xnu-201.tar.gz

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

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This 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 OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_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/thread_shuttle 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 <cpus.h>
#include <mach_host.h>
#include <simple_clock.h>
#include <mach_debug.h>
#include <mach_prof.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 <kern/ast.h>
#include <kern/cpu_data.h>
#include <kern/counters.h>
#include <kern/etap_macros.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/mk_sp.h> /*** ??? fix so this can be removed ***/
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/thread_act.h>
#include <kern/thread_swap.h>
#include <kern/host.h>
#include <kern/zalloc.h>
#include <vm/vm_kern.h>
#include <ipc/ipc_kmsg.h>
#include <ipc/ipc_port.h>
#include <machine/thread.h>             /* for MACHINE_STACK */
#include <kern/profile.h>
#include <kern/assert.h>
#include <sys/kdebug.h>

/*
 * Exported interfaces
 */

#include <mach/thread_act_server.h>
#include <mach/mach_host_server.h>

/*
 * Per-Cpu stashed global state
 */
vm_offset_t                     active_stacks[NCPUS];   /* per-cpu active stacks        */
vm_offset_t                     kernel_stack[NCPUS];    /* top of active stacks         */
thread_act_t            active_kloaded[NCPUS];  /*  + act if kernel loaded      */

struct zone                     *thread_shuttle_zone;

queue_head_t            reaper_queue;
decl_simple_lock_data(,reaper_lock)
thread_call_t           thread_reaper_call;

extern int              tick;

extern void             pcb_module_init(void);

/* private */
static struct thread_shuttle    thr_sh_template;

#if     MACH_DEBUG

#ifdef  MACHINE_STACK
extern void     stack_statistics(
                        unsigned int    *totalp,
                        vm_size_t       *maxusagep);
#endif  /* MACHINE_STACK */
#endif  /* MACH_DEBUG */

/* Forwards */
void            thread_collect_scan(void);

kern_return_t thread_create_shuttle(
        thread_act_t                    thr_act,
        integer_t                               priority,
        void                                    (*start)(void),
        thread_t                                *new_thread);

extern void             Load_context(
        thread_t                thread);


/*
 *      Machine-dependent code must define:
 *              thread_machine_init
 *              thread_machine_terminate
 *              thread_machine_collect
 *
 *      The thread->pcb field is reserved for machine-dependent code.
 */

#ifdef  MACHINE_STACK
/*
 *      Machine-dependent code must define:
 *              stack_alloc_try
 *              stack_alloc
 *              stack_free
 *              stack_free_stack
 *              stack_collect
 *      and if MACH_DEBUG:
 *              stack_statistics
 */
#else   /* MACHINE_STACK */
/*
 *      We allocate stacks from generic kernel VM.
 *      Machine-dependent code must define:
 *              machine_kernel_stack_init
 *
 *      The stack_free_list can only be accessed at splsched,
 *      because stack_alloc_try/thread_invoke operate at splsched.
 */

decl_simple_lock_data(,stack_lock_data)         /* splsched only */
#define stack_lock()    simple_lock(&stack_lock_data)
#define stack_unlock()  simple_unlock(&stack_lock_data)

mutex_t stack_map_lock;                         /* Lock when allocating stacks maps */
vm_map_t stack_map;                                     /* Map for allocating stacks */
vm_offset_t stack_free_list;            /* splsched only */
unsigned int stack_free_max = 0;
unsigned int stack_free_count = 0;      /* splsched only */
unsigned int stack_free_limit = 1;      /* Arbitrary  */

unsigned int stack_alloc_hits = 0;      /* debugging */
unsigned int stack_alloc_misses = 0;    /* debugging */

unsigned int stack_alloc_total = 0;
unsigned int stack_alloc_hiwater = 0;
unsigned int stack_alloc_bndry = 0;


/*
 *      The next field is at the base of the stack,
 *      so the low end is left unsullied.
 */

#define stack_next(stack) (*((vm_offset_t *)((stack) + KERNEL_STACK_SIZE) - 1))

/*
 *      stack_alloc:
 *
 *      Allocate a kernel stack for an activation.
 *      May block.
 */
vm_offset_t
stack_alloc(
        thread_t thread,
        void (*start_pos)(thread_t))
{
        vm_offset_t     stack = thread->kernel_stack;
        spl_t                   s;

        if (stack)
                return (stack);

/*
 *      We first try the free list.  It is probably empty, or
 *      stack_alloc_try would have succeeded, but possibly a stack was
 *      freed before the swapin thread got to us.
 *
 *      We allocate stacks from their own map which is submaps of the
 *      kernel map.  Because we want to have a guard page (at least) in
 *      front of each stack to catch evil code that overruns its stack, we
 *      allocate the stack on aligned boundaries.  The boundary is
 *      calculated as the next power of 2 above the stack size. For
 *      example, a stack of 4 pages would have a boundry of 8, likewise 5
 *      would also be 8.
 *
 *      We limit the number of stacks to be one allocation chunk
 *      (THREAD_CHUNK) more than the maximum number of threads
 *      (THREAD_MAX).  The extra is to allow for priviliged threads that
 *      can sometimes have 2 stacks.
 *
 */

        s = splsched();
        stack_lock();
        stack = stack_free_list;
        if (stack != 0) {
                stack_free_list = stack_next(stack);
                stack_free_count--;
        }
        stack_unlock();
        splx(s);

        if (stack != 0) {                                                       /* Did we find a free one? */
                stack_attach(thread, stack, start_pos); /* Initialize it */
                return (stack);                                                 /* Send it on home */
        }
                
        if (kernel_memory_allocate(
                                        stack_map, &stack,
                                                KERNEL_STACK_SIZE, stack_alloc_bndry - 1,
                                                                                KMA_KOBJECT) != KERN_SUCCESS)
                panic("stack_alloc: no space left for stack maps");

        stack_alloc_total++;
        if (stack_alloc_total > stack_alloc_hiwater)
                stack_alloc_hiwater = stack_alloc_total;

        stack_attach(thread, stack, start_pos);
        return (stack);
}

/*
 *      stack_free:
 *
 *      Free a kernel stack.
 *      Called at splsched.
 */

void
stack_free(
        thread_t thread)
{
    vm_offset_t stack = stack_detach(thread);

        assert(stack);
        if (stack != thread->stack_privilege) {
                stack_lock();
                stack_next(stack) = stack_free_list;
                stack_free_list = stack;
                if (++stack_free_count > stack_free_max)
                        stack_free_max = stack_free_count;
                stack_unlock();
        }
}

static void
stack_free_stack(
        vm_offset_t             stack)
{
        spl_t   s;

        s = splsched();
        stack_lock();
        stack_next(stack) = stack_free_list;
        stack_free_list = stack;
        if (++stack_free_count > stack_free_max)
                stack_free_max = stack_free_count;
        stack_unlock();
        splx(s);
}

/*
 *      stack_collect:
 *
 *      Free excess kernel stacks.
 *      May block.
 */

void
stack_collect(void)
{
        vm_offset_t     stack;
        int                     i;
        spl_t           s;

        s = splsched();
        stack_lock();
        while (stack_free_count > stack_free_limit) {
                stack = stack_free_list;
                stack_free_list = stack_next(stack);
                stack_free_count--;
                stack_unlock();
                splx(s);

                if (vm_map_remove(
                                        stack_map, stack, stack + KERNEL_STACK_SIZE,
                                                                        VM_MAP_REMOVE_KUNWIRE) != KERN_SUCCESS)
                        panic("stack_collect: vm_map_remove failed");

                s = splsched();
                stack_lock();
                stack_alloc_total--;
        }
        stack_unlock();
        splx(s);
}


#if     MACH_DEBUG
/*
 *      stack_statistics:
 *
 *      Return statistics on cached kernel stacks.
 *      *maxusagep must be initialized by the caller.
 */

void
stack_statistics(
        unsigned int    *totalp,
        vm_size_t       *maxusagep)
{
        spl_t   s;

        s = splsched();
        stack_lock();

        *totalp = stack_free_count;
        *maxusagep = 0;

        stack_unlock();
        splx(s);
}
#endif  /* MACH_DEBUG */

#endif  /* MACHINE_STACK */


stack_fake_zone_info(int *count, vm_size_t *cur_size, vm_size_t *max_size, vm_size_t *elem_size,
                     vm_size_t *alloc_size, int *collectable, int *exhaustable)
{
        *count      = stack_alloc_total - stack_free_count;
        *cur_size   = KERNEL_STACK_SIZE * stack_alloc_total;
        *max_size   = KERNEL_STACK_SIZE * stack_alloc_hiwater;
        *elem_size  = KERNEL_STACK_SIZE;
        *alloc_size = KERNEL_STACK_SIZE;
        *collectable = 1;
        *exhaustable = 0;
}


/*
 *      stack_privilege:
 *
 *      stack_alloc_try on this thread must always succeed.
 */

void
stack_privilege(
        register thread_t thread)
{
        /*
         *      This implementation only works for the current thread.
         */

        if (thread != current_thread())
                panic("stack_privilege");

        if (thread->stack_privilege == 0)
                thread->stack_privilege = current_stack();
}

/*
 *      stack_alloc_try:
 *
 *      Non-blocking attempt to allocate a kernel stack.
 *      Called at splsched with the thread locked.
 */

boolean_t stack_alloc_try(
        thread_t        thread,
        void            (*start_pos)(thread_t))
{
        register vm_offset_t stack = thread->stack_privilege;

        if (stack == 0) {
                stack_lock();

                stack = stack_free_list;
                if (stack != (vm_offset_t)0) {
                        stack_free_list = stack_next(stack);
                        stack_free_count--;
                }

                stack_unlock();
        }

        if (stack != 0) {
                stack_attach(thread, stack, start_pos);
                stack_alloc_hits++;

                return (TRUE);
        }
        else {
                stack_alloc_misses++;

                return (FALSE);
        }
}

uint64_t                        max_unsafe_computation;
extern int                      max_unsafe_quanta;

uint32_t                        sched_safe_duration;

uint64_t                        max_poll_computation;
extern int                      max_poll_quanta;

uint32_t                        std_quantum;
uint32_t                        min_std_quantum;

uint32_t                        max_rt_quantum;
uint32_t                        min_rt_quantum;

void
thread_init(void)
{
        kern_return_t ret;
        unsigned int stack;
        
        thread_shuttle_zone = zinit(
                        sizeof(struct thread_shuttle),
                        THREAD_MAX * sizeof(struct thread_shuttle),
                        THREAD_CHUNK * sizeof(struct thread_shuttle),
                        "threads");

        /*
         *      Fill in a template thread_shuttle for fast initialization.
         *      [Fields that must be (or are typically) reset at
         *      time of creation are so noted.]
         */

        /* thr_sh_template.links (none) */
        thr_sh_template.runq = RUN_QUEUE_NULL;


        /* thr_sh_template.task (later) */
        /* thr_sh_template.thread_list (later) */
        /* thr_sh_template.pset_threads (later) */

        /* one ref for pset, one for activation */
        thr_sh_template.ref_count = 2;

        thr_sh_template.wait_event = NO_EVENT;
        thr_sh_template.wait_result = KERN_SUCCESS;
        thr_sh_template.wait_queue = WAIT_QUEUE_NULL;
        thr_sh_template.wake_active = FALSE;
        thr_sh_template.state = TH_STACK_HANDOFF | TH_WAIT | TH_UNINT;
        thr_sh_template.interruptible = TRUE;
        thr_sh_template.continuation = (void (*)(void))0;
        thr_sh_template.top_act = THR_ACT_NULL;

        thr_sh_template.importance = 0;
        thr_sh_template.sched_mode = 0;
        thr_sh_template.safe_mode = 0;

        thr_sh_template.priority = 0;
        thr_sh_template.sched_pri = 0;
        thr_sh_template.depress_priority = -1;
        thr_sh_template.max_priority = 0;
        thr_sh_template.task_priority = 0;

        thr_sh_template.current_quantum = 0;

        thr_sh_template.metered_computation = 0;
        thr_sh_template.computation_epoch = 0;

        thr_sh_template.cpu_usage = 0;
        thr_sh_template.cpu_delta = 0;
        thr_sh_template.sched_usage = 0;
        thr_sh_template.sched_delta = 0;
        thr_sh_template.sched_stamp = 0;
        thr_sh_template.sleep_stamp = 0;
        thr_sh_template.safe_release = 0;

        thr_sh_template.vm_privilege = FALSE;

        timer_init(&(thr_sh_template.user_timer));
        timer_init(&(thr_sh_template.system_timer));
        thr_sh_template.user_timer_save.low = 0;
        thr_sh_template.user_timer_save.high = 0;
        thr_sh_template.system_timer_save.low = 0;
        thr_sh_template.system_timer_save.high = 0;

        thr_sh_template.active = FALSE; /* reset */

        /* thr_sh_template.processor_set (later) */
#if     NCPUS > 1
        thr_sh_template.bound_processor = PROCESSOR_NULL;
#endif  /*NCPUS > 1*/
#if     MACH_HOST
        thr_sh_template.may_assign = TRUE;
        thr_sh_template.assign_active = FALSE;
#endif  /* MACH_HOST */
        thr_sh_template.funnel_state = 0;

#if     NCPUS > 1
        /* thr_sh_template.last_processor  (later) */
#endif  /* NCPUS > 1 */

        /*
         *      Initialize other data structures used in
         *      this module.
         */

        queue_init(&reaper_queue);
        simple_lock_init(&reaper_lock, ETAP_THREAD_REAPER);
    thr_sh_template.funnel_lock = THR_FUNNEL_NULL;

#ifndef MACHINE_STACK
        simple_lock_init(&stack_lock_data, ETAP_THREAD_STACK);  /* Initialize the stack lock */
        
        if (KERNEL_STACK_SIZE < round_page(KERNEL_STACK_SIZE)) {        /* Kernel stacks must be multiples of pages */
                panic("thread_init: kernel stack size (%08X) must be a multiple of page size (%08X)\n", 
                        KERNEL_STACK_SIZE, PAGE_SIZE);
        }
        
        for(stack_alloc_bndry = PAGE_SIZE; stack_alloc_bndry <= KERNEL_STACK_SIZE; stack_alloc_bndry <<= 1);    /* Find next power of 2 above stack size */

        ret = kmem_suballoc(kernel_map,                 /* Suballocate from the kernel map */

                &stack,
                (stack_alloc_bndry * (THREAD_MAX + 64)),        /* Allocate enough for all of it */
                FALSE,                                                          /* Say not pageable so that it is wired */
                TRUE,                                                           /* Allocate from anywhere */
                &stack_map);                                            /* Allocate a submap */
                
        if(ret != KERN_SUCCESS) {                               /* Did we get one? */
                panic("thread_init: kmem_suballoc for stacks failed - ret = %d\n", ret);        /* Die */
        }       
        stack = vm_map_min(stack_map);                  /* Make sure we skip the first hunk */
        ret = vm_map_enter(stack_map, &stack, PAGE_SIZE, 0,     /* Make sure there is nothing at the start */
                0,                                                                      /* Force it at start */
                VM_OBJECT_NULL, 0,                                      /* No object yet */
                FALSE,                                                          /* No copy */
                VM_PROT_NONE,                                           /* Allow no access */
                VM_PROT_NONE,                                           /* Allow no access */
                VM_INHERIT_DEFAULT);                            /* Just be normal */
                
        if(ret != KERN_SUCCESS) {                                       /* Did it work? */
                panic("thread_init: dummy alignment allocation failed; ret = %d\n", ret);
        }
                
#endif  /* MACHINE_STACK */

#if     MACH_LDEBUG
        thr_sh_template.kthread = FALSE;
        thr_sh_template.mutex_count = 0;
#endif  /* MACH_LDEBUG */

        {
                uint64_t                        abstime;

                clock_interval_to_absolutetime_interval(
                                                        std_quantum_us, NSEC_PER_USEC, &abstime);
                assert((abstime >> 32) == 0 && (uint32_t)abstime != 0);
                std_quantum = abstime;

                /* 250 us */
                clock_interval_to_absolutetime_interval(250, NSEC_PER_USEC, &abstime);
                assert((abstime >> 32) == 0 && (uint32_t)abstime != 0);
                min_std_quantum = abstime;

                /* 50 us */
                clock_interval_to_absolutetime_interval(50, NSEC_PER_USEC, &abstime);
                assert((abstime >> 32) == 0 && (uint32_t)abstime != 0);
                min_rt_quantum = abstime;

                /* 50 ms */
                clock_interval_to_absolutetime_interval(
                                                                                50, 1000*NSEC_PER_USEC, &abstime);
                assert((abstime >> 32) == 0 && (uint32_t)abstime != 0);
                max_rt_quantum = abstime;

                max_unsafe_computation = max_unsafe_quanta * std_quantum;
                max_poll_computation = max_poll_quanta * std_quantum;

                sched_safe_duration = 2 * max_unsafe_quanta *
                                                                                (std_quantum_us / (1000 * 1000)) *
                                                                                                (1 << SCHED_TICK_SHIFT);
        }

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

void
thread_reaper_enqueue(
        thread_t                thread)
{
        /*
         * thread lock is already held, splsched()
         * not necessary here.
         */
        simple_lock(&reaper_lock);
        enqueue_tail(&reaper_queue, (queue_entry_t)thread);
        simple_unlock(&reaper_lock);

        thread_call_enter(thread_reaper_call);
}


/*
 *      Routine: thread_terminate_self
 *
 *              This routine is called by a thread which has unwound from
 *              its current RPC and kernel contexts and found that it's
 *              root activation has been marked for extinction.  This lets
 *              it clean up the last few things that can only be cleaned
 *              up in this context and then impale itself on the reaper
 *              queue.
 *
 *              When the reaper gets the thread, it will deallocate the
 *              thread_act's reference on itself, which in turn will release
 *              its own reference on this thread. By doing things in that
 *              order, a thread_act will always have a valid thread - but the
 *              thread may persist beyond having a thread_act (but must never
 *              run like that).
 */
void
thread_terminate_self(void)
{
        register thread_t       thread = current_thread();
        thread_act_t            thr_act = thread->top_act;
        task_t                  task = thr_act->task;
        int                     active_acts;
        spl_t                   s;

        /*
         * We should be at the base of the inheritance chain.
         */
        assert(thr_act->thread == thread);

        _mk_sp_thread_depress_abort(thread, TRUE);

        /*
         * Check to see if this is the last active activation.  By
         * this we mean the last activation to call thread_terminate_self.
         * If so, and the task is associated with a BSD process, we
         * need to call BSD and let them clean up.
         */
        task_lock(task);
        active_acts = --task->active_act_count;
        task_unlock(task);
        if (!active_acts && task->bsd_info)
                proc_exit(task->bsd_info);

#ifdef CALLOUT_RPC_MODEL
        if (thr_act->lower) {
                /*
                 * JMM - RPC will not be using a callout/stack manipulation
                 * mechanism.  instead we will let it return normally as if
                 * from a continuation.  Accordingly, these need to be cleaned
                 * up a bit.
                 */
                act_switch_swapcheck(thread, (ipc_port_t)0);
                act_lock(thr_act);      /* hierarchy violation XXX */
                (void) switch_act(THR_ACT_NULL);
                assert(thr_act->ref_count == 1);        /* XXX */
                /* act_deallocate(thr_act);                XXX */
                prev_act = thread->top_act;
                /* 
                 * disable preemption to protect kernel stack changes
                 * disable_preemption();
                 * MACH_RPC_RET(prev_act) = KERN_RPC_SERVER_TERMINATED;
                 * machine_kernel_stack_init(thread, mach_rpc_return_error);
                 */
                act_unlock(thr_act);

                /*
                 * Load_context(thread);
                 */
                /* NOTREACHED */
        }

#else /* !CALLOUT_RPC_MODEL */

        assert(!thr_act->lower);

#endif /* CALLOUT_RPC_MODEL */

        s = splsched();
        thread_lock(thread);
        thread->active = FALSE;
        thread_unlock(thread);
        splx(s);

        thread_timer_terminate();

        /* flush any lazy HW state while in own context */
        thread_machine_flush(thr_act);

        ipc_thread_terminate(thread);

        s = splsched();
        thread_lock(thread);
        thread->state |= (TH_HALTED|TH_TERMINATE);
        assert((thread->state & TH_UNINT) == 0);
        thread_mark_wait_locked(thread, THREAD_UNINT);
        thread_unlock(thread);
        /* splx(s); */

        ETAP_SET_REASON(thread, BLOCKED_ON_TERMINATION);
        thread_block((void (*)(void)) 0);
        panic("the zombie walks!");
        /*NOTREACHED*/
}


/*
 * Create a new thread.
 * Doesn't start the thread running; It first must be attached to
 * an activation - then use thread_go to start it.
 */
kern_return_t
thread_create_shuttle(
        thread_act_t                    thr_act,
        integer_t                               priority,
        void                                    (*start)(void),
        thread_t                                *new_thread)
{
        thread_t                                new_shuttle;
        task_t                                  parent_task = thr_act->task;
        processor_set_t                 pset;
        kern_return_t                   result;
        int                                             suspcnt;

        assert(!thr_act->thread);
        assert(!thr_act->pool_port);

        /*
         *      Allocate a thread and initialize static fields
         */
        new_shuttle = (thread_t)zalloc(thread_shuttle_zone);
        if (new_shuttle == THREAD_NULL)
                return (KERN_RESOURCE_SHORTAGE);

        *new_shuttle = thr_sh_template;

        thread_lock_init(new_shuttle);
        rpc_lock_init(new_shuttle);
        wake_lock_init(new_shuttle);
        new_shuttle->sleep_stamp = sched_tick;

        /*
         *      Thread still isn't runnable yet (our caller will do
         *      that).  Initialize runtime-dependent fields here.
         */
        result = thread_machine_create(new_shuttle, thr_act, thread_continue);
        assert (result == KERN_SUCCESS);

        thread_start(new_shuttle, start);
        thread_timer_setup(new_shuttle);
        ipc_thread_init(new_shuttle);

        pset = parent_task->processor_set;
        if (!pset->active) {
                pset = &default_pset;
        }
        pset_lock(pset);

        task_lock(parent_task);

        /*
         *      Don't need to initialize because the context switch
         *      code will set it before it can be used.
         */
        if (!parent_task->active) {
                task_unlock(parent_task);
                pset_unlock(pset);
                thread_machine_destroy(new_shuttle);
                zfree(thread_shuttle_zone, (vm_offset_t) new_shuttle);
                return (KERN_FAILURE);
        }

        act_attach(thr_act, new_shuttle, 0);

        /* Chain the thr_act onto the task's list */
        queue_enter(&parent_task->thr_acts, thr_act, thread_act_t, thr_acts);
        parent_task->thr_act_count++;
        parent_task->res_act_count++;
        parent_task->active_act_count++;

        /* Associate the thread with the processor set */
        pset_add_thread(pset, new_shuttle);

        /* Set the thread's scheduling parameters */
        if (parent_task != kernel_task)
                new_shuttle->sched_mode |= TH_MODE_TIMESHARE;
        new_shuttle->max_priority = parent_task->max_priority;
        new_shuttle->task_priority = parent_task->priority;
        new_shuttle->priority = (priority < 0)? parent_task->priority: priority;
        if (new_shuttle->priority > new_shuttle->max_priority)
                new_shuttle->priority = new_shuttle->max_priority;
        new_shuttle->importance =
                                        new_shuttle->priority - new_shuttle->task_priority;
        new_shuttle->sched_stamp = sched_tick;
        compute_priority(new_shuttle, TRUE);

#if     ETAP_EVENT_MONITOR
        new_thread->etap_reason = 0;
        new_thread->etap_trace  = FALSE;
#endif  /* ETAP_EVENT_MONITOR */

        new_shuttle->active = TRUE;
        thr_act->active = TRUE;
        pset_unlock(pset);

        /*
         * No need to lock thr_act, since it can't be known to anyone --
         * we set its suspend_count to one more than the task suspend_count
         * by calling thread_hold.
         */
        thr_act->user_stop_count = 1;
        for (suspcnt = thr_act->task->suspend_count + 1; suspcnt; --suspcnt)
                thread_hold(thr_act);
        task_unlock(parent_task);

        *new_thread = new_shuttle;

        {
          long dbg_arg1, dbg_arg2, dbg_arg3, dbg_arg4;

          KERNEL_DEBUG_CONSTANT((TRACEDBG_CODE(DBG_TRACE_DATA, 1)) | DBG_FUNC_NONE,
                                (vm_address_t)new_shuttle, 0,0,0,0);

          kdbg_trace_string(parent_task->bsd_info, &dbg_arg1, &dbg_arg2, &dbg_arg3, 
                            &dbg_arg4);
          KERNEL_DEBUG_CONSTANT((TRACEDBG_CODE(DBG_TRACE_STRING, 1)) | DBG_FUNC_NONE,
                                dbg_arg1, dbg_arg2, dbg_arg3, dbg_arg4, 0);
        }

        return (KERN_SUCCESS);
}

kern_return_t
thread_create(
        task_t                          task,
        thread_act_t            *new_act)
{
        thread_act_t            thr_act;
        thread_t                        thread;
        kern_return_t           result;
        spl_t                           s;
        extern void                     thread_bootstrap_return(void);

        if (task == TASK_NULL)
                return KERN_INVALID_ARGUMENT;

        result = act_create(task, &thr_act);
        if (result != KERN_SUCCESS)
                return (result);

        result = thread_create_shuttle(thr_act, -1, thread_bootstrap_return, &thread);
        if (result != KERN_SUCCESS) {
                act_deallocate(thr_act);
                return (result);
        }

        if (task->kernel_loaded)
                thread_user_to_kernel(thread);

        /* Start the thread running (it will immediately suspend itself).  */
        s = splsched();
        thread_ast_set(thr_act, AST_APC);
        thread_lock(thread);
        thread_go_locked(thread, THREAD_AWAKENED);
        thread_unlock(thread);
        splx(s);
        
        *new_act = thr_act;

        return (KERN_SUCCESS);
}

/*
 * Update thread that belongs to a task created via kernel_task_create().
 */
void
thread_user_to_kernel(
        thread_t                thread)
{
        /*
         * Used to set special swap_func here...
         */
}

kern_return_t
thread_create_running(
        register task_t         parent_task,
        int                     flavor,
        thread_state_t          new_state,
        mach_msg_type_number_t  new_state_count,
        thread_act_t                    *child_act)             /* OUT */
{
        register kern_return_t  result;

        result = thread_create(parent_task, child_act);
        if (result != KERN_SUCCESS)
                return (result);

        result = act_machine_set_state(*child_act, flavor,
                                       new_state, new_state_count);
        if (result != KERN_SUCCESS) {
                (void) thread_terminate(*child_act);
                return (result);
        }

        result = thread_resume(*child_act);
        if (result != KERN_SUCCESS) {
                (void) thread_terminate(*child_act);
                return (result);
        }

        return (result);
}

/*
 *      kernel_thread:
 *
 *      Create and kernel thread in the specified task, and
 *      optionally start it running.
 */
thread_t
kernel_thread_with_priority(
        task_t                          task,
        integer_t                       priority,
        void                            (*start)(void),
        boolean_t                       alloc_stack,
        boolean_t                       start_running)
{
        kern_return_t           result;
        thread_t                        thread;
        thread_act_t            thr_act;
        spl_t                           s;

        result = act_create(task, &thr_act);
        if (result != KERN_SUCCESS) {
                return THREAD_NULL;
        }

        result = thread_create_shuttle(thr_act, priority, start, &thread);
        if (result != KERN_SUCCESS) {
                act_deallocate(thr_act);
                return THREAD_NULL;
        }

        if (alloc_stack)
                thread_doswapin(thread);

        s = splsched();
        thread_lock(thread);

        thr_act = thread->top_act;
#if     MACH_LDEBUG
        thread->kthread = TRUE;
#endif  /* MACH_LDEBUG */

        if (start_running)
                thread_go_locked(thread, THREAD_AWAKENED);

        thread_unlock(thread);
        splx(s);

        if (start_running)
                thread_resume(thr_act);

        act_deallocate(thr_act);
        return (thread);
}

thread_t
kernel_thread(
        task_t                  task,
        void                    (*start)(void))
{
        return kernel_thread_with_priority(task, -1, start, FALSE, TRUE);
}

unsigned int c_weird_pset_ref_exit = 0; /* pset code raced us */

void
thread_deallocate(
        thread_t                        thread)
{
        task_t                          task;
        processor_set_t         pset;
        spl_t                           s;

        if (thread == THREAD_NULL)
                return;

        /*
         *      First, check for new count > 1 (the common case).
         *      Only the thread needs to be locked.
         */
        s = splsched();
        thread_lock(thread);
        if (--thread->ref_count > 1) {
                thread_unlock(thread);
                splx(s);
                return;
        }

        /*
         *      Down to pset reference, lets try to clean up.
         *      However, the processor set may make more. Its lock
         *      also dominate the thread lock.  So, reverse the
         *      order of the locks and see if its still the last
         *      reference;
         */
        assert(thread->ref_count == 1); /* Else this is an extra dealloc! */
        thread_unlock(thread);
        splx(s);

#if     MACH_HOST
        thread_freeze(thread);
#endif  /* MACH_HOST */

        pset = thread->processor_set;
        pset_lock(pset);

        s = splsched();
        thread_lock(thread);

        if (thread->ref_count > 1) {
#if     MACH_HOST
                boolean_t need_wakeup = FALSE;
                /*
                 *      processor_set made extra reference.
                 */
                /* Inline the unfreeze */
                thread->may_assign = TRUE;
                if (thread->assign_active) {
                        need_wakeup = TRUE;
                        thread->assign_active = FALSE;
                }
#endif  /* MACH_HOST */
                thread_unlock(thread);
                splx(s);
                pset_unlock(pset);
#if     MACH_HOST
                if (need_wakeup)
                        thread_wakeup((event_t)&thread->assign_active);
#endif  /* MACH_HOST */
                c_weird_pset_ref_exit++;
                return;
        }
#if     MACH_HOST
        assert(thread->assign_active == FALSE);
#endif  /* MACH_HOST */

        /*
         *      Thread only had pset reference - we can remove it.
         */
        if (thread == current_thread())
            panic("thread deallocating itself");

        pset_remove_thread(pset, thread);
        thread->ref_count = 0;
        thread_unlock(thread);          /* no more references - safe */
        splx(s);
        pset_unlock(pset);

        pset_deallocate(thread->processor_set);

        if (thread->stack_privilege != 0) {
                if (thread->stack_privilege != thread->kernel_stack)
                        stack_free_stack(thread->stack_privilege);
                thread->stack_privilege = 0;
        }
        /* frees kernel stack & other MD resources */
        thread_machine_destroy(thread);

        zfree(thread_shuttle_zone, (vm_offset_t) thread);
}

void
thread_reference(
        thread_t        thread)
{
        spl_t           s;

        if (thread == THREAD_NULL)
                return;

        s = splsched();
        thread_lock(thread);
        thread->ref_count++;
        thread_unlock(thread);
        splx(s);
}

/*
 * Called with "appropriate" thread-related locks held on
 * thread and its top_act for synchrony with RPC (see
 * act_lock_thread()).
 */
kern_return_t
thread_info_shuttle(
        register thread_act_t   thr_act,
        thread_flavor_t                 flavor,
        thread_info_t                   thread_info_out,        /* ptr to OUT array */
        mach_msg_type_number_t  *thread_info_count)     /*IN/OUT*/
{
        register thread_t               thread = thr_act->thread;
        int                                             state, flags;
        spl_t                                   s;

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

        if (flavor == THREAD_BASIC_INFO) {
            register thread_basic_info_t        basic_info;

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

            basic_info = (thread_basic_info_t) thread_info_out;

            s = splsched();
            thread_lock(thread);

            /* 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 (thread->sched_stamp != sched_tick)
                        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 = (thread->cpu_usage << SCHED_TICK_SHIFT) /
                                                                                                (TIMER_RATE / TH_USAGE_SCALE);
                basic_info->cpu_usage = (basic_info->cpu_usage * 3) / 5;
#if     SIMPLE_CLOCK
                /*
                 *      Clock drift compensation.
                 */
                basic_info->cpu_usage = (basic_info->cpu_usage * 1000000) / sched_usec;
#endif  /* SIMPLE_CLOCK */

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

            flags = 0;
                if (thread->state & TH_IDLE)
                        flags |= TH_FLAGS_IDLE;

            if (thread->state & TH_STACK_HANDOFF)
                        flags |= TH_FLAGS_SWAPPED;

            state = 0;
            if (thread->state & TH_HALTED)
                        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 = thr_act->user_stop_count;

            thread_unlock(thread);
            splx(s);

            *thread_info_count = THREAD_BASIC_INFO_COUNT;

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

                ts_info->depressed = (thread->depress_priority >= 0);
                ts_info->depress_priority = thread->depress_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;

                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->base_priority = thread->priority;
                rr_info->max_priority = thread->max_priority;
            rr_info->quantum = std_quantum_us / 1000;

                rr_info->depressed = (thread->depress_priority >= 0);
                rr_info->depress_priority = thread->depress_priority;

                thread_unlock(thread);
            splx(s);

                *thread_info_count = POLICY_RR_INFO_COUNT;

                return (KERN_SUCCESS);  
        }

        return (KERN_INVALID_ARGUMENT);
}

void
thread_doreap(
        register thread_t       thread)
{
        thread_act_t            thr_act;
        struct ipc_port         *pool_port;


        thr_act = thread_lock_act(thread);
        assert(thr_act && thr_act->thread == thread);

        act_locked_act_reference(thr_act);
        pool_port = thr_act->pool_port;

        /*
         * Replace `act_unlock_thread()' with individual
         * calls.  (`act_detach()' can change fields used
         * to determine which locks are held, confusing
         * `act_unlock_thread()'.)
         */
        rpc_unlock(thread);
        if (pool_port != IP_NULL)
                ip_unlock(pool_port);
        act_unlock(thr_act);

        /* Remove the reference held by a rooted thread */
        if (pool_port == IP_NULL)
                act_deallocate(thr_act);

        /* Remove the reference held by the thread: */
        act_deallocate(thr_act);
}

static thread_call_data_t       thread_reaper_call_data;

/*
 *      reaper_thread:
 *
 *      This kernel thread runs forever looking for threads to destroy
 *      (when they request that they be destroyed, of course).
 *
 *      The reaper thread will disappear in the next revision of thread
 *      control when it's function will be moved into thread_dispatch.
 */
static void
_thread_reaper(
        thread_call_param_t             p0,
        thread_call_param_t             p1)
{
        register thread_t       thread;
        spl_t                           s;

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

        while ((thread = (thread_t) dequeue_head(&reaper_queue)) != THREAD_NULL) {
                simple_unlock(&reaper_lock);

                /*
                 * wait for run bit to clear
                 */
                thread_lock(thread);
                if (thread->state & TH_RUN)
                        panic("thread reaper: TH_RUN");
                thread_unlock(thread);
                splx(s);

                thread_doreap(thread);

                s = splsched();
                simple_lock(&reaper_lock);
        }

        simple_unlock(&reaper_lock);
        splx(s);
}

void
thread_reaper(void)
{
        thread_call_setup(&thread_reaper_call_data,     _thread_reaper, NULL);
        thread_reaper_call = &thread_reaper_call_data;

        _thread_reaper(NULL, NULL);
}

kern_return_t
thread_assign(
        thread_act_t    thr_act,
        processor_set_t new_pset)
{
#ifdef  lint
        thread++; new_pset++;
#endif  /* lint */
        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_act_t    thr_act)
{
        return (thread_assign(thr_act, &default_pset));
}

/*
 *      thread_get_assignment
 *
 *      Return current assignment for this thread.
 */         
kern_return_t
thread_get_assignment(
        thread_act_t    thr_act,
        processor_set_t *pset)
{
        thread_t        thread;

        if (thr_act == THR_ACT_NULL)
                return(KERN_INVALID_ARGUMENT);
        thread = act_lock_thread(thr_act);
        if (thread == THREAD_NULL) {
                act_unlock_thread(thr_act);
                return(KERN_INVALID_ARGUMENT);
        }
        *pset = thread->processor_set;
        act_unlock_thread(thr_act);
        pset_reference(*pset);
        return(KERN_SUCCESS);
}

/*
 *      thread_wire:
 *
 *      Specify that the target thread must always be able
 *      to run and to allocate memory.
 */
kern_return_t
thread_wire(
        host_priv_t     host_priv,
        thread_act_t    thr_act,
        boolean_t       wired)
{
        spl_t           s;
        thread_t        thread;
        extern void vm_page_free_reserve(int pages);

        if (thr_act == THR_ACT_NULL || host_priv == HOST_PRIV_NULL)
                return (KERN_INVALID_ARGUMENT);

        assert(host_priv == &realhost);

        thread = act_lock_thread(thr_act);
        if (thread ==THREAD_NULL) {
                act_unlock_thread(thr_act);
                return(KERN_INVALID_ARGUMENT);
        }

        /*
         * This implementation only works for the current thread.
         * See stack_privilege.
         */
        if (thr_act != current_act())
            return KERN_INVALID_ARGUMENT;

        s = splsched();
        thread_lock(thread);

        if (wired) {
            if (thread->vm_privilege == FALSE) 
                    vm_page_free_reserve(1);    /* XXX */
            thread->vm_privilege = TRUE;
        } else {
            if (thread->vm_privilege == TRUE) 
                    vm_page_free_reserve(-1);   /* XXX */
            thread->vm_privilege = FALSE;
        }

        thread_unlock(thread);
        splx(s);
        act_unlock_thread(thr_act);

        return KERN_SUCCESS;
}

/*
 *      thread_collect_scan:
 *
 *      Attempt to free resources owned by threads.
 */

void
thread_collect_scan(void)
{
        /* This code runs very quickly! */
}

/* Also disabled in vm/vm_pageout.c */
boolean_t thread_collect_allowed = FALSE;
unsigned thread_collect_last_tick = 0;
unsigned thread_collect_max_rate = 0;           /* in ticks */

/*
 *      consider_thread_collect:
 *
 *      Called by the pageout daemon when the system needs more free pages.
 */

void
consider_thread_collect(void)
{
        /*
         *      By default, don't attempt thread collection more frequently
         *      than once a second.
         */

        if (thread_collect_max_rate == 0)
                thread_collect_max_rate = (1 << SCHED_TICK_SHIFT) + 1;

        if (thread_collect_allowed &&
            (sched_tick >
             (thread_collect_last_tick + thread_collect_max_rate))) {
                thread_collect_last_tick = sched_tick;
                thread_collect_scan();
        }
}

kern_return_t
host_stack_usage(
        host_t          host,
        vm_size_t       *reservedp,
        unsigned int    *totalp,
        vm_size_t       *spacep,
        vm_size_t       *residentp,
        vm_size_t       *maxusagep,
        vm_offset_t     *maxstackp)
{
#if !MACH_DEBUG
        return KERN_NOT_SUPPORTED;
#else
        unsigned int total;
        vm_size_t maxusage;

        if (host == HOST_NULL)
                return KERN_INVALID_HOST;

        maxusage = 0;

        stack_statistics(&total, &maxusage);

        *reservedp = 0;
        *totalp = total;
        *spacep = *residentp = total * round_page(KERNEL_STACK_SIZE);
        *maxusagep = maxusage;
        *maxstackp = 0;
        return KERN_SUCCESS;

#endif /* MACH_DEBUG */
}

/*
 * Return info on stack usage for threads in a specific processor set
 */
kern_return_t
processor_set_stack_usage(
        processor_set_t pset,
        unsigned int    *totalp,
        vm_size_t       *spacep,
        vm_size_t       *residentp,
        vm_size_t       *maxusagep,
        vm_offset_t     *maxstackp)
{
#if !MACH_DEBUG
        return KERN_NOT_SUPPORTED;
#else
        unsigned int total;
        vm_size_t maxusage;
        vm_offset_t maxstack;

        register thread_t *threads;
        register thread_t thread;

        unsigned int actual;    /* this many things */
        unsigned int i;

        vm_size_t size, size_needed;
        vm_offset_t addr;

        if (pset == PROCESSOR_SET_NULL)
                return KERN_INVALID_ARGUMENT;

        size = 0; addr = 0;

        for (;;) {
                pset_lock(pset);
                if (!pset->active) {
                        pset_unlock(pset);
                        return KERN_INVALID_ARGUMENT;
                }

                actual = pset->thread_count;

                /* do we have the memory we need? */

                size_needed = actual * sizeof(thread_t);
                if (size_needed <= size)
                        break;

                /* unlock the pset and allocate more memory */
                pset_unlock(pset);

                if (size != 0)
                        kfree(addr, size);

                assert(size_needed > 0);
                size = size_needed;

                addr = kalloc(size);
                if (addr == 0)
                        return KERN_RESOURCE_SHORTAGE;
        }

        /* OK, have memory and the processor_set is locked & active */

        threads = (thread_t *) addr;
        for (i = 0, thread = (thread_t) queue_first(&pset->threads);
             i < actual;
             i++,
             thread = (thread_t) queue_next(&thread->pset_threads)) {
                thread_reference(thread);
                threads[i] = thread;
        }
        assert(queue_end(&pset->threads, (queue_entry_t) thread));

        /* can unlock processor set now that we have the thread refs */
        pset_unlock(pset);

        /* calculate maxusage and free thread references */

        total = 0;
        maxusage = 0;
        maxstack = 0;
        for (i = 0; i < actual; i++) {
                int cpu;
                thread_t thread = threads[i];
                vm_offset_t stack = 0;

                /*
                 *      thread->kernel_stack is only accurate if the
                 *      thread isn't swapped and is not executing.
                 *
                 *      Of course, we don't have the appropriate locks
                 *      for these shenanigans.
                 */

                stack = thread->kernel_stack;

                for (cpu = 0; cpu < NCPUS; cpu++)
                        if (cpu_data[cpu].active_thread == thread) {
                                stack = active_stacks[cpu];
                                break;
                        }

                if (stack != 0) {
                        total++;
                }

                thread_deallocate(thread);
        }

        if (size != 0)
                kfree(addr, size);

        *totalp = total;
        *residentp = *spacep = total * round_page(KERNEL_STACK_SIZE);
        *maxusagep = maxusage;
        *maxstackp = maxstack;
        return KERN_SUCCESS;

#endif  /* MACH_DEBUG */
}

static int split_funnel_off = 0;
funnel_t *
funnel_alloc(
        int type)
{
        mutex_t *m;
        funnel_t * fnl;
        if ((fnl = (funnel_t *)kalloc(sizeof(funnel_t))) != 0){
                bzero((void *)fnl, sizeof(funnel_t));
                if ((m = mutex_alloc(0)) == (mutex_t *)NULL) {
                        kfree((vm_offset_t)fnl, sizeof(funnel_t));
                        return(THR_FUNNEL_NULL);
                }
                fnl->fnl_mutex = m;
                fnl->fnl_type = type;
        }
        return(fnl);
}

void 
funnel_free(
        funnel_t * fnl)
{
        mutex_free(fnl->fnl_mutex);
        if (fnl->fnl_oldmutex)
                mutex_free(fnl->fnl_oldmutex);
        kfree((vm_offset_t)fnl, sizeof(funnel_t));
}

void 
funnel_lock(
        funnel_t * fnl)
{
        mutex_t * m;

        m = fnl->fnl_mutex;
restart:
        mutex_lock(m);
        fnl->fnl_mtxholder = current_thread();
        if (split_funnel_off && (m != fnl->fnl_mutex)) {
                mutex_unlock(m);
                m = fnl->fnl_mutex;     
                goto restart;
        }
}

void 
funnel_unlock(
        funnel_t * fnl)
{
        mutex_unlock(fnl->fnl_mutex);
        fnl->fnl_mtxrelease = current_thread();
}

funnel_t *
thread_funnel_get(
        void)
{
        thread_t th = current_thread();

        if (th->funnel_state & TH_FN_OWNED) {
                return(th->funnel_lock);
        }
        return(THR_FUNNEL_NULL);
}

boolean_t
thread_funnel_set(
        funnel_t *      fnl,
        boolean_t       funneled)
{
        thread_t        cur_thread;
        boolean_t       funnel_state_prev;
        boolean_t       intr;
        
        cur_thread = current_thread();
        funnel_state_prev = ((cur_thread->funnel_state & TH_FN_OWNED) == TH_FN_OWNED);

        if (funnel_state_prev != funneled) {
                intr = ml_set_interrupts_enabled(FALSE);

                if (funneled == TRUE) {
                        if (cur_thread->funnel_lock)
                                panic("Funnel lock called when holding one %x", cur_thread->funnel_lock);
                        KERNEL_DEBUG(0x6032428 | DBG_FUNC_NONE,
                                                                                        fnl, 1, 0, 0, 0);
                        funnel_lock(fnl);
                        KERNEL_DEBUG(0x6032434 | DBG_FUNC_NONE,
                                                                                        fnl, 1, 0, 0, 0);
                        cur_thread->funnel_state |= TH_FN_OWNED;
                        cur_thread->funnel_lock = fnl;
                } else {
                        if(cur_thread->funnel_lock->fnl_mutex != fnl->fnl_mutex)
                                panic("Funnel unlock  when not holding funnel");
                        cur_thread->funnel_state &= ~TH_FN_OWNED;
                        KERNEL_DEBUG(0x603242c | DBG_FUNC_NONE,
                                                                fnl, 1, 0, 0, 0);

                        cur_thread->funnel_lock = THR_FUNNEL_NULL;
                        funnel_unlock(fnl);
                }
                (void)ml_set_interrupts_enabled(intr);
        } else {
                /* if we are trying to acquire funnel recursively
                 * check for funnel to be held already
                 */
                if (funneled && (fnl->fnl_mutex != cur_thread->funnel_lock->fnl_mutex)) {
                                panic("thread_funnel_set: already holding a different funnel");
                }
        }
        return(funnel_state_prev);
}

boolean_t
thread_funnel_merge(
        funnel_t * fnl,
        funnel_t * otherfnl)
{
        mutex_t * m;
        mutex_t * otherm;
        funnel_t * gfnl;
        extern int disable_funnel;

        if ((gfnl = thread_funnel_get()) == THR_FUNNEL_NULL)
                panic("thread_funnel_merge called with no funnels held");

        if (gfnl->fnl_type != 1)
                panic("thread_funnel_merge called from non kernel funnel");

        if (gfnl != fnl)
                panic("thread_funnel_merge incorrect invocation");

        if (disable_funnel || split_funnel_off)
                return (KERN_FAILURE);

        m = fnl->fnl_mutex;
        otherm = otherfnl->fnl_mutex;

        /* Acquire other funnel mutex */
        mutex_lock(otherm);
        split_funnel_off = 1;
        disable_funnel = 1;
        otherfnl->fnl_mutex = m;
        otherfnl->fnl_type = fnl->fnl_type;
        otherfnl->fnl_oldmutex = otherm;        /* save this for future use */

        mutex_unlock(otherm);
        return(KERN_SUCCESS);
}

void
thread_set_cont_arg(
        int                             arg)
{
        thread_t                self = current_thread();

        self->saved.misc = arg; 
}

int
thread_get_cont_arg(void)
{
        thread_t                self = current_thread();

        return (self->saved.misc); 
}

/*
 * Export routines to other components for things that are done as macros
 * within the osfmk component.
 */
#undef thread_should_halt
boolean_t
thread_should_halt(
        thread_shuttle_t th)
{
        return(thread_should_halt_fast(th));
}