path: root/kern/task.c

/*
 * Mach Operating System
 * Copyright (c) 1993-1988 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/task.c
 *	Author:	Avadis Tevanian, Jr., Michael Wayne Young, David Golub,
 *		David Black
 *
 *	Task management primitives implementation.
 */

#include <string.h>

#include <mach/machine/vm_types.h>
#include <mach/vm_param.h>
#include <mach/task_info.h>
#include <mach/task_special_ports.h>
#include <mach_debug/mach_debug_types.h>
#include <ipc/ipc_space.h>
#include <ipc/ipc_types.h>
#include <kern/debug.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/slab.h>
#include <kern/kalloc.h>
#include <kern/processor.h>
#include <kern/printf.h>
#include <kern/sched_prim.h>	/* for thread_wakeup */
#include <kern/ipc_tt.h>
#include <kern/syscall_emulation.h>
#include <kern/task_notify.user.h>
#include <vm/vm_kern.h>		/* for kernel_map, ipc_kernel_map */
#include <machine/machspl.h>	/* for splsched */

task_t	kernel_task = TASK_NULL;
struct kmem_cache task_cache;

/* Where to send notifications about newly created tasks.  */
ipc_port_t new_task_notification = NULL;

void task_init(void)
{
	kmem_cache_init(&task_cache, "task", sizeof(struct task), 0,
			NULL, NULL, NULL, 0);

	eml_init();
	machine_task_module_init ();

	/*
	 * Create the kernel task as the first task.
	 * Task_create must assign to kernel_task as a side effect,
	 * for other initialization. (:-()
	 */
	(void) task_create(TASK_NULL, FALSE, &kernel_task);
	(void) task_set_name(kernel_task, "gnumach");
}

kern_return_t task_create(
	task_t		parent_task,
	boolean_t	inherit_memory,
	task_t		*child_task)		/* OUT */
{
	task_t		new_task;
	processor_set_t	pset;
#if FAST_TAS
	int i;
#endif

	new_task = (task_t) kmem_cache_alloc(&task_cache);
	if (new_task == TASK_NULL)
		return KERN_RESOURCE_SHORTAGE;

	/* one ref for just being alive; one for our caller */
	new_task->ref_count = 2;

	if (child_task == &kernel_task)  {
		new_task->map = kernel_map;
	} else if (inherit_memory) {
		new_task->map = vm_map_fork(parent_task->map);
	} else {
		new_task->map = vm_map_create(pmap_create(0),
					round_page(VM_MIN_ADDRESS),
					trunc_page(VM_MAX_ADDRESS), TRUE);
	}

	simple_lock_init(&new_task->lock);
	queue_init(&new_task->thread_list);
	new_task->suspend_count = 0;
	new_task->active = TRUE;
	new_task->user_stop_count = 0;
	new_task->thread_count = 0;
	new_task->faults = 0;
	new_task->zero_fills = 0;
	new_task->reactivations = 0;
	new_task->pageins = 0;
	new_task->cow_faults = 0;
	new_task->messages_sent = 0;
	new_task->messages_received = 0;

	eml_task_reference(new_task, parent_task);

	ipc_task_init(new_task, parent_task);
	machine_task_init (new_task);

	new_task->total_user_time.seconds = 0;
	new_task->total_user_time.microseconds = 0;
	new_task->total_system_time.seconds = 0;
	new_task->total_system_time.microseconds = 0;

	record_time_stamp (&new_task->creation_time);

	if (parent_task != TASK_NULL) {
		task_lock(parent_task);
		pset = parent_task->processor_set;
		if (!pset->active)
			pset = &default_pset;
		pset_reference(pset);
		new_task->priority = parent_task->priority;
		task_unlock(parent_task);
	}
	else {
		pset = &default_pset;
		pset_reference(pset);
		new_task->priority = BASEPRI_USER;
	}
	pset_lock(pset);
	pset_add_task(pset, new_task);
	pset_unlock(pset);

	new_task->may_assign = TRUE;
	new_task->assign_active = FALSE;

#if	MACH_PCSAMPLE
	new_task->pc_sample.buffer = 0;
	new_task->pc_sample.seqno = 0;
	new_task->pc_sample.sampletypes = 0;
#endif	/* MACH_PCSAMPLE */

#if	FAST_TAS
	for (i = 0; i < TASK_FAST_TAS_NRAS; i++)  {
	    if (inherit_memory) {
		new_task->fast_tas_base[i] = parent_task->fast_tas_base[i];
 		new_task->fast_tas_end[i]  = parent_task->fast_tas_end[i];
	    } else {
 		new_task->fast_tas_base[i] = (vm_offset_t)0;
 		new_task->fast_tas_end[i]  = (vm_offset_t)0;
	    }
	}
#endif	/* FAST_TAS */

	if (parent_task == TASK_NULL)
		snprintf (new_task->name, sizeof new_task->name, "%p",
			  new_task);
	else
		snprintf (new_task->name, sizeof new_task->name, "(%.*s)",
			  sizeof new_task->name - 3, parent_task->name);

	if (new_task_notification != NULL) {
		task_reference (new_task);
		task_reference (parent_task);
		mach_notify_new_task (new_task_notification,
				      convert_task_to_port (new_task),
				      convert_task_to_port (parent_task));
	}

	ipc_task_enable(new_task);

	*child_task = new_task;
	return KERN_SUCCESS;
}

/*
 *	task_deallocate:
 *
 *	Give up a reference to the specified task and destroy it if there
 *	are no other references left.  It is assumed that the current thread
 *	is never in this task.
 */
void task_deallocate(
	task_t	task)
{
	int c;
	processor_set_t pset;

	if (task == TASK_NULL)
		return;

	task_lock(task);
	c = --(task->ref_count);
	task_unlock(task);
	if (c != 0)
		return;

	machine_task_terminate (task);

	eml_task_deallocate(task);

	pset = task->processor_set;
	pset_lock(pset);
	pset_remove_task(pset,task);
	pset_unlock(pset);
	pset_deallocate(pset);
	vm_map_deallocate(task->map);
	is_release(task->itk_space);
	kmem_cache_free(&task_cache, (vm_offset_t) task);
}

void task_reference(
	task_t	task)
{
	if (task == TASK_NULL)
		return;

	task_lock(task);
	task->ref_count++;
	task_unlock(task);
}

/*
 *	task_terminate:
 *
 *	Terminate the specified task.  See comments on thread_terminate
 *	(kern/thread.c) about problems with terminating the "current task."
 */
kern_return_t task_terminate(
	task_t	task)
{
	thread_t		thread, cur_thread;
	queue_head_t		*list;
	task_t			cur_task;
	spl_t			s;

	if (task == TASK_NULL)
		return KERN_INVALID_ARGUMENT;

	list = &task->thread_list;
	cur_task = current_task();
	cur_thread = current_thread();

	/*
	 *	Deactivate task so that it can't be terminated again,
	 *	and so lengthy operations in progress will abort.
	 *
	 *	If the current thread is in this task, remove it from
	 *	the task's thread list to keep the thread-termination
	 *	loop simple.
	 */
	if (task == cur_task) {
		task_lock(task);
		if (!task->active) {
			/*
			 *	Task is already being terminated.
			 */
			task_unlock(task);
			return KERN_FAILURE;
		}
		/*
		 *	Make sure current thread is not being terminated.
		 */
		s = splsched();
		thread_lock(cur_thread);
		if (!cur_thread->active) {
			thread_unlock(cur_thread);
			(void) splx(s);
			task_unlock(task);
			thread_terminate(cur_thread);
			return KERN_FAILURE;
		}
		task_hold_locked(task);
		task->active = FALSE;
		queue_remove(list, cur_thread, thread_t, thread_list);
		thread_unlock(cur_thread);
		(void) splx(s);
		task_unlock(task);

		/*
		 *	Shut down this thread's ipc now because it must
		 *	be left alone to terminate the task.
		 */
		ipc_thread_disable(cur_thread);
		ipc_thread_terminate(cur_thread);
	}
	else {
		/*
		 *	Lock both current and victim task to check for
		 *	potential deadlock.
		 */
		if ((vm_offset_t)task < (vm_offset_t)cur_task) {
			task_lock(task);
			task_lock(cur_task);
		}
		else {
			task_lock(cur_task);
			task_lock(task);
		}
		/*
		 *	Check if current thread or task is being terminated.
		 */
		s = splsched();
		thread_lock(cur_thread);
		if ((!cur_task->active) ||(!cur_thread->active)) {
			/*
			 * Current task or thread is being terminated.
			 */
			thread_unlock(cur_thread);
			(void) splx(s);
			task_unlock(task);
			task_unlock(cur_task);
			thread_terminate(cur_thread);
			return KERN_FAILURE;
		}
		thread_unlock(cur_thread);
		(void) splx(s);
		task_unlock(cur_task);

		if (!task->active) {
			/*
			 *	Task is already being terminated.
			 */
			task_unlock(task);
			return KERN_FAILURE;
		}
		task_hold_locked(task);
		task->active = FALSE;
		task_unlock(task);
	}

	/*
	 *	Prevent further execution of the task.  ipc_task_disable
	 *	prevents further task operations via the task port.
	 *	If this is the current task, the current thread will
	 *	be left running.
	 */
	(void) task_dowait(task,TRUE);			/* may block */
	ipc_task_disable(task);

	/*
	 *	Terminate each thread in the task.
	 *
         *      The task_port is closed down, so no more thread_create
         *      operations can be done.  Thread_force_terminate closes the
         *      thread port for each thread; when that is done, the
         *      thread will eventually disappear.  Thus the loop will
         *      terminate.  Call thread_force_terminate instead of
         *      thread_terminate to avoid deadlock checks.  Need
         *      to call thread_block() inside loop because some other
         *      thread (e.g., the reaper) may have to run to get rid
         *      of all references to the thread; it won't vanish from
         *      the task's thread list until the last one is gone.
         */
        task_lock(task);
        while (!queue_empty(list)) {
                thread = (thread_t) queue_first(list);
                thread_reference(thread);
                task_unlock(task);
                thread_force_terminate(thread);
                thread_deallocate(thread);
                thread_block((void (*)()) 0);
                task_lock(task);
        }
        task_unlock(task);

	/*
	 *	Shut down IPC.
	 */
	ipc_task_terminate(task);


	/*
	 *	Deallocate the task's reference to itself.
	 */
	task_deallocate(task);

	/*
	 *	If the current thread is in this task, it has not yet
	 *	been terminated (since it was removed from the task's
	 *	thread-list).  Put it back in the thread list (for
	 *	completeness), and terminate it.  Since it holds the
	 *	last reference to the task, terminating it will deallocate
	 *	the task.
	 */
	if (cur_thread->task == task) {
		task_lock(task);
		s = splsched();
		queue_enter(list, cur_thread, thread_t, thread_list);
		(void) splx(s);
		task_unlock(task);
		(void) thread_terminate(cur_thread);
	}

	return KERN_SUCCESS;
}

/*
 *	task_hold:
 *
 *	Suspend execution of the specified task.
 *	This is a recursive-style suspension of the task, a count of
 *	suspends is maintained.
 *
 *	CONDITIONS: the task is locked and active.
 */
void task_hold_locked(
	task_t	task)
{
	queue_head_t	*list;
	thread_t	thread, cur_thread;

	assert(task->active);

	cur_thread = current_thread();

	task->suspend_count++;

	/*
	 *	Iterate through all the threads and hold them.
	 *	Do not hold the current thread if it is within the
	 *	task.
	 */
	list = &task->thread_list;
	queue_iterate(list, thread, thread_t, thread_list) {
		if (thread != cur_thread)
			thread_hold(thread);
	}
}

/*
 *	task_hold:
 *
 *	Suspend execution of the specified task.
 *	This is a recursive-style suspension of the task, a count of
 *	suspends is maintained.
 */
kern_return_t task_hold(
	task_t	task)
{
	task_lock(task);
	if (!task->active) {
		task_unlock(task);
		return KERN_FAILURE;
	}

	task_hold_locked(task);

	task_unlock(task);
	return KERN_SUCCESS;
}

/*
 *	task_dowait:
 *
 *	Wait until the task has really been suspended (all of the threads
 *	are stopped).  Skip the current thread if it is within the task.
 *
 *	If task is deactivated while waiting, return a failure code unless
 *	must_wait is true.
 */
kern_return_t task_dowait(
	task_t	task,
	boolean_t must_wait)
{
	queue_head_t	*list;
	thread_t	thread, cur_thread, prev_thread;
	kern_return_t	ret = KERN_SUCCESS;

	/*
	 *	Iterate through all the threads.
	 *	While waiting for each thread, we gain a reference to it
	 *	to prevent it from going away on us.  This guarantees
	 *	that the "next" thread in the list will be a valid thread.
	 *
	 *	We depend on the fact that if threads are created while
	 *	we are looping through the threads, they will be held
	 *	automatically.  We don't care about threads that get
	 *	deallocated along the way (the reference prevents it
	 *	from happening to the thread we are working with).
	 *
	 *	If the current thread is in the affected task, it is skipped.
	 *
	 *	If the task is deactivated before we're done, and we don't
	 *	have to wait for it (must_wait is FALSE), just bail out.
	 */
	cur_thread = current_thread();

	list = &task->thread_list;
	prev_thread = THREAD_NULL;
	task_lock(task);
	queue_iterate(list, thread, thread_t, thread_list) {
		if (!(task->active) && !(must_wait)) {
			ret = KERN_FAILURE;
			break;
		}
		if (thread != cur_thread) {
			thread_reference(thread);
			task_unlock(task);
			if (prev_thread != THREAD_NULL)
				thread_deallocate(prev_thread);
							/* may block */
			(void) thread_dowait(thread, TRUE);  /* may block */
			prev_thread = thread;
			task_lock(task);
		}
	}
	task_unlock(task);
	if (prev_thread != THREAD_NULL)
		thread_deallocate(prev_thread);		/* may block */
	return ret;
}

kern_return_t task_release(
	task_t	task)
{
	queue_head_t	*list;
	thread_t	thread, next;

	task_lock(task);
	if (!task->active) {
		task_unlock(task);
		return KERN_FAILURE;
	}

	task->suspend_count--;

	/*
	 *	Iterate through all the threads and release them
	 */
	list = &task->thread_list;
	thread = (thread_t) queue_first(list);
	while (!queue_end(list, (queue_entry_t) thread)) {
		next = (thread_t) queue_next(&thread->thread_list);
		thread_release(thread);
		thread = next;
	}
	task_unlock(task);
	return KERN_SUCCESS;
}

kern_return_t task_threads(
	task_t		task,
	thread_array_t	*thread_list,
	natural_t	*count)
{
	unsigned int actual;	/* this many threads */
	thread_t thread;
	thread_t *threads;
	int i;

	vm_size_t size, size_needed;
	vm_offset_t addr;

	if (task == TASK_NULL)
		return KERN_INVALID_ARGUMENT;

	size = 0; addr = 0;

	for (;;) {
		task_lock(task);
		if (!task->active) {
			task_unlock(task);
			return KERN_FAILURE;
		}

		actual = task->thread_count;

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

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

		/* unlock the task and allocate more memory */
		task_unlock(task);

		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 task is locked & active */

	threads = (thread_t *) addr;

	for (i = 0, thread = (thread_t) queue_first(&task->thread_list);
	     i < actual;
	     i++, thread = (thread_t) queue_next(&thread->thread_list)) {
		/* take ref for convert_thread_to_port */
		thread_reference(thread);
		threads[i] = thread;
	}
	assert(queue_end(&task->thread_list, (queue_entry_t) thread));

	/* can unlock task now that we've got the thread refs */
	task_unlock(task);

	if (actual == 0) {
		/* no threads, so return null pointer and deallocate memory */

		*thread_list = 0;
		*count = 0;

		if (size != 0)
			kfree(addr, size);
	} else {
		/* if we allocated too much, must copy */

		if (size_needed < size) {
			vm_offset_t newaddr;

			newaddr = kalloc(size_needed);
			if (newaddr == 0) {
				for (i = 0; i < actual; i++)
					thread_deallocate(threads[i]);
				kfree(addr, size);
				return KERN_RESOURCE_SHORTAGE;
			}

			memcpy((void *) newaddr, (void *) addr, size_needed);
			kfree(addr, size);
			threads = (thread_t *) newaddr;
		}

		*thread_list = (mach_port_t *) threads;
		*count = actual;

		/* do the conversion that Mig should handle */

		for (i = 0; i < actual; i++)
			((ipc_port_t *) threads)[i] =
				convert_thread_to_port(threads[i]);
	}

	return KERN_SUCCESS;
}

kern_return_t task_suspend(
	task_t	task)
{
	boolean_t	hold;

	if (task == TASK_NULL)
		return KERN_INVALID_ARGUMENT;

	hold = FALSE;
	task_lock(task);
	if ((task->user_stop_count)++ == 0)
		hold = TRUE;
	task_unlock(task);

	/*
	 *	If the stop count was positive, the task is
	 *	already stopped and we can exit.
	 */
	if (!hold) {
		return KERN_SUCCESS;
	}

	/*
	 *	Hold all of the threads in the task, and wait for
	 *	them to stop.  If the current thread is within
	 *	this task, hold it separately so that all of the
	 *	other threads can stop first.
	 */

	if (task_hold(task) != KERN_SUCCESS)
		return KERN_FAILURE;

	if (task_dowait(task, FALSE) != KERN_SUCCESS)
		return KERN_FAILURE;

	if (current_task() == task) {
		spl_t s;

		thread_hold(current_thread());
		/*
		 *	We want to call thread_block on our way out,
		 *	to stop running.
		 */
		s = splsched();
		ast_on(cpu_number(), AST_BLOCK);
		(void) splx(s);
	}

	return KERN_SUCCESS;
}

kern_return_t task_resume(
	task_t	task)
{
	boolean_t	release;

	if (task == TASK_NULL)
		return KERN_INVALID_ARGUMENT;

	release = FALSE;
	task_lock(task);
	if (task->user_stop_count > 0) {
		if (--(task->user_stop_count) == 0)
	    		release = TRUE;
	}
	else {
		task_unlock(task);
		return KERN_FAILURE;
	}
	task_unlock(task);

	/*
	 *	Release the task if necessary.
	 */
	if (release)
		return task_release(task);

	return KERN_SUCCESS;
}

kern_return_t task_info(
	task_t			task,
	int			flavor,
	task_info_t		task_info_out,	/* pointer to OUT array */
	natural_t		*task_info_count)	/* IN/OUT */
{
	vm_map_t		map;

	if (task == TASK_NULL)
		return KERN_INVALID_ARGUMENT;

	switch (flavor) {
	    case TASK_BASIC_INFO:
	    {
		task_basic_info_t	basic_info;

		/* Allow *task_info_count to be two words smaller than
		   the usual amount, because creation_time is a new member
		   that some callers might not know about. */

		if (*task_info_count < TASK_BASIC_INFO_COUNT - 2) {
		    return KERN_INVALID_ARGUMENT;
		}

		basic_info = (task_basic_info_t) task_info_out;

		map = (task == kernel_task) ? kernel_map : task->map;

		basic_info->virtual_size  = map->size;
		basic_info->resident_size = pmap_resident_count(map->pmap)
						   * PAGE_SIZE;

		task_lock(task);
		basic_info->base_priority = task->priority;
		basic_info->suspend_count = task->user_stop_count;
		basic_info->user_time.seconds
				= task->total_user_time.seconds;
		basic_info->user_time.microseconds
				= task->total_user_time.microseconds;
		basic_info->system_time.seconds
				= task->total_system_time.seconds;
		basic_info->system_time.microseconds
				= task->total_system_time.microseconds;
		basic_info->creation_time = task->creation_time;
		task_unlock(task);

		if (*task_info_count > TASK_BASIC_INFO_COUNT)
		  *task_info_count = TASK_BASIC_INFO_COUNT;
		break;
	    }

	    case TASK_EVENTS_INFO:
	    {
		task_events_info_t	event_info;

		if (*task_info_count < TASK_EVENTS_INFO_COUNT) {
		    return KERN_INVALID_ARGUMENT;
		}

		event_info = (task_events_info_t) task_info_out;

		task_lock(task);
		event_info->faults = task->faults;
		event_info->zero_fills = task->zero_fills;
		event_info->reactivations = task->reactivations;
		event_info->pageins = task->pageins;
		event_info->cow_faults = task->cow_faults;
		event_info->messages_sent = task->messages_sent;
		event_info->messages_received = task->messages_received;
		task_unlock(task);

		*task_info_count = TASK_EVENTS_INFO_COUNT;
		break;
	    }

	    case TASK_THREAD_TIMES_INFO:
	    {
		task_thread_times_info_t times_info;
		thread_t	thread;

		if (*task_info_count < TASK_THREAD_TIMES_INFO_COUNT) {
		    return KERN_INVALID_ARGUMENT;
		}

		times_info = (task_thread_times_info_t) task_info_out;
		times_info->user_time.seconds = 0;
		times_info->user_time.microseconds = 0;
		times_info->system_time.seconds = 0;
		times_info->system_time.microseconds = 0;

		task_lock(task);
		queue_iterate(&task->thread_list, thread,
			      thread_t, thread_list)
		{
		    time_value_t user_time, system_time;
		    spl_t		 s;

		    s = splsched();
		    thread_lock(thread);

		    thread_read_times(thread, &user_time, &system_time);

		    thread_unlock(thread);
		    splx(s);

		    time_value_add(&times_info->user_time, &user_time);
		    time_value_add(&times_info->system_time, &system_time);
		}
		task_unlock(task);

		*task_info_count = TASK_THREAD_TIMES_INFO_COUNT;
		break;
	    }

	    default:
		return KERN_INVALID_ARGUMENT;
	}

	return KERN_SUCCESS;
}

#if	MACH_HOST
/*
 *	task_assign:
 *
 *	Change the assigned processor set for the task
 */
kern_return_t
task_assign(
	task_t		task,
	processor_set_t	new_pset,
	boolean_t	assign_threads)
{
	kern_return_t		ret = KERN_SUCCESS;
	thread_t	thread, prev_thread;
	queue_head_t	*list;
	processor_set_t	pset;

	if (task == TASK_NULL || new_pset == PROCESSOR_SET_NULL) {
		return KERN_INVALID_ARGUMENT;
	}

	/*
	 *	Freeze task`s assignment.  Prelude to assigning
	 *	task.  Only one freeze may be held per task.
	 */

	task_lock(task);
	while (task->may_assign == FALSE) {
		task->assign_active = TRUE;
		assert_wait((event_t)&task->assign_active, TRUE);
		task_unlock(task);
		thread_block((void (*)()) 0);
		task_lock(task);
	}

	/*
	 *	Avoid work if task already in this processor set.
	 */
	if (task->processor_set == new_pset)  {
		/*
		 *	No need for task->assign_active wakeup:
		 *	task->may_assign is still TRUE.
		 */
		task_unlock(task);
		return KERN_SUCCESS;
	}

	task->may_assign = FALSE;
	task_unlock(task);

	/*
	 *	Safe to get the task`s pset: it cannot change while
	 *	task is frozen.
	 */
	pset = task->processor_set;

	/*
	 *	Lock both psets now.  Use ordering to avoid deadlock.
	 */
    Restart:
	if ((vm_offset_t) pset < (vm_offset_t) new_pset) {
	    pset_lock(pset);
	    pset_lock(new_pset);
	}
	else {
	    pset_lock(new_pset);
	    pset_lock(pset);
	}

	/*
	 *	Check if new_pset is ok to assign to.  If not,
	 *	reassign to default_pset.
	 */
	if (!new_pset->active) {
	    pset_unlock(pset);
	    pset_unlock(new_pset);
	    new_pset = &default_pset;
	    goto Restart;
	}

	pset_reference(new_pset);

	/*
	 *	Now grab the task lock and move the task.
	 */

	task_lock(task);
	pset_remove_task(pset, task);
	pset_add_task(new_pset, task);

	pset_unlock(pset);
	pset_unlock(new_pset);

	if (assign_threads == FALSE) {
		/*
		 *	We leave existing threads at their
		 *	old assignments.  Unfreeze task`s
		 *	assignment.
		 */
		task->may_assign = TRUE;
		if (task->assign_active) {
			task->assign_active = FALSE;
			thread_wakeup((event_t) &task->assign_active);
		}
		task_unlock(task);
		pset_deallocate(pset);
		return KERN_SUCCESS;
	}

	/*
	 *	If current thread is in task, freeze its assignment.
	 */
	if (current_thread()->task == task) {
		task_unlock(task);
		thread_freeze(current_thread());
		task_lock(task);
	}

	/*
	 *	Iterate down the thread list reassigning all the threads.
	 *	New threads pick up task's new processor set automatically.
	 *	Do current thread last because new pset may be empty.
	 */
	list = &task->thread_list;
	prev_thread = THREAD_NULL;
	queue_iterate(list, thread, thread_t, thread_list) {
		if (!(task->active)) {
			ret = KERN_FAILURE;
			break;
		}
		if (thread != current_thread()) {
			thread_reference(thread);
			task_unlock(task);
			if (prev_thread != THREAD_NULL)
			    thread_deallocate(prev_thread); /* may block */
			thread_assign(thread,new_pset);	    /* may block */
			prev_thread = thread;
			task_lock(task);
		}
	}

	/*
	 *	Done, wakeup anyone waiting for us.
	 */
	task->may_assign = TRUE;
	if (task->assign_active) {
		task->assign_active = FALSE;
		thread_wakeup((event_t)&task->assign_active);
	}
	task_unlock(task);
	if (prev_thread != THREAD_NULL)
		thread_deallocate(prev_thread);		/* may block */

	/*
	 *	Finish assignment of current thread.
	 */
	if (current_thread()->task == task)
		thread_doassign(current_thread(), new_pset, TRUE);

	pset_deallocate(pset);

	return ret;
}
#else	/* MACH_HOST */
/*
 *	task_assign:
 *
 *	Change the assigned processor set for the task
 */
kern_return_t
task_assign(
	task_t		task,
	processor_set_t	new_pset,
	boolean_t	assign_threads)
{
	return KERN_FAILURE;
}
#endif	/* MACH_HOST */


/*
 *	task_assign_default:
 *
 *	Version of task_assign to assign to default processor set.
 */
kern_return_t
task_assign_default(
	task_t		task,
	boolean_t	assign_threads)
{
	return task_assign(task, &default_pset, assign_threads);
}

/*
 *	task_get_assignment
 *
 *	Return name of processor set that task is assigned to.
 */
kern_return_t task_get_assignment(
	task_t		task,
	processor_set_t	*pset)
{
	if (!task->active)
		return KERN_FAILURE;

	*pset = task->processor_set;
	pset_reference(*pset);
	return KERN_SUCCESS;
}

/*
 *	task_priority
 *
 *	Set priority of task; used only for newly created threads.
 *	Optionally change priorities of threads.
 */
kern_return_t
task_priority(
	task_t		task,
	int		priority,
	boolean_t	change_threads)
{
	kern_return_t	ret = KERN_SUCCESS;

	if (task == TASK_NULL || invalid_pri(priority))
		return KERN_INVALID_ARGUMENT;

	task_lock(task);
	task->priority = priority;

	if (change_threads) {
		thread_t	thread;
		queue_head_t	*list;

		list = &task->thread_list;
		queue_iterate(list, thread, thread_t, thread_list) {
			if (thread_priority(thread, priority, FALSE)
				!= KERN_SUCCESS)
					ret = KERN_FAILURE;
		}
	}

	task_unlock(task);
	return ret;
}

/*
 *	task_set_name
 *
 *	Set the name of task TASK to NAME.  This is a debugging aid.
 *	NAME will be used in error messages printed by the kernel.
 */
kern_return_t
task_set_name(
	task_t			task,
	kernel_debug_name_t	name)
{
	strncpy(task->name, name, sizeof task->name - 1);
	task->name[sizeof task->name - 1] = '\0';
	return KERN_SUCCESS;
}

/*
 *	task_collect_scan:
 *
 *	Attempt to free resources owned by tasks.
 */

void task_collect_scan(void)
{
	task_t			task, prev_task;
	processor_set_t		pset, prev_pset;

	prev_task = TASK_NULL;
	prev_pset = PROCESSOR_SET_NULL;

	simple_lock(&all_psets_lock);
	queue_iterate(&all_psets, pset, processor_set_t, all_psets) {
		pset_lock(pset);
		queue_iterate(&pset->tasks, task, task_t, pset_tasks) {
			task_reference(task);
			pset_reference(pset);
			pset_unlock(pset);
			simple_unlock(&all_psets_lock);

			machine_task_collect (task);
			pmap_collect(task->map->pmap);

			if (prev_task != TASK_NULL)
				task_deallocate(prev_task);
			prev_task = task;

			if (prev_pset != PROCESSOR_SET_NULL)
				pset_deallocate(prev_pset);
			prev_pset = pset;

			simple_lock(&all_psets_lock);
			pset_lock(pset);
		}
		pset_unlock(pset);
	}
	simple_unlock(&all_psets_lock);

	if (prev_task != TASK_NULL)
		task_deallocate(prev_task);
	if (prev_pset != PROCESSOR_SET_NULL)
		pset_deallocate(prev_pset);
}

boolean_t task_collect_allowed = TRUE;
unsigned task_collect_last_tick = 0;
unsigned task_collect_max_rate = 0;		/* in ticks */

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

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

	if (task_collect_max_rate == 0)
		task_collect_max_rate = hz;

	if (task_collect_allowed &&
	    (sched_tick > (task_collect_last_tick + task_collect_max_rate))) {
		task_collect_last_tick = sched_tick;
		task_collect_scan();
	}
}

kern_return_t
task_ras_control(
 	task_t task,
 	vm_offset_t pc,
 	vm_offset_t endpc,
	int flavor)
{
    kern_return_t ret = KERN_FAILURE;

#if	FAST_TAS
    int i;

    ret = KERN_SUCCESS;
    task_lock(task);
    switch (flavor)  {
    case TASK_RAS_CONTROL_PURGE_ALL:  /* remove all RAS */
	for (i = 0; i < TASK_FAST_TAS_NRAS; i++) {
	    task->fast_tas_base[i] = task->fast_tas_end[i] = 0;
	}
	break;
    case TASK_RAS_CONTROL_PURGE_ONE:  /* remove this RAS, collapse remaining */
	for (i = 0; i < TASK_FAST_TAS_NRAS; i++)  {
	    if ( (task->fast_tas_base[i] == pc)
		&& (task->fast_tas_end[i] == endpc))  {
			while (i < TASK_FAST_TAS_NRAS-1)  {
	    		  task->fast_tas_base[i] = task->fast_tas_base[i+1];
	    		  task->fast_tas_end[i] = task->fast_tas_end[i+1];
			  i++;
			 }
	    		task->fast_tas_base[TASK_FAST_TAS_NRAS-1] = 0;
	    		task->fast_tas_end[TASK_FAST_TAS_NRAS-1] = 0;
			break;
	     }
	}
	if (i == TASK_FAST_TAS_NRAS) {
	    ret = KERN_INVALID_ADDRESS;
	}
	break;
    case TASK_RAS_CONTROL_PURGE_ALL_AND_INSTALL_ONE:
	/* remove all RAS an install this RAS */
	for (i = 0; i < TASK_FAST_TAS_NRAS; i++) {
	    task->fast_tas_base[i] = task->fast_tas_end[i] = 0;
	}
	/* FALL THROUGH */
    case TASK_RAS_CONTROL_INSTALL_ONE: /* install this RAS */
	for (i = 0; i < TASK_FAST_TAS_NRAS; i++)  {
	    if ( (task->fast_tas_base[i] == pc)
	    && (task->fast_tas_end[i] == endpc))   {
		/* already installed */
		break;
	    }
	    if ((task->fast_tas_base[i] == 0) && (task->fast_tas_end[i] == 0)){
		task->fast_tas_base[i] = pc;
		task->fast_tas_end[i] = endpc;
		break;
	    }
	}
	if (i == TASK_FAST_TAS_NRAS)  {
	    ret = KERN_RESOURCE_SHORTAGE;
	}
	break;
    default: ret = KERN_INVALID_VALUE;
	break;
    }
    task_unlock(task);
#endif /* FAST_TAS */
    return ret;
}

/*
 *	register_new_task_notification
 *
 *	Register a port to which a notification about newly created
 *	tasks are sent.
 */
kern_return_t
register_new_task_notification(
	const host_t host,
	ipc_port_t notification)
{
	if (host == HOST_NULL)
		return KERN_INVALID_HOST;

	if (new_task_notification != NULL)
		return KERN_NO_ACCESS;

	new_task_notification = notification;
	return KERN_SUCCESS;
}