/*
- * Copyright (c) 2000-2008 Apple Inc. All rights reserved.
+ * Copyright (c) 2000-2010 Apple Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
/*
*/
/*
- * File: clock_prim.c
+ * File: priority.c
* Author: Avadis Tevanian, Jr.
* Date: 1986
*
- * Clock primitives.
+ * Priority related scheduler bits.
*/
#include <mach/boolean.h>
#include <kern/host.h>
#include <kern/mach_param.h>
#include <kern/sched.h>
+#include <sys/kdebug.h>
#include <kern/spl.h>
#include <kern/thread.h>
#include <kern/processor.h>
+#include <kern/ledger.h>
#include <machine/machparam.h>
+#include <kern/machine.h>
+
+#ifdef CONFIG_MACH_APPROXIMATE_TIME
+#include <machine/commpage.h> /* for commpage_update_mach_approximate_time */
+#endif
+
+static void sched_update_thread_bucket(thread_t thread);
/*
* thread_quantum_expire:
processor_t processor = p0;
thread_t thread = p1;
ast_t preempt;
+ uint64_t ctime;
+ int urgency;
+ uint64_t ignore1, ignore2;
- thread_lock(thread);
+ assert(processor == current_processor());
+ assert(thread == current_thread());
+
+ KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED, MACH_SCHED_QUANTUM_EXPIRED) | DBG_FUNC_START, 0, 0, 0, 0, 0);
+
+ SCHED_STATS_QUANTUM_TIMER_EXPIRATION(processor);
/*
- * Check for fail-safe trip.
+ * We bill CPU time to both the individual thread and its task.
+ *
+ * Because this balance adjustment could potentially attempt to wake this very
+ * thread, we must credit the ledger before taking the thread lock. The ledger
+ * pointers are only manipulated by the thread itself at the ast boundary.
+ *
+ * TODO: This fails to account for the time between when the timer was armed and when it fired.
+ * It should be based on the system_timer and running a thread_timer_event operation here.
*/
- if (!(thread->sched_mode & (TH_MODE_TIMESHARE|TH_MODE_PROMOTED))) {
- uint64_t new_computation;
+ ledger_credit(thread->t_ledger, task_ledgers.cpu_time, thread->quantum_remaining);
+ ledger_credit(thread->t_threadledger, thread_ledgers.cpu_time, thread->quantum_remaining);
+#ifdef CONFIG_BANK
+ if (thread->t_bankledger) {
+ ledger_credit(thread->t_bankledger, bank_ledgers.cpu_time,
+ (thread->quantum_remaining - thread->t_deduct_bank_ledger_time));
+ }
+ thread->t_deduct_bank_ledger_time = 0;
+#endif
- new_computation = processor->quantum_end;
- new_computation -= thread->computation_epoch;
- if (new_computation + thread->computation_metered >
- max_unsafe_computation) {
+ ctime = mach_absolute_time();
- if (thread->sched_mode & TH_MODE_REALTIME) {
- thread->priority = DEPRESSPRI;
+#ifdef CONFIG_MACH_APPROXIMATE_TIME
+ commpage_update_mach_approximate_time(ctime);
+#endif
- thread->safe_mode |= TH_MODE_REALTIME;
- thread->sched_mode &= ~TH_MODE_REALTIME;
- }
+ thread_lock(thread);
- sched_share_incr();
+ /*
+ * We've run up until our quantum expiration, and will (potentially)
+ * continue without re-entering the scheduler, so update this now.
+ */
+ processor->last_dispatch = ctime;
+ thread->last_run_time = ctime;
- thread->safe_release = sched_tick + sched_safe_duration;
- thread->sched_mode |= (TH_MODE_FAILSAFE|TH_MODE_TIMESHARE);
+ /*
+ * Check for fail-safe trip.
+ */
+ if ((thread->sched_mode == TH_MODE_REALTIME || thread->sched_mode == TH_MODE_FIXED) &&
+ !(thread->sched_flags & TH_SFLAG_PROMOTED_MASK) &&
+ !(thread->options & TH_OPT_SYSTEM_CRITICAL)) {
+ uint64_t new_computation;
+
+ new_computation = ctime - thread->computation_epoch;
+ new_computation += thread->computation_metered;
+ if (new_computation > max_unsafe_computation) {
+ KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED, MACH_FAILSAFE)|DBG_FUNC_NONE,
+ (uintptr_t)thread->sched_pri, (uintptr_t)thread->sched_mode, 0, 0, 0);
+
+ thread->safe_release = ctime + sched_safe_duration;
+
+ sched_thread_mode_demote(thread, TH_SFLAG_FAILSAFE);
}
}
-
+
/*
* Recompute scheduled priority if appropriate.
*/
- if (thread->sched_stamp != sched_tick)
- update_priority(thread);
+ if (SCHED(can_update_priority)(thread))
+ SCHED(update_priority)(thread);
else
- if (thread->sched_mode & TH_MODE_TIMESHARE) {
- register uint32_t delta;
-
- thread_timer_delta(thread, delta);
+ SCHED(lightweight_update_priority)(thread);
- /*
- * Accumulate timesharing usage only
- * during contention for processor
- * resources.
- */
- if (thread->pri_shift < INT8_MAX)
- thread->sched_usage += delta;
-
- thread->cpu_delta += delta;
-
- /*
- * Adjust the scheduled priority if
- * the thread has not been promoted
- * and is not depressed.
- */
- if ( !(thread->sched_mode & TH_MODE_PROMOTED) &&
- !(thread->sched_mode & TH_MODE_ISDEPRESSED) )
- compute_my_priority(thread);
- }
+ if (thread->sched_mode != TH_MODE_REALTIME)
+ SCHED(quantum_expire)(thread);
processor->current_pri = thread->sched_pri;
+ processor->current_thmode = thread->sched_mode;
+
+ /* Tell platform layer that we are still running this thread */
+ urgency = thread_get_urgency(thread, &ignore1, &ignore2);
+ machine_thread_going_on_core(thread, urgency, 0);
/*
* This quantum is up, give this thread another.
*/
- if (first_timeslice(processor))
- processor->timeslice--;
+ processor->first_timeslice = FALSE;
thread_quantum_init(thread);
- processor->quantum_end += thread->current_quantum;
- timer_call_enter1(&processor->quantum_timer,
- thread, processor->quantum_end);
+
+ /* Reload precise timing global policy to thread-local policy */
+ thread->precise_user_kernel_time = use_precise_user_kernel_time(thread);
+
+ /*
+ * Since non-precise user/kernel time doesn't update the state/thread timer
+ * during privilege transitions, synthesize an event now.
+ */
+ if (!thread->precise_user_kernel_time) {
+ timer_switch(PROCESSOR_DATA(processor, current_state),
+ ctime,
+ PROCESSOR_DATA(processor, current_state));
+ timer_switch(PROCESSOR_DATA(processor, thread_timer),
+ ctime,
+ PROCESSOR_DATA(processor, thread_timer));
+ }
+
+ processor->quantum_end = ctime + thread->quantum_remaining;
/*
* Context switch check.
*/
- if ((preempt = csw_check(thread, processor)) != AST_NONE)
+ if ((preempt = csw_check(processor, AST_QUANTUM)) != AST_NONE)
ast_on(preempt);
- else {
- processor_set_t pset = processor->processor_set;
- pset_lock(pset);
+ thread_unlock(thread);
+
+ timer_call_enter1(&processor->quantum_timer, thread,
+ processor->quantum_end, TIMER_CALL_SYS_CRITICAL | TIMER_CALL_LOCAL);
+
+#if defined(CONFIG_SCHED_TIMESHARE_CORE)
+ sched_timeshare_consider_maintenance(ctime);
+#endif /* CONFIG_SCHED_TIMESHARE_CORE */
+
+
+ KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED, MACH_SCHED_QUANTUM_EXPIRED) | DBG_FUNC_END, preempt, 0, 0, 0, 0);
+}
+
+/*
+ * sched_set_thread_base_priority:
+ *
+ * Set the base priority of the thread
+ * and reset its scheduled priority.
+ *
+ * This is the only path to change base_pri.
+ *
+ * Called with the thread locked.
+ */
+void
+sched_set_thread_base_priority(thread_t thread, int priority)
+{
+ assert(priority >= MINPRI);
+
+ if (thread->sched_mode == TH_MODE_REALTIME)
+ assert(priority <= BASEPRI_RTQUEUES);
+ else
+ assert(priority < BASEPRI_RTQUEUES);
+
+ thread->base_pri = priority;
+
+ sched_update_thread_bucket(thread);
+
+ thread_recompute_sched_pri(thread, FALSE);
+}
+
+/*
+ * thread_recompute_sched_pri:
+ *
+ * Reset the scheduled priority of the thread
+ * according to its base priority if the
+ * thread has not been promoted or depressed.
+ *
+ * This is the standard way to push base_pri changes into sched_pri,
+ * or to recalculate the appropriate sched_pri after clearing
+ * a promotion or depression.
+ *
+ * Called at splsched with the thread locked.
+ */
+void
+thread_recompute_sched_pri(
+ thread_t thread,
+ boolean_t override_depress)
+{
+ int priority;
- pset_pri_hint(pset, processor, processor->current_pri);
+ if (thread->sched_mode == TH_MODE_TIMESHARE)
+ priority = SCHED(compute_timeshare_priority)(thread);
+ else
+ priority = thread->base_pri;
- pset_unlock(pset);
+ if ((!(thread->sched_flags & TH_SFLAG_PROMOTED_MASK) || (priority > thread->sched_pri)) &&
+ (!(thread->sched_flags & TH_SFLAG_DEPRESSED_MASK) || override_depress)) {
+ set_sched_pri(thread, priority);
}
+}
- thread_unlock(thread);
+void
+sched_default_quantum_expire(thread_t thread __unused)
+{
+ /*
+ * No special behavior when a timeshare, fixed, or realtime thread
+ * uses up its entire quantum
+ */
+}
+
+#if defined(CONFIG_SCHED_TIMESHARE_CORE)
+
+/*
+ * lightweight_update_priority:
+ *
+ * Update the scheduled priority for
+ * a timesharing thread.
+ *
+ * Only for use on the current thread.
+ *
+ * Called with the thread locked.
+ */
+void
+lightweight_update_priority(thread_t thread)
+{
+ assert(thread->runq == PROCESSOR_NULL);
+ assert(thread == current_thread());
+
+ if (thread->sched_mode == TH_MODE_TIMESHARE) {
+ int priority;
+ uint32_t delta;
+
+ thread_timer_delta(thread, delta);
+
+ /*
+ * Accumulate timesharing usage only
+ * during contention for processor
+ * resources.
+ */
+ if (thread->pri_shift < INT8_MAX)
+ thread->sched_usage += delta;
+
+ thread->cpu_delta += delta;
+
+ priority = sched_compute_timeshare_priority(thread);
+
+ /*
+ * Adjust the scheduled priority like thread_recompute_sched_pri,
+ * except with the benefit of knowing the thread is on this core.
+ */
+ if ((!(thread->sched_flags & TH_SFLAG_PROMOTED_MASK) || (priority > thread->sched_pri)) &&
+ (!(thread->sched_flags & TH_SFLAG_DEPRESSED_MASK)) &&
+ priority != thread->sched_pri) {
+
+ thread->sched_pri = priority;
+
+ KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED, MACH_SCHED_CHANGE_PRIORITY),
+ (uintptr_t)thread_tid(thread),
+ thread->base_pri,
+ thread->sched_pri,
+ 0, /* eventually, 'reason' */
+ 0);
+ }
+ }
}
/*
};
/*
- * do_priority_computation:
+ * sched_compute_timeshare_priority:
*
* Calculate the timesharing priority based upon usage and load.
*/
-#define do_priority_computation(thread, pri) \
- MACRO_BEGIN \
- (pri) = (thread)->priority /* start with base priority */ \
- - ((thread)->sched_usage >> (thread)->pri_shift); \
- if ((pri) < MINPRI_USER) \
- (pri) = MINPRI_USER; \
- else \
- if ((pri) > MAXPRI_KERNEL) \
- (pri) = MAXPRI_KERNEL; \
- MACRO_END
+extern int sched_pri_decay_band_limit;
-/*
- * set_priority:
- *
- * Set the base priority of the thread
- * and reset its scheduled priority.
- *
- * Called with the thread locked.
- */
-void
-set_priority(
- register thread_t thread,
- register int priority)
-{
- thread->priority = priority;
- compute_priority(thread, FALSE);
-}
-/*
- * compute_priority:
- *
- * Reset the scheduled priority of the thread
- * according to its base priority if the
- * thread has not been promoted or depressed.
- *
- * Called with the thread locked.
- */
-void
-compute_priority(
- register thread_t thread,
- boolean_t override_depress)
+int
+sched_compute_timeshare_priority(thread_t thread)
{
- register int priority;
+ /* start with base priority */
+ int priority = thread->base_pri - (thread->sched_usage >> thread->pri_shift);
- if ( !(thread->sched_mode & TH_MODE_PROMOTED) &&
- (!(thread->sched_mode & TH_MODE_ISDEPRESSED) ||
- override_depress ) ) {
- if (thread->sched_mode & TH_MODE_TIMESHARE)
- do_priority_computation(thread, priority);
- else
- priority = thread->priority;
+ if (priority < MINPRI_USER)
+ priority = MINPRI_USER;
+ else if (priority > MAXPRI_KERNEL)
+ priority = MAXPRI_KERNEL;
- set_sched_pri(thread, priority);
- }
+ return priority;
}
+
/*
- * compute_my_priority:
- *
- * Reset the scheduled priority for
- * a timesharing thread.
+ * can_update_priority
*
- * Only for use on the current thread
- * if timesharing and not depressed.
+ * Make sure we don't do re-dispatches more frequently than a scheduler tick.
*
* Called with the thread locked.
*/
-void
-compute_my_priority(
- register thread_t thread)
+boolean_t
+can_update_priority(
+ thread_t thread)
{
- register int priority;
-
- do_priority_computation(thread, priority);
- assert(thread->runq == PROCESSOR_NULL);
- thread->sched_pri = priority;
+ if (sched_tick == thread->sched_stamp)
+ return (FALSE);
+ else
+ return (TRUE);
}
/*
*/
void
update_priority(
- register thread_t thread)
+ thread_t thread)
{
- register unsigned ticks;
- register uint32_t delta;
+ uint32_t ticks, delta;
ticks = sched_tick - thread->sched_stamp;
assert(ticks != 0);
+
thread->sched_stamp += ticks;
- thread->pri_shift = sched_pri_shift;
+
+ thread->pri_shift = sched_pri_shifts[thread->th_sched_bucket];
+
+ /* If requested, accelerate aging of sched_usage */
+ if (sched_decay_usage_age_factor > 1)
+ ticks *= sched_decay_usage_age_factor;
/*
* Gather cpu usage data.
*/
thread_timer_delta(thread, delta);
if (ticks < SCHED_DECAY_TICKS) {
- register struct shift_data *shiftp;
-
/*
* Accumulate timesharing usage only
* during contention for processor
thread->cpu_usage += delta + thread->cpu_delta;
thread->cpu_delta = 0;
- shiftp = &sched_decay_shifts[ticks];
+ struct shift_data *shiftp = &sched_decay_shifts[ticks];
+
if (shiftp->shift2 > 0) {
- thread->cpu_usage =
- (thread->cpu_usage >> shiftp->shift1) +
- (thread->cpu_usage >> shiftp->shift2);
- thread->sched_usage =
- (thread->sched_usage >> shiftp->shift1) +
- (thread->sched_usage >> shiftp->shift2);
- }
- else {
- thread->cpu_usage =
- (thread->cpu_usage >> shiftp->shift1) -
- (thread->cpu_usage >> -(shiftp->shift2));
- thread->sched_usage =
- (thread->sched_usage >> shiftp->shift1) -
- (thread->sched_usage >> -(shiftp->shift2));
+ thread->cpu_usage = (thread->cpu_usage >> shiftp->shift1) +
+ (thread->cpu_usage >> shiftp->shift2);
+ thread->sched_usage = (thread->sched_usage >> shiftp->shift1) +
+ (thread->sched_usage >> shiftp->shift2);
+ } else {
+ thread->cpu_usage = (thread->cpu_usage >> shiftp->shift1) -
+ (thread->cpu_usage >> -(shiftp->shift2));
+ thread->sched_usage = (thread->sched_usage >> shiftp->shift1) -
+ (thread->sched_usage >> -(shiftp->shift2));
}
- }
- else {
+ } else {
thread->cpu_usage = thread->cpu_delta = 0;
thread->sched_usage = 0;
}
/*
* Check for fail-safe release.
*/
- if ( (thread->sched_mode & TH_MODE_FAILSAFE) &&
- thread->sched_stamp >= thread->safe_release ) {
- if (!(thread->safe_mode & TH_MODE_TIMESHARE)) {
- if (thread->safe_mode & TH_MODE_REALTIME) {
- thread->priority = BASEPRI_RTQUEUES;
+ if ((thread->sched_flags & TH_SFLAG_FAILSAFE) &&
+ mach_absolute_time() >= thread->safe_release) {
+ sched_thread_mode_undemote(thread, TH_SFLAG_FAILSAFE);
+ }
- thread->sched_mode |= TH_MODE_REALTIME;
- }
+ /*
+ * Recompute scheduled priority if appropriate.
+ */
+ if (thread->sched_mode == TH_MODE_TIMESHARE) {
+ int priority = sched_compute_timeshare_priority(thread);
- thread->sched_mode &= ~TH_MODE_TIMESHARE;
+ /*
+ * Adjust the scheduled priority like thread_recompute_sched_pri,
+ * except without setting an AST.
+ */
+ if ((!(thread->sched_flags & TH_SFLAG_PROMOTED_MASK) || (priority > thread->sched_pri)) &&
+ (!(thread->sched_flags & TH_SFLAG_DEPRESSED_MASK)) &&
+ priority != thread->sched_pri) {
- if ((thread->state & (TH_RUN|TH_IDLE)) == TH_RUN)
- sched_share_decr();
+ boolean_t removed = thread_run_queue_remove(thread);
- if (!(thread->sched_mode & TH_MODE_ISDEPRESSED))
- set_sched_pri(thread, thread->priority);
- }
+ thread->sched_pri = priority;
+
+ KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED, MACH_SCHED_CHANGE_PRIORITY),
+ (uintptr_t)thread_tid(thread),
+ thread->base_pri,
+ thread->sched_pri,
+ 0, /* eventually, 'reason' */
+ 0);
- thread->safe_mode = 0;
- thread->sched_mode &= ~TH_MODE_FAILSAFE;
+ if (removed)
+ thread_run_queue_reinsert(thread, SCHED_TAILQ);
+ }
}
- /*
- * Recompute scheduled priority if appropriate.
- */
- if ( (thread->sched_mode & TH_MODE_TIMESHARE) &&
- !(thread->sched_mode & TH_MODE_PROMOTED) &&
- !(thread->sched_mode & TH_MODE_ISDEPRESSED) ) {
- register int new_pri;
+ return;
+}
- do_priority_computation(thread, new_pri);
- if (new_pri != thread->sched_pri) {
- boolean_t removed = run_queue_remove(thread);
+#endif /* CONFIG_SCHED_TIMESHARE_CORE */
- thread->sched_pri = new_pri;
- if (removed)
- thread_setrun(thread, SCHED_TAILQ);
+
+/*
+ * TH_BUCKET_RUN is a count of *all* runnable non-idle threads.
+ * Each other bucket is a count of the runnable non-idle threads
+ * with that property.
+ */
+volatile uint32_t sched_run_buckets[TH_BUCKET_MAX];
+
+static void
+sched_incr_bucket(sched_bucket_t bucket)
+{
+ assert(bucket >= TH_BUCKET_FIXPRI &&
+ bucket <= TH_BUCKET_SHARE_BG);
+
+ hw_atomic_add(&sched_run_buckets[bucket], 1);
+}
+
+static void
+sched_decr_bucket(sched_bucket_t bucket)
+{
+ assert(bucket >= TH_BUCKET_FIXPRI &&
+ bucket <= TH_BUCKET_SHARE_BG);
+
+ assert(sched_run_buckets[bucket] > 0);
+
+ hw_atomic_sub(&sched_run_buckets[bucket], 1);
+}
+
+/* TH_RUN & !TH_IDLE controls whether a thread has a run count */
+
+uint32_t
+sched_run_incr(thread_t thread)
+{
+ assert((thread->state & (TH_RUN|TH_IDLE)) == TH_RUN);
+
+ uint32_t new_count = hw_atomic_add(&sched_run_buckets[TH_BUCKET_RUN], 1);
+
+ sched_incr_bucket(thread->th_sched_bucket);
+
+ return new_count;
+}
+
+uint32_t
+sched_run_decr(thread_t thread)
+{
+ assert((thread->state & (TH_RUN|TH_IDLE)) != TH_RUN);
+
+ sched_decr_bucket(thread->th_sched_bucket);
+
+ uint32_t new_count = hw_atomic_sub(&sched_run_buckets[TH_BUCKET_RUN], 1);
+
+ return new_count;
+}
+
+static void
+sched_update_thread_bucket(thread_t thread)
+{
+ sched_bucket_t old_bucket = thread->th_sched_bucket;
+ sched_bucket_t new_bucket = TH_BUCKET_RUN;
+
+ switch (thread->sched_mode) {
+ case TH_MODE_FIXED:
+ case TH_MODE_REALTIME:
+ new_bucket = TH_BUCKET_FIXPRI;
+ break;
+
+ case TH_MODE_TIMESHARE:
+ if (thread->base_pri > BASEPRI_UTILITY)
+ new_bucket = TH_BUCKET_SHARE_FG;
+ else if (thread->base_pri > MAXPRI_THROTTLE)
+ new_bucket = TH_BUCKET_SHARE_UT;
+ else
+ new_bucket = TH_BUCKET_SHARE_BG;
+ break;
+
+ default:
+ panic("unexpected mode: %d", thread->sched_mode);
+ break;
+ }
+
+ if (old_bucket != new_bucket) {
+ thread->th_sched_bucket = new_bucket;
+ thread->pri_shift = sched_pri_shifts[new_bucket];
+
+ if ((thread->state & (TH_RUN|TH_IDLE)) == TH_RUN) {
+ sched_decr_bucket(old_bucket);
+ sched_incr_bucket(new_bucket);
}
}
}
+
+/*
+ * Set the thread's true scheduling mode
+ * Called with thread mutex and thread locked
+ * The thread has already been removed from the runqueue.
+ *
+ * (saved_mode is handled before this point)
+ */
+void
+sched_set_thread_mode(thread_t thread, sched_mode_t new_mode)
+{
+ assert(thread->runq == PROCESSOR_NULL);
+
+ switch (new_mode) {
+ case TH_MODE_FIXED:
+ case TH_MODE_REALTIME:
+ case TH_MODE_TIMESHARE:
+ break;
+
+ default:
+ panic("unexpected mode: %d", new_mode);
+ break;
+ }
+
+ thread->sched_mode = new_mode;
+
+ sched_update_thread_bucket(thread);
+}
+
+/*
+ * Demote the true scheduler mode to timeshare (called with the thread locked)
+ */
+void
+sched_thread_mode_demote(thread_t thread, uint32_t reason)
+{
+ assert(reason & TH_SFLAG_DEMOTED_MASK);
+ assert((thread->sched_flags & reason) != reason);
+
+ if (thread->policy_reset)
+ return;
+
+ if (thread->sched_flags & TH_SFLAG_DEMOTED_MASK) {
+ /* Another demotion reason is already active */
+ thread->sched_flags |= reason;
+ return;
+ }
+
+ assert(thread->saved_mode == TH_MODE_NONE);
+
+ boolean_t removed = thread_run_queue_remove(thread);
+
+ thread->sched_flags |= reason;
+
+ thread->saved_mode = thread->sched_mode;
+
+ sched_set_thread_mode(thread, TH_MODE_TIMESHARE);
+
+ thread_recompute_priority(thread);
+
+ if (removed)
+ thread_run_queue_reinsert(thread, SCHED_TAILQ);
+}
+
+/*
+ * Un-demote the true scheduler mode back to the saved mode (called with the thread locked)
+ */
+void
+sched_thread_mode_undemote(thread_t thread, uint32_t reason)
+{
+ assert(reason & TH_SFLAG_DEMOTED_MASK);
+ assert((thread->sched_flags & reason) == reason);
+ assert(thread->saved_mode != TH_MODE_NONE);
+ assert(thread->sched_mode == TH_MODE_TIMESHARE);
+ assert(thread->policy_reset == 0);
+
+ thread->sched_flags &= ~reason;
+
+ if (thread->sched_flags & TH_SFLAG_DEMOTED_MASK) {
+ /* Another demotion reason is still active */
+ return;
+ }
+
+ boolean_t removed = thread_run_queue_remove(thread);
+
+ sched_set_thread_mode(thread, thread->saved_mode);
+
+ thread->saved_mode = TH_MODE_NONE;
+
+ thread_recompute_priority(thread);
+
+ if (removed)
+ thread_run_queue_reinsert(thread, SCHED_TAILQ);
+}
+
+
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