thread_policy.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@
 */

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

#include <kern/kern_types.h>
#include <kern/processor.h>
#include <kern/thread.h>
#include <kern/affinity.h>
#include <mach/task_policy.h>
#include <kern/sfi.h>
#include <kern/policy_internal.h>
#include <sys/errno.h>
#include <sys/ulock.h>

#include <mach/machine/sdt.h>

static KALLOC_TYPE_DEFINE(thread_qos_override_zone,
    struct thread_qos_override, KT_DEFAULT);

#ifdef MACH_BSD
extern int      proc_selfpid(void);
extern char *   proc_name_address(void *p);
extern void     rethrottle_thread(void * uthread);
#endif /* MACH_BSD */

#define QOS_EXTRACT(q)        ((q) & 0xff)

#define QOS_OVERRIDE_MODE_OVERHANG_PEAK 0
#define QOS_OVERRIDE_MODE_IGNORE_OVERRIDE 1
#define QOS_OVERRIDE_MODE_FINE_GRAINED_OVERRIDE 2
#define QOS_OVERRIDE_MODE_FINE_GRAINED_OVERRIDE_BUT_SINGLE_MUTEX_OVERRIDE 3

TUNABLE(uint32_t, qos_override_mode, "qos_override_mode",
    QOS_OVERRIDE_MODE_FINE_GRAINED_OVERRIDE_BUT_SINGLE_MUTEX_OVERRIDE);

static void
proc_thread_qos_remove_override_internal(thread_t thread, user_addr_t resource, int resource_type, boolean_t reset);

/*
 * THREAD_QOS_UNSPECIFIED is assigned the highest tier available, so it does not provide a limit
 * to threads that don't have a QoS class set.
 */
const qos_policy_params_t thread_qos_policy_params = {
	/*
	 * This table defines the starting base priority of the thread,
	 * which will be modified by the thread importance and the task max priority
	 * before being applied.
	 */
	.qos_pri[THREAD_QOS_UNSPECIFIED]                = 0, /* not consulted */
	.qos_pri[THREAD_QOS_USER_INTERACTIVE]           = BASEPRI_BACKGROUND, /* i.e. 46 */
	.qos_pri[THREAD_QOS_USER_INITIATED]             = BASEPRI_USER_INITIATED,
	.qos_pri[THREAD_QOS_LEGACY]                     = BASEPRI_DEFAULT,
	.qos_pri[THREAD_QOS_UTILITY]                    = BASEPRI_UTILITY,
	.qos_pri[THREAD_QOS_BACKGROUND]                 = MAXPRI_THROTTLE,
	.qos_pri[THREAD_QOS_MAINTENANCE]                = MAXPRI_THROTTLE,

	/*
	 * This table defines the highest IO priority that a thread marked with this
	 * QoS class can have.
	 */
	.qos_iotier[THREAD_QOS_UNSPECIFIED]             = THROTTLE_LEVEL_TIER0,
	.qos_iotier[THREAD_QOS_USER_INTERACTIVE]        = THROTTLE_LEVEL_TIER0,
	.qos_iotier[THREAD_QOS_USER_INITIATED]          = THROTTLE_LEVEL_TIER0,
	.qos_iotier[THREAD_QOS_LEGACY]                  = THROTTLE_LEVEL_TIER0,
	.qos_iotier[THREAD_QOS_UTILITY]                 = THROTTLE_LEVEL_TIER1,
	.qos_iotier[THREAD_QOS_BACKGROUND]              = THROTTLE_LEVEL_TIER2, /* possibly overridden by bg_iotier */
	.qos_iotier[THREAD_QOS_MAINTENANCE]             = THROTTLE_LEVEL_TIER3,

	/*
	 * This table defines the highest QoS level that
	 * a thread marked with this QoS class can have.
	 */

	.qos_through_qos[THREAD_QOS_UNSPECIFIED]        = QOS_EXTRACT(THROUGHPUT_QOS_TIER_UNSPECIFIED),
	.qos_through_qos[THREAD_QOS_USER_INTERACTIVE]   = QOS_EXTRACT(THROUGHPUT_QOS_TIER_0),
	.qos_through_qos[THREAD_QOS_USER_INITIATED]     = QOS_EXTRACT(THROUGHPUT_QOS_TIER_1),
	.qos_through_qos[THREAD_QOS_LEGACY]             = QOS_EXTRACT(THROUGHPUT_QOS_TIER_1),
	.qos_through_qos[THREAD_QOS_UTILITY]            = QOS_EXTRACT(THROUGHPUT_QOS_TIER_2),
	.qos_through_qos[THREAD_QOS_BACKGROUND]         = QOS_EXTRACT(THROUGHPUT_QOS_TIER_5),
	.qos_through_qos[THREAD_QOS_MAINTENANCE]        = QOS_EXTRACT(THROUGHPUT_QOS_TIER_5),

	.qos_latency_qos[THREAD_QOS_UNSPECIFIED]        = QOS_EXTRACT(LATENCY_QOS_TIER_UNSPECIFIED),
	.qos_latency_qos[THREAD_QOS_USER_INTERACTIVE]   = QOS_EXTRACT(LATENCY_QOS_TIER_0),
	.qos_latency_qos[THREAD_QOS_USER_INITIATED]     = QOS_EXTRACT(LATENCY_QOS_TIER_1),
	.qos_latency_qos[THREAD_QOS_LEGACY]             = QOS_EXTRACT(LATENCY_QOS_TIER_1),
	.qos_latency_qos[THREAD_QOS_UTILITY]            = QOS_EXTRACT(LATENCY_QOS_TIER_3),
	.qos_latency_qos[THREAD_QOS_BACKGROUND]         = QOS_EXTRACT(LATENCY_QOS_TIER_3),
	.qos_latency_qos[THREAD_QOS_MAINTENANCE]        = QOS_EXTRACT(LATENCY_QOS_TIER_3),
};

static void
thread_set_user_sched_mode_and_recompute_pri(thread_t thread, sched_mode_t mode);

static int
thread_qos_scaled_relative_priority(int qos, int qos_relprio);

static void
proc_get_thread_policy_bitfield(thread_t thread, thread_policy_state_t info);

static void
proc_set_thread_policy_locked(thread_t thread, int category, int flavor, int value, int value2, task_pend_token_t pend_token);

static void
proc_set_thread_policy_spinlocked(thread_t thread, int category, int flavor, int value, int value2, task_pend_token_t pend_token);

static void
thread_set_requested_policy_spinlocked(thread_t thread, int category, int flavor, int value, int value2, task_pend_token_t pend_token);

static int
thread_get_requested_policy_spinlocked(thread_t thread, int category, int flavor, int* value2);

static int
proc_get_thread_policy_locked(thread_t thread, int category, int flavor, int* value2);

static void
thread_policy_update_spinlocked(thread_t thread, bool recompute_priority, task_pend_token_t pend_token);

static void
thread_policy_update_internal_spinlocked(thread_t thread, bool recompute_priority, task_pend_token_t pend_token);

boolean_t
thread_has_qos_policy(thread_t thread)
{
	return (proc_get_thread_policy(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS) != THREAD_QOS_UNSPECIFIED) ? TRUE : FALSE;
}


static void
thread_remove_qos_policy_locked(thread_t thread,
    task_pend_token_t pend_token)
{
	__unused int prev_qos = thread->requested_policy.thrp_qos;

	DTRACE_PROC2(qos__remove, thread_t, thread, int, prev_qos);

	proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_AND_RELPRIO,
	    THREAD_QOS_UNSPECIFIED, 0, pend_token);
}

kern_return_t
thread_remove_qos_policy(thread_t thread)
{
	struct task_pend_token pend_token = {};

	thread_mtx_lock(thread);
	if (!thread->active) {
		thread_mtx_unlock(thread);
		return KERN_TERMINATED;
	}

	thread_remove_qos_policy_locked(thread, &pend_token);

	thread_mtx_unlock(thread);

	thread_policy_update_complete_unlocked(thread, &pend_token);

	return KERN_SUCCESS;
}


boolean_t
thread_is_static_param(thread_t thread)
{
	if (thread->static_param) {
		DTRACE_PROC1(qos__legacy__denied, thread_t, thread);
		return TRUE;
	}
	return FALSE;
}

/*
 * Relative priorities can range between 0REL and -15REL. These
 * map to QoS-specific ranges, to create non-overlapping priority
 * ranges.
 */
static int
thread_qos_scaled_relative_priority(int qos, int qos_relprio)
{
	int next_lower_qos;

	/* Fast path, since no validation or scaling is needed */
	if (qos_relprio == 0) {
		return 0;
	}

	switch (qos) {
	case THREAD_QOS_USER_INTERACTIVE:
		next_lower_qos = THREAD_QOS_USER_INITIATED;
		break;
	case THREAD_QOS_USER_INITIATED:
		next_lower_qos = THREAD_QOS_LEGACY;
		break;
	case THREAD_QOS_LEGACY:
		next_lower_qos = THREAD_QOS_UTILITY;
		break;
	case THREAD_QOS_UTILITY:
		next_lower_qos = THREAD_QOS_BACKGROUND;
		break;
	case THREAD_QOS_MAINTENANCE:
	case THREAD_QOS_BACKGROUND:
		next_lower_qos = 0;
		break;
	default:
		panic("Unrecognized QoS %d", qos);
		return 0;
	}

	int prio_range_max = thread_qos_policy_params.qos_pri[qos];
	int prio_range_min = next_lower_qos ? thread_qos_policy_params.qos_pri[next_lower_qos] : 0;

	/*
	 * We now have the valid range that the scaled relative priority can map to. Note
	 * that the lower bound is exclusive, but the upper bound is inclusive. If the
	 * range is (21,31], 0REL should map to 31 and -15REL should map to 22. We use the
	 * fact that the max relative priority is -15 and use ">>4" to divide by 16 and discard
	 * remainder.
	 */
	int scaled_relprio = -(((prio_range_max - prio_range_min) * (-qos_relprio)) >> 4);

	return scaled_relprio;
}

/*
 * flag set by -qos-policy-allow boot-arg to allow
 * testing thread qos policy from userspace
 */
static TUNABLE(bool, allow_qos_policy_set, "-qos-policy-allow", false);

kern_return_t
thread_policy_set(
	thread_t                                thread,
	thread_policy_flavor_t  flavor,
	thread_policy_t                 policy_info,
	mach_msg_type_number_t  count)
{
	thread_qos_policy_data_t req_qos;
	kern_return_t kr;

	req_qos.qos_tier = THREAD_QOS_UNSPECIFIED;

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

	if (!allow_qos_policy_set) {
		if (thread_is_static_param(thread)) {
			return KERN_POLICY_STATIC;
		}

		if (flavor == THREAD_QOS_POLICY) {
			return KERN_INVALID_ARGUMENT;
		}

		if (flavor == THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY) {
			if (count < THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY_COUNT) {
				return KERN_INVALID_ARGUMENT;
			}
			thread_time_constraint_with_priority_policy_t info = (thread_time_constraint_with_priority_policy_t)policy_info;
			if (info->priority != BASEPRI_RTQUEUES) {
				return KERN_INVALID_ARGUMENT;
			}
		}
	}

	/* Threads without static_param set reset their QoS when other policies are applied. */
	if (thread->requested_policy.thrp_qos != THREAD_QOS_UNSPECIFIED) {
		/* Store the existing tier, if we fail this call it is used to reset back. */
		req_qos.qos_tier = thread->requested_policy.thrp_qos;
		req_qos.tier_importance = thread->requested_policy.thrp_qos_relprio;

		kr = thread_remove_qos_policy(thread);
		if (kr != KERN_SUCCESS) {
			return kr;
		}
	}

	kr = thread_policy_set_internal(thread, flavor, policy_info, count);

	/* Return KERN_QOS_REMOVED instead of KERN_SUCCESS if we succeeded. */
	if (req_qos.qos_tier != THREAD_QOS_UNSPECIFIED) {
		if (kr != KERN_SUCCESS) {
			/* Reset back to our original tier as the set failed. */
			(void)thread_policy_set_internal(thread, THREAD_QOS_POLICY, (thread_policy_t)&req_qos, THREAD_QOS_POLICY_COUNT);
		}
	}

	return kr;
}

static_assert(offsetof(thread_time_constraint_with_priority_policy_data_t, period) == offsetof(thread_time_constraint_policy_data_t, period));
static_assert(offsetof(thread_time_constraint_with_priority_policy_data_t, computation) == offsetof(thread_time_constraint_policy_data_t, computation));
static_assert(offsetof(thread_time_constraint_with_priority_policy_data_t, constraint) == offsetof(thread_time_constraint_policy_data_t, constraint));
static_assert(offsetof(thread_time_constraint_with_priority_policy_data_t, preemptible) == offsetof(thread_time_constraint_policy_data_t, preemptible));

kern_return_t
thread_policy_set_internal(
	thread_t                     thread,
	thread_policy_flavor_t       flavor,
	thread_policy_t              policy_info,
	mach_msg_type_number_t       count)
{
	kern_return_t result = KERN_SUCCESS;
	struct task_pend_token pend_token = {};

	thread_mtx_lock(thread);
	if (!thread->active) {
		thread_mtx_unlock(thread);

		return KERN_TERMINATED;
	}

	switch (flavor) {
	case THREAD_EXTENDED_POLICY:
	{
		boolean_t timeshare = TRUE;

		if (count >= THREAD_EXTENDED_POLICY_COUNT) {
			thread_extended_policy_t info;

			info = (thread_extended_policy_t)policy_info;
			timeshare = info->timeshare;
		}

		sched_mode_t mode = (timeshare == TRUE) ? TH_MODE_TIMESHARE : TH_MODE_FIXED;

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

		thread_set_user_sched_mode_and_recompute_pri(thread, mode);

		thread_unlock(thread);
		splx(s);

		pend_token.tpt_update_thread_sfi = 1;

		break;
	}

	case THREAD_TIME_CONSTRAINT_POLICY:
	case THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY:
	{
		thread_time_constraint_with_priority_policy_t info;

		mach_msg_type_number_t min_count = (flavor == THREAD_TIME_CONSTRAINT_POLICY ?
		    THREAD_TIME_CONSTRAINT_POLICY_COUNT :
		    THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY_COUNT);

		if (count < min_count) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		info = (thread_time_constraint_with_priority_policy_t)policy_info;


		if (info->constraint < info->computation ||
		    info->computation > max_rt_quantum ||
		    info->computation < min_rt_quantum) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if (info->computation < (info->constraint / 2)) {
			info->computation = (info->constraint / 2);
			if (info->computation > max_rt_quantum) {
				info->computation = max_rt_quantum;
			}
		}

		if (flavor == THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY) {
			if ((info->priority < BASEPRI_RTQUEUES) || (info->priority > MAXPRI)) {
				result = KERN_INVALID_ARGUMENT;
				break;
			}
		}

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

		thread->realtime.period          = info->period;
		thread->realtime.computation     = info->computation;
		thread->realtime.constraint      = info->constraint;
		thread->realtime.preemptible     = info->preemptible;
		if (flavor == THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY) {
			thread->realtime.priority_offset = (uint8_t)(info->priority - BASEPRI_RTQUEUES);
		} else {
			thread->realtime.priority_offset = 0;
			/* Or check for override from allowed thread group? */
		}

		thread_set_user_sched_mode_and_recompute_pri(thread, TH_MODE_REALTIME);

		thread_unlock(thread);
		splx(s);

		pend_token.tpt_update_thread_sfi = 1;

		break;
	}

	case THREAD_PRECEDENCE_POLICY:
	{
		thread_precedence_policy_t info;

		if (count < THREAD_PRECEDENCE_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}
		info = (thread_precedence_policy_t)policy_info;

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

		thread->importance = info->importance;

		thread_recompute_priority(thread);

		thread_unlock(thread);
		splx(s);

		break;
	}

	case THREAD_AFFINITY_POLICY:
	{
		thread_affinity_policy_t info;

		if (!thread_affinity_is_supported()) {
			result = KERN_NOT_SUPPORTED;
			break;
		}
		if (count < THREAD_AFFINITY_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		info = (thread_affinity_policy_t) policy_info;
		/*
		 * Unlock the thread mutex here and
		 * return directly after calling thread_affinity_set().
		 * This is necessary for correct lock ordering because
		 * thread_affinity_set() takes the task lock.
		 */
		thread_mtx_unlock(thread);
		return thread_affinity_set(thread, info->affinity_tag);
	}

#if !defined(XNU_TARGET_OS_OSX)
	case THREAD_BACKGROUND_POLICY:
	{
		thread_background_policy_t info;

		if (count < THREAD_BACKGROUND_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if (get_threadtask(thread) != current_task()) {
			result = KERN_PROTECTION_FAILURE;
			break;
		}

		info = (thread_background_policy_t) policy_info;

		int enable;

		if (info->priority == THREAD_BACKGROUND_POLICY_DARWIN_BG) {
			enable = TASK_POLICY_ENABLE;
		} else {
			enable = TASK_POLICY_DISABLE;
		}

		int category = (current_thread() == thread) ? TASK_POLICY_INTERNAL : TASK_POLICY_EXTERNAL;

		proc_set_thread_policy_locked(thread, category, TASK_POLICY_DARWIN_BG, enable, 0, &pend_token);

		break;
	}
#endif /* !defined(XNU_TARGET_OS_OSX) */

	case THREAD_THROUGHPUT_QOS_POLICY:
	{
		thread_throughput_qos_policy_t info = (thread_throughput_qos_policy_t) policy_info;
		thread_throughput_qos_t tqos;

		if (count < THREAD_THROUGHPUT_QOS_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if ((result = qos_throughput_policy_validate(info->thread_throughput_qos_tier)) != KERN_SUCCESS) {
			break;
		}

		tqos = qos_extract(info->thread_throughput_qos_tier);

		proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE,
		    TASK_POLICY_THROUGH_QOS, tqos, 0, &pend_token);

		break;
	}

	case THREAD_LATENCY_QOS_POLICY:
	{
		thread_latency_qos_policy_t info = (thread_latency_qos_policy_t) policy_info;
		thread_latency_qos_t lqos;

		if (count < THREAD_LATENCY_QOS_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if ((result = qos_latency_policy_validate(info->thread_latency_qos_tier)) != KERN_SUCCESS) {
			break;
		}

		lqos = qos_extract(info->thread_latency_qos_tier);

		proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE,
		    TASK_POLICY_LATENCY_QOS, lqos, 0, &pend_token);

		break;
	}

	case THREAD_QOS_POLICY:
	{
		thread_qos_policy_t info = (thread_qos_policy_t)policy_info;

		if (count < THREAD_QOS_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if (info->qos_tier < 0 || info->qos_tier >= THREAD_QOS_LAST) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if (info->tier_importance > 0 || info->tier_importance < THREAD_QOS_MIN_TIER_IMPORTANCE) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if (info->qos_tier == THREAD_QOS_UNSPECIFIED && info->tier_importance != 0) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_AND_RELPRIO,
		    info->qos_tier, -info->tier_importance, &pend_token);

		break;
	}

	default:
		result = KERN_INVALID_ARGUMENT;
		break;
	}

	thread_mtx_unlock(thread);

	thread_policy_update_complete_unlocked(thread, &pend_token);

	return result;
}

/*
 * Note that there is no implemented difference between POLICY_RR and POLICY_FIFO.
 * Both result in FIXED mode scheduling.
 */
static sched_mode_t
convert_policy_to_sched_mode(integer_t policy)
{
	switch (policy) {
	case POLICY_TIMESHARE:
		return TH_MODE_TIMESHARE;
	case POLICY_RR:
	case POLICY_FIFO:
		return TH_MODE_FIXED;
	default:
		panic("unexpected sched policy: %d", policy);
		return TH_MODE_NONE;
	}
}

/*
 * Called either with the thread mutex locked
 * or from the pthread kext in a 'safe place'.
 */
static kern_return_t
thread_set_mode_and_absolute_pri_internal(thread_t              thread,
    sched_mode_t          mode,
    integer_t             priority,
    task_pend_token_t     pend_token)
{
	kern_return_t kr = KERN_SUCCESS;

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

	/* This path isn't allowed to change a thread out of realtime. */
	if ((thread->sched_mode == TH_MODE_REALTIME) ||
	    (thread->saved_mode == TH_MODE_REALTIME)) {
		kr = KERN_FAILURE;
		goto unlock;
	}

	if (thread->policy_reset) {
		kr = KERN_SUCCESS;
		goto unlock;
	}

	sched_mode_t old_mode = thread->sched_mode;

	/*
	 * Reverse engineer and apply the correct importance value
	 * from the requested absolute priority value.
	 *
	 * TODO: Store the absolute priority value instead
	 */

	if (priority >= thread->max_priority) {
		priority = thread->max_priority - thread->task_priority;
	} else if (priority >= MINPRI_KERNEL) {
		priority -=  MINPRI_KERNEL;
	} else if (priority >= MINPRI_RESERVED) {
		priority -=  MINPRI_RESERVED;
	} else {
		priority -= BASEPRI_DEFAULT;
	}

	priority += thread->task_priority;

	if (priority > thread->max_priority) {
		priority = thread->max_priority;
	} else if (priority < MINPRI) {
		priority = MINPRI;
	}

	thread->importance = priority - thread->task_priority;

	thread_set_user_sched_mode_and_recompute_pri(thread, mode);

	if (mode != old_mode) {
		pend_token->tpt_update_thread_sfi = 1;
	}

unlock:
	thread_unlock(thread);
	splx(s);

	return kr;
}

void
thread_freeze_base_pri(thread_t thread)
{
	assert(thread == current_thread());

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

	assert((thread->sched_flags & TH_SFLAG_BASE_PRI_FROZEN) == 0);
	thread->sched_flags |= TH_SFLAG_BASE_PRI_FROZEN;

	thread_unlock(thread);
	splx(s);
}

bool
thread_unfreeze_base_pri(thread_t thread)
{
	assert(thread == current_thread());
	integer_t base_pri;
	ast_t ast = 0;

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

	assert(thread->sched_flags & TH_SFLAG_BASE_PRI_FROZEN);
	thread->sched_flags &= ~TH_SFLAG_BASE_PRI_FROZEN;

	base_pri = thread->req_base_pri;
	if (base_pri != thread->base_pri) {
		/*
		 * This function returns "true" if the base pri change
		 * is the most likely cause for the preemption.
		 */
		sched_set_thread_base_priority(thread, base_pri);
		ast = ast_peek(AST_PREEMPT);
	}

	thread_unlock(thread);
	splx(s);

	return ast != 0;
}

uint8_t
thread_workq_pri_for_qos(thread_qos_t qos)
{
	assert(qos < THREAD_QOS_LAST);
	return (uint8_t)thread_qos_policy_params.qos_pri[qos];
}

thread_qos_t
thread_workq_qos_for_pri(int priority)
{
	thread_qos_t qos;
	if (priority > thread_qos_policy_params.qos_pri[THREAD_QOS_USER_INTERACTIVE]) {
		// indicate that workq should map >UI threads to workq's
		// internal notation for above-UI work.
		return THREAD_QOS_UNSPECIFIED;
	}
	for (qos = THREAD_QOS_USER_INTERACTIVE; qos > THREAD_QOS_MAINTENANCE; qos--) {
		// map a given priority up to the next nearest qos band.
		if (thread_qos_policy_params.qos_pri[qos - 1] < priority) {
			return qos;
		}
	}
	return THREAD_QOS_MAINTENANCE;
}

/*
 * private interface for pthread workqueues
 *
 * Set scheduling policy & absolute priority for thread
 * May be called with spinlocks held
 * Thread mutex lock is not held
 */
void
thread_reset_workq_qos(thread_t thread, uint32_t qos)
{
	struct task_pend_token pend_token = {};

	assert(qos < THREAD_QOS_LAST);

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

	proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
	    TASK_POLICY_QOS_AND_RELPRIO, qos, 0, &pend_token);
	proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
	    TASK_POLICY_QOS_WORKQ_OVERRIDE, THREAD_QOS_UNSPECIFIED, 0,
	    &pend_token);

	assert(pend_token.tpt_update_sockets == 0);

	thread_unlock(thread);
	splx(s);

	thread_policy_update_complete_unlocked(thread, &pend_token);
}

/*
 * private interface for pthread workqueues
 *
 * Set scheduling policy & absolute priority for thread
 * May be called with spinlocks held
 * Thread mutex lock is held
 */
void
thread_set_workq_override(thread_t thread, uint32_t qos)
{
	struct task_pend_token pend_token = {};

	assert(qos < THREAD_QOS_LAST);

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

	proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
	    TASK_POLICY_QOS_WORKQ_OVERRIDE, qos, 0, &pend_token);

	assert(pend_token.tpt_update_sockets == 0);

	thread_unlock(thread);
	splx(s);

	thread_policy_update_complete_unlocked(thread, &pend_token);
}

/*
 * private interface for pthread workqueues
 *
 * Set scheduling policy & absolute priority for thread
 * May be called with spinlocks held
 * Thread mutex lock is not held
 */
void
thread_set_workq_pri(thread_t  thread,
    thread_qos_t qos,
    integer_t priority,
    integer_t policy)
{
	struct task_pend_token pend_token = {};
	sched_mode_t mode = convert_policy_to_sched_mode(policy);

	assert(qos < THREAD_QOS_LAST);
	assert(thread->static_param);

	if (!thread->static_param || !thread->active) {
		return;
	}

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

	proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
	    TASK_POLICY_QOS_AND_RELPRIO, qos, 0, &pend_token);
	proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
	    TASK_POLICY_QOS_WORKQ_OVERRIDE, THREAD_QOS_UNSPECIFIED,
	    0, &pend_token);

	thread_unlock(thread);
	splx(s);

	/* Concern: this doesn't hold the mutex... */

	__assert_only kern_return_t kr;
	kr = thread_set_mode_and_absolute_pri_internal(thread, mode, priority,
	    &pend_token);
	assert(kr == KERN_SUCCESS);

	if (pend_token.tpt_update_thread_sfi) {
		sfi_reevaluate(thread);
	}
}

/*
 * thread_set_mode_and_absolute_pri:
 *
 * Set scheduling policy & absolute priority for thread, for deprecated
 * thread_set_policy and thread_policy interfaces.
 *
 * Called with nothing locked.
 */
kern_return_t
thread_set_mode_and_absolute_pri(thread_t   thread,
    integer_t  policy,
    integer_t  priority)
{
	kern_return_t kr = KERN_SUCCESS;
	struct task_pend_token pend_token = {};

	sched_mode_t mode = convert_policy_to_sched_mode(policy);

	thread_mtx_lock(thread);

	if (!thread->active) {
		kr = KERN_TERMINATED;
		goto unlock;
	}

	if (thread_is_static_param(thread)) {
		kr = KERN_POLICY_STATIC;
		goto unlock;
	}

	/* Setting legacy policies on threads kills the current QoS */
	if (thread->requested_policy.thrp_qos != THREAD_QOS_UNSPECIFIED) {
		thread_remove_qos_policy_locked(thread, &pend_token);
	}

	kr = thread_set_mode_and_absolute_pri_internal(thread, mode, priority, &pend_token);

unlock:
	thread_mtx_unlock(thread);

	thread_policy_update_complete_unlocked(thread, &pend_token);

	return kr;
}

/*
 * Set the thread's requested mode and recompute priority
 * Called with thread mutex and thread locked
 *
 * TODO: Mitigate potential problems caused by moving thread to end of runq
 * whenever its priority is recomputed
 *      Only remove when it actually changes? Attempt to re-insert at appropriate location?
 */
static void
thread_set_user_sched_mode_and_recompute_pri(thread_t thread, sched_mode_t mode)
{
	if (thread->policy_reset) {
		return;
	}

	boolean_t removed = thread_run_queue_remove(thread);

	/*
	 * TODO: Instead of having saved mode, have 'user mode' and 'true mode'.
	 * That way there's zero confusion over which the user wants
	 * and which the kernel wants.
	 */
	if (thread->sched_flags & TH_SFLAG_DEMOTED_MASK) {
		thread->saved_mode = mode;
	} else {
		sched_set_thread_mode(thread, mode);
	}

	thread_recompute_priority(thread);

	if (removed) {
		thread_run_queue_reinsert(thread, SCHED_TAILQ);
	}
}

/* called at splsched with thread lock locked */
static void
thread_update_qos_cpu_time_locked(thread_t thread)
{
	task_t task = get_threadtask(thread);
	uint64_t timer_sum, timer_delta;

	/*
	 * This is only as accurate as the distance between
	 * last context switch (embedded) or last user/kernel boundary transition (desktop)
	 * because user_timer and system_timer are only updated then.
	 *
	 * TODO: Consider running a timer_update operation here to update it first.
	 *       Maybe doable with interrupts disabled from current thread.
	 *       If the thread is on a different core, may not be easy to get right.
	 *
	 * TODO: There should be a function for this in timer.c
	 */

	timer_sum = timer_grab(&thread->user_timer);
	timer_sum += timer_grab(&thread->system_timer);
	timer_delta = timer_sum - thread->vtimer_qos_save;

	thread->vtimer_qos_save = timer_sum;

	uint64_t* task_counter = NULL;

	/* Update the task-level effective and requested qos stats atomically, because we don't have the task lock. */
	switch (thread->effective_policy.thep_qos) {
	case THREAD_QOS_UNSPECIFIED:        task_counter = &task->cpu_time_eqos_stats.cpu_time_qos_default; break;
	case THREAD_QOS_MAINTENANCE:        task_counter = &task->cpu_time_eqos_stats.cpu_time_qos_maintenance; break;
	case THREAD_QOS_BACKGROUND:         task_counter = &task->cpu_time_eqos_stats.cpu_time_qos_background; break;
	case THREAD_QOS_UTILITY:            task_counter = &task->cpu_time_eqos_stats.cpu_time_qos_utility; break;
	case THREAD_QOS_LEGACY:             task_counter = &task->cpu_time_eqos_stats.cpu_time_qos_legacy; break;
	case THREAD_QOS_USER_INITIATED:     task_counter = &task->cpu_time_eqos_stats.cpu_time_qos_user_initiated; break;
	case THREAD_QOS_USER_INTERACTIVE:   task_counter = &task->cpu_time_eqos_stats.cpu_time_qos_user_interactive; break;
	default:
		panic("unknown effective QoS: %d", thread->effective_policy.thep_qos);
	}

	OSAddAtomic64(timer_delta, task_counter);

	/* Update the task-level qos stats atomically, because we don't have the task lock. */
	switch (thread->requested_policy.thrp_qos) {
	case THREAD_QOS_UNSPECIFIED:        task_counter = &task->cpu_time_rqos_stats.cpu_time_qos_default; break;
	case THREAD_QOS_MAINTENANCE:        task_counter = &task->cpu_time_rqos_stats.cpu_time_qos_maintenance; break;
	case THREAD_QOS_BACKGROUND:         task_counter = &task->cpu_time_rqos_stats.cpu_time_qos_background; break;
	case THREAD_QOS_UTILITY:            task_counter = &task->cpu_time_rqos_stats.cpu_time_qos_utility; break;
	case THREAD_QOS_LEGACY:             task_counter = &task->cpu_time_rqos_stats.cpu_time_qos_legacy; break;
	case THREAD_QOS_USER_INITIATED:     task_counter = &task->cpu_time_rqos_stats.cpu_time_qos_user_initiated; break;
	case THREAD_QOS_USER_INTERACTIVE:   task_counter = &task->cpu_time_rqos_stats.cpu_time_qos_user_interactive; break;
	default:
		panic("unknown requested QoS: %d", thread->requested_policy.thrp_qos);
	}

	OSAddAtomic64(timer_delta, task_counter);
}

/*
 * called with no thread locks held
 * may hold task lock
 */
void
thread_update_qos_cpu_time(thread_t thread)
{
	thread_mtx_lock(thread);

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

	thread_update_qos_cpu_time_locked(thread);

	thread_unlock(thread);
	splx(s);

	thread_mtx_unlock(thread);
}

/*
 * Calculate base priority from thread attributes, and set it on the thread
 *
 * Called with thread_lock and thread mutex held.
 */
extern boolean_t vps_dynamic_priority_enabled;

void
thread_recompute_priority(
	thread_t                thread)
{
	integer_t               priority;

	if (thread->policy_reset) {
		return;
	}

	if (thread->sched_mode == TH_MODE_REALTIME) {
		uint8_t i = thread->realtime.priority_offset;
		assert((i >= 0) && (i < NRTQS));
		priority = BASEPRI_RTQUEUES + i;
		sched_set_thread_base_priority(thread, priority);
		if (thread->realtime.deadline == RT_DEADLINE_NONE) {
			/* Make sure the thread has a valid deadline */
			uint64_t ctime = mach_absolute_time();
			thread->realtime.deadline = thread->realtime.constraint + ctime;
			KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_SET_RT_DEADLINE) | DBG_FUNC_NONE,
			    (uintptr_t)thread_tid(thread), thread->realtime.deadline, thread->realtime.computation, 1);
		}
		return;
	} else if (thread->effective_policy.thep_qos != THREAD_QOS_UNSPECIFIED) {
		int qos = thread->effective_policy.thep_qos;
		int qos_ui_is_urgent = thread->effective_policy.thep_qos_ui_is_urgent;
		int qos_relprio = -(thread->effective_policy.thep_qos_relprio); /* stored in task policy inverted */
		int qos_scaled_relprio;

		assert(qos >= 0 && qos < THREAD_QOS_LAST);
		assert(qos_relprio <= 0 && qos_relprio >= THREAD_QOS_MIN_TIER_IMPORTANCE);

		priority = thread_qos_policy_params.qos_pri[qos];
		qos_scaled_relprio = thread_qos_scaled_relative_priority(qos, qos_relprio);

		if (qos == THREAD_QOS_USER_INTERACTIVE && qos_ui_is_urgent == 1) {
			/* Bump priority 46 to 47 when in a frontmost app */
			qos_scaled_relprio += 1;
		}

		/* TODO: factor in renice priority here? */

		priority += qos_scaled_relprio;
	} else {
		if (thread->importance > MAXPRI) {
			priority = MAXPRI;
		} else if (thread->importance < -MAXPRI) {
			priority = -MAXPRI;
		} else {
			priority = thread->importance;
		}

		priority += thread->task_priority;
	}

	priority = MAX(priority, thread->user_promotion_basepri);

	/*
	 * Clamp priority back into the allowed range for this task.
	 *  The initial priority value could be out of this range due to:
	 *      Task clamped to BG or Utility (max-pri is 4, or 20)
	 *      Task is user task (max-pri is 63)
	 *      Task is kernel task (max-pri is 95)
	 * Note that thread->importance is user-settable to any integer
	 * via THREAD_PRECEDENCE_POLICY.
	 */
	if (priority > thread->max_priority) {
		if (thread->effective_policy.thep_promote_above_task) {
			priority = MAX(thread->max_priority, thread->user_promotion_basepri);
		} else {
			priority = thread->max_priority;
		}
	} else if (priority < MINPRI) {
		priority = MINPRI;
	}

	if (thread->saved_mode == TH_MODE_REALTIME &&
	    thread->sched_flags & TH_SFLAG_FAILSAFE) {
		priority = DEPRESSPRI;
	}

	if (thread->effective_policy.thep_terminated == TRUE) {
		/*
		 * We temporarily want to override the expected priority to
		 * ensure that the thread exits in a timely manner.
		 * Note that this is allowed to exceed thread->max_priority
		 * so that the thread is no longer clamped to background
		 * during the final exit phase.
		 */
		if (priority < thread->task_priority) {
			priority = thread->task_priority;
		}
		if (priority < BASEPRI_DEFAULT) {
			priority = BASEPRI_DEFAULT;
		}
	}

#if !defined(XNU_TARGET_OS_OSX)
	/* No one can have a base priority less than MAXPRI_THROTTLE */
	if (priority < MAXPRI_THROTTLE) {
		priority = MAXPRI_THROTTLE;
	}
#endif /* !defined(XNU_TARGET_OS_OSX) */

	sched_set_thread_base_priority(thread, priority);
}

/* Called with the task lock held, but not the thread mutex or spinlock */
void
thread_policy_update_tasklocked(
	thread_t           thread,
	integer_t          priority,
	integer_t          max_priority,
	task_pend_token_t  pend_token)
{
	thread_mtx_lock(thread);

	if (!thread->active || thread->policy_reset) {
		thread_mtx_unlock(thread);
		return;
	}

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

	__unused
	integer_t old_max_priority = thread->max_priority;

	assert(priority >= INT16_MIN && priority <= INT16_MAX);
	thread->task_priority = (int16_t)priority;

	assert(max_priority >= INT16_MIN && max_priority <= INT16_MAX);
	thread->max_priority = (int16_t)max_priority;

	/*
	 * When backgrounding a thread, realtime and fixed priority threads
	 * should be demoted to timeshare background threads.
	 *
	 * TODO: Do this inside the thread policy update routine in order to avoid double
	 * remove/reinsert for a runnable thread
	 */
	if ((max_priority <= MAXPRI_THROTTLE) && (old_max_priority > MAXPRI_THROTTLE)) {
		sched_thread_mode_demote(thread, TH_SFLAG_THROTTLED);
	} else if ((max_priority > MAXPRI_THROTTLE) && (old_max_priority <= MAXPRI_THROTTLE)) {
		sched_thread_mode_undemote(thread, TH_SFLAG_THROTTLED);
	}

	thread_policy_update_spinlocked(thread, true, pend_token);

	thread_unlock(thread);
	splx(s);

	thread_mtx_unlock(thread);
}

/*
 * Reset thread to default state in preparation for termination
 * Called with thread mutex locked
 *
 * Always called on current thread, so we don't need a run queue remove
 */
void
thread_policy_reset(
	thread_t                thread)
{
	spl_t           s;

	assert(thread == current_thread());

	s = splsched();
	thread_lock(thread);

	if (thread->sched_flags & TH_SFLAG_FAILSAFE) {
		sched_thread_mode_undemote(thread, TH_SFLAG_FAILSAFE);
	}

	if (thread->sched_flags & TH_SFLAG_THROTTLED) {
		sched_thread_mode_undemote(thread, TH_SFLAG_THROTTLED);
	}

	/* At this point, the various demotions should be inactive */
	assert(!(thread->sched_flags & TH_SFLAG_DEMOTED_MASK));
	assert(!(thread->sched_flags & TH_SFLAG_THROTTLED));
	assert(!(thread->sched_flags & TH_SFLAG_DEPRESSED_MASK));

	/* Reset thread back to task-default basepri and mode  */
	sched_mode_t newmode = SCHED(initial_thread_sched_mode)(get_threadtask(thread));

	sched_set_thread_mode(thread, newmode);

	thread->importance = 0;

	/* Prevent further changes to thread base priority or mode */
	thread->policy_reset = 1;

	sched_set_thread_base_priority(thread, thread->task_priority);

	thread_unlock(thread);
	splx(s);
}

kern_return_t
thread_policy_get(
	thread_t                                thread,
	thread_policy_flavor_t  flavor,
	thread_policy_t                 policy_info,
	mach_msg_type_number_t  *count,
	boolean_t                               *get_default)
{
	kern_return_t                   result = KERN_SUCCESS;

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

	thread_mtx_lock(thread);
	if (!thread->active) {
		thread_mtx_unlock(thread);

		return KERN_TERMINATED;
	}

	switch (flavor) {
	case THREAD_EXTENDED_POLICY:
	{
		boolean_t               timeshare = TRUE;

		if (!(*get_default)) {
			spl_t s = splsched();
			thread_lock(thread);

			if ((thread->sched_mode != TH_MODE_REALTIME) &&
			    (thread->saved_mode != TH_MODE_REALTIME)) {
				if (!(thread->sched_flags & TH_SFLAG_DEMOTED_MASK)) {
					timeshare = (thread->sched_mode == TH_MODE_TIMESHARE) != 0;
				} else {
					timeshare = (thread->saved_mode == TH_MODE_TIMESHARE) != 0;
				}
			} else {
				*get_default = TRUE;
			}

			thread_unlock(thread);
			splx(s);
		}

		if (*count >= THREAD_EXTENDED_POLICY_COUNT) {
			thread_extended_policy_t        info;

			info = (thread_extended_policy_t)policy_info;
			info->timeshare = timeshare;
		}

		break;
	}

	case THREAD_TIME_CONSTRAINT_POLICY:
	case THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY:
	{
		thread_time_constraint_with_priority_policy_t         info;

		mach_msg_type_number_t min_count = (flavor == THREAD_TIME_CONSTRAINT_POLICY ?
		    THREAD_TIME_CONSTRAINT_POLICY_COUNT :
		    THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY_COUNT);

		if (*count < min_count) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		info = (thread_time_constraint_with_priority_policy_t)policy_info;

		if (!(*get_default)) {
			spl_t s = splsched();
			thread_lock(thread);

			if ((thread->sched_mode == TH_MODE_REALTIME) ||
			    (thread->saved_mode == TH_MODE_REALTIME)) {
				info->period = thread->realtime.period;
				info->computation = thread->realtime.computation;
				info->constraint = thread->realtime.constraint;
				info->preemptible = thread->realtime.preemptible;
				if (flavor == THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY) {
					info->priority = thread->realtime.priority_offset + BASEPRI_RTQUEUES;
				}
			} else {
				*get_default = TRUE;
			}

			thread_unlock(thread);
			splx(s);
		}

		if (*get_default) {
			info->period = 0;
			info->computation = default_timeshare_computation;
			info->constraint = default_timeshare_constraint;
			info->preemptible = TRUE;
			if (flavor == THREAD_TIME_CONSTRAINT_WITH_PRIORITY_POLICY) {
				info->priority = BASEPRI_RTQUEUES;
			}
		}


		break;
	}

	case THREAD_PRECEDENCE_POLICY:
	{
		thread_precedence_policy_t              info;

		if (*count < THREAD_PRECEDENCE_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		info = (thread_precedence_policy_t)policy_info;

		if (!(*get_default)) {
			spl_t s = splsched();
			thread_lock(thread);

			info->importance = thread->importance;

			thread_unlock(thread);
			splx(s);
		} else {
			info->importance = 0;
		}

		break;
	}

	case THREAD_AFFINITY_POLICY:
	{
		thread_affinity_policy_t                info;

		if (!thread_affinity_is_supported()) {
			result = KERN_NOT_SUPPORTED;
			break;
		}
		if (*count < THREAD_AFFINITY_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		info = (thread_affinity_policy_t)policy_info;

		if (!(*get_default)) {
			info->affinity_tag = thread_affinity_get(thread);
		} else {
			info->affinity_tag = THREAD_AFFINITY_TAG_NULL;
		}

		break;
	}

	case THREAD_POLICY_STATE:
	{
		thread_policy_state_t           info;

		if (*count < THREAD_POLICY_STATE_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		/* Only root can get this info */
		if (!task_is_privileged(current_task())) {
			result = KERN_PROTECTION_FAILURE;
			break;
		}

		info = (thread_policy_state_t)(void*)policy_info;

		if (!(*get_default)) {
			info->flags = 0;

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

			info->flags |= (thread->static_param ? THREAD_POLICY_STATE_FLAG_STATIC_PARAM : 0);

			info->thps_requested_policy = *(uint64_t*)(void*)(&thread->requested_policy);
			info->thps_effective_policy = *(uint64_t*)(void*)(&thread->effective_policy);

			info->thps_user_promotions          = 0;
			info->thps_user_promotion_basepri   = thread->user_promotion_basepri;
			info->thps_ipc_overrides            = thread->kevent_overrides;

			proc_get_thread_policy_bitfield(thread, info);

			thread_unlock(thread);
			splx(s);
		} else {
			info->requested = 0;
			info->effective = 0;
			info->pending = 0;
		}

		break;
	}

	case THREAD_LATENCY_QOS_POLICY:
	{
		thread_latency_qos_policy_t info = (thread_latency_qos_policy_t) policy_info;
		thread_latency_qos_t plqos;

		if (*count < THREAD_LATENCY_QOS_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if (*get_default) {
			plqos = 0;
		} else {
			plqos = proc_get_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_LATENCY_QOS, NULL);
		}

		info->thread_latency_qos_tier = qos_latency_policy_package(plqos);
	}
	break;

	case THREAD_THROUGHPUT_QOS_POLICY:
	{
		thread_throughput_qos_policy_t info = (thread_throughput_qos_policy_t) policy_info;
		thread_throughput_qos_t ptqos;

		if (*count < THREAD_THROUGHPUT_QOS_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if (*get_default) {
			ptqos = 0;
		} else {
			ptqos = proc_get_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_THROUGH_QOS, NULL);
		}

		info->thread_throughput_qos_tier = qos_throughput_policy_package(ptqos);
	}
	break;

	case THREAD_QOS_POLICY:
	{
		thread_qos_policy_t info = (thread_qos_policy_t)policy_info;

		if (*count < THREAD_QOS_POLICY_COUNT) {
			result = KERN_INVALID_ARGUMENT;
			break;
		}

		if (!(*get_default)) {
			int relprio_value = 0;
			info->qos_tier = proc_get_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE,
			    TASK_POLICY_QOS_AND_RELPRIO, &relprio_value);

			info->tier_importance = -relprio_value;
		} else {
			info->qos_tier = THREAD_QOS_UNSPECIFIED;
			info->tier_importance = 0;
		}

		break;
	}

	default:
		result = KERN_INVALID_ARGUMENT;
		break;
	}

	thread_mtx_unlock(thread);

	return result;
}

void
thread_policy_create(thread_t thread)
{
	KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
	    (IMPORTANCE_CODE(IMP_UPDATE, (IMP_UPDATE_TASK_CREATE | TASK_POLICY_THREAD))) | DBG_FUNC_START,
	    thread_tid(thread), theffective_0(thread),
	    theffective_1(thread), thread->base_pri, 0);

	/* We pass a pend token but ignore it */
	struct task_pend_token pend_token = {};

	thread_policy_update_internal_spinlocked(thread, true, &pend_token);

	KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
	    (IMPORTANCE_CODE(IMP_UPDATE, (IMP_UPDATE_TASK_CREATE | TASK_POLICY_THREAD))) | DBG_FUNC_END,
	    thread_tid(thread), theffective_0(thread),
	    theffective_1(thread), thread->base_pri, 0);
}

static void
thread_policy_update_spinlocked(thread_t thread, bool recompute_priority, task_pend_token_t pend_token)
{
	KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
	    (IMPORTANCE_CODE(IMP_UPDATE, TASK_POLICY_THREAD) | DBG_FUNC_START),
	    thread_tid(thread), theffective_0(thread),
	    theffective_1(thread), thread->base_pri, 0);

	thread_policy_update_internal_spinlocked(thread, recompute_priority, pend_token);

	KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
	    (IMPORTANCE_CODE(IMP_UPDATE, TASK_POLICY_THREAD)) | DBG_FUNC_END,
	    thread_tid(thread), theffective_0(thread),
	    theffective_1(thread), thread->base_pri, 0);
}



/*
 * One thread state update function TO RULE THEM ALL
 *
 * This function updates the thread effective policy fields
 * and pushes the results to the relevant subsystems.
 *
 * Returns TRUE if a pended action needs to be run.
 *
 * Called with thread spinlock locked, task may be locked, thread mutex may be locked
 */
static void
thread_policy_update_internal_spinlocked(thread_t thread, bool recompute_priority,
    task_pend_token_t pend_token)
{
	/*
	 * Step 1:
	 *  Gather requested policy and effective task state
	 */

	struct thread_requested_policy requested = thread->requested_policy;
	struct task_effective_policy task_effective = get_threadtask(thread)->effective_policy;

	/*
	 * Step 2:
	 *  Calculate new effective policies from requested policy, task and thread state
	 *  Rules:
	 *      Don't change requested, it won't take effect
	 */

	struct thread_effective_policy next = {};

	next.thep_qos_ui_is_urgent = task_effective.tep_qos_ui_is_urgent;

	uint32_t next_qos = requested.thrp_qos;

	if (requested.thrp_qos != THREAD_QOS_UNSPECIFIED) {
		next_qos = MAX(requested.thrp_qos_override, next_qos);
		next_qos = MAX(requested.thrp_qos_promote, next_qos);
		next_qos = MAX(requested.thrp_qos_kevent_override, next_qos);
		next_qos = MAX(requested.thrp_qos_wlsvc_override, next_qos);
		next_qos = MAX(requested.thrp_qos_workq_override, next_qos);
	}

	if (task_effective.tep_darwinbg && task_effective.tep_adaptive_bg &&
	    requested.thrp_qos_promote > THREAD_QOS_BACKGROUND) {
		/*
		 * This thread is turnstile-boosted higher than the adaptive clamp
		 * by a synchronous waiter. Allow that to override the adaptive
		 * clamp temporarily for this thread only.
		 */
		next.thep_promote_above_task = true;
		next_qos = requested.thrp_qos_promote;
	}

	next.thep_qos = next_qos;

	/* A task clamp will result in an effective QoS even when requested is UNSPECIFIED */
	if (task_effective.tep_qos_clamp != THREAD_QOS_UNSPECIFIED) {
		if (next.thep_qos != THREAD_QOS_UNSPECIFIED) {
			next.thep_qos = MIN(task_effective.tep_qos_clamp, next.thep_qos);
		} else {
			next.thep_qos = task_effective.tep_qos_clamp;
		}
	}

	/*
	 * Extract outbound-promotion QoS before applying task ceiling or BG clamp
	 * This allows QoS promotions to work properly even after the process is unclamped.
	 */
	next.thep_qos_promote = next.thep_qos;

	/* The ceiling only applies to threads that are in the QoS world */
	/* TODO: is it appropriate for this to limit a turnstile-boosted thread's QoS? */
	if (task_effective.tep_qos_ceiling != THREAD_QOS_UNSPECIFIED &&
	    next.thep_qos != THREAD_QOS_UNSPECIFIED) {
		next.thep_qos = MIN(task_effective.tep_qos_ceiling, next.thep_qos);
	}

	/*
	 * The QoS relative priority is only applicable when the original programmer's
	 * intended (requested) QoS is in effect. When the QoS is clamped (e.g.
	 * USER_INITIATED-13REL clamped to UTILITY), the relative priority is not honored,
	 * since otherwise it would be lower than unclamped threads. Similarly, in the
	 * presence of boosting, the programmer doesn't know what other actors
	 * are boosting the thread.
	 */
	if ((requested.thrp_qos != THREAD_QOS_UNSPECIFIED) &&
	    (requested.thrp_qos == next.thep_qos) &&
	    (requested.thrp_qos_override == THREAD_QOS_UNSPECIFIED)) {
		next.thep_qos_relprio = requested.thrp_qos_relprio;
	} else {
		next.thep_qos_relprio = 0;
	}

	/* Calculate DARWIN_BG */
	bool wants_darwinbg        = false;
	bool wants_all_sockets_bg  = false; /* Do I want my existing sockets to be bg */

	if (task_effective.tep_darwinbg && !next.thep_promote_above_task) {
		wants_darwinbg = true;
	}

	/*
	 * If DARWIN_BG has been requested at either level, it's engaged.
	 * darwinbg threads always create bg sockets,
	 * but only some types of darwinbg change the sockets
	 * after they're created
	 */
	if (requested.thrp_int_darwinbg || requested.thrp_ext_darwinbg) {
		wants_all_sockets_bg = wants_darwinbg = true;
	}

	if (requested.thrp_pidbind_bg) {
		wants_all_sockets_bg = wants_darwinbg = true;
	}

	if (next.thep_qos == THREAD_QOS_BACKGROUND ||
	    next.thep_qos == THREAD_QOS_MAINTENANCE) {
		wants_darwinbg = true;
	}

	/* Calculate side effects of DARWIN_BG */

	if (wants_darwinbg) {
		next.thep_darwinbg = 1;
	}

	if (next.thep_darwinbg || task_effective.tep_new_sockets_bg) {
		next.thep_new_sockets_bg = 1;
	}

	/* Don't use task_effective.tep_all_sockets_bg here */
	if (wants_all_sockets_bg) {
		next.thep_all_sockets_bg = 1;
	}

	/* darwinbg implies background QOS (or lower) */
	if (next.thep_darwinbg &&
	    (next.thep_qos > THREAD_QOS_BACKGROUND || next.thep_qos == THREAD_QOS_UNSPECIFIED)) {
		next.thep_qos = THREAD_QOS_BACKGROUND;
		next.thep_qos_relprio = 0;
	}

	/* Calculate IO policy */

	int iopol = THROTTLE_LEVEL_TIER0;

	/* Factor in the task's IO policy */
	if (next.thep_darwinbg) {
		iopol = MAX(iopol, task_effective.tep_bg_iotier);
	}

	if (!next.thep_promote_above_task) {
		iopol = MAX(iopol, task_effective.tep_io_tier);
	}

	/* Look up the associated IO tier value for the QoS class */
	iopol = MAX(iopol, thread_qos_policy_params.qos_iotier[next.thep_qos]);

	iopol = MAX(iopol, requested.thrp_int_iotier);
	iopol = MAX(iopol, requested.thrp_ext_iotier);

	next.thep_io_tier = iopol;

	/*
	 * If a QoS override is causing IO to go into a lower tier, we also set
	 * the passive bit so that a thread doesn't end up stuck in its own throttle
	 * window when the override goes away.
	 */

	int next_qos_iotier = thread_qos_policy_params.qos_iotier[next.thep_qos];
	int req_qos_iotier = thread_qos_policy_params.qos_iotier[requested.thrp_qos];
	bool qos_io_override_active = (next_qos_iotier < req_qos_iotier);

	/* Calculate Passive IO policy */
	if (requested.thrp_ext_iopassive ||
	    requested.thrp_int_iopassive ||
	    qos_io_override_active ||
	    task_effective.tep_io_passive) {
		next.thep_io_passive = 1;
	}

	/* Calculate timer QOS */
	uint32_t latency_qos = requested.thrp_latency_qos;

	if (!next.thep_promote_above_task) {
		latency_qos = MAX(latency_qos, task_effective.tep_latency_qos);
	}

	latency_qos = MAX(latency_qos, thread_qos_policy_params.qos_latency_qos[next.thep_qos]);

	next.thep_latency_qos = latency_qos;

	/* Calculate throughput QOS */
	uint32_t through_qos = requested.thrp_through_qos;

	if (!next.thep_promote_above_task) {
		through_qos = MAX(through_qos, task_effective.tep_through_qos);
	}

	through_qos = MAX(through_qos, thread_qos_policy_params.qos_through_qos[next.thep_qos]);

	next.thep_through_qos = through_qos;

	if (task_effective.tep_terminated || requested.thrp_terminated) {
		/* Shoot down the throttles that slow down exit or response to SIGTERM */
		next.thep_terminated    = 1;
		next.thep_darwinbg      = 0;
		next.thep_io_tier       = THROTTLE_LEVEL_TIER0;
		next.thep_qos           = THREAD_QOS_UNSPECIFIED;
		next.thep_latency_qos   = LATENCY_QOS_TIER_UNSPECIFIED;
		next.thep_through_qos   = THROUGHPUT_QOS_TIER_UNSPECIFIED;
	}

	/*
	 * Step 3:
	 *  Swap out old policy for new policy
	 */

	struct thread_effective_policy prev = thread->effective_policy;

	thread_update_qos_cpu_time_locked(thread);

	/* This is the point where the new values become visible to other threads */
	thread->effective_policy = next;

	/*
	 * Step 4:
	 *  Pend updates that can't be done while holding the thread lock
	 */

	if (prev.thep_all_sockets_bg != next.thep_all_sockets_bg) {
		pend_token->tpt_update_sockets = 1;
	}

	/* TODO: Doesn't this only need to be done if the throttle went up? */
	if (prev.thep_io_tier != next.thep_io_tier) {
		pend_token->tpt_update_throttle = 1;
	}

	/*
	 * Check for the attributes that sfi_thread_classify() consults,
	 *  and trigger SFI re-evaluation.
	 */
	if (prev.thep_qos != next.thep_qos ||
	    prev.thep_darwinbg != next.thep_darwinbg) {
		pend_token->tpt_update_thread_sfi = 1;
	}

	integer_t old_base_pri = thread->base_pri;

	/*
	 * Step 5:
	 *  Update other subsystems as necessary if something has changed
	 */

	/* Check for the attributes that thread_recompute_priority() consults */
	if (prev.thep_qos != next.thep_qos ||
	    prev.thep_qos_relprio != next.thep_qos_relprio ||
	    prev.thep_qos_ui_is_urgent != next.thep_qos_ui_is_urgent ||
	    prev.thep_promote_above_task != next.thep_promote_above_task ||
	    prev.thep_terminated != next.thep_terminated ||
	    pend_token->tpt_force_recompute_pri == 1 ||
	    recompute_priority) {
		thread_recompute_priority(thread);
	}

	/*
	 * Check if the thread is waiting on a turnstile and needs priority propagation.
	 */
	if (pend_token->tpt_update_turnstile &&
	    ((old_base_pri == thread->base_pri) ||
	    !thread_get_waiting_turnstile(thread))) {
		/*
		 * Reset update turnstile pend token since either
		 * the thread priority did not change or thread is
		 * not blocked on a turnstile.
		 */
		pend_token->tpt_update_turnstile = 0;
	}
}


/*
 * Initiate a thread policy state transition on a thread with its TID
 * Useful if you cannot guarantee the thread won't get terminated
 * Precondition: No locks are held
 * Will take task lock - using the non-tid variant is faster
 * if you already have a thread ref.
 */
void
proc_set_thread_policy_with_tid(task_t     task,
    uint64_t   tid,
    int        category,
    int        flavor,
    int        value)
{
	/* takes task lock, returns ref'ed thread or NULL */
	thread_t thread = task_findtid(task, tid);

	if (thread == THREAD_NULL) {
		return;
	}

	proc_set_thread_policy(thread, category, flavor, value);

	thread_deallocate(thread);
}

/*
 * Initiate a thread policy transition on a thread
 * This path supports networking transitions (i.e. darwinbg transitions)
 * Precondition: No locks are held
 */
void
proc_set_thread_policy(thread_t   thread,
    int        category,
    int        flavor,
    int        value)
{
	struct task_pend_token pend_token = {};

	thread_mtx_lock(thread);

	proc_set_thread_policy_locked(thread, category, flavor, value, 0, &pend_token);

	thread_mtx_unlock(thread);

	thread_policy_update_complete_unlocked(thread, &pend_token);
}

/*
 * Do the things that can't be done while holding a thread mutex.
 * These are set up to call back into thread policy to get the latest value,
 * so they don't have to be synchronized with the update.
 * The only required semantic is 'call this sometime after updating effective policy'
 *
 * Precondition: Thread mutex is not held
 *
 * This may be called with the task lock held, but in that case it won't be
 * called with tpt_update_sockets set.
 */
void
thread_policy_update_complete_unlocked(thread_t thread, task_pend_token_t pend_token)
{
#ifdef MACH_BSD
	if (pend_token->tpt_update_sockets) {
		proc_apply_task_networkbg(task_pid(get_threadtask(thread)), thread);
	}
#endif /* MACH_BSD */

	if (pend_token->tpt_update_throttle) {
		rethrottle_thread(get_bsdthread_info(thread));
	}

	if (pend_token->tpt_update_thread_sfi) {
		sfi_reevaluate(thread);
	}

	if (pend_token->tpt_update_turnstile) {
		turnstile_update_thread_priority_chain(thread);
	}
}

/*
 * Set and update thread policy
 * Thread mutex might be held
 */
static void
proc_set_thread_policy_locked(thread_t          thread,
    int               category,
    int               flavor,
    int               value,
    int               value2,
    task_pend_token_t pend_token)
{
	spl_t s = splsched();
	thread_lock(thread);

	proc_set_thread_policy_spinlocked(thread, category, flavor, value, value2, pend_token);

	thread_unlock(thread);
	splx(s);
}

/*
 * Set and update thread policy
 * Thread spinlock is held
 */
static void
proc_set_thread_policy_spinlocked(thread_t          thread,
    int               category,
    int               flavor,
    int               value,
    int               value2,
    task_pend_token_t pend_token)
{
	KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
	    (IMPORTANCE_CODE(flavor, (category | TASK_POLICY_THREAD))) | DBG_FUNC_START,
	    thread_tid(thread), threquested_0(thread),
	    threquested_1(thread), value, 0);

	thread_set_requested_policy_spinlocked(thread, category, flavor, value, value2, pend_token);

	thread_policy_update_spinlocked(thread, false, pend_token);

	KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
	    (IMPORTANCE_CODE(flavor, (category | TASK_POLICY_THREAD))) | DBG_FUNC_END,
	    thread_tid(thread), threquested_0(thread),
	    threquested_1(thread), tpending(pend_token), 0);
}

/*
 * Set the requested state for a specific flavor to a specific value.
 */
static void
thread_set_requested_policy_spinlocked(thread_t     thread,
    int               category,
    int               flavor,
    int               value,
    int               value2,
    task_pend_token_t pend_token)
{
	int tier, passive;

	struct thread_requested_policy requested = thread->requested_policy;

	switch (flavor) {
	/* Category: EXTERNAL and INTERNAL, thread and task */

	case TASK_POLICY_DARWIN_BG:
		if (category == TASK_POLICY_EXTERNAL) {
			requested.thrp_ext_darwinbg = value;
		} else {
			requested.thrp_int_darwinbg = value;
		}
		break;

	case TASK_POLICY_IOPOL:
		proc_iopol_to_tier(value, &tier, &passive);
		if (category == TASK_POLICY_EXTERNAL) {
			requested.thrp_ext_iotier  = tier;
			requested.thrp_ext_iopassive = passive;
		} else {
			requested.thrp_int_iotier  = tier;
			requested.thrp_int_iopassive = passive;
		}
		break;

	case TASK_POLICY_IO:
		if (category == TASK_POLICY_EXTERNAL) {
			requested.thrp_ext_iotier = value;
		} else {
			requested.thrp_int_iotier = value;
		}
		break;

	case TASK_POLICY_PASSIVE_IO:
		if (category == TASK_POLICY_EXTERNAL) {
			requested.thrp_ext_iopassive = value;
		} else {
			requested.thrp_int_iopassive = value;
		}
		break;

	/* Category: ATTRIBUTE, thread only */

	case TASK_POLICY_PIDBIND_BG:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_pidbind_bg = value;
		break;

	case TASK_POLICY_LATENCY_QOS:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_latency_qos = value;
		break;

	case TASK_POLICY_THROUGH_QOS:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_through_qos = value;
		break;

	case TASK_POLICY_QOS_OVERRIDE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_qos_override = value;
		pend_token->tpt_update_turnstile = 1;
		break;

	case TASK_POLICY_QOS_AND_RELPRIO:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_qos = value;
		requested.thrp_qos_relprio = value2;
		pend_token->tpt_update_turnstile = 1;
		DTRACE_BOOST3(qos_set, uint64_t, thread->thread_id, int, requested.thrp_qos, int, requested.thrp_qos_relprio);
		break;

	case TASK_POLICY_QOS_WORKQ_OVERRIDE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_qos_workq_override = value;
		pend_token->tpt_update_turnstile = 1;
		break;

	case TASK_POLICY_QOS_PROMOTE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_qos_promote = value;
		break;

	case TASK_POLICY_QOS_KEVENT_OVERRIDE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_qos_kevent_override = value;
		pend_token->tpt_update_turnstile = 1;
		break;

	case TASK_POLICY_QOS_SERVICER_OVERRIDE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_qos_wlsvc_override = value;
		pend_token->tpt_update_turnstile = 1;
		break;

	case TASK_POLICY_TERMINATED:
		assert(category == TASK_POLICY_ATTRIBUTE);
		requested.thrp_terminated = value;
		break;

	default:
		panic("unknown task policy: %d %d %d", category, flavor, value);
		break;
	}

	thread->requested_policy = requested;
}

/*
 * Gets what you set. Effective values may be different.
 * Precondition: No locks are held
 */
int
proc_get_thread_policy(thread_t   thread,
    int        category,
    int        flavor)
{
	int value = 0;
	thread_mtx_lock(thread);
	value = proc_get_thread_policy_locked(thread, category, flavor, NULL);
	thread_mtx_unlock(thread);
	return value;
}

static int
proc_get_thread_policy_locked(thread_t   thread,
    int        category,
    int        flavor,
    int*       value2)
{
	int value = 0;

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

	value = thread_get_requested_policy_spinlocked(thread, category, flavor, value2);

	thread_unlock(thread);
	splx(s);

	return value;
}

/*
 * Gets what you set. Effective values may be different.
 */
static int
thread_get_requested_policy_spinlocked(thread_t thread,
    int      category,
    int      flavor,
    int*     value2)
{
	int value = 0;

	struct thread_requested_policy requested = thread->requested_policy;

	switch (flavor) {
	case TASK_POLICY_DARWIN_BG:
		if (category == TASK_POLICY_EXTERNAL) {
			value = requested.thrp_ext_darwinbg;
		} else {
			value = requested.thrp_int_darwinbg;
		}
		break;
	case TASK_POLICY_IOPOL:
		if (category == TASK_POLICY_EXTERNAL) {
			value = proc_tier_to_iopol(requested.thrp_ext_iotier,
			    requested.thrp_ext_iopassive);
		} else {
			value = proc_tier_to_iopol(requested.thrp_int_iotier,
			    requested.thrp_int_iopassive);
		}
		break;
	case TASK_POLICY_IO:
		if (category == TASK_POLICY_EXTERNAL) {
			value = requested.thrp_ext_iotier;
		} else {
			value = requested.thrp_int_iotier;
		}
		break;
	case TASK_POLICY_PASSIVE_IO:
		if (category == TASK_POLICY_EXTERNAL) {
			value = requested.thrp_ext_iopassive;
		} else {
			value = requested.thrp_int_iopassive;
		}
		break;
	case TASK_POLICY_QOS:
		assert(category == TASK_POLICY_ATTRIBUTE);
		value = requested.thrp_qos;
		break;
	case TASK_POLICY_QOS_OVERRIDE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		value = requested.thrp_qos_override;
		break;
	case TASK_POLICY_LATENCY_QOS:
		assert(category == TASK_POLICY_ATTRIBUTE);
		value = requested.thrp_latency_qos;
		break;
	case TASK_POLICY_THROUGH_QOS:
		assert(category == TASK_POLICY_ATTRIBUTE);
		value = requested.thrp_through_qos;
		break;
	case TASK_POLICY_QOS_WORKQ_OVERRIDE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		value = requested.thrp_qos_workq_override;
		break;
	case TASK_POLICY_QOS_AND_RELPRIO:
		assert(category == TASK_POLICY_ATTRIBUTE);
		assert(value2 != NULL);
		value = requested.thrp_qos;
		*value2 = requested.thrp_qos_relprio;
		break;
	case TASK_POLICY_QOS_PROMOTE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		value = requested.thrp_qos_promote;
		break;
	case TASK_POLICY_QOS_KEVENT_OVERRIDE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		value = requested.thrp_qos_kevent_override;
		break;
	case TASK_POLICY_QOS_SERVICER_OVERRIDE:
		assert(category == TASK_POLICY_ATTRIBUTE);
		value = requested.thrp_qos_wlsvc_override;
		break;
	case TASK_POLICY_TERMINATED:
		assert(category == TASK_POLICY_ATTRIBUTE);
		value = requested.thrp_terminated;
		break;

	default:
		panic("unknown policy_flavor %d", flavor);
		break;
	}

	return value;
}

/*
 * Gets what is actually in effect, for subsystems which pull policy instead of receive updates.
 *
 * NOTE: This accessor does not take the task or thread lock.
 * Notifications of state updates need to be externally synchronized with state queries.
 * This routine *MUST* remain interrupt safe, as it is potentially invoked
 * within the context of a timer interrupt.
 *
 * TODO: I think we can get away with architecting this such that we don't need to look at the task ever.
 *      Is that a good idea? Maybe it's best to avoid evaluate-all-the-threads updates.
 *      I don't think that cost is worth not having the right answer.
 */
int
proc_get_effective_thread_policy(thread_t thread,
    int      flavor)
{
	int value = 0;

	switch (flavor) {
	case TASK_POLICY_DARWIN_BG:
		/*
		 * This call is used within the timer layer, as well as
		 * prioritizing requests to the graphics system.
		 * It also informs SFI and originator-bg-state.
		 * Returns 1 for background mode, 0 for normal mode
		 */

		value = thread->effective_policy.thep_darwinbg ? 1 : 0;
		break;
	case TASK_POLICY_IO:
		/*
		 * The I/O system calls here to find out what throttling tier to apply to an operation.
		 * Returns THROTTLE_LEVEL_* values
		 */
		value = thread->effective_policy.thep_io_tier;
		if (thread->iotier_override != THROTTLE_LEVEL_NONE) {
			value = MIN(value, thread->iotier_override);
		}
		break;
	case TASK_POLICY_PASSIVE_IO:
		/*
		 * The I/O system calls here to find out whether an operation should be passive.
		 * (i.e. not cause operations with lower throttle tiers to be throttled)
		 * Returns 1 for passive mode, 0 for normal mode
		 *
		 * If an override is causing IO to go into a lower tier, we also set
		 * the passive bit so that a thread doesn't end up stuck in its own throttle
		 * window when the override goes away.
		 */
		value = thread->effective_policy.thep_io_passive ? 1 : 0;
		if (thread->iotier_override != THROTTLE_LEVEL_NONE &&
		    thread->iotier_override < thread->effective_policy.thep_io_tier) {
			value = 1;
		}
		break;
	case TASK_POLICY_ALL_SOCKETS_BG:
		/*
		 * do_background_socket() calls this to determine whether
		 * it should change the thread's sockets
		 * Returns 1 for background mode, 0 for normal mode
		 * This consults both thread and task so un-DBGing a thread while the task is BG
		 * doesn't get you out of the network throttle.
		 */
		value = (thread->effective_policy.thep_all_sockets_bg ||
		    get_threadtask(thread)->effective_policy.tep_all_sockets_bg) ? 1 : 0;
		break;
	case TASK_POLICY_NEW_SOCKETS_BG:
		/*
		 * socreate() calls this to determine if it should mark a new socket as background
		 * Returns 1 for background mode, 0 for normal mode
		 */
		value = thread->effective_policy.thep_new_sockets_bg ? 1 : 0;
		break;
	case TASK_POLICY_LATENCY_QOS:
		/*
		 * timer arming calls into here to find out the timer coalescing level
		 * Returns a latency QoS tier (0-6)
		 */
		value = thread->effective_policy.thep_latency_qos;
		break;
	case TASK_POLICY_THROUGH_QOS:
		/*
		 * This value is passed into the urgency callout from the scheduler
		 * to the performance management subsystem.
		 *
		 * Returns a throughput QoS tier (0-6)
		 */
		value = thread->effective_policy.thep_through_qos;
		break;
	case TASK_POLICY_QOS:
		/*
		 * This is communicated to the performance management layer and SFI.
		 *
		 * Returns a QoS policy tier
		 */
		value = thread->effective_policy.thep_qos;
		break;
	default:
		panic("unknown thread policy flavor %d", flavor);
		break;
	}

	return value;
}


/*
 * (integer_t) casts limit the number of bits we can fit here
 * this interface is deprecated and replaced by the _EXT struct ?
 */
static void
proc_get_thread_policy_bitfield(thread_t thread, thread_policy_state_t info)
{
	uint64_t bits = 0;
	struct thread_requested_policy requested = thread->requested_policy;

	bits |= (requested.thrp_int_darwinbg    ? POLICY_REQ_INT_DARWIN_BG  : 0);
	bits |= (requested.thrp_ext_darwinbg    ? POLICY_REQ_EXT_DARWIN_BG  : 0);
	bits |= (requested.thrp_int_iotier      ? (((uint64_t)requested.thrp_int_iotier) << POLICY_REQ_INT_IO_TIER_SHIFT) : 0);
	bits |= (requested.thrp_ext_iotier      ? (((uint64_t)requested.thrp_ext_iotier) << POLICY_REQ_EXT_IO_TIER_SHIFT) : 0);
	bits |= (requested.thrp_int_iopassive   ? POLICY_REQ_INT_PASSIVE_IO : 0);
	bits |= (requested.thrp_ext_iopassive   ? POLICY_REQ_EXT_PASSIVE_IO : 0);

	bits |= (requested.thrp_qos             ? (((uint64_t)requested.thrp_qos) << POLICY_REQ_TH_QOS_SHIFT) : 0);
	bits |= (requested.thrp_qos_override    ? (((uint64_t)requested.thrp_qos_override) << POLICY_REQ_TH_QOS_OVER_SHIFT)   : 0);

	bits |= (requested.thrp_pidbind_bg      ? POLICY_REQ_PIDBIND_BG     : 0);

	bits |= (requested.thrp_latency_qos     ? (((uint64_t)requested.thrp_latency_qos) << POLICY_REQ_BASE_LATENCY_QOS_SHIFT) : 0);
	bits |= (requested.thrp_through_qos     ? (((uint64_t)requested.thrp_through_qos) << POLICY_REQ_BASE_THROUGH_QOS_SHIFT) : 0);

	info->requested = (integer_t) bits;
	bits = 0;

	struct thread_effective_policy effective = thread->effective_policy;

	bits |= (effective.thep_darwinbg        ? POLICY_EFF_DARWIN_BG      : 0);

	bits |= (effective.thep_io_tier         ? (((uint64_t)effective.thep_io_tier) << POLICY_EFF_IO_TIER_SHIFT) : 0);
	bits |= (effective.thep_io_passive      ? POLICY_EFF_IO_PASSIVE     : 0);
	bits |= (effective.thep_all_sockets_bg  ? POLICY_EFF_ALL_SOCKETS_BG : 0);
	bits |= (effective.thep_new_sockets_bg  ? POLICY_EFF_NEW_SOCKETS_BG : 0);

	bits |= (effective.thep_qos             ? (((uint64_t)effective.thep_qos) << POLICY_EFF_TH_QOS_SHIFT) : 0);

	bits |= (effective.thep_latency_qos     ? (((uint64_t)effective.thep_latency_qos) << POLICY_EFF_LATENCY_QOS_SHIFT) : 0);
	bits |= (effective.thep_through_qos     ? (((uint64_t)effective.thep_through_qos) << POLICY_EFF_THROUGH_QOS_SHIFT) : 0);

	info->effective = (integer_t)bits;
	bits = 0;

	info->pending = 0;
}

/*
 * Sneakily trace either the task and thread requested
 * or just the thread requested, depending on if we have enough room.
 * We do have room on LP64. On LP32, we have to split it between two uintptr_t's.
 *
 *                                LP32            LP64
 * threquested_0(thread)          thread[0]       task[0]
 * threquested_1(thread)          thread[1]       thread[0]
 *
 */

uintptr_t
threquested_0(thread_t thread)
{
	static_assert(sizeof(struct thread_requested_policy) == sizeof(uint64_t), "size invariant violated");

	uintptr_t* raw = (uintptr_t*)(void*)&thread->requested_policy;

	return raw[0];
}

uintptr_t
threquested_1(thread_t thread)
{
#if defined __LP64__
	return *(uintptr_t*)&get_threadtask(thread)->requested_policy;
#else
	uintptr_t* raw = (uintptr_t*)(void*)&thread->requested_policy;
	return raw[1];
#endif
}

uintptr_t
theffective_0(thread_t thread)
{
	static_assert(sizeof(struct thread_effective_policy) == sizeof(uint64_t), "size invariant violated");

	uintptr_t* raw = (uintptr_t*)(void*)&thread->effective_policy;
	return raw[0];
}

uintptr_t
theffective_1(thread_t thread)
{
#if defined __LP64__
	return *(uintptr_t*)&get_threadtask(thread)->effective_policy;
#else
	uintptr_t* raw = (uintptr_t*)(void*)&thread->effective_policy;
	return raw[1];
#endif
}


/*
 * Set an override on the thread which is consulted with a
 * higher priority than the task/thread policy. This should
 * only be set for temporary grants until the thread
 * returns to the userspace boundary
 *
 * We use atomic operations to swap in the override, with
 * the assumption that the thread itself can
 * read the override and clear it on return to userspace.
 *
 * No locking is performed, since it is acceptable to see
 * a stale override for one loop through throttle_lowpri_io().
 * However a thread reference must be held on the thread.
 */

void
set_thread_iotier_override(thread_t thread, int policy)
{
	int current_override;

	/* Let most aggressive I/O policy win until user boundary */
	do {
		current_override = thread->iotier_override;

		if (current_override != THROTTLE_LEVEL_NONE) {
			policy = MIN(current_override, policy);
		}

		if (current_override == policy) {
			/* no effective change */
			return;
		}
	} while (!OSCompareAndSwap(current_override, policy, &thread->iotier_override));

	/*
	 * Since the thread may be currently throttled,
	 * re-evaluate tiers and potentially break out
	 * of an msleep
	 */
	rethrottle_thread(get_bsdthread_info(thread));
}

/*
 * Userspace synchronization routines (like pthread mutexes, pthread reader-writer locks,
 * semaphores, dispatch_sync) may result in priority inversions where a higher priority
 * (i.e. scheduler priority, I/O tier, QoS tier) is waiting on a resource owned by a lower
 * priority thread. In these cases, we attempt to propagate the priority token, as long
 * as the subsystem informs us of the relationships between the threads. The userspace
 * synchronization subsystem should maintain the information of owner->resource and
 * resource->waiters itself.
 */

/*
 * This helper canonicalizes the resource/resource_type given the current qos_override_mode
 * in effect. Note that wildcards (THREAD_QOS_OVERRIDE_RESOURCE_WILDCARD) may need
 * to be handled specially in the future, but for now it's fine to slam
 * *resource to USER_ADDR_NULL even if it was previously a wildcard.
 */
static void
canonicalize_resource_and_type(user_addr_t *resource, int *resource_type)
{
	if (qos_override_mode == QOS_OVERRIDE_MODE_OVERHANG_PEAK || qos_override_mode == QOS_OVERRIDE_MODE_IGNORE_OVERRIDE) {
		/* Map all input resource/type to a single one */
		*resource = USER_ADDR_NULL;
		*resource_type = THREAD_QOS_OVERRIDE_TYPE_UNKNOWN;
	} else if (qos_override_mode == QOS_OVERRIDE_MODE_FINE_GRAINED_OVERRIDE) {
		/* no transform */
	} else if (qos_override_mode == QOS_OVERRIDE_MODE_FINE_GRAINED_OVERRIDE_BUT_SINGLE_MUTEX_OVERRIDE) {
		/* Map all mutex overrides to a single one, to avoid memory overhead */
		if (*resource_type == THREAD_QOS_OVERRIDE_TYPE_PTHREAD_MUTEX) {
			*resource = USER_ADDR_NULL;
		}
	}
}

/* This helper routine finds an existing override if known. Locking should be done by caller */
static struct thread_qos_override *
find_qos_override(thread_t thread,
    user_addr_t resource,
    int resource_type)
{
	struct thread_qos_override *override;

	override = thread->overrides;
	while (override) {
		if (override->override_resource == resource &&
		    override->override_resource_type == resource_type) {
			return override;
		}

		override = override->override_next;
	}

	return NULL;
}

static void
find_and_decrement_qos_override(thread_t       thread,
    user_addr_t    resource,
    int            resource_type,
    boolean_t      reset,
    struct thread_qos_override **free_override_list)
{
	struct thread_qos_override *override, *override_prev;

	override_prev = NULL;
	override = thread->overrides;
	while (override) {
		struct thread_qos_override *override_next = override->override_next;

		if ((THREAD_QOS_OVERRIDE_RESOURCE_WILDCARD == resource || override->override_resource == resource) &&
		    (THREAD_QOS_OVERRIDE_TYPE_WILDCARD == resource_type || override->override_resource_type == resource_type)) {
			if (reset) {
				override->override_contended_resource_count = 0;
			} else {
				override->override_contended_resource_count--;
			}

			if (override->override_contended_resource_count == 0) {
				if (override_prev == NULL) {
					thread->overrides = override_next;
				} else {
					override_prev->override_next = override_next;
				}

				/* Add to out-param for later zfree */
				override->override_next = *free_override_list;
				*free_override_list = override;
			} else {
				override_prev = override;
			}

			if (THREAD_QOS_OVERRIDE_RESOURCE_WILDCARD != resource) {
				return;
			}
		} else {
			override_prev = override;
		}

		override = override_next;
	}
}

/* This helper recalculates the current requested override using the policy selected at boot */
static int
calculate_requested_qos_override(thread_t thread)
{
	if (qos_override_mode == QOS_OVERRIDE_MODE_IGNORE_OVERRIDE) {
		return THREAD_QOS_UNSPECIFIED;
	}

	/* iterate over all overrides and calculate MAX */
	struct thread_qos_override *override;
	int qos_override = THREAD_QOS_UNSPECIFIED;

	override = thread->overrides;
	while (override) {
		qos_override = MAX(qos_override, override->override_qos);
		override = override->override_next;
	}

	return qos_override;
}

/*
 * Returns:
 * - 0 on success
 * - EINVAL if some invalid input was passed
 */
static int
proc_thread_qos_add_override_internal(thread_t         thread,
    int              override_qos,
    boolean_t        first_override_for_resource,
    user_addr_t      resource,
    int              resource_type)
{
	struct task_pend_token pend_token = {};
	int rc = 0;

	thread_mtx_lock(thread);

	KERNEL_DEBUG_CONSTANT((IMPORTANCE_CODE(IMP_USYNCH_QOS_OVERRIDE, IMP_USYNCH_ADD_OVERRIDE)) | DBG_FUNC_START,
	    thread_tid(thread), override_qos, first_override_for_resource ? 1 : 0, 0, 0);

	DTRACE_BOOST5(qos_add_override_pre, uint64_t, thread_tid(thread),
	    uint64_t, thread->requested_policy.thrp_qos,
	    uint64_t, thread->effective_policy.thep_qos,
	    int, override_qos, boolean_t, first_override_for_resource);

	struct thread_qos_override *override;
	struct thread_qos_override *override_new = NULL;
	int new_qos_override, prev_qos_override;
	int new_effective_qos;

	canonicalize_resource_and_type(&resource, &resource_type);

	override = find_qos_override(thread, resource, resource_type);
	if (first_override_for_resource && !override) {
		/* We need to allocate a new object. Drop the thread lock and
		 * recheck afterwards in case someone else added the override
		 */
		thread_mtx_unlock(thread);
		override_new = zalloc(thread_qos_override_zone);
		thread_mtx_lock(thread);
		override = find_qos_override(thread, resource, resource_type);
	}
	if (first_override_for_resource && override) {
		/* Someone else already allocated while the thread lock was dropped */
		override->override_contended_resource_count++;
	} else if (!override && override_new) {
		override = override_new;
		override_new = NULL;
		override->override_next = thread->overrides;
		/* since first_override_for_resource was TRUE */
		override->override_contended_resource_count = 1;
		override->override_resource = resource;
		override->override_resource_type = (int16_t)resource_type;
		override->override_qos = THREAD_QOS_UNSPECIFIED;
		thread->overrides = override;
	}

	if (override) {
		if (override->override_qos == THREAD_QOS_UNSPECIFIED) {
			override->override_qos = (int16_t)override_qos;
		} else {
			override->override_qos = MAX(override->override_qos, (int16_t)override_qos);
		}
	}

	/* Determine how to combine the various overrides into a single current
	 * requested override
	 */
	new_qos_override = calculate_requested_qos_override(thread);

	prev_qos_override = proc_get_thread_policy_locked(thread,
	    TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_OVERRIDE, NULL);

	if (new_qos_override != prev_qos_override) {
		proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE,
		    TASK_POLICY_QOS_OVERRIDE,
		    new_qos_override, 0, &pend_token);
	}

	new_effective_qos = proc_get_effective_thread_policy(thread, TASK_POLICY_QOS);

	thread_mtx_unlock(thread);

	thread_policy_update_complete_unlocked(thread, &pend_token);

	if (override_new) {
		zfree(thread_qos_override_zone, override_new);
	}

	DTRACE_BOOST4(qos_add_override_post, int, prev_qos_override,
	    int, new_qos_override, int, new_effective_qos, int, rc);

	KERNEL_DEBUG_CONSTANT((IMPORTANCE_CODE(IMP_USYNCH_QOS_OVERRIDE, IMP_USYNCH_ADD_OVERRIDE)) | DBG_FUNC_END,
	    new_qos_override, resource, resource_type, 0, 0);

	return rc;
}

int
proc_thread_qos_add_override(task_t           task,
    thread_t         thread,
    uint64_t         tid,
    int              override_qos,
    boolean_t        first_override_for_resource,
    user_addr_t      resource,
    int              resource_type)
{
	boolean_t has_thread_reference = FALSE;
	int rc = 0;

	if (thread == THREAD_NULL) {
		thread = task_findtid(task, tid);
		/* returns referenced thread */

		if (thread == THREAD_NULL) {
			KERNEL_DEBUG_CONSTANT((IMPORTANCE_CODE(IMP_USYNCH_QOS_OVERRIDE, IMP_USYNCH_ADD_OVERRIDE)) | DBG_FUNC_NONE,
			    tid, 0, 0xdead, 0, 0);
			return ESRCH;
		}
		has_thread_reference = TRUE;
	} else {
		assert(get_threadtask(thread) == task);
	}
	rc = proc_thread_qos_add_override_internal(thread, override_qos,
	    first_override_for_resource, resource, resource_type);
	if (has_thread_reference) {
		thread_deallocate(thread);
	}

	return rc;
}

static void
proc_thread_qos_remove_override_internal(thread_t       thread,
    user_addr_t    resource,
    int            resource_type,
    boolean_t      reset)
{
	struct task_pend_token pend_token = {};

	struct thread_qos_override *deferred_free_override_list = NULL;
	int new_qos_override, prev_qos_override, new_effective_qos;

	thread_mtx_lock(thread);

	canonicalize_resource_and_type(&resource, &resource_type);

	find_and_decrement_qos_override(thread, resource, resource_type, reset, &deferred_free_override_list);

	KERNEL_DEBUG_CONSTANT((IMPORTANCE_CODE(IMP_USYNCH_QOS_OVERRIDE, IMP_USYNCH_REMOVE_OVERRIDE)) | DBG_FUNC_START,
	    thread_tid(thread), resource, reset, 0, 0);

	DTRACE_BOOST3(qos_remove_override_pre, uint64_t, thread_tid(thread),
	    uint64_t, thread->requested_policy.thrp_qos,
	    uint64_t, thread->effective_policy.thep_qos);

	/* Determine how to combine the various overrides into a single current requested override */
	new_qos_override = calculate_requested_qos_override(thread);

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

	/*
	 * The override chain and therefore the value of the current override is locked with thread mutex,
	 * so we can do a get/set without races.  However, the rest of thread policy is locked under the spinlock.
	 * This means you can't change the current override from a spinlock-only setter.
	 */
	prev_qos_override = thread_get_requested_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_OVERRIDE, NULL);

	if (new_qos_override != prev_qos_override) {
		proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_OVERRIDE, new_qos_override, 0, &pend_token);
	}

	new_effective_qos = proc_get_effective_thread_policy(thread, TASK_POLICY_QOS);

	thread_unlock(thread);
	splx(s);

	thread_mtx_unlock(thread);

	thread_policy_update_complete_unlocked(thread, &pend_token);

	while (deferred_free_override_list) {
		struct thread_qos_override *override_next = deferred_free_override_list->override_next;

		zfree(thread_qos_override_zone, deferred_free_override_list);
		deferred_free_override_list = override_next;
	}

	DTRACE_BOOST3(qos_remove_override_post, int, prev_qos_override,
	    int, new_qos_override, int, new_effective_qos);

	KERNEL_DEBUG_CONSTANT((IMPORTANCE_CODE(IMP_USYNCH_QOS_OVERRIDE, IMP_USYNCH_REMOVE_OVERRIDE)) | DBG_FUNC_END,
	    thread_tid(thread), 0, 0, 0, 0);
}

int
proc_thread_qos_remove_override(task_t      task,
    thread_t    thread,
    uint64_t    tid,
    user_addr_t resource,
    int         resource_type)
{
	boolean_t has_thread_reference = FALSE;

	if (thread == THREAD_NULL) {
		thread = task_findtid(task, tid);
		/* returns referenced thread */

		if (thread == THREAD_NULL) {
			KERNEL_DEBUG_CONSTANT((IMPORTANCE_CODE(IMP_USYNCH_QOS_OVERRIDE, IMP_USYNCH_REMOVE_OVERRIDE)) | DBG_FUNC_NONE,
			    tid, 0, 0xdead, 0, 0);
			return ESRCH;
		}
		has_thread_reference = TRUE;
	} else {
		assert(task == get_threadtask(thread));
	}

	proc_thread_qos_remove_override_internal(thread, resource, resource_type, FALSE);

	if (has_thread_reference) {
		thread_deallocate(thread);
	}

	return 0;
}

/* Deallocate before thread termination */
void
proc_thread_qos_deallocate(thread_t thread)
{
	/* This thread must have no more IPC overrides. */
	assert(thread->kevent_overrides == 0);
	assert(thread->requested_policy.thrp_qos_kevent_override == THREAD_QOS_UNSPECIFIED);
	assert(thread->requested_policy.thrp_qos_wlsvc_override == THREAD_QOS_UNSPECIFIED);

	/*
	 * Clear out any lingering override objects.
	 */
	struct thread_qos_override *override;

	thread_mtx_lock(thread);
	override = thread->overrides;
	thread->overrides = NULL;
	thread->requested_policy.thrp_qos_override = THREAD_QOS_UNSPECIFIED;
	/* We don't need to re-evaluate thread policy here because the thread has already exited */
	thread_mtx_unlock(thread);

	while (override) {
		struct thread_qos_override *override_next = override->override_next;

		zfree(thread_qos_override_zone, override);
		override = override_next;
	}
}

/*
 * Set up the primordial thread's QoS
 */
void
task_set_main_thread_qos(task_t task, thread_t thread)
{
	struct task_pend_token pend_token = {};

	assert(get_threadtask(thread) == task);

	thread_mtx_lock(thread);

	KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
	    (IMPORTANCE_CODE(IMP_MAIN_THREAD_QOS, 0)) | DBG_FUNC_START,
	    thread_tid(thread), threquested_0(thread), threquested_1(thread),
	    thread->requested_policy.thrp_qos, 0);

	thread_qos_t primordial_qos = task_compute_main_thread_qos(task);

	proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_AND_RELPRIO,
	    primordial_qos, 0, &pend_token);

	thread_mtx_unlock(thread);

	thread_policy_update_complete_unlocked(thread, &pend_token);

	KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
	    (IMPORTANCE_CODE(IMP_MAIN_THREAD_QOS, 0)) | DBG_FUNC_END,
	    thread_tid(thread), threquested_0(thread), threquested_1(thread),
	    primordial_qos, 0);
}

/*
 * KPI for pthread kext
 *
 * Return a good guess at what the initial manager QoS will be
 * Dispatch can override this in userspace if it so chooses
 */
thread_qos_t
task_get_default_manager_qos(task_t task)
{
	thread_qos_t primordial_qos = task_compute_main_thread_qos(task);

	if (primordial_qos == THREAD_QOS_LEGACY) {
		primordial_qos = THREAD_QOS_USER_INITIATED;
	}

	return primordial_qos;
}

/*
 * Check if the kernel promotion on thread has changed
 * and apply it.
 *
 * thread locked on entry and exit
 */
boolean_t
thread_recompute_kernel_promotion_locked(thread_t thread)
{
	boolean_t needs_update = FALSE;
	uint8_t kern_promotion_schedpri = (uint8_t)thread_get_inheritor_turnstile_sched_priority(thread);

	/*
	 * For now just assert that kern_promotion_schedpri <= MAXPRI_PROMOTE.
	 * TURNSTILE_KERNEL_PROMOTE adds threads on the waitq already capped to MAXPRI_PROMOTE
	 * and propagates the priority through the chain with the same cap, because as of now it does
	 * not differenciate on the kernel primitive.
	 *
	 * If this assumption will change with the adoption of a kernel primitive that does not
	 * cap the when adding/propagating,
	 * then here is the place to put the generic cap for all kernel primitives
	 * (converts the assert to kern_promotion_schedpri = MIN(priority, MAXPRI_PROMOTE))
	 */
	assert(kern_promotion_schedpri <= MAXPRI_PROMOTE);

	if (kern_promotion_schedpri != thread->kern_promotion_schedpri) {
		KDBG(MACHDBG_CODE(
			    DBG_MACH_SCHED, MACH_TURNSTILE_KERNEL_CHANGE) | DBG_FUNC_NONE,
		    thread_tid(thread),
		    kern_promotion_schedpri,
		    thread->kern_promotion_schedpri);

		needs_update = TRUE;
		thread->kern_promotion_schedpri = kern_promotion_schedpri;
		thread_recompute_sched_pri(thread, SETPRI_DEFAULT);
	}

	return needs_update;
}

/*
 * Check if the user promotion on thread has changed
 * and apply it.
 *
 * thread locked on entry, might drop the thread lock
 * and reacquire it.
 */
boolean_t
thread_recompute_user_promotion_locked(thread_t thread)
{
	boolean_t needs_update = FALSE;
	struct task_pend_token pend_token = {};
	uint8_t user_promotion_basepri = MIN((uint8_t)thread_get_inheritor_turnstile_base_priority(thread), MAXPRI_USER);
	int old_base_pri = thread->base_pri;
	thread_qos_t qos_promotion;

	/* Check if user promotion has changed */
	if (thread->user_promotion_basepri == user_promotion_basepri) {
		return needs_update;
	} else {
		KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
		    (TURNSTILE_CODE(TURNSTILE_PRIORITY_OPERATIONS, (THREAD_USER_PROMOTION_CHANGE))) | DBG_FUNC_NONE,
		    thread_tid(thread),
		    user_promotion_basepri,
		    thread->user_promotion_basepri,
		    0, 0);
		KDBG(MACHDBG_CODE(
			    DBG_MACH_SCHED, MACH_TURNSTILE_USER_CHANGE) | DBG_FUNC_NONE,
		    thread_tid(thread),
		    user_promotion_basepri,
		    thread->user_promotion_basepri);
	}

	/* Update the user promotion base pri */
	thread->user_promotion_basepri = user_promotion_basepri;
	pend_token.tpt_force_recompute_pri = 1;

	if (user_promotion_basepri <= MAXPRI_THROTTLE) {
		qos_promotion = THREAD_QOS_UNSPECIFIED;
	} else {
		qos_promotion = thread_user_promotion_qos_for_pri(user_promotion_basepri);
	}

	proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
	    TASK_POLICY_QOS_PROMOTE, qos_promotion, 0, &pend_token);

	if (thread_get_waiting_turnstile(thread) &&
	    thread->base_pri != old_base_pri) {
		needs_update = TRUE;
	}

	thread_unlock(thread);

	thread_policy_update_complete_unlocked(thread, &pend_token);

	thread_lock(thread);

	return needs_update;
}

/*
 * Convert the thread user promotion base pri to qos for threads in qos world.
 * For priority above UI qos, the qos would be set to UI.
 */
thread_qos_t
thread_user_promotion_qos_for_pri(int priority)
{
	thread_qos_t qos;
	for (qos = THREAD_QOS_USER_INTERACTIVE; qos > THREAD_QOS_MAINTENANCE; qos--) {
		if (thread_qos_policy_params.qos_pri[qos] <= priority) {
			return qos;
		}
	}
	return THREAD_QOS_MAINTENANCE;
}

/*
 * Set the thread's QoS Kevent override
 * Owned by the Kevent subsystem
 *
 * May be called with spinlocks held, but not spinlocks
 * that may deadlock against the thread lock, the throttle lock, or the SFI lock.
 *
 * One 'add' must be balanced by one 'drop'.
 * Between 'add' and 'drop', the overide QoS value may be updated with an 'update'.
 * Before the thread is deallocated, there must be 0 remaining overrides.
 */
static void
thread_kevent_override(thread_t    thread,
    uint32_t    qos_override,
    boolean_t   is_new_override)
{
	struct task_pend_token pend_token = {};
	boolean_t needs_update;

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

	uint32_t old_override = thread->requested_policy.thrp_qos_kevent_override;

	assert(qos_override > THREAD_QOS_UNSPECIFIED);
	assert(qos_override < THREAD_QOS_LAST);

	if (is_new_override) {
		if (thread->kevent_overrides++ == 0) {
			/* This add is the first override for this thread */
			assert(old_override == THREAD_QOS_UNSPECIFIED);
		} else {
			/* There are already other overrides in effect for this thread */
			assert(old_override > THREAD_QOS_UNSPECIFIED);
		}
	} else {
		/* There must be at least one override (the previous add call) in effect */
		assert(thread->kevent_overrides > 0);
		assert(old_override > THREAD_QOS_UNSPECIFIED);
	}

	/*
	 * We can't allow lowering if there are several IPC overrides because
	 * the caller can't possibly know the whole truth
	 */
	if (thread->kevent_overrides == 1) {
		needs_update = qos_override != old_override;
	} else {
		needs_update = qos_override > old_override;
	}

	if (needs_update) {
		proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
		    TASK_POLICY_QOS_KEVENT_OVERRIDE,
		    qos_override, 0, &pend_token);
		assert(pend_token.tpt_update_sockets == 0);
	}

	thread_unlock(thread);
	splx(s);

	thread_policy_update_complete_unlocked(thread, &pend_token);
}

void
thread_add_kevent_override(thread_t thread, uint32_t qos_override)
{
	thread_kevent_override(thread, qos_override, TRUE);
}

void
thread_update_kevent_override(thread_t thread, uint32_t qos_override)
{
	thread_kevent_override(thread, qos_override, FALSE);
}

void
thread_drop_kevent_override(thread_t thread)
{
	struct task_pend_token pend_token = {};

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

	assert(thread->kevent_overrides > 0);

	if (--thread->kevent_overrides == 0) {
		/*
		 * There are no more overrides for this thread, so we should
		 * clear out the saturated override value
		 */

		proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
		    TASK_POLICY_QOS_KEVENT_OVERRIDE, THREAD_QOS_UNSPECIFIED,
		    0, &pend_token);
	}

	thread_unlock(thread);
	splx(s);

	thread_policy_update_complete_unlocked(thread, &pend_token);
}

/*
 * Set the thread's QoS Workloop Servicer override
 * Owned by the Kevent subsystem
 *
 * May be called with spinlocks held, but not spinlocks
 * that may deadlock against the thread lock, the throttle lock, or the SFI lock.
 *
 * One 'add' must be balanced by one 'drop'.
 * Between 'add' and 'drop', the overide QoS value may be updated with an 'update'.
 * Before the thread is deallocated, there must be 0 remaining overrides.
 */
static void
thread_servicer_override(thread_t    thread,
    uint32_t    qos_override,
    boolean_t   is_new_override)
{
	struct task_pend_token pend_token = {};

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

	if (is_new_override) {
		assert(!thread->requested_policy.thrp_qos_wlsvc_override);
	} else {
		assert(thread->requested_policy.thrp_qos_wlsvc_override);
	}

	proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
	    TASK_POLICY_QOS_SERVICER_OVERRIDE,
	    qos_override, 0, &pend_token);

	thread_unlock(thread);
	splx(s);

	assert(pend_token.tpt_update_sockets == 0);
	thread_policy_update_complete_unlocked(thread, &pend_token);
}

void
thread_add_servicer_override(thread_t thread, uint32_t qos_override)
{
	assert(qos_override > THREAD_QOS_UNSPECIFIED);
	assert(qos_override < THREAD_QOS_LAST);

	thread_servicer_override(thread, qos_override, TRUE);
}

void
thread_update_servicer_override(thread_t thread, uint32_t qos_override)
{
	assert(qos_override > THREAD_QOS_UNSPECIFIED);
	assert(qos_override < THREAD_QOS_LAST);

	thread_servicer_override(thread, qos_override, FALSE);
}

void
thread_drop_servicer_override(thread_t thread)
{
	thread_servicer_override(thread, THREAD_QOS_UNSPECIFIED, FALSE);
}


/* Get current requested qos / relpri, may be called from spinlock context */
thread_qos_t
thread_get_requested_qos(thread_t thread, int *relpri)
{
	int relprio_value = 0;
	thread_qos_t qos;

	qos = (thread_qos_t)proc_get_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE,
	    TASK_POLICY_QOS_AND_RELPRIO, &relprio_value);
	if (relpri) {
		*relpri = -relprio_value;
	}
	return qos;
}

/*
 * This function will promote the thread priority
 * since exec could block other threads calling
 * proc_find on the proc. This boost must be removed
 * via call to thread_clear_exec_promotion.
 *
 * This should be replaced with a generic 'priority inheriting gate' mechanism (24194397)
 */
void
thread_set_exec_promotion(thread_t thread)
{
	spl_t s = splsched();
	thread_lock(thread);

	sched_thread_promote_reason(thread, TH_SFLAG_EXEC_PROMOTED, 0);

	thread_unlock(thread);
	splx(s);
}

/*
 * This function will clear the exec thread
 * promotion set on the thread by thread_set_exec_promotion.
 */
void
thread_clear_exec_promotion(thread_t thread)
{
	spl_t s = splsched();
	thread_lock(thread);

	sched_thread_unpromote_reason(thread, TH_SFLAG_EXEC_PROMOTED, 0);

	thread_unlock(thread);
	splx(s);
}