4 * Kernel scheduler and related syscalls
6 * Copyright (C) 1991-2002 Linus Torvalds
8 * 1996-12-23 Modified by Dave Grothe to fix bugs in semaphores and
9 * make semaphores SMP safe
10 * 1998-11-19 Implemented schedule_timeout() and related stuff
12 * 2002-01-04 New ultra-scalable O(1) scheduler by Ingo Molnar:
13 * hybrid priority-list and round-robin design with
14 * an array-switch method of distributing timeslices
15 * and per-CPU runqueues. Cleanups and useful suggestions
16 * by Davide Libenzi, preemptible kernel bits by Robert Love.
17 * 2003-09-03 Interactivity tuning by Con Kolivas.
18 * 2004-04-02 Scheduler domains code by Nick Piggin
22 #include <linux/module.h>
23 #include <linux/nmi.h>
24 #include <linux/init.h>
25 #include <asm/uaccess.h>
26 #include <linux/highmem.h>
27 #include <linux/smp_lock.h>
28 #include <linux/pagemap.h>
29 #include <asm/mmu_context.h>
30 #include <linux/interrupt.h>
31 #include <linux/completion.h>
32 #include <linux/kernel_stat.h>
33 #include <linux/security.h>
34 #include <linux/notifier.h>
35 #include <linux/suspend.h>
36 #include <linux/blkdev.h>
37 #include <linux/delay.h>
38 #include <linux/smp.h>
39 #include <linux/timer.h>
40 #include <linux/rcupdate.h>
41 #include <linux/cpu.h>
42 #include <linux/percpu.h>
43 #include <linux/kthread.h>
46 #include <asm/unistd.h>
49 #define cpu_to_node_mask(cpu) node_to_cpumask(cpu_to_node(cpu))
51 #define cpu_to_node_mask(cpu) (cpu_online_map)
55 * Convert user-nice values [ -20 ... 0 ... 19 ]
56 * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
59 #define NICE_TO_PRIO(nice) (MAX_RT_PRIO + (nice) + 20)
60 #define PRIO_TO_NICE(prio) ((prio) - MAX_RT_PRIO - 20)
61 #define TASK_NICE(p) PRIO_TO_NICE((p)->static_prio)
64 * 'User priority' is the nice value converted to something we
65 * can work with better when scaling various scheduler parameters,
66 * it's a [ 0 ... 39 ] range.
68 #define USER_PRIO(p) ((p)-MAX_RT_PRIO)
69 #define TASK_USER_PRIO(p) USER_PRIO((p)->static_prio)
70 #define MAX_USER_PRIO (USER_PRIO(MAX_PRIO))
71 #define AVG_TIMESLICE (MIN_TIMESLICE + ((MAX_TIMESLICE - MIN_TIMESLICE) *\
72 (MAX_PRIO-1-NICE_TO_PRIO(0))/(MAX_USER_PRIO - 1)))
75 * Some helpers for converting nanosecond timing to jiffy resolution
77 #define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ))
78 #define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ))
81 * These are the 'tuning knobs' of the scheduler:
83 * Minimum timeslice is 10 msecs, default timeslice is 100 msecs,
84 * maximum timeslice is 200 msecs. Timeslices get refilled after
87 #define MIN_TIMESLICE ( 10 * HZ / 1000)
88 #define MAX_TIMESLICE (200 * HZ / 1000)
89 #define ON_RUNQUEUE_WEIGHT 30
90 #define CHILD_PENALTY 95
91 #define PARENT_PENALTY 100
93 #define PRIO_BONUS_RATIO 25
94 #define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
95 #define INTERACTIVE_DELTA 2
96 #define MAX_SLEEP_AVG (AVG_TIMESLICE * MAX_BONUS)
97 #define STARVATION_LIMIT (MAX_SLEEP_AVG)
98 #define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG))
99 #define CREDIT_LIMIT 100
102 * If a task is 'interactive' then we reinsert it in the active
103 * array after it has expired its current timeslice. (it will not
104 * continue to run immediately, it will still roundrobin with
105 * other interactive tasks.)
107 * This part scales the interactivity limit depending on niceness.
109 * We scale it linearly, offset by the INTERACTIVE_DELTA delta.
110 * Here are a few examples of different nice levels:
112 * TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
113 * TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
114 * TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0]
115 * TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
116 * TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
118 * (the X axis represents the possible -5 ... 0 ... +5 dynamic
119 * priority range a task can explore, a value of '1' means the
120 * task is rated interactive.)
122 * Ie. nice +19 tasks can never get 'interactive' enough to be
123 * reinserted into the active array. And only heavily CPU-hog nice -20
124 * tasks will be expired. Default nice 0 tasks are somewhere between,
125 * it takes some effort for them to get interactive, but it's not
129 #define CURRENT_BONUS(p) \
130 (NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \
134 #define TIMESLICE_GRANULARITY(p) (MIN_TIMESLICE * \
135 (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
138 #define TIMESLICE_GRANULARITY(p) (MIN_TIMESLICE * \
139 (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)))
142 #define SCALE(v1,v1_max,v2_max) \
143 (v1) * (v2_max) / (v1_max)
146 (SCALE(TASK_NICE(p), 40, MAX_BONUS) + INTERACTIVE_DELTA)
148 #define TASK_INTERACTIVE(p) \
149 ((p)->prio <= (p)->static_prio - DELTA(p))
151 #define INTERACTIVE_SLEEP(p) \
152 (JIFFIES_TO_NS(MAX_SLEEP_AVG * \
153 (MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
155 #define HIGH_CREDIT(p) \
156 ((p)->interactive_credit > CREDIT_LIMIT)
158 #define LOW_CREDIT(p) \
159 ((p)->interactive_credit < -CREDIT_LIMIT)
161 #define TASK_PREEMPTS_CURR(p, rq) \
162 ((p)->prio < (rq)->curr->prio)
165 * BASE_TIMESLICE scales user-nice values [ -20 ... 19 ]
166 * to time slice values.
168 * The higher a thread's priority, the bigger timeslices
169 * it gets during one round of execution. But even the lowest
170 * priority thread gets MIN_TIMESLICE worth of execution time.
172 * task_timeslice() is the interface that is used by the scheduler.
175 #define BASE_TIMESLICE(p) (MIN_TIMESLICE + \
176 ((MAX_TIMESLICE - MIN_TIMESLICE) * \
177 (MAX_PRIO-1 - (p)->static_prio) / (MAX_USER_PRIO-1)))
179 static unsigned int task_timeslice(task_t *p)
181 return BASE_TIMESLICE(p);
184 #define task_hot(p, now, sd) ((now) - (p)->timestamp < (sd)->cache_hot_time)
187 * These are the runqueue data structures:
190 #define BITMAP_SIZE ((((MAX_PRIO+1+7)/8)+sizeof(long)-1)/sizeof(long))
192 typedef struct runqueue runqueue_t;
195 unsigned int nr_active;
196 unsigned long bitmap[BITMAP_SIZE];
197 struct list_head queue[MAX_PRIO];
201 * This is the main, per-CPU runqueue data structure.
203 * Locking rule: those places that want to lock multiple runqueues
204 * (such as the load balancing or the thread migration code), lock
205 * acquire operations must be ordered by ascending &runqueue.
211 * nr_running and cpu_load should be in the same cacheline because
212 * remote CPUs use both these fields when doing load calculation.
214 unsigned long nr_running;
216 unsigned long cpu_load;
218 unsigned long long nr_switches, nr_preempt;
219 unsigned long expired_timestamp, nr_uninterruptible;
220 unsigned long long timestamp_last_tick;
222 struct mm_struct *prev_mm;
223 prio_array_t *active, *expired, arrays[2];
224 int best_expired_prio;
228 struct sched_domain *sd;
230 /* For active balancing */
234 task_t *migration_thread;
235 struct list_head migration_queue;
239 static DEFINE_PER_CPU(struct runqueue, runqueues);
241 #define for_each_domain(cpu, domain) \
242 for (domain = cpu_rq(cpu)->sd; domain; domain = domain->parent)
244 #define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
245 #define this_rq() (&__get_cpu_var(runqueues))
246 #define task_rq(p) cpu_rq(task_cpu(p))
247 #define cpu_curr(cpu) (cpu_rq(cpu)->curr)
250 * Default context-switch locking:
252 #ifndef prepare_arch_switch
253 # define prepare_arch_switch(rq, next) do { } while (0)
254 # define finish_arch_switch(rq, next) spin_unlock_irq(&(rq)->lock)
255 # define task_running(rq, p) ((rq)->curr == (p))
259 * task_rq_lock - lock the runqueue a given task resides on and disable
260 * interrupts. Note the ordering: we can safely lookup the task_rq without
261 * explicitly disabling preemption.
263 static runqueue_t *task_rq_lock(task_t *p, unsigned long *flags)
268 local_irq_save(*flags);
270 spin_lock(&rq->lock);
271 if (unlikely(rq != task_rq(p))) {
272 spin_unlock_irqrestore(&rq->lock, *flags);
273 goto repeat_lock_task;
278 static inline void task_rq_unlock(runqueue_t *rq, unsigned long *flags)
280 spin_unlock_irqrestore(&rq->lock, *flags);
284 * rq_lock - lock a given runqueue and disable interrupts.
286 static runqueue_t *this_rq_lock(void)
292 spin_lock(&rq->lock);
297 static inline void rq_unlock(runqueue_t *rq)
299 spin_unlock_irq(&rq->lock);
303 * Adding/removing a task to/from a priority array:
305 static void dequeue_task(struct task_struct *p, prio_array_t *array)
308 list_del(&p->run_list);
309 if (list_empty(array->queue + p->prio))
310 __clear_bit(p->prio, array->bitmap);
313 static void enqueue_task(struct task_struct *p, prio_array_t *array)
315 list_add_tail(&p->run_list, array->queue + p->prio);
316 __set_bit(p->prio, array->bitmap);
322 * Used by the migration code - we pull tasks from the head of the
323 * remote queue so we want these tasks to show up at the head of the
326 static inline void enqueue_task_head(struct task_struct *p, prio_array_t *array)
328 list_add(&p->run_list, array->queue + p->prio);
329 __set_bit(p->prio, array->bitmap);
335 * effective_prio - return the priority that is based on the static
336 * priority but is modified by bonuses/penalties.
338 * We scale the actual sleep average [0 .... MAX_SLEEP_AVG]
339 * into the -5 ... 0 ... +5 bonus/penalty range.
341 * We use 25% of the full 0...39 priority range so that:
343 * 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs.
344 * 2) nice -20 CPU hogs do not get preempted by nice 0 tasks.
346 * Both properties are important to certain workloads.
348 static int effective_prio(task_t *p)
355 bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;
357 prio = p->static_prio - bonus;
358 if (prio < MAX_RT_PRIO)
360 if (prio > MAX_PRIO-1)
366 * __activate_task - move a task to the runqueue.
368 static inline void __activate_task(task_t *p, runqueue_t *rq)
370 enqueue_task(p, rq->active);
375 * __activate_idle_task - move idle task to the _front_ of runqueue.
377 static inline void __activate_idle_task(task_t *p, runqueue_t *rq)
379 enqueue_task_head(p, rq->active);
383 static void recalc_task_prio(task_t *p, unsigned long long now)
385 unsigned long long __sleep_time = now - p->timestamp;
386 unsigned long sleep_time;
388 if (__sleep_time > NS_MAX_SLEEP_AVG)
389 sleep_time = NS_MAX_SLEEP_AVG;
391 sleep_time = (unsigned long)__sleep_time;
393 if (likely(sleep_time > 0)) {
395 * User tasks that sleep a long time are categorised as
396 * idle and will get just interactive status to stay active &
397 * prevent them suddenly becoming cpu hogs and starving
400 if (p->mm && p->activated != -1 &&
401 sleep_time > INTERACTIVE_SLEEP(p)) {
402 p->sleep_avg = JIFFIES_TO_NS(MAX_SLEEP_AVG -
405 p->interactive_credit++;
408 * The lower the sleep avg a task has the more
409 * rapidly it will rise with sleep time.
411 sleep_time *= (MAX_BONUS - CURRENT_BONUS(p)) ? : 1;
414 * Tasks with low interactive_credit are limited to
415 * one timeslice worth of sleep avg bonus.
418 sleep_time > JIFFIES_TO_NS(task_timeslice(p)))
419 sleep_time = JIFFIES_TO_NS(task_timeslice(p));
422 * Non high_credit tasks waking from uninterruptible
423 * sleep are limited in their sleep_avg rise as they
424 * are likely to be cpu hogs waiting on I/O
426 if (p->activated == -1 && !HIGH_CREDIT(p) && p->mm) {
427 if (p->sleep_avg >= INTERACTIVE_SLEEP(p))
429 else if (p->sleep_avg + sleep_time >=
430 INTERACTIVE_SLEEP(p)) {
431 p->sleep_avg = INTERACTIVE_SLEEP(p);
437 * This code gives a bonus to interactive tasks.
439 * The boost works by updating the 'average sleep time'
440 * value here, based on ->timestamp. The more time a
441 * task spends sleeping, the higher the average gets -
442 * and the higher the priority boost gets as well.
444 p->sleep_avg += sleep_time;
446 if (p->sleep_avg > NS_MAX_SLEEP_AVG) {
447 p->sleep_avg = NS_MAX_SLEEP_AVG;
449 p->interactive_credit++;
454 p->prio = effective_prio(p);
458 * activate_task - move a task to the runqueue and do priority recalculation
460 * Update all the scheduling statistics stuff. (sleep average
461 * calculation, priority modifiers, etc.)
463 static void activate_task(task_t *p, runqueue_t *rq, int local)
465 unsigned long long now;
470 /* Compensate for drifting sched_clock */
471 runqueue_t *this_rq = this_rq();
472 now = (now - this_rq->timestamp_last_tick)
473 + rq->timestamp_last_tick;
477 recalc_task_prio(p, now);
480 * This checks to make sure it's not an uninterruptible task
481 * that is now waking up.
485 * Tasks which were woken up by interrupts (ie. hw events)
486 * are most likely of interactive nature. So we give them
487 * the credit of extending their sleep time to the period
488 * of time they spend on the runqueue, waiting for execution
489 * on a CPU, first time around:
495 * Normal first-time wakeups get a credit too for
496 * on-runqueue time, but it will be weighted down:
503 __activate_task(p, rq);
507 * deactivate_task - remove a task from the runqueue.
509 static void deactivate_task(struct task_struct *p, runqueue_t *rq)
512 if (p->state == TASK_UNINTERRUPTIBLE)
513 rq->nr_uninterruptible++;
514 dequeue_task(p, p->array);
519 * resched_task - mark a task 'to be rescheduled now'.
521 * On UP this means the setting of the need_resched flag, on SMP it
522 * might also involve a cross-CPU call to trigger the scheduler on
526 static void resched_task(task_t *p)
528 int need_resched, nrpolling;
531 /* minimise the chance of sending an interrupt to poll_idle() */
532 nrpolling = test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
533 need_resched = test_and_set_tsk_thread_flag(p,TIF_NEED_RESCHED);
534 nrpolling |= test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
536 if (!need_resched && !nrpolling && (task_cpu(p) != smp_processor_id()))
537 smp_send_reschedule(task_cpu(p));
541 static inline void resched_task(task_t *p)
543 set_tsk_need_resched(p);
548 * task_curr - is this task currently executing on a CPU?
549 * @p: the task in question.
551 inline int task_curr(const task_t *p)
553 return cpu_curr(task_cpu(p)) == p;
563 struct list_head list;
564 enum request_type type;
566 /* For REQ_MOVE_TASK */
570 /* For REQ_SET_DOMAIN */
571 struct sched_domain *sd;
573 struct completion done;
577 * The task's runqueue lock must be held.
578 * Returns true if you have to wait for migration thread.
580 static int migrate_task(task_t *p, int dest_cpu, migration_req_t *req)
582 runqueue_t *rq = task_rq(p);
585 * If the task is not on a runqueue (and not running), then
586 * it is sufficient to simply update the task's cpu field.
588 if (!p->array && !task_running(rq, p)) {
589 set_task_cpu(p, dest_cpu);
593 init_completion(&req->done);
594 req->type = REQ_MOVE_TASK;
596 req->dest_cpu = dest_cpu;
597 list_add(&req->list, &rq->migration_queue);
602 * wait_task_inactive - wait for a thread to unschedule.
604 * The caller must ensure that the task *will* unschedule sometime soon,
605 * else this function might spin for a *long* time. This function can't
606 * be called with interrupts off, or it may introduce deadlock with
607 * smp_call_function() if an IPI is sent by the same process we are
608 * waiting to become inactive.
610 void wait_task_inactive(task_t * p)
617 rq = task_rq_lock(p, &flags);
618 /* Must be off runqueue entirely, not preempted. */
619 if (unlikely(p->array)) {
620 /* If it's preempted, we yield. It could be a while. */
621 preempted = !task_running(rq, p);
622 task_rq_unlock(rq, &flags);
628 task_rq_unlock(rq, &flags);
632 * kick_process - kick a running thread to enter/exit the kernel
633 * @p: the to-be-kicked thread
635 * Cause a process which is running on another CPU to enter
636 * kernel-mode, without any delay. (to get signals handled.)
638 void kick_process(task_t *p)
644 if ((cpu != smp_processor_id()) && task_curr(p))
645 smp_send_reschedule(cpu);
649 EXPORT_SYMBOL_GPL(kick_process);
652 * Return a low guess at the load of a migration-source cpu.
654 * We want to under-estimate the load of migration sources, to
655 * balance conservatively.
657 static inline unsigned long source_load(int cpu)
659 runqueue_t *rq = cpu_rq(cpu);
660 unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;
662 return min(rq->cpu_load, load_now);
666 * Return a high guess at the load of a migration-target cpu
668 static inline unsigned long target_load(int cpu)
670 runqueue_t *rq = cpu_rq(cpu);
671 unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;
673 return max(rq->cpu_load, load_now);
679 * wake_idle() is useful especially on SMT architectures to wake a
680 * task onto an idle sibling if we would otherwise wake it onto a
683 * Returns the CPU we should wake onto.
685 #if defined(ARCH_HAS_SCHED_WAKE_IDLE)
686 static int wake_idle(int cpu, task_t *p)
689 runqueue_t *rq = cpu_rq(cpu);
690 struct sched_domain *sd;
697 if (!(sd->flags & SD_WAKE_IDLE))
700 cpus_and(tmp, sd->span, cpu_online_map);
701 cpus_and(tmp, tmp, p->cpus_allowed);
703 for_each_cpu_mask(i, tmp) {
711 static inline int wake_idle(int cpu, task_t *p)
718 * try_to_wake_up - wake up a thread
719 * @p: the to-be-woken-up thread
720 * @state: the mask of task states that can be woken
721 * @sync: do a synchronous wakeup?
723 * Put it on the run-queue if it's not already there. The "current"
724 * thread is always on the run-queue (except when the actual
725 * re-schedule is in progress), and as such you're allowed to do
726 * the simpler "current->state = TASK_RUNNING" to mark yourself
727 * runnable without the overhead of this.
729 * returns failure only if the task is already active.
731 static int try_to_wake_up(task_t * p, unsigned int state, int sync)
733 int cpu, this_cpu, success = 0;
738 unsigned long load, this_load;
739 struct sched_domain *sd;
743 rq = task_rq_lock(p, &flags);
744 old_state = p->state;
745 if (!(old_state & state))
752 this_cpu = smp_processor_id();
755 if (unlikely(task_running(rq, p)))
760 if (cpu == this_cpu || unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
763 load = source_load(cpu);
764 this_load = target_load(this_cpu);
767 * If sync wakeup then subtract the (maximum possible) effect of
768 * the currently running task from the load of the current CPU:
771 this_load -= SCHED_LOAD_SCALE;
773 /* Don't pull the task off an idle CPU to a busy one */
774 if (load < SCHED_LOAD_SCALE/2 && this_load > SCHED_LOAD_SCALE/2)
777 new_cpu = this_cpu; /* Wake to this CPU if we can */
780 * Scan domains for affine wakeup and passive balancing
783 for_each_domain(this_cpu, sd) {
784 unsigned int imbalance;
786 * Start passive balancing when half the imbalance_pct
789 imbalance = sd->imbalance_pct + (sd->imbalance_pct - 100) / 2;
791 if ( ((sd->flags & SD_WAKE_AFFINE) &&
792 !task_hot(p, rq->timestamp_last_tick, sd))
793 || ((sd->flags & SD_WAKE_BALANCE) &&
794 imbalance*this_load <= 100*load) ) {
796 * Now sd has SD_WAKE_AFFINE and p is cache cold in sd
797 * or sd has SD_WAKE_BALANCE and there is an imbalance
799 if (cpu_isset(cpu, sd->span))
804 new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */
806 new_cpu = wake_idle(new_cpu, p);
807 if (new_cpu != cpu && cpu_isset(new_cpu, p->cpus_allowed)) {
808 set_task_cpu(p, new_cpu);
809 task_rq_unlock(rq, &flags);
810 /* might preempt at this point */
811 rq = task_rq_lock(p, &flags);
812 old_state = p->state;
813 if (!(old_state & state))
818 this_cpu = smp_processor_id();
823 #endif /* CONFIG_SMP */
824 if (old_state == TASK_UNINTERRUPTIBLE) {
825 rq->nr_uninterruptible--;
827 * Tasks on involuntary sleep don't earn
828 * sleep_avg beyond just interactive state.
834 * Sync wakeups (i.e. those types of wakeups where the waker
835 * has indicated that it will leave the CPU in short order)
836 * don't trigger a preemption, if the woken up task will run on
837 * this cpu. (in this case the 'I will reschedule' promise of
838 * the waker guarantees that the freshly woken up task is going
839 * to be considered on this CPU.)
841 activate_task(p, rq, cpu == this_cpu);
842 if (!sync || cpu != this_cpu) {
843 if (TASK_PREEMPTS_CURR(p, rq))
844 resched_task(rq->curr);
849 p->state = TASK_RUNNING;
851 task_rq_unlock(rq, &flags);
856 int fastcall wake_up_process(task_t * p)
858 return try_to_wake_up(p, TASK_STOPPED |
859 TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, 0);
862 EXPORT_SYMBOL(wake_up_process);
864 int fastcall wake_up_state(task_t *p, unsigned int state)
866 return try_to_wake_up(p, state, 0);
870 * Perform scheduler related setup for a newly forked process p.
871 * p is forked by current.
873 void fastcall sched_fork(task_t *p)
876 * We mark the process as running here, but have not actually
877 * inserted it onto the runqueue yet. This guarantees that
878 * nobody will actually run it, and a signal or other external
879 * event cannot wake it up and insert it on the runqueue either.
881 p->state = TASK_RUNNING;
882 INIT_LIST_HEAD(&p->run_list);
884 spin_lock_init(&p->switch_lock);
885 #ifdef CONFIG_PREEMPT
887 * During context-switch we hold precisely one spinlock, which
888 * schedule_tail drops. (in the common case it's this_rq()->lock,
889 * but it also can be p->switch_lock.) So we compensate with a count
890 * of 1. Also, we want to start with kernel preemption disabled.
892 p->thread_info->preempt_count = 1;
895 * Share the timeslice between parent and child, thus the
896 * total amount of pending timeslices in the system doesn't change,
897 * resulting in more scheduling fairness.
900 p->time_slice = (current->time_slice + 1) >> 1;
902 * The remainder of the first timeslice might be recovered by
903 * the parent if the child exits early enough.
905 p->first_time_slice = 1;
906 current->time_slice >>= 1;
907 p->timestamp = sched_clock();
908 if (!current->time_slice) {
910 * This case is rare, it happens when the parent has only
911 * a single jiffy left from its timeslice. Taking the
912 * runqueue lock is not a problem.
914 current->time_slice = 1;
916 scheduler_tick(0, 0);
924 * wake_up_forked_process - wake up a freshly forked process.
926 * This function will do some initial scheduler statistics housekeeping
927 * that must be done for every newly created process.
929 void fastcall wake_up_forked_process(task_t * p)
932 runqueue_t *rq = task_rq_lock(current, &flags);
934 BUG_ON(p->state != TASK_RUNNING);
937 * We decrease the sleep average of forking parents
938 * and children as well, to keep max-interactive tasks
939 * from forking tasks that are max-interactive.
941 current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
942 PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
944 p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
945 CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
947 p->interactive_credit = 0;
949 p->prio = effective_prio(p);
950 set_task_cpu(p, smp_processor_id());
952 if (unlikely(!current->array))
953 __activate_task(p, rq);
955 p->prio = current->prio;
956 list_add_tail(&p->run_list, ¤t->run_list);
957 p->array = current->array;
958 p->array->nr_active++;
961 task_rq_unlock(rq, &flags);
965 * Potentially available exiting-child timeslices are
966 * retrieved here - this way the parent does not get
967 * penalized for creating too many threads.
969 * (this cannot be used to 'generate' timeslices
970 * artificially, because any timeslice recovered here
971 * was given away by the parent in the first place.)
973 void fastcall sched_exit(task_t * p)
978 local_irq_save(flags);
979 if (p->first_time_slice) {
980 p->parent->time_slice += p->time_slice;
981 if (unlikely(p->parent->time_slice > MAX_TIMESLICE))
982 p->parent->time_slice = MAX_TIMESLICE;
984 local_irq_restore(flags);
986 * If the child was a (relative-) CPU hog then decrease
987 * the sleep_avg of the parent as well.
989 rq = task_rq_lock(p->parent, &flags);
990 if (p->sleep_avg < p->parent->sleep_avg)
991 p->parent->sleep_avg = p->parent->sleep_avg /
992 (EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
994 task_rq_unlock(rq, &flags);
998 * finish_task_switch - clean up after a task-switch
999 * @prev: the thread we just switched away from.
1001 * We enter this with the runqueue still locked, and finish_arch_switch()
1002 * will unlock it along with doing any other architecture-specific cleanup
1005 * Note that we may have delayed dropping an mm in context_switch(). If
1006 * so, we finish that here outside of the runqueue lock. (Doing it
1007 * with the lock held can cause deadlocks; see schedule() for
1010 static void finish_task_switch(task_t *prev)
1012 runqueue_t *rq = this_rq();
1013 struct mm_struct *mm = rq->prev_mm;
1014 unsigned long prev_task_flags;
1019 * A task struct has one reference for the use as "current".
1020 * If a task dies, then it sets TASK_ZOMBIE in tsk->state and calls
1021 * schedule one last time. The schedule call will never return,
1022 * and the scheduled task must drop that reference.
1023 * The test for TASK_ZOMBIE must occur while the runqueue locks are
1024 * still held, otherwise prev could be scheduled on another cpu, die
1025 * there before we look at prev->state, and then the reference would
1027 * Manfred Spraul <manfred@colorfullife.com>
1029 prev_task_flags = prev->flags;
1030 finish_arch_switch(rq, prev);
1033 if (unlikely(prev_task_flags & PF_DEAD))
1034 put_task_struct(prev);
1038 * schedule_tail - first thing a freshly forked thread must call.
1039 * @prev: the thread we just switched away from.
1041 asmlinkage void schedule_tail(task_t *prev)
1043 finish_task_switch(prev);
1045 if (current->set_child_tid)
1046 put_user(current->pid, current->set_child_tid);
1050 * context_switch - switch to the new MM and the new
1051 * thread's register state.
1054 task_t * context_switch(runqueue_t *rq, task_t *prev, task_t *next)
1056 struct mm_struct *mm = next->mm;
1057 struct mm_struct *oldmm = prev->active_mm;
1059 if (unlikely(!mm)) {
1060 next->active_mm = oldmm;
1061 atomic_inc(&oldmm->mm_count);
1062 enter_lazy_tlb(oldmm, next);
1064 switch_mm(oldmm, mm, next);
1066 if (unlikely(!prev->mm)) {
1067 prev->active_mm = NULL;
1068 WARN_ON(rq->prev_mm);
1069 rq->prev_mm = oldmm;
1072 /* Here we just switch the register state and the stack. */
1073 switch_to(prev, next, prev);
1079 * nr_running, nr_uninterruptible and nr_context_switches:
1081 * externally visible scheduler statistics: current number of runnable
1082 * threads, current number of uninterruptible-sleeping threads, total
1083 * number of context switches performed since bootup.
1085 unsigned long nr_running(void)
1087 unsigned long i, sum = 0;
1090 sum += cpu_rq(i)->nr_running;
1095 unsigned long nr_uninterruptible(void)
1097 unsigned long i, sum = 0;
1099 for_each_online_cpu(i)
1100 sum += cpu_rq(i)->nr_uninterruptible;
1105 unsigned long long nr_context_switches(void)
1107 unsigned long long i, sum = 0;
1109 for_each_online_cpu(i)
1110 sum += cpu_rq(i)->nr_switches;
1115 unsigned long nr_iowait(void)
1117 unsigned long i, sum = 0;
1119 for_each_online_cpu(i)
1120 sum += atomic_read(&cpu_rq(i)->nr_iowait);
1126 * double_rq_lock - safely lock two runqueues
1128 * Note this does not disable interrupts like task_rq_lock,
1129 * you need to do so manually before calling.
1131 static void double_rq_lock(runqueue_t *rq1, runqueue_t *rq2)
1134 spin_lock(&rq1->lock);
1137 spin_lock(&rq1->lock);
1138 spin_lock(&rq2->lock);
1140 spin_lock(&rq2->lock);
1141 spin_lock(&rq1->lock);
1147 * double_rq_unlock - safely unlock two runqueues
1149 * Note this does not restore interrupts like task_rq_unlock,
1150 * you need to do so manually after calling.
1152 static void double_rq_unlock(runqueue_t *rq1, runqueue_t *rq2)
1154 spin_unlock(&rq1->lock);
1156 spin_unlock(&rq2->lock);
1159 unsigned long long nr_preempt(void)
1161 unsigned long long i, sum = 0;
1163 for_each_online_cpu(i)
1164 sum += cpu_rq(i)->nr_preempt;
1179 * find_idlest_cpu - find the least busy runqueue.
1181 static int find_idlest_cpu(struct task_struct *p, int this_cpu,
1182 struct sched_domain *sd)
1184 unsigned long load, min_load, this_load;
1189 min_load = ULONG_MAX;
1191 cpus_and(mask, sd->span, cpu_online_map);
1192 cpus_and(mask, mask, p->cpus_allowed);
1194 for_each_cpu_mask(i, mask) {
1195 load = target_load(i);
1197 if (load < min_load) {
1201 /* break out early on an idle CPU: */
1207 /* add +1 to account for the new task */
1208 this_load = source_load(this_cpu) + SCHED_LOAD_SCALE;
1211 * Would with the addition of the new task to the
1212 * current CPU there be an imbalance between this
1213 * CPU and the idlest CPU?
1215 * Use half of the balancing threshold - new-context is
1216 * a good opportunity to balance.
1218 if (min_load*(100 + (sd->imbalance_pct-100)/2) < this_load*100)
1225 * wake_up_forked_thread - wake up a freshly forked thread.
1227 * This function will do some initial scheduler statistics housekeeping
1228 * that must be done for every newly created context, and it also does
1229 * runqueue balancing.
1231 void fastcall wake_up_forked_thread(task_t * p)
1233 unsigned long flags;
1234 int this_cpu = get_cpu(), cpu;
1235 struct sched_domain *tmp, *sd = NULL;
1236 runqueue_t *this_rq = cpu_rq(this_cpu), *rq;
1239 * Find the largest domain that this CPU is part of that
1240 * is willing to balance on clone:
1242 for_each_domain(this_cpu, tmp)
1243 if (tmp->flags & SD_BALANCE_CLONE)
1246 cpu = find_idlest_cpu(p, this_cpu, sd);
1250 local_irq_save(flags);
1253 double_rq_lock(this_rq, rq);
1255 BUG_ON(p->state != TASK_RUNNING);
1258 * We did find_idlest_cpu() unlocked, so in theory
1259 * the mask could have changed - just dont migrate
1262 if (unlikely(!cpu_isset(cpu, p->cpus_allowed))) {
1264 double_rq_unlock(this_rq, rq);
1268 * We decrease the sleep average of forking parents
1269 * and children as well, to keep max-interactive tasks
1270 * from forking tasks that are max-interactive.
1272 current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
1273 PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
1275 p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
1276 CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
1278 p->interactive_credit = 0;
1280 p->prio = effective_prio(p);
1281 set_task_cpu(p, cpu);
1283 if (cpu == this_cpu) {
1284 if (unlikely(!current->array))
1285 __activate_task(p, rq);
1287 p->prio = current->prio;
1288 list_add_tail(&p->run_list, ¤t->run_list);
1289 p->array = current->array;
1290 p->array->nr_active++;
1294 /* Not the local CPU - must adjust timestamp */
1295 p->timestamp = (p->timestamp - this_rq->timestamp_last_tick)
1296 + rq->timestamp_last_tick;
1297 __activate_task(p, rq);
1298 if (TASK_PREEMPTS_CURR(p, rq))
1299 resched_task(rq->curr);
1302 double_rq_unlock(this_rq, rq);
1303 local_irq_restore(flags);
1308 * If dest_cpu is allowed for this process, migrate the task to it.
1309 * This is accomplished by forcing the cpu_allowed mask to only
1310 * allow dest_cpu, which will force the cpu onto dest_cpu. Then
1311 * the cpu_allowed mask is restored.
1313 static void sched_migrate_task(task_t *p, int dest_cpu)
1315 migration_req_t req;
1317 unsigned long flags;
1319 rq = task_rq_lock(p, &flags);
1320 if (!cpu_isset(dest_cpu, p->cpus_allowed)
1321 || unlikely(cpu_is_offline(dest_cpu)))
1324 /* force the process onto the specified CPU */
1325 if (migrate_task(p, dest_cpu, &req)) {
1326 /* Need to wait for migration thread (might exit: take ref). */
1327 struct task_struct *mt = rq->migration_thread;
1328 get_task_struct(mt);
1329 task_rq_unlock(rq, &flags);
1330 wake_up_process(mt);
1331 put_task_struct(mt);
1332 wait_for_completion(&req.done);
1336 task_rq_unlock(rq, &flags);
1340 * sched_balance_exec(): find the highest-level, exec-balance-capable
1341 * domain and try to migrate the task to the least loaded CPU.
1343 * execve() is a valuable balancing opportunity, because at this point
1344 * the task has the smallest effective memory and cache footprint.
1346 void sched_balance_exec(void)
1348 struct sched_domain *tmp, *sd = NULL;
1349 int new_cpu, this_cpu = get_cpu();
1351 /* Prefer the current CPU if there's only this task running */
1352 if (this_rq()->nr_running <= 1)
1355 for_each_domain(this_cpu, tmp)
1356 if (tmp->flags & SD_BALANCE_EXEC)
1360 new_cpu = find_idlest_cpu(current, this_cpu, sd);
1361 if (new_cpu != this_cpu) {
1363 sched_migrate_task(current, new_cpu);
1372 * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
1374 static void double_lock_balance(runqueue_t *this_rq, runqueue_t *busiest)
1376 if (unlikely(!spin_trylock(&busiest->lock))) {
1377 if (busiest < this_rq) {
1378 spin_unlock(&this_rq->lock);
1379 spin_lock(&busiest->lock);
1380 spin_lock(&this_rq->lock);
1382 spin_lock(&busiest->lock);
1387 * pull_task - move a task from a remote runqueue to the local runqueue.
1388 * Both runqueues must be locked.
1391 void pull_task(runqueue_t *src_rq, prio_array_t *src_array, task_t *p,
1392 runqueue_t *this_rq, prio_array_t *this_array, int this_cpu)
1394 dequeue_task(p, src_array);
1395 src_rq->nr_running--;
1396 set_task_cpu(p, this_cpu);
1397 this_rq->nr_running++;
1398 enqueue_task(p, this_array);
1399 p->timestamp = (p->timestamp - src_rq->timestamp_last_tick)
1400 + this_rq->timestamp_last_tick;
1402 * Note that idle threads have a prio of MAX_PRIO, for this test
1403 * to be always true for them.
1405 if (TASK_PREEMPTS_CURR(p, this_rq))
1406 resched_task(this_rq->curr);
1410 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
1413 int can_migrate_task(task_t *p, runqueue_t *rq, int this_cpu,
1414 struct sched_domain *sd, enum idle_type idle)
1417 * We do not migrate tasks that are:
1418 * 1) running (obviously), or
1419 * 2) cannot be migrated to this CPU due to cpus_allowed, or
1420 * 3) are cache-hot on their current CPU.
1422 if (task_running(rq, p))
1424 if (!cpu_isset(this_cpu, p->cpus_allowed))
1427 /* Aggressive migration if we've failed balancing */
1428 if (idle == NEWLY_IDLE ||
1429 sd->nr_balance_failed < sd->cache_nice_tries) {
1430 if (task_hot(p, rq->timestamp_last_tick, sd))
1438 * move_tasks tries to move up to max_nr_move tasks from busiest to this_rq,
1439 * as part of a balancing operation within "domain". Returns the number of
1442 * Called with both runqueues locked.
1444 static int move_tasks(runqueue_t *this_rq, int this_cpu, runqueue_t *busiest,
1445 unsigned long max_nr_move, struct sched_domain *sd,
1446 enum idle_type idle)
1448 prio_array_t *array, *dst_array;
1449 struct list_head *head, *curr;
1450 int idx, pulled = 0;
1453 if (max_nr_move <= 0 || busiest->nr_running <= 1)
1457 * We first consider expired tasks. Those will likely not be
1458 * executed in the near future, and they are most likely to
1459 * be cache-cold, thus switching CPUs has the least effect
1462 if (busiest->expired->nr_active) {
1463 array = busiest->expired;
1464 dst_array = this_rq->expired;
1466 array = busiest->active;
1467 dst_array = this_rq->active;
1471 /* Start searching at priority 0: */
1475 idx = sched_find_first_bit(array->bitmap);
1477 idx = find_next_bit(array->bitmap, MAX_PRIO, idx);
1478 if (idx >= MAX_PRIO) {
1479 if (array == busiest->expired && busiest->active->nr_active) {
1480 array = busiest->active;
1481 dst_array = this_rq->active;
1487 head = array->queue + idx;
1490 tmp = list_entry(curr, task_t, run_list);
1494 if (!can_migrate_task(tmp, busiest, this_cpu, sd, idle)) {
1500 pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu);
1503 /* We only want to steal up to the prescribed number of tasks. */
1504 if (pulled < max_nr_move) {
1515 * find_busiest_group finds and returns the busiest CPU group within the
1516 * domain. It calculates and returns the number of tasks which should be
1517 * moved to restore balance via the imbalance parameter.
1519 static struct sched_group *
1520 find_busiest_group(struct sched_domain *sd, int this_cpu,
1521 unsigned long *imbalance, enum idle_type idle)
1523 struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
1524 unsigned long max_load, avg_load, total_load, this_load, total_pwr;
1526 max_load = this_load = total_load = total_pwr = 0;
1534 local_group = cpu_isset(this_cpu, group->cpumask);
1536 /* Tally up the load of all CPUs in the group */
1538 cpus_and(tmp, group->cpumask, cpu_online_map);
1539 if (unlikely(cpus_empty(tmp)))
1542 for_each_cpu_mask(i, tmp) {
1543 /* Bias balancing toward cpus of our domain */
1545 load = target_load(i);
1547 load = source_load(i);
1556 total_load += avg_load;
1557 total_pwr += group->cpu_power;
1559 /* Adjust by relative CPU power of the group */
1560 avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
1563 this_load = avg_load;
1566 } else if (avg_load > max_load) {
1567 max_load = avg_load;
1571 group = group->next;
1572 } while (group != sd->groups);
1574 if (!busiest || this_load >= max_load)
1577 avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;
1579 if (this_load >= avg_load ||
1580 100*max_load <= sd->imbalance_pct*this_load)
1584 * We're trying to get all the cpus to the average_load, so we don't
1585 * want to push ourselves above the average load, nor do we wish to
1586 * reduce the max loaded cpu below the average load, as either of these
1587 * actions would just result in more rebalancing later, and ping-pong
1588 * tasks around. Thus we look for the minimum possible imbalance.
1589 * Negative imbalances (*we* are more loaded than anyone else) will
1590 * be counted as no imbalance for these purposes -- we can't fix that
1591 * by pulling tasks to us. Be careful of negative numbers as they'll
1592 * appear as very large values with unsigned longs.
1594 *imbalance = min(max_load - avg_load, avg_load - this_load);
1596 /* How much load to actually move to equalise the imbalance */
1597 *imbalance = (*imbalance * min(busiest->cpu_power, this->cpu_power))
1600 if (*imbalance < SCHED_LOAD_SCALE - 1) {
1601 unsigned long pwr_now = 0, pwr_move = 0;
1604 if (max_load - this_load >= SCHED_LOAD_SCALE*2) {
1610 * OK, we don't have enough imbalance to justify moving tasks,
1611 * however we may be able to increase total CPU power used by
1615 pwr_now += busiest->cpu_power*min(SCHED_LOAD_SCALE, max_load);
1616 pwr_now += this->cpu_power*min(SCHED_LOAD_SCALE, this_load);
1617 pwr_now /= SCHED_LOAD_SCALE;
1619 /* Amount of load we'd subtract */
1620 tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/busiest->cpu_power;
1622 pwr_move += busiest->cpu_power*min(SCHED_LOAD_SCALE,
1625 /* Amount of load we'd add */
1626 tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/this->cpu_power;
1629 pwr_move += this->cpu_power*min(SCHED_LOAD_SCALE, this_load + tmp);
1630 pwr_move /= SCHED_LOAD_SCALE;
1632 /* Move if we gain another 8th of a CPU worth of throughput */
1633 if (pwr_move < pwr_now + SCHED_LOAD_SCALE / 8)
1640 /* Get rid of the scaling factor, rounding down as we divide */
1641 *imbalance = (*imbalance + 1) / SCHED_LOAD_SCALE;
1646 if (busiest && (idle == NEWLY_IDLE ||
1647 (idle == IDLE && max_load > SCHED_LOAD_SCALE)) ) {
1657 * find_busiest_queue - find the busiest runqueue among the cpus in group.
1659 static runqueue_t *find_busiest_queue(struct sched_group *group)
1662 unsigned long load, max_load = 0;
1663 runqueue_t *busiest = NULL;
1666 cpus_and(tmp, group->cpumask, cpu_online_map);
1667 for_each_cpu_mask(i, tmp) {
1668 load = source_load(i);
1670 if (load > max_load) {
1672 busiest = cpu_rq(i);
1680 * Check this_cpu to ensure it is balanced within domain. Attempt to move
1681 * tasks if there is an imbalance.
1683 * Called with this_rq unlocked.
1685 static int load_balance(int this_cpu, runqueue_t *this_rq,
1686 struct sched_domain *sd, enum idle_type idle)
1688 struct sched_group *group;
1689 runqueue_t *busiest;
1690 unsigned long imbalance;
1693 spin_lock(&this_rq->lock);
1695 group = find_busiest_group(sd, this_cpu, &imbalance, idle);
1699 busiest = find_busiest_queue(group);
1703 * This should be "impossible", but since load
1704 * balancing is inherently racy and statistical,
1705 * it could happen in theory.
1707 if (unlikely(busiest == this_rq)) {
1713 if (busiest->nr_running > 1) {
1715 * Attempt to move tasks. If find_busiest_group has found
1716 * an imbalance but busiest->nr_running <= 1, the group is
1717 * still unbalanced. nr_moved simply stays zero, so it is
1718 * correctly treated as an imbalance.
1720 double_lock_balance(this_rq, busiest);
1721 nr_moved = move_tasks(this_rq, this_cpu, busiest,
1722 imbalance, sd, idle);
1723 spin_unlock(&busiest->lock);
1725 spin_unlock(&this_rq->lock);
1728 sd->nr_balance_failed++;
1730 if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
1733 spin_lock(&busiest->lock);
1734 if (!busiest->active_balance) {
1735 busiest->active_balance = 1;
1736 busiest->push_cpu = this_cpu;
1739 spin_unlock(&busiest->lock);
1741 wake_up_process(busiest->migration_thread);
1744 * We've kicked active balancing, reset the failure
1747 sd->nr_balance_failed = sd->cache_nice_tries;
1750 sd->nr_balance_failed = 0;
1752 /* We were unbalanced, so reset the balancing interval */
1753 sd->balance_interval = sd->min_interval;
1758 spin_unlock(&this_rq->lock);
1760 /* tune up the balancing interval */
1761 if (sd->balance_interval < sd->max_interval)
1762 sd->balance_interval *= 2;
1768 * Check this_cpu to ensure it is balanced within domain. Attempt to move
1769 * tasks if there is an imbalance.
1771 * Called from schedule when this_rq is about to become idle (NEWLY_IDLE).
1772 * this_rq is locked.
1774 static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
1775 struct sched_domain *sd)
1777 struct sched_group *group;
1778 runqueue_t *busiest = NULL;
1779 unsigned long imbalance;
1782 group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE);
1786 busiest = find_busiest_queue(group);
1787 if (!busiest || busiest == this_rq)
1790 /* Attempt to move tasks */
1791 double_lock_balance(this_rq, busiest);
1793 nr_moved = move_tasks(this_rq, this_cpu, busiest,
1794 imbalance, sd, NEWLY_IDLE);
1796 spin_unlock(&busiest->lock);
1803 * idle_balance is called by schedule() if this_cpu is about to become
1804 * idle. Attempts to pull tasks from other CPUs.
1806 static inline void idle_balance(int this_cpu, runqueue_t *this_rq)
1808 struct sched_domain *sd;
1810 for_each_domain(this_cpu, sd) {
1811 if (sd->flags & SD_BALANCE_NEWIDLE) {
1812 if (load_balance_newidle(this_cpu, this_rq, sd)) {
1813 /* We've pulled tasks over so stop searching */
1821 * active_load_balance is run by migration threads. It pushes a running
1822 * task off the cpu. It can be required to correctly have at least 1 task
1823 * running on each physical CPU where possible, and not have a physical /
1824 * logical imbalance.
1826 * Called with busiest locked.
1828 static void active_load_balance(runqueue_t *busiest, int busiest_cpu)
1830 struct sched_domain *sd;
1831 struct sched_group *group, *busy_group;
1834 if (busiest->nr_running <= 1)
1837 for_each_domain(busiest_cpu, sd)
1838 if (cpu_isset(busiest->push_cpu, sd->span))
1846 while (!cpu_isset(busiest_cpu, group->cpumask))
1847 group = group->next;
1856 if (group == busy_group)
1859 cpus_and(tmp, group->cpumask, cpu_online_map);
1860 if (!cpus_weight(tmp))
1863 for_each_cpu_mask(i, tmp) {
1869 rq = cpu_rq(push_cpu);
1872 * This condition is "impossible", but since load
1873 * balancing is inherently a bit racy and statistical,
1874 * it can trigger.. Reported by Bjorn Helgaas on a
1877 if (unlikely(busiest == rq))
1879 double_lock_balance(busiest, rq);
1880 move_tasks(rq, push_cpu, busiest, 1, sd, IDLE);
1881 spin_unlock(&rq->lock);
1883 group = group->next;
1884 } while (group != sd->groups);
1888 * rebalance_tick will get called every timer tick, on every CPU.
1890 * It checks each scheduling domain to see if it is due to be balanced,
1891 * and initiates a balancing operation if so.
1893 * Balancing parameters are set up in arch_init_sched_domains.
1896 /* Don't have all balancing operations going off at once */
1897 #define CPU_OFFSET(cpu) (HZ * cpu / NR_CPUS)
1899 static void rebalance_tick(int this_cpu, runqueue_t *this_rq,
1900 enum idle_type idle)
1902 unsigned long old_load, this_load;
1903 unsigned long j = jiffies + CPU_OFFSET(this_cpu);
1904 struct sched_domain *sd;
1906 /* Update our load */
1907 old_load = this_rq->cpu_load;
1908 this_load = this_rq->nr_running * SCHED_LOAD_SCALE;
1910 * Round up the averaging division if load is increasing. This
1911 * prevents us from getting stuck on 9 if the load is 10, for
1914 if (this_load > old_load)
1916 this_rq->cpu_load = (old_load + this_load) / 2;
1918 for_each_domain(this_cpu, sd) {
1919 unsigned long interval = sd->balance_interval;
1922 interval *= sd->busy_factor;
1924 /* scale ms to jiffies */
1925 interval = msecs_to_jiffies(interval);
1926 if (unlikely(!interval))
1929 if (j - sd->last_balance >= interval) {
1930 if (load_balance(this_cpu, this_rq, sd, idle)) {
1931 /* We've pulled tasks over so no longer idle */
1934 sd->last_balance += interval;
1940 * on UP we do not need to balance between CPUs:
1942 static inline void rebalance_tick(int cpu, runqueue_t *rq, enum idle_type idle)
1945 static inline void idle_balance(int cpu, runqueue_t *rq)
1950 static inline int wake_priority_sleeper(runqueue_t *rq)
1952 #ifdef CONFIG_SCHED_SMT
1954 * If an SMT sibling task has been put to sleep for priority
1955 * reasons reschedule the idle task to see if it can now run.
1957 if (rq->nr_running) {
1958 resched_task(rq->idle);
1965 DEFINE_PER_CPU(struct kernel_stat, kstat);
1967 EXPORT_PER_CPU_SYMBOL(kstat);
1970 * We place interactive tasks back into the active array, if possible.
1972 * To guarantee that this does not starve expired tasks we ignore the
1973 * interactivity of a task if the first expired task had to wait more
1974 * than a 'reasonable' amount of time. This deadline timeout is
1975 * load-dependent, as the frequency of array switched decreases with
1976 * increasing number of running tasks. We also ignore the interactivity
1977 * if a better static_prio task has expired:
1979 #define EXPIRED_STARVING(rq) \
1980 ((STARVATION_LIMIT && ((rq)->expired_timestamp && \
1981 (jiffies - (rq)->expired_timestamp >= \
1982 STARVATION_LIMIT * ((rq)->nr_running) + 1))) || \
1983 ((rq)->curr->static_prio > (rq)->best_expired_prio))
1986 * This function gets called by the timer code, with HZ frequency.
1987 * We call it with interrupts disabled.
1989 * It also gets called by the fork code, when changing the parent's
1992 void scheduler_tick(int user_ticks, int sys_ticks)
1994 int cpu = smp_processor_id();
1995 struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
1996 runqueue_t *rq = this_rq();
1997 task_t *p = current;
1999 rq->timestamp_last_tick = sched_clock();
2001 if (rcu_pending(cpu))
2002 rcu_check_callbacks(cpu, user_ticks);
2004 /* note: this timer irq context must be accounted for as well */
2005 if (hardirq_count() - HARDIRQ_OFFSET) {
2006 cpustat->irq += sys_ticks;
2008 } else if (softirq_count()) {
2009 cpustat->softirq += sys_ticks;
2013 if (p == rq->idle) {
2014 if (atomic_read(&rq->nr_iowait) > 0)
2015 cpustat->iowait += sys_ticks;
2017 cpustat->idle += sys_ticks;
2018 if (wake_priority_sleeper(rq))
2020 rebalance_tick(cpu, rq, IDLE);
2023 if (TASK_NICE(p) > 0)
2024 cpustat->nice += user_ticks;
2026 cpustat->user += user_ticks;
2027 cpustat->system += sys_ticks;
2029 /* Task might have expired already, but not scheduled off yet */
2030 if (p->array != rq->active) {
2031 set_tsk_need_resched(p);
2034 spin_lock(&rq->lock);
2036 * The task was running during this tick - update the
2037 * time slice counter. Note: we do not update a thread's
2038 * priority until it either goes to sleep or uses up its
2039 * timeslice. This makes it possible for interactive tasks
2040 * to use up their timeslices at their highest priority levels.
2042 if (unlikely(rt_task(p))) {
2044 * RR tasks need a special form of timeslice management.
2045 * FIFO tasks have no timeslices.
2047 if ((p->policy == SCHED_RR) && !--p->time_slice) {
2048 p->time_slice = task_timeslice(p);
2049 p->first_time_slice = 0;
2050 set_tsk_need_resched(p);
2052 /* put it at the end of the queue: */
2053 dequeue_task(p, rq->active);
2054 enqueue_task(p, rq->active);
2058 if (!--p->time_slice) {
2059 dequeue_task(p, rq->active);
2060 set_tsk_need_resched(p);
2061 p->prio = effective_prio(p);
2062 p->time_slice = task_timeslice(p);
2063 p->first_time_slice = 0;
2065 if (!rq->expired_timestamp)
2066 rq->expired_timestamp = jiffies;
2067 if (!TASK_INTERACTIVE(p) || EXPIRED_STARVING(rq)) {
2068 enqueue_task(p, rq->expired);
2069 if (p->static_prio < rq->best_expired_prio)
2070 rq->best_expired_prio = p->static_prio;
2072 enqueue_task(p, rq->active);
2075 * Prevent a too long timeslice allowing a task to monopolize
2076 * the CPU. We do this by splitting up the timeslice into
2079 * Note: this does not mean the task's timeslices expire or
2080 * get lost in any way, they just might be preempted by
2081 * another task of equal priority. (one with higher
2082 * priority would have preempted this task already.) We
2083 * requeue this task to the end of the list on this priority
2084 * level, which is in essence a round-robin of tasks with
2087 * This only applies to tasks in the interactive
2088 * delta range with at least TIMESLICE_GRANULARITY to requeue.
2090 if (TASK_INTERACTIVE(p) && !((task_timeslice(p) -
2091 p->time_slice) % TIMESLICE_GRANULARITY(p)) &&
2092 (p->time_slice >= TIMESLICE_GRANULARITY(p)) &&
2093 (p->array == rq->active)) {
2095 dequeue_task(p, rq->active);
2096 set_tsk_need_resched(p);
2097 p->prio = effective_prio(p);
2098 enqueue_task(p, rq->active);
2102 spin_unlock(&rq->lock);
2104 rebalance_tick(cpu, rq, NOT_IDLE);
2107 #ifdef CONFIG_SCHED_SMT
2108 static inline void wake_sleeping_dependent(int cpu, runqueue_t *rq)
2111 struct sched_domain *sd = rq->sd;
2112 cpumask_t sibling_map;
2114 if (!(sd->flags & SD_SHARE_CPUPOWER))
2117 cpus_and(sibling_map, sd->span, cpu_online_map);
2118 for_each_cpu_mask(i, sibling_map) {
2127 * If an SMT sibling task is sleeping due to priority
2128 * reasons wake it up now.
2130 if (smt_rq->curr == smt_rq->idle && smt_rq->nr_running)
2131 resched_task(smt_rq->idle);
2135 static inline int dependent_sleeper(int cpu, runqueue_t *rq, task_t *p)
2137 struct sched_domain *sd = rq->sd;
2138 cpumask_t sibling_map;
2141 if (!(sd->flags & SD_SHARE_CPUPOWER))
2144 cpus_and(sibling_map, sd->span, cpu_online_map);
2145 for_each_cpu_mask(i, sibling_map) {
2153 smt_curr = smt_rq->curr;
2156 * If a user task with lower static priority than the
2157 * running task on the SMT sibling is trying to schedule,
2158 * delay it till there is proportionately less timeslice
2159 * left of the sibling task to prevent a lower priority
2160 * task from using an unfair proportion of the
2161 * physical cpu's resources. -ck
2163 if (((smt_curr->time_slice * (100 - sd->per_cpu_gain) / 100) >
2164 task_timeslice(p) || rt_task(smt_curr)) &&
2165 p->mm && smt_curr->mm && !rt_task(p))
2169 * Reschedule a lower priority task on the SMT sibling,
2170 * or wake it up if it has been put to sleep for priority
2173 if ((((p->time_slice * (100 - sd->per_cpu_gain) / 100) >
2174 task_timeslice(smt_curr) || rt_task(p)) &&
2175 smt_curr->mm && p->mm && !rt_task(smt_curr)) ||
2176 (smt_curr == smt_rq->idle && smt_rq->nr_running))
2177 resched_task(smt_curr);
2182 static inline void wake_sleeping_dependent(int cpu, runqueue_t *rq)
2186 static inline int dependent_sleeper(int cpu, runqueue_t *rq, task_t *p)
2193 * schedule() is the main scheduler function.
2195 asmlinkage void __sched schedule(void)
2198 task_t *prev, *next;
2200 prio_array_t *array;
2201 struct list_head *queue;
2202 unsigned long long now;
2203 unsigned long run_time;
2206 //WARN_ON(system_state == SYSTEM_BOOTING);
2208 * Test if we are atomic. Since do_exit() needs to call into
2209 * schedule() atomically, we ignore that path for now.
2210 * Otherwise, whine if we are scheduling when we should not be.
2212 if (likely(!(current->state & (TASK_DEAD | TASK_ZOMBIE)))) {
2213 if (unlikely(in_atomic())) {
2214 printk(KERN_ERR "bad: scheduling while atomic!\n");
2224 release_kernel_lock(prev);
2225 now = sched_clock();
2226 if (likely(now - prev->timestamp < NS_MAX_SLEEP_AVG))
2227 run_time = now - prev->timestamp;
2229 run_time = NS_MAX_SLEEP_AVG;
2232 * Tasks with interactive credits get charged less run_time
2233 * at high sleep_avg to delay them losing their interactive
2236 if (HIGH_CREDIT(prev))
2237 run_time /= (CURRENT_BONUS(prev) ? : 1);
2239 spin_lock_irq(&rq->lock);
2242 * if entering off of a kernel preemption go straight
2243 * to picking the next task.
2245 switch_count = &prev->nivcsw;
2246 if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
2247 switch_count = &prev->nvcsw;
2248 if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
2249 unlikely(signal_pending(prev))))
2250 prev->state = TASK_RUNNING;
2252 deactivate_task(prev, rq);
2255 cpu = smp_processor_id();
2256 if (unlikely(!rq->nr_running)) {
2257 idle_balance(cpu, rq);
2258 if (!rq->nr_running) {
2260 rq->expired_timestamp = 0;
2261 wake_sleeping_dependent(cpu, rq);
2267 if (unlikely(!array->nr_active)) {
2269 * Switch the active and expired arrays.
2271 rq->active = rq->expired;
2272 rq->expired = array;
2274 rq->expired_timestamp = 0;
2275 rq->best_expired_prio = MAX_PRIO;
2278 idx = sched_find_first_bit(array->bitmap);
2279 queue = array->queue + idx;
2280 next = list_entry(queue->next, task_t, run_list);
2282 if (dependent_sleeper(cpu, rq, next)) {
2287 if (!rt_task(next) && next->activated > 0) {
2288 unsigned long long delta = now - next->timestamp;
2290 if (next->activated == 1)
2291 delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
2293 array = next->array;
2294 dequeue_task(next, array);
2295 recalc_task_prio(next, next->timestamp + delta);
2296 enqueue_task(next, array);
2298 next->activated = 0;
2301 if (test_and_clear_tsk_thread_flag(prev,TIF_NEED_RESCHED))
2303 RCU_qsctr(task_cpu(prev))++;
2305 prev->sleep_avg -= run_time;
2306 if ((long)prev->sleep_avg <= 0) {
2307 prev->sleep_avg = 0;
2308 if (!(HIGH_CREDIT(prev) || LOW_CREDIT(prev)))
2309 prev->interactive_credit--;
2311 prev->timestamp = now;
2313 if (likely(prev != next)) {
2314 next->timestamp = now;
2319 prepare_arch_switch(rq, next);
2320 prev = context_switch(rq, prev, next);
2323 finish_task_switch(prev);
2325 spin_unlock_irq(&rq->lock);
2327 reacquire_kernel_lock(current);
2328 preempt_enable_no_resched();
2329 if (test_thread_flag(TIF_NEED_RESCHED))
2333 EXPORT_SYMBOL(schedule);
2335 #ifdef CONFIG_PREEMPT
2337 * this is is the entry point to schedule() from in-kernel preemption
2338 * off of preempt_enable. Kernel preemptions off return from interrupt
2339 * occur there and call schedule directly.
2341 asmlinkage void __sched preempt_schedule(void)
2343 struct thread_info *ti = current_thread_info();
2346 * If there is a non-zero preempt_count or interrupts are disabled,
2347 * we do not want to preempt the current task. Just return..
2349 if (unlikely(ti->preempt_count || irqs_disabled()))
2353 ti->preempt_count = PREEMPT_ACTIVE;
2355 ti->preempt_count = 0;
2357 /* we could miss a preemption opportunity between schedule and now */
2359 if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
2363 EXPORT_SYMBOL(preempt_schedule);
2364 #endif /* CONFIG_PREEMPT */
2366 int default_wake_function(wait_queue_t *curr, unsigned mode, int sync, void *key)
2368 task_t *p = curr->task;
2369 return try_to_wake_up(p, mode, sync);
2372 EXPORT_SYMBOL(default_wake_function);
2375 * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
2376 * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
2377 * number) then we wake all the non-exclusive tasks and one exclusive task.
2379 * There are circumstances in which we can try to wake a task which has already
2380 * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
2381 * zero in this (rare) case, and we handle it by continuing to scan the queue.
2383 static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
2384 int nr_exclusive, int sync, void *key)
2386 struct list_head *tmp, *next;
2388 list_for_each_safe(tmp, next, &q->task_list) {
2391 curr = list_entry(tmp, wait_queue_t, task_list);
2392 flags = curr->flags;
2393 if (curr->func(curr, mode, sync, key) &&
2394 (flags & WQ_FLAG_EXCLUSIVE) &&
2401 * __wake_up - wake up threads blocked on a waitqueue.
2403 * @mode: which threads
2404 * @nr_exclusive: how many wake-one or wake-many threads to wake up
2406 void fastcall __wake_up(wait_queue_head_t *q, unsigned int mode,
2407 int nr_exclusive, void *key)
2409 unsigned long flags;
2411 spin_lock_irqsave(&q->lock, flags);
2412 __wake_up_common(q, mode, nr_exclusive, 0, key);
2413 spin_unlock_irqrestore(&q->lock, flags);
2416 EXPORT_SYMBOL(__wake_up);
2419 * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
2421 void fastcall __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
2423 __wake_up_common(q, mode, 1, 0, NULL);
2427 * __wake_up - sync- wake up threads blocked on a waitqueue.
2429 * @mode: which threads
2430 * @nr_exclusive: how many wake-one or wake-many threads to wake up
2432 * The sync wakeup differs that the waker knows that it will schedule
2433 * away soon, so while the target thread will be woken up, it will not
2434 * be migrated to another CPU - ie. the two threads are 'synchronized'
2435 * with each other. This can prevent needless bouncing between CPUs.
2437 * On UP it can prevent extra preemption.
2439 void fastcall __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
2441 unsigned long flags;
2447 if (unlikely(!nr_exclusive))
2450 spin_lock_irqsave(&q->lock, flags);
2451 __wake_up_common(q, mode, nr_exclusive, sync, NULL);
2452 spin_unlock_irqrestore(&q->lock, flags);
2454 EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
2456 void fastcall complete(struct completion *x)
2458 unsigned long flags;
2460 spin_lock_irqsave(&x->wait.lock, flags);
2462 __wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
2464 spin_unlock_irqrestore(&x->wait.lock, flags);
2466 EXPORT_SYMBOL(complete);
2468 void fastcall complete_all(struct completion *x)
2470 unsigned long flags;
2472 spin_lock_irqsave(&x->wait.lock, flags);
2473 x->done += UINT_MAX/2;
2474 __wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
2476 spin_unlock_irqrestore(&x->wait.lock, flags);
2478 EXPORT_SYMBOL(complete_all);
2480 void fastcall __sched wait_for_completion(struct completion *x)
2483 spin_lock_irq(&x->wait.lock);
2485 DECLARE_WAITQUEUE(wait, current);
2487 wait.flags |= WQ_FLAG_EXCLUSIVE;
2488 __add_wait_queue_tail(&x->wait, &wait);
2490 __set_current_state(TASK_UNINTERRUPTIBLE);
2491 spin_unlock_irq(&x->wait.lock);
2493 spin_lock_irq(&x->wait.lock);
2495 __remove_wait_queue(&x->wait, &wait);
2498 spin_unlock_irq(&x->wait.lock);
2500 EXPORT_SYMBOL(wait_for_completion);
2502 #define SLEEP_ON_VAR \
2503 unsigned long flags; \
2504 wait_queue_t wait; \
2505 init_waitqueue_entry(&wait, current);
2507 #define SLEEP_ON_HEAD \
2508 spin_lock_irqsave(&q->lock,flags); \
2509 __add_wait_queue(q, &wait); \
2510 spin_unlock(&q->lock);
2512 #define SLEEP_ON_TAIL \
2513 spin_lock_irq(&q->lock); \
2514 __remove_wait_queue(q, &wait); \
2515 spin_unlock_irqrestore(&q->lock, flags);
2517 #define SLEEP_ON_BKLCHECK \
2518 if (unlikely(!kernel_locked()) && \
2519 sleep_on_bkl_warnings < 10) { \
2520 sleep_on_bkl_warnings++; \
2524 static int sleep_on_bkl_warnings;
2526 void fastcall __sched interruptible_sleep_on(wait_queue_head_t *q)
2532 current->state = TASK_INTERRUPTIBLE;
2539 EXPORT_SYMBOL(interruptible_sleep_on);
2541 long fastcall __sched interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
2547 current->state = TASK_INTERRUPTIBLE;
2550 timeout = schedule_timeout(timeout);
2556 EXPORT_SYMBOL(interruptible_sleep_on_timeout);
2558 long fastcall __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
2564 current->state = TASK_UNINTERRUPTIBLE;
2567 timeout = schedule_timeout(timeout);
2573 EXPORT_SYMBOL(sleep_on_timeout);
2575 void set_user_nice(task_t *p, long nice)
2577 unsigned long flags;
2578 prio_array_t *array;
2580 int old_prio, new_prio, delta;
2582 if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
2585 * We have to be careful, if called from sys_setpriority(),
2586 * the task might be in the middle of scheduling on another CPU.
2588 rq = task_rq_lock(p, &flags);
2590 * The RT priorities are set via setscheduler(), but we still
2591 * allow the 'normal' nice value to be set - but as expected
2592 * it wont have any effect on scheduling until the task is
2596 p->static_prio = NICE_TO_PRIO(nice);
2601 dequeue_task(p, array);
2604 new_prio = NICE_TO_PRIO(nice);
2605 delta = new_prio - old_prio;
2606 p->static_prio = NICE_TO_PRIO(nice);
2610 enqueue_task(p, array);
2612 * If the task increased its priority or is running and
2613 * lowered its priority, then reschedule its CPU:
2615 if (delta < 0 || (delta > 0 && task_running(rq, p)))
2616 resched_task(rq->curr);
2619 task_rq_unlock(rq, &flags);
2622 EXPORT_SYMBOL(set_user_nice);
2624 #ifdef __ARCH_WANT_SYS_NICE
2627 * sys_nice - change the priority of the current process.
2628 * @increment: priority increment
2630 * sys_setpriority is a more generic, but much slower function that
2631 * does similar things.
2633 asmlinkage long sys_nice(int increment)
2639 * Setpriority might change our priority at the same moment.
2640 * We don't have to worry. Conceptually one call occurs first
2641 * and we have a single winner.
2643 if (increment < 0) {
2644 if (!capable(CAP_SYS_NICE))
2646 if (increment < -40)
2652 nice = PRIO_TO_NICE(current->static_prio) + increment;
2658 retval = security_task_setnice(current, nice);
2662 set_user_nice(current, nice);
2669 * task_prio - return the priority value of a given task.
2670 * @p: the task in question.
2672 * This is the priority value as seen by users in /proc.
2673 * RT tasks are offset by -200. Normal tasks are centered
2674 * around 0, value goes from -16 to +15.
2676 int task_prio(const task_t *p)
2678 return p->prio - MAX_RT_PRIO;
2682 * task_nice - return the nice value of a given task.
2683 * @p: the task in question.
2685 int task_nice(const task_t *p)
2687 return TASK_NICE(p);
2690 EXPORT_SYMBOL(task_nice);
2693 * idle_cpu - is a given cpu idle currently?
2694 * @cpu: the processor in question.
2696 int idle_cpu(int cpu)
2698 return cpu_curr(cpu) == cpu_rq(cpu)->idle;
2701 EXPORT_SYMBOL_GPL(idle_cpu);
2704 * find_process_by_pid - find a process with a matching PID value.
2705 * @pid: the pid in question.
2707 static inline task_t *find_process_by_pid(pid_t pid)
2709 return pid ? find_task_by_pid(pid) : current;
2712 /* Actually do priority change: must hold rq lock. */
2713 static void __setscheduler(struct task_struct *p, int policy, int prio)
2717 p->rt_priority = prio;
2718 if (policy != SCHED_NORMAL)
2719 p->prio = MAX_USER_RT_PRIO-1 - p->rt_priority;
2721 p->prio = p->static_prio;
2725 * setscheduler - change the scheduling policy and/or RT priority of a thread.
2727 static int setscheduler(pid_t pid, int policy, struct sched_param __user *param)
2729 struct sched_param lp;
2730 int retval = -EINVAL;
2732 prio_array_t *array;
2733 unsigned long flags;
2737 if (!param || pid < 0)
2741 if (copy_from_user(&lp, param, sizeof(struct sched_param)))
2745 * We play safe to avoid deadlocks.
2747 read_lock_irq(&tasklist_lock);
2749 p = find_process_by_pid(pid);
2753 goto out_unlock_tasklist;
2756 * To be able to change p->policy safely, the apropriate
2757 * runqueue lock must be held.
2759 rq = task_rq_lock(p, &flags);
2765 if (policy != SCHED_FIFO && policy != SCHED_RR &&
2766 policy != SCHED_NORMAL)
2771 * Valid priorities for SCHED_FIFO and SCHED_RR are
2772 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL is 0.
2775 if (lp.sched_priority < 0 || lp.sched_priority > MAX_USER_RT_PRIO-1)
2777 if ((policy == SCHED_NORMAL) != (lp.sched_priority == 0))
2781 if ((policy == SCHED_FIFO || policy == SCHED_RR) &&
2782 !capable(CAP_SYS_NICE))
2784 if ((current->euid != p->euid) && (current->euid != p->uid) &&
2785 !capable(CAP_SYS_NICE))
2788 retval = security_task_setscheduler(p, policy, &lp);
2794 deactivate_task(p, task_rq(p));
2797 __setscheduler(p, policy, lp.sched_priority);
2799 __activate_task(p, task_rq(p));
2801 * Reschedule if we are currently running on this runqueue and
2802 * our priority decreased, or if we are not currently running on
2803 * this runqueue and our priority is higher than the current's
2805 if (task_running(rq, p)) {
2806 if (p->prio > oldprio)
2807 resched_task(rq->curr);
2808 } else if (TASK_PREEMPTS_CURR(p, rq))
2809 resched_task(rq->curr);
2813 task_rq_unlock(rq, &flags);
2814 out_unlock_tasklist:
2815 read_unlock_irq(&tasklist_lock);
2822 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
2823 * @pid: the pid in question.
2824 * @policy: new policy
2825 * @param: structure containing the new RT priority.
2827 asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
2828 struct sched_param __user *param)
2830 return setscheduler(pid, policy, param);
2834 * sys_sched_setparam - set/change the RT priority of a thread
2835 * @pid: the pid in question.
2836 * @param: structure containing the new RT priority.
2838 asmlinkage long sys_sched_setparam(pid_t pid, struct sched_param __user *param)
2840 return setscheduler(pid, -1, param);
2844 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
2845 * @pid: the pid in question.
2847 asmlinkage long sys_sched_getscheduler(pid_t pid)
2849 int retval = -EINVAL;
2856 read_lock(&tasklist_lock);
2857 p = find_process_by_pid(pid);
2859 retval = security_task_getscheduler(p);
2863 read_unlock(&tasklist_lock);
2870 * sys_sched_getscheduler - get the RT priority of a thread
2871 * @pid: the pid in question.
2872 * @param: structure containing the RT priority.
2874 asmlinkage long sys_sched_getparam(pid_t pid, struct sched_param __user *param)
2876 struct sched_param lp;
2877 int retval = -EINVAL;
2880 if (!param || pid < 0)
2883 read_lock(&tasklist_lock);
2884 p = find_process_by_pid(pid);
2889 retval = security_task_getscheduler(p);
2893 lp.sched_priority = p->rt_priority;
2894 read_unlock(&tasklist_lock);
2897 * This one might sleep, we cannot do it with a spinlock held ...
2899 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
2905 read_unlock(&tasklist_lock);
2910 * sys_sched_setaffinity - set the cpu affinity of a process
2911 * @pid: pid of the process
2912 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
2913 * @user_mask_ptr: user-space pointer to the new cpu mask
2915 asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
2916 unsigned long __user *user_mask_ptr)
2922 if (len < sizeof(new_mask))
2925 if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
2929 read_lock(&tasklist_lock);
2931 p = find_process_by_pid(pid);
2933 read_unlock(&tasklist_lock);
2934 unlock_cpu_hotplug();
2939 * It is not safe to call set_cpus_allowed with the
2940 * tasklist_lock held. We will bump the task_struct's
2941 * usage count and then drop tasklist_lock.
2944 read_unlock(&tasklist_lock);
2947 if ((current->euid != p->euid) && (current->euid != p->uid) &&
2948 !capable(CAP_SYS_NICE))
2951 retval = set_cpus_allowed(p, new_mask);
2955 unlock_cpu_hotplug();
2960 * Represents all cpu's present in the system
2961 * In systems capable of hotplug, this map could dynamically grow
2962 * as new cpu's are detected in the system via any platform specific
2963 * method, such as ACPI for e.g.
2966 cpumask_t cpu_present_map;
2967 EXPORT_SYMBOL(cpu_present_map);
2970 cpumask_t cpu_online_map = CPU_MASK_ALL;
2971 cpumask_t cpu_possible_map = CPU_MASK_ALL;
2975 * sys_sched_getaffinity - get the cpu affinity of a process
2976 * @pid: pid of the process
2977 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
2978 * @user_mask_ptr: user-space pointer to hold the current cpu mask
2980 asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
2981 unsigned long __user *user_mask_ptr)
2983 unsigned int real_len;
2988 real_len = sizeof(mask);
2993 read_lock(&tasklist_lock);
2996 p = find_process_by_pid(pid);
3001 cpus_and(mask, p->cpus_allowed, cpu_possible_map);
3004 read_unlock(&tasklist_lock);
3005 unlock_cpu_hotplug();
3008 if (copy_to_user(user_mask_ptr, &mask, real_len))
3014 * sys_sched_yield - yield the current processor to other threads.
3016 * this function yields the current CPU by moving the calling thread
3017 * to the expired array. If there are no other threads running on this
3018 * CPU then this function will return.
3020 asmlinkage long sys_sched_yield(void)
3022 runqueue_t *rq = this_rq_lock();
3023 prio_array_t *array = current->array;
3024 prio_array_t *target = rq->expired;
3027 * We implement yielding by moving the task into the expired
3030 * (special rule: RT tasks will just roundrobin in the active
3033 if (unlikely(rt_task(current)))
3034 target = rq->active;
3036 dequeue_task(current, array);
3037 enqueue_task(current, target);
3040 * Since we are going to call schedule() anyway, there's
3041 * no need to preempt or enable interrupts:
3043 _raw_spin_unlock(&rq->lock);
3044 preempt_enable_no_resched();
3051 void __sched __cond_resched(void)
3053 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
3054 __might_sleep(__FILE__, __LINE__, 0);
3057 * The system_state check is somewhat ugly but we might be
3058 * called during early boot when we are not yet ready to reschedule.
3060 if (need_resched() && system_state >= SYSTEM_BOOTING_SCHEDULER_OK) {
3061 set_current_state(TASK_RUNNING);
3066 EXPORT_SYMBOL(__cond_resched);
3068 void __sched __cond_resched_lock(spinlock_t * lock)
3070 if (need_resched()) {
3071 _raw_spin_unlock(lock);
3072 preempt_enable_no_resched();
3073 set_current_state(TASK_RUNNING);
3079 EXPORT_SYMBOL(__cond_resched_lock);
3082 * yield - yield the current processor to other threads.
3084 * this is a shortcut for kernel-space yielding - it marks the
3085 * thread runnable and calls sys_sched_yield().
3087 void __sched yield(void)
3089 set_current_state(TASK_RUNNING);
3093 EXPORT_SYMBOL(yield);
3096 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
3097 * that process accounting knows that this is a task in IO wait state.
3099 * But don't do that if it is a deliberate, throttling IO wait (this task
3100 * has set its backing_dev_info: the queue against which it should throttle)
3102 void __sched io_schedule(void)
3104 struct runqueue *rq = this_rq();
3106 atomic_inc(&rq->nr_iowait);
3108 atomic_dec(&rq->nr_iowait);
3111 EXPORT_SYMBOL(io_schedule);
3113 long __sched io_schedule_timeout(long timeout)
3115 struct runqueue *rq = this_rq();
3118 atomic_inc(&rq->nr_iowait);
3119 ret = schedule_timeout(timeout);
3120 atomic_dec(&rq->nr_iowait);
3125 * sys_sched_get_priority_max - return maximum RT priority.
3126 * @policy: scheduling class.
3128 * this syscall returns the maximum rt_priority that can be used
3129 * by a given scheduling class.
3131 asmlinkage long sys_sched_get_priority_max(int policy)
3138 ret = MAX_USER_RT_PRIO-1;
3148 * sys_sched_get_priority_min - return minimum RT priority.
3149 * @policy: scheduling class.
3151 * this syscall returns the minimum rt_priority that can be used
3152 * by a given scheduling class.
3154 asmlinkage long sys_sched_get_priority_min(int policy)
3170 * sys_sched_rr_get_interval - return the default timeslice of a process.
3171 * @pid: pid of the process.
3172 * @interval: userspace pointer to the timeslice value.
3174 * this syscall writes the default timeslice value of a given process
3175 * into the user-space timespec buffer. A value of '0' means infinity.
3178 long sys_sched_rr_get_interval(pid_t pid, struct timespec __user *interval)
3180 int retval = -EINVAL;
3188 read_lock(&tasklist_lock);
3189 p = find_process_by_pid(pid);
3193 retval = security_task_getscheduler(p);
3197 jiffies_to_timespec(p->policy & SCHED_FIFO ?
3198 0 : task_timeslice(p), &t);
3199 read_unlock(&tasklist_lock);
3200 retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
3204 read_unlock(&tasklist_lock);
3208 static inline struct task_struct *eldest_child(struct task_struct *p)
3210 if (list_empty(&p->children)) return NULL;
3211 return list_entry(p->children.next,struct task_struct,sibling);
3214 static inline struct task_struct *older_sibling(struct task_struct *p)
3216 if (p->sibling.prev==&p->parent->children) return NULL;
3217 return list_entry(p->sibling.prev,struct task_struct,sibling);
3220 static inline struct task_struct *younger_sibling(struct task_struct *p)
3222 if (p->sibling.next==&p->parent->children) return NULL;
3223 return list_entry(p->sibling.next,struct task_struct,sibling);
3226 static void show_task(task_t * p)
3230 unsigned long free = 0;
3231 static const char *stat_nam[] = { "R", "S", "D", "T", "Z", "W" };
3233 printk("%-13.13s ", p->comm);
3234 state = p->state ? __ffs(p->state) + 1 : 0;
3235 if (state < ARRAY_SIZE(stat_nam))
3236 printk(stat_nam[state]);
3239 #if (BITS_PER_LONG == 32)
3240 if (state == TASK_RUNNING)
3241 printk(" running ");
3243 printk(" %08lX ", thread_saved_pc(p));
3245 if (state == TASK_RUNNING)
3246 printk(" running task ");
3248 printk(" %016lx ", thread_saved_pc(p));
3250 #ifdef CONFIG_DEBUG_STACK_USAGE
3252 unsigned long * n = (unsigned long *) (p->thread_info+1);
3255 free = (unsigned long) n - (unsigned long)(p->thread_info+1);
3258 printk("%5lu %5d %6d ", free, p->pid, p->parent->pid);
3259 if ((relative = eldest_child(p)))
3260 printk("%5d ", relative->pid);
3263 if ((relative = younger_sibling(p)))
3264 printk("%7d", relative->pid);
3267 if ((relative = older_sibling(p)))
3268 printk(" %5d", relative->pid);
3272 printk(" (L-TLB)\n");
3274 printk(" (NOTLB)\n");
3276 if (state != TASK_RUNNING)
3277 show_stack(p, NULL);
3280 void show_state(void)
3284 #if (BITS_PER_LONG == 32)
3287 printk(" task PC pid father child younger older\n");
3291 printk(" task PC pid father child younger older\n");
3293 read_lock(&tasklist_lock);
3294 do_each_thread(g, p) {
3296 * reset the NMI-timeout, listing all files on a slow
3297 * console might take alot of time:
3299 touch_nmi_watchdog();
3301 } while_each_thread(g, p);
3303 read_unlock(&tasklist_lock);
3306 EXPORT_SYMBOL_GPL(show_state);
3308 void __devinit init_idle(task_t *idle, int cpu)
3310 runqueue_t *idle_rq = cpu_rq(cpu), *rq = cpu_rq(task_cpu(idle));
3311 unsigned long flags;
3313 local_irq_save(flags);
3314 double_rq_lock(idle_rq, rq);
3316 idle_rq->curr = idle_rq->idle = idle;
3317 deactivate_task(idle, rq);
3319 idle->prio = MAX_PRIO;
3320 idle->state = TASK_RUNNING;
3321 set_task_cpu(idle, cpu);
3322 double_rq_unlock(idle_rq, rq);
3323 set_tsk_need_resched(idle);
3324 local_irq_restore(flags);
3326 /* Set the preempt count _outside_ the spinlocks! */
3327 #ifdef CONFIG_PREEMPT
3328 idle->thread_info->preempt_count = (idle->lock_depth >= 0);
3330 idle->thread_info->preempt_count = 0;
3335 * In a system that switches off the HZ timer nohz_cpu_mask
3336 * indicates which cpus entered this state. This is used
3337 * in the rcu update to wait only for active cpus. For system
3338 * which do not switch off the HZ timer nohz_cpu_mask should
3339 * always be CPU_MASK_NONE.
3341 cpumask_t nohz_cpu_mask = CPU_MASK_NONE;
3345 * This is how migration works:
3347 * 1) we queue a migration_req_t structure in the source CPU's
3348 * runqueue and wake up that CPU's migration thread.
3349 * 2) we down() the locked semaphore => thread blocks.
3350 * 3) migration thread wakes up (implicitly it forces the migrated
3351 * thread off the CPU)
3352 * 4) it gets the migration request and checks whether the migrated
3353 * task is still in the wrong runqueue.
3354 * 5) if it's in the wrong runqueue then the migration thread removes
3355 * it and puts it into the right queue.
3356 * 6) migration thread up()s the semaphore.
3357 * 7) we wake up and the migration is done.
3361 * Change a given task's CPU affinity. Migrate the thread to a
3362 * proper CPU and schedule it away if the CPU it's executing on
3363 * is removed from the allowed bitmask.
3365 * NOTE: the caller must have a valid reference to the task, the
3366 * task must not exit() & deallocate itself prematurely. The
3367 * call is not atomic; no spinlocks may be held.
3369 int set_cpus_allowed(task_t *p, cpumask_t new_mask)
3371 unsigned long flags;
3373 migration_req_t req;
3376 rq = task_rq_lock(p, &flags);
3377 if (!cpus_intersects(new_mask, cpu_online_map)) {
3382 p->cpus_allowed = new_mask;
3383 /* Can the task run on the task's current CPU? If so, we're done */
3384 if (cpu_isset(task_cpu(p), new_mask))
3387 if (migrate_task(p, any_online_cpu(new_mask), &req)) {
3388 /* Need help from migration thread: drop lock and wait. */
3389 task_rq_unlock(rq, &flags);
3390 wake_up_process(rq->migration_thread);
3391 wait_for_completion(&req.done);
3392 tlb_migrate_finish(p->mm);
3396 task_rq_unlock(rq, &flags);
3400 EXPORT_SYMBOL_GPL(set_cpus_allowed);
3403 * Move (not current) task off this cpu, onto dest cpu. We're doing
3404 * this because either it can't run here any more (set_cpus_allowed()
3405 * away from this CPU, or CPU going down), or because we're
3406 * attempting to rebalance this task on exec (sched_balance_exec).
3408 * So we race with normal scheduler movements, but that's OK, as long
3409 * as the task is no longer on this CPU.
3411 static void __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
3413 runqueue_t *rq_dest, *rq_src;
3415 if (unlikely(cpu_is_offline(dest_cpu)))
3418 rq_src = cpu_rq(src_cpu);
3419 rq_dest = cpu_rq(dest_cpu);
3421 double_rq_lock(rq_src, rq_dest);
3422 /* Already moved. */
3423 if (task_cpu(p) != src_cpu)
3425 /* Affinity changed (again). */
3426 if (!cpu_isset(dest_cpu, p->cpus_allowed))
3429 set_task_cpu(p, dest_cpu);
3432 * Sync timestamp with rq_dest's before activating.
3433 * The same thing could be achieved by doing this step
3434 * afterwards, and pretending it was a local activate.
3435 * This way is cleaner and logically correct.
3437 p->timestamp = p->timestamp - rq_src->timestamp_last_tick
3438 + rq_dest->timestamp_last_tick;
3439 deactivate_task(p, rq_src);
3440 activate_task(p, rq_dest, 0);
3441 if (TASK_PREEMPTS_CURR(p, rq_dest))
3442 resched_task(rq_dest->curr);
3446 double_rq_unlock(rq_src, rq_dest);
3450 * migration_thread - this is a highprio system thread that performs
3451 * thread migration by bumping thread off CPU then 'pushing' onto
3454 static int migration_thread(void * data)
3457 int cpu = (long)data;
3460 BUG_ON(rq->migration_thread != current);
3462 set_current_state(TASK_INTERRUPTIBLE);
3463 while (!kthread_should_stop()) {
3464 struct list_head *head;
3465 migration_req_t *req;
3467 if (current->flags & PF_FREEZE)
3468 refrigerator(PF_FREEZE);
3470 spin_lock_irq(&rq->lock);
3472 if (cpu_is_offline(cpu)) {
3473 spin_unlock_irq(&rq->lock);
3477 if (rq->active_balance) {
3478 active_load_balance(rq, cpu);
3479 rq->active_balance = 0;
3482 head = &rq->migration_queue;
3484 if (list_empty(head)) {
3485 spin_unlock_irq(&rq->lock);
3487 set_current_state(TASK_INTERRUPTIBLE);
3490 req = list_entry(head->next, migration_req_t, list);
3491 list_del_init(head->next);
3493 if (req->type == REQ_MOVE_TASK) {
3494 spin_unlock(&rq->lock);
3495 __migrate_task(req->task, smp_processor_id(),
3498 } else if (req->type == REQ_SET_DOMAIN) {
3500 spin_unlock_irq(&rq->lock);
3502 spin_unlock_irq(&rq->lock);
3506 complete(&req->done);
3508 __set_current_state(TASK_RUNNING);
3512 /* Wait for kthread_stop */
3513 set_current_state(TASK_INTERRUPTIBLE);
3514 while (!kthread_should_stop()) {
3516 set_current_state(TASK_INTERRUPTIBLE);
3518 __set_current_state(TASK_RUNNING);
3522 #ifdef CONFIG_HOTPLUG_CPU
3523 /* migrate_all_tasks - function to migrate all tasks from the dead cpu. */
3524 static void migrate_all_tasks(int src_cpu)
3526 struct task_struct *tsk, *t;
3530 write_lock_irq(&tasklist_lock);
3532 /* watch out for per node tasks, let's stay on this node */
3533 node = cpu_to_node(src_cpu);
3535 do_each_thread(t, tsk) {
3540 if (task_cpu(tsk) != src_cpu)
3543 /* Figure out where this task should go (attempting to
3544 * keep it on-node), and check if it can be migrated
3545 * as-is. NOTE that kernel threads bound to more than
3546 * one online cpu will be migrated. */
3547 mask = node_to_cpumask(node);
3548 cpus_and(mask, mask, tsk->cpus_allowed);
3549 dest_cpu = any_online_cpu(mask);
3550 if (dest_cpu == NR_CPUS)
3551 dest_cpu = any_online_cpu(tsk->cpus_allowed);
3552 if (dest_cpu == NR_CPUS) {
3553 cpus_setall(tsk->cpus_allowed);
3554 dest_cpu = any_online_cpu(tsk->cpus_allowed);
3556 /* Don't tell them about moving exiting tasks
3557 or kernel threads (both mm NULL), since
3558 they never leave kernel. */
3559 if (tsk->mm && printk_ratelimit())
3560 printk(KERN_INFO "process %d (%s) no "
3561 "longer affine to cpu%d\n",
3562 tsk->pid, tsk->comm, src_cpu);
3565 __migrate_task(tsk, src_cpu, dest_cpu);
3566 } while_each_thread(t, tsk);
3568 write_unlock_irq(&tasklist_lock);
3571 /* Schedules idle task to be the next runnable task on current CPU.
3572 * It does so by boosting its priority to highest possible and adding it to
3573 * the _front_ of runqueue. Used by CPU offline code.
3575 void sched_idle_next(void)
3577 int cpu = smp_processor_id();
3578 runqueue_t *rq = this_rq();
3579 struct task_struct *p = rq->idle;
3580 unsigned long flags;
3582 /* cpu has to be offline */
3583 BUG_ON(cpu_online(cpu));
3585 /* Strictly not necessary since rest of the CPUs are stopped by now
3586 * and interrupts disabled on current cpu.
3588 spin_lock_irqsave(&rq->lock, flags);
3590 __setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
3591 /* Add idle task to _front_ of it's priority queue */
3592 __activate_idle_task(p, rq);
3594 spin_unlock_irqrestore(&rq->lock, flags);
3596 #endif /* CONFIG_HOTPLUG_CPU */
3599 * migration_call - callback that gets triggered when a CPU is added.
3600 * Here we can start up the necessary migration thread for the new CPU.
3602 static int migration_call(struct notifier_block *nfb, unsigned long action,
3605 int cpu = (long)hcpu;
3606 struct task_struct *p;
3607 struct runqueue *rq;
3608 unsigned long flags;
3611 case CPU_UP_PREPARE:
3612 p = kthread_create(migration_thread, hcpu, "migration/%d",cpu);
3615 p->flags |= PF_NOFREEZE;
3616 kthread_bind(p, cpu);
3617 /* Must be high prio: stop_machine expects to yield to it. */
3618 rq = task_rq_lock(p, &flags);
3619 __setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
3620 task_rq_unlock(rq, &flags);
3621 cpu_rq(cpu)->migration_thread = p;
3624 /* Strictly unneccessary, as first user will wake it. */
3625 wake_up_process(cpu_rq(cpu)->migration_thread);
3627 #ifdef CONFIG_HOTPLUG_CPU
3628 case CPU_UP_CANCELED:
3629 /* Unbind it from offline cpu so it can run. Fall thru. */
3630 kthread_bind(cpu_rq(cpu)->migration_thread,smp_processor_id());
3631 kthread_stop(cpu_rq(cpu)->migration_thread);
3632 cpu_rq(cpu)->migration_thread = NULL;
3635 migrate_all_tasks(cpu);
3637 kthread_stop(rq->migration_thread);
3638 rq->migration_thread = NULL;
3639 /* Idle task back to normal (off runqueue, low prio) */
3640 rq = task_rq_lock(rq->idle, &flags);
3641 deactivate_task(rq->idle, rq);
3642 rq->idle->static_prio = MAX_PRIO;
3643 __setscheduler(rq->idle, SCHED_NORMAL, 0);
3644 task_rq_unlock(rq, &flags);
3645 BUG_ON(rq->nr_running != 0);
3647 /* No need to migrate the tasks: it was best-effort if
3648 * they didn't do lock_cpu_hotplug(). Just wake up
3649 * the requestors. */
3650 spin_lock_irq(&rq->lock);
3651 while (!list_empty(&rq->migration_queue)) {
3652 migration_req_t *req;
3653 req = list_entry(rq->migration_queue.next,
3654 migration_req_t, list);
3655 BUG_ON(req->type != REQ_MOVE_TASK);
3656 list_del_init(&req->list);
3657 complete(&req->done);
3659 spin_unlock_irq(&rq->lock);
3666 /* Register at highest priority so that task migration (migrate_all_tasks)
3667 * happens before everything else.
3669 static struct notifier_block __devinitdata migration_notifier = {
3670 .notifier_call = migration_call,
3674 int __init migration_init(void)
3676 void *cpu = (void *)(long)smp_processor_id();
3677 /* Start one for boot CPU. */
3678 migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
3679 migration_call(&migration_notifier, CPU_ONLINE, cpu);
3680 register_cpu_notifier(&migration_notifier);
3686 * The 'big kernel lock'
3688 * This spinlock is taken and released recursively by lock_kernel()
3689 * and unlock_kernel(). It is transparently dropped and reaquired
3690 * over schedule(). It is used to protect legacy code that hasn't
3691 * been migrated to a proper locking design yet.
3693 * Don't use in new code.
3695 * Note: spinlock debugging needs this even on !CONFIG_SMP.
3697 spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
3698 EXPORT_SYMBOL(kernel_flag);
3701 /* Attach the domain 'sd' to 'cpu' as its base domain */
3702 void cpu_attach_domain(struct sched_domain *sd, int cpu)
3704 migration_req_t req;
3705 unsigned long flags;
3706 runqueue_t *rq = cpu_rq(cpu);
3711 spin_lock_irqsave(&rq->lock, flags);
3713 if (cpu == smp_processor_id() || !cpu_online(cpu)) {
3716 init_completion(&req.done);
3717 req.type = REQ_SET_DOMAIN;
3719 list_add(&req.list, &rq->migration_queue);
3723 spin_unlock_irqrestore(&rq->lock, flags);
3726 wake_up_process(rq->migration_thread);
3727 wait_for_completion(&req.done);
3730 unlock_cpu_hotplug();
3733 #ifdef ARCH_HAS_SCHED_DOMAIN
3734 extern void __init arch_init_sched_domains(void);
3736 static struct sched_group sched_group_cpus[NR_CPUS];
3737 static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
3739 static struct sched_group sched_group_nodes[MAX_NUMNODES];
3740 static DEFINE_PER_CPU(struct sched_domain, node_domains);
3741 static void __init arch_init_sched_domains(void)
3744 struct sched_group *first_node = NULL, *last_node = NULL;
3746 /* Set up domains */
3748 int node = cpu_to_node(i);
3749 cpumask_t nodemask = node_to_cpumask(node);
3750 struct sched_domain *node_sd = &per_cpu(node_domains, i);
3751 struct sched_domain *cpu_sd = &per_cpu(cpu_domains, i);
3753 *node_sd = SD_NODE_INIT;
3754 node_sd->span = cpu_possible_map;
3755 node_sd->groups = &sched_group_nodes[cpu_to_node(i)];
3757 *cpu_sd = SD_CPU_INIT;
3758 cpus_and(cpu_sd->span, nodemask, cpu_possible_map);
3759 cpu_sd->groups = &sched_group_cpus[i];
3760 cpu_sd->parent = node_sd;
3764 for (i = 0; i < MAX_NUMNODES; i++) {
3765 cpumask_t tmp = node_to_cpumask(i);
3767 struct sched_group *first_cpu = NULL, *last_cpu = NULL;
3768 struct sched_group *node = &sched_group_nodes[i];
3771 cpus_and(nodemask, tmp, cpu_possible_map);
3773 if (cpus_empty(nodemask))
3776 node->cpumask = nodemask;
3777 node->cpu_power = SCHED_LOAD_SCALE * cpus_weight(node->cpumask);
3779 for_each_cpu_mask(j, node->cpumask) {
3780 struct sched_group *cpu = &sched_group_cpus[j];
3782 cpus_clear(cpu->cpumask);
3783 cpu_set(j, cpu->cpumask);
3784 cpu->cpu_power = SCHED_LOAD_SCALE;
3789 last_cpu->next = cpu;
3792 last_cpu->next = first_cpu;
3797 last_node->next = node;
3800 last_node->next = first_node;
3804 struct sched_domain *cpu_sd = &per_cpu(cpu_domains, i);
3805 cpu_attach_domain(cpu_sd, i);
3809 #else /* !CONFIG_NUMA */
3810 static void __init arch_init_sched_domains(void)
3813 struct sched_group *first_cpu = NULL, *last_cpu = NULL;
3815 /* Set up domains */
3817 struct sched_domain *cpu_sd = &per_cpu(cpu_domains, i);
3819 *cpu_sd = SD_CPU_INIT;
3820 cpu_sd->span = cpu_possible_map;
3821 cpu_sd->groups = &sched_group_cpus[i];
3824 /* Set up CPU groups */
3825 for_each_cpu_mask(i, cpu_possible_map) {
3826 struct sched_group *cpu = &sched_group_cpus[i];
3828 cpus_clear(cpu->cpumask);
3829 cpu_set(i, cpu->cpumask);
3830 cpu->cpu_power = SCHED_LOAD_SCALE;
3835 last_cpu->next = cpu;
3838 last_cpu->next = first_cpu;
3840 mb(); /* domains were modified outside the lock */
3842 struct sched_domain *cpu_sd = &per_cpu(cpu_domains, i);
3843 cpu_attach_domain(cpu_sd, i);
3847 #endif /* CONFIG_NUMA */
3848 #endif /* ARCH_HAS_SCHED_DOMAIN */
3850 #define SCHED_DOMAIN_DEBUG
3851 #ifdef SCHED_DOMAIN_DEBUG
3852 void sched_domain_debug(void)
3857 runqueue_t *rq = cpu_rq(i);
3858 struct sched_domain *sd;
3863 printk(KERN_DEBUG "CPU%d: %s\n",
3864 i, (cpu_online(i) ? " online" : "offline"));
3869 struct sched_group *group = sd->groups;
3870 cpumask_t groupmask;
3872 cpumask_scnprintf(str, NR_CPUS, sd->span);
3873 cpus_clear(groupmask);
3876 for (j = 0; j < level + 1; j++)
3878 printk("domain %d: span %s\n", level, str);
3880 if (!cpu_isset(i, sd->span))
3881 printk(KERN_DEBUG "ERROR domain->span does not contain CPU%d\n", i);
3882 if (!cpu_isset(i, group->cpumask))
3883 printk(KERN_DEBUG "ERROR domain->groups does not contain CPU%d\n", i);
3884 if (!group->cpu_power)
3885 printk(KERN_DEBUG "ERROR domain->cpu_power not set\n");
3888 for (j = 0; j < level + 2; j++)
3893 printk(" ERROR: NULL");
3897 if (!cpus_weight(group->cpumask))
3898 printk(" ERROR empty group:");
3900 if (cpus_intersects(groupmask, group->cpumask))
3901 printk(" ERROR repeated CPUs:");
3903 cpus_or(groupmask, groupmask, group->cpumask);
3905 cpumask_scnprintf(str, NR_CPUS, group->cpumask);
3908 group = group->next;
3909 } while (group != sd->groups);
3912 if (!cpus_equal(sd->span, groupmask))
3913 printk(KERN_DEBUG "ERROR groups don't span domain->span\n");
3919 if (!cpus_subset(groupmask, sd->span))
3920 printk(KERN_DEBUG "ERROR parent span is not a superset of domain->span\n");
3927 #define sched_domain_debug() {}
3930 void __init sched_init_smp(void)
3932 arch_init_sched_domains();
3933 sched_domain_debug();
3936 void __init sched_init_smp(void)
3939 #endif /* CONFIG_SMP */
3941 int in_sched_functions(unsigned long addr)
3943 /* Linker adds these: start and end of __sched functions */
3944 extern char __sched_text_start[], __sched_text_end[];
3945 return addr >= (unsigned long)__sched_text_start
3946 && addr < (unsigned long)__sched_text_end;
3949 void __init sched_init(void)
3955 /* Set up an initial dummy domain for early boot */
3956 static struct sched_domain sched_domain_init;
3957 static struct sched_group sched_group_init;
3959 memset(&sched_domain_init, 0, sizeof(struct sched_domain));
3960 sched_domain_init.span = CPU_MASK_ALL;
3961 sched_domain_init.groups = &sched_group_init;
3962 sched_domain_init.last_balance = jiffies;
3963 sched_domain_init.balance_interval = INT_MAX; /* Don't balance */
3965 memset(&sched_group_init, 0, sizeof(struct sched_group));
3966 sched_group_init.cpumask = CPU_MASK_ALL;
3967 sched_group_init.next = &sched_group_init;
3968 sched_group_init.cpu_power = SCHED_LOAD_SCALE;
3971 for (i = 0; i < NR_CPUS; i++) {
3972 prio_array_t *array;
3975 spin_lock_init(&rq->lock);
3976 rq->active = rq->arrays;
3977 rq->expired = rq->arrays + 1;
3978 rq->best_expired_prio = MAX_PRIO;
3981 rq->sd = &sched_domain_init;
3983 rq->active_balance = 0;
3985 rq->migration_thread = NULL;
3986 INIT_LIST_HEAD(&rq->migration_queue);
3988 atomic_set(&rq->nr_iowait, 0);
3990 for (j = 0; j < 2; j++) {
3991 array = rq->arrays + j;
3992 for (k = 0; k < MAX_PRIO; k++) {
3993 INIT_LIST_HEAD(array->queue + k);
3994 __clear_bit(k, array->bitmap);
3996 // delimiter for bitsearch
3997 __set_bit(MAX_PRIO, array->bitmap);
4001 * We have to do a little magic to get the first
4002 * thread right in SMP mode.
4007 set_task_cpu(current, smp_processor_id());
4008 wake_up_forked_process(current);
4011 * The boot idle thread does lazy MMU switching as well:
4013 atomic_inc(&init_mm.mm_count);
4014 enter_lazy_tlb(&init_mm, current);
4017 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
4018 void __might_sleep(char *file, int line, int atomic_depth)
4020 #if defined(in_atomic)
4021 static unsigned long prev_jiffy; /* ratelimiting */
4023 #ifndef CONFIG_PREEMPT
4026 if (((in_atomic() != atomic_depth) || irqs_disabled()) &&
4027 system_state == SYSTEM_RUNNING) {
4028 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
4030 prev_jiffy = jiffies;
4031 printk(KERN_ERR "Debug: sleeping function called from invalid"
4032 " context at %s:%d\n", file, line);
4033 printk("in_atomic():%d[expected: %d], irqs_disabled():%d\n",
4034 in_atomic(), atomic_depth, irqs_disabled());
4039 EXPORT_SYMBOL(__might_sleep);
4043 #if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT)
4045 * This could be a long-held lock. If another CPU holds it for a long time,
4046 * and that CPU is not asked to reschedule then *this* CPU will spin on the
4047 * lock for a long time, even if *this* CPU is asked to reschedule.
4049 * So what we do here, in the slow (contended) path is to spin on the lock by
4050 * hand while permitting preemption.
4052 * Called inside preempt_disable().
4054 void __sched __preempt_spin_lock(spinlock_t *lock)
4056 if (preempt_count() > 1) {
4057 _raw_spin_lock(lock);
4062 while (spin_is_locked(lock))
4065 } while (!_raw_spin_trylock(lock));
4068 EXPORT_SYMBOL(__preempt_spin_lock);
4070 void __sched __preempt_write_lock(rwlock_t *lock)
4072 if (preempt_count() > 1) {
4073 _raw_write_lock(lock);
4079 while (rwlock_is_locked(lock))
4082 } while (!_raw_write_trylock(lock));
4085 EXPORT_SYMBOL(__preempt_write_lock);
4086 #endif /* defined(CONFIG_SMP) && defined(CONFIG_PREEMPT) */