thread_policy.c   [plain text]

/*
 * 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>

#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)

uint32_t qos_override_mode;
#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_IGNORE_DISPATCH 3
#define QOS_OVERRIDE_MODE_FINE_GRAINED_OVERRIDE_BUT_SINGLE_MUTEX_OVERRIDE 4

extern zone_t thread_qos_override_zone;

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

/*
 * 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);

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, boolean_t recompute_priority, task_pend_token_t pend_token);

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

void
thread_policy_init(void) {
	if (PE_parse_boot_argn("qos_override_mode", &qos_override_mode, sizeof(qos_override_mode))) {
		printf("QOS override mode: 0x%08x\n", qos_override_mode);
	} else {
		qos_override_mode = QOS_OVERRIDE_MODE_FINE_GRAINED_OVERRIDE_BUT_SINGLE_MUTEX_OVERRIDE;
	}
}

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
 */
boolean_t allow_qos_policy_set = 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 == FALSE) {
		if (thread_is_static_param(thread))
			return (KERN_POLICY_STATIC);

		if (flavor == THREAD_QOS_POLICY)
			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;
}

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:
	{
		thread_time_constraint_policy_t info;

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

		info = (thread_time_constraint_policy_t)policy_info;
		if (info->constraint  < info->computation   ||
		    info->computation > max_rt_quantum      ||
		    info->computation < min_rt_quantum      ) {
			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;

		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);
	}


	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;
}

/*
 * KPI for pthread kext
 *
 * Set scheduling policy & absolute priority for thread
 * May be called from waitqueue callout context with spinlocks held
 * Thread mutex lock is not held
 */
kern_return_t
thread_set_workq_pri(thread_t  thread,
                     integer_t priority,
                     integer_t policy)
{
	struct task_pend_token pend_token = {};
	sched_mode_t mode = convert_policy_to_sched_mode(policy);

	assert(thread->static_param);
	if (!thread->static_param)
		return KERN_FAILURE;

	/* Concern: this doesn't hold the mutex... */
	if (!thread->active)
		return KERN_TERMINATED;

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

	if (pend_token.tpt_update_thread_sfi)
		sfi_reevaluate(thread);

	return kr;
}

/*
 * 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 = thread->task;
	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 thread_timer_event 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 qos stats atomically, because we don't have the task lock. */
	switch (thread->effective_policy.thep_qos) {
		case THREAD_QOS_DEFAULT:            task_counter = &task->cpu_time_qos_stats.cpu_time_qos_default;          break;
		case THREAD_QOS_MAINTENANCE:        task_counter = &task->cpu_time_qos_stats.cpu_time_qos_maintenance;      break;
		case THREAD_QOS_BACKGROUND:         task_counter = &task->cpu_time_qos_stats.cpu_time_qos_background;       break;
		case THREAD_QOS_UTILITY:            task_counter = &task->cpu_time_qos_stats.cpu_time_qos_utility;          break;
		case THREAD_QOS_LEGACY:             task_counter = &task->cpu_time_qos_stats.cpu_time_qos_legacy;           break;
		case THREAD_QOS_USER_INITIATED:     task_counter = &task->cpu_time_qos_stats.cpu_time_qos_user_initiated;   break;
		case THREAD_QOS_USER_INTERACTIVE:   task_counter = &task->cpu_time_qos_stats.cpu_time_qos_user_interactive; break;
		default:
			panic("unknown effective QoS: %d", thread->effective_policy.thep_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.
 */
void
thread_recompute_priority(
	thread_t		thread)
{
	integer_t		priority;

	if (thread->policy_reset)
		return;

	if (thread->sched_mode == TH_MODE_REALTIME) {
		sched_set_thread_base_priority(thread, BASEPRI_RTQUEUES);
		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)
		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;
	}


	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;

	thread->task_priority = priority;
	thread->max_priority = max_priority;


	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)(thread->task);

	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:
	{
		thread_time_constraint_policy_t		info;

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

		info = (thread_time_constraint_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;
			}
			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;
		}

		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 (current_task()->sec_token.val[0] != 0) {
			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          = thread->user_promotions;
			info->thps_user_promotion_basepri   = thread->user_promotion_basepri;
			info->thps_ipc_overrides            = thread->ipc_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);
}

static volatile uint64_t unique_work_interval_id = 1; /* Start at 1, 0 is not a valid work interval ID */

kern_return_t
thread_policy_create_work_interval(
	thread_t		thread,
	uint64_t		*work_interval_id)
{
	thread_mtx_lock(thread);
	if (thread->work_interval_id) {
		/* already assigned a work interval ID */
		thread_mtx_unlock(thread);
		return (KERN_INVALID_VALUE);
	}

	thread->work_interval_id = OSIncrementAtomic64((volatile int64_t *)&unique_work_interval_id);
	*work_interval_id = thread->work_interval_id;

	thread_mtx_unlock(thread);
	return KERN_SUCCESS;
}

kern_return_t
thread_policy_destroy_work_interval(
	thread_t		thread,
	uint64_t		work_interval_id)
{
	thread_mtx_lock(thread);
	if (work_interval_id == 0 || thread->work_interval_id == 0 || thread->work_interval_id != work_interval_id) {
		/* work ID isn't valid or doesn't match previously assigned work interval ID */
		thread_mtx_unlock(thread);
		return (KERN_INVALID_ARGUMENT);
	}

	thread->work_interval_id = 0;

	thread_mtx_unlock(thread);
	return KERN_SUCCESS;
}

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, boolean_t 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, boolean_t 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 = thread->task->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) {
		if (requested.thrp_qos_override != THREAD_QOS_UNSPECIFIED)
			next_qos = MAX(requested.thrp_qos_override, next_qos);

		if (requested.thrp_qos_promote != THREAD_QOS_UNSPECIFIED)
			next_qos = MAX(requested.thrp_qos_promote, next_qos);

		if (requested.thrp_qos_ipc_override != THREAD_QOS_UNSPECIFIED)
			next_qos = MAX(requested.thrp_qos_ipc_override, next_qos);
	}

	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 */
	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 */
	boolean_t wants_darwinbg        = FALSE;
	boolean_t wants_all_sockets_bg  = FALSE; /* Do I want my existing sockets to be bg */

	/*
	 * 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 (task_effective.tep_darwinbg)
		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);

	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.
	 */
	boolean_t qos_io_override_active = FALSE;
	if (thread_qos_policy_params.qos_iotier[next.thep_qos] <
	    thread_qos_policy_params.qos_iotier[requested.thrp_qos])
		qos_io_override_active = TRUE;

	/* 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;

	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;

	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;

	/*
	 * 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_terminated        != next.thep_terminated         ||
	    pend_token->tpt_force_recompute_pri == 1                    ||
	    recompute_priority) {
		thread_recompute_priority(thread);
	}
}


/*
 * 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);
}

/*
 * KPI for pthread kext to call to set thread base QoS values during a workq wakeup
 * May be called with interrupts disabled and workqueue/waitqueue/kqueue locks held
 *
 * Does NOT do update completion, so the thread MUST be in a safe place WRT
 * IO throttling and SFI.
 *
 * TODO: Can I assert 'it must be in a safe place'?
 */
kern_return_t
thread_set_workq_qos(thread_t   thread,
                     int        qos_tier,
                     int        relprio) /* relprio is -16 to 0 */
{
	assert(qos_tier >= 0 && qos_tier <= THREAD_QOS_LAST);
	assert(relprio  <= 0 && relprio  >= THREAD_QOS_MIN_TIER_IMPORTANCE);

	if (!(qos_tier >= 0 && qos_tier <= THREAD_QOS_LAST))
		return KERN_FAILURE;
	if (!(relprio  <= 0 && relprio  >= THREAD_QOS_MIN_TIER_IMPORTANCE))
		return KERN_FAILURE;

	if (qos_tier == THREAD_QOS_UNSPECIFIED) {
		assert(relprio == 0);
		if (relprio != 0)
			return KERN_FAILURE;
	}

	assert(thread->static_param);
	if (!thread->static_param) {
		return KERN_FAILURE;
	}

	/* Concern: this doesn't hold the mutex... */
	//if (!thread->active)
	//	return KERN_TERMINATED;

	struct task_pend_token pend_token = {};

	proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_AND_RELPRIO, qos_tier, -relprio, &pend_token);

	assert(pend_token.tpt_update_sockets == 0);
	/* we don't need to update throttle or sfi because pthread kext promises the thread is in a safe place */
	/* TODO: Do we need to update SFI to ensure it gets tagged with the AST? */

	return KERN_SUCCESS;
}


/*
 * 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(thread->task->bsd_info, thread);
#endif /* MACH_BSD */

	if (pend_token->tpt_update_throttle)
		rethrottle_thread(thread->uthread);

	if (pend_token->tpt_update_thread_sfi)
		sfi_reevaluate(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);

	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)
{
	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:
			assert(category == TASK_POLICY_ATTRIBUTE);
			requested.thrp_qos = value;
			break;

		case TASK_POLICY_QOS_OVERRIDE:
			assert(category == TASK_POLICY_ATTRIBUTE);
			requested.thrp_qos_override = value;
			break;

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

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

		case TASK_POLICY_QOS_IPC_OVERRIDE:
			assert(category == TASK_POLICY_ATTRIBUTE);
			requested.thrp_qos_ipc_override = value;
			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_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_IPC_OVERRIDE:
			assert(category == TASK_POLICY_ATTRIBUTE);
			value = requested.thrp_qos_ipc_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 ||
			         thread->task->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*)&thread->task->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*)&thread->task->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(thread->uthread);
}

/*
 * 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_IGNORE_DISPATCH) {
		/* Map all dispatch overrides to a single one, to avoid memory overhead */
		if (*resource_type == THREAD_QOS_OVERRIDE_TYPE_DISPATCH_ASYNCHRONOUS_OVERRIDE) {
			*resource = USER_ADDR_NULL;
		}
	} 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) {
		if (qos_override_mode != QOS_OVERRIDE_MODE_FINE_GRAINED_OVERRIDE_BUT_IGNORE_DISPATCH ||
			override->override_resource_type != THREAD_QOS_OVERRIDE_TYPE_DISPATCH_ASYNCHRONOUS_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
 * - EFAULT if user_lock_addr != NULL and needs to be faulted (userland has to
 *   fault and retry)
 * - ESTALE if user_lock_addr != NULL &&
 *   ulock_owner_value_to_port_name(*user_lock_addr) != user_lock_owner
 */
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,
                                      user_addr_t      user_lock_addr,
                                      mach_port_name_t user_lock_owner)
{
	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 (user_lock_addr) {
		uint64_t val;
		/* Workaround lack of explicit support for 'no-fault copyin'
		 * <rdar://problem/24999882>, as disabling preemption prevents paging in
		 */
		disable_preemption();
		rc = copyin_word(user_lock_addr, &val, sizeof(user_lock_owner));
		enable_preemption();
		if (rc == 0 && ulock_owner_value_to_port_name((uint32_t)val) != user_lock_owner) {
			rc = ESTALE;
		}
		if (rc) {
			prev_qos_override = proc_get_thread_policy_locked(thread,
					TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_OVERRIDE, NULL);
			new_qos_override = prev_qos_override;
			new_effective_qos = proc_get_effective_thread_policy(thread, TASK_POLICY_QOS);
			thread_mtx_unlock(thread);
			goto out;
		}
	}
	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 = resource_type;
		override->override_qos = THREAD_QOS_UNSPECIFIED;
		thread->overrides = override;
	}

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

out:
	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_check_owner(thread_t thread,
                                         int override_qos,
                                         boolean_t first_override_for_resource,
                                         user_addr_t resource,
                                         int resource_type,
                                         user_addr_t user_lock_addr,
                                         mach_port_name_t user_lock_owner)
{
	return proc_thread_qos_add_override_internal(thread, override_qos,
			first_override_for_resource, resource, resource_type,
			user_lock_addr, user_lock_owner);
}

boolean_t
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 FALSE;
		}
		has_thread_reference = TRUE;
	} else {
		assert(thread->task == task);
	}
	rc = proc_thread_qos_add_override_internal(thread, override_qos,
			first_override_for_resource, resource, resource_type, 0, 0);
	if (has_thread_reference) {
		thread_deallocate(thread);
	}

	return rc == 0;
}

static int
proc_thread_qos_remove_override_internal(thread_t       thread,
                                         user_addr_t    resource,
                                         int            resource_type,
                                         boolean_t      reset,
                                         boolean_t      squash)
{
	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, prev_qos;
	int new_qos = THREAD_QOS_UNSPECIFIED;

	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 (squash) {
		/*
		 * Remove the specified overrides, and set the current override as the new base QoS.
		 * Return the new QoS value.
		 */
		prev_qos = thread_get_requested_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS, NULL);

		new_qos = MAX(prev_qos, prev_qos_override);
		if (new_qos != prev_qos)
			proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS, new_qos, 0, &pend_token);
	}

	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), squash, 0, 0, 0);

	return new_qos;
}

boolean_t
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 FALSE;
		}
		has_thread_reference = TRUE;
	} else {
		assert(task == thread->task);
	}

	proc_thread_qos_remove_override_internal(thread, resource, resource_type, FALSE, FALSE);

	if (has_thread_reference)
		thread_deallocate(thread);

	return TRUE;
}

boolean_t
proc_thread_qos_reset_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 FALSE;
		}
		has_thread_reference = TRUE;
	} else {
		assert(task == thread->task);
	}

	proc_thread_qos_remove_override_internal(thread, resource, resource_type, TRUE, FALSE);

	if (has_thread_reference)
		thread_deallocate(thread);

	return TRUE;
}

/*
 * Clears the requested overrides, and replaces the current QoS with the max
 * of the current QoS and the current override, then returns the new QoS.
 *
 * This is useful in order to reset overrides before parking a workqueue thread,
 * but avoid dropping priority and getting preempted right before parking.
 *
 * Called without any locks held.
 */
int
proc_thread_qos_squash_override(thread_t thread, user_addr_t resource, int resource_type)
{
	return proc_thread_qos_remove_override_internal(thread, resource, resource_type, TRUE, TRUE);
}

/* Deallocate before thread termination */
void proc_thread_qos_deallocate(thread_t thread)
{
	/*
	 * There are no more references to this thread,
	 * therefore this thread must not own any more locks,
	 * therefore there must not be any more user promotions.
	 */
	assert(thread->user_promotions == 0);
	assert(thread->requested_policy.thrp_qos_promote == THREAD_QOS_UNSPECIFIED);
	assert(thread->user_promotion_basepri == 0);

	/* This thread must have no more IPC overrides. */
	assert(thread->ipc_overrides == 0);
	assert(thread->requested_policy.thrp_qos_ipc_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(thread->task == 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);

	int primordial_qos = task_compute_main_thread_qos(task);

	proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS,
	                              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
 */
int
task_get_default_manager_qos(task_t task)
{
	int primordial_qos = task_compute_main_thread_qos(task);

	if (primordial_qos == THREAD_QOS_LEGACY)
		primordial_qos = THREAD_QOS_USER_INITIATED;

	return primordial_qos;
}


/*
 * Promote thread with the user level properties of 'promoter'
 * Mutexes may be held, but it's OK to take the throttle lock
 *
 * if 'new_promotion' is TRUE, this is a new promotion.
 * if FALSE, we are updating an existing promotion.
 */
static void
thread_user_promotion_promote(thread_t  thread,
                              thread_t  promoter,
                              struct promote_token* promote_token,
                              boolean_t new_promotion)
{
	struct task_pend_token pend_token = {};

	uint32_t promoter_base_pri = 0, promoter_qos = THREAD_QOS_UNSPECIFIED;

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

	/*
	 * We capture the 'promotion qos' here, which is captured
	 * before task-level clamping.
	 *
	 * This means that if the process gets unclamped while a promotion,
	 * is in effect, the owning thread ends up with the correct QoS.
	 *
	 * This does NOT work correctly across processes, as the correct QoS
	 * in one is not necessarily the correct QoS in another.
	 * When we add support for multi-process ulock boosting, we need to
	 * do something more complex.
	 */
	promoter_qos = promoter->effective_policy.thep_qos_promote;

	/* TODO: extract 'effective unclamped base pri' instead */
	promoter_base_pri = promoter->base_pri;

	thread_unlock(promoter);
	splx(s);

	/* clamp out realtime to max user pri */
	promoter_base_pri = MIN(promoter_base_pri, MAXPRI_USER);

	/* add in the saved promotion token */
	assert(promote_token->pt_basepri <= MAXPRI_USER);

	promoter_base_pri = MAX(promoter_base_pri, promote_token->pt_basepri);
	promoter_qos = MAX(promoter_qos, promote_token->pt_qos);

	/* save the max for later */
	promote_token->pt_basepri = promoter_base_pri;
	promote_token->pt_qos = promoter_qos;

	s = splsched();
	thread_lock(thread);

	if (new_promotion) {
		if (thread->user_promotions == 0) {
			assert(thread->requested_policy.thrp_qos_promote == THREAD_QOS_UNSPECIFIED);
			assert(thread->user_promotion_basepri == 0);
		}

		thread->user_promotions++;
	} else {
		assert(thread->user_promotions > 0);
	}

	uint32_t thread_qos     = thread->requested_policy.thrp_qos_promote;
	uint32_t thread_basepri = thread->user_promotion_basepri;

	uint32_t new_qos     = MAX(thread_qos, promoter_qos);
	uint32_t new_basepri = MAX(thread_basepri, promoter_base_pri);

	/* TODO: Fast path the 'new is lower than effective' case to avoid full reevaluation */
	if (thread_qos != new_qos || thread_basepri != new_basepri) {

		thread->user_promotion_basepri = new_basepri;

		pend_token.tpt_force_recompute_pri = 1;

		proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
		                                  TASK_POLICY_QOS_PROMOTE, new_qos,
		                                  0, &pend_token);
	}

	thread_unlock(thread);
	splx(s);

	thread_policy_update_complete_unlocked(thread, &pend_token);
}

/* Add a user promotion to thread */
void
thread_user_promotion_add(thread_t thread,
                          thread_t promoter,
                          struct promote_token* promote_token)
{
	thread_user_promotion_promote(thread, promoter, promote_token, TRUE);
}

/* Update an existing user promotion on thread */
void
thread_user_promotion_update(thread_t thread,
                             thread_t promoter,
                             struct promote_token* promote_token)
{
	thread_user_promotion_promote(thread, promoter, promote_token, FALSE);
}

/*
 * Drop a user promotion on thread
 * Mutexes may be held, but it's OK to take the throttle lock
 */
void
thread_user_promotion_drop(thread_t thread)
{
	struct task_pend_token pend_token = {};

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

	assert(thread->user_promotions > 0);

	if (--thread->user_promotions == 0) {
		thread->requested_policy.thrp_qos_promote = THREAD_QOS_UNSPECIFIED;
		thread->user_promotion_basepri = 0;

		pend_token.tpt_force_recompute_pri = 1;

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

	thread_unlock(thread);
	splx(s);

	thread_policy_update_complete_unlocked(thread, &pend_token);
}


/*
 * Set the thread's QoS IPC override
 * Owned by the IPC 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_ipc_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);

	uint32_t old_override = thread->requested_policy.thrp_qos_ipc_override;

	if (is_new_override) {
		if (thread->ipc_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->ipc_overrides > 0);
		assert(old_override > THREAD_QOS_UNSPECIFIED);
	}

	uint32_t new_override = MAX(old_override, qos_override);

	proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
	                                  TASK_POLICY_QOS_IPC_OVERRIDE,
	                                  new_override, 0, &pend_token);

	assert(pend_token.tpt_update_sockets == 0);

	thread_unlock(thread);
	splx(s);

	/*
	 * this is only safe after rethrottle_thread supports
	 * being called from spinlock context
	 */
	thread_policy_update_complete_unlocked(thread, &pend_token);
}

void
thread_add_ipc_override(thread_t    thread,
                        uint32_t    qos_override)
{
	thread_ipc_override(thread, qos_override, TRUE);
}

void
thread_update_ipc_override(thread_t     thread,
                           uint32_t     qos_override)
{
	thread_ipc_override(thread, qos_override, FALSE);
}

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

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

	assert(thread->ipc_overrides > 0);

	if (--thread->ipc_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_IPC_OVERRIDE, THREAD_QOS_UNSPECIFIED,
		                                  0, &pend_token);
	}

	thread_unlock(thread);
	splx(s);

	/*
	 * this is only safe after rethrottle_thread supports
	 * being called from spinlock context
	 */
	thread_policy_update_complete_unlocked(thread, &pend_token);
}

/* Get current IPC override, may be called from spinlock context */
uint32_t
thread_get_ipc_override(thread_t thread)
{
	return proc_get_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_IPC_OVERRIDE, NULL);
}