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 <asm/mmu_context.h>
29 #include <linux/interrupt.h>
30 #include <linux/completion.h>
31 #include <linux/kernel_stat.h>
32 #include <linux/security.h>
33 #include <linux/notifier.h>
34 #include <linux/profile.h>
35 #include <linux/suspend.h>
36 #include <linux/blkdev.h>
37 #include <linux/delay.h>
38 #include <linux/smp.h>
39 #include <linux/threads.h>
40 #include <linux/timer.h>
41 #include <linux/rcupdate.h>
42 #include <linux/cpu.h>
43 #include <linux/cpuset.h>
44 #include <linux/percpu.h>
45 #include <linux/kthread.h>
46 #include <linux/seq_file.h>
47 #include <linux/syscalls.h>
48 #include <linux/times.h>
49 #include <linux/acct.h>
52 #include <asm/unistd.h>
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))
73 * Some helpers for converting nanosecond timing to jiffy resolution
75 #define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ))
76 #define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ))
79 * These are the 'tuning knobs' of the scheduler:
81 * Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger),
82 * default timeslice is 100 msecs, maximum timeslice is 800 msecs.
83 * Timeslices get refilled after they expire.
85 #define MIN_TIMESLICE max(5 * HZ / 1000, 1)
86 #define DEF_TIMESLICE (100 * HZ / 1000)
87 #define ON_RUNQUEUE_WEIGHT 30
88 #define CHILD_PENALTY 95
89 #define PARENT_PENALTY 100
91 #define PRIO_BONUS_RATIO 25
92 #define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
93 #define INTERACTIVE_DELTA 2
94 #define MAX_SLEEP_AVG (DEF_TIMESLICE * MAX_BONUS)
95 #define STARVATION_LIMIT (MAX_SLEEP_AVG)
96 #define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG))
99 * If a task is 'interactive' then we reinsert it in the active
100 * array after it has expired its current timeslice. (it will not
101 * continue to run immediately, it will still roundrobin with
102 * other interactive tasks.)
104 * This part scales the interactivity limit depending on niceness.
106 * We scale it linearly, offset by the INTERACTIVE_DELTA delta.
107 * Here are a few examples of different nice levels:
109 * TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
110 * TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
111 * TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0]
112 * TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
113 * TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
115 * (the X axis represents the possible -5 ... 0 ... +5 dynamic
116 * priority range a task can explore, a value of '1' means the
117 * task is rated interactive.)
119 * Ie. nice +19 tasks can never get 'interactive' enough to be
120 * reinserted into the active array. And only heavily CPU-hog nice -20
121 * tasks will be expired. Default nice 0 tasks are somewhere between,
122 * it takes some effort for them to get interactive, but it's not
126 #define CURRENT_BONUS(p) \
127 (NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \
130 #define GRANULARITY (10 * HZ / 1000 ? : 1)
133 #define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
134 (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
137 #define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
138 (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)))
141 #define SCALE(v1,v1_max,v2_max) \
142 (v1) * (v2_max) / (v1_max)
145 (SCALE(TASK_NICE(p), 40, MAX_BONUS) + INTERACTIVE_DELTA)
147 #define TASK_INTERACTIVE(p) \
148 ((p)->prio <= (p)->static_prio - DELTA(p))
150 #define INTERACTIVE_SLEEP(p) \
151 (JIFFIES_TO_NS(MAX_SLEEP_AVG * \
152 (MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
154 #define TASK_PREEMPTS_CURR(p, rq) \
155 ((p)->prio < (rq)->curr->prio)
158 * task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
159 * to time slice values: [800ms ... 100ms ... 5ms]
161 * The higher a thread's priority, the bigger timeslices
162 * it gets during one round of execution. But even the lowest
163 * priority thread gets MIN_TIMESLICE worth of execution time.
166 #define SCALE_PRIO(x, prio) \
167 max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO/2), MIN_TIMESLICE)
169 static unsigned int task_timeslice(task_t *p)
171 if (p->static_prio < NICE_TO_PRIO(0))
172 return SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio);
174 return SCALE_PRIO(DEF_TIMESLICE, p->static_prio);
176 #define task_hot(p, now, sd) ((long long) ((now) - (p)->last_ran) \
177 < (long long) (sd)->cache_hot_time)
180 * These are the runqueue data structures:
183 #define BITMAP_SIZE ((((MAX_PRIO+1+7)/8)+sizeof(long)-1)/sizeof(long))
185 typedef struct runqueue runqueue_t;
188 unsigned int nr_active;
189 unsigned long bitmap[BITMAP_SIZE];
190 struct list_head queue[MAX_PRIO];
194 * This is the main, per-CPU runqueue data structure.
196 * Locking rule: those places that want to lock multiple runqueues
197 * (such as the load balancing or the thread migration code), lock
198 * acquire operations must be ordered by ascending &runqueue.
204 * nr_running and cpu_load should be in the same cacheline because
205 * remote CPUs use both these fields when doing load calculation.
207 unsigned long nr_running;
209 unsigned long cpu_load[3];
211 unsigned long long nr_switches;
214 * This is part of a global counter where only the total sum
215 * over all CPUs matters. A task can increase this counter on
216 * one CPU and if it got migrated afterwards it may decrease
217 * it on another CPU. Always updated under the runqueue lock:
219 unsigned long nr_uninterruptible;
221 unsigned long expired_timestamp;
222 unsigned long long timestamp_last_tick;
224 struct mm_struct *prev_mm;
225 prio_array_t *active, *expired, arrays[2];
226 int best_expired_prio;
230 struct sched_domain *sd;
232 /* For active balancing */
236 task_t *migration_thread;
237 struct list_head migration_queue;
240 #ifdef CONFIG_SCHEDSTATS
242 struct sched_info rq_sched_info;
244 /* sys_sched_yield() stats */
245 unsigned long yld_exp_empty;
246 unsigned long yld_act_empty;
247 unsigned long yld_both_empty;
248 unsigned long yld_cnt;
250 /* schedule() stats */
251 unsigned long sched_switch;
252 unsigned long sched_cnt;
253 unsigned long sched_goidle;
255 /* try_to_wake_up() stats */
256 unsigned long ttwu_cnt;
257 unsigned long ttwu_local;
261 static DEFINE_PER_CPU(struct runqueue, runqueues);
264 * The domain tree (rq->sd) is protected by RCU's quiescent state transition.
265 * See detach_destroy_domains: synchronize_sched for details.
267 * The domain tree of any CPU may only be accessed from within
268 * preempt-disabled sections.
270 #define for_each_domain(cpu, domain) \
271 for (domain = rcu_dereference(cpu_rq(cpu)->sd); domain; domain = domain->parent)
273 #define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
274 #define this_rq() (&__get_cpu_var(runqueues))
275 #define task_rq(p) cpu_rq(task_cpu(p))
276 #define cpu_curr(cpu) (cpu_rq(cpu)->curr)
278 #ifndef prepare_arch_switch
279 # define prepare_arch_switch(next) do { } while (0)
281 #ifndef finish_arch_switch
282 # define finish_arch_switch(prev) do { } while (0)
285 #ifndef __ARCH_WANT_UNLOCKED_CTXSW
286 static inline int task_running(runqueue_t *rq, task_t *p)
288 return rq->curr == p;
291 static inline void prepare_lock_switch(runqueue_t *rq, task_t *next)
295 static inline void finish_lock_switch(runqueue_t *rq, task_t *prev)
297 #ifdef CONFIG_DEBUG_SPINLOCK
298 /* this is a valid case when another task releases the spinlock */
299 rq->lock.owner = current;
301 spin_unlock_irq(&rq->lock);
304 #else /* __ARCH_WANT_UNLOCKED_CTXSW */
305 static inline int task_running(runqueue_t *rq, task_t *p)
310 return rq->curr == p;
314 static inline void prepare_lock_switch(runqueue_t *rq, task_t *next)
318 * We can optimise this out completely for !SMP, because the
319 * SMP rebalancing from interrupt is the only thing that cares
324 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
325 spin_unlock_irq(&rq->lock);
327 spin_unlock(&rq->lock);
331 static inline void finish_lock_switch(runqueue_t *rq, task_t *prev)
335 * After ->oncpu is cleared, the task can be moved to a different CPU.
336 * We must ensure this doesn't happen until the switch is completely
342 #ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
346 #endif /* __ARCH_WANT_UNLOCKED_CTXSW */
349 * task_rq_lock - lock the runqueue a given task resides on and disable
350 * interrupts. Note the ordering: we can safely lookup the task_rq without
351 * explicitly disabling preemption.
353 static inline runqueue_t *task_rq_lock(task_t *p, unsigned long *flags)
359 local_irq_save(*flags);
361 spin_lock(&rq->lock);
362 if (unlikely(rq != task_rq(p))) {
363 spin_unlock_irqrestore(&rq->lock, *flags);
364 goto repeat_lock_task;
369 static inline void task_rq_unlock(runqueue_t *rq, unsigned long *flags)
372 spin_unlock_irqrestore(&rq->lock, *flags);
375 #ifdef CONFIG_SCHEDSTATS
377 * bump this up when changing the output format or the meaning of an existing
378 * format, so that tools can adapt (or abort)
380 #define SCHEDSTAT_VERSION 12
382 static int show_schedstat(struct seq_file *seq, void *v)
386 seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
387 seq_printf(seq, "timestamp %lu\n", jiffies);
388 for_each_online_cpu(cpu) {
389 runqueue_t *rq = cpu_rq(cpu);
391 struct sched_domain *sd;
395 /* runqueue-specific stats */
397 "cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
398 cpu, rq->yld_both_empty,
399 rq->yld_act_empty, rq->yld_exp_empty, rq->yld_cnt,
400 rq->sched_switch, rq->sched_cnt, rq->sched_goidle,
401 rq->ttwu_cnt, rq->ttwu_local,
402 rq->rq_sched_info.cpu_time,
403 rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt);
405 seq_printf(seq, "\n");
408 /* domain-specific stats */
410 for_each_domain(cpu, sd) {
411 enum idle_type itype;
412 char mask_str[NR_CPUS];
414 cpumask_scnprintf(mask_str, NR_CPUS, sd->span);
415 seq_printf(seq, "domain%d %s", dcnt++, mask_str);
416 for (itype = SCHED_IDLE; itype < MAX_IDLE_TYPES;
418 seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu",
420 sd->lb_balanced[itype],
421 sd->lb_failed[itype],
422 sd->lb_imbalance[itype],
423 sd->lb_gained[itype],
424 sd->lb_hot_gained[itype],
425 sd->lb_nobusyq[itype],
426 sd->lb_nobusyg[itype]);
428 seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n",
429 sd->alb_cnt, sd->alb_failed, sd->alb_pushed,
430 sd->sbe_cnt, sd->sbe_balanced, sd->sbe_pushed,
431 sd->sbf_cnt, sd->sbf_balanced, sd->sbf_pushed,
432 sd->ttwu_wake_remote, sd->ttwu_move_affine, sd->ttwu_move_balance);
440 static int schedstat_open(struct inode *inode, struct file *file)
442 unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32);
443 char *buf = kmalloc(size, GFP_KERNEL);
449 res = single_open(file, show_schedstat, NULL);
451 m = file->private_data;
459 struct file_operations proc_schedstat_operations = {
460 .open = schedstat_open,
463 .release = single_release,
466 # define schedstat_inc(rq, field) do { (rq)->field++; } while (0)
467 # define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0)
468 #else /* !CONFIG_SCHEDSTATS */
469 # define schedstat_inc(rq, field) do { } while (0)
470 # define schedstat_add(rq, field, amt) do { } while (0)
474 * rq_lock - lock a given runqueue and disable interrupts.
476 static inline runqueue_t *this_rq_lock(void)
483 spin_lock(&rq->lock);
488 #ifdef CONFIG_SCHEDSTATS
490 * Called when a process is dequeued from the active array and given
491 * the cpu. We should note that with the exception of interactive
492 * tasks, the expired queue will become the active queue after the active
493 * queue is empty, without explicitly dequeuing and requeuing tasks in the
494 * expired queue. (Interactive tasks may be requeued directly to the
495 * active queue, thus delaying tasks in the expired queue from running;
496 * see scheduler_tick()).
498 * This function is only called from sched_info_arrive(), rather than
499 * dequeue_task(). Even though a task may be queued and dequeued multiple
500 * times as it is shuffled about, we're really interested in knowing how
501 * long it was from the *first* time it was queued to the time that it
504 static inline void sched_info_dequeued(task_t *t)
506 t->sched_info.last_queued = 0;
510 * Called when a task finally hits the cpu. We can now calculate how
511 * long it was waiting to run. We also note when it began so that we
512 * can keep stats on how long its timeslice is.
514 static inline void sched_info_arrive(task_t *t)
516 unsigned long now = jiffies, diff = 0;
517 struct runqueue *rq = task_rq(t);
519 if (t->sched_info.last_queued)
520 diff = now - t->sched_info.last_queued;
521 sched_info_dequeued(t);
522 t->sched_info.run_delay += diff;
523 t->sched_info.last_arrival = now;
524 t->sched_info.pcnt++;
529 rq->rq_sched_info.run_delay += diff;
530 rq->rq_sched_info.pcnt++;
534 * Called when a process is queued into either the active or expired
535 * array. The time is noted and later used to determine how long we
536 * had to wait for us to reach the cpu. Since the expired queue will
537 * become the active queue after active queue is empty, without dequeuing
538 * and requeuing any tasks, we are interested in queuing to either. It
539 * is unusual but not impossible for tasks to be dequeued and immediately
540 * requeued in the same or another array: this can happen in sched_yield(),
541 * set_user_nice(), and even load_balance() as it moves tasks from runqueue
544 * This function is only called from enqueue_task(), but also only updates
545 * the timestamp if it is already not set. It's assumed that
546 * sched_info_dequeued() will clear that stamp when appropriate.
548 static inline void sched_info_queued(task_t *t)
550 if (!t->sched_info.last_queued)
551 t->sched_info.last_queued = jiffies;
555 * Called when a process ceases being the active-running process, either
556 * voluntarily or involuntarily. Now we can calculate how long we ran.
558 static inline void sched_info_depart(task_t *t)
560 struct runqueue *rq = task_rq(t);
561 unsigned long diff = jiffies - t->sched_info.last_arrival;
563 t->sched_info.cpu_time += diff;
566 rq->rq_sched_info.cpu_time += diff;
570 * Called when tasks are switched involuntarily due, typically, to expiring
571 * their time slice. (This may also be called when switching to or from
572 * the idle task.) We are only called when prev != next.
574 static inline void sched_info_switch(task_t *prev, task_t *next)
576 struct runqueue *rq = task_rq(prev);
579 * prev now departs the cpu. It's not interesting to record
580 * stats about how efficient we were at scheduling the idle
583 if (prev != rq->idle)
584 sched_info_depart(prev);
586 if (next != rq->idle)
587 sched_info_arrive(next);
590 #define sched_info_queued(t) do { } while (0)
591 #define sched_info_switch(t, next) do { } while (0)
592 #endif /* CONFIG_SCHEDSTATS */
595 * Adding/removing a task to/from a priority array:
597 static void dequeue_task(struct task_struct *p, prio_array_t *array)
600 list_del(&p->run_list);
601 if (list_empty(array->queue + p->prio))
602 __clear_bit(p->prio, array->bitmap);
605 static void enqueue_task(struct task_struct *p, prio_array_t *array)
607 sched_info_queued(p);
608 list_add_tail(&p->run_list, array->queue + p->prio);
609 __set_bit(p->prio, array->bitmap);
615 * Put task to the end of the run list without the overhead of dequeue
616 * followed by enqueue.
618 static void requeue_task(struct task_struct *p, prio_array_t *array)
620 list_move_tail(&p->run_list, array->queue + p->prio);
623 static inline void enqueue_task_head(struct task_struct *p, prio_array_t *array)
625 list_add(&p->run_list, array->queue + p->prio);
626 __set_bit(p->prio, array->bitmap);
632 * effective_prio - return the priority that is based on the static
633 * priority but is modified by bonuses/penalties.
635 * We scale the actual sleep average [0 .... MAX_SLEEP_AVG]
636 * into the -5 ... 0 ... +5 bonus/penalty range.
638 * We use 25% of the full 0...39 priority range so that:
640 * 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs.
641 * 2) nice -20 CPU hogs do not get preempted by nice 0 tasks.
643 * Both properties are important to certain workloads.
645 static int effective_prio(task_t *p)
652 bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;
654 prio = p->static_prio - bonus;
655 if (prio < MAX_RT_PRIO)
657 if (prio > MAX_PRIO-1)
663 * __activate_task - move a task to the runqueue.
665 static inline void __activate_task(task_t *p, runqueue_t *rq)
667 enqueue_task(p, rq->active);
672 * __activate_idle_task - move idle task to the _front_ of runqueue.
674 static inline void __activate_idle_task(task_t *p, runqueue_t *rq)
676 enqueue_task_head(p, rq->active);
680 static int recalc_task_prio(task_t *p, unsigned long long now)
682 /* Caller must always ensure 'now >= p->timestamp' */
683 unsigned long long __sleep_time = now - p->timestamp;
684 unsigned long sleep_time;
686 if (__sleep_time > NS_MAX_SLEEP_AVG)
687 sleep_time = NS_MAX_SLEEP_AVG;
689 sleep_time = (unsigned long)__sleep_time;
691 if (likely(sleep_time > 0)) {
693 * User tasks that sleep a long time are categorised as
694 * idle and will get just interactive status to stay active &
695 * prevent them suddenly becoming cpu hogs and starving
698 if (p->mm && p->activated != -1 &&
699 sleep_time > INTERACTIVE_SLEEP(p)) {
700 p->sleep_avg = JIFFIES_TO_NS(MAX_SLEEP_AVG -
704 * The lower the sleep avg a task has the more
705 * rapidly it will rise with sleep time.
707 sleep_time *= (MAX_BONUS - CURRENT_BONUS(p)) ? : 1;
710 * Tasks waking from uninterruptible sleep are
711 * limited in their sleep_avg rise as they
712 * are likely to be waiting on I/O
714 if (p->activated == -1 && p->mm) {
715 if (p->sleep_avg >= INTERACTIVE_SLEEP(p))
717 else if (p->sleep_avg + sleep_time >=
718 INTERACTIVE_SLEEP(p)) {
719 p->sleep_avg = INTERACTIVE_SLEEP(p);
725 * This code gives a bonus to interactive tasks.
727 * The boost works by updating the 'average sleep time'
728 * value here, based on ->timestamp. The more time a
729 * task spends sleeping, the higher the average gets -
730 * and the higher the priority boost gets as well.
732 p->sleep_avg += sleep_time;
734 if (p->sleep_avg > NS_MAX_SLEEP_AVG)
735 p->sleep_avg = NS_MAX_SLEEP_AVG;
739 return effective_prio(p);
743 * activate_task - move a task to the runqueue and do priority recalculation
745 * Update all the scheduling statistics stuff. (sleep average
746 * calculation, priority modifiers, etc.)
748 static void activate_task(task_t *p, runqueue_t *rq, int local)
750 unsigned long long now;
755 /* Compensate for drifting sched_clock */
756 runqueue_t *this_rq = this_rq();
757 now = (now - this_rq->timestamp_last_tick)
758 + rq->timestamp_last_tick;
762 p->prio = recalc_task_prio(p, now);
765 * This checks to make sure it's not an uninterruptible task
766 * that is now waking up.
770 * Tasks which were woken up by interrupts (ie. hw events)
771 * are most likely of interactive nature. So we give them
772 * the credit of extending their sleep time to the period
773 * of time they spend on the runqueue, waiting for execution
774 * on a CPU, first time around:
780 * Normal first-time wakeups get a credit too for
781 * on-runqueue time, but it will be weighted down:
788 __activate_task(p, rq);
792 * deactivate_task - remove a task from the runqueue.
794 static void deactivate_task(struct task_struct *p, runqueue_t *rq)
797 dequeue_task(p, p->array);
802 * resched_task - mark a task 'to be rescheduled now'.
804 * On UP this means the setting of the need_resched flag, on SMP it
805 * might also involve a cross-CPU call to trigger the scheduler on
809 static void resched_task(task_t *p)
811 int need_resched, nrpolling;
813 assert_spin_locked(&task_rq(p)->lock);
815 /* minimise the chance of sending an interrupt to poll_idle() */
816 nrpolling = test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
817 need_resched = test_and_set_tsk_thread_flag(p,TIF_NEED_RESCHED);
818 nrpolling |= test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
820 if (!need_resched && !nrpolling && (task_cpu(p) != smp_processor_id()))
821 smp_send_reschedule(task_cpu(p));
824 static inline void resched_task(task_t *p)
826 set_tsk_need_resched(p);
831 * task_curr - is this task currently executing on a CPU?
832 * @p: the task in question.
834 inline int task_curr(const task_t *p)
836 return cpu_curr(task_cpu(p)) == p;
841 struct list_head list;
846 struct completion done;
850 * The task's runqueue lock must be held.
851 * Returns true if you have to wait for migration thread.
853 static int migrate_task(task_t *p, int dest_cpu, migration_req_t *req)
855 runqueue_t *rq = task_rq(p);
858 * If the task is not on a runqueue (and not running), then
859 * it is sufficient to simply update the task's cpu field.
861 if (!p->array && !task_running(rq, p)) {
862 set_task_cpu(p, dest_cpu);
866 init_completion(&req->done);
868 req->dest_cpu = dest_cpu;
869 list_add(&req->list, &rq->migration_queue);
874 * wait_task_inactive - wait for a thread to unschedule.
876 * The caller must ensure that the task *will* unschedule sometime soon,
877 * else this function might spin for a *long* time. This function can't
878 * be called with interrupts off, or it may introduce deadlock with
879 * smp_call_function() if an IPI is sent by the same process we are
880 * waiting to become inactive.
882 void wait_task_inactive(task_t *p)
889 rq = task_rq_lock(p, &flags);
890 /* Must be off runqueue entirely, not preempted. */
891 if (unlikely(p->array || task_running(rq, p))) {
892 /* If it's preempted, we yield. It could be a while. */
893 preempted = !task_running(rq, p);
894 task_rq_unlock(rq, &flags);
900 task_rq_unlock(rq, &flags);
904 * kick_process - kick a running thread to enter/exit the kernel
905 * @p: the to-be-kicked thread
907 * Cause a process which is running on another CPU to enter
908 * kernel-mode, without any delay. (to get signals handled.)
910 * NOTE: this function doesnt have to take the runqueue lock,
911 * because all it wants to ensure is that the remote task enters
912 * the kernel. If the IPI races and the task has been migrated
913 * to another CPU then no harm is done and the purpose has been
916 void kick_process(task_t *p)
922 if ((cpu != smp_processor_id()) && task_curr(p))
923 smp_send_reschedule(cpu);
928 * Return a low guess at the load of a migration-source cpu.
930 * We want to under-estimate the load of migration sources, to
931 * balance conservatively.
933 static inline unsigned long source_load(int cpu, int type)
935 runqueue_t *rq = cpu_rq(cpu);
936 unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;
940 return min(rq->cpu_load[type-1], load_now);
944 * Return a high guess at the load of a migration-target cpu
946 static inline unsigned long target_load(int cpu, int type)
948 runqueue_t *rq = cpu_rq(cpu);
949 unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;
953 return max(rq->cpu_load[type-1], load_now);
957 * find_idlest_group finds and returns the least busy CPU group within the
960 static struct sched_group *
961 find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
963 struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups;
964 unsigned long min_load = ULONG_MAX, this_load = 0;
965 int load_idx = sd->forkexec_idx;
966 int imbalance = 100 + (sd->imbalance_pct-100)/2;
969 unsigned long load, avg_load;
973 /* Skip over this group if it has no CPUs allowed */
974 if (!cpus_intersects(group->cpumask, p->cpus_allowed))
977 local_group = cpu_isset(this_cpu, group->cpumask);
979 /* Tally up the load of all CPUs in the group */
982 for_each_cpu_mask(i, group->cpumask) {
983 /* Bias balancing toward cpus of our domain */
985 load = source_load(i, load_idx);
987 load = target_load(i, load_idx);
992 /* Adjust by relative CPU power of the group */
993 avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
996 this_load = avg_load;
998 } else if (avg_load < min_load) {
1003 group = group->next;
1004 } while (group != sd->groups);
1006 if (!idlest || 100*this_load < imbalance*min_load)
1012 * find_idlest_queue - find the idlest runqueue among the cpus in group.
1015 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
1018 unsigned long load, min_load = ULONG_MAX;
1022 /* Traverse only the allowed CPUs */
1023 cpus_and(tmp, group->cpumask, p->cpus_allowed);
1025 for_each_cpu_mask(i, tmp) {
1026 load = source_load(i, 0);
1028 if (load < min_load || (load == min_load && i == this_cpu)) {
1038 * sched_balance_self: balance the current task (running on cpu) in domains
1039 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
1042 * Balance, ie. select the least loaded group.
1044 * Returns the target CPU number, or the same CPU if no balancing is needed.
1046 * preempt must be disabled.
1048 static int sched_balance_self(int cpu, int flag)
1050 struct task_struct *t = current;
1051 struct sched_domain *tmp, *sd = NULL;
1053 for_each_domain(cpu, tmp)
1054 if (tmp->flags & flag)
1059 struct sched_group *group;
1064 group = find_idlest_group(sd, t, cpu);
1068 new_cpu = find_idlest_cpu(group, t, cpu);
1069 if (new_cpu == -1 || new_cpu == cpu)
1072 /* Now try balancing at a lower domain level */
1076 weight = cpus_weight(span);
1077 for_each_domain(cpu, tmp) {
1078 if (weight <= cpus_weight(tmp->span))
1080 if (tmp->flags & flag)
1083 /* while loop will break here if sd == NULL */
1089 #endif /* CONFIG_SMP */
1092 * wake_idle() will wake a task on an idle cpu if task->cpu is
1093 * not idle and an idle cpu is available. The span of cpus to
1094 * search starts with cpus closest then further out as needed,
1095 * so we always favor a closer, idle cpu.
1097 * Returns the CPU we should wake onto.
1099 #if defined(ARCH_HAS_SCHED_WAKE_IDLE)
1100 static int wake_idle(int cpu, task_t *p)
1103 struct sched_domain *sd;
1109 for_each_domain(cpu, sd) {
1110 if (sd->flags & SD_WAKE_IDLE) {
1111 cpus_and(tmp, sd->span, p->cpus_allowed);
1112 for_each_cpu_mask(i, tmp) {
1123 static inline int wake_idle(int cpu, task_t *p)
1130 * try_to_wake_up - wake up a thread
1131 * @p: the to-be-woken-up thread
1132 * @state: the mask of task states that can be woken
1133 * @sync: do a synchronous wakeup?
1135 * Put it on the run-queue if it's not already there. The "current"
1136 * thread is always on the run-queue (except when the actual
1137 * re-schedule is in progress), and as such you're allowed to do
1138 * the simpler "current->state = TASK_RUNNING" to mark yourself
1139 * runnable without the overhead of this.
1141 * returns failure only if the task is already active.
1143 static int try_to_wake_up(task_t *p, unsigned int state, int sync)
1145 int cpu, this_cpu, success = 0;
1146 unsigned long flags;
1150 unsigned long load, this_load;
1151 struct sched_domain *sd, *this_sd = NULL;
1155 rq = task_rq_lock(p, &flags);
1156 old_state = p->state;
1157 if (!(old_state & state))
1164 this_cpu = smp_processor_id();
1167 if (unlikely(task_running(rq, p)))
1172 schedstat_inc(rq, ttwu_cnt);
1173 if (cpu == this_cpu) {
1174 schedstat_inc(rq, ttwu_local);
1178 for_each_domain(this_cpu, sd) {
1179 if (cpu_isset(cpu, sd->span)) {
1180 schedstat_inc(sd, ttwu_wake_remote);
1186 if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
1190 * Check for affine wakeup and passive balancing possibilities.
1193 int idx = this_sd->wake_idx;
1194 unsigned int imbalance;
1196 imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
1198 load = source_load(cpu, idx);
1199 this_load = target_load(this_cpu, idx);
1201 new_cpu = this_cpu; /* Wake to this CPU if we can */
1203 if (this_sd->flags & SD_WAKE_AFFINE) {
1204 unsigned long tl = this_load;
1206 * If sync wakeup then subtract the (maximum possible)
1207 * effect of the currently running task from the load
1208 * of the current CPU:
1211 tl -= SCHED_LOAD_SCALE;
1214 tl + target_load(cpu, idx) <= SCHED_LOAD_SCALE) ||
1215 100*(tl + SCHED_LOAD_SCALE) <= imbalance*load) {
1217 * This domain has SD_WAKE_AFFINE and
1218 * p is cache cold in this domain, and
1219 * there is no bad imbalance.
1221 schedstat_inc(this_sd, ttwu_move_affine);
1227 * Start passive balancing when half the imbalance_pct
1230 if (this_sd->flags & SD_WAKE_BALANCE) {
1231 if (imbalance*this_load <= 100*load) {
1232 schedstat_inc(this_sd, ttwu_move_balance);
1238 new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */
1240 new_cpu = wake_idle(new_cpu, p);
1241 if (new_cpu != cpu) {
1242 set_task_cpu(p, new_cpu);
1243 task_rq_unlock(rq, &flags);
1244 /* might preempt at this point */
1245 rq = task_rq_lock(p, &flags);
1246 old_state = p->state;
1247 if (!(old_state & state))
1252 this_cpu = smp_processor_id();
1257 #endif /* CONFIG_SMP */
1258 if (old_state == TASK_UNINTERRUPTIBLE) {
1259 rq->nr_uninterruptible--;
1261 * Tasks on involuntary sleep don't earn
1262 * sleep_avg beyond just interactive state.
1268 * Tasks that have marked their sleep as noninteractive get
1269 * woken up without updating their sleep average. (i.e. their
1270 * sleep is handled in a priority-neutral manner, no priority
1271 * boost and no penalty.)
1273 if (old_state & TASK_NONINTERACTIVE)
1274 __activate_task(p, rq);
1276 activate_task(p, rq, cpu == this_cpu);
1278 * Sync wakeups (i.e. those types of wakeups where the waker
1279 * has indicated that it will leave the CPU in short order)
1280 * don't trigger a preemption, if the woken up task will run on
1281 * this cpu. (in this case the 'I will reschedule' promise of
1282 * the waker guarantees that the freshly woken up task is going
1283 * to be considered on this CPU.)
1285 if (!sync || cpu != this_cpu) {
1286 if (TASK_PREEMPTS_CURR(p, rq))
1287 resched_task(rq->curr);
1292 p->state = TASK_RUNNING;
1294 task_rq_unlock(rq, &flags);
1299 int fastcall wake_up_process(task_t *p)
1301 return try_to_wake_up(p, TASK_STOPPED | TASK_TRACED |
1302 TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, 0);
1305 EXPORT_SYMBOL(wake_up_process);
1307 int fastcall wake_up_state(task_t *p, unsigned int state)
1309 return try_to_wake_up(p, state, 0);
1313 * Perform scheduler related setup for a newly forked process p.
1314 * p is forked by current.
1316 void fastcall sched_fork(task_t *p, int clone_flags)
1318 int cpu = get_cpu();
1321 cpu = sched_balance_self(cpu, SD_BALANCE_FORK);
1323 set_task_cpu(p, cpu);
1326 * We mark the process as running here, but have not actually
1327 * inserted it onto the runqueue yet. This guarantees that
1328 * nobody will actually run it, and a signal or other external
1329 * event cannot wake it up and insert it on the runqueue either.
1331 p->state = TASK_RUNNING;
1332 INIT_LIST_HEAD(&p->run_list);
1334 #ifdef CONFIG_SCHEDSTATS
1335 memset(&p->sched_info, 0, sizeof(p->sched_info));
1337 #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
1340 #ifdef CONFIG_PREEMPT
1341 /* Want to start with kernel preemption disabled. */
1342 p->thread_info->preempt_count = 1;
1345 * Share the timeslice between parent and child, thus the
1346 * total amount of pending timeslices in the system doesn't change,
1347 * resulting in more scheduling fairness.
1349 local_irq_disable();
1350 p->time_slice = (current->time_slice + 1) >> 1;
1352 * The remainder of the first timeslice might be recovered by
1353 * the parent if the child exits early enough.
1355 p->first_time_slice = 1;
1356 current->time_slice >>= 1;
1357 p->timestamp = sched_clock();
1358 if (unlikely(!current->time_slice)) {
1360 * This case is rare, it happens when the parent has only
1361 * a single jiffy left from its timeslice. Taking the
1362 * runqueue lock is not a problem.
1364 current->time_slice = 1;
1372 * wake_up_new_task - wake up a newly created task for the first time.
1374 * This function will do some initial scheduler statistics housekeeping
1375 * that must be done for every newly created context, then puts the task
1376 * on the runqueue and wakes it.
1378 void fastcall wake_up_new_task(task_t *p, unsigned long clone_flags)
1380 unsigned long flags;
1382 runqueue_t *rq, *this_rq;
1384 rq = task_rq_lock(p, &flags);
1385 BUG_ON(p->state != TASK_RUNNING);
1386 this_cpu = smp_processor_id();
1390 * We decrease the sleep average of forking parents
1391 * and children as well, to keep max-interactive tasks
1392 * from forking tasks that are max-interactive. The parent
1393 * (current) is done further down, under its lock.
1395 p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
1396 CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
1398 p->prio = effective_prio(p);
1400 if (likely(cpu == this_cpu)) {
1401 if (!(clone_flags & CLONE_VM)) {
1403 * The VM isn't cloned, so we're in a good position to
1404 * do child-runs-first in anticipation of an exec. This
1405 * usually avoids a lot of COW overhead.
1407 if (unlikely(!current->array))
1408 __activate_task(p, rq);
1410 p->prio = current->prio;
1411 list_add_tail(&p->run_list, ¤t->run_list);
1412 p->array = current->array;
1413 p->array->nr_active++;
1418 /* Run child last */
1419 __activate_task(p, rq);
1421 * We skip the following code due to cpu == this_cpu
1423 * task_rq_unlock(rq, &flags);
1424 * this_rq = task_rq_lock(current, &flags);
1428 this_rq = cpu_rq(this_cpu);
1431 * Not the local CPU - must adjust timestamp. This should
1432 * get optimised away in the !CONFIG_SMP case.
1434 p->timestamp = (p->timestamp - this_rq->timestamp_last_tick)
1435 + rq->timestamp_last_tick;
1436 __activate_task(p, rq);
1437 if (TASK_PREEMPTS_CURR(p, rq))
1438 resched_task(rq->curr);
1441 * Parent and child are on different CPUs, now get the
1442 * parent runqueue to update the parent's ->sleep_avg:
1444 task_rq_unlock(rq, &flags);
1445 this_rq = task_rq_lock(current, &flags);
1447 current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
1448 PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
1449 task_rq_unlock(this_rq, &flags);
1453 * Potentially available exiting-child timeslices are
1454 * retrieved here - this way the parent does not get
1455 * penalized for creating too many threads.
1457 * (this cannot be used to 'generate' timeslices
1458 * artificially, because any timeslice recovered here
1459 * was given away by the parent in the first place.)
1461 void fastcall sched_exit(task_t *p)
1463 unsigned long flags;
1467 * If the child was a (relative-) CPU hog then decrease
1468 * the sleep_avg of the parent as well.
1470 rq = task_rq_lock(p->parent, &flags);
1471 if (p->first_time_slice) {
1472 p->parent->time_slice += p->time_slice;
1473 if (unlikely(p->parent->time_slice > task_timeslice(p)))
1474 p->parent->time_slice = task_timeslice(p);
1476 if (p->sleep_avg < p->parent->sleep_avg)
1477 p->parent->sleep_avg = p->parent->sleep_avg /
1478 (EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
1480 task_rq_unlock(rq, &flags);
1484 * prepare_task_switch - prepare to switch tasks
1485 * @rq: the runqueue preparing to switch
1486 * @next: the task we are going to switch to.
1488 * This is called with the rq lock held and interrupts off. It must
1489 * be paired with a subsequent finish_task_switch after the context
1492 * prepare_task_switch sets up locking and calls architecture specific
1495 static inline void prepare_task_switch(runqueue_t *rq, task_t *next)
1497 prepare_lock_switch(rq, next);
1498 prepare_arch_switch(next);
1502 * finish_task_switch - clean up after a task-switch
1503 * @rq: runqueue associated with task-switch
1504 * @prev: the thread we just switched away from.
1506 * finish_task_switch must be called after the context switch, paired
1507 * with a prepare_task_switch call before the context switch.
1508 * finish_task_switch will reconcile locking set up by prepare_task_switch,
1509 * and do any other architecture-specific cleanup actions.
1511 * Note that we may have delayed dropping an mm in context_switch(). If
1512 * so, we finish that here outside of the runqueue lock. (Doing it
1513 * with the lock held can cause deadlocks; see schedule() for
1516 static inline void finish_task_switch(runqueue_t *rq, task_t *prev)
1517 __releases(rq->lock)
1519 struct mm_struct *mm = rq->prev_mm;
1520 unsigned long prev_task_flags;
1525 * A task struct has one reference for the use as "current".
1526 * If a task dies, then it sets EXIT_ZOMBIE in tsk->exit_state and
1527 * calls schedule one last time. The schedule call will never return,
1528 * and the scheduled task must drop that reference.
1529 * The test for EXIT_ZOMBIE must occur while the runqueue locks are
1530 * still held, otherwise prev could be scheduled on another cpu, die
1531 * there before we look at prev->state, and then the reference would
1533 * Manfred Spraul <manfred@colorfullife.com>
1535 prev_task_flags = prev->flags;
1536 finish_arch_switch(prev);
1537 finish_lock_switch(rq, prev);
1540 if (unlikely(prev_task_flags & PF_DEAD))
1541 put_task_struct(prev);
1545 * schedule_tail - first thing a freshly forked thread must call.
1546 * @prev: the thread we just switched away from.
1548 asmlinkage void schedule_tail(task_t *prev)
1549 __releases(rq->lock)
1551 runqueue_t *rq = this_rq();
1552 finish_task_switch(rq, prev);
1553 #ifdef __ARCH_WANT_UNLOCKED_CTXSW
1554 /* In this case, finish_task_switch does not reenable preemption */
1557 if (current->set_child_tid)
1558 put_user(current->pid, current->set_child_tid);
1562 * context_switch - switch to the new MM and the new
1563 * thread's register state.
1566 task_t * context_switch(runqueue_t *rq, task_t *prev, task_t *next)
1568 struct mm_struct *mm = next->mm;
1569 struct mm_struct *oldmm = prev->active_mm;
1571 if (unlikely(!mm)) {
1572 next->active_mm = oldmm;
1573 atomic_inc(&oldmm->mm_count);
1574 enter_lazy_tlb(oldmm, next);
1576 switch_mm(oldmm, mm, next);
1578 if (unlikely(!prev->mm)) {
1579 prev->active_mm = NULL;
1580 WARN_ON(rq->prev_mm);
1581 rq->prev_mm = oldmm;
1584 /* Here we just switch the register state and the stack. */
1585 switch_to(prev, next, prev);
1591 * nr_running, nr_uninterruptible and nr_context_switches:
1593 * externally visible scheduler statistics: current number of runnable
1594 * threads, current number of uninterruptible-sleeping threads, total
1595 * number of context switches performed since bootup.
1597 unsigned long nr_running(void)
1599 unsigned long i, sum = 0;
1601 for_each_online_cpu(i)
1602 sum += cpu_rq(i)->nr_running;
1607 unsigned long nr_uninterruptible(void)
1609 unsigned long i, sum = 0;
1612 sum += cpu_rq(i)->nr_uninterruptible;
1615 * Since we read the counters lockless, it might be slightly
1616 * inaccurate. Do not allow it to go below zero though:
1618 if (unlikely((long)sum < 0))
1624 unsigned long long nr_context_switches(void)
1626 unsigned long long i, sum = 0;
1629 sum += cpu_rq(i)->nr_switches;
1634 unsigned long nr_iowait(void)
1636 unsigned long i, sum = 0;
1639 sum += atomic_read(&cpu_rq(i)->nr_iowait);
1647 * double_rq_lock - safely lock two runqueues
1649 * Note this does not disable interrupts like task_rq_lock,
1650 * you need to do so manually before calling.
1652 static void double_rq_lock(runqueue_t *rq1, runqueue_t *rq2)
1653 __acquires(rq1->lock)
1654 __acquires(rq2->lock)
1657 spin_lock(&rq1->lock);
1658 __acquire(rq2->lock); /* Fake it out ;) */
1661 spin_lock(&rq1->lock);
1662 spin_lock(&rq2->lock);
1664 spin_lock(&rq2->lock);
1665 spin_lock(&rq1->lock);
1671 * double_rq_unlock - safely unlock two runqueues
1673 * Note this does not restore interrupts like task_rq_unlock,
1674 * you need to do so manually after calling.
1676 static void double_rq_unlock(runqueue_t *rq1, runqueue_t *rq2)
1677 __releases(rq1->lock)
1678 __releases(rq2->lock)
1680 spin_unlock(&rq1->lock);
1682 spin_unlock(&rq2->lock);
1684 __release(rq2->lock);
1688 * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
1690 static void double_lock_balance(runqueue_t *this_rq, runqueue_t *busiest)
1691 __releases(this_rq->lock)
1692 __acquires(busiest->lock)
1693 __acquires(this_rq->lock)
1695 if (unlikely(!spin_trylock(&busiest->lock))) {
1696 if (busiest < this_rq) {
1697 spin_unlock(&this_rq->lock);
1698 spin_lock(&busiest->lock);
1699 spin_lock(&this_rq->lock);
1701 spin_lock(&busiest->lock);
1706 * If dest_cpu is allowed for this process, migrate the task to it.
1707 * This is accomplished by forcing the cpu_allowed mask to only
1708 * allow dest_cpu, which will force the cpu onto dest_cpu. Then
1709 * the cpu_allowed mask is restored.
1711 static void sched_migrate_task(task_t *p, int dest_cpu)
1713 migration_req_t req;
1715 unsigned long flags;
1717 rq = task_rq_lock(p, &flags);
1718 if (!cpu_isset(dest_cpu, p->cpus_allowed)
1719 || unlikely(cpu_is_offline(dest_cpu)))
1722 /* force the process onto the specified CPU */
1723 if (migrate_task(p, dest_cpu, &req)) {
1724 /* Need to wait for migration thread (might exit: take ref). */
1725 struct task_struct *mt = rq->migration_thread;
1726 get_task_struct(mt);
1727 task_rq_unlock(rq, &flags);
1728 wake_up_process(mt);
1729 put_task_struct(mt);
1730 wait_for_completion(&req.done);
1734 task_rq_unlock(rq, &flags);
1738 * sched_exec - execve() is a valuable balancing opportunity, because at
1739 * this point the task has the smallest effective memory and cache footprint.
1741 void sched_exec(void)
1743 int new_cpu, this_cpu = get_cpu();
1744 new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC);
1746 if (new_cpu != this_cpu)
1747 sched_migrate_task(current, new_cpu);
1751 * pull_task - move a task from a remote runqueue to the local runqueue.
1752 * Both runqueues must be locked.
1755 void pull_task(runqueue_t *src_rq, prio_array_t *src_array, task_t *p,
1756 runqueue_t *this_rq, prio_array_t *this_array, int this_cpu)
1758 dequeue_task(p, src_array);
1759 src_rq->nr_running--;
1760 set_task_cpu(p, this_cpu);
1761 this_rq->nr_running++;
1762 enqueue_task(p, this_array);
1763 p->timestamp = (p->timestamp - src_rq->timestamp_last_tick)
1764 + this_rq->timestamp_last_tick;
1766 * Note that idle threads have a prio of MAX_PRIO, for this test
1767 * to be always true for them.
1769 if (TASK_PREEMPTS_CURR(p, this_rq))
1770 resched_task(this_rq->curr);
1774 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
1777 int can_migrate_task(task_t *p, runqueue_t *rq, int this_cpu,
1778 struct sched_domain *sd, enum idle_type idle,
1782 * We do not migrate tasks that are:
1783 * 1) running (obviously), or
1784 * 2) cannot be migrated to this CPU due to cpus_allowed, or
1785 * 3) are cache-hot on their current CPU.
1787 if (!cpu_isset(this_cpu, p->cpus_allowed))
1791 if (task_running(rq, p))
1795 * Aggressive migration if:
1796 * 1) task is cache cold, or
1797 * 2) too many balance attempts have failed.
1800 if (sd->nr_balance_failed > sd->cache_nice_tries)
1803 if (task_hot(p, rq->timestamp_last_tick, sd))
1809 * move_tasks tries to move up to max_nr_move tasks from busiest to this_rq,
1810 * as part of a balancing operation within "domain". Returns the number of
1813 * Called with both runqueues locked.
1815 static int move_tasks(runqueue_t *this_rq, int this_cpu, runqueue_t *busiest,
1816 unsigned long max_nr_move, struct sched_domain *sd,
1817 enum idle_type idle, int *all_pinned)
1819 prio_array_t *array, *dst_array;
1820 struct list_head *head, *curr;
1821 int idx, pulled = 0, pinned = 0;
1824 if (max_nr_move == 0)
1830 * We first consider expired tasks. Those will likely not be
1831 * executed in the near future, and they are most likely to
1832 * be cache-cold, thus switching CPUs has the least effect
1835 if (busiest->expired->nr_active) {
1836 array = busiest->expired;
1837 dst_array = this_rq->expired;
1839 array = busiest->active;
1840 dst_array = this_rq->active;
1844 /* Start searching at priority 0: */
1848 idx = sched_find_first_bit(array->bitmap);
1850 idx = find_next_bit(array->bitmap, MAX_PRIO, idx);
1851 if (idx >= MAX_PRIO) {
1852 if (array == busiest->expired && busiest->active->nr_active) {
1853 array = busiest->active;
1854 dst_array = this_rq->active;
1860 head = array->queue + idx;
1863 tmp = list_entry(curr, task_t, run_list);
1867 if (!can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) {
1874 #ifdef CONFIG_SCHEDSTATS
1875 if (task_hot(tmp, busiest->timestamp_last_tick, sd))
1876 schedstat_inc(sd, lb_hot_gained[idle]);
1879 pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu);
1882 /* We only want to steal up to the prescribed number of tasks. */
1883 if (pulled < max_nr_move) {
1891 * Right now, this is the only place pull_task() is called,
1892 * so we can safely collect pull_task() stats here rather than
1893 * inside pull_task().
1895 schedstat_add(sd, lb_gained[idle], pulled);
1898 *all_pinned = pinned;
1903 * find_busiest_group finds and returns the busiest CPU group within the
1904 * domain. It calculates and returns the number of tasks which should be
1905 * moved to restore balance via the imbalance parameter.
1907 static struct sched_group *
1908 find_busiest_group(struct sched_domain *sd, int this_cpu,
1909 unsigned long *imbalance, enum idle_type idle, int *sd_idle)
1911 struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
1912 unsigned long max_load, avg_load, total_load, this_load, total_pwr;
1913 unsigned long max_pull;
1916 max_load = this_load = total_load = total_pwr = 0;
1917 if (idle == NOT_IDLE)
1918 load_idx = sd->busy_idx;
1919 else if (idle == NEWLY_IDLE)
1920 load_idx = sd->newidle_idx;
1922 load_idx = sd->idle_idx;
1929 local_group = cpu_isset(this_cpu, group->cpumask);
1931 /* Tally up the load of all CPUs in the group */
1934 for_each_cpu_mask(i, group->cpumask) {
1935 if (*sd_idle && !idle_cpu(i))
1938 /* Bias balancing toward cpus of our domain */
1940 load = target_load(i, load_idx);
1942 load = source_load(i, load_idx);
1947 total_load += avg_load;
1948 total_pwr += group->cpu_power;
1950 /* Adjust by relative CPU power of the group */
1951 avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
1954 this_load = avg_load;
1956 } else if (avg_load > max_load) {
1957 max_load = avg_load;
1960 group = group->next;
1961 } while (group != sd->groups);
1963 if (!busiest || this_load >= max_load || max_load <= SCHED_LOAD_SCALE)
1966 avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;
1968 if (this_load >= avg_load ||
1969 100*max_load <= sd->imbalance_pct*this_load)
1973 * We're trying to get all the cpus to the average_load, so we don't
1974 * want to push ourselves above the average load, nor do we wish to
1975 * reduce the max loaded cpu below the average load, as either of these
1976 * actions would just result in more rebalancing later, and ping-pong
1977 * tasks around. Thus we look for the minimum possible imbalance.
1978 * Negative imbalances (*we* are more loaded than anyone else) will
1979 * be counted as no imbalance for these purposes -- we can't fix that
1980 * by pulling tasks to us. Be careful of negative numbers as they'll
1981 * appear as very large values with unsigned longs.
1984 /* Don't want to pull so many tasks that a group would go idle */
1985 max_pull = min(max_load - avg_load, max_load - SCHED_LOAD_SCALE);
1987 /* How much load to actually move to equalise the imbalance */
1988 *imbalance = min(max_pull * busiest->cpu_power,
1989 (avg_load - this_load) * this->cpu_power)
1992 if (*imbalance < SCHED_LOAD_SCALE) {
1993 unsigned long pwr_now = 0, pwr_move = 0;
1996 if (max_load - this_load >= SCHED_LOAD_SCALE*2) {
2002 * OK, we don't have enough imbalance to justify moving tasks,
2003 * however we may be able to increase total CPU power used by
2007 pwr_now += busiest->cpu_power*min(SCHED_LOAD_SCALE, max_load);
2008 pwr_now += this->cpu_power*min(SCHED_LOAD_SCALE, this_load);
2009 pwr_now /= SCHED_LOAD_SCALE;
2011 /* Amount of load we'd subtract */
2012 tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/busiest->cpu_power;
2014 pwr_move += busiest->cpu_power*min(SCHED_LOAD_SCALE,
2017 /* Amount of load we'd add */
2018 if (max_load*busiest->cpu_power <
2019 SCHED_LOAD_SCALE*SCHED_LOAD_SCALE)
2020 tmp = max_load*busiest->cpu_power/this->cpu_power;
2022 tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/this->cpu_power;
2023 pwr_move += this->cpu_power*min(SCHED_LOAD_SCALE, this_load + tmp);
2024 pwr_move /= SCHED_LOAD_SCALE;
2026 /* Move if we gain throughput */
2027 if (pwr_move <= pwr_now)
2034 /* Get rid of the scaling factor, rounding down as we divide */
2035 *imbalance = *imbalance / SCHED_LOAD_SCALE;
2045 * find_busiest_queue - find the busiest runqueue among the cpus in group.
2047 static runqueue_t *find_busiest_queue(struct sched_group *group)
2049 unsigned long load, max_load = 0;
2050 runqueue_t *busiest = NULL;
2053 for_each_cpu_mask(i, group->cpumask) {
2054 load = source_load(i, 0);
2056 if (load > max_load) {
2058 busiest = cpu_rq(i);
2066 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
2067 * so long as it is large enough.
2069 #define MAX_PINNED_INTERVAL 512
2072 * Check this_cpu to ensure it is balanced within domain. Attempt to move
2073 * tasks if there is an imbalance.
2075 * Called with this_rq unlocked.
2077 static int load_balance(int this_cpu, runqueue_t *this_rq,
2078 struct sched_domain *sd, enum idle_type idle)
2080 struct sched_group *group;
2081 runqueue_t *busiest;
2082 unsigned long imbalance;
2083 int nr_moved, all_pinned = 0;
2084 int active_balance = 0;
2087 if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER)
2090 schedstat_inc(sd, lb_cnt[idle]);
2092 group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle);
2094 schedstat_inc(sd, lb_nobusyg[idle]);
2098 busiest = find_busiest_queue(group);
2100 schedstat_inc(sd, lb_nobusyq[idle]);
2104 BUG_ON(busiest == this_rq);
2106 schedstat_add(sd, lb_imbalance[idle], imbalance);
2109 if (busiest->nr_running > 1) {
2111 * Attempt to move tasks. If find_busiest_group has found
2112 * an imbalance but busiest->nr_running <= 1, the group is
2113 * still unbalanced. nr_moved simply stays zero, so it is
2114 * correctly treated as an imbalance.
2116 double_rq_lock(this_rq, busiest);
2117 nr_moved = move_tasks(this_rq, this_cpu, busiest,
2118 imbalance, sd, idle, &all_pinned);
2119 double_rq_unlock(this_rq, busiest);
2121 /* All tasks on this runqueue were pinned by CPU affinity */
2122 if (unlikely(all_pinned))
2127 schedstat_inc(sd, lb_failed[idle]);
2128 sd->nr_balance_failed++;
2130 if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
2132 spin_lock(&busiest->lock);
2134 /* don't kick the migration_thread, if the curr
2135 * task on busiest cpu can't be moved to this_cpu
2137 if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) {
2138 spin_unlock(&busiest->lock);
2140 goto out_one_pinned;
2143 if (!busiest->active_balance) {
2144 busiest->active_balance = 1;
2145 busiest->push_cpu = this_cpu;
2148 spin_unlock(&busiest->lock);
2150 wake_up_process(busiest->migration_thread);
2153 * We've kicked active balancing, reset the failure
2156 sd->nr_balance_failed = sd->cache_nice_tries+1;
2159 sd->nr_balance_failed = 0;
2161 if (likely(!active_balance)) {
2162 /* We were unbalanced, so reset the balancing interval */
2163 sd->balance_interval = sd->min_interval;
2166 * If we've begun active balancing, start to back off. This
2167 * case may not be covered by the all_pinned logic if there
2168 * is only 1 task on the busy runqueue (because we don't call
2171 if (sd->balance_interval < sd->max_interval)
2172 sd->balance_interval *= 2;
2175 if (!nr_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER)
2180 schedstat_inc(sd, lb_balanced[idle]);
2182 sd->nr_balance_failed = 0;
2185 /* tune up the balancing interval */
2186 if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
2187 (sd->balance_interval < sd->max_interval))
2188 sd->balance_interval *= 2;
2190 if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
2196 * Check this_cpu to ensure it is balanced within domain. Attempt to move
2197 * tasks if there is an imbalance.
2199 * Called from schedule when this_rq is about to become idle (NEWLY_IDLE).
2200 * this_rq is locked.
2202 static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
2203 struct sched_domain *sd)
2205 struct sched_group *group;
2206 runqueue_t *busiest = NULL;
2207 unsigned long imbalance;
2211 if (sd->flags & SD_SHARE_CPUPOWER)
2214 schedstat_inc(sd, lb_cnt[NEWLY_IDLE]);
2215 group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE, &sd_idle);
2217 schedstat_inc(sd, lb_nobusyg[NEWLY_IDLE]);
2221 busiest = find_busiest_queue(group);
2223 schedstat_inc(sd, lb_nobusyq[NEWLY_IDLE]);
2227 BUG_ON(busiest == this_rq);
2229 schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance);
2232 if (busiest->nr_running > 1) {
2233 /* Attempt to move tasks */
2234 double_lock_balance(this_rq, busiest);
2235 nr_moved = move_tasks(this_rq, this_cpu, busiest,
2236 imbalance, sd, NEWLY_IDLE, NULL);
2237 spin_unlock(&busiest->lock);
2241 schedstat_inc(sd, lb_failed[NEWLY_IDLE]);
2242 if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
2245 sd->nr_balance_failed = 0;
2250 schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
2251 if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
2253 sd->nr_balance_failed = 0;
2258 * idle_balance is called by schedule() if this_cpu is about to become
2259 * idle. Attempts to pull tasks from other CPUs.
2261 static inline void idle_balance(int this_cpu, runqueue_t *this_rq)
2263 struct sched_domain *sd;
2265 for_each_domain(this_cpu, sd) {
2266 if (sd->flags & SD_BALANCE_NEWIDLE) {
2267 if (load_balance_newidle(this_cpu, this_rq, sd)) {
2268 /* We've pulled tasks over so stop searching */
2276 * active_load_balance is run by migration threads. It pushes running tasks
2277 * off the busiest CPU onto idle CPUs. It requires at least 1 task to be
2278 * running on each physical CPU where possible, and avoids physical /
2279 * logical imbalances.
2281 * Called with busiest_rq locked.
2283 static void active_load_balance(runqueue_t *busiest_rq, int busiest_cpu)
2285 struct sched_domain *sd;
2286 runqueue_t *target_rq;
2287 int target_cpu = busiest_rq->push_cpu;
2289 if (busiest_rq->nr_running <= 1)
2290 /* no task to move */
2293 target_rq = cpu_rq(target_cpu);
2296 * This condition is "impossible", if it occurs
2297 * we need to fix it. Originally reported by
2298 * Bjorn Helgaas on a 128-cpu setup.
2300 BUG_ON(busiest_rq == target_rq);
2302 /* move a task from busiest_rq to target_rq */
2303 double_lock_balance(busiest_rq, target_rq);
2305 /* Search for an sd spanning us and the target CPU. */
2306 for_each_domain(target_cpu, sd)
2307 if ((sd->flags & SD_LOAD_BALANCE) &&
2308 cpu_isset(busiest_cpu, sd->span))
2311 if (unlikely(sd == NULL))
2314 schedstat_inc(sd, alb_cnt);
2316 if (move_tasks(target_rq, target_cpu, busiest_rq, 1, sd, SCHED_IDLE, NULL))
2317 schedstat_inc(sd, alb_pushed);
2319 schedstat_inc(sd, alb_failed);
2321 spin_unlock(&target_rq->lock);
2325 * rebalance_tick will get called every timer tick, on every CPU.
2327 * It checks each scheduling domain to see if it is due to be balanced,
2328 * and initiates a balancing operation if so.
2330 * Balancing parameters are set up in arch_init_sched_domains.
2333 /* Don't have all balancing operations going off at once */
2334 #define CPU_OFFSET(cpu) (HZ * cpu / NR_CPUS)
2336 static void rebalance_tick(int this_cpu, runqueue_t *this_rq,
2337 enum idle_type idle)
2339 unsigned long old_load, this_load;
2340 unsigned long j = jiffies + CPU_OFFSET(this_cpu);
2341 struct sched_domain *sd;
2344 this_load = this_rq->nr_running * SCHED_LOAD_SCALE;
2345 /* Update our load */
2346 for (i = 0; i < 3; i++) {
2347 unsigned long new_load = this_load;
2349 old_load = this_rq->cpu_load[i];
2351 * Round up the averaging division if load is increasing. This
2352 * prevents us from getting stuck on 9 if the load is 10, for
2355 if (new_load > old_load)
2356 new_load += scale-1;
2357 this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) / scale;
2360 for_each_domain(this_cpu, sd) {
2361 unsigned long interval;
2363 if (!(sd->flags & SD_LOAD_BALANCE))
2366 interval = sd->balance_interval;
2367 if (idle != SCHED_IDLE)
2368 interval *= sd->busy_factor;
2370 /* scale ms to jiffies */
2371 interval = msecs_to_jiffies(interval);
2372 if (unlikely(!interval))
2375 if (j - sd->last_balance >= interval) {
2376 if (load_balance(this_cpu, this_rq, sd, idle)) {
2378 * We've pulled tasks over so either we're no
2379 * longer idle, or one of our SMT siblings is
2384 sd->last_balance += interval;
2390 * on UP we do not need to balance between CPUs:
2392 static inline void rebalance_tick(int cpu, runqueue_t *rq, enum idle_type idle)
2395 static inline void idle_balance(int cpu, runqueue_t *rq)
2400 static inline int wake_priority_sleeper(runqueue_t *rq)
2403 #ifdef CONFIG_SCHED_SMT
2404 spin_lock(&rq->lock);
2406 * If an SMT sibling task has been put to sleep for priority
2407 * reasons reschedule the idle task to see if it can now run.
2409 if (rq->nr_running) {
2410 resched_task(rq->idle);
2413 spin_unlock(&rq->lock);
2418 DEFINE_PER_CPU(struct kernel_stat, kstat);
2420 EXPORT_PER_CPU_SYMBOL(kstat);
2423 * This is called on clock ticks and on context switches.
2424 * Bank in p->sched_time the ns elapsed since the last tick or switch.
2426 static inline void update_cpu_clock(task_t *p, runqueue_t *rq,
2427 unsigned long long now)
2429 unsigned long long last = max(p->timestamp, rq->timestamp_last_tick);
2430 p->sched_time += now - last;
2434 * Return current->sched_time plus any more ns on the sched_clock
2435 * that have not yet been banked.
2437 unsigned long long current_sched_time(const task_t *tsk)
2439 unsigned long long ns;
2440 unsigned long flags;
2441 local_irq_save(flags);
2442 ns = max(tsk->timestamp, task_rq(tsk)->timestamp_last_tick);
2443 ns = tsk->sched_time + (sched_clock() - ns);
2444 local_irq_restore(flags);
2449 * We place interactive tasks back into the active array, if possible.
2451 * To guarantee that this does not starve expired tasks we ignore the
2452 * interactivity of a task if the first expired task had to wait more
2453 * than a 'reasonable' amount of time. This deadline timeout is
2454 * load-dependent, as the frequency of array switched decreases with
2455 * increasing number of running tasks. We also ignore the interactivity
2456 * if a better static_prio task has expired:
2458 #define EXPIRED_STARVING(rq) \
2459 ((STARVATION_LIMIT && ((rq)->expired_timestamp && \
2460 (jiffies - (rq)->expired_timestamp >= \
2461 STARVATION_LIMIT * ((rq)->nr_running) + 1))) || \
2462 ((rq)->curr->static_prio > (rq)->best_expired_prio))
2465 * Account user cpu time to a process.
2466 * @p: the process that the cpu time gets accounted to
2467 * @hardirq_offset: the offset to subtract from hardirq_count()
2468 * @cputime: the cpu time spent in user space since the last update
2470 void account_user_time(struct task_struct *p, cputime_t cputime)
2472 struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
2475 p->utime = cputime_add(p->utime, cputime);
2477 /* Add user time to cpustat. */
2478 tmp = cputime_to_cputime64(cputime);
2479 if (TASK_NICE(p) > 0)
2480 cpustat->nice = cputime64_add(cpustat->nice, tmp);
2482 cpustat->user = cputime64_add(cpustat->user, tmp);
2486 * Account system cpu time to a process.
2487 * @p: the process that the cpu time gets accounted to
2488 * @hardirq_offset: the offset to subtract from hardirq_count()
2489 * @cputime: the cpu time spent in kernel space since the last update
2491 void account_system_time(struct task_struct *p, int hardirq_offset,
2494 struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
2495 runqueue_t *rq = this_rq();
2498 p->stime = cputime_add(p->stime, cputime);
2500 /* Add system time to cpustat. */
2501 tmp = cputime_to_cputime64(cputime);
2502 if (hardirq_count() - hardirq_offset)
2503 cpustat->irq = cputime64_add(cpustat->irq, tmp);
2504 else if (softirq_count())
2505 cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
2506 else if (p != rq->idle)
2507 cpustat->system = cputime64_add(cpustat->system, tmp);
2508 else if (atomic_read(&rq->nr_iowait) > 0)
2509 cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
2511 cpustat->idle = cputime64_add(cpustat->idle, tmp);
2512 /* Account for system time used */
2513 acct_update_integrals(p);
2514 /* Update rss highwater mark */
2515 update_mem_hiwater(p);
2519 * Account for involuntary wait time.
2520 * @p: the process from which the cpu time has been stolen
2521 * @steal: the cpu time spent in involuntary wait
2523 void account_steal_time(struct task_struct *p, cputime_t steal)
2525 struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
2526 cputime64_t tmp = cputime_to_cputime64(steal);
2527 runqueue_t *rq = this_rq();
2529 if (p == rq->idle) {
2530 p->stime = cputime_add(p->stime, steal);
2531 if (atomic_read(&rq->nr_iowait) > 0)
2532 cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
2534 cpustat->idle = cputime64_add(cpustat->idle, tmp);
2536 cpustat->steal = cputime64_add(cpustat->steal, tmp);
2540 * This function gets called by the timer code, with HZ frequency.
2541 * We call it with interrupts disabled.
2543 * It also gets called by the fork code, when changing the parent's
2546 void scheduler_tick(void)
2548 int cpu = smp_processor_id();
2549 runqueue_t *rq = this_rq();
2550 task_t *p = current;
2551 unsigned long long now = sched_clock();
2553 update_cpu_clock(p, rq, now);
2555 rq->timestamp_last_tick = now;
2557 if (p == rq->idle) {
2558 if (wake_priority_sleeper(rq))
2560 rebalance_tick(cpu, rq, SCHED_IDLE);
2564 /* Task might have expired already, but not scheduled off yet */
2565 if (p->array != rq->active) {
2566 set_tsk_need_resched(p);
2569 spin_lock(&rq->lock);
2571 * The task was running during this tick - update the
2572 * time slice counter. Note: we do not update a thread's
2573 * priority until it either goes to sleep or uses up its
2574 * timeslice. This makes it possible for interactive tasks
2575 * to use up their timeslices at their highest priority levels.
2579 * RR tasks need a special form of timeslice management.
2580 * FIFO tasks have no timeslices.
2582 if ((p->policy == SCHED_RR) && !--p->time_slice) {
2583 p->time_slice = task_timeslice(p);
2584 p->first_time_slice = 0;
2585 set_tsk_need_resched(p);
2587 /* put it at the end of the queue: */
2588 requeue_task(p, rq->active);
2592 if (!--p->time_slice) {
2593 dequeue_task(p, rq->active);
2594 set_tsk_need_resched(p);
2595 p->prio = effective_prio(p);
2596 p->time_slice = task_timeslice(p);
2597 p->first_time_slice = 0;
2599 if (!rq->expired_timestamp)
2600 rq->expired_timestamp = jiffies;
2601 if (!TASK_INTERACTIVE(p) || EXPIRED_STARVING(rq)) {
2602 enqueue_task(p, rq->expired);
2603 if (p->static_prio < rq->best_expired_prio)
2604 rq->best_expired_prio = p->static_prio;
2606 enqueue_task(p, rq->active);
2609 * Prevent a too long timeslice allowing a task to monopolize
2610 * the CPU. We do this by splitting up the timeslice into
2613 * Note: this does not mean the task's timeslices expire or
2614 * get lost in any way, they just might be preempted by
2615 * another task of equal priority. (one with higher
2616 * priority would have preempted this task already.) We
2617 * requeue this task to the end of the list on this priority
2618 * level, which is in essence a round-robin of tasks with
2621 * This only applies to tasks in the interactive
2622 * delta range with at least TIMESLICE_GRANULARITY to requeue.
2624 if (TASK_INTERACTIVE(p) && !((task_timeslice(p) -
2625 p->time_slice) % TIMESLICE_GRANULARITY(p)) &&
2626 (p->time_slice >= TIMESLICE_GRANULARITY(p)) &&
2627 (p->array == rq->active)) {
2629 requeue_task(p, rq->active);
2630 set_tsk_need_resched(p);
2634 spin_unlock(&rq->lock);
2636 rebalance_tick(cpu, rq, NOT_IDLE);
2639 #ifdef CONFIG_SCHED_SMT
2640 static inline void wakeup_busy_runqueue(runqueue_t *rq)
2642 /* If an SMT runqueue is sleeping due to priority reasons wake it up */
2643 if (rq->curr == rq->idle && rq->nr_running)
2644 resched_task(rq->idle);
2647 static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
2649 struct sched_domain *tmp, *sd = NULL;
2650 cpumask_t sibling_map;
2653 for_each_domain(this_cpu, tmp)
2654 if (tmp->flags & SD_SHARE_CPUPOWER)
2661 * Unlock the current runqueue because we have to lock in
2662 * CPU order to avoid deadlocks. Caller knows that we might
2663 * unlock. We keep IRQs disabled.
2665 spin_unlock(&this_rq->lock);
2667 sibling_map = sd->span;
2669 for_each_cpu_mask(i, sibling_map)
2670 spin_lock(&cpu_rq(i)->lock);
2672 * We clear this CPU from the mask. This both simplifies the
2673 * inner loop and keps this_rq locked when we exit:
2675 cpu_clear(this_cpu, sibling_map);
2677 for_each_cpu_mask(i, sibling_map) {
2678 runqueue_t *smt_rq = cpu_rq(i);
2680 wakeup_busy_runqueue(smt_rq);
2683 for_each_cpu_mask(i, sibling_map)
2684 spin_unlock(&cpu_rq(i)->lock);
2686 * We exit with this_cpu's rq still held and IRQs
2692 * number of 'lost' timeslices this task wont be able to fully
2693 * utilize, if another task runs on a sibling. This models the
2694 * slowdown effect of other tasks running on siblings:
2696 static inline unsigned long smt_slice(task_t *p, struct sched_domain *sd)
2698 return p->time_slice * (100 - sd->per_cpu_gain) / 100;
2701 static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
2703 struct sched_domain *tmp, *sd = NULL;
2704 cpumask_t sibling_map;
2705 prio_array_t *array;
2709 for_each_domain(this_cpu, tmp)
2710 if (tmp->flags & SD_SHARE_CPUPOWER)
2717 * The same locking rules and details apply as for
2718 * wake_sleeping_dependent():
2720 spin_unlock(&this_rq->lock);
2721 sibling_map = sd->span;
2722 for_each_cpu_mask(i, sibling_map)
2723 spin_lock(&cpu_rq(i)->lock);
2724 cpu_clear(this_cpu, sibling_map);
2727 * Establish next task to be run - it might have gone away because
2728 * we released the runqueue lock above:
2730 if (!this_rq->nr_running)
2732 array = this_rq->active;
2733 if (!array->nr_active)
2734 array = this_rq->expired;
2735 BUG_ON(!array->nr_active);
2737 p = list_entry(array->queue[sched_find_first_bit(array->bitmap)].next,
2740 for_each_cpu_mask(i, sibling_map) {
2741 runqueue_t *smt_rq = cpu_rq(i);
2742 task_t *smt_curr = smt_rq->curr;
2744 /* Kernel threads do not participate in dependent sleeping */
2745 if (!p->mm || !smt_curr->mm || rt_task(p))
2746 goto check_smt_task;
2749 * If a user task with lower static priority than the
2750 * running task on the SMT sibling is trying to schedule,
2751 * delay it till there is proportionately less timeslice
2752 * left of the sibling task to prevent a lower priority
2753 * task from using an unfair proportion of the
2754 * physical cpu's resources. -ck
2756 if (rt_task(smt_curr)) {
2758 * With real time tasks we run non-rt tasks only
2759 * per_cpu_gain% of the time.
2761 if ((jiffies % DEF_TIMESLICE) >
2762 (sd->per_cpu_gain * DEF_TIMESLICE / 100))
2765 if (smt_curr->static_prio < p->static_prio &&
2766 !TASK_PREEMPTS_CURR(p, smt_rq) &&
2767 smt_slice(smt_curr, sd) > task_timeslice(p))
2771 if ((!smt_curr->mm && smt_curr != smt_rq->idle) ||
2775 wakeup_busy_runqueue(smt_rq);
2780 * Reschedule a lower priority task on the SMT sibling for
2781 * it to be put to sleep, or wake it up if it has been put to
2782 * sleep for priority reasons to see if it should run now.
2785 if ((jiffies % DEF_TIMESLICE) >
2786 (sd->per_cpu_gain * DEF_TIMESLICE / 100))
2787 resched_task(smt_curr);
2789 if (TASK_PREEMPTS_CURR(p, smt_rq) &&
2790 smt_slice(p, sd) > task_timeslice(smt_curr))
2791 resched_task(smt_curr);
2793 wakeup_busy_runqueue(smt_rq);
2797 for_each_cpu_mask(i, sibling_map)
2798 spin_unlock(&cpu_rq(i)->lock);
2802 static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
2806 static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
2812 #if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT)
2814 void fastcall add_preempt_count(int val)
2819 BUG_ON((preempt_count() < 0));
2820 preempt_count() += val;
2822 * Spinlock count overflowing soon?
2824 BUG_ON((preempt_count() & PREEMPT_MASK) >= PREEMPT_MASK-10);
2826 EXPORT_SYMBOL(add_preempt_count);
2828 void fastcall sub_preempt_count(int val)
2833 BUG_ON(val > preempt_count());
2835 * Is the spinlock portion underflowing?
2837 BUG_ON((val < PREEMPT_MASK) && !(preempt_count() & PREEMPT_MASK));
2838 preempt_count() -= val;
2840 EXPORT_SYMBOL(sub_preempt_count);
2845 * schedule() is the main scheduler function.
2847 asmlinkage void __sched schedule(void)
2850 task_t *prev, *next;
2852 prio_array_t *array;
2853 struct list_head *queue;
2854 unsigned long long now;
2855 unsigned long run_time;
2856 int cpu, idx, new_prio;
2859 * Test if we are atomic. Since do_exit() needs to call into
2860 * schedule() atomically, we ignore that path for now.
2861 * Otherwise, whine if we are scheduling when we should not be.
2863 if (likely(!current->exit_state)) {
2864 if (unlikely(in_atomic())) {
2865 printk(KERN_ERR "scheduling while atomic: "
2867 current->comm, preempt_count(), current->pid);
2871 profile_hit(SCHED_PROFILING, __builtin_return_address(0));
2876 release_kernel_lock(prev);
2877 need_resched_nonpreemptible:
2881 * The idle thread is not allowed to schedule!
2882 * Remove this check after it has been exercised a bit.
2884 if (unlikely(prev == rq->idle) && prev->state != TASK_RUNNING) {
2885 printk(KERN_ERR "bad: scheduling from the idle thread!\n");
2889 schedstat_inc(rq, sched_cnt);
2890 now = sched_clock();
2891 if (likely((long long)(now - prev->timestamp) < NS_MAX_SLEEP_AVG)) {
2892 run_time = now - prev->timestamp;
2893 if (unlikely((long long)(now - prev->timestamp) < 0))
2896 run_time = NS_MAX_SLEEP_AVG;
2899 * Tasks charged proportionately less run_time at high sleep_avg to
2900 * delay them losing their interactive status
2902 run_time /= (CURRENT_BONUS(prev) ? : 1);
2904 spin_lock_irq(&rq->lock);
2906 if (unlikely(prev->flags & PF_DEAD))
2907 prev->state = EXIT_DEAD;
2909 switch_count = &prev->nivcsw;
2910 if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
2911 switch_count = &prev->nvcsw;
2912 if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
2913 unlikely(signal_pending(prev))))
2914 prev->state = TASK_RUNNING;
2916 if (prev->state == TASK_UNINTERRUPTIBLE)
2917 rq->nr_uninterruptible++;
2918 deactivate_task(prev, rq);
2922 cpu = smp_processor_id();
2923 if (unlikely(!rq->nr_running)) {
2925 idle_balance(cpu, rq);
2926 if (!rq->nr_running) {
2928 rq->expired_timestamp = 0;
2929 wake_sleeping_dependent(cpu, rq);
2931 * wake_sleeping_dependent() might have released
2932 * the runqueue, so break out if we got new
2935 if (!rq->nr_running)
2939 if (dependent_sleeper(cpu, rq)) {
2944 * dependent_sleeper() releases and reacquires the runqueue
2945 * lock, hence go into the idle loop if the rq went
2948 if (unlikely(!rq->nr_running))
2953 if (unlikely(!array->nr_active)) {
2955 * Switch the active and expired arrays.
2957 schedstat_inc(rq, sched_switch);
2958 rq->active = rq->expired;
2959 rq->expired = array;
2961 rq->expired_timestamp = 0;
2962 rq->best_expired_prio = MAX_PRIO;
2965 idx = sched_find_first_bit(array->bitmap);
2966 queue = array->queue + idx;
2967 next = list_entry(queue->next, task_t, run_list);
2969 if (!rt_task(next) && next->activated > 0) {
2970 unsigned long long delta = now - next->timestamp;
2971 if (unlikely((long long)(now - next->timestamp) < 0))
2974 if (next->activated == 1)
2975 delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
2977 array = next->array;
2978 new_prio = recalc_task_prio(next, next->timestamp + delta);
2980 if (unlikely(next->prio != new_prio)) {
2981 dequeue_task(next, array);
2982 next->prio = new_prio;
2983 enqueue_task(next, array);
2985 requeue_task(next, array);
2987 next->activated = 0;
2989 if (next == rq->idle)
2990 schedstat_inc(rq, sched_goidle);
2992 prefetch_stack(next);
2993 clear_tsk_need_resched(prev);
2994 rcu_qsctr_inc(task_cpu(prev));
2996 update_cpu_clock(prev, rq, now);
2998 prev->sleep_avg -= run_time;
2999 if ((long)prev->sleep_avg <= 0)
3000 prev->sleep_avg = 0;
3001 prev->timestamp = prev->last_ran = now;
3003 sched_info_switch(prev, next);
3004 if (likely(prev != next)) {
3005 next->timestamp = now;
3010 prepare_task_switch(rq, next);
3011 prev = context_switch(rq, prev, next);
3014 * this_rq must be evaluated again because prev may have moved
3015 * CPUs since it called schedule(), thus the 'rq' on its stack
3016 * frame will be invalid.
3018 finish_task_switch(this_rq(), prev);
3020 spin_unlock_irq(&rq->lock);
3023 if (unlikely(reacquire_kernel_lock(prev) < 0))
3024 goto need_resched_nonpreemptible;
3025 preempt_enable_no_resched();
3026 if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
3030 EXPORT_SYMBOL(schedule);
3032 #ifdef CONFIG_PREEMPT
3034 * this is is the entry point to schedule() from in-kernel preemption
3035 * off of preempt_enable. Kernel preemptions off return from interrupt
3036 * occur there and call schedule directly.
3038 asmlinkage void __sched preempt_schedule(void)
3040 struct thread_info *ti = current_thread_info();
3041 #ifdef CONFIG_PREEMPT_BKL
3042 struct task_struct *task = current;
3043 int saved_lock_depth;
3046 * If there is a non-zero preempt_count or interrupts are disabled,
3047 * we do not want to preempt the current task. Just return..
3049 if (unlikely(ti->preempt_count || irqs_disabled()))
3053 add_preempt_count(PREEMPT_ACTIVE);
3055 * We keep the big kernel semaphore locked, but we
3056 * clear ->lock_depth so that schedule() doesnt
3057 * auto-release the semaphore:
3059 #ifdef CONFIG_PREEMPT_BKL
3060 saved_lock_depth = task->lock_depth;
3061 task->lock_depth = -1;
3064 #ifdef CONFIG_PREEMPT_BKL
3065 task->lock_depth = saved_lock_depth;
3067 sub_preempt_count(PREEMPT_ACTIVE);
3069 /* we could miss a preemption opportunity between schedule and now */
3071 if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
3075 EXPORT_SYMBOL(preempt_schedule);
3078 * this is is the entry point to schedule() from kernel preemption
3079 * off of irq context.
3080 * Note, that this is called and return with irqs disabled. This will
3081 * protect us against recursive calling from irq.
3083 asmlinkage void __sched preempt_schedule_irq(void)
3085 struct thread_info *ti = current_thread_info();
3086 #ifdef CONFIG_PREEMPT_BKL
3087 struct task_struct *task = current;
3088 int saved_lock_depth;
3090 /* Catch callers which need to be fixed*/
3091 BUG_ON(ti->preempt_count || !irqs_disabled());
3094 add_preempt_count(PREEMPT_ACTIVE);
3096 * We keep the big kernel semaphore locked, but we
3097 * clear ->lock_depth so that schedule() doesnt
3098 * auto-release the semaphore:
3100 #ifdef CONFIG_PREEMPT_BKL
3101 saved_lock_depth = task->lock_depth;
3102 task->lock_depth = -1;
3106 local_irq_disable();
3107 #ifdef CONFIG_PREEMPT_BKL
3108 task->lock_depth = saved_lock_depth;
3110 sub_preempt_count(PREEMPT_ACTIVE);
3112 /* we could miss a preemption opportunity between schedule and now */
3114 if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
3118 #endif /* CONFIG_PREEMPT */
3120 int default_wake_function(wait_queue_t *curr, unsigned mode, int sync,
3123 task_t *p = curr->private;
3124 return try_to_wake_up(p, mode, sync);
3127 EXPORT_SYMBOL(default_wake_function);
3130 * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
3131 * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
3132 * number) then we wake all the non-exclusive tasks and one exclusive task.
3134 * There are circumstances in which we can try to wake a task which has already
3135 * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
3136 * zero in this (rare) case, and we handle it by continuing to scan the queue.
3138 static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
3139 int nr_exclusive, int sync, void *key)
3141 struct list_head *tmp, *next;
3143 list_for_each_safe(tmp, next, &q->task_list) {
3146 curr = list_entry(tmp, wait_queue_t, task_list);
3147 flags = curr->flags;
3148 if (curr->func(curr, mode, sync, key) &&
3149 (flags & WQ_FLAG_EXCLUSIVE) &&
3156 * __wake_up - wake up threads blocked on a waitqueue.
3158 * @mode: which threads
3159 * @nr_exclusive: how many wake-one or wake-many threads to wake up
3160 * @key: is directly passed to the wakeup function
3162 void fastcall __wake_up(wait_queue_head_t *q, unsigned int mode,
3163 int nr_exclusive, void *key)
3165 unsigned long flags;
3167 spin_lock_irqsave(&q->lock, flags);
3168 __wake_up_common(q, mode, nr_exclusive, 0, key);
3169 spin_unlock_irqrestore(&q->lock, flags);
3172 EXPORT_SYMBOL(__wake_up);
3175 * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
3177 void fastcall __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
3179 __wake_up_common(q, mode, 1, 0, NULL);
3183 * __wake_up_sync - wake up threads blocked on a waitqueue.
3185 * @mode: which threads
3186 * @nr_exclusive: how many wake-one or wake-many threads to wake up
3188 * The sync wakeup differs that the waker knows that it will schedule
3189 * away soon, so while the target thread will be woken up, it will not
3190 * be migrated to another CPU - ie. the two threads are 'synchronized'
3191 * with each other. This can prevent needless bouncing between CPUs.
3193 * On UP it can prevent extra preemption.
3196 __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
3198 unsigned long flags;
3204 if (unlikely(!nr_exclusive))
3207 spin_lock_irqsave(&q->lock, flags);
3208 __wake_up_common(q, mode, nr_exclusive, sync, NULL);
3209 spin_unlock_irqrestore(&q->lock, flags);
3211 EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
3213 void fastcall complete(struct completion *x)
3215 unsigned long flags;
3217 spin_lock_irqsave(&x->wait.lock, flags);
3219 __wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
3221 spin_unlock_irqrestore(&x->wait.lock, flags);
3223 EXPORT_SYMBOL(complete);
3225 void fastcall complete_all(struct completion *x)
3227 unsigned long flags;
3229 spin_lock_irqsave(&x->wait.lock, flags);
3230 x->done += UINT_MAX/2;
3231 __wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
3233 spin_unlock_irqrestore(&x->wait.lock, flags);
3235 EXPORT_SYMBOL(complete_all);
3237 void fastcall __sched wait_for_completion(struct completion *x)
3240 spin_lock_irq(&x->wait.lock);
3242 DECLARE_WAITQUEUE(wait, current);
3244 wait.flags |= WQ_FLAG_EXCLUSIVE;
3245 __add_wait_queue_tail(&x->wait, &wait);
3247 __set_current_state(TASK_UNINTERRUPTIBLE);
3248 spin_unlock_irq(&x->wait.lock);
3250 spin_lock_irq(&x->wait.lock);
3252 __remove_wait_queue(&x->wait, &wait);
3255 spin_unlock_irq(&x->wait.lock);
3257 EXPORT_SYMBOL(wait_for_completion);
3259 unsigned long fastcall __sched
3260 wait_for_completion_timeout(struct completion *x, unsigned long timeout)
3264 spin_lock_irq(&x->wait.lock);
3266 DECLARE_WAITQUEUE(wait, current);
3268 wait.flags |= WQ_FLAG_EXCLUSIVE;
3269 __add_wait_queue_tail(&x->wait, &wait);
3271 __set_current_state(TASK_UNINTERRUPTIBLE);
3272 spin_unlock_irq(&x->wait.lock);
3273 timeout = schedule_timeout(timeout);
3274 spin_lock_irq(&x->wait.lock);
3276 __remove_wait_queue(&x->wait, &wait);
3280 __remove_wait_queue(&x->wait, &wait);
3284 spin_unlock_irq(&x->wait.lock);
3287 EXPORT_SYMBOL(wait_for_completion_timeout);
3289 int fastcall __sched wait_for_completion_interruptible(struct completion *x)
3295 spin_lock_irq(&x->wait.lock);
3297 DECLARE_WAITQUEUE(wait, current);
3299 wait.flags |= WQ_FLAG_EXCLUSIVE;
3300 __add_wait_queue_tail(&x->wait, &wait);
3302 if (signal_pending(current)) {
3304 __remove_wait_queue(&x->wait, &wait);
3307 __set_current_state(TASK_INTERRUPTIBLE);
3308 spin_unlock_irq(&x->wait.lock);
3310 spin_lock_irq(&x->wait.lock);
3312 __remove_wait_queue(&x->wait, &wait);
3316 spin_unlock_irq(&x->wait.lock);
3320 EXPORT_SYMBOL(wait_for_completion_interruptible);
3322 unsigned long fastcall __sched
3323 wait_for_completion_interruptible_timeout(struct completion *x,
3324 unsigned long timeout)
3328 spin_lock_irq(&x->wait.lock);
3330 DECLARE_WAITQUEUE(wait, current);
3332 wait.flags |= WQ_FLAG_EXCLUSIVE;
3333 __add_wait_queue_tail(&x->wait, &wait);
3335 if (signal_pending(current)) {
3336 timeout = -ERESTARTSYS;
3337 __remove_wait_queue(&x->wait, &wait);
3340 __set_current_state(TASK_INTERRUPTIBLE);
3341 spin_unlock_irq(&x->wait.lock);
3342 timeout = schedule_timeout(timeout);
3343 spin_lock_irq(&x->wait.lock);
3345 __remove_wait_queue(&x->wait, &wait);
3349 __remove_wait_queue(&x->wait, &wait);
3353 spin_unlock_irq(&x->wait.lock);
3356 EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
3359 #define SLEEP_ON_VAR \
3360 unsigned long flags; \
3361 wait_queue_t wait; \
3362 init_waitqueue_entry(&wait, current);
3364 #define SLEEP_ON_HEAD \
3365 spin_lock_irqsave(&q->lock,flags); \
3366 __add_wait_queue(q, &wait); \
3367 spin_unlock(&q->lock);
3369 #define SLEEP_ON_TAIL \
3370 spin_lock_irq(&q->lock); \
3371 __remove_wait_queue(q, &wait); \
3372 spin_unlock_irqrestore(&q->lock, flags);
3374 void fastcall __sched interruptible_sleep_on(wait_queue_head_t *q)
3378 current->state = TASK_INTERRUPTIBLE;
3385 EXPORT_SYMBOL(interruptible_sleep_on);
3387 long fastcall __sched
3388 interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
3392 current->state = TASK_INTERRUPTIBLE;
3395 timeout = schedule_timeout(timeout);
3401 EXPORT_SYMBOL(interruptible_sleep_on_timeout);
3403 void fastcall __sched sleep_on(wait_queue_head_t *q)
3407 current->state = TASK_UNINTERRUPTIBLE;
3414 EXPORT_SYMBOL(sleep_on);
3416 long fastcall __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
3420 current->state = TASK_UNINTERRUPTIBLE;
3423 timeout = schedule_timeout(timeout);
3429 EXPORT_SYMBOL(sleep_on_timeout);
3431 void set_user_nice(task_t *p, long nice)
3433 unsigned long flags;
3434 prio_array_t *array;
3436 int old_prio, new_prio, delta;
3438 if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
3441 * We have to be careful, if called from sys_setpriority(),
3442 * the task might be in the middle of scheduling on another CPU.
3444 rq = task_rq_lock(p, &flags);
3446 * The RT priorities are set via sched_setscheduler(), but we still
3447 * allow the 'normal' nice value to be set - but as expected
3448 * it wont have any effect on scheduling until the task is
3452 p->static_prio = NICE_TO_PRIO(nice);
3457 dequeue_task(p, array);
3460 new_prio = NICE_TO_PRIO(nice);
3461 delta = new_prio - old_prio;
3462 p->static_prio = NICE_TO_PRIO(nice);
3466 enqueue_task(p, array);
3468 * If the task increased its priority or is running and
3469 * lowered its priority, then reschedule its CPU:
3471 if (delta < 0 || (delta > 0 && task_running(rq, p)))
3472 resched_task(rq->curr);
3475 task_rq_unlock(rq, &flags);
3478 EXPORT_SYMBOL(set_user_nice);
3481 * can_nice - check if a task can reduce its nice value
3485 int can_nice(const task_t *p, const int nice)
3487 /* convert nice value [19,-20] to rlimit style value [1,40] */
3488 int nice_rlim = 20 - nice;
3489 return (nice_rlim <= p->signal->rlim[RLIMIT_NICE].rlim_cur ||
3490 capable(CAP_SYS_NICE));
3493 #ifdef __ARCH_WANT_SYS_NICE
3496 * sys_nice - change the priority of the current process.
3497 * @increment: priority increment
3499 * sys_setpriority is a more generic, but much slower function that
3500 * does similar things.
3502 asmlinkage long sys_nice(int increment)
3508 * Setpriority might change our priority at the same moment.
3509 * We don't have to worry. Conceptually one call occurs first
3510 * and we have a single winner.
3512 if (increment < -40)
3517 nice = PRIO_TO_NICE(current->static_prio) + increment;
3523 if (increment < 0 && !can_nice(current, nice))
3526 retval = security_task_setnice(current, nice);
3530 set_user_nice(current, nice);
3537 * task_prio - return the priority value of a given task.
3538 * @p: the task in question.
3540 * This is the priority value as seen by users in /proc.
3541 * RT tasks are offset by -200. Normal tasks are centered
3542 * around 0, value goes from -16 to +15.
3544 int task_prio(const task_t *p)
3546 return p->prio - MAX_RT_PRIO;
3550 * task_nice - return the nice value of a given task.
3551 * @p: the task in question.
3553 int task_nice(const task_t *p)
3555 return TASK_NICE(p);
3557 EXPORT_SYMBOL_GPL(task_nice);
3560 * idle_cpu - is a given cpu idle currently?
3561 * @cpu: the processor in question.
3563 int idle_cpu(int cpu)
3565 return cpu_curr(cpu) == cpu_rq(cpu)->idle;
3568 EXPORT_SYMBOL_GPL(idle_cpu);
3571 * idle_task - return the idle task for a given cpu.
3572 * @cpu: the processor in question.
3574 task_t *idle_task(int cpu)
3576 return cpu_rq(cpu)->idle;
3580 * find_process_by_pid - find a process with a matching PID value.
3581 * @pid: the pid in question.
3583 static inline task_t *find_process_by_pid(pid_t pid)
3585 return pid ? find_task_by_pid(pid) : current;
3588 /* Actually do priority change: must hold rq lock. */
3589 static void __setscheduler(struct task_struct *p, int policy, int prio)
3593 p->rt_priority = prio;
3594 if (policy != SCHED_NORMAL)
3595 p->prio = MAX_RT_PRIO-1 - p->rt_priority;
3597 p->prio = p->static_prio;
3601 * sched_setscheduler - change the scheduling policy and/or RT priority of
3603 * @p: the task in question.
3604 * @policy: new policy.
3605 * @param: structure containing the new RT priority.
3607 int sched_setscheduler(struct task_struct *p, int policy,
3608 struct sched_param *param)
3611 int oldprio, oldpolicy = -1;
3612 prio_array_t *array;
3613 unsigned long flags;
3617 /* double check policy once rq lock held */
3619 policy = oldpolicy = p->policy;
3620 else if (policy != SCHED_FIFO && policy != SCHED_RR &&
3621 policy != SCHED_NORMAL)
3624 * Valid priorities for SCHED_FIFO and SCHED_RR are
3625 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL is 0.
3627 if (param->sched_priority < 0 ||
3628 (p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) ||
3629 (!p->mm && param->sched_priority > MAX_RT_PRIO-1))
3631 if ((policy == SCHED_NORMAL) != (param->sched_priority == 0))
3635 * Allow unprivileged RT tasks to decrease priority:
3637 if (!capable(CAP_SYS_NICE)) {
3638 /* can't change policy */
3639 if (policy != p->policy &&
3640 !p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
3642 /* can't increase priority */
3643 if (policy != SCHED_NORMAL &&
3644 param->sched_priority > p->rt_priority &&
3645 param->sched_priority >
3646 p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
3648 /* can't change other user's priorities */
3649 if ((current->euid != p->euid) &&
3650 (current->euid != p->uid))
3654 retval = security_task_setscheduler(p, policy, param);
3658 * To be able to change p->policy safely, the apropriate
3659 * runqueue lock must be held.
3661 rq = task_rq_lock(p, &flags);
3662 /* recheck policy now with rq lock held */
3663 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
3664 policy = oldpolicy = -1;
3665 task_rq_unlock(rq, &flags);
3670 deactivate_task(p, rq);
3672 __setscheduler(p, policy, param->sched_priority);
3674 __activate_task(p, rq);
3676 * Reschedule if we are currently running on this runqueue and
3677 * our priority decreased, or if we are not currently running on
3678 * this runqueue and our priority is higher than the current's
3680 if (task_running(rq, p)) {
3681 if (p->prio > oldprio)
3682 resched_task(rq->curr);
3683 } else if (TASK_PREEMPTS_CURR(p, rq))
3684 resched_task(rq->curr);
3686 task_rq_unlock(rq, &flags);
3689 EXPORT_SYMBOL_GPL(sched_setscheduler);
3692 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
3695 struct sched_param lparam;
3696 struct task_struct *p;
3698 if (!param || pid < 0)
3700 if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
3702 read_lock_irq(&tasklist_lock);
3703 p = find_process_by_pid(pid);
3705 read_unlock_irq(&tasklist_lock);
3708 retval = sched_setscheduler(p, policy, &lparam);
3709 read_unlock_irq(&tasklist_lock);
3714 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
3715 * @pid: the pid in question.
3716 * @policy: new policy.
3717 * @param: structure containing the new RT priority.
3719 asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
3720 struct sched_param __user *param)
3722 return do_sched_setscheduler(pid, policy, param);
3726 * sys_sched_setparam - set/change the RT priority of a thread
3727 * @pid: the pid in question.
3728 * @param: structure containing the new RT priority.
3730 asmlinkage long sys_sched_setparam(pid_t pid, struct sched_param __user *param)
3732 return do_sched_setscheduler(pid, -1, param);
3736 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
3737 * @pid: the pid in question.
3739 asmlinkage long sys_sched_getscheduler(pid_t pid)
3741 int retval = -EINVAL;
3748 read_lock(&tasklist_lock);
3749 p = find_process_by_pid(pid);
3751 retval = security_task_getscheduler(p);
3755 read_unlock(&tasklist_lock);
3762 * sys_sched_getscheduler - get the RT priority of a thread
3763 * @pid: the pid in question.
3764 * @param: structure containing the RT priority.
3766 asmlinkage long sys_sched_getparam(pid_t pid, struct sched_param __user *param)
3768 struct sched_param lp;
3769 int retval = -EINVAL;
3772 if (!param || pid < 0)
3775 read_lock(&tasklist_lock);
3776 p = find_process_by_pid(pid);
3781 retval = security_task_getscheduler(p);
3785 lp.sched_priority = p->rt_priority;
3786 read_unlock(&tasklist_lock);
3789 * This one might sleep, we cannot do it with a spinlock held ...
3791 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
3797 read_unlock(&tasklist_lock);
3801 long sched_setaffinity(pid_t pid, cpumask_t new_mask)
3805 cpumask_t cpus_allowed;
3808 read_lock(&tasklist_lock);
3810 p = find_process_by_pid(pid);
3812 read_unlock(&tasklist_lock);
3813 unlock_cpu_hotplug();
3818 * It is not safe to call set_cpus_allowed with the
3819 * tasklist_lock held. We will bump the task_struct's
3820 * usage count and then drop tasklist_lock.
3823 read_unlock(&tasklist_lock);
3826 if ((current->euid != p->euid) && (current->euid != p->uid) &&
3827 !capable(CAP_SYS_NICE))
3830 cpus_allowed = cpuset_cpus_allowed(p);
3831 cpus_and(new_mask, new_mask, cpus_allowed);
3832 retval = set_cpus_allowed(p, new_mask);
3836 unlock_cpu_hotplug();
3840 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
3841 cpumask_t *new_mask)
3843 if (len < sizeof(cpumask_t)) {
3844 memset(new_mask, 0, sizeof(cpumask_t));
3845 } else if (len > sizeof(cpumask_t)) {
3846 len = sizeof(cpumask_t);
3848 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
3852 * sys_sched_setaffinity - set the cpu affinity of a process
3853 * @pid: pid of the process
3854 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
3855 * @user_mask_ptr: user-space pointer to the new cpu mask
3857 asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
3858 unsigned long __user *user_mask_ptr)
3863 retval = get_user_cpu_mask(user_mask_ptr, len, &new_mask);
3867 return sched_setaffinity(pid, new_mask);
3871 * Represents all cpu's present in the system
3872 * In systems capable of hotplug, this map could dynamically grow
3873 * as new cpu's are detected in the system via any platform specific
3874 * method, such as ACPI for e.g.
3877 cpumask_t cpu_present_map;
3878 EXPORT_SYMBOL(cpu_present_map);
3881 cpumask_t cpu_online_map = CPU_MASK_ALL;
3882 EXPORT_SYMBOL_GPL(cpu_online_map);
3883 cpumask_t cpu_possible_map = CPU_MASK_ALL;
3886 long sched_getaffinity(pid_t pid, cpumask_t *mask)
3892 read_lock(&tasklist_lock);
3895 p = find_process_by_pid(pid);
3900 cpus_and(*mask, p->cpus_allowed, cpu_possible_map);
3903 read_unlock(&tasklist_lock);
3904 unlock_cpu_hotplug();
3912 * sys_sched_getaffinity - get the cpu affinity of a process
3913 * @pid: pid of the process
3914 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
3915 * @user_mask_ptr: user-space pointer to hold the current cpu mask
3917 asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
3918 unsigned long __user *user_mask_ptr)
3923 if (len < sizeof(cpumask_t))
3926 ret = sched_getaffinity(pid, &mask);
3930 if (copy_to_user(user_mask_ptr, &mask, sizeof(cpumask_t)))
3933 return sizeof(cpumask_t);
3937 * sys_sched_yield - yield the current processor to other threads.
3939 * this function yields the current CPU by moving the calling thread
3940 * to the expired array. If there are no other threads running on this
3941 * CPU then this function will return.
3943 asmlinkage long sys_sched_yield(void)
3945 runqueue_t *rq = this_rq_lock();
3946 prio_array_t *array = current->array;
3947 prio_array_t *target = rq->expired;
3949 schedstat_inc(rq, yld_cnt);
3951 * We implement yielding by moving the task into the expired
3954 * (special rule: RT tasks will just roundrobin in the active
3957 if (rt_task(current))
3958 target = rq->active;
3960 if (array->nr_active == 1) {
3961 schedstat_inc(rq, yld_act_empty);
3962 if (!rq->expired->nr_active)
3963 schedstat_inc(rq, yld_both_empty);
3964 } else if (!rq->expired->nr_active)
3965 schedstat_inc(rq, yld_exp_empty);
3967 if (array != target) {
3968 dequeue_task(current, array);
3969 enqueue_task(current, target);
3972 * requeue_task is cheaper so perform that if possible.
3974 requeue_task(current, array);
3977 * Since we are going to call schedule() anyway, there's
3978 * no need to preempt or enable interrupts:
3980 __release(rq->lock);
3981 _raw_spin_unlock(&rq->lock);
3982 preempt_enable_no_resched();
3989 static inline void __cond_resched(void)
3992 * The BKS might be reacquired before we have dropped
3993 * PREEMPT_ACTIVE, which could trigger a second
3994 * cond_resched() call.
3996 if (unlikely(preempt_count()))
3999 add_preempt_count(PREEMPT_ACTIVE);
4001 sub_preempt_count(PREEMPT_ACTIVE);
4002 } while (need_resched());
4005 int __sched cond_resched(void)
4007 if (need_resched()) {
4014 EXPORT_SYMBOL(cond_resched);
4017 * cond_resched_lock() - if a reschedule is pending, drop the given lock,
4018 * call schedule, and on return reacquire the lock.
4020 * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
4021 * operations here to prevent schedule() from being called twice (once via
4022 * spin_unlock(), once by hand).
4024 int cond_resched_lock(spinlock_t *lock)
4028 if (need_lockbreak(lock)) {
4034 if (need_resched()) {
4035 _raw_spin_unlock(lock);
4036 preempt_enable_no_resched();
4044 EXPORT_SYMBOL(cond_resched_lock);
4046 int __sched cond_resched_softirq(void)
4048 BUG_ON(!in_softirq());
4050 if (need_resched()) {
4051 __local_bh_enable();
4059 EXPORT_SYMBOL(cond_resched_softirq);
4063 * yield - yield the current processor to other threads.
4065 * this is a shortcut for kernel-space yielding - it marks the
4066 * thread runnable and calls sys_sched_yield().
4068 void __sched yield(void)
4070 set_current_state(TASK_RUNNING);
4074 EXPORT_SYMBOL(yield);
4077 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
4078 * that process accounting knows that this is a task in IO wait state.
4080 * But don't do that if it is a deliberate, throttling IO wait (this task
4081 * has set its backing_dev_info: the queue against which it should throttle)
4083 void __sched io_schedule(void)
4085 struct runqueue *rq = &per_cpu(runqueues, raw_smp_processor_id());
4087 atomic_inc(&rq->nr_iowait);
4089 atomic_dec(&rq->nr_iowait);
4092 EXPORT_SYMBOL(io_schedule);
4094 long __sched io_schedule_timeout(long timeout)
4096 struct runqueue *rq = &per_cpu(runqueues, raw_smp_processor_id());
4099 atomic_inc(&rq->nr_iowait);
4100 ret = schedule_timeout(timeout);
4101 atomic_dec(&rq->nr_iowait);
4106 * sys_sched_get_priority_max - return maximum RT priority.
4107 * @policy: scheduling class.
4109 * this syscall returns the maximum rt_priority that can be used
4110 * by a given scheduling class.
4112 asmlinkage long sys_sched_get_priority_max(int policy)
4119 ret = MAX_USER_RT_PRIO-1;
4129 * sys_sched_get_priority_min - return minimum RT priority.
4130 * @policy: scheduling class.
4132 * this syscall returns the minimum rt_priority that can be used
4133 * by a given scheduling class.
4135 asmlinkage long sys_sched_get_priority_min(int policy)
4151 * sys_sched_rr_get_interval - return the default timeslice of a process.
4152 * @pid: pid of the process.
4153 * @interval: userspace pointer to the timeslice value.
4155 * this syscall writes the default timeslice value of a given process
4156 * into the user-space timespec buffer. A value of '0' means infinity.
4159 long sys_sched_rr_get_interval(pid_t pid, struct timespec __user *interval)
4161 int retval = -EINVAL;
4169 read_lock(&tasklist_lock);
4170 p = find_process_by_pid(pid);
4174 retval = security_task_getscheduler(p);
4178 jiffies_to_timespec(p->policy & SCHED_FIFO ?
4179 0 : task_timeslice(p), &t);
4180 read_unlock(&tasklist_lock);
4181 retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
4185 read_unlock(&tasklist_lock);
4189 static inline struct task_struct *eldest_child(struct task_struct *p)
4191 if (list_empty(&p->children)) return NULL;
4192 return list_entry(p->children.next,struct task_struct,sibling);
4195 static inline struct task_struct *older_sibling(struct task_struct *p)
4197 if (p->sibling.prev==&p->parent->children) return NULL;
4198 return list_entry(p->sibling.prev,struct task_struct,sibling);
4201 static inline struct task_struct *younger_sibling(struct task_struct *p)
4203 if (p->sibling.next==&p->parent->children) return NULL;
4204 return list_entry(p->sibling.next,struct task_struct,sibling);
4207 static void show_task(task_t *p)
4211 unsigned long free = 0;
4212 static const char *stat_nam[] = { "R", "S", "D", "T", "t", "Z", "X" };
4214 printk("%-13.13s ", p->comm);
4215 state = p->state ? __ffs(p->state) + 1 : 0;
4216 if (state < ARRAY_SIZE(stat_nam))
4217 printk(stat_nam[state]);
4220 #if (BITS_PER_LONG == 32)
4221 if (state == TASK_RUNNING)
4222 printk(" running ");
4224 printk(" %08lX ", thread_saved_pc(p));
4226 if (state == TASK_RUNNING)
4227 printk(" running task ");
4229 printk(" %016lx ", thread_saved_pc(p));
4231 #ifdef CONFIG_DEBUG_STACK_USAGE
4233 unsigned long *n = (unsigned long *) (p->thread_info+1);
4236 free = (unsigned long) n - (unsigned long)(p->thread_info+1);
4239 printk("%5lu %5d %6d ", free, p->pid, p->parent->pid);
4240 if ((relative = eldest_child(p)))
4241 printk("%5d ", relative->pid);
4244 if ((relative = younger_sibling(p)))
4245 printk("%7d", relative->pid);
4248 if ((relative = older_sibling(p)))
4249 printk(" %5d", relative->pid);
4253 printk(" (L-TLB)\n");
4255 printk(" (NOTLB)\n");
4257 if (state != TASK_RUNNING)
4258 show_stack(p, NULL);
4261 void show_state(void)
4265 #if (BITS_PER_LONG == 32)
4268 printk(" task PC pid father child younger older\n");
4272 printk(" task PC pid father child younger older\n");
4274 read_lock(&tasklist_lock);
4275 do_each_thread(g, p) {
4277 * reset the NMI-timeout, listing all files on a slow
4278 * console might take alot of time:
4280 touch_nmi_watchdog();
4282 } while_each_thread(g, p);
4284 read_unlock(&tasklist_lock);
4288 * init_idle - set up an idle thread for a given CPU
4289 * @idle: task in question
4290 * @cpu: cpu the idle task belongs to
4292 * NOTE: this function does not set the idle thread's NEED_RESCHED
4293 * flag, to make booting more robust.
4295 void __devinit init_idle(task_t *idle, int cpu)
4297 runqueue_t *rq = cpu_rq(cpu);
4298 unsigned long flags;
4300 idle->sleep_avg = 0;
4302 idle->prio = MAX_PRIO;
4303 idle->state = TASK_RUNNING;
4304 idle->cpus_allowed = cpumask_of_cpu(cpu);
4305 set_task_cpu(idle, cpu);
4307 spin_lock_irqsave(&rq->lock, flags);
4308 rq->curr = rq->idle = idle;
4309 #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
4312 spin_unlock_irqrestore(&rq->lock, flags);
4314 /* Set the preempt count _outside_ the spinlocks! */
4315 #if defined(CONFIG_PREEMPT) && !defined(CONFIG_PREEMPT_BKL)
4316 idle->thread_info->preempt_count = (idle->lock_depth >= 0);
4318 idle->thread_info->preempt_count = 0;
4323 * In a system that switches off the HZ timer nohz_cpu_mask
4324 * indicates which cpus entered this state. This is used
4325 * in the rcu update to wait only for active cpus. For system
4326 * which do not switch off the HZ timer nohz_cpu_mask should
4327 * always be CPU_MASK_NONE.
4329 cpumask_t nohz_cpu_mask = CPU_MASK_NONE;
4333 * This is how migration works:
4335 * 1) we queue a migration_req_t structure in the source CPU's
4336 * runqueue and wake up that CPU's migration thread.
4337 * 2) we down() the locked semaphore => thread blocks.
4338 * 3) migration thread wakes up (implicitly it forces the migrated
4339 * thread off the CPU)
4340 * 4) it gets the migration request and checks whether the migrated
4341 * task is still in the wrong runqueue.
4342 * 5) if it's in the wrong runqueue then the migration thread removes
4343 * it and puts it into the right queue.
4344 * 6) migration thread up()s the semaphore.
4345 * 7) we wake up and the migration is done.
4349 * Change a given task's CPU affinity. Migrate the thread to a
4350 * proper CPU and schedule it away if the CPU it's executing on
4351 * is removed from the allowed bitmask.
4353 * NOTE: the caller must have a valid reference to the task, the
4354 * task must not exit() & deallocate itself prematurely. The
4355 * call is not atomic; no spinlocks may be held.
4357 int set_cpus_allowed(task_t *p, cpumask_t new_mask)
4359 unsigned long flags;
4361 migration_req_t req;
4364 rq = task_rq_lock(p, &flags);
4365 if (!cpus_intersects(new_mask, cpu_online_map)) {
4370 p->cpus_allowed = new_mask;
4371 /* Can the task run on the task's current CPU? If so, we're done */
4372 if (cpu_isset(task_cpu(p), new_mask))
4375 if (migrate_task(p, any_online_cpu(new_mask), &req)) {
4376 /* Need help from migration thread: drop lock and wait. */
4377 task_rq_unlock(rq, &flags);
4378 wake_up_process(rq->migration_thread);
4379 wait_for_completion(&req.done);
4380 tlb_migrate_finish(p->mm);
4384 task_rq_unlock(rq, &flags);
4388 EXPORT_SYMBOL_GPL(set_cpus_allowed);
4391 * Move (not current) task off this cpu, onto dest cpu. We're doing
4392 * this because either it can't run here any more (set_cpus_allowed()
4393 * away from this CPU, or CPU going down), or because we're
4394 * attempting to rebalance this task on exec (sched_exec).
4396 * So we race with normal scheduler movements, but that's OK, as long
4397 * as the task is no longer on this CPU.
4399 static void __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
4401 runqueue_t *rq_dest, *rq_src;
4403 if (unlikely(cpu_is_offline(dest_cpu)))
4406 rq_src = cpu_rq(src_cpu);
4407 rq_dest = cpu_rq(dest_cpu);
4409 double_rq_lock(rq_src, rq_dest);
4410 /* Already moved. */
4411 if (task_cpu(p) != src_cpu)
4413 /* Affinity changed (again). */
4414 if (!cpu_isset(dest_cpu, p->cpus_allowed))
4417 set_task_cpu(p, dest_cpu);
4420 * Sync timestamp with rq_dest's before activating.
4421 * The same thing could be achieved by doing this step
4422 * afterwards, and pretending it was a local activate.
4423 * This way is cleaner and logically correct.
4425 p->timestamp = p->timestamp - rq_src->timestamp_last_tick
4426 + rq_dest->timestamp_last_tick;
4427 deactivate_task(p, rq_src);
4428 activate_task(p, rq_dest, 0);
4429 if (TASK_PREEMPTS_CURR(p, rq_dest))
4430 resched_task(rq_dest->curr);
4434 double_rq_unlock(rq_src, rq_dest);
4438 * migration_thread - this is a highprio system thread that performs
4439 * thread migration by bumping thread off CPU then 'pushing' onto
4442 static int migration_thread(void *data)
4445 int cpu = (long)data;
4448 BUG_ON(rq->migration_thread != current);
4450 set_current_state(TASK_INTERRUPTIBLE);
4451 while (!kthread_should_stop()) {
4452 struct list_head *head;
4453 migration_req_t *req;
4457 spin_lock_irq(&rq->lock);
4459 if (cpu_is_offline(cpu)) {
4460 spin_unlock_irq(&rq->lock);
4464 if (rq->active_balance) {
4465 active_load_balance(rq, cpu);
4466 rq->active_balance = 0;
4469 head = &rq->migration_queue;
4471 if (list_empty(head)) {
4472 spin_unlock_irq(&rq->lock);
4474 set_current_state(TASK_INTERRUPTIBLE);
4477 req = list_entry(head->next, migration_req_t, list);
4478 list_del_init(head->next);
4480 spin_unlock(&rq->lock);
4481 __migrate_task(req->task, cpu, req->dest_cpu);
4484 complete(&req->done);
4486 __set_current_state(TASK_RUNNING);
4490 /* Wait for kthread_stop */
4491 set_current_state(TASK_INTERRUPTIBLE);
4492 while (!kthread_should_stop()) {
4494 set_current_state(TASK_INTERRUPTIBLE);
4496 __set_current_state(TASK_RUNNING);
4500 #ifdef CONFIG_HOTPLUG_CPU
4501 /* Figure out where task on dead CPU should go, use force if neccessary. */
4502 static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *tsk)
4508 mask = node_to_cpumask(cpu_to_node(dead_cpu));
4509 cpus_and(mask, mask, tsk->cpus_allowed);
4510 dest_cpu = any_online_cpu(mask);
4512 /* On any allowed CPU? */
4513 if (dest_cpu == NR_CPUS)
4514 dest_cpu = any_online_cpu(tsk->cpus_allowed);
4516 /* No more Mr. Nice Guy. */
4517 if (dest_cpu == NR_CPUS) {
4518 cpus_setall(tsk->cpus_allowed);
4519 dest_cpu = any_online_cpu(tsk->cpus_allowed);
4522 * Don't tell them about moving exiting tasks or
4523 * kernel threads (both mm NULL), since they never
4526 if (tsk->mm && printk_ratelimit())
4527 printk(KERN_INFO "process %d (%s) no "
4528 "longer affine to cpu%d\n",
4529 tsk->pid, tsk->comm, dead_cpu);
4531 __migrate_task(tsk, dead_cpu, dest_cpu);
4535 * While a dead CPU has no uninterruptible tasks queued at this point,
4536 * it might still have a nonzero ->nr_uninterruptible counter, because
4537 * for performance reasons the counter is not stricly tracking tasks to
4538 * their home CPUs. So we just add the counter to another CPU's counter,
4539 * to keep the global sum constant after CPU-down:
4541 static void migrate_nr_uninterruptible(runqueue_t *rq_src)
4543 runqueue_t *rq_dest = cpu_rq(any_online_cpu(CPU_MASK_ALL));
4544 unsigned long flags;
4546 local_irq_save(flags);
4547 double_rq_lock(rq_src, rq_dest);
4548 rq_dest->nr_uninterruptible += rq_src->nr_uninterruptible;
4549 rq_src->nr_uninterruptible = 0;
4550 double_rq_unlock(rq_src, rq_dest);
4551 local_irq_restore(flags);
4554 /* Run through task list and migrate tasks from the dead cpu. */
4555 static void migrate_live_tasks(int src_cpu)
4557 struct task_struct *tsk, *t;
4559 write_lock_irq(&tasklist_lock);
4561 do_each_thread(t, tsk) {
4565 if (task_cpu(tsk) == src_cpu)
4566 move_task_off_dead_cpu(src_cpu, tsk);
4567 } while_each_thread(t, tsk);
4569 write_unlock_irq(&tasklist_lock);
4572 /* Schedules idle task to be the next runnable task on current CPU.
4573 * It does so by boosting its priority to highest possible and adding it to
4574 * the _front_ of runqueue. Used by CPU offline code.
4576 void sched_idle_next(void)
4578 int cpu = smp_processor_id();
4579 runqueue_t *rq = this_rq();
4580 struct task_struct *p = rq->idle;
4581 unsigned long flags;
4583 /* cpu has to be offline */
4584 BUG_ON(cpu_online(cpu));
4586 /* Strictly not necessary since rest of the CPUs are stopped by now
4587 * and interrupts disabled on current cpu.
4589 spin_lock_irqsave(&rq->lock, flags);
4591 __setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
4592 /* Add idle task to _front_ of it's priority queue */
4593 __activate_idle_task(p, rq);
4595 spin_unlock_irqrestore(&rq->lock, flags);
4598 /* Ensures that the idle task is using init_mm right before its cpu goes
4601 void idle_task_exit(void)
4603 struct mm_struct *mm = current->active_mm;
4605 BUG_ON(cpu_online(smp_processor_id()));
4608 switch_mm(mm, &init_mm, current);
4612 static void migrate_dead(unsigned int dead_cpu, task_t *tsk)
4614 struct runqueue *rq = cpu_rq(dead_cpu);
4616 /* Must be exiting, otherwise would be on tasklist. */
4617 BUG_ON(tsk->exit_state != EXIT_ZOMBIE && tsk->exit_state != EXIT_DEAD);
4619 /* Cannot have done final schedule yet: would have vanished. */
4620 BUG_ON(tsk->flags & PF_DEAD);
4622 get_task_struct(tsk);
4625 * Drop lock around migration; if someone else moves it,
4626 * that's OK. No task can be added to this CPU, so iteration is
4629 spin_unlock_irq(&rq->lock);
4630 move_task_off_dead_cpu(dead_cpu, tsk);
4631 spin_lock_irq(&rq->lock);
4633 put_task_struct(tsk);
4636 /* release_task() removes task from tasklist, so we won't find dead tasks. */
4637 static void migrate_dead_tasks(unsigned int dead_cpu)
4640 struct runqueue *rq = cpu_rq(dead_cpu);
4642 for (arr = 0; arr < 2; arr++) {
4643 for (i = 0; i < MAX_PRIO; i++) {
4644 struct list_head *list = &rq->arrays[arr].queue[i];
4645 while (!list_empty(list))
4646 migrate_dead(dead_cpu,
4647 list_entry(list->next, task_t,
4652 #endif /* CONFIG_HOTPLUG_CPU */
4655 * migration_call - callback that gets triggered when a CPU is added.
4656 * Here we can start up the necessary migration thread for the new CPU.
4658 static int migration_call(struct notifier_block *nfb, unsigned long action,
4661 int cpu = (long)hcpu;
4662 struct task_struct *p;
4663 struct runqueue *rq;
4664 unsigned long flags;
4667 case CPU_UP_PREPARE:
4668 p = kthread_create(migration_thread, hcpu, "migration/%d",cpu);
4671 p->flags |= PF_NOFREEZE;
4672 kthread_bind(p, cpu);
4673 /* Must be high prio: stop_machine expects to yield to it. */
4674 rq = task_rq_lock(p, &flags);
4675 __setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
4676 task_rq_unlock(rq, &flags);
4677 cpu_rq(cpu)->migration_thread = p;
4680 /* Strictly unneccessary, as first user will wake it. */
4681 wake_up_process(cpu_rq(cpu)->migration_thread);
4683 #ifdef CONFIG_HOTPLUG_CPU
4684 case CPU_UP_CANCELED:
4685 /* Unbind it from offline cpu so it can run. Fall thru. */
4686 kthread_bind(cpu_rq(cpu)->migration_thread,smp_processor_id());
4687 kthread_stop(cpu_rq(cpu)->migration_thread);
4688 cpu_rq(cpu)->migration_thread = NULL;
4691 migrate_live_tasks(cpu);
4693 kthread_stop(rq->migration_thread);
4694 rq->migration_thread = NULL;
4695 /* Idle task back to normal (off runqueue, low prio) */
4696 rq = task_rq_lock(rq->idle, &flags);
4697 deactivate_task(rq->idle, rq);
4698 rq->idle->static_prio = MAX_PRIO;
4699 __setscheduler(rq->idle, SCHED_NORMAL, 0);
4700 migrate_dead_tasks(cpu);
4701 task_rq_unlock(rq, &flags);
4702 migrate_nr_uninterruptible(rq);
4703 BUG_ON(rq->nr_running != 0);
4705 /* No need to migrate the tasks: it was best-effort if
4706 * they didn't do lock_cpu_hotplug(). Just wake up
4707 * the requestors. */
4708 spin_lock_irq(&rq->lock);
4709 while (!list_empty(&rq->migration_queue)) {
4710 migration_req_t *req;
4711 req = list_entry(rq->migration_queue.next,
4712 migration_req_t, list);
4713 list_del_init(&req->list);
4714 complete(&req->done);
4716 spin_unlock_irq(&rq->lock);
4723 /* Register at highest priority so that task migration (migrate_all_tasks)
4724 * happens before everything else.
4726 static struct notifier_block __devinitdata migration_notifier = {
4727 .notifier_call = migration_call,
4731 int __init migration_init(void)
4733 void *cpu = (void *)(long)smp_processor_id();
4734 /* Start one for boot CPU. */
4735 migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
4736 migration_call(&migration_notifier, CPU_ONLINE, cpu);
4737 register_cpu_notifier(&migration_notifier);
4743 #undef SCHED_DOMAIN_DEBUG
4744 #ifdef SCHED_DOMAIN_DEBUG
4745 static void sched_domain_debug(struct sched_domain *sd, int cpu)
4750 printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
4754 printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
4759 struct sched_group *group = sd->groups;
4760 cpumask_t groupmask;
4762 cpumask_scnprintf(str, NR_CPUS, sd->span);
4763 cpus_clear(groupmask);
4766 for (i = 0; i < level + 1; i++)
4768 printk("domain %d: ", level);
4770 if (!(sd->flags & SD_LOAD_BALANCE)) {
4771 printk("does not load-balance\n");
4773 printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain has parent");
4777 printk("span %s\n", str);
4779 if (!cpu_isset(cpu, sd->span))
4780 printk(KERN_ERR "ERROR: domain->span does not contain CPU%d\n", cpu);
4781 if (!cpu_isset(cpu, group->cpumask))
4782 printk(KERN_ERR "ERROR: domain->groups does not contain CPU%d\n", cpu);
4785 for (i = 0; i < level + 2; i++)
4791 printk(KERN_ERR "ERROR: group is NULL\n");
4795 if (!group->cpu_power) {
4797 printk(KERN_ERR "ERROR: domain->cpu_power not set\n");
4800 if (!cpus_weight(group->cpumask)) {
4802 printk(KERN_ERR "ERROR: empty group\n");
4805 if (cpus_intersects(groupmask, group->cpumask)) {
4807 printk(KERN_ERR "ERROR: repeated CPUs\n");
4810 cpus_or(groupmask, groupmask, group->cpumask);
4812 cpumask_scnprintf(str, NR_CPUS, group->cpumask);
4815 group = group->next;
4816 } while (group != sd->groups);
4819 if (!cpus_equal(sd->span, groupmask))
4820 printk(KERN_ERR "ERROR: groups don't span domain->span\n");
4826 if (!cpus_subset(groupmask, sd->span))
4827 printk(KERN_ERR "ERROR: parent span is not a superset of domain->span\n");
4833 #define sched_domain_debug(sd, cpu) {}
4836 static int sd_degenerate(struct sched_domain *sd)
4838 if (cpus_weight(sd->span) == 1)
4841 /* Following flags need at least 2 groups */
4842 if (sd->flags & (SD_LOAD_BALANCE |
4843 SD_BALANCE_NEWIDLE |
4846 if (sd->groups != sd->groups->next)
4850 /* Following flags don't use groups */
4851 if (sd->flags & (SD_WAKE_IDLE |
4859 static int sd_parent_degenerate(struct sched_domain *sd,
4860 struct sched_domain *parent)
4862 unsigned long cflags = sd->flags, pflags = parent->flags;
4864 if (sd_degenerate(parent))
4867 if (!cpus_equal(sd->span, parent->span))
4870 /* Does parent contain flags not in child? */
4871 /* WAKE_BALANCE is a subset of WAKE_AFFINE */
4872 if (cflags & SD_WAKE_AFFINE)
4873 pflags &= ~SD_WAKE_BALANCE;
4874 /* Flags needing groups don't count if only 1 group in parent */
4875 if (parent->groups == parent->groups->next) {
4876 pflags &= ~(SD_LOAD_BALANCE |
4877 SD_BALANCE_NEWIDLE |
4881 if (~cflags & pflags)
4888 * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
4889 * hold the hotplug lock.
4891 static void cpu_attach_domain(struct sched_domain *sd, int cpu)
4893 runqueue_t *rq = cpu_rq(cpu);
4894 struct sched_domain *tmp;
4896 /* Remove the sched domains which do not contribute to scheduling. */
4897 for (tmp = sd; tmp; tmp = tmp->parent) {
4898 struct sched_domain *parent = tmp->parent;
4901 if (sd_parent_degenerate(tmp, parent))
4902 tmp->parent = parent->parent;
4905 if (sd && sd_degenerate(sd))
4908 sched_domain_debug(sd, cpu);
4910 rcu_assign_pointer(rq->sd, sd);
4913 /* cpus with isolated domains */
4914 static cpumask_t __devinitdata cpu_isolated_map = CPU_MASK_NONE;
4916 /* Setup the mask of cpus configured for isolated domains */
4917 static int __init isolated_cpu_setup(char *str)
4919 int ints[NR_CPUS], i;
4921 str = get_options(str, ARRAY_SIZE(ints), ints);
4922 cpus_clear(cpu_isolated_map);
4923 for (i = 1; i <= ints[0]; i++)
4924 if (ints[i] < NR_CPUS)
4925 cpu_set(ints[i], cpu_isolated_map);
4929 __setup ("isolcpus=", isolated_cpu_setup);
4932 * init_sched_build_groups takes an array of groups, the cpumask we wish
4933 * to span, and a pointer to a function which identifies what group a CPU
4934 * belongs to. The return value of group_fn must be a valid index into the
4935 * groups[] array, and must be >= 0 and < NR_CPUS (due to the fact that we
4936 * keep track of groups covered with a cpumask_t).
4938 * init_sched_build_groups will build a circular linked list of the groups
4939 * covered by the given span, and will set each group's ->cpumask correctly,
4940 * and ->cpu_power to 0.
4942 static void init_sched_build_groups(struct sched_group groups[], cpumask_t span,
4943 int (*group_fn)(int cpu))
4945 struct sched_group *first = NULL, *last = NULL;
4946 cpumask_t covered = CPU_MASK_NONE;
4949 for_each_cpu_mask(i, span) {
4950 int group = group_fn(i);
4951 struct sched_group *sg = &groups[group];
4954 if (cpu_isset(i, covered))
4957 sg->cpumask = CPU_MASK_NONE;
4960 for_each_cpu_mask(j, span) {
4961 if (group_fn(j) != group)
4964 cpu_set(j, covered);
4965 cpu_set(j, sg->cpumask);
4976 #define SD_NODES_PER_DOMAIN 16
4980 * find_next_best_node - find the next node to include in a sched_domain
4981 * @node: node whose sched_domain we're building
4982 * @used_nodes: nodes already in the sched_domain
4984 * Find the next node to include in a given scheduling domain. Simply
4985 * finds the closest node not already in the @used_nodes map.
4987 * Should use nodemask_t.
4989 static int find_next_best_node(int node, unsigned long *used_nodes)
4991 int i, n, val, min_val, best_node = 0;
4995 for (i = 0; i < MAX_NUMNODES; i++) {
4996 /* Start at @node */
4997 n = (node + i) % MAX_NUMNODES;
4999 if (!nr_cpus_node(n))
5002 /* Skip already used nodes */
5003 if (test_bit(n, used_nodes))
5006 /* Simple min distance search */
5007 val = node_distance(node, n);
5009 if (val < min_val) {
5015 set_bit(best_node, used_nodes);
5020 * sched_domain_node_span - get a cpumask for a node's sched_domain
5021 * @node: node whose cpumask we're constructing
5022 * @size: number of nodes to include in this span
5024 * Given a node, construct a good cpumask for its sched_domain to span. It
5025 * should be one that prevents unnecessary balancing, but also spreads tasks
5028 static cpumask_t sched_domain_node_span(int node)
5031 cpumask_t span, nodemask;
5032 DECLARE_BITMAP(used_nodes, MAX_NUMNODES);
5035 bitmap_zero(used_nodes, MAX_NUMNODES);
5037 nodemask = node_to_cpumask(node);
5038 cpus_or(span, span, nodemask);
5039 set_bit(node, used_nodes);
5041 for (i = 1; i < SD_NODES_PER_DOMAIN; i++) {
5042 int next_node = find_next_best_node(node, used_nodes);
5043 nodemask = node_to_cpumask(next_node);
5044 cpus_or(span, span, nodemask);
5052 * At the moment, CONFIG_SCHED_SMT is never defined, but leave it in so we
5053 * can switch it on easily if needed.
5055 #ifdef CONFIG_SCHED_SMT
5056 static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
5057 static struct sched_group sched_group_cpus[NR_CPUS];
5058 static int cpu_to_cpu_group(int cpu)
5064 static DEFINE_PER_CPU(struct sched_domain, phys_domains);
5065 static struct sched_group sched_group_phys[NR_CPUS];
5066 static int cpu_to_phys_group(int cpu)
5068 #ifdef CONFIG_SCHED_SMT
5069 return first_cpu(cpu_sibling_map[cpu]);
5077 * The init_sched_build_groups can't handle what we want to do with node
5078 * groups, so roll our own. Now each node has its own list of groups which
5079 * gets dynamically allocated.
5081 static DEFINE_PER_CPU(struct sched_domain, node_domains);
5082 static struct sched_group **sched_group_nodes_bycpu[NR_CPUS];
5084 static DEFINE_PER_CPU(struct sched_domain, allnodes_domains);
5085 static struct sched_group *sched_group_allnodes_bycpu[NR_CPUS];
5087 static int cpu_to_allnodes_group(int cpu)
5089 return cpu_to_node(cpu);
5094 * Build sched domains for a given set of cpus and attach the sched domains
5095 * to the individual cpus
5097 void build_sched_domains(const cpumask_t *cpu_map)
5101 struct sched_group **sched_group_nodes = NULL;
5102 struct sched_group *sched_group_allnodes = NULL;
5105 * Allocate the per-node list of sched groups
5107 sched_group_nodes = kmalloc(sizeof(struct sched_group*)*MAX_NUMNODES,
5109 if (!sched_group_nodes) {
5110 printk(KERN_WARNING "Can not alloc sched group node list\n");
5113 sched_group_nodes_bycpu[first_cpu(*cpu_map)] = sched_group_nodes;
5117 * Set up domains for cpus specified by the cpu_map.
5119 for_each_cpu_mask(i, *cpu_map) {
5121 struct sched_domain *sd = NULL, *p;
5122 cpumask_t nodemask = node_to_cpumask(cpu_to_node(i));
5124 cpus_and(nodemask, nodemask, *cpu_map);
5127 if (cpus_weight(*cpu_map)
5128 > SD_NODES_PER_DOMAIN*cpus_weight(nodemask)) {
5129 if (!sched_group_allnodes) {
5130 sched_group_allnodes
5131 = kmalloc(sizeof(struct sched_group)
5134 if (!sched_group_allnodes) {
5136 "Can not alloc allnodes sched group\n");
5139 sched_group_allnodes_bycpu[i]
5140 = sched_group_allnodes;
5142 sd = &per_cpu(allnodes_domains, i);
5143 *sd = SD_ALLNODES_INIT;
5144 sd->span = *cpu_map;
5145 group = cpu_to_allnodes_group(i);
5146 sd->groups = &sched_group_allnodes[group];
5151 sd = &per_cpu(node_domains, i);
5153 sd->span = sched_domain_node_span(cpu_to_node(i));
5155 cpus_and(sd->span, sd->span, *cpu_map);
5159 sd = &per_cpu(phys_domains, i);
5160 group = cpu_to_phys_group(i);
5162 sd->span = nodemask;
5164 sd->groups = &sched_group_phys[group];
5166 #ifdef CONFIG_SCHED_SMT
5168 sd = &per_cpu(cpu_domains, i);
5169 group = cpu_to_cpu_group(i);
5170 *sd = SD_SIBLING_INIT;
5171 sd->span = cpu_sibling_map[i];
5172 cpus_and(sd->span, sd->span, *cpu_map);
5174 sd->groups = &sched_group_cpus[group];
5178 #ifdef CONFIG_SCHED_SMT
5179 /* Set up CPU (sibling) groups */
5180 for_each_cpu_mask(i, *cpu_map) {
5181 cpumask_t this_sibling_map = cpu_sibling_map[i];
5182 cpus_and(this_sibling_map, this_sibling_map, *cpu_map);
5183 if (i != first_cpu(this_sibling_map))
5186 init_sched_build_groups(sched_group_cpus, this_sibling_map,
5191 /* Set up physical groups */
5192 for (i = 0; i < MAX_NUMNODES; i++) {
5193 cpumask_t nodemask = node_to_cpumask(i);
5195 cpus_and(nodemask, nodemask, *cpu_map);
5196 if (cpus_empty(nodemask))
5199 init_sched_build_groups(sched_group_phys, nodemask,
5200 &cpu_to_phys_group);
5204 /* Set up node groups */
5205 if (sched_group_allnodes)
5206 init_sched_build_groups(sched_group_allnodes, *cpu_map,
5207 &cpu_to_allnodes_group);
5209 for (i = 0; i < MAX_NUMNODES; i++) {
5210 /* Set up node groups */
5211 struct sched_group *sg, *prev;
5212 cpumask_t nodemask = node_to_cpumask(i);
5213 cpumask_t domainspan;
5214 cpumask_t covered = CPU_MASK_NONE;
5217 cpus_and(nodemask, nodemask, *cpu_map);
5218 if (cpus_empty(nodemask)) {
5219 sched_group_nodes[i] = NULL;
5223 domainspan = sched_domain_node_span(i);
5224 cpus_and(domainspan, domainspan, *cpu_map);
5226 sg = kmalloc(sizeof(struct sched_group), GFP_KERNEL);
5227 sched_group_nodes[i] = sg;
5228 for_each_cpu_mask(j, nodemask) {
5229 struct sched_domain *sd;
5230 sd = &per_cpu(node_domains, j);
5232 if (sd->groups == NULL) {
5233 /* Turn off balancing if we have no groups */
5239 "Can not alloc domain group for node %d\n", i);
5243 sg->cpumask = nodemask;
5244 cpus_or(covered, covered, nodemask);
5247 for (j = 0; j < MAX_NUMNODES; j++) {
5248 cpumask_t tmp, notcovered;
5249 int n = (i + j) % MAX_NUMNODES;
5251 cpus_complement(notcovered, covered);
5252 cpus_and(tmp, notcovered, *cpu_map);
5253 cpus_and(tmp, tmp, domainspan);
5254 if (cpus_empty(tmp))
5257 nodemask = node_to_cpumask(n);
5258 cpus_and(tmp, tmp, nodemask);
5259 if (cpus_empty(tmp))
5262 sg = kmalloc(sizeof(struct sched_group), GFP_KERNEL);
5265 "Can not alloc domain group for node %d\n", j);
5270 cpus_or(covered, covered, tmp);
5274 prev->next = sched_group_nodes[i];
5278 /* Calculate CPU power for physical packages and nodes */
5279 for_each_cpu_mask(i, *cpu_map) {
5281 struct sched_domain *sd;
5282 #ifdef CONFIG_SCHED_SMT
5283 sd = &per_cpu(cpu_domains, i);
5284 power = SCHED_LOAD_SCALE;
5285 sd->groups->cpu_power = power;
5288 sd = &per_cpu(phys_domains, i);
5289 power = SCHED_LOAD_SCALE + SCHED_LOAD_SCALE *
5290 (cpus_weight(sd->groups->cpumask)-1) / 10;
5291 sd->groups->cpu_power = power;
5294 sd = &per_cpu(allnodes_domains, i);
5296 power = SCHED_LOAD_SCALE + SCHED_LOAD_SCALE *
5297 (cpus_weight(sd->groups->cpumask)-1) / 10;
5298 sd->groups->cpu_power = power;
5304 for (i = 0; i < MAX_NUMNODES; i++) {
5305 struct sched_group *sg = sched_group_nodes[i];
5311 for_each_cpu_mask(j, sg->cpumask) {
5312 struct sched_domain *sd;
5315 sd = &per_cpu(phys_domains, j);
5316 if (j != first_cpu(sd->groups->cpumask)) {
5318 * Only add "power" once for each
5323 power = SCHED_LOAD_SCALE + SCHED_LOAD_SCALE *
5324 (cpus_weight(sd->groups->cpumask)-1) / 10;
5326 sg->cpu_power += power;
5329 if (sg != sched_group_nodes[i])
5334 /* Attach the domains */
5335 for_each_cpu_mask(i, *cpu_map) {
5336 struct sched_domain *sd;
5337 #ifdef CONFIG_SCHED_SMT
5338 sd = &per_cpu(cpu_domains, i);
5340 sd = &per_cpu(phys_domains, i);
5342 cpu_attach_domain(sd, i);
5346 * Set up scheduler domains and groups. Callers must hold the hotplug lock.
5348 static void arch_init_sched_domains(const cpumask_t *cpu_map)
5350 cpumask_t cpu_default_map;
5353 * Setup mask for cpus without special case scheduling requirements.
5354 * For now this just excludes isolated cpus, but could be used to
5355 * exclude other special cases in the future.
5357 cpus_andnot(cpu_default_map, *cpu_map, cpu_isolated_map);
5359 build_sched_domains(&cpu_default_map);
5362 static void arch_destroy_sched_domains(const cpumask_t *cpu_map)
5368 for_each_cpu_mask(cpu, *cpu_map) {
5369 struct sched_group *sched_group_allnodes
5370 = sched_group_allnodes_bycpu[cpu];
5371 struct sched_group **sched_group_nodes
5372 = sched_group_nodes_bycpu[cpu];
5374 if (sched_group_allnodes) {
5375 kfree(sched_group_allnodes);
5376 sched_group_allnodes_bycpu[cpu] = NULL;
5379 if (!sched_group_nodes)
5382 for (i = 0; i < MAX_NUMNODES; i++) {
5383 cpumask_t nodemask = node_to_cpumask(i);
5384 struct sched_group *oldsg, *sg = sched_group_nodes[i];
5386 cpus_and(nodemask, nodemask, *cpu_map);
5387 if (cpus_empty(nodemask))
5397 if (oldsg != sched_group_nodes[i])
5400 kfree(sched_group_nodes);
5401 sched_group_nodes_bycpu[cpu] = NULL;
5407 * Detach sched domains from a group of cpus specified in cpu_map
5408 * These cpus will now be attached to the NULL domain
5410 static inline void detach_destroy_domains(const cpumask_t *cpu_map)
5414 for_each_cpu_mask(i, *cpu_map)
5415 cpu_attach_domain(NULL, i);
5416 synchronize_sched();
5417 arch_destroy_sched_domains(cpu_map);
5421 * Partition sched domains as specified by the cpumasks below.
5422 * This attaches all cpus from the cpumasks to the NULL domain,
5423 * waits for a RCU quiescent period, recalculates sched
5424 * domain information and then attaches them back to the
5425 * correct sched domains
5426 * Call with hotplug lock held
5428 void partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2)
5430 cpumask_t change_map;
5432 cpus_and(*partition1, *partition1, cpu_online_map);
5433 cpus_and(*partition2, *partition2, cpu_online_map);
5434 cpus_or(change_map, *partition1, *partition2);
5436 /* Detach sched domains from all of the affected cpus */
5437 detach_destroy_domains(&change_map);
5438 if (!cpus_empty(*partition1))
5439 build_sched_domains(partition1);
5440 if (!cpus_empty(*partition2))
5441 build_sched_domains(partition2);
5444 #ifdef CONFIG_HOTPLUG_CPU
5446 * Force a reinitialization of the sched domains hierarchy. The domains
5447 * and groups cannot be updated in place without racing with the balancing
5448 * code, so we temporarily attach all running cpus to the NULL domain
5449 * which will prevent rebalancing while the sched domains are recalculated.
5451 static int update_sched_domains(struct notifier_block *nfb,
5452 unsigned long action, void *hcpu)
5455 case CPU_UP_PREPARE:
5456 case CPU_DOWN_PREPARE:
5457 detach_destroy_domains(&cpu_online_map);
5460 case CPU_UP_CANCELED:
5461 case CPU_DOWN_FAILED:
5465 * Fall through and re-initialise the domains.
5472 /* The hotplug lock is already held by cpu_up/cpu_down */
5473 arch_init_sched_domains(&cpu_online_map);
5479 void __init sched_init_smp(void)
5482 arch_init_sched_domains(&cpu_online_map);
5483 unlock_cpu_hotplug();
5484 /* XXX: Theoretical race here - CPU may be hotplugged now */
5485 hotcpu_notifier(update_sched_domains, 0);
5488 void __init sched_init_smp(void)
5491 #endif /* CONFIG_SMP */
5493 int in_sched_functions(unsigned long addr)
5495 /* Linker adds these: start and end of __sched functions */
5496 extern char __sched_text_start[], __sched_text_end[];
5497 return in_lock_functions(addr) ||
5498 (addr >= (unsigned long)__sched_text_start
5499 && addr < (unsigned long)__sched_text_end);
5502 void __init sched_init(void)
5507 for (i = 0; i < NR_CPUS; i++) {
5508 prio_array_t *array;
5511 spin_lock_init(&rq->lock);
5513 rq->active = rq->arrays;
5514 rq->expired = rq->arrays + 1;
5515 rq->best_expired_prio = MAX_PRIO;
5519 for (j = 1; j < 3; j++)
5520 rq->cpu_load[j] = 0;
5521 rq->active_balance = 0;
5523 rq->migration_thread = NULL;
5524 INIT_LIST_HEAD(&rq->migration_queue);
5526 atomic_set(&rq->nr_iowait, 0);
5528 for (j = 0; j < 2; j++) {
5529 array = rq->arrays + j;
5530 for (k = 0; k < MAX_PRIO; k++) {
5531 INIT_LIST_HEAD(array->queue + k);
5532 __clear_bit(k, array->bitmap);
5534 // delimiter for bitsearch
5535 __set_bit(MAX_PRIO, array->bitmap);
5540 * The boot idle thread does lazy MMU switching as well:
5542 atomic_inc(&init_mm.mm_count);
5543 enter_lazy_tlb(&init_mm, current);
5546 * Make us the idle thread. Technically, schedule() should not be
5547 * called from this thread, however somewhere below it might be,
5548 * but because we are the idle thread, we just pick up running again
5549 * when this runqueue becomes "idle".
5551 init_idle(current, smp_processor_id());
5554 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
5555 void __might_sleep(char *file, int line)
5557 #if defined(in_atomic)
5558 static unsigned long prev_jiffy; /* ratelimiting */
5560 if ((in_atomic() || irqs_disabled()) &&
5561 system_state == SYSTEM_RUNNING && !oops_in_progress) {
5562 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
5564 prev_jiffy = jiffies;
5565 printk(KERN_ERR "Debug: sleeping function called from invalid"
5566 " context at %s:%d\n", file, line);
5567 printk("in_atomic():%d, irqs_disabled():%d\n",
5568 in_atomic(), irqs_disabled());
5573 EXPORT_SYMBOL(__might_sleep);
5576 #ifdef CONFIG_MAGIC_SYSRQ
5577 void normalize_rt_tasks(void)
5579 struct task_struct *p;
5580 prio_array_t *array;
5581 unsigned long flags;
5584 read_lock_irq(&tasklist_lock);
5585 for_each_process (p) {
5589 rq = task_rq_lock(p, &flags);
5593 deactivate_task(p, task_rq(p));
5594 __setscheduler(p, SCHED_NORMAL, 0);
5596 __activate_task(p, task_rq(p));
5597 resched_task(rq->curr);
5600 task_rq_unlock(rq, &flags);
5602 read_unlock_irq(&tasklist_lock);
5605 #endif /* CONFIG_MAGIC_SYSRQ */
5609 * These functions are only useful for the IA64 MCA handling.
5611 * They can only be called when the whole system has been
5612 * stopped - every CPU needs to be quiescent, and no scheduling
5613 * activity can take place. Using them for anything else would
5614 * be a serious bug, and as a result, they aren't even visible
5615 * under any other configuration.
5619 * curr_task - return the current task for a given cpu.
5620 * @cpu: the processor in question.
5622 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
5624 task_t *curr_task(int cpu)
5626 return cpu_curr(cpu);
5630 * set_curr_task - set the current task for a given cpu.
5631 * @cpu: the processor in question.
5632 * @p: the task pointer to set.
5634 * Description: This function must only be used when non-maskable interrupts
5635 * are serviced on a separate stack. It allows the architecture to switch the
5636 * notion of the current task on a cpu in a non-blocking manner. This function
5637 * must be called with all CPU's synchronized, and interrupts disabled, the
5638 * and caller must save the original value of the current task (see
5639 * curr_task() above) and restore that value before reenabling interrupts and
5640 * re-starting the system.
5642 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
5644 void set_curr_task(int cpu, task_t *p)