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/capability.h>
31 #include <linux/completion.h>
32 #include <linux/kernel_stat.h>
33 #include <linux/security.h>
34 #include <linux/notifier.h>
35 #include <linux/profile.h>
36 #include <linux/suspend.h>
37 #include <linux/vmalloc.h>
38 #include <linux/blkdev.h>
39 #include <linux/delay.h>
40 #include <linux/smp.h>
41 #include <linux/threads.h>
42 #include <linux/timer.h>
43 #include <linux/rcupdate.h>
44 #include <linux/cpu.h>
45 #include <linux/cpuset.h>
46 #include <linux/percpu.h>
47 #include <linux/kthread.h>
48 #include <linux/seq_file.h>
49 #include <linux/syscalls.h>
50 #include <linux/times.h>
51 #include <linux/acct.h>
52 #include <linux/kprobes.h>
55 #include <asm/unistd.h>
58 * Convert user-nice values [ -20 ... 0 ... 19 ]
59 * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
62 #define NICE_TO_PRIO(nice) (MAX_RT_PRIO + (nice) + 20)
63 #define PRIO_TO_NICE(prio) ((prio) - MAX_RT_PRIO - 20)
64 #define TASK_NICE(p) PRIO_TO_NICE((p)->static_prio)
67 * 'User priority' is the nice value converted to something we
68 * can work with better when scaling various scheduler parameters,
69 * it's a [ 0 ... 39 ] range.
71 #define USER_PRIO(p) ((p)-MAX_RT_PRIO)
72 #define TASK_USER_PRIO(p) USER_PRIO((p)->static_prio)
73 #define MAX_USER_PRIO (USER_PRIO(MAX_PRIO))
76 * Some helpers for converting nanosecond timing to jiffy resolution
78 #define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ))
79 #define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ))
82 * These are the 'tuning knobs' of the scheduler:
84 * Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger),
85 * default timeslice is 100 msecs, maximum timeslice is 800 msecs.
86 * Timeslices get refilled after they expire.
88 #define MIN_TIMESLICE max(5 * HZ / 1000, 1)
89 #define DEF_TIMESLICE (100 * HZ / 1000)
90 #define ON_RUNQUEUE_WEIGHT 30
91 #define CHILD_PENALTY 95
92 #define PARENT_PENALTY 100
94 #define PRIO_BONUS_RATIO 25
95 #define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
96 #define INTERACTIVE_DELTA 2
97 #define MAX_SLEEP_AVG (DEF_TIMESLICE * MAX_BONUS)
98 #define STARVATION_LIMIT (MAX_SLEEP_AVG)
99 #define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG))
102 * If a task is 'interactive' then we reinsert it in the active
103 * array after it has expired its current timeslice. (it will not
104 * continue to run immediately, it will still roundrobin with
105 * other interactive tasks.)
107 * This part scales the interactivity limit depending on niceness.
109 * We scale it linearly, offset by the INTERACTIVE_DELTA delta.
110 * Here are a few examples of different nice levels:
112 * TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
113 * TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
114 * TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0]
115 * TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
116 * TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
118 * (the X axis represents the possible -5 ... 0 ... +5 dynamic
119 * priority range a task can explore, a value of '1' means the
120 * task is rated interactive.)
122 * Ie. nice +19 tasks can never get 'interactive' enough to be
123 * reinserted into the active array. And only heavily CPU-hog nice -20
124 * tasks will be expired. Default nice 0 tasks are somewhere between,
125 * it takes some effort for them to get interactive, but it's not
129 #define CURRENT_BONUS(p) \
130 (NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \
133 #define GRANULARITY (10 * HZ / 1000 ? : 1)
136 #define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
137 (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
140 #define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
141 (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)))
144 #define SCALE(v1,v1_max,v2_max) \
145 (v1) * (v2_max) / (v1_max)
148 (SCALE(TASK_NICE(p) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \
151 #define TASK_INTERACTIVE(p) \
152 ((p)->prio <= (p)->static_prio - DELTA(p))
154 #define INTERACTIVE_SLEEP(p) \
155 (JIFFIES_TO_NS(MAX_SLEEP_AVG * \
156 (MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
158 #define TASK_PREEMPTS_CURR(p, rq) \
159 ((p)->prio < (rq)->curr->prio)
162 * task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
163 * to time slice values: [800ms ... 100ms ... 5ms]
165 * The higher a thread's priority, the bigger timeslices
166 * it gets during one round of execution. But even the lowest
167 * priority thread gets MIN_TIMESLICE worth of execution time.
170 #define SCALE_PRIO(x, prio) \
171 max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE)
173 static unsigned int static_prio_timeslice(int static_prio
)
175 if (static_prio
< NICE_TO_PRIO(0))
176 return SCALE_PRIO(DEF_TIMESLICE
* 4, static_prio
);
178 return SCALE_PRIO(DEF_TIMESLICE
, static_prio
);
181 static inline unsigned int task_timeslice(task_t
*p
)
183 return static_prio_timeslice(p
->static_prio
);
186 #define task_hot(p, now, sd) ((long long) ((now) - (p)->last_ran) \
187 < (long long) (sd)->cache_hot_time)
190 * These are the runqueue data structures:
193 typedef struct runqueue runqueue_t
;
196 unsigned int nr_active
;
197 DECLARE_BITMAP(bitmap
, MAX_PRIO
+1); /* include 1 bit for delimiter */
198 struct list_head queue
[MAX_PRIO
];
202 * This is the main, per-CPU runqueue data structure.
204 * Locking rule: those places that want to lock multiple runqueues
205 * (such as the load balancing or the thread migration code), lock
206 * acquire operations must be ordered by ascending &runqueue.
212 * nr_running and cpu_load should be in the same cacheline because
213 * remote CPUs use both these fields when doing load calculation.
215 unsigned long nr_running
;
216 unsigned long raw_weighted_load
;
218 unsigned long cpu_load
[3];
220 unsigned long long nr_switches
;
223 * This is part of a global counter where only the total sum
224 * over all CPUs matters. A task can increase this counter on
225 * one CPU and if it got migrated afterwards it may decrease
226 * it on another CPU. Always updated under the runqueue lock:
228 unsigned long nr_uninterruptible
;
230 unsigned long expired_timestamp
;
231 unsigned long long timestamp_last_tick
;
233 struct mm_struct
*prev_mm
;
234 prio_array_t
*active
, *expired
, arrays
[2];
235 int best_expired_prio
;
239 struct sched_domain
*sd
;
241 /* For active balancing */
245 task_t
*migration_thread
;
246 struct list_head migration_queue
;
249 #ifdef CONFIG_SCHEDSTATS
251 struct sched_info rq_sched_info
;
253 /* sys_sched_yield() stats */
254 unsigned long yld_exp_empty
;
255 unsigned long yld_act_empty
;
256 unsigned long yld_both_empty
;
257 unsigned long yld_cnt
;
259 /* schedule() stats */
260 unsigned long sched_switch
;
261 unsigned long sched_cnt
;
262 unsigned long sched_goidle
;
264 /* try_to_wake_up() stats */
265 unsigned long ttwu_cnt
;
266 unsigned long ttwu_local
;
270 static DEFINE_PER_CPU(struct runqueue
, runqueues
);
273 * The domain tree (rq->sd) is protected by RCU's quiescent state transition.
274 * See detach_destroy_domains: synchronize_sched for details.
276 * The domain tree of any CPU may only be accessed from within
277 * preempt-disabled sections.
279 #define for_each_domain(cpu, domain) \
280 for (domain = rcu_dereference(cpu_rq(cpu)->sd); domain; domain = domain->parent)
282 #define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
283 #define this_rq() (&__get_cpu_var(runqueues))
284 #define task_rq(p) cpu_rq(task_cpu(p))
285 #define cpu_curr(cpu) (cpu_rq(cpu)->curr)
287 #ifndef prepare_arch_switch
288 # define prepare_arch_switch(next) do { } while (0)
290 #ifndef finish_arch_switch
291 # define finish_arch_switch(prev) do { } while (0)
294 #ifndef __ARCH_WANT_UNLOCKED_CTXSW
295 static inline int task_running(runqueue_t
*rq
, task_t
*p
)
297 return rq
->curr
== p
;
300 static inline void prepare_lock_switch(runqueue_t
*rq
, task_t
*next
)
304 static inline void finish_lock_switch(runqueue_t
*rq
, task_t
*prev
)
306 #ifdef CONFIG_DEBUG_SPINLOCK
307 /* this is a valid case when another task releases the spinlock */
308 rq
->lock
.owner
= current
;
310 spin_unlock_irq(&rq
->lock
);
313 #else /* __ARCH_WANT_UNLOCKED_CTXSW */
314 static inline int task_running(runqueue_t
*rq
, task_t
*p
)
319 return rq
->curr
== p
;
323 static inline void prepare_lock_switch(runqueue_t
*rq
, task_t
*next
)
327 * We can optimise this out completely for !SMP, because the
328 * SMP rebalancing from interrupt is the only thing that cares
333 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
334 spin_unlock_irq(&rq
->lock
);
336 spin_unlock(&rq
->lock
);
340 static inline void finish_lock_switch(runqueue_t
*rq
, task_t
*prev
)
344 * After ->oncpu is cleared, the task can be moved to a different CPU.
345 * We must ensure this doesn't happen until the switch is completely
351 #ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
355 #endif /* __ARCH_WANT_UNLOCKED_CTXSW */
358 * task_rq_lock - lock the runqueue a given task resides on and disable
359 * interrupts. Note the ordering: we can safely lookup the task_rq without
360 * explicitly disabling preemption.
362 static inline runqueue_t
*task_rq_lock(task_t
*p
, unsigned long *flags
)
368 local_irq_save(*flags
);
370 spin_lock(&rq
->lock
);
371 if (unlikely(rq
!= task_rq(p
))) {
372 spin_unlock_irqrestore(&rq
->lock
, *flags
);
373 goto repeat_lock_task
;
378 static inline void task_rq_unlock(runqueue_t
*rq
, unsigned long *flags
)
381 spin_unlock_irqrestore(&rq
->lock
, *flags
);
384 #ifdef CONFIG_SCHEDSTATS
386 * bump this up when changing the output format or the meaning of an existing
387 * format, so that tools can adapt (or abort)
389 #define SCHEDSTAT_VERSION 12
391 static int show_schedstat(struct seq_file
*seq
, void *v
)
395 seq_printf(seq
, "version %d\n", SCHEDSTAT_VERSION
);
396 seq_printf(seq
, "timestamp %lu\n", jiffies
);
397 for_each_online_cpu(cpu
) {
398 runqueue_t
*rq
= cpu_rq(cpu
);
400 struct sched_domain
*sd
;
404 /* runqueue-specific stats */
406 "cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
407 cpu
, rq
->yld_both_empty
,
408 rq
->yld_act_empty
, rq
->yld_exp_empty
, rq
->yld_cnt
,
409 rq
->sched_switch
, rq
->sched_cnt
, rq
->sched_goidle
,
410 rq
->ttwu_cnt
, rq
->ttwu_local
,
411 rq
->rq_sched_info
.cpu_time
,
412 rq
->rq_sched_info
.run_delay
, rq
->rq_sched_info
.pcnt
);
414 seq_printf(seq
, "\n");
417 /* domain-specific stats */
419 for_each_domain(cpu
, sd
) {
420 enum idle_type itype
;
421 char mask_str
[NR_CPUS
];
423 cpumask_scnprintf(mask_str
, NR_CPUS
, sd
->span
);
424 seq_printf(seq
, "domain%d %s", dcnt
++, mask_str
);
425 for (itype
= SCHED_IDLE
; itype
< MAX_IDLE_TYPES
;
427 seq_printf(seq
, " %lu %lu %lu %lu %lu %lu %lu %lu",
429 sd
->lb_balanced
[itype
],
430 sd
->lb_failed
[itype
],
431 sd
->lb_imbalance
[itype
],
432 sd
->lb_gained
[itype
],
433 sd
->lb_hot_gained
[itype
],
434 sd
->lb_nobusyq
[itype
],
435 sd
->lb_nobusyg
[itype
]);
437 seq_printf(seq
, " %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n",
438 sd
->alb_cnt
, sd
->alb_failed
, sd
->alb_pushed
,
439 sd
->sbe_cnt
, sd
->sbe_balanced
, sd
->sbe_pushed
,
440 sd
->sbf_cnt
, sd
->sbf_balanced
, sd
->sbf_pushed
,
441 sd
->ttwu_wake_remote
, sd
->ttwu_move_affine
, sd
->ttwu_move_balance
);
449 static int schedstat_open(struct inode
*inode
, struct file
*file
)
451 unsigned int size
= PAGE_SIZE
* (1 + num_online_cpus() / 32);
452 char *buf
= kmalloc(size
, GFP_KERNEL
);
458 res
= single_open(file
, show_schedstat
, NULL
);
460 m
= file
->private_data
;
468 struct file_operations proc_schedstat_operations
= {
469 .open
= schedstat_open
,
472 .release
= single_release
,
475 # define schedstat_inc(rq, field) do { (rq)->field++; } while (0)
476 # define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0)
477 #else /* !CONFIG_SCHEDSTATS */
478 # define schedstat_inc(rq, field) do { } while (0)
479 # define schedstat_add(rq, field, amt) do { } while (0)
483 * rq_lock - lock a given runqueue and disable interrupts.
485 static inline runqueue_t
*this_rq_lock(void)
492 spin_lock(&rq
->lock
);
497 #ifdef CONFIG_SCHEDSTATS
499 * Called when a process is dequeued from the active array and given
500 * the cpu. We should note that with the exception of interactive
501 * tasks, the expired queue will become the active queue after the active
502 * queue is empty, without explicitly dequeuing and requeuing tasks in the
503 * expired queue. (Interactive tasks may be requeued directly to the
504 * active queue, thus delaying tasks in the expired queue from running;
505 * see scheduler_tick()).
507 * This function is only called from sched_info_arrive(), rather than
508 * dequeue_task(). Even though a task may be queued and dequeued multiple
509 * times as it is shuffled about, we're really interested in knowing how
510 * long it was from the *first* time it was queued to the time that it
513 static inline void sched_info_dequeued(task_t
*t
)
515 t
->sched_info
.last_queued
= 0;
519 * Called when a task finally hits the cpu. We can now calculate how
520 * long it was waiting to run. We also note when it began so that we
521 * can keep stats on how long its timeslice is.
523 static void sched_info_arrive(task_t
*t
)
525 unsigned long now
= jiffies
, diff
= 0;
526 struct runqueue
*rq
= task_rq(t
);
528 if (t
->sched_info
.last_queued
)
529 diff
= now
- t
->sched_info
.last_queued
;
530 sched_info_dequeued(t
);
531 t
->sched_info
.run_delay
+= diff
;
532 t
->sched_info
.last_arrival
= now
;
533 t
->sched_info
.pcnt
++;
538 rq
->rq_sched_info
.run_delay
+= diff
;
539 rq
->rq_sched_info
.pcnt
++;
543 * Called when a process is queued into either the active or expired
544 * array. The time is noted and later used to determine how long we
545 * had to wait for us to reach the cpu. Since the expired queue will
546 * become the active queue after active queue is empty, without dequeuing
547 * and requeuing any tasks, we are interested in queuing to either. It
548 * is unusual but not impossible for tasks to be dequeued and immediately
549 * requeued in the same or another array: this can happen in sched_yield(),
550 * set_user_nice(), and even load_balance() as it moves tasks from runqueue
553 * This function is only called from enqueue_task(), but also only updates
554 * the timestamp if it is already not set. It's assumed that
555 * sched_info_dequeued() will clear that stamp when appropriate.
557 static inline void sched_info_queued(task_t
*t
)
559 if (!t
->sched_info
.last_queued
)
560 t
->sched_info
.last_queued
= jiffies
;
564 * Called when a process ceases being the active-running process, either
565 * voluntarily or involuntarily. Now we can calculate how long we ran.
567 static inline void sched_info_depart(task_t
*t
)
569 struct runqueue
*rq
= task_rq(t
);
570 unsigned long diff
= jiffies
- t
->sched_info
.last_arrival
;
572 t
->sched_info
.cpu_time
+= diff
;
575 rq
->rq_sched_info
.cpu_time
+= diff
;
579 * Called when tasks are switched involuntarily due, typically, to expiring
580 * their time slice. (This may also be called when switching to or from
581 * the idle task.) We are only called when prev != next.
583 static inline void sched_info_switch(task_t
*prev
, task_t
*next
)
585 struct runqueue
*rq
= task_rq(prev
);
588 * prev now departs the cpu. It's not interesting to record
589 * stats about how efficient we were at scheduling the idle
592 if (prev
!= rq
->idle
)
593 sched_info_depart(prev
);
595 if (next
!= rq
->idle
)
596 sched_info_arrive(next
);
599 #define sched_info_queued(t) do { } while (0)
600 #define sched_info_switch(t, next) do { } while (0)
601 #endif /* CONFIG_SCHEDSTATS */
604 * Adding/removing a task to/from a priority array:
606 static void dequeue_task(struct task_struct
*p
, prio_array_t
*array
)
609 list_del(&p
->run_list
);
610 if (list_empty(array
->queue
+ p
->prio
))
611 __clear_bit(p
->prio
, array
->bitmap
);
614 static void enqueue_task(struct task_struct
*p
, prio_array_t
*array
)
616 sched_info_queued(p
);
617 list_add_tail(&p
->run_list
, array
->queue
+ p
->prio
);
618 __set_bit(p
->prio
, array
->bitmap
);
624 * Put task to the end of the run list without the overhead of dequeue
625 * followed by enqueue.
627 static void requeue_task(struct task_struct
*p
, prio_array_t
*array
)
629 list_move_tail(&p
->run_list
, array
->queue
+ p
->prio
);
632 static inline void enqueue_task_head(struct task_struct
*p
, prio_array_t
*array
)
634 list_add(&p
->run_list
, array
->queue
+ p
->prio
);
635 __set_bit(p
->prio
, array
->bitmap
);
641 * effective_prio - return the priority that is based on the static
642 * priority but is modified by bonuses/penalties.
644 * We scale the actual sleep average [0 .... MAX_SLEEP_AVG]
645 * into the -5 ... 0 ... +5 bonus/penalty range.
647 * We use 25% of the full 0...39 priority range so that:
649 * 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs.
650 * 2) nice -20 CPU hogs do not get preempted by nice 0 tasks.
652 * Both properties are important to certain workloads.
654 static int effective_prio(task_t
*p
)
661 bonus
= CURRENT_BONUS(p
) - MAX_BONUS
/ 2;
663 prio
= p
->static_prio
- bonus
;
664 if (prio
< MAX_RT_PRIO
)
666 if (prio
> MAX_PRIO
-1)
672 * To aid in avoiding the subversion of "niceness" due to uneven distribution
673 * of tasks with abnormal "nice" values across CPUs the contribution that
674 * each task makes to its run queue's load is weighted according to its
675 * scheduling class and "nice" value. For SCHED_NORMAL tasks this is just a
676 * scaled version of the new time slice allocation that they receive on time
681 * Assume: static_prio_timeslice(NICE_TO_PRIO(0)) == DEF_TIMESLICE
682 * If static_prio_timeslice() is ever changed to break this assumption then
683 * this code will need modification
685 #define TIME_SLICE_NICE_ZERO DEF_TIMESLICE
686 #define LOAD_WEIGHT(lp) \
687 (((lp) * SCHED_LOAD_SCALE) / TIME_SLICE_NICE_ZERO)
688 #define PRIO_TO_LOAD_WEIGHT(prio) \
689 LOAD_WEIGHT(static_prio_timeslice(prio))
690 #define RTPRIO_TO_LOAD_WEIGHT(rp) \
691 (PRIO_TO_LOAD_WEIGHT(MAX_RT_PRIO) + LOAD_WEIGHT(rp))
693 static void set_load_weight(task_t
*p
)
697 if (p
== task_rq(p
)->migration_thread
)
699 * The migration thread does the actual balancing.
700 * Giving its load any weight will skew balancing
706 p
->load_weight
= RTPRIO_TO_LOAD_WEIGHT(p
->rt_priority
);
708 p
->load_weight
= PRIO_TO_LOAD_WEIGHT(p
->static_prio
);
711 static inline void inc_raw_weighted_load(runqueue_t
*rq
, const task_t
*p
)
713 rq
->raw_weighted_load
+= p
->load_weight
;
716 static inline void dec_raw_weighted_load(runqueue_t
*rq
, const task_t
*p
)
718 rq
->raw_weighted_load
-= p
->load_weight
;
721 static inline void inc_nr_running(task_t
*p
, runqueue_t
*rq
)
724 inc_raw_weighted_load(rq
, p
);
727 static inline void dec_nr_running(task_t
*p
, runqueue_t
*rq
)
730 dec_raw_weighted_load(rq
, p
);
734 * __activate_task - move a task to the runqueue.
736 static void __activate_task(task_t
*p
, runqueue_t
*rq
)
738 prio_array_t
*target
= rq
->active
;
741 target
= rq
->expired
;
742 enqueue_task(p
, target
);
743 inc_nr_running(p
, rq
);
747 * __activate_idle_task - move idle task to the _front_ of runqueue.
749 static inline void __activate_idle_task(task_t
*p
, runqueue_t
*rq
)
751 enqueue_task_head(p
, rq
->active
);
752 inc_nr_running(p
, rq
);
755 static int recalc_task_prio(task_t
*p
, unsigned long long now
)
757 /* Caller must always ensure 'now >= p->timestamp' */
758 unsigned long sleep_time
= now
- p
->timestamp
;
763 if (likely(sleep_time
> 0)) {
765 * This ceiling is set to the lowest priority that would allow
766 * a task to be reinserted into the active array on timeslice
769 unsigned long ceiling
= INTERACTIVE_SLEEP(p
);
771 if (p
->mm
&& sleep_time
> ceiling
&& p
->sleep_avg
< ceiling
) {
773 * Prevents user tasks from achieving best priority
774 * with one single large enough sleep.
776 p
->sleep_avg
= ceiling
;
778 * Using INTERACTIVE_SLEEP() as a ceiling places a
779 * nice(0) task 1ms sleep away from promotion, and
780 * gives it 700ms to round-robin with no chance of
781 * being demoted. This is more than generous, so
782 * mark this sleep as non-interactive to prevent the
783 * on-runqueue bonus logic from intervening should
784 * this task not receive cpu immediately.
786 p
->sleep_type
= SLEEP_NONINTERACTIVE
;
789 * Tasks waking from uninterruptible sleep are
790 * limited in their sleep_avg rise as they
791 * are likely to be waiting on I/O
793 if (p
->sleep_type
== SLEEP_NONINTERACTIVE
&& p
->mm
) {
794 if (p
->sleep_avg
>= ceiling
)
796 else if (p
->sleep_avg
+ sleep_time
>=
798 p
->sleep_avg
= ceiling
;
804 * This code gives a bonus to interactive tasks.
806 * The boost works by updating the 'average sleep time'
807 * value here, based on ->timestamp. The more time a
808 * task spends sleeping, the higher the average gets -
809 * and the higher the priority boost gets as well.
811 p
->sleep_avg
+= sleep_time
;
814 if (p
->sleep_avg
> NS_MAX_SLEEP_AVG
)
815 p
->sleep_avg
= NS_MAX_SLEEP_AVG
;
818 return effective_prio(p
);
822 * activate_task - move a task to the runqueue and do priority recalculation
824 * Update all the scheduling statistics stuff. (sleep average
825 * calculation, priority modifiers, etc.)
827 static void activate_task(task_t
*p
, runqueue_t
*rq
, int local
)
829 unsigned long long now
;
834 /* Compensate for drifting sched_clock */
835 runqueue_t
*this_rq
= this_rq();
836 now
= (now
- this_rq
->timestamp_last_tick
)
837 + rq
->timestamp_last_tick
;
842 p
->prio
= recalc_task_prio(p
, now
);
845 * This checks to make sure it's not an uninterruptible task
846 * that is now waking up.
848 if (p
->sleep_type
== SLEEP_NORMAL
) {
850 * Tasks which were woken up by interrupts (ie. hw events)
851 * are most likely of interactive nature. So we give them
852 * the credit of extending their sleep time to the period
853 * of time they spend on the runqueue, waiting for execution
854 * on a CPU, first time around:
857 p
->sleep_type
= SLEEP_INTERRUPTED
;
860 * Normal first-time wakeups get a credit too for
861 * on-runqueue time, but it will be weighted down:
863 p
->sleep_type
= SLEEP_INTERACTIVE
;
868 __activate_task(p
, rq
);
872 * deactivate_task - remove a task from the runqueue.
874 static void deactivate_task(struct task_struct
*p
, runqueue_t
*rq
)
876 dec_nr_running(p
, rq
);
877 dequeue_task(p
, p
->array
);
882 * resched_task - mark a task 'to be rescheduled now'.
884 * On UP this means the setting of the need_resched flag, on SMP it
885 * might also involve a cross-CPU call to trigger the scheduler on
890 #ifndef tsk_is_polling
891 #define tsk_is_polling(t) test_tsk_thread_flag(t, TIF_POLLING_NRFLAG)
894 static void resched_task(task_t
*p
)
898 assert_spin_locked(&task_rq(p
)->lock
);
900 if (unlikely(test_tsk_thread_flag(p
, TIF_NEED_RESCHED
)))
903 set_tsk_thread_flag(p
, TIF_NEED_RESCHED
);
906 if (cpu
== smp_processor_id())
909 /* NEED_RESCHED must be visible before we test polling */
911 if (!tsk_is_polling(p
))
912 smp_send_reschedule(cpu
);
915 static inline void resched_task(task_t
*p
)
917 assert_spin_locked(&task_rq(p
)->lock
);
918 set_tsk_need_resched(p
);
923 * task_curr - is this task currently executing on a CPU?
924 * @p: the task in question.
926 inline int task_curr(const task_t
*p
)
928 return cpu_curr(task_cpu(p
)) == p
;
931 /* Used instead of source_load when we know the type == 0 */
932 unsigned long weighted_cpuload(const int cpu
)
934 return cpu_rq(cpu
)->raw_weighted_load
;
939 struct list_head list
;
944 struct completion done
;
948 * The task's runqueue lock must be held.
949 * Returns true if you have to wait for migration thread.
951 static int migrate_task(task_t
*p
, int dest_cpu
, migration_req_t
*req
)
953 runqueue_t
*rq
= task_rq(p
);
956 * If the task is not on a runqueue (and not running), then
957 * it is sufficient to simply update the task's cpu field.
959 if (!p
->array
&& !task_running(rq
, p
)) {
960 set_task_cpu(p
, dest_cpu
);
964 init_completion(&req
->done
);
966 req
->dest_cpu
= dest_cpu
;
967 list_add(&req
->list
, &rq
->migration_queue
);
972 * wait_task_inactive - wait for a thread to unschedule.
974 * The caller must ensure that the task *will* unschedule sometime soon,
975 * else this function might spin for a *long* time. This function can't
976 * be called with interrupts off, or it may introduce deadlock with
977 * smp_call_function() if an IPI is sent by the same process we are
978 * waiting to become inactive.
980 void wait_task_inactive(task_t
*p
)
987 rq
= task_rq_lock(p
, &flags
);
988 /* Must be off runqueue entirely, not preempted. */
989 if (unlikely(p
->array
|| task_running(rq
, p
))) {
990 /* If it's preempted, we yield. It could be a while. */
991 preempted
= !task_running(rq
, p
);
992 task_rq_unlock(rq
, &flags
);
998 task_rq_unlock(rq
, &flags
);
1002 * kick_process - kick a running thread to enter/exit the kernel
1003 * @p: the to-be-kicked thread
1005 * Cause a process which is running on another CPU to enter
1006 * kernel-mode, without any delay. (to get signals handled.)
1008 * NOTE: this function doesnt have to take the runqueue lock,
1009 * because all it wants to ensure is that the remote task enters
1010 * the kernel. If the IPI races and the task has been migrated
1011 * to another CPU then no harm is done and the purpose has been
1014 void kick_process(task_t
*p
)
1020 if ((cpu
!= smp_processor_id()) && task_curr(p
))
1021 smp_send_reschedule(cpu
);
1026 * Return a low guess at the load of a migration-source cpu weighted
1027 * according to the scheduling class and "nice" value.
1029 * We want to under-estimate the load of migration sources, to
1030 * balance conservatively.
1032 static inline unsigned long source_load(int cpu
, int type
)
1034 runqueue_t
*rq
= cpu_rq(cpu
);
1037 return rq
->raw_weighted_load
;
1039 return min(rq
->cpu_load
[type
-1], rq
->raw_weighted_load
);
1043 * Return a high guess at the load of a migration-target cpu weighted
1044 * according to the scheduling class and "nice" value.
1046 static inline unsigned long target_load(int cpu
, int type
)
1048 runqueue_t
*rq
= cpu_rq(cpu
);
1051 return rq
->raw_weighted_load
;
1053 return max(rq
->cpu_load
[type
-1], rq
->raw_weighted_load
);
1057 * Return the average load per task on the cpu's run queue
1059 static inline unsigned long cpu_avg_load_per_task(int cpu
)
1061 runqueue_t
*rq
= cpu_rq(cpu
);
1062 unsigned long n
= rq
->nr_running
;
1064 return n
? rq
->raw_weighted_load
/ n
: SCHED_LOAD_SCALE
;
1068 * find_idlest_group finds and returns the least busy CPU group within the
1071 static struct sched_group
*
1072 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
, int this_cpu
)
1074 struct sched_group
*idlest
= NULL
, *this = NULL
, *group
= sd
->groups
;
1075 unsigned long min_load
= ULONG_MAX
, this_load
= 0;
1076 int load_idx
= sd
->forkexec_idx
;
1077 int imbalance
= 100 + (sd
->imbalance_pct
-100)/2;
1080 unsigned long load
, avg_load
;
1084 /* Skip over this group if it has no CPUs allowed */
1085 if (!cpus_intersects(group
->cpumask
, p
->cpus_allowed
))
1088 local_group
= cpu_isset(this_cpu
, group
->cpumask
);
1090 /* Tally up the load of all CPUs in the group */
1093 for_each_cpu_mask(i
, group
->cpumask
) {
1094 /* Bias balancing toward cpus of our domain */
1096 load
= source_load(i
, load_idx
);
1098 load
= target_load(i
, load_idx
);
1103 /* Adjust by relative CPU power of the group */
1104 avg_load
= (avg_load
* SCHED_LOAD_SCALE
) / group
->cpu_power
;
1107 this_load
= avg_load
;
1109 } else if (avg_load
< min_load
) {
1110 min_load
= avg_load
;
1114 group
= group
->next
;
1115 } while (group
!= sd
->groups
);
1117 if (!idlest
|| 100*this_load
< imbalance
*min_load
)
1123 * find_idlest_queue - find the idlest runqueue among the cpus in group.
1126 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
1129 unsigned long load
, min_load
= ULONG_MAX
;
1133 /* Traverse only the allowed CPUs */
1134 cpus_and(tmp
, group
->cpumask
, p
->cpus_allowed
);
1136 for_each_cpu_mask(i
, tmp
) {
1137 load
= weighted_cpuload(i
);
1139 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
1149 * sched_balance_self: balance the current task (running on cpu) in domains
1150 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
1153 * Balance, ie. select the least loaded group.
1155 * Returns the target CPU number, or the same CPU if no balancing is needed.
1157 * preempt must be disabled.
1159 static int sched_balance_self(int cpu
, int flag
)
1161 struct task_struct
*t
= current
;
1162 struct sched_domain
*tmp
, *sd
= NULL
;
1164 for_each_domain(cpu
, tmp
) {
1165 if (tmp
->flags
& flag
)
1171 struct sched_group
*group
;
1176 group
= find_idlest_group(sd
, t
, cpu
);
1180 new_cpu
= find_idlest_cpu(group
, t
, cpu
);
1181 if (new_cpu
== -1 || new_cpu
== cpu
)
1184 /* Now try balancing at a lower domain level */
1188 weight
= cpus_weight(span
);
1189 for_each_domain(cpu
, tmp
) {
1190 if (weight
<= cpus_weight(tmp
->span
))
1192 if (tmp
->flags
& flag
)
1195 /* while loop will break here if sd == NULL */
1201 #endif /* CONFIG_SMP */
1204 * wake_idle() will wake a task on an idle cpu if task->cpu is
1205 * not idle and an idle cpu is available. The span of cpus to
1206 * search starts with cpus closest then further out as needed,
1207 * so we always favor a closer, idle cpu.
1209 * Returns the CPU we should wake onto.
1211 #if defined(ARCH_HAS_SCHED_WAKE_IDLE)
1212 static int wake_idle(int cpu
, task_t
*p
)
1215 struct sched_domain
*sd
;
1221 for_each_domain(cpu
, sd
) {
1222 if (sd
->flags
& SD_WAKE_IDLE
) {
1223 cpus_and(tmp
, sd
->span
, p
->cpus_allowed
);
1224 for_each_cpu_mask(i
, tmp
) {
1235 static inline int wake_idle(int cpu
, task_t
*p
)
1242 * try_to_wake_up - wake up a thread
1243 * @p: the to-be-woken-up thread
1244 * @state: the mask of task states that can be woken
1245 * @sync: do a synchronous wakeup?
1247 * Put it on the run-queue if it's not already there. The "current"
1248 * thread is always on the run-queue (except when the actual
1249 * re-schedule is in progress), and as such you're allowed to do
1250 * the simpler "current->state = TASK_RUNNING" to mark yourself
1251 * runnable without the overhead of this.
1253 * returns failure only if the task is already active.
1255 static int try_to_wake_up(task_t
*p
, unsigned int state
, int sync
)
1257 int cpu
, this_cpu
, success
= 0;
1258 unsigned long flags
;
1262 unsigned long load
, this_load
;
1263 struct sched_domain
*sd
, *this_sd
= NULL
;
1267 rq
= task_rq_lock(p
, &flags
);
1268 old_state
= p
->state
;
1269 if (!(old_state
& state
))
1276 this_cpu
= smp_processor_id();
1279 if (unlikely(task_running(rq
, p
)))
1284 schedstat_inc(rq
, ttwu_cnt
);
1285 if (cpu
== this_cpu
) {
1286 schedstat_inc(rq
, ttwu_local
);
1290 for_each_domain(this_cpu
, sd
) {
1291 if (cpu_isset(cpu
, sd
->span
)) {
1292 schedstat_inc(sd
, ttwu_wake_remote
);
1298 if (unlikely(!cpu_isset(this_cpu
, p
->cpus_allowed
)))
1302 * Check for affine wakeup and passive balancing possibilities.
1305 int idx
= this_sd
->wake_idx
;
1306 unsigned int imbalance
;
1308 imbalance
= 100 + (this_sd
->imbalance_pct
- 100) / 2;
1310 load
= source_load(cpu
, idx
);
1311 this_load
= target_load(this_cpu
, idx
);
1313 new_cpu
= this_cpu
; /* Wake to this CPU if we can */
1315 if (this_sd
->flags
& SD_WAKE_AFFINE
) {
1316 unsigned long tl
= this_load
;
1317 unsigned long tl_per_task
= cpu_avg_load_per_task(this_cpu
);
1320 * If sync wakeup then subtract the (maximum possible)
1321 * effect of the currently running task from the load
1322 * of the current CPU:
1325 tl
-= current
->load_weight
;
1328 tl
+ target_load(cpu
, idx
) <= tl_per_task
) ||
1329 100*(tl
+ p
->load_weight
) <= imbalance
*load
) {
1331 * This domain has SD_WAKE_AFFINE and
1332 * p is cache cold in this domain, and
1333 * there is no bad imbalance.
1335 schedstat_inc(this_sd
, ttwu_move_affine
);
1341 * Start passive balancing when half the imbalance_pct
1344 if (this_sd
->flags
& SD_WAKE_BALANCE
) {
1345 if (imbalance
*this_load
<= 100*load
) {
1346 schedstat_inc(this_sd
, ttwu_move_balance
);
1352 new_cpu
= cpu
; /* Could not wake to this_cpu. Wake to cpu instead */
1354 new_cpu
= wake_idle(new_cpu
, p
);
1355 if (new_cpu
!= cpu
) {
1356 set_task_cpu(p
, new_cpu
);
1357 task_rq_unlock(rq
, &flags
);
1358 /* might preempt at this point */
1359 rq
= task_rq_lock(p
, &flags
);
1360 old_state
= p
->state
;
1361 if (!(old_state
& state
))
1366 this_cpu
= smp_processor_id();
1371 #endif /* CONFIG_SMP */
1372 if (old_state
== TASK_UNINTERRUPTIBLE
) {
1373 rq
->nr_uninterruptible
--;
1375 * Tasks on involuntary sleep don't earn
1376 * sleep_avg beyond just interactive state.
1378 p
->sleep_type
= SLEEP_NONINTERACTIVE
;
1382 * Tasks that have marked their sleep as noninteractive get
1383 * woken up with their sleep average not weighted in an
1386 if (old_state
& TASK_NONINTERACTIVE
)
1387 p
->sleep_type
= SLEEP_NONINTERACTIVE
;
1390 activate_task(p
, rq
, cpu
== this_cpu
);
1392 * Sync wakeups (i.e. those types of wakeups where the waker
1393 * has indicated that it will leave the CPU in short order)
1394 * don't trigger a preemption, if the woken up task will run on
1395 * this cpu. (in this case the 'I will reschedule' promise of
1396 * the waker guarantees that the freshly woken up task is going
1397 * to be considered on this CPU.)
1399 if (!sync
|| cpu
!= this_cpu
) {
1400 if (TASK_PREEMPTS_CURR(p
, rq
))
1401 resched_task(rq
->curr
);
1406 p
->state
= TASK_RUNNING
;
1408 task_rq_unlock(rq
, &flags
);
1413 int fastcall
wake_up_process(task_t
*p
)
1415 return try_to_wake_up(p
, TASK_STOPPED
| TASK_TRACED
|
1416 TASK_INTERRUPTIBLE
| TASK_UNINTERRUPTIBLE
, 0);
1419 EXPORT_SYMBOL(wake_up_process
);
1421 int fastcall
wake_up_state(task_t
*p
, unsigned int state
)
1423 return try_to_wake_up(p
, state
, 0);
1427 * Perform scheduler related setup for a newly forked process p.
1428 * p is forked by current.
1430 void fastcall
sched_fork(task_t
*p
, int clone_flags
)
1432 int cpu
= get_cpu();
1435 cpu
= sched_balance_self(cpu
, SD_BALANCE_FORK
);
1437 set_task_cpu(p
, cpu
);
1440 * We mark the process as running here, but have not actually
1441 * inserted it onto the runqueue yet. This guarantees that
1442 * nobody will actually run it, and a signal or other external
1443 * event cannot wake it up and insert it on the runqueue either.
1445 p
->state
= TASK_RUNNING
;
1446 INIT_LIST_HEAD(&p
->run_list
);
1448 #ifdef CONFIG_SCHEDSTATS
1449 memset(&p
->sched_info
, 0, sizeof(p
->sched_info
));
1451 #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
1454 #ifdef CONFIG_PREEMPT
1455 /* Want to start with kernel preemption disabled. */
1456 task_thread_info(p
)->preempt_count
= 1;
1459 * Share the timeslice between parent and child, thus the
1460 * total amount of pending timeslices in the system doesn't change,
1461 * resulting in more scheduling fairness.
1463 local_irq_disable();
1464 p
->time_slice
= (current
->time_slice
+ 1) >> 1;
1466 * The remainder of the first timeslice might be recovered by
1467 * the parent if the child exits early enough.
1469 p
->first_time_slice
= 1;
1470 current
->time_slice
>>= 1;
1471 p
->timestamp
= sched_clock();
1472 if (unlikely(!current
->time_slice
)) {
1474 * This case is rare, it happens when the parent has only
1475 * a single jiffy left from its timeslice. Taking the
1476 * runqueue lock is not a problem.
1478 current
->time_slice
= 1;
1486 * wake_up_new_task - wake up a newly created task for the first time.
1488 * This function will do some initial scheduler statistics housekeeping
1489 * that must be done for every newly created context, then puts the task
1490 * on the runqueue and wakes it.
1492 void fastcall
wake_up_new_task(task_t
*p
, unsigned long clone_flags
)
1494 unsigned long flags
;
1496 runqueue_t
*rq
, *this_rq
;
1498 rq
= task_rq_lock(p
, &flags
);
1499 BUG_ON(p
->state
!= TASK_RUNNING
);
1500 this_cpu
= smp_processor_id();
1504 * We decrease the sleep average of forking parents
1505 * and children as well, to keep max-interactive tasks
1506 * from forking tasks that are max-interactive. The parent
1507 * (current) is done further down, under its lock.
1509 p
->sleep_avg
= JIFFIES_TO_NS(CURRENT_BONUS(p
) *
1510 CHILD_PENALTY
/ 100 * MAX_SLEEP_AVG
/ MAX_BONUS
);
1512 p
->prio
= effective_prio(p
);
1514 if (likely(cpu
== this_cpu
)) {
1515 if (!(clone_flags
& CLONE_VM
)) {
1517 * The VM isn't cloned, so we're in a good position to
1518 * do child-runs-first in anticipation of an exec. This
1519 * usually avoids a lot of COW overhead.
1521 if (unlikely(!current
->array
))
1522 __activate_task(p
, rq
);
1524 p
->prio
= current
->prio
;
1525 list_add_tail(&p
->run_list
, ¤t
->run_list
);
1526 p
->array
= current
->array
;
1527 p
->array
->nr_active
++;
1528 inc_nr_running(p
, rq
);
1532 /* Run child last */
1533 __activate_task(p
, rq
);
1535 * We skip the following code due to cpu == this_cpu
1537 * task_rq_unlock(rq, &flags);
1538 * this_rq = task_rq_lock(current, &flags);
1542 this_rq
= cpu_rq(this_cpu
);
1545 * Not the local CPU - must adjust timestamp. This should
1546 * get optimised away in the !CONFIG_SMP case.
1548 p
->timestamp
= (p
->timestamp
- this_rq
->timestamp_last_tick
)
1549 + rq
->timestamp_last_tick
;
1550 __activate_task(p
, rq
);
1551 if (TASK_PREEMPTS_CURR(p
, rq
))
1552 resched_task(rq
->curr
);
1555 * Parent and child are on different CPUs, now get the
1556 * parent runqueue to update the parent's ->sleep_avg:
1558 task_rq_unlock(rq
, &flags
);
1559 this_rq
= task_rq_lock(current
, &flags
);
1561 current
->sleep_avg
= JIFFIES_TO_NS(CURRENT_BONUS(current
) *
1562 PARENT_PENALTY
/ 100 * MAX_SLEEP_AVG
/ MAX_BONUS
);
1563 task_rq_unlock(this_rq
, &flags
);
1567 * Potentially available exiting-child timeslices are
1568 * retrieved here - this way the parent does not get
1569 * penalized for creating too many threads.
1571 * (this cannot be used to 'generate' timeslices
1572 * artificially, because any timeslice recovered here
1573 * was given away by the parent in the first place.)
1575 void fastcall
sched_exit(task_t
*p
)
1577 unsigned long flags
;
1581 * If the child was a (relative-) CPU hog then decrease
1582 * the sleep_avg of the parent as well.
1584 rq
= task_rq_lock(p
->parent
, &flags
);
1585 if (p
->first_time_slice
&& task_cpu(p
) == task_cpu(p
->parent
)) {
1586 p
->parent
->time_slice
+= p
->time_slice
;
1587 if (unlikely(p
->parent
->time_slice
> task_timeslice(p
)))
1588 p
->parent
->time_slice
= task_timeslice(p
);
1590 if (p
->sleep_avg
< p
->parent
->sleep_avg
)
1591 p
->parent
->sleep_avg
= p
->parent
->sleep_avg
/
1592 (EXIT_WEIGHT
+ 1) * EXIT_WEIGHT
+ p
->sleep_avg
/
1594 task_rq_unlock(rq
, &flags
);
1598 * prepare_task_switch - prepare to switch tasks
1599 * @rq: the runqueue preparing to switch
1600 * @next: the task we are going to switch to.
1602 * This is called with the rq lock held and interrupts off. It must
1603 * be paired with a subsequent finish_task_switch after the context
1606 * prepare_task_switch sets up locking and calls architecture specific
1609 static inline void prepare_task_switch(runqueue_t
*rq
, task_t
*next
)
1611 prepare_lock_switch(rq
, next
);
1612 prepare_arch_switch(next
);
1616 * finish_task_switch - clean up after a task-switch
1617 * @rq: runqueue associated with task-switch
1618 * @prev: the thread we just switched away from.
1620 * finish_task_switch must be called after the context switch, paired
1621 * with a prepare_task_switch call before the context switch.
1622 * finish_task_switch will reconcile locking set up by prepare_task_switch,
1623 * and do any other architecture-specific cleanup actions.
1625 * Note that we may have delayed dropping an mm in context_switch(). If
1626 * so, we finish that here outside of the runqueue lock. (Doing it
1627 * with the lock held can cause deadlocks; see schedule() for
1630 static inline void finish_task_switch(runqueue_t
*rq
, task_t
*prev
)
1631 __releases(rq
->lock
)
1633 struct mm_struct
*mm
= rq
->prev_mm
;
1634 unsigned long prev_task_flags
;
1639 * A task struct has one reference for the use as "current".
1640 * If a task dies, then it sets EXIT_ZOMBIE in tsk->exit_state and
1641 * calls schedule one last time. The schedule call will never return,
1642 * and the scheduled task must drop that reference.
1643 * The test for EXIT_ZOMBIE must occur while the runqueue locks are
1644 * still held, otherwise prev could be scheduled on another cpu, die
1645 * there before we look at prev->state, and then the reference would
1647 * Manfred Spraul <manfred@colorfullife.com>
1649 prev_task_flags
= prev
->flags
;
1650 finish_arch_switch(prev
);
1651 finish_lock_switch(rq
, prev
);
1654 if (unlikely(prev_task_flags
& PF_DEAD
)) {
1656 * Remove function-return probe instances associated with this
1657 * task and put them back on the free list.
1659 kprobe_flush_task(prev
);
1660 put_task_struct(prev
);
1665 * schedule_tail - first thing a freshly forked thread must call.
1666 * @prev: the thread we just switched away from.
1668 asmlinkage
void schedule_tail(task_t
*prev
)
1669 __releases(rq
->lock
)
1671 runqueue_t
*rq
= this_rq();
1672 finish_task_switch(rq
, prev
);
1673 #ifdef __ARCH_WANT_UNLOCKED_CTXSW
1674 /* In this case, finish_task_switch does not reenable preemption */
1677 if (current
->set_child_tid
)
1678 put_user(current
->pid
, current
->set_child_tid
);
1682 * context_switch - switch to the new MM and the new
1683 * thread's register state.
1686 task_t
* context_switch(runqueue_t
*rq
, task_t
*prev
, task_t
*next
)
1688 struct mm_struct
*mm
= next
->mm
;
1689 struct mm_struct
*oldmm
= prev
->active_mm
;
1691 if (unlikely(!mm
)) {
1692 next
->active_mm
= oldmm
;
1693 atomic_inc(&oldmm
->mm_count
);
1694 enter_lazy_tlb(oldmm
, next
);
1696 switch_mm(oldmm
, mm
, next
);
1698 if (unlikely(!prev
->mm
)) {
1699 prev
->active_mm
= NULL
;
1700 WARN_ON(rq
->prev_mm
);
1701 rq
->prev_mm
= oldmm
;
1704 /* Here we just switch the register state and the stack. */
1705 switch_to(prev
, next
, prev
);
1711 * nr_running, nr_uninterruptible and nr_context_switches:
1713 * externally visible scheduler statistics: current number of runnable
1714 * threads, current number of uninterruptible-sleeping threads, total
1715 * number of context switches performed since bootup.
1717 unsigned long nr_running(void)
1719 unsigned long i
, sum
= 0;
1721 for_each_online_cpu(i
)
1722 sum
+= cpu_rq(i
)->nr_running
;
1727 unsigned long nr_uninterruptible(void)
1729 unsigned long i
, sum
= 0;
1731 for_each_possible_cpu(i
)
1732 sum
+= cpu_rq(i
)->nr_uninterruptible
;
1735 * Since we read the counters lockless, it might be slightly
1736 * inaccurate. Do not allow it to go below zero though:
1738 if (unlikely((long)sum
< 0))
1744 unsigned long long nr_context_switches(void)
1747 unsigned long long sum
= 0;
1749 for_each_possible_cpu(i
)
1750 sum
+= cpu_rq(i
)->nr_switches
;
1755 unsigned long nr_iowait(void)
1757 unsigned long i
, sum
= 0;
1759 for_each_possible_cpu(i
)
1760 sum
+= atomic_read(&cpu_rq(i
)->nr_iowait
);
1765 unsigned long nr_active(void)
1767 unsigned long i
, running
= 0, uninterruptible
= 0;
1769 for_each_online_cpu(i
) {
1770 running
+= cpu_rq(i
)->nr_running
;
1771 uninterruptible
+= cpu_rq(i
)->nr_uninterruptible
;
1774 if (unlikely((long)uninterruptible
< 0))
1775 uninterruptible
= 0;
1777 return running
+ uninterruptible
;
1783 * double_rq_lock - safely lock two runqueues
1785 * Note this does not disable interrupts like task_rq_lock,
1786 * you need to do so manually before calling.
1788 static void double_rq_lock(runqueue_t
*rq1
, runqueue_t
*rq2
)
1789 __acquires(rq1
->lock
)
1790 __acquires(rq2
->lock
)
1793 spin_lock(&rq1
->lock
);
1794 __acquire(rq2
->lock
); /* Fake it out ;) */
1797 spin_lock(&rq1
->lock
);
1798 spin_lock(&rq2
->lock
);
1800 spin_lock(&rq2
->lock
);
1801 spin_lock(&rq1
->lock
);
1807 * double_rq_unlock - safely unlock two runqueues
1809 * Note this does not restore interrupts like task_rq_unlock,
1810 * you need to do so manually after calling.
1812 static void double_rq_unlock(runqueue_t
*rq1
, runqueue_t
*rq2
)
1813 __releases(rq1
->lock
)
1814 __releases(rq2
->lock
)
1816 spin_unlock(&rq1
->lock
);
1818 spin_unlock(&rq2
->lock
);
1820 __release(rq2
->lock
);
1824 * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
1826 static void double_lock_balance(runqueue_t
*this_rq
, runqueue_t
*busiest
)
1827 __releases(this_rq
->lock
)
1828 __acquires(busiest
->lock
)
1829 __acquires(this_rq
->lock
)
1831 if (unlikely(!spin_trylock(&busiest
->lock
))) {
1832 if (busiest
< this_rq
) {
1833 spin_unlock(&this_rq
->lock
);
1834 spin_lock(&busiest
->lock
);
1835 spin_lock(&this_rq
->lock
);
1837 spin_lock(&busiest
->lock
);
1842 * If dest_cpu is allowed for this process, migrate the task to it.
1843 * This is accomplished by forcing the cpu_allowed mask to only
1844 * allow dest_cpu, which will force the cpu onto dest_cpu. Then
1845 * the cpu_allowed mask is restored.
1847 static void sched_migrate_task(task_t
*p
, int dest_cpu
)
1849 migration_req_t req
;
1851 unsigned long flags
;
1853 rq
= task_rq_lock(p
, &flags
);
1854 if (!cpu_isset(dest_cpu
, p
->cpus_allowed
)
1855 || unlikely(cpu_is_offline(dest_cpu
)))
1858 /* force the process onto the specified CPU */
1859 if (migrate_task(p
, dest_cpu
, &req
)) {
1860 /* Need to wait for migration thread (might exit: take ref). */
1861 struct task_struct
*mt
= rq
->migration_thread
;
1862 get_task_struct(mt
);
1863 task_rq_unlock(rq
, &flags
);
1864 wake_up_process(mt
);
1865 put_task_struct(mt
);
1866 wait_for_completion(&req
.done
);
1870 task_rq_unlock(rq
, &flags
);
1874 * sched_exec - execve() is a valuable balancing opportunity, because at
1875 * this point the task has the smallest effective memory and cache footprint.
1877 void sched_exec(void)
1879 int new_cpu
, this_cpu
= get_cpu();
1880 new_cpu
= sched_balance_self(this_cpu
, SD_BALANCE_EXEC
);
1882 if (new_cpu
!= this_cpu
)
1883 sched_migrate_task(current
, new_cpu
);
1887 * pull_task - move a task from a remote runqueue to the local runqueue.
1888 * Both runqueues must be locked.
1891 void pull_task(runqueue_t
*src_rq
, prio_array_t
*src_array
, task_t
*p
,
1892 runqueue_t
*this_rq
, prio_array_t
*this_array
, int this_cpu
)
1894 dequeue_task(p
, src_array
);
1895 dec_nr_running(p
, src_rq
);
1896 set_task_cpu(p
, this_cpu
);
1897 inc_nr_running(p
, this_rq
);
1898 enqueue_task(p
, this_array
);
1899 p
->timestamp
= (p
->timestamp
- src_rq
->timestamp_last_tick
)
1900 + this_rq
->timestamp_last_tick
;
1902 * Note that idle threads have a prio of MAX_PRIO, for this test
1903 * to be always true for them.
1905 if (TASK_PREEMPTS_CURR(p
, this_rq
))
1906 resched_task(this_rq
->curr
);
1910 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
1913 int can_migrate_task(task_t
*p
, runqueue_t
*rq
, int this_cpu
,
1914 struct sched_domain
*sd
, enum idle_type idle
,
1918 * We do not migrate tasks that are:
1919 * 1) running (obviously), or
1920 * 2) cannot be migrated to this CPU due to cpus_allowed, or
1921 * 3) are cache-hot on their current CPU.
1923 if (!cpu_isset(this_cpu
, p
->cpus_allowed
))
1927 if (task_running(rq
, p
))
1931 * Aggressive migration if:
1932 * 1) task is cache cold, or
1933 * 2) too many balance attempts have failed.
1936 if (sd
->nr_balance_failed
> sd
->cache_nice_tries
)
1939 if (task_hot(p
, rq
->timestamp_last_tick
, sd
))
1944 #define rq_best_prio(rq) min((rq)->curr->prio, (rq)->best_expired_prio)
1946 * move_tasks tries to move up to max_nr_move tasks and max_load_move weighted
1947 * load from busiest to this_rq, as part of a balancing operation within
1948 * "domain". Returns the number of tasks moved.
1950 * Called with both runqueues locked.
1952 static int move_tasks(runqueue_t
*this_rq
, int this_cpu
, runqueue_t
*busiest
,
1953 unsigned long max_nr_move
, unsigned long max_load_move
,
1954 struct sched_domain
*sd
, enum idle_type idle
,
1957 prio_array_t
*array
, *dst_array
;
1958 struct list_head
*head
, *curr
;
1959 int idx
, pulled
= 0, pinned
= 0, this_best_prio
, busiest_best_prio
;
1960 int busiest_best_prio_seen
;
1961 int skip_for_load
; /* skip the task based on weighted load issues */
1965 if (max_nr_move
== 0 || max_load_move
== 0)
1968 rem_load_move
= max_load_move
;
1970 this_best_prio
= rq_best_prio(this_rq
);
1971 busiest_best_prio
= rq_best_prio(busiest
);
1973 * Enable handling of the case where there is more than one task
1974 * with the best priority. If the current running task is one
1975 * of those with prio==busiest_best_prio we know it won't be moved
1976 * and therefore it's safe to override the skip (based on load) of
1977 * any task we find with that prio.
1979 busiest_best_prio_seen
= busiest_best_prio
== busiest
->curr
->prio
;
1982 * We first consider expired tasks. Those will likely not be
1983 * executed in the near future, and they are most likely to
1984 * be cache-cold, thus switching CPUs has the least effect
1987 if (busiest
->expired
->nr_active
) {
1988 array
= busiest
->expired
;
1989 dst_array
= this_rq
->expired
;
1991 array
= busiest
->active
;
1992 dst_array
= this_rq
->active
;
1996 /* Start searching at priority 0: */
2000 idx
= sched_find_first_bit(array
->bitmap
);
2002 idx
= find_next_bit(array
->bitmap
, MAX_PRIO
, idx
);
2003 if (idx
>= MAX_PRIO
) {
2004 if (array
== busiest
->expired
&& busiest
->active
->nr_active
) {
2005 array
= busiest
->active
;
2006 dst_array
= this_rq
->active
;
2012 head
= array
->queue
+ idx
;
2015 tmp
= list_entry(curr
, task_t
, run_list
);
2020 * To help distribute high priority tasks accross CPUs we don't
2021 * skip a task if it will be the highest priority task (i.e. smallest
2022 * prio value) on its new queue regardless of its load weight
2024 skip_for_load
= tmp
->load_weight
> rem_load_move
;
2025 if (skip_for_load
&& idx
< this_best_prio
)
2026 skip_for_load
= !busiest_best_prio_seen
&& idx
== busiest_best_prio
;
2027 if (skip_for_load
||
2028 !can_migrate_task(tmp
, busiest
, this_cpu
, sd
, idle
, &pinned
)) {
2029 busiest_best_prio_seen
|= idx
== busiest_best_prio
;
2036 #ifdef CONFIG_SCHEDSTATS
2037 if (task_hot(tmp
, busiest
->timestamp_last_tick
, sd
))
2038 schedstat_inc(sd
, lb_hot_gained
[idle
]);
2041 pull_task(busiest
, array
, tmp
, this_rq
, dst_array
, this_cpu
);
2043 rem_load_move
-= tmp
->load_weight
;
2046 * We only want to steal up to the prescribed number of tasks
2047 * and the prescribed amount of weighted load.
2049 if (pulled
< max_nr_move
&& rem_load_move
> 0) {
2050 if (idx
< this_best_prio
)
2051 this_best_prio
= idx
;
2059 * Right now, this is the only place pull_task() is called,
2060 * so we can safely collect pull_task() stats here rather than
2061 * inside pull_task().
2063 schedstat_add(sd
, lb_gained
[idle
], pulled
);
2066 *all_pinned
= pinned
;
2071 * find_busiest_group finds and returns the busiest CPU group within the
2072 * domain. It calculates and returns the amount of weighted load which should be
2073 * moved to restore balance via the imbalance parameter.
2075 static struct sched_group
*
2076 find_busiest_group(struct sched_domain
*sd
, int this_cpu
,
2077 unsigned long *imbalance
, enum idle_type idle
, int *sd_idle
)
2079 struct sched_group
*busiest
= NULL
, *this = NULL
, *group
= sd
->groups
;
2080 unsigned long max_load
, avg_load
, total_load
, this_load
, total_pwr
;
2081 unsigned long max_pull
;
2082 unsigned long busiest_load_per_task
, busiest_nr_running
;
2083 unsigned long this_load_per_task
, this_nr_running
;
2086 max_load
= this_load
= total_load
= total_pwr
= 0;
2087 busiest_load_per_task
= busiest_nr_running
= 0;
2088 this_load_per_task
= this_nr_running
= 0;
2089 if (idle
== NOT_IDLE
)
2090 load_idx
= sd
->busy_idx
;
2091 else if (idle
== NEWLY_IDLE
)
2092 load_idx
= sd
->newidle_idx
;
2094 load_idx
= sd
->idle_idx
;
2100 unsigned long sum_nr_running
, sum_weighted_load
;
2102 local_group
= cpu_isset(this_cpu
, group
->cpumask
);
2104 /* Tally up the load of all CPUs in the group */
2105 sum_weighted_load
= sum_nr_running
= avg_load
= 0;
2107 for_each_cpu_mask(i
, group
->cpumask
) {
2108 runqueue_t
*rq
= cpu_rq(i
);
2110 if (*sd_idle
&& !idle_cpu(i
))
2113 /* Bias balancing toward cpus of our domain */
2115 load
= target_load(i
, load_idx
);
2117 load
= source_load(i
, load_idx
);
2120 sum_nr_running
+= rq
->nr_running
;
2121 sum_weighted_load
+= rq
->raw_weighted_load
;
2124 total_load
+= avg_load
;
2125 total_pwr
+= group
->cpu_power
;
2127 /* Adjust by relative CPU power of the group */
2128 avg_load
= (avg_load
* SCHED_LOAD_SCALE
) / group
->cpu_power
;
2131 this_load
= avg_load
;
2133 this_nr_running
= sum_nr_running
;
2134 this_load_per_task
= sum_weighted_load
;
2135 } else if (avg_load
> max_load
&&
2136 sum_nr_running
> group
->cpu_power
/ SCHED_LOAD_SCALE
) {
2137 max_load
= avg_load
;
2139 busiest_nr_running
= sum_nr_running
;
2140 busiest_load_per_task
= sum_weighted_load
;
2142 group
= group
->next
;
2143 } while (group
!= sd
->groups
);
2145 if (!busiest
|| this_load
>= max_load
|| busiest_nr_running
== 0)
2148 avg_load
= (SCHED_LOAD_SCALE
* total_load
) / total_pwr
;
2150 if (this_load
>= avg_load
||
2151 100*max_load
<= sd
->imbalance_pct
*this_load
)
2154 busiest_load_per_task
/= busiest_nr_running
;
2156 * We're trying to get all the cpus to the average_load, so we don't
2157 * want to push ourselves above the average load, nor do we wish to
2158 * reduce the max loaded cpu below the average load, as either of these
2159 * actions would just result in more rebalancing later, and ping-pong
2160 * tasks around. Thus we look for the minimum possible imbalance.
2161 * Negative imbalances (*we* are more loaded than anyone else) will
2162 * be counted as no imbalance for these purposes -- we can't fix that
2163 * by pulling tasks to us. Be careful of negative numbers as they'll
2164 * appear as very large values with unsigned longs.
2166 if (max_load
<= busiest_load_per_task
)
2170 * In the presence of smp nice balancing, certain scenarios can have
2171 * max load less than avg load(as we skip the groups at or below
2172 * its cpu_power, while calculating max_load..)
2174 if (max_load
< avg_load
) {
2176 goto small_imbalance
;
2179 /* Don't want to pull so many tasks that a group would go idle */
2180 max_pull
= min(max_load
- avg_load
, max_load
- busiest_load_per_task
);
2182 /* How much load to actually move to equalise the imbalance */
2183 *imbalance
= min(max_pull
* busiest
->cpu_power
,
2184 (avg_load
- this_load
) * this->cpu_power
)
2188 * if *imbalance is less than the average load per runnable task
2189 * there is no gaurantee that any tasks will be moved so we'll have
2190 * a think about bumping its value to force at least one task to be
2193 if (*imbalance
< busiest_load_per_task
) {
2194 unsigned long pwr_now
, pwr_move
;
2199 pwr_move
= pwr_now
= 0;
2201 if (this_nr_running
) {
2202 this_load_per_task
/= this_nr_running
;
2203 if (busiest_load_per_task
> this_load_per_task
)
2206 this_load_per_task
= SCHED_LOAD_SCALE
;
2208 if (max_load
- this_load
>= busiest_load_per_task
* imbn
) {
2209 *imbalance
= busiest_load_per_task
;
2214 * OK, we don't have enough imbalance to justify moving tasks,
2215 * however we may be able to increase total CPU power used by
2219 pwr_now
+= busiest
->cpu_power
*
2220 min(busiest_load_per_task
, max_load
);
2221 pwr_now
+= this->cpu_power
*
2222 min(this_load_per_task
, this_load
);
2223 pwr_now
/= SCHED_LOAD_SCALE
;
2225 /* Amount of load we'd subtract */
2226 tmp
= busiest_load_per_task
*SCHED_LOAD_SCALE
/busiest
->cpu_power
;
2228 pwr_move
+= busiest
->cpu_power
*
2229 min(busiest_load_per_task
, max_load
- tmp
);
2231 /* Amount of load we'd add */
2232 if (max_load
*busiest
->cpu_power
<
2233 busiest_load_per_task
*SCHED_LOAD_SCALE
)
2234 tmp
= max_load
*busiest
->cpu_power
/this->cpu_power
;
2236 tmp
= busiest_load_per_task
*SCHED_LOAD_SCALE
/this->cpu_power
;
2237 pwr_move
+= this->cpu_power
*min(this_load_per_task
, this_load
+ tmp
);
2238 pwr_move
/= SCHED_LOAD_SCALE
;
2240 /* Move if we gain throughput */
2241 if (pwr_move
<= pwr_now
)
2244 *imbalance
= busiest_load_per_task
;
2256 * find_busiest_queue - find the busiest runqueue among the cpus in group.
2258 static runqueue_t
*find_busiest_queue(struct sched_group
*group
,
2259 enum idle_type idle
, unsigned long imbalance
)
2261 unsigned long max_load
= 0;
2262 runqueue_t
*busiest
= NULL
, *rqi
;
2265 for_each_cpu_mask(i
, group
->cpumask
) {
2268 if (rqi
->nr_running
== 1 && rqi
->raw_weighted_load
> imbalance
)
2271 if (rqi
->raw_weighted_load
> max_load
) {
2272 max_load
= rqi
->raw_weighted_load
;
2281 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
2282 * so long as it is large enough.
2284 #define MAX_PINNED_INTERVAL 512
2286 #define minus_1_or_zero(n) ((n) > 0 ? (n) - 1 : 0)
2288 * Check this_cpu to ensure it is balanced within domain. Attempt to move
2289 * tasks if there is an imbalance.
2291 * Called with this_rq unlocked.
2293 static int load_balance(int this_cpu
, runqueue_t
*this_rq
,
2294 struct sched_domain
*sd
, enum idle_type idle
)
2296 struct sched_group
*group
;
2297 runqueue_t
*busiest
;
2298 unsigned long imbalance
;
2299 int nr_moved
, all_pinned
= 0;
2300 int active_balance
= 0;
2303 if (idle
!= NOT_IDLE
&& sd
->flags
& SD_SHARE_CPUPOWER
)
2306 schedstat_inc(sd
, lb_cnt
[idle
]);
2308 group
= find_busiest_group(sd
, this_cpu
, &imbalance
, idle
, &sd_idle
);
2310 schedstat_inc(sd
, lb_nobusyg
[idle
]);
2314 busiest
= find_busiest_queue(group
, idle
, imbalance
);
2316 schedstat_inc(sd
, lb_nobusyq
[idle
]);
2320 BUG_ON(busiest
== this_rq
);
2322 schedstat_add(sd
, lb_imbalance
[idle
], imbalance
);
2325 if (busiest
->nr_running
> 1) {
2327 * Attempt to move tasks. If find_busiest_group has found
2328 * an imbalance but busiest->nr_running <= 1, the group is
2329 * still unbalanced. nr_moved simply stays zero, so it is
2330 * correctly treated as an imbalance.
2332 double_rq_lock(this_rq
, busiest
);
2333 nr_moved
= move_tasks(this_rq
, this_cpu
, busiest
,
2334 minus_1_or_zero(busiest
->nr_running
),
2335 imbalance
, sd
, idle
, &all_pinned
);
2336 double_rq_unlock(this_rq
, busiest
);
2338 /* All tasks on this runqueue were pinned by CPU affinity */
2339 if (unlikely(all_pinned
))
2344 schedstat_inc(sd
, lb_failed
[idle
]);
2345 sd
->nr_balance_failed
++;
2347 if (unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2)) {
2349 spin_lock(&busiest
->lock
);
2351 /* don't kick the migration_thread, if the curr
2352 * task on busiest cpu can't be moved to this_cpu
2354 if (!cpu_isset(this_cpu
, busiest
->curr
->cpus_allowed
)) {
2355 spin_unlock(&busiest
->lock
);
2357 goto out_one_pinned
;
2360 if (!busiest
->active_balance
) {
2361 busiest
->active_balance
= 1;
2362 busiest
->push_cpu
= this_cpu
;
2365 spin_unlock(&busiest
->lock
);
2367 wake_up_process(busiest
->migration_thread
);
2370 * We've kicked active balancing, reset the failure
2373 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
2376 sd
->nr_balance_failed
= 0;
2378 if (likely(!active_balance
)) {
2379 /* We were unbalanced, so reset the balancing interval */
2380 sd
->balance_interval
= sd
->min_interval
;
2383 * If we've begun active balancing, start to back off. This
2384 * case may not be covered by the all_pinned logic if there
2385 * is only 1 task on the busy runqueue (because we don't call
2388 if (sd
->balance_interval
< sd
->max_interval
)
2389 sd
->balance_interval
*= 2;
2392 if (!nr_moved
&& !sd_idle
&& sd
->flags
& SD_SHARE_CPUPOWER
)
2397 schedstat_inc(sd
, lb_balanced
[idle
]);
2399 sd
->nr_balance_failed
= 0;
2402 /* tune up the balancing interval */
2403 if ((all_pinned
&& sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
2404 (sd
->balance_interval
< sd
->max_interval
))
2405 sd
->balance_interval
*= 2;
2407 if (!sd_idle
&& sd
->flags
& SD_SHARE_CPUPOWER
)
2413 * Check this_cpu to ensure it is balanced within domain. Attempt to move
2414 * tasks if there is an imbalance.
2416 * Called from schedule when this_rq is about to become idle (NEWLY_IDLE).
2417 * this_rq is locked.
2419 static int load_balance_newidle(int this_cpu
, runqueue_t
*this_rq
,
2420 struct sched_domain
*sd
)
2422 struct sched_group
*group
;
2423 runqueue_t
*busiest
= NULL
;
2424 unsigned long imbalance
;
2428 if (sd
->flags
& SD_SHARE_CPUPOWER
)
2431 schedstat_inc(sd
, lb_cnt
[NEWLY_IDLE
]);
2432 group
= find_busiest_group(sd
, this_cpu
, &imbalance
, NEWLY_IDLE
, &sd_idle
);
2434 schedstat_inc(sd
, lb_nobusyg
[NEWLY_IDLE
]);
2438 busiest
= find_busiest_queue(group
, NEWLY_IDLE
, imbalance
);
2440 schedstat_inc(sd
, lb_nobusyq
[NEWLY_IDLE
]);
2444 BUG_ON(busiest
== this_rq
);
2446 schedstat_add(sd
, lb_imbalance
[NEWLY_IDLE
], imbalance
);
2449 if (busiest
->nr_running
> 1) {
2450 /* Attempt to move tasks */
2451 double_lock_balance(this_rq
, busiest
);
2452 nr_moved
= move_tasks(this_rq
, this_cpu
, busiest
,
2453 minus_1_or_zero(busiest
->nr_running
),
2454 imbalance
, sd
, NEWLY_IDLE
, NULL
);
2455 spin_unlock(&busiest
->lock
);
2459 schedstat_inc(sd
, lb_failed
[NEWLY_IDLE
]);
2460 if (!sd_idle
&& sd
->flags
& SD_SHARE_CPUPOWER
)
2463 sd
->nr_balance_failed
= 0;
2468 schedstat_inc(sd
, lb_balanced
[NEWLY_IDLE
]);
2469 if (!sd_idle
&& sd
->flags
& SD_SHARE_CPUPOWER
)
2471 sd
->nr_balance_failed
= 0;
2476 * idle_balance is called by schedule() if this_cpu is about to become
2477 * idle. Attempts to pull tasks from other CPUs.
2479 static void idle_balance(int this_cpu
, runqueue_t
*this_rq
)
2481 struct sched_domain
*sd
;
2483 for_each_domain(this_cpu
, sd
) {
2484 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
2485 if (load_balance_newidle(this_cpu
, this_rq
, sd
)) {
2486 /* We've pulled tasks over so stop searching */
2494 * active_load_balance is run by migration threads. It pushes running tasks
2495 * off the busiest CPU onto idle CPUs. It requires at least 1 task to be
2496 * running on each physical CPU where possible, and avoids physical /
2497 * logical imbalances.
2499 * Called with busiest_rq locked.
2501 static void active_load_balance(runqueue_t
*busiest_rq
, int busiest_cpu
)
2503 struct sched_domain
*sd
;
2504 runqueue_t
*target_rq
;
2505 int target_cpu
= busiest_rq
->push_cpu
;
2507 if (busiest_rq
->nr_running
<= 1)
2508 /* no task to move */
2511 target_rq
= cpu_rq(target_cpu
);
2514 * This condition is "impossible", if it occurs
2515 * we need to fix it. Originally reported by
2516 * Bjorn Helgaas on a 128-cpu setup.
2518 BUG_ON(busiest_rq
== target_rq
);
2520 /* move a task from busiest_rq to target_rq */
2521 double_lock_balance(busiest_rq
, target_rq
);
2523 /* Search for an sd spanning us and the target CPU. */
2524 for_each_domain(target_cpu
, sd
) {
2525 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
2526 cpu_isset(busiest_cpu
, sd
->span
))
2530 if (unlikely(sd
== NULL
))
2533 schedstat_inc(sd
, alb_cnt
);
2535 if (move_tasks(target_rq
, target_cpu
, busiest_rq
, 1,
2536 RTPRIO_TO_LOAD_WEIGHT(100), sd
, SCHED_IDLE
, NULL
))
2537 schedstat_inc(sd
, alb_pushed
);
2539 schedstat_inc(sd
, alb_failed
);
2541 spin_unlock(&target_rq
->lock
);
2545 * rebalance_tick will get called every timer tick, on every CPU.
2547 * It checks each scheduling domain to see if it is due to be balanced,
2548 * and initiates a balancing operation if so.
2550 * Balancing parameters are set up in arch_init_sched_domains.
2553 /* Don't have all balancing operations going off at once */
2554 #define CPU_OFFSET(cpu) (HZ * cpu / NR_CPUS)
2556 static void rebalance_tick(int this_cpu
, runqueue_t
*this_rq
,
2557 enum idle_type idle
)
2559 unsigned long old_load
, this_load
;
2560 unsigned long j
= jiffies
+ CPU_OFFSET(this_cpu
);
2561 struct sched_domain
*sd
;
2564 this_load
= this_rq
->raw_weighted_load
;
2565 /* Update our load */
2566 for (i
= 0; i
< 3; i
++) {
2567 unsigned long new_load
= this_load
;
2569 old_load
= this_rq
->cpu_load
[i
];
2571 * Round up the averaging division if load is increasing. This
2572 * prevents us from getting stuck on 9 if the load is 10, for
2575 if (new_load
> old_load
)
2576 new_load
+= scale
-1;
2577 this_rq
->cpu_load
[i
] = (old_load
*(scale
-1) + new_load
) / scale
;
2580 for_each_domain(this_cpu
, sd
) {
2581 unsigned long interval
;
2583 if (!(sd
->flags
& SD_LOAD_BALANCE
))
2586 interval
= sd
->balance_interval
;
2587 if (idle
!= SCHED_IDLE
)
2588 interval
*= sd
->busy_factor
;
2590 /* scale ms to jiffies */
2591 interval
= msecs_to_jiffies(interval
);
2592 if (unlikely(!interval
))
2595 if (j
- sd
->last_balance
>= interval
) {
2596 if (load_balance(this_cpu
, this_rq
, sd
, idle
)) {
2598 * We've pulled tasks over so either we're no
2599 * longer idle, or one of our SMT siblings is
2604 sd
->last_balance
+= interval
;
2610 * on UP we do not need to balance between CPUs:
2612 static inline void rebalance_tick(int cpu
, runqueue_t
*rq
, enum idle_type idle
)
2615 static inline void idle_balance(int cpu
, runqueue_t
*rq
)
2620 static inline int wake_priority_sleeper(runqueue_t
*rq
)
2623 #ifdef CONFIG_SCHED_SMT
2624 spin_lock(&rq
->lock
);
2626 * If an SMT sibling task has been put to sleep for priority
2627 * reasons reschedule the idle task to see if it can now run.
2629 if (rq
->nr_running
) {
2630 resched_task(rq
->idle
);
2633 spin_unlock(&rq
->lock
);
2638 DEFINE_PER_CPU(struct kernel_stat
, kstat
);
2640 EXPORT_PER_CPU_SYMBOL(kstat
);
2643 * This is called on clock ticks and on context switches.
2644 * Bank in p->sched_time the ns elapsed since the last tick or switch.
2646 static inline void update_cpu_clock(task_t
*p
, runqueue_t
*rq
,
2647 unsigned long long now
)
2649 unsigned long long last
= max(p
->timestamp
, rq
->timestamp_last_tick
);
2650 p
->sched_time
+= now
- last
;
2654 * Return current->sched_time plus any more ns on the sched_clock
2655 * that have not yet been banked.
2657 unsigned long long current_sched_time(const task_t
*tsk
)
2659 unsigned long long ns
;
2660 unsigned long flags
;
2661 local_irq_save(flags
);
2662 ns
= max(tsk
->timestamp
, task_rq(tsk
)->timestamp_last_tick
);
2663 ns
= tsk
->sched_time
+ (sched_clock() - ns
);
2664 local_irq_restore(flags
);
2669 * We place interactive tasks back into the active array, if possible.
2671 * To guarantee that this does not starve expired tasks we ignore the
2672 * interactivity of a task if the first expired task had to wait more
2673 * than a 'reasonable' amount of time. This deadline timeout is
2674 * load-dependent, as the frequency of array switched decreases with
2675 * increasing number of running tasks. We also ignore the interactivity
2676 * if a better static_prio task has expired:
2678 #define EXPIRED_STARVING(rq) \
2679 ((STARVATION_LIMIT && ((rq)->expired_timestamp && \
2680 (jiffies - (rq)->expired_timestamp >= \
2681 STARVATION_LIMIT * ((rq)->nr_running) + 1))) || \
2682 ((rq)->curr->static_prio > (rq)->best_expired_prio))
2685 * Account user cpu time to a process.
2686 * @p: the process that the cpu time gets accounted to
2687 * @hardirq_offset: the offset to subtract from hardirq_count()
2688 * @cputime: the cpu time spent in user space since the last update
2690 void account_user_time(struct task_struct
*p
, cputime_t cputime
)
2692 struct cpu_usage_stat
*cpustat
= &kstat_this_cpu
.cpustat
;
2695 p
->utime
= cputime_add(p
->utime
, cputime
);
2697 /* Add user time to cpustat. */
2698 tmp
= cputime_to_cputime64(cputime
);
2699 if (TASK_NICE(p
) > 0)
2700 cpustat
->nice
= cputime64_add(cpustat
->nice
, tmp
);
2702 cpustat
->user
= cputime64_add(cpustat
->user
, tmp
);
2706 * Account system cpu time to a process.
2707 * @p: the process that the cpu time gets accounted to
2708 * @hardirq_offset: the offset to subtract from hardirq_count()
2709 * @cputime: the cpu time spent in kernel space since the last update
2711 void account_system_time(struct task_struct
*p
, int hardirq_offset
,
2714 struct cpu_usage_stat
*cpustat
= &kstat_this_cpu
.cpustat
;
2715 runqueue_t
*rq
= this_rq();
2718 p
->stime
= cputime_add(p
->stime
, cputime
);
2720 /* Add system time to cpustat. */
2721 tmp
= cputime_to_cputime64(cputime
);
2722 if (hardirq_count() - hardirq_offset
)
2723 cpustat
->irq
= cputime64_add(cpustat
->irq
, tmp
);
2724 else if (softirq_count())
2725 cpustat
->softirq
= cputime64_add(cpustat
->softirq
, tmp
);
2726 else if (p
!= rq
->idle
)
2727 cpustat
->system
= cputime64_add(cpustat
->system
, tmp
);
2728 else if (atomic_read(&rq
->nr_iowait
) > 0)
2729 cpustat
->iowait
= cputime64_add(cpustat
->iowait
, tmp
);
2731 cpustat
->idle
= cputime64_add(cpustat
->idle
, tmp
);
2732 /* Account for system time used */
2733 acct_update_integrals(p
);
2737 * Account for involuntary wait time.
2738 * @p: the process from which the cpu time has been stolen
2739 * @steal: the cpu time spent in involuntary wait
2741 void account_steal_time(struct task_struct
*p
, cputime_t steal
)
2743 struct cpu_usage_stat
*cpustat
= &kstat_this_cpu
.cpustat
;
2744 cputime64_t tmp
= cputime_to_cputime64(steal
);
2745 runqueue_t
*rq
= this_rq();
2747 if (p
== rq
->idle
) {
2748 p
->stime
= cputime_add(p
->stime
, steal
);
2749 if (atomic_read(&rq
->nr_iowait
) > 0)
2750 cpustat
->iowait
= cputime64_add(cpustat
->iowait
, tmp
);
2752 cpustat
->idle
= cputime64_add(cpustat
->idle
, tmp
);
2754 cpustat
->steal
= cputime64_add(cpustat
->steal
, tmp
);
2758 * This function gets called by the timer code, with HZ frequency.
2759 * We call it with interrupts disabled.
2761 * It also gets called by the fork code, when changing the parent's
2764 void scheduler_tick(void)
2766 int cpu
= smp_processor_id();
2767 runqueue_t
*rq
= this_rq();
2768 task_t
*p
= current
;
2769 unsigned long long now
= sched_clock();
2771 update_cpu_clock(p
, rq
, now
);
2773 rq
->timestamp_last_tick
= now
;
2775 if (p
== rq
->idle
) {
2776 if (wake_priority_sleeper(rq
))
2778 rebalance_tick(cpu
, rq
, SCHED_IDLE
);
2782 /* Task might have expired already, but not scheduled off yet */
2783 if (p
->array
!= rq
->active
) {
2784 set_tsk_need_resched(p
);
2787 spin_lock(&rq
->lock
);
2789 * The task was running during this tick - update the
2790 * time slice counter. Note: we do not update a thread's
2791 * priority until it either goes to sleep or uses up its
2792 * timeslice. This makes it possible for interactive tasks
2793 * to use up their timeslices at their highest priority levels.
2797 * RR tasks need a special form of timeslice management.
2798 * FIFO tasks have no timeslices.
2800 if ((p
->policy
== SCHED_RR
) && !--p
->time_slice
) {
2801 p
->time_slice
= task_timeslice(p
);
2802 p
->first_time_slice
= 0;
2803 set_tsk_need_resched(p
);
2805 /* put it at the end of the queue: */
2806 requeue_task(p
, rq
->active
);
2810 if (!--p
->time_slice
) {
2811 dequeue_task(p
, rq
->active
);
2812 set_tsk_need_resched(p
);
2813 p
->prio
= effective_prio(p
);
2814 p
->time_slice
= task_timeslice(p
);
2815 p
->first_time_slice
= 0;
2817 if (!rq
->expired_timestamp
)
2818 rq
->expired_timestamp
= jiffies
;
2819 if (!TASK_INTERACTIVE(p
) || EXPIRED_STARVING(rq
)) {
2820 enqueue_task(p
, rq
->expired
);
2821 if (p
->static_prio
< rq
->best_expired_prio
)
2822 rq
->best_expired_prio
= p
->static_prio
;
2824 enqueue_task(p
, rq
->active
);
2827 * Prevent a too long timeslice allowing a task to monopolize
2828 * the CPU. We do this by splitting up the timeslice into
2831 * Note: this does not mean the task's timeslices expire or
2832 * get lost in any way, they just might be preempted by
2833 * another task of equal priority. (one with higher
2834 * priority would have preempted this task already.) We
2835 * requeue this task to the end of the list on this priority
2836 * level, which is in essence a round-robin of tasks with
2839 * This only applies to tasks in the interactive
2840 * delta range with at least TIMESLICE_GRANULARITY to requeue.
2842 if (TASK_INTERACTIVE(p
) && !((task_timeslice(p
) -
2843 p
->time_slice
) % TIMESLICE_GRANULARITY(p
)) &&
2844 (p
->time_slice
>= TIMESLICE_GRANULARITY(p
)) &&
2845 (p
->array
== rq
->active
)) {
2847 requeue_task(p
, rq
->active
);
2848 set_tsk_need_resched(p
);
2852 spin_unlock(&rq
->lock
);
2854 rebalance_tick(cpu
, rq
, NOT_IDLE
);
2857 #ifdef CONFIG_SCHED_SMT
2858 static inline void wakeup_busy_runqueue(runqueue_t
*rq
)
2860 /* If an SMT runqueue is sleeping due to priority reasons wake it up */
2861 if (rq
->curr
== rq
->idle
&& rq
->nr_running
)
2862 resched_task(rq
->idle
);
2866 * Called with interrupt disabled and this_rq's runqueue locked.
2868 static void wake_sleeping_dependent(int this_cpu
)
2870 struct sched_domain
*tmp
, *sd
= NULL
;
2873 for_each_domain(this_cpu
, tmp
) {
2874 if (tmp
->flags
& SD_SHARE_CPUPOWER
) {
2883 for_each_cpu_mask(i
, sd
->span
) {
2884 runqueue_t
*smt_rq
= cpu_rq(i
);
2888 if (unlikely(!spin_trylock(&smt_rq
->lock
)))
2891 wakeup_busy_runqueue(smt_rq
);
2892 spin_unlock(&smt_rq
->lock
);
2897 * number of 'lost' timeslices this task wont be able to fully
2898 * utilize, if another task runs on a sibling. This models the
2899 * slowdown effect of other tasks running on siblings:
2901 static inline unsigned long smt_slice(task_t
*p
, struct sched_domain
*sd
)
2903 return p
->time_slice
* (100 - sd
->per_cpu_gain
) / 100;
2907 * To minimise lock contention and not have to drop this_rq's runlock we only
2908 * trylock the sibling runqueues and bypass those runqueues if we fail to
2909 * acquire their lock. As we only trylock the normal locking order does not
2910 * need to be obeyed.
2912 static int dependent_sleeper(int this_cpu
, runqueue_t
*this_rq
, task_t
*p
)
2914 struct sched_domain
*tmp
, *sd
= NULL
;
2917 /* kernel/rt threads do not participate in dependent sleeping */
2918 if (!p
->mm
|| rt_task(p
))
2921 for_each_domain(this_cpu
, tmp
) {
2922 if (tmp
->flags
& SD_SHARE_CPUPOWER
) {
2931 for_each_cpu_mask(i
, sd
->span
) {
2939 if (unlikely(!spin_trylock(&smt_rq
->lock
)))
2942 smt_curr
= smt_rq
->curr
;
2948 * If a user task with lower static priority than the
2949 * running task on the SMT sibling is trying to schedule,
2950 * delay it till there is proportionately less timeslice
2951 * left of the sibling task to prevent a lower priority
2952 * task from using an unfair proportion of the
2953 * physical cpu's resources. -ck
2955 if (rt_task(smt_curr
)) {
2957 * With real time tasks we run non-rt tasks only
2958 * per_cpu_gain% of the time.
2960 if ((jiffies
% DEF_TIMESLICE
) >
2961 (sd
->per_cpu_gain
* DEF_TIMESLICE
/ 100))
2964 if (smt_curr
->static_prio
< p
->static_prio
&&
2965 !TASK_PREEMPTS_CURR(p
, smt_rq
) &&
2966 smt_slice(smt_curr
, sd
) > task_timeslice(p
))
2970 spin_unlock(&smt_rq
->lock
);
2975 static inline void wake_sleeping_dependent(int this_cpu
)
2979 static inline int dependent_sleeper(int this_cpu
, runqueue_t
*this_rq
,
2986 #if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT)
2988 void fastcall
add_preempt_count(int val
)
2993 BUG_ON((preempt_count() < 0));
2994 preempt_count() += val
;
2996 * Spinlock count overflowing soon?
2998 BUG_ON((preempt_count() & PREEMPT_MASK
) >= PREEMPT_MASK
-10);
3000 EXPORT_SYMBOL(add_preempt_count
);
3002 void fastcall
sub_preempt_count(int val
)
3007 BUG_ON(val
> preempt_count());
3009 * Is the spinlock portion underflowing?
3011 BUG_ON((val
< PREEMPT_MASK
) && !(preempt_count() & PREEMPT_MASK
));
3012 preempt_count() -= val
;
3014 EXPORT_SYMBOL(sub_preempt_count
);
3018 static inline int interactive_sleep(enum sleep_type sleep_type
)
3020 return (sleep_type
== SLEEP_INTERACTIVE
||
3021 sleep_type
== SLEEP_INTERRUPTED
);
3025 * schedule() is the main scheduler function.
3027 asmlinkage
void __sched
schedule(void)
3030 task_t
*prev
, *next
;
3032 prio_array_t
*array
;
3033 struct list_head
*queue
;
3034 unsigned long long now
;
3035 unsigned long run_time
;
3036 int cpu
, idx
, new_prio
;
3039 * Test if we are atomic. Since do_exit() needs to call into
3040 * schedule() atomically, we ignore that path for now.
3041 * Otherwise, whine if we are scheduling when we should not be.
3043 if (unlikely(in_atomic() && !current
->exit_state
)) {
3044 printk(KERN_ERR
"BUG: scheduling while atomic: "
3046 current
->comm
, preempt_count(), current
->pid
);
3049 profile_hit(SCHED_PROFILING
, __builtin_return_address(0));
3054 release_kernel_lock(prev
);
3055 need_resched_nonpreemptible
:
3059 * The idle thread is not allowed to schedule!
3060 * Remove this check after it has been exercised a bit.
3062 if (unlikely(prev
== rq
->idle
) && prev
->state
!= TASK_RUNNING
) {
3063 printk(KERN_ERR
"bad: scheduling from the idle thread!\n");
3067 schedstat_inc(rq
, sched_cnt
);
3068 now
= sched_clock();
3069 if (likely((long long)(now
- prev
->timestamp
) < NS_MAX_SLEEP_AVG
)) {
3070 run_time
= now
- prev
->timestamp
;
3071 if (unlikely((long long)(now
- prev
->timestamp
) < 0))
3074 run_time
= NS_MAX_SLEEP_AVG
;
3077 * Tasks charged proportionately less run_time at high sleep_avg to
3078 * delay them losing their interactive status
3080 run_time
/= (CURRENT_BONUS(prev
) ? : 1);
3082 spin_lock_irq(&rq
->lock
);
3084 if (unlikely(prev
->flags
& PF_DEAD
))
3085 prev
->state
= EXIT_DEAD
;
3087 switch_count
= &prev
->nivcsw
;
3088 if (prev
->state
&& !(preempt_count() & PREEMPT_ACTIVE
)) {
3089 switch_count
= &prev
->nvcsw
;
3090 if (unlikely((prev
->state
& TASK_INTERRUPTIBLE
) &&
3091 unlikely(signal_pending(prev
))))
3092 prev
->state
= TASK_RUNNING
;
3094 if (prev
->state
== TASK_UNINTERRUPTIBLE
)
3095 rq
->nr_uninterruptible
++;
3096 deactivate_task(prev
, rq
);
3100 cpu
= smp_processor_id();
3101 if (unlikely(!rq
->nr_running
)) {
3102 idle_balance(cpu
, rq
);
3103 if (!rq
->nr_running
) {
3105 rq
->expired_timestamp
= 0;
3106 wake_sleeping_dependent(cpu
);
3112 if (unlikely(!array
->nr_active
)) {
3114 * Switch the active and expired arrays.
3116 schedstat_inc(rq
, sched_switch
);
3117 rq
->active
= rq
->expired
;
3118 rq
->expired
= array
;
3120 rq
->expired_timestamp
= 0;
3121 rq
->best_expired_prio
= MAX_PRIO
;
3124 idx
= sched_find_first_bit(array
->bitmap
);
3125 queue
= array
->queue
+ idx
;
3126 next
= list_entry(queue
->next
, task_t
, run_list
);
3128 if (!rt_task(next
) && interactive_sleep(next
->sleep_type
)) {
3129 unsigned long long delta
= now
- next
->timestamp
;
3130 if (unlikely((long long)(now
- next
->timestamp
) < 0))
3133 if (next
->sleep_type
== SLEEP_INTERACTIVE
)
3134 delta
= delta
* (ON_RUNQUEUE_WEIGHT
* 128 / 100) / 128;
3136 array
= next
->array
;
3137 new_prio
= recalc_task_prio(next
, next
->timestamp
+ delta
);
3139 if (unlikely(next
->prio
!= new_prio
)) {
3140 dequeue_task(next
, array
);
3141 next
->prio
= new_prio
;
3142 enqueue_task(next
, array
);
3145 next
->sleep_type
= SLEEP_NORMAL
;
3146 if (dependent_sleeper(cpu
, rq
, next
))
3149 if (next
== rq
->idle
)
3150 schedstat_inc(rq
, sched_goidle
);
3152 prefetch_stack(next
);
3153 clear_tsk_need_resched(prev
);
3154 rcu_qsctr_inc(task_cpu(prev
));
3156 update_cpu_clock(prev
, rq
, now
);
3158 prev
->sleep_avg
-= run_time
;
3159 if ((long)prev
->sleep_avg
<= 0)
3160 prev
->sleep_avg
= 0;
3161 prev
->timestamp
= prev
->last_ran
= now
;
3163 sched_info_switch(prev
, next
);
3164 if (likely(prev
!= next
)) {
3165 next
->timestamp
= now
;
3170 prepare_task_switch(rq
, next
);
3171 prev
= context_switch(rq
, prev
, next
);
3174 * this_rq must be evaluated again because prev may have moved
3175 * CPUs since it called schedule(), thus the 'rq' on its stack
3176 * frame will be invalid.
3178 finish_task_switch(this_rq(), prev
);
3180 spin_unlock_irq(&rq
->lock
);
3183 if (unlikely(reacquire_kernel_lock(prev
) < 0))
3184 goto need_resched_nonpreemptible
;
3185 preempt_enable_no_resched();
3186 if (unlikely(test_thread_flag(TIF_NEED_RESCHED
)))
3190 EXPORT_SYMBOL(schedule
);
3192 #ifdef CONFIG_PREEMPT
3194 * this is is the entry point to schedule() from in-kernel preemption
3195 * off of preempt_enable. Kernel preemptions off return from interrupt
3196 * occur there and call schedule directly.
3198 asmlinkage
void __sched
preempt_schedule(void)
3200 struct thread_info
*ti
= current_thread_info();
3201 #ifdef CONFIG_PREEMPT_BKL
3202 struct task_struct
*task
= current
;
3203 int saved_lock_depth
;
3206 * If there is a non-zero preempt_count or interrupts are disabled,
3207 * we do not want to preempt the current task. Just return..
3209 if (unlikely(ti
->preempt_count
|| irqs_disabled()))
3213 add_preempt_count(PREEMPT_ACTIVE
);
3215 * We keep the big kernel semaphore locked, but we
3216 * clear ->lock_depth so that schedule() doesnt
3217 * auto-release the semaphore:
3219 #ifdef CONFIG_PREEMPT_BKL
3220 saved_lock_depth
= task
->lock_depth
;
3221 task
->lock_depth
= -1;
3224 #ifdef CONFIG_PREEMPT_BKL
3225 task
->lock_depth
= saved_lock_depth
;
3227 sub_preempt_count(PREEMPT_ACTIVE
);
3229 /* we could miss a preemption opportunity between schedule and now */
3231 if (unlikely(test_thread_flag(TIF_NEED_RESCHED
)))
3235 EXPORT_SYMBOL(preempt_schedule
);
3238 * this is is the entry point to schedule() from kernel preemption
3239 * off of irq context.
3240 * Note, that this is called and return with irqs disabled. This will
3241 * protect us against recursive calling from irq.
3243 asmlinkage
void __sched
preempt_schedule_irq(void)
3245 struct thread_info
*ti
= current_thread_info();
3246 #ifdef CONFIG_PREEMPT_BKL
3247 struct task_struct
*task
= current
;
3248 int saved_lock_depth
;
3250 /* Catch callers which need to be fixed*/
3251 BUG_ON(ti
->preempt_count
|| !irqs_disabled());
3254 add_preempt_count(PREEMPT_ACTIVE
);
3256 * We keep the big kernel semaphore locked, but we
3257 * clear ->lock_depth so that schedule() doesnt
3258 * auto-release the semaphore:
3260 #ifdef CONFIG_PREEMPT_BKL
3261 saved_lock_depth
= task
->lock_depth
;
3262 task
->lock_depth
= -1;
3266 local_irq_disable();
3267 #ifdef CONFIG_PREEMPT_BKL
3268 task
->lock_depth
= saved_lock_depth
;
3270 sub_preempt_count(PREEMPT_ACTIVE
);
3272 /* we could miss a preemption opportunity between schedule and now */
3274 if (unlikely(test_thread_flag(TIF_NEED_RESCHED
)))
3278 #endif /* CONFIG_PREEMPT */
3280 int default_wake_function(wait_queue_t
*curr
, unsigned mode
, int sync
,
3283 task_t
*p
= curr
->private;
3284 return try_to_wake_up(p
, mode
, sync
);
3287 EXPORT_SYMBOL(default_wake_function
);
3290 * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
3291 * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
3292 * number) then we wake all the non-exclusive tasks and one exclusive task.
3294 * There are circumstances in which we can try to wake a task which has already
3295 * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
3296 * zero in this (rare) case, and we handle it by continuing to scan the queue.
3298 static void __wake_up_common(wait_queue_head_t
*q
, unsigned int mode
,
3299 int nr_exclusive
, int sync
, void *key
)
3301 struct list_head
*tmp
, *next
;
3303 list_for_each_safe(tmp
, next
, &q
->task_list
) {
3306 curr
= list_entry(tmp
, wait_queue_t
, task_list
);
3307 flags
= curr
->flags
;
3308 if (curr
->func(curr
, mode
, sync
, key
) &&
3309 (flags
& WQ_FLAG_EXCLUSIVE
) &&
3316 * __wake_up - wake up threads blocked on a waitqueue.
3318 * @mode: which threads
3319 * @nr_exclusive: how many wake-one or wake-many threads to wake up
3320 * @key: is directly passed to the wakeup function
3322 void fastcall
__wake_up(wait_queue_head_t
*q
, unsigned int mode
,
3323 int nr_exclusive
, void *key
)
3325 unsigned long flags
;
3327 spin_lock_irqsave(&q
->lock
, flags
);
3328 __wake_up_common(q
, mode
, nr_exclusive
, 0, key
);
3329 spin_unlock_irqrestore(&q
->lock
, flags
);
3332 EXPORT_SYMBOL(__wake_up
);
3335 * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
3337 void fastcall
__wake_up_locked(wait_queue_head_t
*q
, unsigned int mode
)
3339 __wake_up_common(q
, mode
, 1, 0, NULL
);
3343 * __wake_up_sync - wake up threads blocked on a waitqueue.
3345 * @mode: which threads
3346 * @nr_exclusive: how many wake-one or wake-many threads to wake up
3348 * The sync wakeup differs that the waker knows that it will schedule
3349 * away soon, so while the target thread will be woken up, it will not
3350 * be migrated to another CPU - ie. the two threads are 'synchronized'
3351 * with each other. This can prevent needless bouncing between CPUs.
3353 * On UP it can prevent extra preemption.
3356 __wake_up_sync(wait_queue_head_t
*q
, unsigned int mode
, int nr_exclusive
)
3358 unsigned long flags
;
3364 if (unlikely(!nr_exclusive
))
3367 spin_lock_irqsave(&q
->lock
, flags
);
3368 __wake_up_common(q
, mode
, nr_exclusive
, sync
, NULL
);
3369 spin_unlock_irqrestore(&q
->lock
, flags
);
3371 EXPORT_SYMBOL_GPL(__wake_up_sync
); /* For internal use only */
3373 void fastcall
complete(struct completion
*x
)
3375 unsigned long flags
;
3377 spin_lock_irqsave(&x
->wait
.lock
, flags
);
3379 __wake_up_common(&x
->wait
, TASK_UNINTERRUPTIBLE
| TASK_INTERRUPTIBLE
,
3381 spin_unlock_irqrestore(&x
->wait
.lock
, flags
);
3383 EXPORT_SYMBOL(complete
);
3385 void fastcall
complete_all(struct completion
*x
)
3387 unsigned long flags
;
3389 spin_lock_irqsave(&x
->wait
.lock
, flags
);
3390 x
->done
+= UINT_MAX
/2;
3391 __wake_up_common(&x
->wait
, TASK_UNINTERRUPTIBLE
| TASK_INTERRUPTIBLE
,
3393 spin_unlock_irqrestore(&x
->wait
.lock
, flags
);
3395 EXPORT_SYMBOL(complete_all
);
3397 void fastcall __sched
wait_for_completion(struct completion
*x
)
3400 spin_lock_irq(&x
->wait
.lock
);
3402 DECLARE_WAITQUEUE(wait
, current
);
3404 wait
.flags
|= WQ_FLAG_EXCLUSIVE
;
3405 __add_wait_queue_tail(&x
->wait
, &wait
);
3407 __set_current_state(TASK_UNINTERRUPTIBLE
);
3408 spin_unlock_irq(&x
->wait
.lock
);
3410 spin_lock_irq(&x
->wait
.lock
);
3412 __remove_wait_queue(&x
->wait
, &wait
);
3415 spin_unlock_irq(&x
->wait
.lock
);
3417 EXPORT_SYMBOL(wait_for_completion
);
3419 unsigned long fastcall __sched
3420 wait_for_completion_timeout(struct completion
*x
, unsigned long timeout
)
3424 spin_lock_irq(&x
->wait
.lock
);
3426 DECLARE_WAITQUEUE(wait
, current
);
3428 wait
.flags
|= WQ_FLAG_EXCLUSIVE
;
3429 __add_wait_queue_tail(&x
->wait
, &wait
);
3431 __set_current_state(TASK_UNINTERRUPTIBLE
);
3432 spin_unlock_irq(&x
->wait
.lock
);
3433 timeout
= schedule_timeout(timeout
);
3434 spin_lock_irq(&x
->wait
.lock
);
3436 __remove_wait_queue(&x
->wait
, &wait
);
3440 __remove_wait_queue(&x
->wait
, &wait
);
3444 spin_unlock_irq(&x
->wait
.lock
);
3447 EXPORT_SYMBOL(wait_for_completion_timeout
);
3449 int fastcall __sched
wait_for_completion_interruptible(struct completion
*x
)
3455 spin_lock_irq(&x
->wait
.lock
);
3457 DECLARE_WAITQUEUE(wait
, current
);
3459 wait
.flags
|= WQ_FLAG_EXCLUSIVE
;
3460 __add_wait_queue_tail(&x
->wait
, &wait
);
3462 if (signal_pending(current
)) {
3464 __remove_wait_queue(&x
->wait
, &wait
);
3467 __set_current_state(TASK_INTERRUPTIBLE
);
3468 spin_unlock_irq(&x
->wait
.lock
);
3470 spin_lock_irq(&x
->wait
.lock
);
3472 __remove_wait_queue(&x
->wait
, &wait
);
3476 spin_unlock_irq(&x
->wait
.lock
);
3480 EXPORT_SYMBOL(wait_for_completion_interruptible
);
3482 unsigned long fastcall __sched
3483 wait_for_completion_interruptible_timeout(struct completion
*x
,
3484 unsigned long timeout
)
3488 spin_lock_irq(&x
->wait
.lock
);
3490 DECLARE_WAITQUEUE(wait
, current
);
3492 wait
.flags
|= WQ_FLAG_EXCLUSIVE
;
3493 __add_wait_queue_tail(&x
->wait
, &wait
);
3495 if (signal_pending(current
)) {
3496 timeout
= -ERESTARTSYS
;
3497 __remove_wait_queue(&x
->wait
, &wait
);
3500 __set_current_state(TASK_INTERRUPTIBLE
);
3501 spin_unlock_irq(&x
->wait
.lock
);
3502 timeout
= schedule_timeout(timeout
);
3503 spin_lock_irq(&x
->wait
.lock
);
3505 __remove_wait_queue(&x
->wait
, &wait
);
3509 __remove_wait_queue(&x
->wait
, &wait
);
3513 spin_unlock_irq(&x
->wait
.lock
);
3516 EXPORT_SYMBOL(wait_for_completion_interruptible_timeout
);
3519 #define SLEEP_ON_VAR \
3520 unsigned long flags; \
3521 wait_queue_t wait; \
3522 init_waitqueue_entry(&wait, current);
3524 #define SLEEP_ON_HEAD \
3525 spin_lock_irqsave(&q->lock,flags); \
3526 __add_wait_queue(q, &wait); \
3527 spin_unlock(&q->lock);
3529 #define SLEEP_ON_TAIL \
3530 spin_lock_irq(&q->lock); \
3531 __remove_wait_queue(q, &wait); \
3532 spin_unlock_irqrestore(&q->lock, flags);
3534 void fastcall __sched
interruptible_sleep_on(wait_queue_head_t
*q
)
3538 current
->state
= TASK_INTERRUPTIBLE
;
3545 EXPORT_SYMBOL(interruptible_sleep_on
);
3547 long fastcall __sched
3548 interruptible_sleep_on_timeout(wait_queue_head_t
*q
, long timeout
)
3552 current
->state
= TASK_INTERRUPTIBLE
;
3555 timeout
= schedule_timeout(timeout
);
3561 EXPORT_SYMBOL(interruptible_sleep_on_timeout
);
3563 void fastcall __sched
sleep_on(wait_queue_head_t
*q
)
3567 current
->state
= TASK_UNINTERRUPTIBLE
;
3574 EXPORT_SYMBOL(sleep_on
);
3576 long fastcall __sched
sleep_on_timeout(wait_queue_head_t
*q
, long timeout
)
3580 current
->state
= TASK_UNINTERRUPTIBLE
;
3583 timeout
= schedule_timeout(timeout
);
3589 EXPORT_SYMBOL(sleep_on_timeout
);
3591 void set_user_nice(task_t
*p
, long nice
)
3593 unsigned long flags
;
3594 prio_array_t
*array
;
3596 int old_prio
, new_prio
, delta
;
3598 if (TASK_NICE(p
) == nice
|| nice
< -20 || nice
> 19)
3601 * We have to be careful, if called from sys_setpriority(),
3602 * the task might be in the middle of scheduling on another CPU.
3604 rq
= task_rq_lock(p
, &flags
);
3606 * The RT priorities are set via sched_setscheduler(), but we still
3607 * allow the 'normal' nice value to be set - but as expected
3608 * it wont have any effect on scheduling until the task is
3609 * not SCHED_NORMAL/SCHED_BATCH:
3612 p
->static_prio
= NICE_TO_PRIO(nice
);
3617 dequeue_task(p
, array
);
3618 dec_raw_weighted_load(rq
, p
);
3622 new_prio
= NICE_TO_PRIO(nice
);
3623 delta
= new_prio
- old_prio
;
3624 p
->static_prio
= NICE_TO_PRIO(nice
);
3629 enqueue_task(p
, array
);
3630 inc_raw_weighted_load(rq
, p
);
3632 * If the task increased its priority or is running and
3633 * lowered its priority, then reschedule its CPU:
3635 if (delta
< 0 || (delta
> 0 && task_running(rq
, p
)))
3636 resched_task(rq
->curr
);
3639 task_rq_unlock(rq
, &flags
);
3642 EXPORT_SYMBOL(set_user_nice
);
3645 * can_nice - check if a task can reduce its nice value
3649 int can_nice(const task_t
*p
, const int nice
)
3651 /* convert nice value [19,-20] to rlimit style value [1,40] */
3652 int nice_rlim
= 20 - nice
;
3653 return (nice_rlim
<= p
->signal
->rlim
[RLIMIT_NICE
].rlim_cur
||
3654 capable(CAP_SYS_NICE
));
3657 #ifdef __ARCH_WANT_SYS_NICE
3660 * sys_nice - change the priority of the current process.
3661 * @increment: priority increment
3663 * sys_setpriority is a more generic, but much slower function that
3664 * does similar things.
3666 asmlinkage
long sys_nice(int increment
)
3672 * Setpriority might change our priority at the same moment.
3673 * We don't have to worry. Conceptually one call occurs first
3674 * and we have a single winner.
3676 if (increment
< -40)
3681 nice
= PRIO_TO_NICE(current
->static_prio
) + increment
;
3687 if (increment
< 0 && !can_nice(current
, nice
))
3690 retval
= security_task_setnice(current
, nice
);
3694 set_user_nice(current
, nice
);
3701 * task_prio - return the priority value of a given task.
3702 * @p: the task in question.
3704 * This is the priority value as seen by users in /proc.
3705 * RT tasks are offset by -200. Normal tasks are centered
3706 * around 0, value goes from -16 to +15.
3708 int task_prio(const task_t
*p
)
3710 return p
->prio
- MAX_RT_PRIO
;
3714 * task_nice - return the nice value of a given task.
3715 * @p: the task in question.
3717 int task_nice(const task_t
*p
)
3719 return TASK_NICE(p
);
3721 EXPORT_SYMBOL_GPL(task_nice
);
3724 * idle_cpu - is a given cpu idle currently?
3725 * @cpu: the processor in question.
3727 int idle_cpu(int cpu
)
3729 return cpu_curr(cpu
) == cpu_rq(cpu
)->idle
;
3733 * idle_task - return the idle task for a given cpu.
3734 * @cpu: the processor in question.
3736 task_t
*idle_task(int cpu
)
3738 return cpu_rq(cpu
)->idle
;
3742 * find_process_by_pid - find a process with a matching PID value.
3743 * @pid: the pid in question.
3745 static inline task_t
*find_process_by_pid(pid_t pid
)
3747 return pid
? find_task_by_pid(pid
) : current
;
3750 /* Actually do priority change: must hold rq lock. */
3751 static void __setscheduler(struct task_struct
*p
, int policy
, int prio
)
3755 p
->rt_priority
= prio
;
3756 if (policy
!= SCHED_NORMAL
&& policy
!= SCHED_BATCH
) {
3757 p
->prio
= MAX_RT_PRIO
-1 - p
->rt_priority
;
3759 p
->prio
= p
->static_prio
;
3761 * SCHED_BATCH tasks are treated as perpetual CPU hogs:
3763 if (policy
== SCHED_BATCH
)
3770 * sched_setscheduler - change the scheduling policy and/or RT priority of
3772 * @p: the task in question.
3773 * @policy: new policy.
3774 * @param: structure containing the new RT priority.
3776 int sched_setscheduler(struct task_struct
*p
, int policy
,
3777 struct sched_param
*param
)
3780 int oldprio
, oldpolicy
= -1;
3781 prio_array_t
*array
;
3782 unsigned long flags
;
3786 /* double check policy once rq lock held */
3788 policy
= oldpolicy
= p
->policy
;
3789 else if (policy
!= SCHED_FIFO
&& policy
!= SCHED_RR
&&
3790 policy
!= SCHED_NORMAL
&& policy
!= SCHED_BATCH
)
3793 * Valid priorities for SCHED_FIFO and SCHED_RR are
3794 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL and
3797 if (param
->sched_priority
< 0 ||
3798 (p
->mm
&& param
->sched_priority
> MAX_USER_RT_PRIO
-1) ||
3799 (!p
->mm
&& param
->sched_priority
> MAX_RT_PRIO
-1))
3801 if ((policy
== SCHED_NORMAL
|| policy
== SCHED_BATCH
)
3802 != (param
->sched_priority
== 0))
3806 * Allow unprivileged RT tasks to decrease priority:
3808 if (!capable(CAP_SYS_NICE
)) {
3810 * can't change policy, except between SCHED_NORMAL
3813 if (((policy
!= SCHED_NORMAL
&& p
->policy
!= SCHED_BATCH
) &&
3814 (policy
!= SCHED_BATCH
&& p
->policy
!= SCHED_NORMAL
)) &&
3815 !p
->signal
->rlim
[RLIMIT_RTPRIO
].rlim_cur
)
3817 /* can't increase priority */
3818 if ((policy
!= SCHED_NORMAL
&& policy
!= SCHED_BATCH
) &&
3819 param
->sched_priority
> p
->rt_priority
&&
3820 param
->sched_priority
>
3821 p
->signal
->rlim
[RLIMIT_RTPRIO
].rlim_cur
)
3823 /* can't change other user's priorities */
3824 if ((current
->euid
!= p
->euid
) &&
3825 (current
->euid
!= p
->uid
))
3829 retval
= security_task_setscheduler(p
, policy
, param
);
3833 * To be able to change p->policy safely, the apropriate
3834 * runqueue lock must be held.
3836 rq
= task_rq_lock(p
, &flags
);
3837 /* recheck policy now with rq lock held */
3838 if (unlikely(oldpolicy
!= -1 && oldpolicy
!= p
->policy
)) {
3839 policy
= oldpolicy
= -1;
3840 task_rq_unlock(rq
, &flags
);
3845 deactivate_task(p
, rq
);
3847 __setscheduler(p
, policy
, param
->sched_priority
);
3849 __activate_task(p
, rq
);
3851 * Reschedule if we are currently running on this runqueue and
3852 * our priority decreased, or if we are not currently running on
3853 * this runqueue and our priority is higher than the current's
3855 if (task_running(rq
, p
)) {
3856 if (p
->prio
> oldprio
)
3857 resched_task(rq
->curr
);
3858 } else if (TASK_PREEMPTS_CURR(p
, rq
))
3859 resched_task(rq
->curr
);
3861 task_rq_unlock(rq
, &flags
);
3864 EXPORT_SYMBOL_GPL(sched_setscheduler
);
3867 do_sched_setscheduler(pid_t pid
, int policy
, struct sched_param __user
*param
)
3870 struct sched_param lparam
;
3871 struct task_struct
*p
;
3873 if (!param
|| pid
< 0)
3875 if (copy_from_user(&lparam
, param
, sizeof(struct sched_param
)))
3877 read_lock_irq(&tasklist_lock
);
3878 p
= find_process_by_pid(pid
);
3880 read_unlock_irq(&tasklist_lock
);
3883 retval
= sched_setscheduler(p
, policy
, &lparam
);
3884 read_unlock_irq(&tasklist_lock
);
3889 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
3890 * @pid: the pid in question.
3891 * @policy: new policy.
3892 * @param: structure containing the new RT priority.
3894 asmlinkage
long sys_sched_setscheduler(pid_t pid
, int policy
,
3895 struct sched_param __user
*param
)
3897 /* negative values for policy are not valid */
3901 return do_sched_setscheduler(pid
, policy
, param
);
3905 * sys_sched_setparam - set/change the RT priority of a thread
3906 * @pid: the pid in question.
3907 * @param: structure containing the new RT priority.
3909 asmlinkage
long sys_sched_setparam(pid_t pid
, struct sched_param __user
*param
)
3911 return do_sched_setscheduler(pid
, -1, param
);
3915 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
3916 * @pid: the pid in question.
3918 asmlinkage
long sys_sched_getscheduler(pid_t pid
)
3920 int retval
= -EINVAL
;
3927 read_lock(&tasklist_lock
);
3928 p
= find_process_by_pid(pid
);
3930 retval
= security_task_getscheduler(p
);
3934 read_unlock(&tasklist_lock
);
3941 * sys_sched_getscheduler - get the RT priority of a thread
3942 * @pid: the pid in question.
3943 * @param: structure containing the RT priority.
3945 asmlinkage
long sys_sched_getparam(pid_t pid
, struct sched_param __user
*param
)
3947 struct sched_param lp
;
3948 int retval
= -EINVAL
;
3951 if (!param
|| pid
< 0)
3954 read_lock(&tasklist_lock
);
3955 p
= find_process_by_pid(pid
);
3960 retval
= security_task_getscheduler(p
);
3964 lp
.sched_priority
= p
->rt_priority
;
3965 read_unlock(&tasklist_lock
);
3968 * This one might sleep, we cannot do it with a spinlock held ...
3970 retval
= copy_to_user(param
, &lp
, sizeof(*param
)) ? -EFAULT
: 0;
3976 read_unlock(&tasklist_lock
);
3980 long sched_setaffinity(pid_t pid
, cpumask_t new_mask
)
3984 cpumask_t cpus_allowed
;
3987 read_lock(&tasklist_lock
);
3989 p
= find_process_by_pid(pid
);
3991 read_unlock(&tasklist_lock
);
3992 unlock_cpu_hotplug();
3997 * It is not safe to call set_cpus_allowed with the
3998 * tasklist_lock held. We will bump the task_struct's
3999 * usage count and then drop tasklist_lock.
4002 read_unlock(&tasklist_lock
);
4005 if ((current
->euid
!= p
->euid
) && (current
->euid
!= p
->uid
) &&
4006 !capable(CAP_SYS_NICE
))
4009 retval
= security_task_setscheduler(p
, 0, NULL
);
4013 cpus_allowed
= cpuset_cpus_allowed(p
);
4014 cpus_and(new_mask
, new_mask
, cpus_allowed
);
4015 retval
= set_cpus_allowed(p
, new_mask
);
4019 unlock_cpu_hotplug();
4023 static int get_user_cpu_mask(unsigned long __user
*user_mask_ptr
, unsigned len
,
4024 cpumask_t
*new_mask
)
4026 if (len
< sizeof(cpumask_t
)) {
4027 memset(new_mask
, 0, sizeof(cpumask_t
));
4028 } else if (len
> sizeof(cpumask_t
)) {
4029 len
= sizeof(cpumask_t
);
4031 return copy_from_user(new_mask
, user_mask_ptr
, len
) ? -EFAULT
: 0;
4035 * sys_sched_setaffinity - set the cpu affinity of a process
4036 * @pid: pid of the process
4037 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4038 * @user_mask_ptr: user-space pointer to the new cpu mask
4040 asmlinkage
long sys_sched_setaffinity(pid_t pid
, unsigned int len
,
4041 unsigned long __user
*user_mask_ptr
)
4046 retval
= get_user_cpu_mask(user_mask_ptr
, len
, &new_mask
);
4050 return sched_setaffinity(pid
, new_mask
);
4054 * Represents all cpu's present in the system
4055 * In systems capable of hotplug, this map could dynamically grow
4056 * as new cpu's are detected in the system via any platform specific
4057 * method, such as ACPI for e.g.
4060 cpumask_t cpu_present_map __read_mostly
;
4061 EXPORT_SYMBOL(cpu_present_map
);
4064 cpumask_t cpu_online_map __read_mostly
= CPU_MASK_ALL
;
4065 cpumask_t cpu_possible_map __read_mostly
= CPU_MASK_ALL
;
4068 long sched_getaffinity(pid_t pid
, cpumask_t
*mask
)
4074 read_lock(&tasklist_lock
);
4077 p
= find_process_by_pid(pid
);
4081 retval
= security_task_getscheduler(p
);
4085 cpus_and(*mask
, p
->cpus_allowed
, cpu_online_map
);
4088 read_unlock(&tasklist_lock
);
4089 unlock_cpu_hotplug();
4097 * sys_sched_getaffinity - get the cpu affinity of a process
4098 * @pid: pid of the process
4099 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4100 * @user_mask_ptr: user-space pointer to hold the current cpu mask
4102 asmlinkage
long sys_sched_getaffinity(pid_t pid
, unsigned int len
,
4103 unsigned long __user
*user_mask_ptr
)
4108 if (len
< sizeof(cpumask_t
))
4111 ret
= sched_getaffinity(pid
, &mask
);
4115 if (copy_to_user(user_mask_ptr
, &mask
, sizeof(cpumask_t
)))
4118 return sizeof(cpumask_t
);
4122 * sys_sched_yield - yield the current processor to other threads.
4124 * this function yields the current CPU by moving the calling thread
4125 * to the expired array. If there are no other threads running on this
4126 * CPU then this function will return.
4128 asmlinkage
long sys_sched_yield(void)
4130 runqueue_t
*rq
= this_rq_lock();
4131 prio_array_t
*array
= current
->array
;
4132 prio_array_t
*target
= rq
->expired
;
4134 schedstat_inc(rq
, yld_cnt
);
4136 * We implement yielding by moving the task into the expired
4139 * (special rule: RT tasks will just roundrobin in the active
4142 if (rt_task(current
))
4143 target
= rq
->active
;
4145 if (array
->nr_active
== 1) {
4146 schedstat_inc(rq
, yld_act_empty
);
4147 if (!rq
->expired
->nr_active
)
4148 schedstat_inc(rq
, yld_both_empty
);
4149 } else if (!rq
->expired
->nr_active
)
4150 schedstat_inc(rq
, yld_exp_empty
);
4152 if (array
!= target
) {
4153 dequeue_task(current
, array
);
4154 enqueue_task(current
, target
);
4157 * requeue_task is cheaper so perform that if possible.
4159 requeue_task(current
, array
);
4162 * Since we are going to call schedule() anyway, there's
4163 * no need to preempt or enable interrupts:
4165 __release(rq
->lock
);
4166 _raw_spin_unlock(&rq
->lock
);
4167 preempt_enable_no_resched();
4174 static inline void __cond_resched(void)
4176 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
4177 __might_sleep(__FILE__
, __LINE__
);
4180 * The BKS might be reacquired before we have dropped
4181 * PREEMPT_ACTIVE, which could trigger a second
4182 * cond_resched() call.
4184 if (unlikely(preempt_count()))
4186 if (unlikely(system_state
!= SYSTEM_RUNNING
))
4189 add_preempt_count(PREEMPT_ACTIVE
);
4191 sub_preempt_count(PREEMPT_ACTIVE
);
4192 } while (need_resched());
4195 int __sched
cond_resched(void)
4197 if (need_resched()) {
4204 EXPORT_SYMBOL(cond_resched
);
4207 * cond_resched_lock() - if a reschedule is pending, drop the given lock,
4208 * call schedule, and on return reacquire the lock.
4210 * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
4211 * operations here to prevent schedule() from being called twice (once via
4212 * spin_unlock(), once by hand).
4214 int cond_resched_lock(spinlock_t
*lock
)
4218 if (need_lockbreak(lock
)) {
4224 if (need_resched()) {
4225 _raw_spin_unlock(lock
);
4226 preempt_enable_no_resched();
4234 EXPORT_SYMBOL(cond_resched_lock
);
4236 int __sched
cond_resched_softirq(void)
4238 BUG_ON(!in_softirq());
4240 if (need_resched()) {
4241 __local_bh_enable();
4249 EXPORT_SYMBOL(cond_resched_softirq
);
4253 * yield - yield the current processor to other threads.
4255 * this is a shortcut for kernel-space yielding - it marks the
4256 * thread runnable and calls sys_sched_yield().
4258 void __sched
yield(void)
4260 set_current_state(TASK_RUNNING
);
4264 EXPORT_SYMBOL(yield
);
4267 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
4268 * that process accounting knows that this is a task in IO wait state.
4270 * But don't do that if it is a deliberate, throttling IO wait (this task
4271 * has set its backing_dev_info: the queue against which it should throttle)
4273 void __sched
io_schedule(void)
4275 struct runqueue
*rq
= &__raw_get_cpu_var(runqueues
);
4277 atomic_inc(&rq
->nr_iowait
);
4279 atomic_dec(&rq
->nr_iowait
);
4282 EXPORT_SYMBOL(io_schedule
);
4284 long __sched
io_schedule_timeout(long timeout
)
4286 struct runqueue
*rq
= &__raw_get_cpu_var(runqueues
);
4289 atomic_inc(&rq
->nr_iowait
);
4290 ret
= schedule_timeout(timeout
);
4291 atomic_dec(&rq
->nr_iowait
);
4296 * sys_sched_get_priority_max - return maximum RT priority.
4297 * @policy: scheduling class.
4299 * this syscall returns the maximum rt_priority that can be used
4300 * by a given scheduling class.
4302 asmlinkage
long sys_sched_get_priority_max(int policy
)
4309 ret
= MAX_USER_RT_PRIO
-1;
4320 * sys_sched_get_priority_min - return minimum RT priority.
4321 * @policy: scheduling class.
4323 * this syscall returns the minimum rt_priority that can be used
4324 * by a given scheduling class.
4326 asmlinkage
long sys_sched_get_priority_min(int policy
)
4343 * sys_sched_rr_get_interval - return the default timeslice of a process.
4344 * @pid: pid of the process.
4345 * @interval: userspace pointer to the timeslice value.
4347 * this syscall writes the default timeslice value of a given process
4348 * into the user-space timespec buffer. A value of '0' means infinity.
4351 long sys_sched_rr_get_interval(pid_t pid
, struct timespec __user
*interval
)
4353 int retval
= -EINVAL
;
4361 read_lock(&tasklist_lock
);
4362 p
= find_process_by_pid(pid
);
4366 retval
= security_task_getscheduler(p
);
4370 jiffies_to_timespec(p
->policy
== SCHED_FIFO
?
4371 0 : task_timeslice(p
), &t
);
4372 read_unlock(&tasklist_lock
);
4373 retval
= copy_to_user(interval
, &t
, sizeof(t
)) ? -EFAULT
: 0;
4377 read_unlock(&tasklist_lock
);
4381 static inline struct task_struct
*eldest_child(struct task_struct
*p
)
4383 if (list_empty(&p
->children
)) return NULL
;
4384 return list_entry(p
->children
.next
,struct task_struct
,sibling
);
4387 static inline struct task_struct
*older_sibling(struct task_struct
*p
)
4389 if (p
->sibling
.prev
==&p
->parent
->children
) return NULL
;
4390 return list_entry(p
->sibling
.prev
,struct task_struct
,sibling
);
4393 static inline struct task_struct
*younger_sibling(struct task_struct
*p
)
4395 if (p
->sibling
.next
==&p
->parent
->children
) return NULL
;
4396 return list_entry(p
->sibling
.next
,struct task_struct
,sibling
);
4399 static void show_task(task_t
*p
)
4403 unsigned long free
= 0;
4404 static const char *stat_nam
[] = { "R", "S", "D", "T", "t", "Z", "X" };
4406 printk("%-13.13s ", p
->comm
);
4407 state
= p
->state
? __ffs(p
->state
) + 1 : 0;
4408 if (state
< ARRAY_SIZE(stat_nam
))
4409 printk(stat_nam
[state
]);
4412 #if (BITS_PER_LONG == 32)
4413 if (state
== TASK_RUNNING
)
4414 printk(" running ");
4416 printk(" %08lX ", thread_saved_pc(p
));
4418 if (state
== TASK_RUNNING
)
4419 printk(" running task ");
4421 printk(" %016lx ", thread_saved_pc(p
));
4423 #ifdef CONFIG_DEBUG_STACK_USAGE
4425 unsigned long *n
= end_of_stack(p
);
4428 free
= (unsigned long)n
- (unsigned long)end_of_stack(p
);
4431 printk("%5lu %5d %6d ", free
, p
->pid
, p
->parent
->pid
);
4432 if ((relative
= eldest_child(p
)))
4433 printk("%5d ", relative
->pid
);
4436 if ((relative
= younger_sibling(p
)))
4437 printk("%7d", relative
->pid
);
4440 if ((relative
= older_sibling(p
)))
4441 printk(" %5d", relative
->pid
);
4445 printk(" (L-TLB)\n");
4447 printk(" (NOTLB)\n");
4449 if (state
!= TASK_RUNNING
)
4450 show_stack(p
, NULL
);
4453 void show_state(void)
4457 #if (BITS_PER_LONG == 32)
4460 printk(" task PC pid father child younger older\n");
4464 printk(" task PC pid father child younger older\n");
4466 read_lock(&tasklist_lock
);
4467 do_each_thread(g
, p
) {
4469 * reset the NMI-timeout, listing all files on a slow
4470 * console might take alot of time:
4472 touch_nmi_watchdog();
4474 } while_each_thread(g
, p
);
4476 read_unlock(&tasklist_lock
);
4477 mutex_debug_show_all_locks();
4481 * init_idle - set up an idle thread for a given CPU
4482 * @idle: task in question
4483 * @cpu: cpu the idle task belongs to
4485 * NOTE: this function does not set the idle thread's NEED_RESCHED
4486 * flag, to make booting more robust.
4488 void __devinit
init_idle(task_t
*idle
, int cpu
)
4490 runqueue_t
*rq
= cpu_rq(cpu
);
4491 unsigned long flags
;
4493 idle
->timestamp
= sched_clock();
4494 idle
->sleep_avg
= 0;
4496 idle
->prio
= MAX_PRIO
;
4497 idle
->state
= TASK_RUNNING
;
4498 idle
->cpus_allowed
= cpumask_of_cpu(cpu
);
4499 set_task_cpu(idle
, cpu
);
4501 spin_lock_irqsave(&rq
->lock
, flags
);
4502 rq
->curr
= rq
->idle
= idle
;
4503 #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
4506 spin_unlock_irqrestore(&rq
->lock
, flags
);
4508 /* Set the preempt count _outside_ the spinlocks! */
4509 #if defined(CONFIG_PREEMPT) && !defined(CONFIG_PREEMPT_BKL)
4510 task_thread_info(idle
)->preempt_count
= (idle
->lock_depth
>= 0);
4512 task_thread_info(idle
)->preempt_count
= 0;
4517 * In a system that switches off the HZ timer nohz_cpu_mask
4518 * indicates which cpus entered this state. This is used
4519 * in the rcu update to wait only for active cpus. For system
4520 * which do not switch off the HZ timer nohz_cpu_mask should
4521 * always be CPU_MASK_NONE.
4523 cpumask_t nohz_cpu_mask
= CPU_MASK_NONE
;
4527 * This is how migration works:
4529 * 1) we queue a migration_req_t structure in the source CPU's
4530 * runqueue and wake up that CPU's migration thread.
4531 * 2) we down() the locked semaphore => thread blocks.
4532 * 3) migration thread wakes up (implicitly it forces the migrated
4533 * thread off the CPU)
4534 * 4) it gets the migration request and checks whether the migrated
4535 * task is still in the wrong runqueue.
4536 * 5) if it's in the wrong runqueue then the migration thread removes
4537 * it and puts it into the right queue.
4538 * 6) migration thread up()s the semaphore.
4539 * 7) we wake up and the migration is done.
4543 * Change a given task's CPU affinity. Migrate the thread to a
4544 * proper CPU and schedule it away if the CPU it's executing on
4545 * is removed from the allowed bitmask.
4547 * NOTE: the caller must have a valid reference to the task, the
4548 * task must not exit() & deallocate itself prematurely. The
4549 * call is not atomic; no spinlocks may be held.
4551 int set_cpus_allowed(task_t
*p
, cpumask_t new_mask
)
4553 unsigned long flags
;
4555 migration_req_t req
;
4558 rq
= task_rq_lock(p
, &flags
);
4559 if (!cpus_intersects(new_mask
, cpu_online_map
)) {
4564 p
->cpus_allowed
= new_mask
;
4565 /* Can the task run on the task's current CPU? If so, we're done */
4566 if (cpu_isset(task_cpu(p
), new_mask
))
4569 if (migrate_task(p
, any_online_cpu(new_mask
), &req
)) {
4570 /* Need help from migration thread: drop lock and wait. */
4571 task_rq_unlock(rq
, &flags
);
4572 wake_up_process(rq
->migration_thread
);
4573 wait_for_completion(&req
.done
);
4574 tlb_migrate_finish(p
->mm
);
4578 task_rq_unlock(rq
, &flags
);
4582 EXPORT_SYMBOL_GPL(set_cpus_allowed
);
4585 * Move (not current) task off this cpu, onto dest cpu. We're doing
4586 * this because either it can't run here any more (set_cpus_allowed()
4587 * away from this CPU, or CPU going down), or because we're
4588 * attempting to rebalance this task on exec (sched_exec).
4590 * So we race with normal scheduler movements, but that's OK, as long
4591 * as the task is no longer on this CPU.
4593 * Returns non-zero if task was successfully migrated.
4595 static int __migrate_task(struct task_struct
*p
, int src_cpu
, int dest_cpu
)
4597 runqueue_t
*rq_dest
, *rq_src
;
4600 if (unlikely(cpu_is_offline(dest_cpu
)))
4603 rq_src
= cpu_rq(src_cpu
);
4604 rq_dest
= cpu_rq(dest_cpu
);
4606 double_rq_lock(rq_src
, rq_dest
);
4607 /* Already moved. */
4608 if (task_cpu(p
) != src_cpu
)
4610 /* Affinity changed (again). */
4611 if (!cpu_isset(dest_cpu
, p
->cpus_allowed
))
4614 set_task_cpu(p
, dest_cpu
);
4617 * Sync timestamp with rq_dest's before activating.
4618 * The same thing could be achieved by doing this step
4619 * afterwards, and pretending it was a local activate.
4620 * This way is cleaner and logically correct.
4622 p
->timestamp
= p
->timestamp
- rq_src
->timestamp_last_tick
4623 + rq_dest
->timestamp_last_tick
;
4624 deactivate_task(p
, rq_src
);
4625 activate_task(p
, rq_dest
, 0);
4626 if (TASK_PREEMPTS_CURR(p
, rq_dest
))
4627 resched_task(rq_dest
->curr
);
4631 double_rq_unlock(rq_src
, rq_dest
);
4636 * migration_thread - this is a highprio system thread that performs
4637 * thread migration by bumping thread off CPU then 'pushing' onto
4640 static int migration_thread(void *data
)
4643 int cpu
= (long)data
;
4646 BUG_ON(rq
->migration_thread
!= current
);
4648 set_current_state(TASK_INTERRUPTIBLE
);
4649 while (!kthread_should_stop()) {
4650 struct list_head
*head
;
4651 migration_req_t
*req
;
4655 spin_lock_irq(&rq
->lock
);
4657 if (cpu_is_offline(cpu
)) {
4658 spin_unlock_irq(&rq
->lock
);
4662 if (rq
->active_balance
) {
4663 active_load_balance(rq
, cpu
);
4664 rq
->active_balance
= 0;
4667 head
= &rq
->migration_queue
;
4669 if (list_empty(head
)) {
4670 spin_unlock_irq(&rq
->lock
);
4672 set_current_state(TASK_INTERRUPTIBLE
);
4675 req
= list_entry(head
->next
, migration_req_t
, list
);
4676 list_del_init(head
->next
);
4678 spin_unlock(&rq
->lock
);
4679 __migrate_task(req
->task
, cpu
, req
->dest_cpu
);
4682 complete(&req
->done
);
4684 __set_current_state(TASK_RUNNING
);
4688 /* Wait for kthread_stop */
4689 set_current_state(TASK_INTERRUPTIBLE
);
4690 while (!kthread_should_stop()) {
4692 set_current_state(TASK_INTERRUPTIBLE
);
4694 __set_current_state(TASK_RUNNING
);
4698 #ifdef CONFIG_HOTPLUG_CPU
4699 /* Figure out where task on dead CPU should go, use force if neccessary. */
4700 static void move_task_off_dead_cpu(int dead_cpu
, struct task_struct
*tsk
)
4703 unsigned long flags
;
4709 mask
= node_to_cpumask(cpu_to_node(dead_cpu
));
4710 cpus_and(mask
, mask
, tsk
->cpus_allowed
);
4711 dest_cpu
= any_online_cpu(mask
);
4713 /* On any allowed CPU? */
4714 if (dest_cpu
== NR_CPUS
)
4715 dest_cpu
= any_online_cpu(tsk
->cpus_allowed
);
4717 /* No more Mr. Nice Guy. */
4718 if (dest_cpu
== NR_CPUS
) {
4719 rq
= task_rq_lock(tsk
, &flags
);
4720 cpus_setall(tsk
->cpus_allowed
);
4721 dest_cpu
= any_online_cpu(tsk
->cpus_allowed
);
4722 task_rq_unlock(rq
, &flags
);
4725 * Don't tell them about moving exiting tasks or
4726 * kernel threads (both mm NULL), since they never
4729 if (tsk
->mm
&& printk_ratelimit())
4730 printk(KERN_INFO
"process %d (%s) no "
4731 "longer affine to cpu%d\n",
4732 tsk
->pid
, tsk
->comm
, dead_cpu
);
4734 if (!__migrate_task(tsk
, dead_cpu
, dest_cpu
))
4739 * While a dead CPU has no uninterruptible tasks queued at this point,
4740 * it might still have a nonzero ->nr_uninterruptible counter, because
4741 * for performance reasons the counter is not stricly tracking tasks to
4742 * their home CPUs. So we just add the counter to another CPU's counter,
4743 * to keep the global sum constant after CPU-down:
4745 static void migrate_nr_uninterruptible(runqueue_t
*rq_src
)
4747 runqueue_t
*rq_dest
= cpu_rq(any_online_cpu(CPU_MASK_ALL
));
4748 unsigned long flags
;
4750 local_irq_save(flags
);
4751 double_rq_lock(rq_src
, rq_dest
);
4752 rq_dest
->nr_uninterruptible
+= rq_src
->nr_uninterruptible
;
4753 rq_src
->nr_uninterruptible
= 0;
4754 double_rq_unlock(rq_src
, rq_dest
);
4755 local_irq_restore(flags
);
4758 /* Run through task list and migrate tasks from the dead cpu. */
4759 static void migrate_live_tasks(int src_cpu
)
4761 struct task_struct
*tsk
, *t
;
4763 write_lock_irq(&tasklist_lock
);
4765 do_each_thread(t
, tsk
) {
4769 if (task_cpu(tsk
) == src_cpu
)
4770 move_task_off_dead_cpu(src_cpu
, tsk
);
4771 } while_each_thread(t
, tsk
);
4773 write_unlock_irq(&tasklist_lock
);
4776 /* Schedules idle task to be the next runnable task on current CPU.
4777 * It does so by boosting its priority to highest possible and adding it to
4778 * the _front_ of runqueue. Used by CPU offline code.
4780 void sched_idle_next(void)
4782 int cpu
= smp_processor_id();
4783 runqueue_t
*rq
= this_rq();
4784 struct task_struct
*p
= rq
->idle
;
4785 unsigned long flags
;
4787 /* cpu has to be offline */
4788 BUG_ON(cpu_online(cpu
));
4790 /* Strictly not necessary since rest of the CPUs are stopped by now
4791 * and interrupts disabled on current cpu.
4793 spin_lock_irqsave(&rq
->lock
, flags
);
4795 __setscheduler(p
, SCHED_FIFO
, MAX_RT_PRIO
-1);
4796 /* Add idle task to _front_ of it's priority queue */
4797 __activate_idle_task(p
, rq
);
4799 spin_unlock_irqrestore(&rq
->lock
, flags
);
4802 /* Ensures that the idle task is using init_mm right before its cpu goes
4805 void idle_task_exit(void)
4807 struct mm_struct
*mm
= current
->active_mm
;
4809 BUG_ON(cpu_online(smp_processor_id()));
4812 switch_mm(mm
, &init_mm
, current
);
4816 static void migrate_dead(unsigned int dead_cpu
, task_t
*tsk
)
4818 struct runqueue
*rq
= cpu_rq(dead_cpu
);
4820 /* Must be exiting, otherwise would be on tasklist. */
4821 BUG_ON(tsk
->exit_state
!= EXIT_ZOMBIE
&& tsk
->exit_state
!= EXIT_DEAD
);
4823 /* Cannot have done final schedule yet: would have vanished. */
4824 BUG_ON(tsk
->flags
& PF_DEAD
);
4826 get_task_struct(tsk
);
4829 * Drop lock around migration; if someone else moves it,
4830 * that's OK. No task can be added to this CPU, so iteration is
4833 spin_unlock_irq(&rq
->lock
);
4834 move_task_off_dead_cpu(dead_cpu
, tsk
);
4835 spin_lock_irq(&rq
->lock
);
4837 put_task_struct(tsk
);
4840 /* release_task() removes task from tasklist, so we won't find dead tasks. */
4841 static void migrate_dead_tasks(unsigned int dead_cpu
)
4844 struct runqueue
*rq
= cpu_rq(dead_cpu
);
4846 for (arr
= 0; arr
< 2; arr
++) {
4847 for (i
= 0; i
< MAX_PRIO
; i
++) {
4848 struct list_head
*list
= &rq
->arrays
[arr
].queue
[i
];
4849 while (!list_empty(list
))
4850 migrate_dead(dead_cpu
,
4851 list_entry(list
->next
, task_t
,
4856 #endif /* CONFIG_HOTPLUG_CPU */
4859 * migration_call - callback that gets triggered when a CPU is added.
4860 * Here we can start up the necessary migration thread for the new CPU.
4862 static int __cpuinit
migration_call(struct notifier_block
*nfb
,
4863 unsigned long action
,
4866 int cpu
= (long)hcpu
;
4867 struct task_struct
*p
;
4868 struct runqueue
*rq
;
4869 unsigned long flags
;
4872 case CPU_UP_PREPARE
:
4873 p
= kthread_create(migration_thread
, hcpu
, "migration/%d",cpu
);
4876 p
->flags
|= PF_NOFREEZE
;
4877 kthread_bind(p
, cpu
);
4878 /* Must be high prio: stop_machine expects to yield to it. */
4879 rq
= task_rq_lock(p
, &flags
);
4880 __setscheduler(p
, SCHED_FIFO
, MAX_RT_PRIO
-1);
4881 task_rq_unlock(rq
, &flags
);
4882 cpu_rq(cpu
)->migration_thread
= p
;
4885 /* Strictly unneccessary, as first user will wake it. */
4886 wake_up_process(cpu_rq(cpu
)->migration_thread
);
4888 #ifdef CONFIG_HOTPLUG_CPU
4889 case CPU_UP_CANCELED
:
4890 if (!cpu_rq(cpu
)->migration_thread
)
4892 /* Unbind it from offline cpu so it can run. Fall thru. */
4893 kthread_bind(cpu_rq(cpu
)->migration_thread
,
4894 any_online_cpu(cpu_online_map
));
4895 kthread_stop(cpu_rq(cpu
)->migration_thread
);
4896 cpu_rq(cpu
)->migration_thread
= NULL
;
4899 migrate_live_tasks(cpu
);
4901 kthread_stop(rq
->migration_thread
);
4902 rq
->migration_thread
= NULL
;
4903 /* Idle task back to normal (off runqueue, low prio) */
4904 rq
= task_rq_lock(rq
->idle
, &flags
);
4905 deactivate_task(rq
->idle
, rq
);
4906 rq
->idle
->static_prio
= MAX_PRIO
;
4907 __setscheduler(rq
->idle
, SCHED_NORMAL
, 0);
4908 migrate_dead_tasks(cpu
);
4909 task_rq_unlock(rq
, &flags
);
4910 migrate_nr_uninterruptible(rq
);
4911 BUG_ON(rq
->nr_running
!= 0);
4913 /* No need to migrate the tasks: it was best-effort if
4914 * they didn't do lock_cpu_hotplug(). Just wake up
4915 * the requestors. */
4916 spin_lock_irq(&rq
->lock
);
4917 while (!list_empty(&rq
->migration_queue
)) {
4918 migration_req_t
*req
;
4919 req
= list_entry(rq
->migration_queue
.next
,
4920 migration_req_t
, list
);
4921 list_del_init(&req
->list
);
4922 complete(&req
->done
);
4924 spin_unlock_irq(&rq
->lock
);
4931 /* Register at highest priority so that task migration (migrate_all_tasks)
4932 * happens before everything else.
4934 static struct notifier_block __cpuinitdata migration_notifier
= {
4935 .notifier_call
= migration_call
,
4939 int __init
migration_init(void)
4941 void *cpu
= (void *)(long)smp_processor_id();
4942 /* Start one for boot CPU. */
4943 migration_call(&migration_notifier
, CPU_UP_PREPARE
, cpu
);
4944 migration_call(&migration_notifier
, CPU_ONLINE
, cpu
);
4945 register_cpu_notifier(&migration_notifier
);
4951 #undef SCHED_DOMAIN_DEBUG
4952 #ifdef SCHED_DOMAIN_DEBUG
4953 static void sched_domain_debug(struct sched_domain
*sd
, int cpu
)
4958 printk(KERN_DEBUG
"CPU%d attaching NULL sched-domain.\n", cpu
);
4962 printk(KERN_DEBUG
"CPU%d attaching sched-domain:\n", cpu
);
4967 struct sched_group
*group
= sd
->groups
;
4968 cpumask_t groupmask
;
4970 cpumask_scnprintf(str
, NR_CPUS
, sd
->span
);
4971 cpus_clear(groupmask
);
4974 for (i
= 0; i
< level
+ 1; i
++)
4976 printk("domain %d: ", level
);
4978 if (!(sd
->flags
& SD_LOAD_BALANCE
)) {
4979 printk("does not load-balance\n");
4981 printk(KERN_ERR
"ERROR: !SD_LOAD_BALANCE domain has parent");
4985 printk("span %s\n", str
);
4987 if (!cpu_isset(cpu
, sd
->span
))
4988 printk(KERN_ERR
"ERROR: domain->span does not contain CPU%d\n", cpu
);
4989 if (!cpu_isset(cpu
, group
->cpumask
))
4990 printk(KERN_ERR
"ERROR: domain->groups does not contain CPU%d\n", cpu
);
4993 for (i
= 0; i
< level
+ 2; i
++)
4999 printk(KERN_ERR
"ERROR: group is NULL\n");
5003 if (!group
->cpu_power
) {
5005 printk(KERN_ERR
"ERROR: domain->cpu_power not set\n");
5008 if (!cpus_weight(group
->cpumask
)) {
5010 printk(KERN_ERR
"ERROR: empty group\n");
5013 if (cpus_intersects(groupmask
, group
->cpumask
)) {
5015 printk(KERN_ERR
"ERROR: repeated CPUs\n");
5018 cpus_or(groupmask
, groupmask
, group
->cpumask
);
5020 cpumask_scnprintf(str
, NR_CPUS
, group
->cpumask
);
5023 group
= group
->next
;
5024 } while (group
!= sd
->groups
);
5027 if (!cpus_equal(sd
->span
, groupmask
))
5028 printk(KERN_ERR
"ERROR: groups don't span domain->span\n");
5034 if (!cpus_subset(groupmask
, sd
->span
))
5035 printk(KERN_ERR
"ERROR: parent span is not a superset of domain->span\n");
5041 #define sched_domain_debug(sd, cpu) {}
5044 static int sd_degenerate(struct sched_domain
*sd
)
5046 if (cpus_weight(sd
->span
) == 1)
5049 /* Following flags need at least 2 groups */
5050 if (sd
->flags
& (SD_LOAD_BALANCE
|
5051 SD_BALANCE_NEWIDLE
|
5054 if (sd
->groups
!= sd
->groups
->next
)
5058 /* Following flags don't use groups */
5059 if (sd
->flags
& (SD_WAKE_IDLE
|
5067 static int sd_parent_degenerate(struct sched_domain
*sd
,
5068 struct sched_domain
*parent
)
5070 unsigned long cflags
= sd
->flags
, pflags
= parent
->flags
;
5072 if (sd_degenerate(parent
))
5075 if (!cpus_equal(sd
->span
, parent
->span
))
5078 /* Does parent contain flags not in child? */
5079 /* WAKE_BALANCE is a subset of WAKE_AFFINE */
5080 if (cflags
& SD_WAKE_AFFINE
)
5081 pflags
&= ~SD_WAKE_BALANCE
;
5082 /* Flags needing groups don't count if only 1 group in parent */
5083 if (parent
->groups
== parent
->groups
->next
) {
5084 pflags
&= ~(SD_LOAD_BALANCE
|
5085 SD_BALANCE_NEWIDLE
|
5089 if (~cflags
& pflags
)
5096 * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
5097 * hold the hotplug lock.
5099 static void cpu_attach_domain(struct sched_domain
*sd
, int cpu
)
5101 runqueue_t
*rq
= cpu_rq(cpu
);
5102 struct sched_domain
*tmp
;
5104 /* Remove the sched domains which do not contribute to scheduling. */
5105 for (tmp
= sd
; tmp
; tmp
= tmp
->parent
) {
5106 struct sched_domain
*parent
= tmp
->parent
;
5109 if (sd_parent_degenerate(tmp
, parent
))
5110 tmp
->parent
= parent
->parent
;
5113 if (sd
&& sd_degenerate(sd
))
5116 sched_domain_debug(sd
, cpu
);
5118 rcu_assign_pointer(rq
->sd
, sd
);
5121 /* cpus with isolated domains */
5122 static cpumask_t __devinitdata cpu_isolated_map
= CPU_MASK_NONE
;
5124 /* Setup the mask of cpus configured for isolated domains */
5125 static int __init
isolated_cpu_setup(char *str
)
5127 int ints
[NR_CPUS
], i
;
5129 str
= get_options(str
, ARRAY_SIZE(ints
), ints
);
5130 cpus_clear(cpu_isolated_map
);
5131 for (i
= 1; i
<= ints
[0]; i
++)
5132 if (ints
[i
] < NR_CPUS
)
5133 cpu_set(ints
[i
], cpu_isolated_map
);
5137 __setup ("isolcpus=", isolated_cpu_setup
);
5140 * init_sched_build_groups takes an array of groups, the cpumask we wish
5141 * to span, and a pointer to a function which identifies what group a CPU
5142 * belongs to. The return value of group_fn must be a valid index into the
5143 * groups[] array, and must be >= 0 and < NR_CPUS (due to the fact that we
5144 * keep track of groups covered with a cpumask_t).
5146 * init_sched_build_groups will build a circular linked list of the groups
5147 * covered by the given span, and will set each group's ->cpumask correctly,
5148 * and ->cpu_power to 0.
5150 static void init_sched_build_groups(struct sched_group groups
[], cpumask_t span
,
5151 int (*group_fn
)(int cpu
))
5153 struct sched_group
*first
= NULL
, *last
= NULL
;
5154 cpumask_t covered
= CPU_MASK_NONE
;
5157 for_each_cpu_mask(i
, span
) {
5158 int group
= group_fn(i
);
5159 struct sched_group
*sg
= &groups
[group
];
5162 if (cpu_isset(i
, covered
))
5165 sg
->cpumask
= CPU_MASK_NONE
;
5168 for_each_cpu_mask(j
, span
) {
5169 if (group_fn(j
) != group
)
5172 cpu_set(j
, covered
);
5173 cpu_set(j
, sg
->cpumask
);
5184 #define SD_NODES_PER_DOMAIN 16
5187 * Self-tuning task migration cost measurement between source and target CPUs.
5189 * This is done by measuring the cost of manipulating buffers of varying
5190 * sizes. For a given buffer-size here are the steps that are taken:
5192 * 1) the source CPU reads+dirties a shared buffer
5193 * 2) the target CPU reads+dirties the same shared buffer
5195 * We measure how long they take, in the following 4 scenarios:
5197 * - source: CPU1, target: CPU2 | cost1
5198 * - source: CPU2, target: CPU1 | cost2
5199 * - source: CPU1, target: CPU1 | cost3
5200 * - source: CPU2, target: CPU2 | cost4
5202 * We then calculate the cost3+cost4-cost1-cost2 difference - this is
5203 * the cost of migration.
5205 * We then start off from a small buffer-size and iterate up to larger
5206 * buffer sizes, in 5% steps - measuring each buffer-size separately, and
5207 * doing a maximum search for the cost. (The maximum cost for a migration
5208 * normally occurs when the working set size is around the effective cache
5211 #define SEARCH_SCOPE 2
5212 #define MIN_CACHE_SIZE (64*1024U)
5213 #define DEFAULT_CACHE_SIZE (5*1024*1024U)
5214 #define ITERATIONS 1
5215 #define SIZE_THRESH 130
5216 #define COST_THRESH 130
5219 * The migration cost is a function of 'domain distance'. Domain
5220 * distance is the number of steps a CPU has to iterate down its
5221 * domain tree to share a domain with the other CPU. The farther
5222 * two CPUs are from each other, the larger the distance gets.
5224 * Note that we use the distance only to cache measurement results,
5225 * the distance value is not used numerically otherwise. When two
5226 * CPUs have the same distance it is assumed that the migration
5227 * cost is the same. (this is a simplification but quite practical)
5229 #define MAX_DOMAIN_DISTANCE 32
5231 static unsigned long long migration_cost
[MAX_DOMAIN_DISTANCE
] =
5232 { [ 0 ... MAX_DOMAIN_DISTANCE
-1 ] =
5234 * Architectures may override the migration cost and thus avoid
5235 * boot-time calibration. Unit is nanoseconds. Mostly useful for
5236 * virtualized hardware:
5238 #ifdef CONFIG_DEFAULT_MIGRATION_COST
5239 CONFIG_DEFAULT_MIGRATION_COST
5246 * Allow override of migration cost - in units of microseconds.
5247 * E.g. migration_cost=1000,2000,3000 will set up a level-1 cost
5248 * of 1 msec, level-2 cost of 2 msecs and level3 cost of 3 msecs:
5250 static int __init
migration_cost_setup(char *str
)
5252 int ints
[MAX_DOMAIN_DISTANCE
+1], i
;
5254 str
= get_options(str
, ARRAY_SIZE(ints
), ints
);
5256 printk("#ints: %d\n", ints
[0]);
5257 for (i
= 1; i
<= ints
[0]; i
++) {
5258 migration_cost
[i
-1] = (unsigned long long)ints
[i
]*1000;
5259 printk("migration_cost[%d]: %Ld\n", i
-1, migration_cost
[i
-1]);
5264 __setup ("migration_cost=", migration_cost_setup
);
5267 * Global multiplier (divisor) for migration-cutoff values,
5268 * in percentiles. E.g. use a value of 150 to get 1.5 times
5269 * longer cache-hot cutoff times.
5271 * (We scale it from 100 to 128 to long long handling easier.)
5274 #define MIGRATION_FACTOR_SCALE 128
5276 static unsigned int migration_factor
= MIGRATION_FACTOR_SCALE
;
5278 static int __init
setup_migration_factor(char *str
)
5280 get_option(&str
, &migration_factor
);
5281 migration_factor
= migration_factor
* MIGRATION_FACTOR_SCALE
/ 100;
5285 __setup("migration_factor=", setup_migration_factor
);
5288 * Estimated distance of two CPUs, measured via the number of domains
5289 * we have to pass for the two CPUs to be in the same span:
5291 static unsigned long domain_distance(int cpu1
, int cpu2
)
5293 unsigned long distance
= 0;
5294 struct sched_domain
*sd
;
5296 for_each_domain(cpu1
, sd
) {
5297 WARN_ON(!cpu_isset(cpu1
, sd
->span
));
5298 if (cpu_isset(cpu2
, sd
->span
))
5302 if (distance
>= MAX_DOMAIN_DISTANCE
) {
5304 distance
= MAX_DOMAIN_DISTANCE
-1;
5310 static unsigned int migration_debug
;
5312 static int __init
setup_migration_debug(char *str
)
5314 get_option(&str
, &migration_debug
);
5318 __setup("migration_debug=", setup_migration_debug
);
5321 * Maximum cache-size that the scheduler should try to measure.
5322 * Architectures with larger caches should tune this up during
5323 * bootup. Gets used in the domain-setup code (i.e. during SMP
5326 unsigned int max_cache_size
;
5328 static int __init
setup_max_cache_size(char *str
)
5330 get_option(&str
, &max_cache_size
);
5334 __setup("max_cache_size=", setup_max_cache_size
);
5337 * Dirty a big buffer in a hard-to-predict (for the L2 cache) way. This
5338 * is the operation that is timed, so we try to generate unpredictable
5339 * cachemisses that still end up filling the L2 cache:
5341 static void touch_cache(void *__cache
, unsigned long __size
)
5343 unsigned long size
= __size
/sizeof(long), chunk1
= size
/3,
5345 unsigned long *cache
= __cache
;
5348 for (i
= 0; i
< size
/6; i
+= 8) {
5351 case 1: cache
[size
-1-i
]++;
5352 case 2: cache
[chunk1
-i
]++;
5353 case 3: cache
[chunk1
+i
]++;
5354 case 4: cache
[chunk2
-i
]++;
5355 case 5: cache
[chunk2
+i
]++;
5361 * Measure the cache-cost of one task migration. Returns in units of nsec.
5363 static unsigned long long measure_one(void *cache
, unsigned long size
,
5364 int source
, int target
)
5366 cpumask_t mask
, saved_mask
;
5367 unsigned long long t0
, t1
, t2
, t3
, cost
;
5369 saved_mask
= current
->cpus_allowed
;
5372 * Flush source caches to RAM and invalidate them:
5377 * Migrate to the source CPU:
5379 mask
= cpumask_of_cpu(source
);
5380 set_cpus_allowed(current
, mask
);
5381 WARN_ON(smp_processor_id() != source
);
5384 * Dirty the working set:
5387 touch_cache(cache
, size
);
5391 * Migrate to the target CPU, dirty the L2 cache and access
5392 * the shared buffer. (which represents the working set
5393 * of a migrated task.)
5395 mask
= cpumask_of_cpu(target
);
5396 set_cpus_allowed(current
, mask
);
5397 WARN_ON(smp_processor_id() != target
);
5400 touch_cache(cache
, size
);
5403 cost
= t1
-t0
+ t3
-t2
;
5405 if (migration_debug
>= 2)
5406 printk("[%d->%d]: %8Ld %8Ld %8Ld => %10Ld.\n",
5407 source
, target
, t1
-t0
, t1
-t0
, t3
-t2
, cost
);
5409 * Flush target caches to RAM and invalidate them:
5413 set_cpus_allowed(current
, saved_mask
);
5419 * Measure a series of task migrations and return the average
5420 * result. Since this code runs early during bootup the system
5421 * is 'undisturbed' and the average latency makes sense.
5423 * The algorithm in essence auto-detects the relevant cache-size,
5424 * so it will properly detect different cachesizes for different
5425 * cache-hierarchies, depending on how the CPUs are connected.
5427 * Architectures can prime the upper limit of the search range via
5428 * max_cache_size, otherwise the search range defaults to 20MB...64K.
5430 static unsigned long long
5431 measure_cost(int cpu1
, int cpu2
, void *cache
, unsigned int size
)
5433 unsigned long long cost1
, cost2
;
5437 * Measure the migration cost of 'size' bytes, over an
5438 * average of 10 runs:
5440 * (We perturb the cache size by a small (0..4k)
5441 * value to compensate size/alignment related artifacts.
5442 * We also subtract the cost of the operation done on
5448 * dry run, to make sure we start off cache-cold on cpu1,
5449 * and to get any vmalloc pagefaults in advance:
5451 measure_one(cache
, size
, cpu1
, cpu2
);
5452 for (i
= 0; i
< ITERATIONS
; i
++)
5453 cost1
+= measure_one(cache
, size
- i
*1024, cpu1
, cpu2
);
5455 measure_one(cache
, size
, cpu2
, cpu1
);
5456 for (i
= 0; i
< ITERATIONS
; i
++)
5457 cost1
+= measure_one(cache
, size
- i
*1024, cpu2
, cpu1
);
5460 * (We measure the non-migrating [cached] cost on both
5461 * cpu1 and cpu2, to handle CPUs with different speeds)
5465 measure_one(cache
, size
, cpu1
, cpu1
);
5466 for (i
= 0; i
< ITERATIONS
; i
++)
5467 cost2
+= measure_one(cache
, size
- i
*1024, cpu1
, cpu1
);
5469 measure_one(cache
, size
, cpu2
, cpu2
);
5470 for (i
= 0; i
< ITERATIONS
; i
++)
5471 cost2
+= measure_one(cache
, size
- i
*1024, cpu2
, cpu2
);
5474 * Get the per-iteration migration cost:
5476 do_div(cost1
, 2*ITERATIONS
);
5477 do_div(cost2
, 2*ITERATIONS
);
5479 return cost1
- cost2
;
5482 static unsigned long long measure_migration_cost(int cpu1
, int cpu2
)
5484 unsigned long long max_cost
= 0, fluct
= 0, avg_fluct
= 0;
5485 unsigned int max_size
, size
, size_found
= 0;
5486 long long cost
= 0, prev_cost
;
5490 * Search from max_cache_size*5 down to 64K - the real relevant
5491 * cachesize has to lie somewhere inbetween.
5493 if (max_cache_size
) {
5494 max_size
= max(max_cache_size
* SEARCH_SCOPE
, MIN_CACHE_SIZE
);
5495 size
= max(max_cache_size
/ SEARCH_SCOPE
, MIN_CACHE_SIZE
);
5498 * Since we have no estimation about the relevant
5501 max_size
= DEFAULT_CACHE_SIZE
* SEARCH_SCOPE
;
5502 size
= MIN_CACHE_SIZE
;
5505 if (!cpu_online(cpu1
) || !cpu_online(cpu2
)) {
5506 printk("cpu %d and %d not both online!\n", cpu1
, cpu2
);
5511 * Allocate the working set:
5513 cache
= vmalloc(max_size
);
5515 printk("could not vmalloc %d bytes for cache!\n", 2*max_size
);
5516 return 1000000; // return 1 msec on very small boxen
5519 while (size
<= max_size
) {
5521 cost
= measure_cost(cpu1
, cpu2
, cache
, size
);
5527 if (max_cost
< cost
) {
5533 * Calculate average fluctuation, we use this to prevent
5534 * noise from triggering an early break out of the loop:
5536 fluct
= abs(cost
- prev_cost
);
5537 avg_fluct
= (avg_fluct
+ fluct
)/2;
5539 if (migration_debug
)
5540 printk("-> [%d][%d][%7d] %3ld.%ld [%3ld.%ld] (%ld): (%8Ld %8Ld)\n",
5542 (long)cost
/ 1000000,
5543 ((long)cost
/ 100000) % 10,
5544 (long)max_cost
/ 1000000,
5545 ((long)max_cost
/ 100000) % 10,
5546 domain_distance(cpu1
, cpu2
),
5550 * If we iterated at least 20% past the previous maximum,
5551 * and the cost has dropped by more than 20% already,
5552 * (taking fluctuations into account) then we assume to
5553 * have found the maximum and break out of the loop early:
5555 if (size_found
&& (size
*100 > size_found
*SIZE_THRESH
))
5556 if (cost
+avg_fluct
<= 0 ||
5557 max_cost
*100 > (cost
+avg_fluct
)*COST_THRESH
) {
5559 if (migration_debug
)
5560 printk("-> found max.\n");
5564 * Increase the cachesize in 10% steps:
5566 size
= size
* 10 / 9;
5569 if (migration_debug
)
5570 printk("[%d][%d] working set size found: %d, cost: %Ld\n",
5571 cpu1
, cpu2
, size_found
, max_cost
);
5576 * A task is considered 'cache cold' if at least 2 times
5577 * the worst-case cost of migration has passed.
5579 * (this limit is only listened to if the load-balancing
5580 * situation is 'nice' - if there is a large imbalance we
5581 * ignore it for the sake of CPU utilization and
5582 * processing fairness.)
5584 return 2 * max_cost
* migration_factor
/ MIGRATION_FACTOR_SCALE
;
5587 static void calibrate_migration_costs(const cpumask_t
*cpu_map
)
5589 int cpu1
= -1, cpu2
= -1, cpu
, orig_cpu
= raw_smp_processor_id();
5590 unsigned long j0
, j1
, distance
, max_distance
= 0;
5591 struct sched_domain
*sd
;
5596 * First pass - calculate the cacheflush times:
5598 for_each_cpu_mask(cpu1
, *cpu_map
) {
5599 for_each_cpu_mask(cpu2
, *cpu_map
) {
5602 distance
= domain_distance(cpu1
, cpu2
);
5603 max_distance
= max(max_distance
, distance
);
5605 * No result cached yet?
5607 if (migration_cost
[distance
] == -1LL)
5608 migration_cost
[distance
] =
5609 measure_migration_cost(cpu1
, cpu2
);
5613 * Second pass - update the sched domain hierarchy with
5614 * the new cache-hot-time estimations:
5616 for_each_cpu_mask(cpu
, *cpu_map
) {
5618 for_each_domain(cpu
, sd
) {
5619 sd
->cache_hot_time
= migration_cost
[distance
];
5626 if (migration_debug
)
5627 printk("migration: max_cache_size: %d, cpu: %d MHz:\n",
5635 if (system_state
== SYSTEM_BOOTING
) {
5636 printk("migration_cost=");
5637 for (distance
= 0; distance
<= max_distance
; distance
++) {
5640 printk("%ld", (long)migration_cost
[distance
] / 1000);
5645 if (migration_debug
)
5646 printk("migration: %ld seconds\n", (j1
-j0
)/HZ
);
5649 * Move back to the original CPU. NUMA-Q gets confused
5650 * if we migrate to another quad during bootup.
5652 if (raw_smp_processor_id() != orig_cpu
) {
5653 cpumask_t mask
= cpumask_of_cpu(orig_cpu
),
5654 saved_mask
= current
->cpus_allowed
;
5656 set_cpus_allowed(current
, mask
);
5657 set_cpus_allowed(current
, saved_mask
);
5664 * find_next_best_node - find the next node to include in a sched_domain
5665 * @node: node whose sched_domain we're building
5666 * @used_nodes: nodes already in the sched_domain
5668 * Find the next node to include in a given scheduling domain. Simply
5669 * finds the closest node not already in the @used_nodes map.
5671 * Should use nodemask_t.
5673 static int find_next_best_node(int node
, unsigned long *used_nodes
)
5675 int i
, n
, val
, min_val
, best_node
= 0;
5679 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
5680 /* Start at @node */
5681 n
= (node
+ i
) % MAX_NUMNODES
;
5683 if (!nr_cpus_node(n
))
5686 /* Skip already used nodes */
5687 if (test_bit(n
, used_nodes
))
5690 /* Simple min distance search */
5691 val
= node_distance(node
, n
);
5693 if (val
< min_val
) {
5699 set_bit(best_node
, used_nodes
);
5704 * sched_domain_node_span - get a cpumask for a node's sched_domain
5705 * @node: node whose cpumask we're constructing
5706 * @size: number of nodes to include in this span
5708 * Given a node, construct a good cpumask for its sched_domain to span. It
5709 * should be one that prevents unnecessary balancing, but also spreads tasks
5712 static cpumask_t
sched_domain_node_span(int node
)
5715 cpumask_t span
, nodemask
;
5716 DECLARE_BITMAP(used_nodes
, MAX_NUMNODES
);
5719 bitmap_zero(used_nodes
, MAX_NUMNODES
);
5721 nodemask
= node_to_cpumask(node
);
5722 cpus_or(span
, span
, nodemask
);
5723 set_bit(node
, used_nodes
);
5725 for (i
= 1; i
< SD_NODES_PER_DOMAIN
; i
++) {
5726 int next_node
= find_next_best_node(node
, used_nodes
);
5727 nodemask
= node_to_cpumask(next_node
);
5728 cpus_or(span
, span
, nodemask
);
5736 * At the moment, CONFIG_SCHED_SMT is never defined, but leave it in so we
5737 * can switch it on easily if needed.
5739 #ifdef CONFIG_SCHED_SMT
5740 static DEFINE_PER_CPU(struct sched_domain
, cpu_domains
);
5741 static struct sched_group sched_group_cpus
[NR_CPUS
];
5742 static int cpu_to_cpu_group(int cpu
)
5748 #ifdef CONFIG_SCHED_MC
5749 static DEFINE_PER_CPU(struct sched_domain
, core_domains
);
5750 static struct sched_group sched_group_core
[NR_CPUS
];
5753 #if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
5754 static int cpu_to_core_group(int cpu
)
5756 return first_cpu(cpu_sibling_map
[cpu
]);
5758 #elif defined(CONFIG_SCHED_MC)
5759 static int cpu_to_core_group(int cpu
)
5765 static DEFINE_PER_CPU(struct sched_domain
, phys_domains
);
5766 static struct sched_group sched_group_phys
[NR_CPUS
];
5767 static int cpu_to_phys_group(int cpu
)
5769 #if defined(CONFIG_SCHED_MC)
5770 cpumask_t mask
= cpu_coregroup_map(cpu
);
5771 return first_cpu(mask
);
5772 #elif defined(CONFIG_SCHED_SMT)
5773 return first_cpu(cpu_sibling_map
[cpu
]);
5781 * The init_sched_build_groups can't handle what we want to do with node
5782 * groups, so roll our own. Now each node has its own list of groups which
5783 * gets dynamically allocated.
5785 static DEFINE_PER_CPU(struct sched_domain
, node_domains
);
5786 static struct sched_group
**sched_group_nodes_bycpu
[NR_CPUS
];
5788 static DEFINE_PER_CPU(struct sched_domain
, allnodes_domains
);
5789 static struct sched_group
*sched_group_allnodes_bycpu
[NR_CPUS
];
5791 static int cpu_to_allnodes_group(int cpu
)
5793 return cpu_to_node(cpu
);
5795 static void init_numa_sched_groups_power(struct sched_group
*group_head
)
5797 struct sched_group
*sg
= group_head
;
5803 for_each_cpu_mask(j
, sg
->cpumask
) {
5804 struct sched_domain
*sd
;
5806 sd
= &per_cpu(phys_domains
, j
);
5807 if (j
!= first_cpu(sd
->groups
->cpumask
)) {
5809 * Only add "power" once for each
5815 sg
->cpu_power
+= sd
->groups
->cpu_power
;
5818 if (sg
!= group_head
)
5823 /* Free memory allocated for various sched_group structures */
5824 static void free_sched_groups(const cpumask_t
*cpu_map
)
5830 for_each_cpu_mask(cpu
, *cpu_map
) {
5831 struct sched_group
*sched_group_allnodes
5832 = sched_group_allnodes_bycpu
[cpu
];
5833 struct sched_group
**sched_group_nodes
5834 = sched_group_nodes_bycpu
[cpu
];
5836 if (sched_group_allnodes
) {
5837 kfree(sched_group_allnodes
);
5838 sched_group_allnodes_bycpu
[cpu
] = NULL
;
5841 if (!sched_group_nodes
)
5844 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
5845 cpumask_t nodemask
= node_to_cpumask(i
);
5846 struct sched_group
*oldsg
, *sg
= sched_group_nodes
[i
];
5848 cpus_and(nodemask
, nodemask
, *cpu_map
);
5849 if (cpus_empty(nodemask
))
5859 if (oldsg
!= sched_group_nodes
[i
])
5862 kfree(sched_group_nodes
);
5863 sched_group_nodes_bycpu
[cpu
] = NULL
;
5869 * Build sched domains for a given set of cpus and attach the sched domains
5870 * to the individual cpus
5872 static int build_sched_domains(const cpumask_t
*cpu_map
)
5876 struct sched_group
**sched_group_nodes
= NULL
;
5877 struct sched_group
*sched_group_allnodes
= NULL
;
5880 * Allocate the per-node list of sched groups
5882 sched_group_nodes
= kzalloc(sizeof(struct sched_group
*)*MAX_NUMNODES
,
5884 if (!sched_group_nodes
) {
5885 printk(KERN_WARNING
"Can not alloc sched group node list\n");
5888 sched_group_nodes_bycpu
[first_cpu(*cpu_map
)] = sched_group_nodes
;
5892 * Set up domains for cpus specified by the cpu_map.
5894 for_each_cpu_mask(i
, *cpu_map
) {
5896 struct sched_domain
*sd
= NULL
, *p
;
5897 cpumask_t nodemask
= node_to_cpumask(cpu_to_node(i
));
5899 cpus_and(nodemask
, nodemask
, *cpu_map
);
5902 if (cpus_weight(*cpu_map
)
5903 > SD_NODES_PER_DOMAIN
*cpus_weight(nodemask
)) {
5904 if (!sched_group_allnodes
) {
5905 sched_group_allnodes
5906 = kmalloc(sizeof(struct sched_group
)
5909 if (!sched_group_allnodes
) {
5911 "Can not alloc allnodes sched group\n");
5914 sched_group_allnodes_bycpu
[i
]
5915 = sched_group_allnodes
;
5917 sd
= &per_cpu(allnodes_domains
, i
);
5918 *sd
= SD_ALLNODES_INIT
;
5919 sd
->span
= *cpu_map
;
5920 group
= cpu_to_allnodes_group(i
);
5921 sd
->groups
= &sched_group_allnodes
[group
];
5926 sd
= &per_cpu(node_domains
, i
);
5928 sd
->span
= sched_domain_node_span(cpu_to_node(i
));
5930 cpus_and(sd
->span
, sd
->span
, *cpu_map
);
5934 sd
= &per_cpu(phys_domains
, i
);
5935 group
= cpu_to_phys_group(i
);
5937 sd
->span
= nodemask
;
5939 sd
->groups
= &sched_group_phys
[group
];
5941 #ifdef CONFIG_SCHED_MC
5943 sd
= &per_cpu(core_domains
, i
);
5944 group
= cpu_to_core_group(i
);
5946 sd
->span
= cpu_coregroup_map(i
);
5947 cpus_and(sd
->span
, sd
->span
, *cpu_map
);
5949 sd
->groups
= &sched_group_core
[group
];
5952 #ifdef CONFIG_SCHED_SMT
5954 sd
= &per_cpu(cpu_domains
, i
);
5955 group
= cpu_to_cpu_group(i
);
5956 *sd
= SD_SIBLING_INIT
;
5957 sd
->span
= cpu_sibling_map
[i
];
5958 cpus_and(sd
->span
, sd
->span
, *cpu_map
);
5960 sd
->groups
= &sched_group_cpus
[group
];
5964 #ifdef CONFIG_SCHED_SMT
5965 /* Set up CPU (sibling) groups */
5966 for_each_cpu_mask(i
, *cpu_map
) {
5967 cpumask_t this_sibling_map
= cpu_sibling_map
[i
];
5968 cpus_and(this_sibling_map
, this_sibling_map
, *cpu_map
);
5969 if (i
!= first_cpu(this_sibling_map
))
5972 init_sched_build_groups(sched_group_cpus
, this_sibling_map
,
5977 #ifdef CONFIG_SCHED_MC
5978 /* Set up multi-core groups */
5979 for_each_cpu_mask(i
, *cpu_map
) {
5980 cpumask_t this_core_map
= cpu_coregroup_map(i
);
5981 cpus_and(this_core_map
, this_core_map
, *cpu_map
);
5982 if (i
!= first_cpu(this_core_map
))
5984 init_sched_build_groups(sched_group_core
, this_core_map
,
5985 &cpu_to_core_group
);
5990 /* Set up physical groups */
5991 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
5992 cpumask_t nodemask
= node_to_cpumask(i
);
5994 cpus_and(nodemask
, nodemask
, *cpu_map
);
5995 if (cpus_empty(nodemask
))
5998 init_sched_build_groups(sched_group_phys
, nodemask
,
5999 &cpu_to_phys_group
);
6003 /* Set up node groups */
6004 if (sched_group_allnodes
)
6005 init_sched_build_groups(sched_group_allnodes
, *cpu_map
,
6006 &cpu_to_allnodes_group
);
6008 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
6009 /* Set up node groups */
6010 struct sched_group
*sg
, *prev
;
6011 cpumask_t nodemask
= node_to_cpumask(i
);
6012 cpumask_t domainspan
;
6013 cpumask_t covered
= CPU_MASK_NONE
;
6016 cpus_and(nodemask
, nodemask
, *cpu_map
);
6017 if (cpus_empty(nodemask
)) {
6018 sched_group_nodes
[i
] = NULL
;
6022 domainspan
= sched_domain_node_span(i
);
6023 cpus_and(domainspan
, domainspan
, *cpu_map
);
6025 sg
= kmalloc(sizeof(struct sched_group
), GFP_KERNEL
);
6027 printk(KERN_WARNING
"Can not alloc domain group for "
6031 sched_group_nodes
[i
] = sg
;
6032 for_each_cpu_mask(j
, nodemask
) {
6033 struct sched_domain
*sd
;
6034 sd
= &per_cpu(node_domains
, j
);
6038 sg
->cpumask
= nodemask
;
6040 cpus_or(covered
, covered
, nodemask
);
6043 for (j
= 0; j
< MAX_NUMNODES
; j
++) {
6044 cpumask_t tmp
, notcovered
;
6045 int n
= (i
+ j
) % MAX_NUMNODES
;
6047 cpus_complement(notcovered
, covered
);
6048 cpus_and(tmp
, notcovered
, *cpu_map
);
6049 cpus_and(tmp
, tmp
, domainspan
);
6050 if (cpus_empty(tmp
))
6053 nodemask
= node_to_cpumask(n
);
6054 cpus_and(tmp
, tmp
, nodemask
);
6055 if (cpus_empty(tmp
))
6058 sg
= kmalloc(sizeof(struct sched_group
), GFP_KERNEL
);
6061 "Can not alloc domain group for node %d\n", j
);
6066 sg
->next
= prev
->next
;
6067 cpus_or(covered
, covered
, tmp
);
6074 /* Calculate CPU power for physical packages and nodes */
6075 for_each_cpu_mask(i
, *cpu_map
) {
6077 struct sched_domain
*sd
;
6078 #ifdef CONFIG_SCHED_SMT
6079 sd
= &per_cpu(cpu_domains
, i
);
6080 power
= SCHED_LOAD_SCALE
;
6081 sd
->groups
->cpu_power
= power
;
6083 #ifdef CONFIG_SCHED_MC
6084 sd
= &per_cpu(core_domains
, i
);
6085 power
= SCHED_LOAD_SCALE
+ (cpus_weight(sd
->groups
->cpumask
)-1)
6086 * SCHED_LOAD_SCALE
/ 10;
6087 sd
->groups
->cpu_power
= power
;
6089 sd
= &per_cpu(phys_domains
, i
);
6092 * This has to be < 2 * SCHED_LOAD_SCALE
6093 * Lets keep it SCHED_LOAD_SCALE, so that
6094 * while calculating NUMA group's cpu_power
6096 * numa_group->cpu_power += phys_group->cpu_power;
6098 * See "only add power once for each physical pkg"
6101 sd
->groups
->cpu_power
= SCHED_LOAD_SCALE
;
6103 sd
= &per_cpu(phys_domains
, i
);
6104 power
= SCHED_LOAD_SCALE
+ SCHED_LOAD_SCALE
*
6105 (cpus_weight(sd
->groups
->cpumask
)-1) / 10;
6106 sd
->groups
->cpu_power
= power
;
6111 for (i
= 0; i
< MAX_NUMNODES
; i
++)
6112 init_numa_sched_groups_power(sched_group_nodes
[i
]);
6114 init_numa_sched_groups_power(sched_group_allnodes
);
6117 /* Attach the domains */
6118 for_each_cpu_mask(i
, *cpu_map
) {
6119 struct sched_domain
*sd
;
6120 #ifdef CONFIG_SCHED_SMT
6121 sd
= &per_cpu(cpu_domains
, i
);
6122 #elif defined(CONFIG_SCHED_MC)
6123 sd
= &per_cpu(core_domains
, i
);
6125 sd
= &per_cpu(phys_domains
, i
);
6127 cpu_attach_domain(sd
, i
);
6130 * Tune cache-hot values:
6132 calibrate_migration_costs(cpu_map
);
6138 free_sched_groups(cpu_map
);
6143 * Set up scheduler domains and groups. Callers must hold the hotplug lock.
6145 static int arch_init_sched_domains(const cpumask_t
*cpu_map
)
6147 cpumask_t cpu_default_map
;
6151 * Setup mask for cpus without special case scheduling requirements.
6152 * For now this just excludes isolated cpus, but could be used to
6153 * exclude other special cases in the future.
6155 cpus_andnot(cpu_default_map
, *cpu_map
, cpu_isolated_map
);
6157 err
= build_sched_domains(&cpu_default_map
);
6162 static void arch_destroy_sched_domains(const cpumask_t
*cpu_map
)
6164 free_sched_groups(cpu_map
);
6168 * Detach sched domains from a group of cpus specified in cpu_map
6169 * These cpus will now be attached to the NULL domain
6171 static void detach_destroy_domains(const cpumask_t
*cpu_map
)
6175 for_each_cpu_mask(i
, *cpu_map
)
6176 cpu_attach_domain(NULL
, i
);
6177 synchronize_sched();
6178 arch_destroy_sched_domains(cpu_map
);
6182 * Partition sched domains as specified by the cpumasks below.
6183 * This attaches all cpus from the cpumasks to the NULL domain,
6184 * waits for a RCU quiescent period, recalculates sched
6185 * domain information and then attaches them back to the
6186 * correct sched domains
6187 * Call with hotplug lock held
6189 int partition_sched_domains(cpumask_t
*partition1
, cpumask_t
*partition2
)
6191 cpumask_t change_map
;
6194 cpus_and(*partition1
, *partition1
, cpu_online_map
);
6195 cpus_and(*partition2
, *partition2
, cpu_online_map
);
6196 cpus_or(change_map
, *partition1
, *partition2
);
6198 /* Detach sched domains from all of the affected cpus */
6199 detach_destroy_domains(&change_map
);
6200 if (!cpus_empty(*partition1
))
6201 err
= build_sched_domains(partition1
);
6202 if (!err
&& !cpus_empty(*partition2
))
6203 err
= build_sched_domains(partition2
);
6208 #ifdef CONFIG_HOTPLUG_CPU
6210 * Force a reinitialization of the sched domains hierarchy. The domains
6211 * and groups cannot be updated in place without racing with the balancing
6212 * code, so we temporarily attach all running cpus to the NULL domain
6213 * which will prevent rebalancing while the sched domains are recalculated.
6215 static int update_sched_domains(struct notifier_block
*nfb
,
6216 unsigned long action
, void *hcpu
)
6219 case CPU_UP_PREPARE
:
6220 case CPU_DOWN_PREPARE
:
6221 detach_destroy_domains(&cpu_online_map
);
6224 case CPU_UP_CANCELED
:
6225 case CPU_DOWN_FAILED
:
6229 * Fall through and re-initialise the domains.
6236 /* The hotplug lock is already held by cpu_up/cpu_down */
6237 arch_init_sched_domains(&cpu_online_map
);
6243 void __init
sched_init_smp(void)
6246 arch_init_sched_domains(&cpu_online_map
);
6247 unlock_cpu_hotplug();
6248 /* XXX: Theoretical race here - CPU may be hotplugged now */
6249 hotcpu_notifier(update_sched_domains
, 0);
6252 void __init
sched_init_smp(void)
6255 #endif /* CONFIG_SMP */
6257 int in_sched_functions(unsigned long addr
)
6259 /* Linker adds these: start and end of __sched functions */
6260 extern char __sched_text_start
[], __sched_text_end
[];
6261 return in_lock_functions(addr
) ||
6262 (addr
>= (unsigned long)__sched_text_start
6263 && addr
< (unsigned long)__sched_text_end
);
6266 void __init
sched_init(void)
6271 for_each_possible_cpu(i
) {
6272 prio_array_t
*array
;
6275 spin_lock_init(&rq
->lock
);
6277 rq
->active
= rq
->arrays
;
6278 rq
->expired
= rq
->arrays
+ 1;
6279 rq
->best_expired_prio
= MAX_PRIO
;
6283 for (j
= 1; j
< 3; j
++)
6284 rq
->cpu_load
[j
] = 0;
6285 rq
->active_balance
= 0;
6287 rq
->migration_thread
= NULL
;
6288 INIT_LIST_HEAD(&rq
->migration_queue
);
6290 atomic_set(&rq
->nr_iowait
, 0);
6292 for (j
= 0; j
< 2; j
++) {
6293 array
= rq
->arrays
+ j
;
6294 for (k
= 0; k
< MAX_PRIO
; k
++) {
6295 INIT_LIST_HEAD(array
->queue
+ k
);
6296 __clear_bit(k
, array
->bitmap
);
6298 // delimiter for bitsearch
6299 __set_bit(MAX_PRIO
, array
->bitmap
);
6303 set_load_weight(&init_task
);
6305 * The boot idle thread does lazy MMU switching as well:
6307 atomic_inc(&init_mm
.mm_count
);
6308 enter_lazy_tlb(&init_mm
, current
);
6311 * Make us the idle thread. Technically, schedule() should not be
6312 * called from this thread, however somewhere below it might be,
6313 * but because we are the idle thread, we just pick up running again
6314 * when this runqueue becomes "idle".
6316 init_idle(current
, smp_processor_id());
6319 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
6320 void __might_sleep(char *file
, int line
)
6322 #if defined(in_atomic)
6323 static unsigned long prev_jiffy
; /* ratelimiting */
6325 if ((in_atomic() || irqs_disabled()) &&
6326 system_state
== SYSTEM_RUNNING
&& !oops_in_progress
) {
6327 if (time_before(jiffies
, prev_jiffy
+ HZ
) && prev_jiffy
)
6329 prev_jiffy
= jiffies
;
6330 printk(KERN_ERR
"BUG: sleeping function called from invalid"
6331 " context at %s:%d\n", file
, line
);
6332 printk("in_atomic():%d, irqs_disabled():%d\n",
6333 in_atomic(), irqs_disabled());
6338 EXPORT_SYMBOL(__might_sleep
);
6341 #ifdef CONFIG_MAGIC_SYSRQ
6342 void normalize_rt_tasks(void)
6344 struct task_struct
*p
;
6345 prio_array_t
*array
;
6346 unsigned long flags
;
6349 read_lock_irq(&tasklist_lock
);
6350 for_each_process(p
) {
6354 rq
= task_rq_lock(p
, &flags
);
6358 deactivate_task(p
, task_rq(p
));
6359 __setscheduler(p
, SCHED_NORMAL
, 0);
6361 __activate_task(p
, task_rq(p
));
6362 resched_task(rq
->curr
);
6365 task_rq_unlock(rq
, &flags
);
6367 read_unlock_irq(&tasklist_lock
);
6370 #endif /* CONFIG_MAGIC_SYSRQ */
6374 * These functions are only useful for the IA64 MCA handling.
6376 * They can only be called when the whole system has been
6377 * stopped - every CPU needs to be quiescent, and no scheduling
6378 * activity can take place. Using them for anything else would
6379 * be a serious bug, and as a result, they aren't even visible
6380 * under any other configuration.
6384 * curr_task - return the current task for a given cpu.
6385 * @cpu: the processor in question.
6387 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6389 task_t
*curr_task(int cpu
)
6391 return cpu_curr(cpu
);
6395 * set_curr_task - set the current task for a given cpu.
6396 * @cpu: the processor in question.
6397 * @p: the task pointer to set.
6399 * Description: This function must only be used when non-maskable interrupts
6400 * are serviced on a separate stack. It allows the architecture to switch the
6401 * notion of the current task on a cpu in a non-blocking manner. This function
6402 * must be called with all CPU's synchronized, and interrupts disabled, the
6403 * and caller must save the original value of the current task (see
6404 * curr_task() above) and restore that value before reenabling interrupts and
6405 * re-starting the system.
6407 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6409 void set_curr_task(int cpu
, task_t
*p
)