->suspend_count > 0) ||
                        (parent_task->thread_count >= task_threadmax &&
                                parent_task != kernel_task)             ) {
                task_unlock(parent_task);
                lck_mtx_unlock(&tasks_threads_lock);

#ifdef MACH_BSD
                {
                        void *ut = new_thread->uthread;

                        new_thread->uthread = NULL;
                        uthread_cleanup(parent_task, ut, parent_task->bsd_info, FALSE);
                        /* cred free may not be necessary */
                        uthread_cred_free(ut);
                        uthread_zone_free(ut);
                }
#endif  /* MACH_BSD */
                ipc_thread_disable(new_thread);
                ipc_thread_terminate(new_thread);
                kfree(new_thread->thread_io_stats, sizeof(struct io_stat_info));
                lck_mtx_destroy(&new_thread->mutex, &thread_lck_grp);
                machine_thread_destroy(new_thread);
                zfree(thread_zone, new_thread);
                return (KERN_FAILURE);
        }

        /* New threads inherit any default state on the task */
        machine_thread_inherit_taskwide(new_thread, parent_task);

        task_reference_internal(parent_task);

        if (new_thread->task->rusage_cpu_flags & TASK_RUSECPU_FLAGS_PERTHR_LIMIT) {
                /*
                 * This task has a per-thread CPU limit; make sure this new thread
                 * gets its limit set too, before it gets out of the kernel.
                 */
                set_astledger(new_thread);
        }

        /* Instantiate a thread ledger. Do not fail thread creation if ledger creation fails. */
        if ((new_thread->t_threadledger = ledger_instantiate(thread_ledger_template,
                                LEDGER_CREATE_INACTIVE_ENTRIES)) != LEDGER_NULL) {

                ledger_entry_setactive(new_thread->t_threadledger, thread_ledgers.cpu_time);
        }

        new_thread->cpu_time_last_qos = 0;
#ifdef CONFIG_BANK
        new_thread->t_bankledger = LEDGER_NULL;
        new_thread->t_deduct_bank_ledger_time = 0;
#endif

        new_thread->t_ledger = new_thread->task->ledger;
        if (new_thread->t_ledger)
                ledger_reference(new_thread->t_ledger);

#if defined(CONFIG_SCHED_MULTIQ)
        /* Cache the task's sched_group */
        new_thread->sched_group = parent_task->sched_group;
#endif /* defined(CONFIG_SCHED_MULTIQ) */

        /* Cache the task's map */
        new_thread->map = parent_task->map;

        timer_call_setup(&new_thread->wait_timer, thread_timer_expire, new_thread);
        timer_call_setup(&new_thread->depress_timer, thread_depress_expire, new_thread);

#if KPC
        kpc_thread_create(new_thread);
#endif
        
        /* Only need to update policies pushed from task to thread */
        new_thread->requested_policy.bg_iotier  = parent_task->effective_policy.bg_iotier;
        new_thread->requested_policy.terminated = parent_task->effective_policy.terminated;

        /* Set the thread's scheduling parameters */
#if defined(CONFIG_SCHED_TIMESHARE_CORE)
        new_thread->sched_stamp = sched_tick;
        new_thread->pri_shift = sched_pri_shift;
#endif /* defined(CONFIG_SCHED_TIMESHARE_CORE) */

        new_thread->sched_mode = SCHED(initial_thread_sched_mode)(parent_task);
        new_thread->sched_flags = 0;
        new_thread->max_priority = parent_task->max_priority;
        new_thread->task_priority = parent_task->priority;

        int new_priority = (priority < 0) ? parent_task->priority: priority;
        new_priority = (priority < 0)? parent_task->priority: priority;
        if (new_priority > new_thread->max_priority)
                new_priority = new_thread->max_priority;

        new_thread->importance = new_priority - new_thread->task_priority;
        new_thread->saved_importance = new_thread->importance;

        if (parent_task->max_priority <= MAXPRI_THROTTLE) {
                sched_set_thread_throttled(new_thread, TRUE);
        }

        sched_set_thread_base_priority(new_thread, new_priority);

        thread_policy_create(new_thread);

        /* Chain the thread onto the task's list */
        queue_enter(&parent_task->threads, new_thread, thread_t, task_threads);
        parent_task->thread_count++;

        /* So terminating threads don't need to take the task lock to decrement */
        hw_atomic_add(&parent_task->active_thread_count, 1);

        /* Protected by the tasks_threads_lock */
        new_thread->thread_id = ++thread_unique_id;

        queue_enter(&threads, new_thread, thread_t, threads);
        threads_count++;

        new_thread->active = TRUE;
        new_thread->inspection = FALSE;
        *out_thread = new_thread;

        {
                long    dbg_arg1, dbg_arg2, dbg_arg3, dbg_arg4;

                kdbg_trace_data(parent_task->bsd_info, &dbg_arg2);

                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
                        TRACEDBG_CODE(DBG_TRACE_DATA, 1) | DBG_FUNC_NONE,
                        (vm_address_t)(uintptr_t)thread_tid(new_thread), dbg_arg2, 0, 0, 0);

                kdbg_trace_string(parent_task->bsd_info,
                                                        &dbg_arg1, &dbg_arg2, &dbg_arg3, &dbg_arg4);

                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
                        TRACEDBG_CODE(DBG_TRACE_STRING, 1) | DBG_FUNC_NONE,
                        dbg_arg1, dbg_arg2, dbg_arg3, dbg_arg4, 0);
        }

        DTRACE_PROC1(lwp__create, thread_t, *out_thread);

        return (KERN_SUCCESS);
}

static kern_return_t
thread_create_internal2(
        task_t                          task,
        thread_t                        *new_thread,
        boolean_t                       from_user,
        thread_continue_t               continuation)
{
        kern_return_t           result;
        thread_t                        thread;

        if (task == TASK_NULL || task == kernel_task)
                return (KERN_INVALID_ARGUMENT);

        result = thread_create_internal(task, -1, continuation, TH_OPTION_NONE, &thread);
        if (result != KERN_SUCCESS)
                return (result);

        thread->user_stop_count = 1;
        thread_hold(thread);
        if (task->suspend_count > 0)
                thread_hold(thread);

        if (from_user)
                extmod_statistics_incr_thread_create(task);

        task_unlock(task);
        lck_mtx_unlock(&tasks_threads_lock);
        
        *new_thread = thread;

        return (KERN_SUCCESS);
}

/* No prototype, since task_server.h has the _from_user version if KERNEL_SERVER */
kern_return_t
thread_create(
        task_t                          task,
        thread_t                        *new_thread);

kern_return_t
thread_create(
        task_t                          task,
        thread_t                        *new_thread)
{
        return thread_create_internal2(task, new_thread, FALSE, (thread_continue_t)thread_bootstrap_return);
}

kern_return_t
thread_create_from_user(
        task_t                          task,
        thread_t                        *new_thread)
{
        return thread_create_internal2(task, new_thread, TRUE, (thread_continue_t)thread_bootstrap_return);
}

kern_return_t
thread_create_with_continuation(
        task_t                          task,
        thread_t                        *new_thread,
        thread_continue_t               continuation)
{
        return thread_create_internal2(task, new_thread, FALSE, continuation);
}

static kern_return_t
thread_create_running_internal2(
        register task_t         task,
        int                     flavor,
        thread_state_t          new_state,
        mach_msg_type_number_t  new_state_count,
        thread_t                                *new_thread,
        boolean_t                               from_user)
{
        register kern_return_t  result;
        thread_t                                thread;

        if (task == TASK_NULL || task == kernel_task)
                return (KERN_INVALID_ARGUMENT);

        result = thread_create_internal(task, -1, (thread_continue_t)thread_bootstrap_return, TH_OPTION_NONE, &thread);
        if (result != KERN_SUCCESS)
                return (result);

        result = machine_thread_set_state(thread, flavor, new_state, new_state_count);
        if (result != KERN_SUCCESS) {
                task_unlock(task);
                lck_mtx_unlock(&tasks_threads_lock);

                thread_terminate(thread);
                thread_deallocate(thread);
                return (result);
        }

        thread_mtx_lock(thread);
        thread_start_internal(thread);
        thread_mtx_unlock(thread);

        if (from_user)
                extmod_statistics_incr_thread_create(task);

        task_unlock(task);
        lck_mtx_unlock(&tasks_threads_lock);

        *new_thread = thread;

        return (result);
}

/* Prototype, see justification above */
kern_return_t
thread_create_running(
        register task_t         task,
        int                     flavor,
        thread_state_t          new_state,
        mach_msg_type_number_t  new_state_count,
        thread_t                                *new_thread);

kern_return_t
thread_create_running(
        register task_t         task,
        int                     flavor,
        thread_state_t          new_state,
        mach_msg_type_number_t  new_state_count,
        thread_t                                *new_thread)
{
        return thread_create_running_internal2(
                task, flavor, new_state, new_state_count,
                new_thread, FALSE);
}

kern_return_t
thread_create_running_from_user(
        register task_t         task,
        int                     flavor,
        thread_state_t          new_state,
        mach_msg_type_number_t  new_state_count,
        thread_t                                *new_thread)
{
        return thread_create_running_internal2(
                task, flavor, new_state, new_state_count,
                new_thread, TRUE);
}

kern_return_t
thread_create_workq(
        task_t                          task,
        thread_continue_t               thread_return,
        thread_t                        *new_thread)
{
        kern_return_t           result;
        thread_t                        thread;

        if (task == TASK_NULL || task == kernel_task)
                return (KERN_INVALID_ARGUMENT);

        result = thread_create_internal(task, -1, thread_return, TH_OPTION_NOCRED | TH_OPTION_NOSUSP, &thread);
        if (result != KERN_SUCCESS)
                return (result);

        thread->user_stop_count = 1;
        thread_hold(thread);
        if (task->suspend_count > 0)
                thread_hold(thread);

        task_unlock(task);
        lck_mtx_unlock(&tasks_threads_lock);
        
        *new_thread = thread;

        return (KERN_SUCCESS);
}

/*
 *      kernel_thread_create:
 *
 *      Create a thread in the kernel task
 *      to execute in kernel context.
 */
kern_return_t
kernel_thread_create(
        thread_continue_t       continuation,
        void                            *parameter,
        integer_t                       priority,
        thread_t                        *new_thread)
{
        kern_return_t           result;
        thread_t                        thread;
        task_t                          task = kernel_task;

        result = thread_create_internal(task, priority, continuation, TH_OPTION_NONE, &thread);
        if (result != KERN_SUCCESS)
                return (result);

        task_unlock(task);
        lck_mtx_unlock(&tasks_threads_lock);

        stack_alloc(thread);
        assert(thread->kernel_stack != 0);
        thread->reserved_stack = thread->kernel_stack;

        thread->parameter = parameter;

if(debug_task & 1)
        kprintf("kernel_thread_create: thread = %p continuation = %p\n", thread, continuation);
        *new_thread = thread;

        return (result);
}

kern_return_t
kernel_thread_start_priority(
        thread_continue_t       continuation,
        void                            *parameter,
        integer_t                       priority,
        thread_t                        *new_thread)
{
        kern_return_t   result;
        thread_t                thread;

        result = kernel_thread_create(continuation, parameter, priority, &thread);
        if (result != KERN_SUCCESS)
                return (result);

        *new_thread = thread;   

        thread_mtx_lock(thread);
        thread_start_internal(thread);
        thread_mtx_unlock(thread);

        return (result);
}

kern_return_t
kernel_thread_start(
        thread_continue_t       continuation,
        void                            *parameter,
        thread_t                        *new_thread)
{
        return kernel_thread_start_priority(continuation, parameter, -1, new_thread);
}

/* Separated into helper function so it can be used by THREAD_BASIC_INFO and THREAD_EXTENDED_INFO */
/* it is assumed that the thread is locked by the caller */
static void
retrieve_thread_basic_info(thread_t thread, thread_basic_info_t basic_info)
{
        int     state, flags;

        /* fill in info */

        thread_read_times(thread, &basic_info->user_time,
                                                                &basic_info->system_time);

        /*
         *      Update lazy-evaluated scheduler info because someone wants it.
         */
        if (SCHED(can_update_priority)(thread))
                SCHED(update_priority)(thread);

        basic_info->sleep_time = 0;

        /*
         *      To calculate cpu_usage, first correct for timer rate,
         *      then for 5/8 ageing.  The correction factor [3/5] is
         *      (1/(5/8) - 1).
         */
        basic_info->cpu_usage = 0;
#if defined(CONFIG_SCHED_TIMESHARE_CORE)
        if (sched_tick_interval) {
                basic_info->cpu_usage = (integer_t)(((uint64_t)thread->cpu_usage
                                                                        * TH_USAGE_SCALE) /     sched_tick_interval);
                basic_info->cpu_usage = (basic_info->cpu_usage * 3) / 5;
        }
#endif

        if (basic_info->cpu_usage > TH_USAGE_SCALE)
                basic_info->cpu_usage = TH_USAGE_SCALE;

        basic_info->policy = ((thread->sched_mode == TH_MODE_TIMESHARE)?
                                                                                        POLICY_TIMESHARE: POLICY_RR);

        flags = 0;
        if (thread->options & TH_OPT_IDLE_THREAD)
                flags |= TH_FLAGS_IDLE;

        if (thread->options & TH_OPT_GLOBAL_FORCED_IDLE) {
                flags |= TH_FLAGS_GLOBAL_FORCED_IDLE;
        }

        if (!thread->kernel_stack)
                flags |= TH_FLAGS_SWAPPED;

        state = 0;
        if (thread->state & TH_TERMINATE)
                state = TH_STATE_HALTED;
        else
        if (thread->state & TH_RUN)
                state = TH_STATE_RUNNING;
        else
        if (thread->state & TH_UNINT)
                state = TH_STATE_UNINTERRUPTIBLE;
        else
        if (thread->state & TH_SUSP)
                state = TH_STATE_STOPPED;
        else
        if (thread->state & TH_WAIT)
                state = TH_STATE_WAITING;

        basic_info->run_state = state;
        basic_info->flags = flags;

        basic_info->suspend_count = thread->user_stop_count;

        return;
}

kern_return_t
thread_info_internal(
        register thread_t               thread,
        thread_flavor_t                 flavor,
        thread_info_t                   thread_info_out,        /* ptr to OUT array */
        mach_msg_type_number_t  *thread_info_count)     /*IN/OUT*/
{
        spl_t   s;

        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        if (flavor == THREAD_BASIC_INFO) {

                if (*thread_info_count < THREAD_BASIC_INFO_COUNT)
                        return (KERN_INVALID_ARGUMENT);

                s = splsched();
                thread_lock(thread);

                retrieve_thread_basic_info(thread, (thread_basic_info_t) thread_info_out);

                thread_unlock(thread);
                splx(s);

                *thread_info_count = THREAD_BASIC_INFO_COUNT;

                return (KERN_SUCCESS);
        }
        else
        if (flavor == THREAD_IDENTIFIER_INFO) {
                register thread_identifier_info_t       identifier_info;

                if (*thread_info_count < THREAD_IDENTIFIER_INFO_COUNT)
                        return (KERN_INVALID_ARGUMENT);

                identifier_info = (thread_identifier_info_t) thread_info_out;

                s = splsched();
                thread_lock(thread);

                identifier_info->thread_id = thread->thread_id;
                identifier_info->thread_handle = thread->machine.cthread_self;
                identifier_info->dispatch_qaddr = thread_dispatchqaddr(thread);

                thread_unlock(thread);
                splx(s);
                return KERN_SUCCESS;
        }
        else
        if (flavor == THREAD_SCHED_TIMESHARE_INFO) {
                policy_timeshare_info_t         ts_info;

                if (*thread_info_count < POLICY_TIMESHARE_INFO_COUNT)
                        return (KERN_INVALID_ARGUMENT);

                ts_info = (policy_timeshare_info_t)thread_info_out;

                s = splsched();
                thread_lock(thread);

                if (thread->sched_mode != TH_MODE_TIMESHARE) {
                        thread_unlock(thread);
                        splx(s);
                        return (KERN_INVALID_POLICY);
                }

                ts_info->depressed = (thread->sched_flags & TH_SFLAG_DEPRESSED_MASK) != 0;
                if (ts_info->depressed) {
                        ts_info->base_priority = DEPRESSPRI;
                        ts_info->depress_priority = thread->base_pri;
                }
                else {
                        ts_info->base_priority = thread->base_pri;
                        ts_info->depress_priority = -1;
                }

                ts_info->cur_priority = thread->sched_pri;
                ts_info->max_priority = thread->max_priority;

                thread_unlock(thread);
                splx(s);

                *thread_info_count = POLICY_TIMESHARE_INFO_COUNT;

                return (KERN_SUCCESS);
        }
        else
        if (flavor == THREAD_SCHED_FIFO_INFO) {
                if (*thread_info_count < POLICY_FIFO_INFO_COUNT)
                        return (KERN_INVALID_ARGUMENT);

                return (KERN_INVALID_POLICY);
        }
        else
        if (flavor == THREAD_SCHED_RR_INFO) {
                policy_rr_info_t                        rr_info;
                uint32_t quantum_time;
                uint64_t quantum_ns;

                if (*thread_info_count < POLICY_RR_INFO_COUNT)
                        return (KERN_INVALID_ARGUMENT);

                rr_info = (policy_rr_info_t) thread_info_out;

                s = splsched();
                thread_lock(thread);

                if (thread->sched_mode == TH_MODE_TIMESHARE) {
                        thread_unlock(thread);
                        splx(s);

                        return (KERN_INVALID_POLICY);
            }

                rr_info->depressed = (thread->sched_flags & TH_SFLAG_DEPRESSED_MASK) != 0;
                if (rr_info->depressed) {
                        rr_info->base_priority = DEPRESSPRI;
                        rr_info->depress_priority = thread->base_pri;
                }
                else {
                        rr_info->base_priority = thread->base_pri;
                        rr_info->depress_priority = -1;
                }

                quantum_time = SCHED(initial_quantum_size)(THREAD_NULL);
                absolutetime_to_nanoseconds(quantum_time, &quantum_ns);

                rr_info->max_priority = thread->max_priority;
                rr_info->quantum = (uint32_t)(quantum_ns / 1000 / 1000);

                thread_unlock(thread);
                splx(s);

                *thread_info_count = POLICY_RR_INFO_COUNT;

                return (KERN_SUCCESS);
        }
        else
        if (flavor == THREAD_EXTENDED_INFO) {
                thread_basic_info_data_t        basic_info;
                thread_extended_info_t          extended_info = (thread_extended_info_t) thread_info_out;

                if (*thread_info_count < THREAD_EXTENDED_INFO_COUNT) {
                        return (KERN_INVALID_ARGUMENT);
                }

                s = splsched();
                thread_lock(thread);

                /* NOTE: This mimics fill_taskthreadinfo(), which is the function used by proc_pidinfo() for
                 * the PROC_PIDTHREADINFO flavor (which can't be used on corpses)
                 */
                retrieve_thread_basic_info(thread, &basic_info);
                extended_info->pth_user_time = ((basic_info.user_time.seconds * (integer_t)NSEC_PER_SEC) + (basic_info.user_time.microseconds * (integer_t)NSEC_PER_USEC));
                extended_info->pth_system_time = ((basic_info.system_time.seconds * (integer_t)NSEC_PER_SEC) + (basic_info.system_time.microseconds * (integer_t)NSEC_PER_USEC));

                extended_info->pth_cpu_usage = basic_info.cpu_usage;
                extended_info->pth_policy = basic_info.policy;
                extended_info->pth_run_state = basic_info.run_state;
                extended_info->pth_flags = basic_info.flags;
                extended_info->pth_sleep_time = basic_info.sleep_time;
                extended_info->pth_curpri = thread->sched_pri;
                extended_info->pth_priority = thread->base_pri;
                extended_info->pth_maxpriority = thread->max_priority;

                bsd_getthreadname(thread->uthread,extended_info->pth_name);

                thread_unlock(thread);
                splx(s);

                *thread_info_count = THREAD_EXTENDED_INFO_COUNT;

                return (KERN_SUCCESS);
        }
        else
        if (flavor == THREAD_DEBUG_INFO_INTERNAL) {
#if DEVELOPMENT || DEBUG
                thread_debug_info_internal_t dbg_info;
                if (*thread_info_count < THREAD_DEBUG_INFO_INTERNAL_COUNT)
                        return (KERN_NOT_SUPPORTED);

                if (thread_info_out == NULL)
                        return (KERN_INVALID_ARGUMENT);

                dbg_info = (thread_debug_info_internal_t) thread_info_out;
                dbg_info->page_creation_count = thread->t_page_creation_count;

                *thread_info_count = THREAD_DEBUG_INFO_INTERNAL_COUNT;
                return (KERN_SUCCESS);
#endif /* DEVELOPMENT || DEBUG */
                return (KERN_NOT_SUPPORTED);
        }

        return (KERN_INVALID_ARGUMENT);
}

void
thread_read_times(
        thread_t                thread,
        time_value_t    *user_time,
        time_value_t    *system_time)
{
        clock_sec_t             secs;
        clock_usec_t    usecs;
        uint64_t                tval_user, tval_system;

        tval_user = timer_grab(&thread->user_timer);
        tval_system = timer_grab(&thread->system_timer);

        if (thread->precise_user_kernel_time) {
                absolutetime_to_microtime(tval_user, &secs, &usecs);
                user_time->seconds = (typeof(user_time->seconds))secs;
                user_time->microseconds = usecs;
                
                absolutetime_to_microtime(tval_system, &secs, &usecs);
                system_time->seconds = (typeof(system_time->seconds))secs;
                system_time->microseconds = usecs;
        } else {
                /* system_timer may represent either sys or user */
                tval_user += tval_system;
                absolutetime_to_microtime(tval_user, &secs, &usecs);
                user_time->seconds = (typeof(user_time->seconds))secs;
                user_time->microseconds = usecs;

                system_time->seconds = 0;
                system_time->microseconds = 0;
        }
}

uint64_t thread_get_runtime_self(void)
{
        boolean_t interrupt_state;
        uint64_t runtime;
        thread_t thread = NULL;
        processor_t processor = NULL;

        thread = current_thread();

        /* Not interrupt safe, as the scheduler may otherwise update timer values underneath us */
        interrupt_state = ml_set_interrupts_enabled(FALSE);
        processor = current_processor();
        timer_switch(PROCESSOR_DATA(processor, thread_timer), mach_absolute_time(), PROCESSOR_DATA(processor, thread_timer));
        runtime = (timer_grab(&thread->user_timer) + timer_grab(&thread->system_timer));
        ml_set_interrupts_enabled(interrupt_state);

        return runtime;
}

kern_return_t
thread_assign(
        __unused thread_t                       thread,
        __unused processor_set_t        new_pset)
{
        return (KERN_FAILURE);
}

/*
 *      thread_assign_default:
 *
 *      Special version of thread_assign for assigning threads to default
 *      processor set.
 */
kern_return_t
thread_assign_default(
        thread_t                thread)
{
        return (thread_assign(thread, &pset0));
}

/*
 *      thread_get_assignment
 *
 *      Return current assignment for this thread.
 */         
kern_return_t
thread_get_assignment(
        thread_t                thread,
        processor_set_t *pset)
{
        if (thread == NULL)
                return (KERN_INVALID_ARGUMENT);

        *pset = &pset0;

        return (KERN_SUCCESS);
}

/*
 *      thread_wire_internal:
 *
 *      Specify that the target thread must always be able
 *      to run and to allocate memory.
 */
kern_return_t
thread_wire_internal(
        host_priv_t             host_priv,
        thread_t                thread,
        boolean_t               wired,
        boolean_t               *prev_state)
{
        if (host_priv == NULL || thread != current_thread())
                return (KERN_INVALID_ARGUMENT);

        assert(host_priv == &realhost);

        if (prev_state)
            *prev_state = (thread->options & TH_OPT_VMPRIV) != 0;
        
        if (wired) {
            if (!(thread->options & TH_OPT_VMPRIV)) 
                    vm_page_free_reserve(1);    /* XXX */
            thread->options |= TH_OPT_VMPRIV;
        }
        else {
            if (thread->options & TH_OPT_VMPRIV) 
                    vm_page_free_reserve(-1);   /* XXX */
            thread->options &= ~TH_OPT_VMPRIV;
        }

        return (KERN_SUCCESS);
}


/*
 *      thread_wire:
 *
 *      User-api wrapper for thread_wire_internal()
 */
kern_return_t
thread_wire(
        host_priv_t     host_priv,
        thread_t        thread,
        boolean_t       wired)
{
    return (thread_wire_internal(host_priv, thread, wired, NULL));
}


boolean_t
set_vm_privilege(boolean_t privileged)
{
        boolean_t       was_vmpriv;

        if (current_thread()->options & TH_OPT_VMPRIV)
                was_vmpriv = TRUE;
        else
                was_vmpriv = FALSE;

        if (privileged != FALSE)
                current_thread()->options |= TH_OPT_VMPRIV;
        else
                current_thread()->options &= ~TH_OPT_VMPRIV;

        return (was_vmpriv);
}


/*
 * XXX assuming current thread only, for now...
 */
void
thread_guard_violation(thread_t thread, unsigned type)
{
        assert(thread == current_thread());

        spl_t s = splsched();
        /*
         * Use the saved state area of the thread structure
         * to store all info required to handle the AST when
         * returning to userspace
         */
        thread->guard_exc_info.type = type;
        thread_ast_set(thread, AST_GUARD);
        ast_propagate(thread->ast);

        splx(s);
}

/*
 *      guard_ast:
 *
 *      Handle AST_GUARD for a thread. This routine looks at the
 *      state saved in the thread structure to determine the cause
 *      of this exception. Based on this value, it invokes the 
 *      appropriate routine which determines other exception related
 *      info and raises the exception.
 */
void
guard_ast(thread_t thread)
{
        if (thread->guard_exc_info.type == GUARD_TYPE_MACH_PORT)
                mach_port_guard_ast(thread);
        else
                fd_guard_ast(thread);
}

static void
thread_cputime_callback(int warning, __unused const void *arg0, __unused const void *arg1)
{
        if (warning == LEDGER_WARNING_ROSE_ABOVE) {
#if CONFIG_TELEMETRY            
                /*
                 * This thread is in danger of violating the CPU usage monitor. Enable telemetry
                 * on the entire task so there are micro-stackshots available if and when
                 * EXC_RESOURCE is triggered. We could have chosen to enable micro-stackshots
                 * for this thread only; but now that this task is suspect, knowing what all of
                 * its threads are up to will be useful.
                 */
                telemetry_task_ctl(current_task(), TF_CPUMON_WARNING, 1);
#endif
                return;
        }

#if CONFIG_TELEMETRY
        /*
         * If the balance has dipped below the warning level (LEDGER_WARNING_DIPPED_BELOW) or
         * exceeded the limit, turn telemetry off for the task.
         */
        telemetry_task_ctl(current_task(), TF_CPUMON_WARNING, 0);
#endif

        if (warning == 0) {
                THIS_THREAD_IS_CONSUMING_TOO_MUCH_CPU__SENDING_EXC_RESOURCE();
        }
}

void __attribute__((noinline))
THIS_THREAD_IS_CONSUMING_TOO_MUCH_CPU__SENDING_EXC_RESOURCE(void)
{
        int          pid                = 0;
        task_t           task                           = current_task();
        thread_t     thread             = current_thread();
        uint64_t     tid                = thread->thread_id;
        const char       *procname          = "unknown";
        time_value_t thread_total_time  = {0, 0};
        time_value_t thread_system_time;
        time_value_t thread_user_time;
        int          action;
        uint8_t      percentage;
        uint32_t     limit_percent;
        uint32_t     usage_percent;
        uint32_t     interval_sec;
        uint64_t     interval_ns;
        uint64_t     balance_ns;
        boolean_t        fatal = FALSE;

        mach_exception_data_type_t      code[EXCEPTION_CODE_MAX];
        struct ledger_entry_info        lei;

        assert(thread->t_threadledger != LEDGER_NULL);

        /*
         * Now that a thread has tripped the monitor, disable it for the entire task.
         */
        task_lock(task);
        if ((task->rusage_cpu_flags & TASK_RUSECPU_FLAGS_PERTHR_LIMIT) == 0) {
                /*
                 * The CPU usage monitor has been disabled on our task, so some other
                 * thread must have gotten here first. We only send one exception per
                 * task lifetime, so there's nothing left for us to do here.
                 */
                task_unlock(task);
                return;
        }
        if (task->rusage_cpu_flags & TASK_RUSECPU_FLAGS_FATAL_CPUMON) {
                fatal = TRUE;
        }
        task_disable_cpumon(task);
        task_unlock(task);

#ifdef MACH_BSD
        pid = proc_selfpid();
        if (task->bsd_info != NULL)
                procname = proc_name_address(task->bsd_info);
#endif

        thread_get_cpulimit(&action, &percentage, &interval_ns);

        interval_sec = (uint32_t)(interval_ns / NSEC_PER_SEC);

        thread_read_times(thread, &thread_user_time, &thread_system_time);
        time_value_add(&thread_total_time, &thread_user_time);
        time_value_add(&thread_total_time, &thread_system_time);

        ledger_get_entry_info(thread->t_threadledger, thread_ledgers.cpu_time, &lei);

        absolutetime_to_nanoseconds(lei.lei_balance, &balance_ns);
        usage_percent = (uint32_t) ((balance_ns * 100ULL) / lei.lei_last_refill);

        /* Show refill period in the same units as balance, limit, etc */
        nanoseconds_to_absolutetime(lei.lei_refill_period, &lei.lei_refill_period);

        limit_percent = (uint32_t) ((lei.lei_limit * 100ULL) / lei.lei_refill_period);

        /*  TODO: show task total runtime as well? see TASK_ABSOLUTETIME_INFO */

        if (disable_exc_resource) {
                printf("process %s[%d] thread %llu caught burning CPU!; EXC_RESOURCE "
                        "supressed by a boot-arg\n", procname, pid, tid);
                return;
        }

        if (audio_active) {
                printf("process %s[%d] thread %llu caught burning CPU!; EXC_RESOURCE "
                       "supressed due to audio playback\n", procname, pid, tid);
                return;
        }
        printf("process %s[%d] thread %llu caught burning CPU! "
               "It used more than %d%% CPU (Actual recent usage: %d%%) over %d seconds. "
               "thread lifetime cpu usage %d.%06d seconds, (%d.%06d user, %d.%06d system) "
               "ledger info: balance: %lld credit: %lld debit: %lld limit: %llu (%d%%) "
               "period: %llu time since last refill (ns): %llu %s\n",
               procname, pid, tid,
               percentage, usage_percent,  interval_sec,
               thread_total_time.seconds,  thread_total_time.microseconds,
               thread_user_time.seconds,   thread_user_time.microseconds,
               thread_system_time.seconds, thread_system_time.microseconds,
               lei.lei_balance,
               lei.lei_credit,             lei.lei_debit,
               lei.lei_limit,              limit_percent,
               lei.lei_refill_period,      lei.lei_last_refill,
               (fatal ? "[fatal violation]" : ""));


        code[0] = code[1] = 0;
        EXC_RESOURCE_ENCODE_TYPE(code[0], RESOURCE_TYPE_CPU);
        if (fatal) {
                EXC_RESOURCE_ENCODE_FLAVOR(code[0], FLAVOR_CPU_MONITOR_FATAL);
        }else {
                EXC_RESOURCE_ENCODE_FLAVOR(code[0], FLAVOR_CPU_MONITOR);
        }
        EXC_RESOURCE_CPUMONITOR_ENCODE_INTERVAL(code[0], interval_sec);
        EXC_RESOURCE_CPUMONITOR_ENCODE_PERCENTAGE(code[0], limit_percent);
        EXC_RESOURCE_CPUMONITOR_ENCODE_PERCENTAGE(code[1], usage_percent);
        exception_triage(EXC_RESOURCE, code, EXCEPTION_CODE_MAX);

        if (fatal) {
#if CONFIG_JETSAM
                jetsam_on_ledger_cpulimit_exceeded();
#else
                task_terminate_internal(task);
#endif
        }
}

#define UPDATE_IO_STATS(info, size)                             \
{                                                               \
        info.count++;                                           \
        info.size += size;                                      \
}

#define UPDATE_IO_STATS_ATOMIC(info, size)                      \
{                                                               \
        OSIncrementAtomic64((SInt64 *)&(info.count));           \
        OSAddAtomic64(size, (SInt64 *)&(info.size));            \
}

void thread_update_io_stats(thread_t thread, int size, int io_flags)
{
        int io_tier;

        if (thread->thread_io_stats == NULL || thread->task->task_io_stats == NULL)
                return;

        if (io_flags & DKIO_READ) {
                UPDATE_IO_STATS(thread->thread_io_stats->disk_reads, size);
                UPDATE_IO_STATS_ATOMIC(thread->task->task_io_stats->disk_reads, size);
        }
        
        if (io_flags & DKIO_META) {
                UPDATE_IO_STATS(thread->thread_io_stats->metadata, size);
                UPDATE_IO_STATS_ATOMIC(thread->task->task_io_stats->metadata, size);
        }
        
        if (io_flags & DKIO_PAGING) {
                UPDATE_IO_STATS(thread->thread_io_stats->paging, size);
                UPDATE_IO_STATS_ATOMIC(thread->task->task_io_stats->paging, size);
        }

        io_tier = ((io_flags & DKIO_TIER_MASK) >> DKIO_TIER_SHIFT);
        assert (io_tier < IO_NUM_PRIORITIES);

        UPDATE_IO_STATS(thread->thread_io_stats->io_priority[io_tier], size);
        UPDATE_IO_STATS_ATOMIC(thread->task->task_io_stats->io_priority[io_tier], size);

        /* Update Total I/O Counts */
        UPDATE_IO_STATS(thread->thread_io_stats->total_io, size);
        UPDATE_IO_STATS_ATOMIC(thread->task->task_io_stats->total_io, size);

}

void
init_thread_ledgers(void) {
        ledger_template_t t;
        int idx;
        
        assert(thread_ledger_template == NULL);

        if ((t = ledger_template_create("Per-thread ledger")) == NULL)
                panic("couldn't create thread ledger template");

        if ((idx = ledger_entry_add(t, "cpu_time", "sched", "ns")) < 0) {
                panic("couldn't create cpu_time entry for thread ledger template");
        }

        if (ledger_set_callback(t, idx, thread_cputime_callback, NULL, NULL) < 0) {
                panic("couldn't set thread ledger callback for cpu_time entry");
        }

        thread_ledgers.cpu_time = idx;
        
        thread_ledger_template = t;
}

/*
 * Returns currently applied CPU usage limit, or 0/0 if none is applied.
 */
int
thread_get_cpulimit(int *action, uint8_t *percentage, uint64_t *interval_ns)
{
        int64_t         abstime = 0;
        uint64_t        limittime = 0;
        thread_t        thread = current_thread();

        *percentage  = 0;
        *interval_ns = 0;
        *action      = 0;

        if (thread->t_threadledger == LEDGER_NULL) {
                /*
                 * This thread has no per-thread ledger, so it can't possibly
                 * have a CPU limit applied.
                 */
                return (KERN_SUCCESS);
        }

        ledger_get_period(thread->t_threadledger, thread_ledgers.cpu_time, interval_ns);
        ledger_get_limit(thread->t_threadledger, thread_ledgers.cpu_time, &abstime);

        if ((abstime == LEDGER_LIMIT_INFINITY) || (*interval_ns == 0)) {
                /*
                 * This thread's CPU time ledger has no period or limit; so it
                 * doesn't have a CPU limit applied.
                 */
                 return (KERN_SUCCESS);
        }

        /*
         * This calculation is the converse to the one in thread_set_cpulimit().
         */
        absolutetime_to_nanoseconds(abstime, &limittime);
        *percentage = (limittime * 100ULL) / *interval_ns;
        assert(*percentage <= 100);

        if (thread->options & TH_OPT_PROC_CPULIMIT) {
                assert((thread->options & TH_OPT_PRVT_CPULIMIT) == 0);

                *action = THREAD_CPULIMIT_BLOCK;
        } else if (thread->options & TH_OPT_PRVT_CPULIMIT) {
                assert((thread->options & TH_OPT_PROC_CPULIMIT) == 0);

                *action = THREAD_CPULIMIT_EXCEPTION;
        } else {
                *action = THREAD_CPULIMIT_DISABLE;
        }

        return (KERN_SUCCESS);
}

/*
 * Set CPU usage limit on a thread.
 *
 * Calling with percentage of 0 will unset the limit for this thread.
 */
int
thread_set_cpulimit(int action, uint8_t percentage, uint64_t interval_ns)
{
        thread_t        thread = current_thread(); 
        ledger_t        l;
        uint64_t        limittime = 0;
        uint64_t        abstime = 0;

        assert(percentage <= 100);

        if (action == THREAD_CPULIMIT_DISABLE) {
                /*
                 * Remove CPU limit, if any exists.
                 */
                if (thread->t_threadledger != LEDGER_NULL) {
                        l = thread->t_threadledger;
                        ledger_set_limit(l, thread_ledgers.cpu_time, LEDGER_LIMIT_INFINITY, 0);
                        ledger_set_action(l, thread_ledgers.cpu_time, LEDGER_ACTION_IGNORE);
                        thread->options &= ~(TH_OPT_PROC_CPULIMIT | TH_OPT_PRVT_CPULIMIT);
                }

                return (0);
        }

        if (interval_ns < MINIMUM_CPULIMIT_INTERVAL_MS * NSEC_PER_MSEC) {
                return (KERN_INVALID_ARGUMENT);
        }

        l = thread->t_threadledger;
        if (l == LEDGER_NULL) {
                /*
                 * This thread doesn't yet have a per-thread ledger; so create one with the CPU time entry active.
                 */
                if ((l = ledger_instantiate(thread_ledger_template, LEDGER_CREATE_INACTIVE_ENTRIES)) == LEDGER_NULL)
                        return (KERN_RESOURCE_SHORTAGE);

                /*
                 * We are the first to create this thread's ledger, so only activate our entry.
                 */
                ledger_entry_setactive(l, thread_ledgers.cpu_time);
                thread->t_threadledger = l;
        }

        /*
         * The limit is specified as a percentage of CPU over an interval in nanoseconds.
         * Calculate the amount of CPU time that the thread needs to consume in order to hit the limit.
         */
        limittime = (interval_ns * percentage) / 100;
        nanoseconds_to_absolutetime(limittime, &abstime); 
        ledger_set_limit(l, thread_ledgers.cpu_time, abstime, cpumon_ustackshots_trigger_pct);
        /*
         * Refill the thread's allotted CPU time every interval_ns nanoseconds.
         */
        ledger_set_period(l, thread_ledgers.cpu_time, interval_ns);

        if (action == THREAD_CPULIMIT_EXCEPTION) {
                /*
                 * We don't support programming the CPU usage monitor on a task if any of its
                 * threads have a per-thread blocking CPU limit configured.
                 */
                if (thread->options & TH_OPT_PRVT_CPULIMIT) {
                        panic("CPU usage monitor activated, but blocking thread limit exists");
                }

                /*
                 * Make a note that this thread's CPU limit is being used for the task-wide CPU
                 * usage monitor. We don't have to arm the callback which will trigger the
                 * exception, because that was done for us in ledger_instantiate (because the
                 * ledger template used has a default callback).
                 */
                thread->options |= TH_OPT_PROC_CPULIMIT;
        } else {
                /*
                 * We deliberately override any CPU limit imposed by a task-wide limit (eg
                 * CPU usage monitor).
                 */
                thread->options &= ~TH_OPT_PROC_CPULIMIT;               

                thread->options |= TH_OPT_PRVT_CPULIMIT;
                /* The per-thread ledger template by default has a callback for CPU time */
                ledger_disable_callback(l, thread_ledgers.cpu_time);
                ledger_set_action(l, thread_ledgers.cpu_time, LEDGER_ACTION_BLOCK);
        }

        return (0);
}

static void
sched_call_null(
__unused        int                     type,
__unused        thread_t        thread)
{
        return;
}

void
thread_sched_call(
        thread_t                thread,
        sched_call_t    call)
{
        thread->sched_call = (call != NULL)? call: sched_call_null;
}

void
thread_static_param(
        thread_t                thread,
        boolean_t               state)
{
        thread_mtx_lock(thread);
        thread->static_param = state;
        thread_mtx_unlock(thread);
}

uint64_t
thread_tid(
        thread_t        thread)
{
        return (thread != THREAD_NULL? thread->thread_id: 0);
}

uint16_t        thread_set_tag(thread_t th, uint16_t tag) {
        return thread_set_tag_internal(th, tag);
}
uint16_t        thread_get_tag(thread_t th) {
        return thread_get_tag_internal(th);
}

uint64_t
thread_dispatchqaddr(
        thread_t                thread)
{
        uint64_t        dispatchqueue_addr = 0;
        uint64_t        thread_handle = 0;

        if (thread != THREAD_NULL) {
                thread_handle = thread->machine.cthread_self;
                
                 if (thread->inspection == TRUE)
                        dispatchqueue_addr = thread_handle + get_task_dispatchqueue_offset(thread->task);
                 else if (thread->task->bsd_info)
                        dispatchqueue_addr = thread_handle + get_dispatchqueue_offset_from_proc(thread->task->bsd_info);
        }

        return (dispatchqueue_addr);
}

/*
 * Export routines to other components for things that are done as macros
 * within the osfmk component.
 */

#undef thread_reference
void thread_reference(thread_t thread);
void
thread_reference(
        thread_t        thread)
{
        if (thread != THREAD_NULL)
                thread_reference_internal(thread);
}

#undef thread_should_halt

boolean_t
thread_should_halt(
        thread_t                th)
{
        return (thread_should_halt_fast(th));
}

/*
 * thread_set_voucher_name - reset the voucher port name bound to this thread
 *
 * Conditions:  nothing locked
 *
 *      If we already converted the previous name to a cached voucher
 *      reference, then we discard that reference here.  The next lookup
 *      will cache it again.
 */

kern_return_t
thread_set_voucher_name(mach_port_name_t voucher_name)
{
        thread_t thread = current_thread();
        ipc_voucher_t new_voucher = IPC_VOUCHER_NULL;
        ipc_voucher_t voucher;
#ifdef CONFIG_BANK
        ledger_t bankledger = NULL;
#endif

        if (MACH_PORT_DEAD == voucher_name)
                return KERN_INVALID_RIGHT;

        /*
         * agressively convert to voucher reference
         */
        if (MACH_PORT_VALID(voucher_name)) {
                new_voucher = convert_port_name_to_voucher(voucher_name);
                if (IPC_VOUCHER_NULL == new_voucher)
                        return KERN_INVALID_ARGUMENT;
        }
#ifdef CONFIG_BANK
        bankledger = bank_get_voucher_ledger(new_voucher);
#endif

        thread_mtx_lock(thread);
        voucher = thread->ith_voucher;
        thread->ith_voucher_name = voucher_name;
        thread->ith_voucher = new_voucher;
#ifdef CONFIG_BANK
        bank_swap_thread_bank_ledger(thread, bankledger);
#endif
        thread_mtx_unlock(thread);

        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
                                  MACHDBG_CODE(DBG_MACH_IPC,MACH_THREAD_SET_VOUCHER) | DBG_FUNC_NONE,
                                  (uintptr_t)thread_tid(thread),
                                  (uintptr_t)voucher_name,
                                  VM_KERNEL_ADDRPERM((uintptr_t)new_voucher),
                                  1, 0);

        if (IPC_VOUCHER_NULL != voucher)
                ipc_voucher_release(voucher);

        return KERN_SUCCESS;
}

/* 
 *  thread_get_mach_voucher - return a voucher reference for the specified thread voucher
 *
 *  Conditions:  nothing locked
 *
 *  A reference to the voucher may be lazily pending, if someone set the voucher name
 *  but nobody has done a lookup yet.  In that case, we'll have to do the equivalent
 *  lookup here.
 *
 *  NOTE:       At the moment, there is no distinction between the current and effective
 *              vouchers because we only set them at the thread level currently.
 */
kern_return_t 
thread_get_mach_voucher(
        thread_act_t            thread,
        mach_voucher_selector_t __unused which,
        ipc_voucher_t           *voucherp)
{
        ipc_voucher_t           voucher;
        mach_port_name_t        voucher_name;

        if (THREAD_NULL == thread)
                return KERN_INVALID_ARGUMENT;

        thread_mtx_lock(thread);
        voucher = thread->ith_voucher;

        /* if already cached, just return a ref */
        if (IPC_VOUCHER_NULL != voucher) {
                ipc_voucher_reference(voucher);
                thread_mtx_unlock(thread);
                *voucherp = voucher;
                return KERN_SUCCESS;
        }

        voucher_name = thread->ith_voucher_name;

        /* convert the name to a port, then voucher reference */
        if (MACH_PORT_VALID(voucher_name)) {
                ipc_port_t port;

                if (KERN_SUCCESS !=
                    ipc_object_copyin(thread->task->itk_space, voucher_name,
                                      MACH_MSG_TYPE_COPY_SEND, (ipc_object_t *)&port)) {
                        thread->ith_voucher_name = MACH_PORT_NULL;
                        thread_mtx_unlock(thread);
                        *voucherp = IPC_VOUCHER_NULL;
                        return KERN_SUCCESS;
                }

                /* convert to a voucher ref to return, and cache a ref on thread */
                voucher = convert_port_to_voucher(port);
                ipc_voucher_reference(voucher);
                thread->ith_voucher = voucher;
                thread_mtx_unlock(thread);

                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
                                          MACHDBG_CODE(DBG_MACH_IPC,MACH_THREAD_SET_VOUCHER) | DBG_FUNC_NONE,
                                          (uintptr_t)thread_tid(thread),
                                          (uintptr_t)port,
                                          VM_KERNEL_ADDRPERM((uintptr_t)voucher),
                                          2, 0);


                ipc_port_release_send(port);
        } else
                thread_mtx_unlock(thread);

        *voucherp = voucher;
        return KERN_SUCCESS;
}

/* 
 *  thread_set_mach_voucher - set a voucher reference for the specified thread voucher
 *
 *  Conditions: callers holds a reference on the voucher.
 *              nothing locked.
 *
 *  We grab another reference to the voucher and bind it to the thread.  Any lazy
 *  binding is erased.  The old voucher reference associated with the thread is
 *  discarded.
 */
kern_return_t 
thread_set_mach_voucher(
        thread_t                thread,
        ipc_voucher_t           voucher)
{
        ipc_voucher_t old_voucher;
#ifdef CONFIG_BANK
        ledger_t bankledger = NULL;
#endif

        if (THREAD_NULL == thread)
                return KERN_INVALID_ARGUMENT;

        if (thread != current_thread() || thread->started)
                return KERN_INVALID_ARGUMENT;


        ipc_voucher_reference(voucher);
#ifdef CONFIG_BANK
        bankledger = bank_get_voucher_ledger(voucher);
#endif
        thread_mtx_lock(thread);
        old_voucher = thread->ith_voucher;
        thread->ith_voucher = voucher;
        thread->ith_voucher_name = MACH_PORT_NULL;
#ifdef CONFIG_BANK
        bank_swap_thread_bank_ledger(thread, bankledger);
#endif
        thread_mtx_unlock(thread);

        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
                                  MACHDBG_CODE(DBG_MACH_IPC,MACH_THREAD_SET_VOUCHER) | DBG_FUNC_NONE,
                                  (uintptr_t)thread_tid(thread),
                                  (uintptr_t)MACH_PORT_NULL,
                                  VM_KERNEL_ADDRPERM((uintptr_t)voucher),
                                  3, 0);

        ipc_voucher_release(old_voucher);

        return KERN_SUCCESS;
}

/* 
 *  thread_swap_mach_voucher - swap a voucher reference for the specified thread voucher
 *
 *  Conditions: callers holds a reference on the new and presumed old voucher(s).
 *              nothing locked.
 *
 *  If the old voucher is still the same as passed in, replace it with new voucher
 *  and discard the old (and the reference passed in).  Otherwise, discard the new
 *  and return an updated old voucher.
 */
kern_return_t
thread_swap_mach_voucher(
        thread_t                thread,
        ipc_voucher_t           new_voucher,
        ipc_voucher_t           *in_out_old_voucher)
{
        mach_port_name_t old_voucher_name;
        ipc_voucher_t old_voucher;
#ifdef CONFIG_BANK
        ledger_t bankledger = NULL;
#endif

        if (THREAD_NULL == thread)
                return KERN_INVALID_TASK;

        if (thread != current_thread() || thread->started)
                return KERN_INVALID_ARGUMENT;

#ifdef CONFIG_BANK
        bankledger = bank_get_voucher_ledger(new_voucher);
#endif

        thread_mtx_lock(thread);

        old_voucher = thread->ith_voucher;

        if (IPC_VOUCHER_NULL == old_voucher) {
                old_voucher_name = thread->ith_voucher_name;

                /* perform lazy binding if needed */
                if (MACH_PORT_VALID(old_voucher_name)) {
                        old_voucher = convert_port_name_to_voucher(old_voucher_name);
                        thread->ith_voucher_name = MACH_PORT_NULL;
                        thread->ith_voucher = old_voucher;

                        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
                                                  MACHDBG_CODE(DBG_MACH_IPC,MACH_THREAD_SET_VOUCHER) | DBG_FUNC_NONE,
                                                  (uintptr_t)thread_tid(thread),
                                                  (uintptr_t)old_voucher_name,
                                                  VM_KERNEL_ADDRPERM((uintptr_t)old_voucher),
                                                  4, 0);

                }
        }

        /* swap in new voucher, if old voucher matches the one supplied */
        if (old_voucher == *in_out_old_voucher) {
                ipc_voucher_reference(new_voucher);
                thread->ith_voucher = new_voucher;
                thread->ith_voucher_name = MACH_PORT_NULL;
#ifdef CONFIG_BANK
                bank_swap_thread_bank_ledger(thread, bankledger);
#endif
                thread_mtx_unlock(thread);

                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
                                          MACHDBG_CODE(DBG_MACH_IPC,MACH_THREAD_SET_VOUCHER) | DBG_FUNC_NONE,
                                          (uintptr_t)thread_tid(thread),
                                          (uintptr_t)MACH_PORT_NULL,
                                          VM_KERNEL_ADDRPERM((uintptr_t)new_voucher),
                                          5, 0);

                ipc_voucher_release(old_voucher);

                *in_out_old_voucher = IPC_VOUCHER_NULL;
                return KERN_SUCCESS;
        }

        /* Otherwise, just return old voucher reference */
        ipc_voucher_reference(old_voucher);
        thread_mtx_unlock(thread);
        *in_out_old_voucher = old_voucher;
        return KERN_SUCCESS;
}

/* 
 *  thread_get_current_voucher_origin_pid - get the pid of the originator of the current voucher.
 */
kern_return_t
thread_get_current_voucher_origin_pid(
        int32_t      *pid)
{
        uint32_t buf_size;
        kern_return_t kr;
        thread_t thread = current_thread();
        
        buf_size = sizeof(*pid);
        kr = mach_voucher_attr_command(thread->ith_voucher,
                MACH_VOUCHER_ATTR_KEY_BANK,
                BANK_ORIGINATOR_PID,
                NULL,
                0,
                (mach_voucher_attr_content_t)pid,
                &buf_size);

        return kr;
}

#if CONFIG_DTRACE
uint32_t dtrace_get_thread_predcache(thread_t thread)
{
        if (thread != THREAD_NULL)
                return thread->t_dtrace_predcache;
        else
                return 0;
}

int64_t dtrace_get_thread_vtime(thread_t thread)
{
        if (thread != THREAD_NULL)
                return thread->t_dtrace_vtime;
        else
                return 0;
}

int dtrace_get_thread_last_cpu_id(thread_t thread)
{
        if ((thread != THREAD_NULL) && (thread->last_processor != PROCESSOR_NULL)) {
                return thread->last_processor->cpu_id;
        } else {
                return -1;
        }
}

int64_t dtrace_get_thread_tracing(thread_t thread)
{
        if (thread != THREAD_NULL)
                return thread->t_dtrace_tracing;
        else
                return 0;
}

boolean_t dtrace_get_thread_reentering(thread_t thread)
{
        if (thread != THREAD_NULL)
                return (thread->options & TH_OPT_DTRACE) ? TRUE : FALSE;
        else
                return 0;
}

vm_offset_t dtrace_get_kernel_stack(thread_t thread)
{
        if (thread != THREAD_NULL)
                return thread->kernel_stack;
        else
                return 0;
}

int64_t dtrace_calc_thread_recent_vtime(thread_t thread)
{
        if (thread != THREAD_NULL) {
                processor_t             processor = current_processor();
                uint64_t                                abstime = mach_absolute_time();
                timer_t                                 timer;

                timer = PROCESSOR_DATA(processor, thread_timer);

                return timer_grab(&(thread->system_timer)) + timer_grab(&(thread->user_timer)) +
                                (abstime - timer->tstamp); /* XXX need interrupts off to prevent missed time? */
        } else
                return 0;
}

void dtrace_set_thread_predcache(thread_t thread, uint32_t predcache)
{
        if (thread != THREAD_NULL)
                thread->t_dtrace_predcache = predcache;
}

void dtrace_set_thread_vtime(thread_t thread, int64_t vtime)
{
        if (thread != THREAD_NULL)
                thread->t_dtrace_vtime = vtime;
}

void dtrace_set_thread_tracing(thread_t thread, int64_t accum)
{
        if (thread != THREAD_NULL)
                thread->t_dtrace_tracing = accum;
}

void dtrace_set_thread_reentering(thread_t thread, boolean_t vbool)
{
        if (thread != THREAD_NULL) {
                if (vbool)
                        thread->options |= TH_OPT_DTRACE;
                else
                        thread->options &= (~TH_OPT_DTRACE);
        }
}

vm_offset_t dtrace_set_thread_recover(thread_t thread, vm_offset_t recover)
{
        vm_offset_t prev = 0;

        if (thread != THREAD_NULL) {
                prev = thread->recover;
                thread->recover = recover;
        }
        return prev;
}

void dtrace_thread_bootstrap(void)
{
        task_t task = current_task();

        if (task->thread_count == 1) {
                thread_t thread = current_thread();
                if (thread->t_dtrace_flags & TH_DTRACE_EXECSUCCESS) {
                        thread->t_dtrace_flags &= ~TH_DTRACE_EXECSUCCESS;
                        DTRACE_PROC(exec__success);
                }
                DTRACE_PROC(start);
        }
        DTRACE_PROC(lwp__start);

}

void
dtrace_thread_didexec(thread_t thread)
{
        thread->t_dtrace_flags |= TH_DTRACE_EXECSUCCESS;
}
#endif /* CONFIG_DTRACE */