]> git.saurik.com Git - apple/xnu.git/blobdiff - osfmk/kern/thread_policy.c
xnu-7195.101.1.tar.gz
[apple/xnu.git] / osfmk / kern / thread_policy.c
index 9a82a198fbd3e5b358e4ceb85946e98c8dddcd42..e82a67b7235b39ba3e3f72dfcefe926a8befa1d7 100644 (file)
@@ -1,8 +1,8 @@
 /*
- * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
+ * 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
  * 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,
@@ -22,7 +22,7 @@
  * 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 <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_SINGLE_MUTEX_OVERRIDE 3
+
+extern zone_t thread_qos_override_zone;
+
+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.
@@ -98,28 +118,80 @@ 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);
 
-extern void proc_get_thread_policy(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);
 
-boolean_t
-thread_has_qos_policy(thread_t thread) {
-       return (proc_get_task_policy(thread->task, thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS) != THREAD_QOS_UNSPECIFIED) ? TRUE : FALSE;
+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);
+
+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;
+       }
 }
 
-kern_return_t
-thread_remove_qos_policy(thread_t thread) 
+boolean_t
+thread_has_qos_policy(thread_t thread)
 {
-       thread_qos_policy_data_t unspec_qos;
-       unspec_qos.qos_tier = THREAD_QOS_UNSPECIFIED;
-       unspec_qos.tier_importance = 0;
+       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);
 
-       return thread_policy_set_internal(thread, THREAD_QOS_POLICY, (thread_policy_t)&unspec_qos, THREAD_QOS_POLICY_COUNT);
+       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)
 {
@@ -141,28 +213,30 @@ 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;
+       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;
+       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];
@@ -184,29 +258,32 @@ thread_qos_scaled_relative_priority(int qos, int qos_relprio)
  * flag set by -qos-policy-allow boot-arg to allow
  * testing thread qos policy from userspace
  */
-boolean_t allow_qos_policy_set = FALSE;
+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_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 (thread == THREAD_NULL) {
+               return KERN_INVALID_ARGUMENT;
+       }
 
-       if (allow_qos_policy_set == FALSE) {
-               if (thread_is_static_param(thread))
-                       return (KERN_POLICY_STATIC);
+       if (!allow_qos_policy_set) {
+               if (thread_is_static_param(thread)) {
+                       return KERN_POLICY_STATIC;
+               }
 
-               if (flavor == THREAD_QOS_POLICY || flavor == THREAD_QOS_POLICY_OVERRIDE)
-                       return (KERN_INVALID_ARGUMENT);
+               if (flavor == THREAD_QOS_POLICY) {
+                       return KERN_INVALID_ARGUMENT;
+               }
        }
 
        /* Threads without static_param set reset their QoS when other policies are applied. */
@@ -236,29 +313,28 @@ thread_policy_set(
 
 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)
+       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;
-       spl_t                                   s;
+       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);
+               return KERN_TERMINATED;
        }
 
        switch (flavor) {
-
        case THREAD_EXTENDED_POLICY:
        {
-               boolean_t                               timeshare = TRUE;
+               boolean_t timeshare = TRUE;
 
                if (count >= THREAD_EXTENDED_POLICY_COUNT) {
-                       thread_extended_policy_t        info;
+                       thread_extended_policy_t info;
 
                        info = (thread_extended_policy_t)policy_info;
                        timeshare = info->timeshare;
@@ -266,7 +342,7 @@ thread_policy_set_internal(
 
                sched_mode_t mode = (timeshare == TRUE) ? TH_MODE_TIMESHARE : TH_MODE_FIXED;
 
-               s = splsched();
+               spl_t s = splsched();
                thread_lock(thread);
 
                thread_set_user_sched_mode_and_recompute_pri(thread, mode);
@@ -274,14 +350,14 @@ thread_policy_set_internal(
                thread_unlock(thread);
                splx(s);
 
-               sfi_reevaluate(thread);
+               pend_token.tpt_update_thread_sfi = 1;
 
                break;
        }
 
        case THREAD_TIME_CONSTRAINT_POLICY:
        {
-               thread_time_constraint_policy_t         info;
+               thread_time_constraint_policy_t info;
 
                if (count < THREAD_TIME_CONSTRAINT_POLICY_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
@@ -289,34 +365,36 @@ thread_policy_set_internal(
                }
 
                info = (thread_time_constraint_policy_t)policy_info;
-               if (    info->constraint < info->computation    ||
-                               info->computation > max_rt_quantum              ||
-                               info->computation < min_rt_quantum              ) {
+
+
+               if (info->constraint < info->computation ||
+                   info->computation > max_rt_quantum ||
+                   info->computation < min_rt_quantum) {
                        result = KERN_INVALID_ARGUMENT;
                        break;
                }
 
-               s = splsched();
+               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->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);
 
-               sfi_reevaluate(thread);
+               pend_token.tpt_update_thread_sfi = 1;
 
                break;
        }
 
        case THREAD_PRECEDENCE_POLICY:
        {
-               thread_precedence_policy_t              info;
+               thread_precedence_policy_t info;
 
                if (count < THREAD_PRECEDENCE_POLICY_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
@@ -324,7 +402,7 @@ thread_policy_set_internal(
                }
                info = (thread_precedence_policy_t)policy_info;
 
-               s = splsched();
+               spl_t s = splsched();
                thread_lock(thread);
 
                thread->importance = info->importance;
@@ -339,7 +417,7 @@ thread_policy_set_internal(
 
        case THREAD_AFFINITY_POLICY:
        {
-               thread_affinity_policy_t        info;
+               thread_affinity_policy_t info;
 
                if (!thread_affinity_is_supported()) {
                        result = KERN_NOT_SUPPORTED;
@@ -361,53 +439,84 @@ thread_policy_set_internal(
                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 (thread->task != 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;
-               int tqos;
-               
-               if (count < THREAD_LATENCY_QOS_POLICY_COUNT) {
+               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) {
+               if ((result = qos_throughput_policy_validate(info->thread_throughput_qos_tier)) != KERN_SUCCESS) {
                        break;
                }
 
                tqos = qos_extract(info->thread_throughput_qos_tier);
-               thread->effective_policy.t_through_qos = tqos;
-       }
+
+               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;
-               int lqos;
-               
-               if (count < THREAD_THROUGHPUT_QOS_POLICY_COUNT) {
+               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) {
+               if ((result = qos_latency_policy_validate(info->thread_latency_qos_tier)) != KERN_SUCCESS) {
                        break;
                }
 
                lqos = qos_extract(info->thread_latency_qos_tier);
-/* The expected use cases (opt-in) of per-thread latency QoS would seem to
- * preclude any requirement at present to re-evaluate timers on a thread level
- * latency QoS change.
- */
-               thread->effective_policy.t_latency_qos = lqos;
 
-       }
+               proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE,
+                   TASK_POLICY_LATENCY_QOS, lqos, 0, &pend_token);
+
                break;
+       }
 
        case THREAD_QOS_POLICY:
-       case THREAD_QOS_POLICY_OVERRIDE:
        {
                thread_qos_policy_t info = (thread_qos_policy_t)policy_info;
 
@@ -431,41 +540,9 @@ thread_policy_set_internal(
                        break;
                }
 
-               /*
-                * Going into task policy requires the task mutex,
-                * because of the way synchronization against the IO policy
-                * subsystem works.
-                *
-                * We need to move thread policy to the thread mutex instead.
-                * <rdar://problem/15831652> separate thread policy from task policy
-                */
-
-               if (flavor == THREAD_QOS_POLICY_OVERRIDE) {
-                       int strongest_override = info->qos_tier;
-
-                       if (info->qos_tier != THREAD_QOS_UNSPECIFIED &&
-                           thread->requested_policy.thrp_qos_override != THREAD_QOS_UNSPECIFIED)
-                               strongest_override = MAX(thread->requested_policy.thrp_qos_override, info->qos_tier);
-
-                       thread_mtx_unlock(thread);
-
-                       /* There is a race here. To be closed in <rdar://problem/15831652> separate thread policy from task policy */
-
-                       proc_set_task_policy(thread->task, thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_OVERRIDE, strongest_override);
-
-                       return (result);
-               }
-
-               thread_mtx_unlock(thread);
-
-               proc_set_task_policy2(thread->task, thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_AND_RELPRIO, info->qos_tier, -info->tier_importance);
+               proc_set_thread_policy_locked(thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_QOS_AND_RELPRIO,
+                   info->qos_tier, -info->tier_importance, &pend_token);
 
-               thread_mtx_lock(thread);
-               if (!thread->active) {
-                       thread_mtx_unlock(thread);
-                       return (KERN_TERMINATED);
-               }
-               
                break;
        }
 
@@ -475,287 +552,431 @@ thread_policy_set_internal(
        }
 
        thread_mtx_unlock(thread);
-       return (result);
+
+       thread_policy_update_complete_unlocked(thread, &pend_token);
+
+       return result;
 }
 
 /*
- * thread_set_mode_and_absolute_pri:
- *
- * Set scheduling policy & absolute priority for thread, for deprecated
- * thread_set_policy and thread_policy interfaces.
- *
  * Note that there is no implemented difference between POLICY_RR and POLICY_FIFO.
  * Both result in FIXED mode scheduling.
- *
- * Called with thread mutex locked.
  */
-kern_return_t
-thread_set_mode_and_absolute_pri(
-       thread_t                thread,
-       integer_t               policy,
-       integer_t               priority)
+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)
 {
-       spl_t s;
-       sched_mode_t mode;
        kern_return_t kr = KERN_SUCCESS;
 
-       if (thread_is_static_param(thread))
-               return (KERN_POLICY_STATIC);
+       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)
-               return (KERN_SUCCESS);
+       if (thread->policy_reset) {
+               kr = KERN_SUCCESS;
+               goto unlock;
+       }
 
-       /* Setting legacy policies on threads kills the current QoS */
-       if (thread->requested_policy.thrp_qos != THREAD_QOS_UNSPECIFIED) {
-               thread_mtx_unlock(thread);
+       sched_mode_t old_mode = thread->sched_mode;
 
-               kr = thread_remove_qos_policy(thread);
+       /*
+        * Reverse engineer and apply the correct importance value
+        * from the requested absolute priority value.
+        *
+        * TODO: Store the absolute priority value instead
+        */
 
-               thread_mtx_lock(thread);
-               if (!thread->active) {
-                       return (KERN_TERMINATED);
-               }
+       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;
        }
 
-       switch (policy) {
-               case POLICY_TIMESHARE:
-                       mode = TH_MODE_TIMESHARE;
-                       break;
-               case POLICY_RR:
-               case POLICY_FIFO:
-                       mode = TH_MODE_FIXED;
-                       break;
-               default:
-                       panic("unexpected sched policy: %d", policy);
-                       break;
+       priority += thread->task_priority;
+
+       if (priority > thread->max_priority) {
+               priority = thread->max_priority;
+       } else if (priority < MINPRI) {
+               priority = MINPRI;
        }
 
-       s = splsched();
+       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);
 
-       /* 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)) {
+       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) {
                /*
-                * Reverse engineer and apply the correct importance value
-                * from the requested absolute priority value.
+                * 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);
+       }
 
-               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;
+       thread_unlock(thread);
+       splx(s);
 
-               if (priority > thread->max_priority)
-                       priority = thread->max_priority;
-               else if (priority < MINPRI)
-                       priority = MINPRI;
+       return ast != 0;
+}
 
-               thread->importance = priority - thread->task_priority;
+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_set_user_sched_mode_and_recompute_pri(thread, mode);
+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);
 
-       sfi_reevaluate(thread);
-
-       return (kr);
+       thread_policy_update_complete_unlocked(thread, &pend_token);
 }
 
 /*
- * Set the thread's requested mode and recompute priority
- * Called with thread mutex and thread locked
+ * private interface for pthread workqueues
  *
- * 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?
+ * Set scheduling policy & absolute priority for thread
+ * May be called with spinlocks held
+ * Thread mutex lock is held
  */
-static void
-thread_set_user_sched_mode_and_recompute_pri(thread_t thread, sched_mode_t mode)
+void
+thread_set_workq_override(thread_t thread, uint32_t qos)
 {
-       if (thread->policy_reset)
-               return;
+       struct task_pend_token pend_token = {};
 
-       boolean_t removed = thread_run_queue_remove(thread);
+       assert(qos < THREAD_QOS_LAST);
 
-       /*
-        * 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);
+       spl_t s = splsched();
+       thread_lock(thread);
 
-       thread_recompute_priority(thread);
+       proc_set_thread_policy_spinlocked(thread, TASK_POLICY_ATTRIBUTE,
+           TASK_POLICY_QOS_WORKQ_OVERRIDE, qos, 0, &pend_token);
 
-       if (removed)
-               thread_run_queue_reinsert(thread, SCHED_TAILQ);
+       assert(pend_token.tpt_update_sockets == 0);
+
+       thread_unlock(thread);
+       splx(s);
+
+       thread_policy_update_complete_unlocked(thread, &pend_token);
 }
 
-/* called with task lock locked */
+/*
+ * 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_recompute_qos(thread_t thread) {
-       spl_t s;
+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);
 
-       thread_mtx_lock(thread);
+       assert(qos < THREAD_QOS_LAST);
+       assert(thread->static_param);
 
-       if (!thread->active) {
-               thread_mtx_unlock(thread);
+       if (!thread->static_param || !thread->active) {
                return;
        }
 
-       s = splsched();
+       spl_t s = splsched();
        thread_lock(thread);
 
-       thread_recompute_priority(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);
 
-       thread_mtx_unlock(thread);
-}
+       /* Concern: this doesn't hold the mutex... */
 
-/* called with task lock locked and thread_mtx_lock locked */
-void
-thread_update_qos_cpu_time(thread_t thread, boolean_t lock_needed)
-{
-       uint64_t last_qos_change_balance;
-       ledger_amount_t thread_balance_credit;
-       ledger_amount_t thread_balance_debit;
-       ledger_amount_t effective_qos_time;
-       uint64_t ctime;
-       uint64_t remainder = 0, consumed = 0;
-       processor_t             processor;
-       spl_t s;
-       kern_return_t kr;
+       __assert_only kern_return_t kr;
+       kr = thread_set_mode_and_absolute_pri_internal(thread, mode, priority,
+           &pend_token);
+       assert(kr == KERN_SUCCESS);
 
-       if (lock_needed) {
-               s = splsched();
-               thread_lock(thread);
+       if (pend_token.tpt_update_thread_sfi) {
+               sfi_reevaluate(thread);
        }
-       
-       /*
-        * Calculation of time elapsed by the thread in the current qos.
-        * Following is the timeline which shows all the variables used in the calculation below.
-        *
-        *       thread ledger      thread ledger
-        *      cpu_time_last_qos     cpu_time
-        *              |                |<-   consumed  ->|<- remainder  ->|
-        * timeline  ----------------------------------------------------------->
-        *                               |                 |                |
-        *                            thread_dispatch    ctime           quantum end
-        *
-        *              |<-----  effective qos time  ----->|
-        */
-       
-       /* 
-        * Calculate time elapsed since last qos change on this thread.
-        * For cpu time on thread ledger, do not use ledger_get_balance,
-        * only use credit field of ledger, since
-        * debit is used by per thread cpu limits and is not zero.
-        */
-       kr = ledger_get_entries(thread->t_threadledger, thread_ledgers.cpu_time, &thread_balance_credit, &thread_balance_debit);
-       if (kr != KERN_SUCCESS)
-               goto out;
-       last_qos_change_balance = thread->cpu_time_last_qos;
+}
+
+/*
+ * 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);
 
        /*
-        * If thread running on CPU, calculate time elapsed since this thread was last dispatched on cpu.
-        * The thread ledger is only updated at context switch, the time since last context swicth is not 
-        * updated in the thread ledger cpu time.
+        * 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.
         */
-       processor = thread->last_processor;
-       if ((processor != PROCESSOR_NULL) && (processor->state == PROCESSOR_RUNNING) &&
-                  (processor->active_thread == thread)) {
-               ctime = mach_absolute_time();
-       
-               if (processor->quantum_end > ctime)
-                       remainder = processor->quantum_end - ctime;
+       if (thread->sched_flags & TH_SFLAG_DEMOTED_MASK) {
+               thread->saved_mode = mode;
+       } else {
+               sched_set_thread_mode(thread, mode);
+       }
+
+       thread_recompute_priority(thread);
 
-               consumed = thread->quantum_remaining - remainder;
+       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;
+
        /*
-        * There can be multiple qos change in a quantum and in that case the cpu_time_last_qos will
-        * lie between cpu_time marker and ctime marker shown below. The output of 
-        * thread_balance - last_qos_change_balance will be negative in such case, but overall outcome
-        * when consumed is added to it would be positive.
+        * 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.
         *
-        *          thread ledger
-        *            cpu_time
-        *               |<------------  consumed    --------->|<- remainder  ->|
-        * timeline  ----------------------------------------------------------->
-        *               |              |                      |                |
-        *         thread_dispatch  thread ledger            ctime           quantum end
-        *                          cpu_time_last_qos
+        * 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.
         *
-        *                              |<-effective qos time->|
+        * TODO: There should be a function for this in timer.c
         */
-       effective_qos_time = (ledger_amount_t) consumed;
-       effective_qos_time += thread_balance_credit - last_qos_change_balance;
 
-       if (lock_needed) {
-               thread_unlock(thread);
-               splx(s);
-       }
+       timer_sum = timer_grab(&thread->user_timer);
+       timer_sum += timer_grab(&thread->system_timer);
+       timer_delta = timer_sum - thread->vtimer_qos_save;
 
-       if (effective_qos_time < 0)
-               return;
+       thread->vtimer_qos_save = timer_sum;
 
-       thread->cpu_time_last_qos += (uint64_t)effective_qos_time;
+       uint64_t* task_counter = NULL;
 
-       /*
-        * Update the task-level qos stats. Its safe to perform operations on these fields, since we 
-        * hold the task lock.
-        */
+       /* 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_DEFAULT:
-               thread->task->cpu_time_qos_stats.cpu_time_qos_default += effective_qos_time;
-               break;
+       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);
+       }
 
-       case THREAD_QOS_MAINTENANCE:
-               thread->task->cpu_time_qos_stats.cpu_time_qos_maintenance += effective_qos_time;
-               break;
+       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);
+       }
 
-       case THREAD_QOS_BACKGROUND:
-               thread->task->cpu_time_qos_stats.cpu_time_qos_background += effective_qos_time;
-               break;
+       OSAddAtomic64(timer_delta, task_counter);
+}
 
-       case THREAD_QOS_UTILITY:
-               thread->task->cpu_time_qos_stats.cpu_time_qos_utility += effective_qos_time;
-               break;
+/*
+ * called with no thread locks held
+ * may hold task lock
+ */
+void
+thread_update_qos_cpu_time(thread_t thread)
+{
+       thread_mtx_lock(thread);
 
-       case THREAD_QOS_LEGACY:
-               thread->task->cpu_time_qos_stats.cpu_time_qos_legacy += effective_qos_time;
-               break;
-       
-       case THREAD_QOS_USER_INITIATED:
-               thread->task->cpu_time_qos_stats.cpu_time_qos_user_initiated += effective_qos_time;
-               break;
+       spl_t s = splsched();
+       thread_lock(thread);
 
-       case THREAD_QOS_USER_INTERACTIVE:
-               thread->task->cpu_time_qos_stats.cpu_time_qos_user_interactive += effective_qos_time;
-               break;
-       }
+       thread_update_qos_cpu_time_locked(thread);
 
-       return;
+       thread_unlock(thread);
+       splx(s);
 
-out:
-       if (lock_needed) {
-               thread_unlock(thread);
-               splx(s);
-       }
+       thread_mtx_unlock(thread);
 }
 
 /*
@@ -763,21 +984,25 @@ out:
  *
  * Called with thread_lock and thread mutex held.
  */
+extern thread_t vm_pageout_scan_thread;
+extern boolean_t vps_dynamic_priority_enabled;
+
 void
 thread_recompute_priority(
-       thread_t                thread)
+       thread_t                thread)
 {
-       integer_t               priority;
+       integer_t               priority;
 
-       if (thread->policy_reset)
+       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.qos_ui_is_urgent;
+               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;
 
@@ -792,68 +1017,119 @@ thread_recompute_priority(
                        qos_scaled_relprio += 1;
                }
 
+               /* TODO: factor in renice priority here? */
+
                priority += qos_scaled_relprio;
        } else {
-               if (thread->importance > MAXPRI)
+               if (thread->importance > MAXPRI) {
                        priority = MAXPRI;
-               else if (thread->importance < -MAXPRI)
+               } else if (thread->importance < -MAXPRI) {
                        priority = -MAXPRI;
-               else
+               } 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)
+           thread->sched_flags & TH_SFLAG_FAILSAFE) {
                priority = DEPRESSPRI;
-
-       if (thread->effective_policy.terminated == TRUE && priority < thread->task_priority) {
-               priority = thread->task_priority;
        }
 
-       if (priority > thread->max_priority)
-               priority = thread->max_priority;
-       else if (priority < MINPRI)
-               priority = MINPRI;
+       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 thread mutex held */
+/* Called with the task lock held, but not the thread mutex or spinlock */
 void
-thread_task_priority(
-       thread_t                thread,
-       integer_t               priority,
-       integer_t               max_priority)
+thread_policy_update_tasklocked(
+       thread_t           thread,
+       integer_t          priority,
+       integer_t          max_priority,
+       task_pend_token_t  pend_token)
 {
-       spl_t s;
-
-       assert(thread != THREAD_NULL);
+       thread_mtx_lock(thread);
 
-       if (!thread->active || thread->policy_reset)
+       if (!thread->active || thread->policy_reset) {
+               thread_mtx_unlock(thread);
                return;
+       }
 
-       s = splsched();
+       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;
+       assert(priority >= INT16_MIN && priority <= INT16_MAX);
+       thread->task_priority = (int16_t)priority;
 
-       /* A thread is 'throttled' when its max priority is below MAXPRI_THROTTLE */
-       if ((max_priority > MAXPRI_THROTTLE) && (old_max_priority <= MAXPRI_THROTTLE)) {
-               sched_set_thread_throttled(thread, FALSE);
-       } else if ((max_priority <= MAXPRI_THROTTLE) && (old_max_priority > MAXPRI_THROTTLE)) {
-               sched_set_thread_throttled(thread, TRUE);
+       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_recompute_priority(thread);
+       thread_policy_update_spinlocked(thread, true, pend_token);
 
        thread_unlock(thread);
        splx(s);
+
+       thread_mtx_unlock(thread);
 }
 
 /*
@@ -864,28 +1140,22 @@ thread_task_priority(
  */
 void
 thread_policy_reset(
-       thread_t                thread)
+       thread_t                thread)
 {
-       spl_t           s;
+       spl_t           s;
 
        assert(thread == current_thread());
 
        s = splsched();
        thread_lock(thread);
 
-       assert_thread_sched_count(thread);
-
-       if (thread->sched_flags & TH_SFLAG_FAILSAFE)
+       if (thread->sched_flags & TH_SFLAG_FAILSAFE) {
                sched_thread_mode_undemote(thread, TH_SFLAG_FAILSAFE);
+       }
 
-       assert_thread_sched_count(thread);
-
-       if (thread->sched_flags & TH_SFLAG_THROTTLED)
-               sched_set_thread_throttled(thread, FALSE);
-
-       assert_thread_sched_count(thread);
-
-       assert(thread->BG_COUNT == 0);
+       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));
@@ -899,13 +1169,10 @@ thread_policy_reset(
 
        thread->importance = 0;
 
-       sched_set_thread_base_priority(thread, thread->task_priority);
-
        /* Prevent further changes to thread base priority or mode */
        thread->policy_reset = 1;
 
-       assert(thread->BG_COUNT == 0);
-       assert_thread_sched_count(thread);
+       sched_set_thread_base_priority(thread, thread->task_priority);
 
        thread_unlock(thread);
        splx(s);
@@ -913,51 +1180,51 @@ thread_policy_reset(
 
 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)
+       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;
-       spl_t                                   s;
+       kern_return_t                   result = KERN_SUCCESS;
 
-       if (thread == THREAD_NULL)
-               return (KERN_INVALID_ARGUMENT);
+       if (thread == THREAD_NULL) {
+               return KERN_INVALID_ARGUMENT;
+       }
 
        thread_mtx_lock(thread);
        if (!thread->active) {
                thread_mtx_unlock(thread);
 
-               return (KERN_TERMINATED);
+               return KERN_TERMINATED;
        }
 
        switch (flavor) {
-
        case THREAD_EXTENDED_POLICY:
        {
-               boolean_t               timeshare = TRUE;
+               boolean_t               timeshare = TRUE;
 
                if (!(*get_default)) {
-                       s = splsched();
+                       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))
+                       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
+                               } else {
                                        timeshare = (thread->saved_mode == TH_MODE_TIMESHARE) != 0;
-                       }
-                       else
+                               }
+                       } else {
                                *get_default = TRUE;
+                       }
 
                        thread_unlock(thread);
                        splx(s);
                }
 
                if (*count >= THREAD_EXTENDED_POLICY_COUNT) {
-                       thread_extended_policy_t        info;
+                       thread_extended_policy_t        info;
 
                        info = (thread_extended_policy_t)policy_info;
                        info->timeshare = timeshare;
@@ -968,7 +1235,7 @@ thread_policy_get(
 
        case THREAD_TIME_CONSTRAINT_POLICY:
        {
-               thread_time_constraint_policy_t         info;
+               thread_time_constraint_policy_t         info;
 
                if (*count < THREAD_TIME_CONSTRAINT_POLICY_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
@@ -978,18 +1245,18 @@ thread_policy_get(
                info = (thread_time_constraint_policy_t)policy_info;
 
                if (!(*get_default)) {
-                       s = splsched();
+                       spl_t s = splsched();
                        thread_lock(thread);
 
-                       if (    (thread->sched_mode == TH_MODE_REALTIME)        ||
-                                       (thread->saved_mode == TH_MODE_REALTIME)                ) {
+                       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
+                       } else {
                                *get_default = TRUE;
+                       }
 
                        thread_unlock(thread);
                        splx(s);
@@ -1002,12 +1269,13 @@ thread_policy_get(
                        info->preemptible = TRUE;
                }
 
+
                break;
        }
 
        case THREAD_PRECEDENCE_POLICY:
        {
-               thread_precedence_policy_t              info;
+               thread_precedence_policy_t              info;
 
                if (*count < THREAD_PRECEDENCE_POLICY_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
@@ -1017,23 +1285,23 @@ thread_policy_get(
                info = (thread_precedence_policy_t)policy_info;
 
                if (!(*get_default)) {
-                       s = splsched();
+                       spl_t s = splsched();
                        thread_lock(thread);
 
                        info->importance = thread->importance;
 
                        thread_unlock(thread);
                        splx(s);
-               }
-               else
+               } else {
                        info->importance = 0;
+               }
 
                break;
        }
 
        case THREAD_AFFINITY_POLICY:
        {
-               thread_affinity_policy_t                info;
+               thread_affinity_policy_t                info;
 
                if (!thread_affinity_is_supported()) {
                        result = KERN_NOT_SUPPORTED;
@@ -1046,17 +1314,18 @@ thread_policy_get(
 
                info = (thread_affinity_policy_t)policy_info;
 
-               if (!(*get_default))
+               if (!(*get_default)) {
                        info->affinity_tag = thread_affinity_get(thread);
-               else
+               } else {
                        info->affinity_tag = THREAD_AFFINITY_TAG_NULL;
+               }
 
                break;
        }
 
        case THREAD_POLICY_STATE:
        {
-               thread_policy_state_t           info;
+               thread_policy_state_t           info;
 
                if (*count < THREAD_POLICY_STATE_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
@@ -1069,21 +1338,27 @@ thread_policy_get(
                        break;
                }
 
-               info = (thread_policy_state_t)policy_info;
+               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);
 
-                       /*
-                        * Unlock the thread mutex and directly return.
-                        * This is necessary because proc_get_thread_policy()
-                        * takes the task lock.
-                        */
-                       thread_mtx_unlock(thread);
-                       proc_get_thread_policy(thread, info);
-                       return (result);
+                       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;
@@ -1092,11 +1367,11 @@ thread_policy_get(
 
                break;
        }
-       
+
        case THREAD_LATENCY_QOS_POLICY:
        {
                thread_latency_qos_policy_t info = (thread_latency_qos_policy_t) policy_info;
-               uint32_t plqos;
+               thread_latency_qos_t plqos;
 
                if (*count < THREAD_LATENCY_QOS_POLICY_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
@@ -1106,7 +1381,7 @@ thread_policy_get(
                if (*get_default) {
                        plqos = 0;
                } else {
-                       plqos = thread->effective_policy.t_latency_qos;
+                       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);
@@ -1116,7 +1391,7 @@ thread_policy_get(
        case THREAD_THROUGHPUT_QOS_POLICY:
        {
                thread_throughput_qos_policy_t info = (thread_throughput_qos_policy_t) policy_info;
-               uint32_t ptqos;
+               thread_throughput_qos_t ptqos;
 
                if (*count < THREAD_THROUGHPUT_QOS_POLICY_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
@@ -1126,7 +1401,7 @@ thread_policy_get(
                if (*get_default) {
                        ptqos = 0;
                } else {
-                       ptqos = thread->effective_policy.t_through_qos;
+                       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);
@@ -1134,7 +1409,6 @@ thread_policy_get(
        break;
 
        case THREAD_QOS_POLICY:
-       case THREAD_QOS_POLICY_OVERRIDE:
        {
                thread_qos_policy_t info = (thread_qos_policy_t)policy_info;
 
@@ -1144,14 +1418,11 @@ thread_policy_get(
                }
 
                if (!(*get_default)) {
-                       if (flavor == THREAD_QOS_POLICY_OVERRIDE) {
-                               info->qos_tier = thread->requested_policy.thrp_qos_override;
-                               /* TODO: handle importance overrides */
-                               info->tier_importance = 0;
-                       } else {
-                               info->qos_tier = thread->requested_policy.thrp_qos;
-                               info->tier_importance = thread->importance;
-                       }
+                       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;
@@ -1167,44 +1438,1715 @@ thread_policy_get(
 
        thread_mtx_unlock(thread);
 
-       return (result);
+       return result;
 }
 
-static volatile uint64_t unique_work_interval_id = 1; /* Start at 1, 0 is not a valid work interval ID */
+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 = {};
 
-kern_return_t
-thread_policy_create_work_interval(
-       thread_t                thread,
-       uint64_t                *work_interval_id)
+       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)
 {
-       thread_mtx_lock(thread);
-       if (thread->work_interval_id) {
-               /* already assigned a work interval ID */
-               thread_mtx_unlock(thread);
-               return (KERN_INVALID_VALUE);
-       }
+       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->work_interval_id = OSIncrementAtomic64((volatile int64_t *)&unique_work_interval_id);
-       *work_interval_id = thread->work_interval_id;
+       thread_policy_update_internal_spinlocked(thread, recompute_priority, pend_token);
 
-       thread_mtx_unlock(thread);
-       return KERN_SUCCESS;
+       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);
 }
 
-kern_return_t
-thread_policy_destroy_work_interval(
-       thread_t                thread,
-       uint64_t                work_interval_id)
+
+
+/*
+ * 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)
 {
-       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);
+       /*
+        * 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) {
+               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);
        }
 
-       thread->work_interval_id = 0;
+       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;
+       }
 
-       thread_mtx_unlock(thread);
-       return KERN_SUCCESS;
+       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(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);
+       }
+
+       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 ||
+                   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_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(thread->task == 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 == thread->task);
+       }
+
+       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(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);
+
+       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);
 }