blob: dd153d6f8a04b7c2ba8c4954b8628ef70ad307ce [file] [log] [blame]
/*
* kernel/sched.c
*
* Kernel scheduler and related syscalls
*
* Copyright (C) 1991-2002 Linus Torvalds
*
* 1996-12-23 Modified by Dave Grothe to fix bugs in semaphores and
* make semaphores SMP safe
* 1998-11-19 Implemented schedule_timeout() and related stuff
* by Andrea Arcangeli
* 2002-01-04 New ultra-scalable O(1) scheduler by Ingo Molnar:
* hybrid priority-list and round-robin design with
* an array-switch method of distributing timeslices
* and per-CPU runqueues. Cleanups and useful suggestions
* by Davide Libenzi, preemptible kernel bits by Robert Love.
* 2003-09-03 Interactivity tuning by Con Kolivas.
* 2004-04-02 Scheduler domains code by Nick Piggin
*/
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/highmem.h>
#include <linux/smp_lock.h>
#include <asm/mmu_context.h>
#include <linux/interrupt.h>
#include <linux/capability.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
#include <linux/security.h>
#include <linux/notifier.h>
#include <linux/profile.h>
#include <linux/suspend.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/threads.h>
#include <linux/timer.h>
#include <linux/rcupdate.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/percpu.h>
#include <linux/kthread.h>
#include <linux/seq_file.h>
#include <linux/syscalls.h>
#include <linux/times.h>
#include <linux/acct.h>
#include <linux/kprobes.h>
#include <asm/tlb.h>
#include <asm/unistd.h>
/*
* Convert user-nice values [ -20 ... 0 ... 19 ]
* to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
* and back.
*/
#define NICE_TO_PRIO(nice) (MAX_RT_PRIO + (nice) + 20)
#define PRIO_TO_NICE(prio) ((prio) - MAX_RT_PRIO - 20)
#define TASK_NICE(p) PRIO_TO_NICE((p)->static_prio)
/*
* 'User priority' is the nice value converted to something we
* can work with better when scaling various scheduler parameters,
* it's a [ 0 ... 39 ] range.
*/
#define USER_PRIO(p) ((p)-MAX_RT_PRIO)
#define TASK_USER_PRIO(p) USER_PRIO((p)->static_prio)
#define MAX_USER_PRIO (USER_PRIO(MAX_PRIO))
/*
* Some helpers for converting nanosecond timing to jiffy resolution
*/
#define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ))
#define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ))
/*
* These are the 'tuning knobs' of the scheduler:
*
* Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger),
* default timeslice is 100 msecs, maximum timeslice is 800 msecs.
* Timeslices get refilled after they expire.
*/
#define MIN_TIMESLICE max(5 * HZ / 1000, 1)
#define DEF_TIMESLICE (100 * HZ / 1000)
#define ON_RUNQUEUE_WEIGHT 30
#define CHILD_PENALTY 95
#define PARENT_PENALTY 100
#define EXIT_WEIGHT 3
#define PRIO_BONUS_RATIO 25
#define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
#define INTERACTIVE_DELTA 2
#define MAX_SLEEP_AVG (DEF_TIMESLICE * MAX_BONUS)
#define STARVATION_LIMIT (MAX_SLEEP_AVG)
#define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG))
/*
* If a task is 'interactive' then we reinsert it in the active
* array after it has expired its current timeslice. (it will not
* continue to run immediately, it will still roundrobin with
* other interactive tasks.)
*
* This part scales the interactivity limit depending on niceness.
*
* We scale it linearly, offset by the INTERACTIVE_DELTA delta.
* Here are a few examples of different nice levels:
*
* TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
* TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
* TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0]
* TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
* TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
*
* (the X axis represents the possible -5 ... 0 ... +5 dynamic
* priority range a task can explore, a value of '1' means the
* task is rated interactive.)
*
* Ie. nice +19 tasks can never get 'interactive' enough to be
* reinserted into the active array. And only heavily CPU-hog nice -20
* tasks will be expired. Default nice 0 tasks are somewhere between,
* it takes some effort for them to get interactive, but it's not
* too hard.
*/
#define CURRENT_BONUS(p) \
(NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \
MAX_SLEEP_AVG)
#define GRANULARITY (10 * HZ / 1000 ? : 1)
#ifdef CONFIG_SMP
#define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
(1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
num_online_cpus())
#else
#define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
(1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)))
#endif
#define SCALE(v1,v1_max,v2_max) \
(v1) * (v2_max) / (v1_max)
#define DELTA(p) \
(SCALE(TASK_NICE(p) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \
INTERACTIVE_DELTA)
#define TASK_INTERACTIVE(p) \
((p)->prio <= (p)->static_prio - DELTA(p))
#define INTERACTIVE_SLEEP(p) \
(JIFFIES_TO_NS(MAX_SLEEP_AVG * \
(MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
#define TASK_PREEMPTS_CURR(p, rq) \
((p)->prio < (rq)->curr->prio)
/*
* task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
* to time slice values: [800ms ... 100ms ... 5ms]
*
* The higher a thread's priority, the bigger timeslices
* it gets during one round of execution. But even the lowest
* priority thread gets MIN_TIMESLICE worth of execution time.
*/
#define SCALE_PRIO(x, prio) \
max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO/2), MIN_TIMESLICE)
static unsigned int task_timeslice(task_t *p)
{
if (p->static_prio < NICE_TO_PRIO(0))
return SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio);
else
return SCALE_PRIO(DEF_TIMESLICE, p->static_prio);
}
#define task_hot(p, now, sd) ((long long) ((now) - (p)->last_ran) \
< (long long) (sd)->cache_hot_time)
/*
* These are the runqueue data structures:
*/
#define BITMAP_SIZE ((((MAX_PRIO+1+7)/8)+sizeof(long)-1)/sizeof(long))
typedef struct runqueue runqueue_t;
struct prio_array {
unsigned int nr_active;
unsigned long bitmap[BITMAP_SIZE];
struct list_head queue[MAX_PRIO];
};
/*
* This is the main, per-CPU runqueue data structure.
*
* Locking rule: those places that want to lock multiple runqueues
* (such as the load balancing or the thread migration code), lock
* acquire operations must be ordered by ascending &runqueue.
*/
struct runqueue {
spinlock_t lock;
/*
* nr_running and cpu_load should be in the same cacheline because
* remote CPUs use both these fields when doing load calculation.
*/
unsigned long nr_running;
#ifdef CONFIG_SMP
unsigned long cpu_load[3];
#endif
unsigned long long nr_switches;
/*
* This is part of a global counter where only the total sum
* over all CPUs matters. A task can increase this counter on
* one CPU and if it got migrated afterwards it may decrease
* it on another CPU. Always updated under the runqueue lock:
*/
unsigned long nr_uninterruptible;
unsigned long expired_timestamp;
unsigned long long timestamp_last_tick;
task_t *curr, *idle;
struct mm_struct *prev_mm;
prio_array_t *active, *expired, arrays[2];
int best_expired_prio;
atomic_t nr_iowait;
#ifdef CONFIG_SMP
struct sched_domain *sd;
/* For active balancing */
int active_balance;
int push_cpu;
task_t *migration_thread;
struct list_head migration_queue;
int cpu;
#endif
#ifdef CONFIG_SCHEDSTATS
/* latency stats */
struct sched_info rq_sched_info;
/* sys_sched_yield() stats */
unsigned long yld_exp_empty;
unsigned long yld_act_empty;
unsigned long yld_both_empty;
unsigned long yld_cnt;
/* schedule() stats */
unsigned long sched_switch;
unsigned long sched_cnt;
unsigned long sched_goidle;
/* try_to_wake_up() stats */
unsigned long ttwu_cnt;
unsigned long ttwu_local;
#endif
};
static DEFINE_PER_CPU(struct runqueue, runqueues);
/*
* The domain tree (rq->sd) is protected by RCU's quiescent state transition.
* See detach_destroy_domains: synchronize_sched for details.
*
* The domain tree of any CPU may only be accessed from within
* preempt-disabled sections.
*/
#define for_each_domain(cpu, domain) \
for (domain = rcu_dereference(cpu_rq(cpu)->sd); domain; domain = domain->parent)
#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
#define this_rq() (&__get_cpu_var(runqueues))
#define task_rq(p) cpu_rq(task_cpu(p))
#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
#ifndef prepare_arch_switch
# define prepare_arch_switch(next) do { } while (0)
#endif
#ifndef finish_arch_switch
# define finish_arch_switch(prev) do { } while (0)
#endif
#ifndef __ARCH_WANT_UNLOCKED_CTXSW
static inline int task_running(runqueue_t *rq, task_t *p)
{
return rq->curr == p;
}
static inline void prepare_lock_switch(runqueue_t *rq, task_t *next)
{
}
static inline void finish_lock_switch(runqueue_t *rq, task_t *prev)
{
#ifdef CONFIG_DEBUG_SPINLOCK
/* this is a valid case when another task releases the spinlock */
rq->lock.owner = current;
#endif
spin_unlock_irq(&rq->lock);
}
#else /* __ARCH_WANT_UNLOCKED_CTXSW */
static inline int task_running(runqueue_t *rq, task_t *p)
{
#ifdef CONFIG_SMP
return p->oncpu;
#else
return rq->curr == p;
#endif
}
static inline void prepare_lock_switch(runqueue_t *rq, task_t *next)
{
#ifdef CONFIG_SMP
/*
* We can optimise this out completely for !SMP, because the
* SMP rebalancing from interrupt is the only thing that cares
* here.
*/
next->oncpu = 1;
#endif
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
spin_unlock_irq(&rq->lock);
#else
spin_unlock(&rq->lock);
#endif
}
static inline void finish_lock_switch(runqueue_t *rq, task_t *prev)
{
#ifdef CONFIG_SMP
/*
* After ->oncpu is cleared, the task can be moved to a different CPU.
* We must ensure this doesn't happen until the switch is completely
* finished.
*/
smp_wmb();
prev->oncpu = 0;
#endif
#ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
local_irq_enable();
#endif
}
#endif /* __ARCH_WANT_UNLOCKED_CTXSW */
/*
* task_rq_lock - lock the runqueue a given task resides on and disable
* interrupts. Note the ordering: we can safely lookup the task_rq without
* explicitly disabling preemption.
*/
static inline runqueue_t *task_rq_lock(task_t *p, unsigned long *flags)
__acquires(rq->lock)
{
struct runqueue *rq;
repeat_lock_task:
local_irq_save(*flags);
rq = task_rq(p);
spin_lock(&rq->lock);
if (unlikely(rq != task_rq(p))) {
spin_unlock_irqrestore(&rq->lock, *flags);
goto repeat_lock_task;
}
return rq;
}
static inline void task_rq_unlock(runqueue_t *rq, unsigned long *flags)
__releases(rq->lock)
{
spin_unlock_irqrestore(&rq->lock, *flags);
}
#ifdef CONFIG_SCHEDSTATS
/*
* bump this up when changing the output format or the meaning of an existing
* format, so that tools can adapt (or abort)
*/
#define SCHEDSTAT_VERSION 12
static int show_schedstat(struct seq_file *seq, void *v)
{
int cpu;
seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
seq_printf(seq, "timestamp %lu\n", jiffies);
for_each_online_cpu(cpu) {
runqueue_t *rq = cpu_rq(cpu);
#ifdef CONFIG_SMP
struct sched_domain *sd;
int dcnt = 0;
#endif
/* runqueue-specific stats */
seq_printf(seq,
"cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
cpu, rq->yld_both_empty,
rq->yld_act_empty, rq->yld_exp_empty, rq->yld_cnt,
rq->sched_switch, rq->sched_cnt, rq->sched_goidle,
rq->ttwu_cnt, rq->ttwu_local,
rq->rq_sched_info.cpu_time,
rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt);
seq_printf(seq, "\n");
#ifdef CONFIG_SMP
/* domain-specific stats */
preempt_disable();
for_each_domain(cpu, sd) {
enum idle_type itype;
char mask_str[NR_CPUS];
cpumask_scnprintf(mask_str, NR_CPUS, sd->span);
seq_printf(seq, "domain%d %s", dcnt++, mask_str);
for (itype = SCHED_IDLE; itype < MAX_IDLE_TYPES;
itype++) {
seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu",
sd->lb_cnt[itype],
sd->lb_balanced[itype],
sd->lb_failed[itype],
sd->lb_imbalance[itype],
sd->lb_gained[itype],
sd->lb_hot_gained[itype],
sd->lb_nobusyq[itype],
sd->lb_nobusyg[itype]);
}
seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n",
sd->alb_cnt, sd->alb_failed, sd->alb_pushed,
sd->sbe_cnt, sd->sbe_balanced, sd->sbe_pushed,
sd->sbf_cnt, sd->sbf_balanced, sd->sbf_pushed,
sd->ttwu_wake_remote, sd->ttwu_move_affine, sd->ttwu_move_balance);
}
preempt_enable();
#endif
}
return 0;
}
static int schedstat_open(struct inode *inode, struct file *file)
{
unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32);
char *buf = kmalloc(size, GFP_KERNEL);
struct seq_file *m;
int res;
if (!buf)
return -ENOMEM;
res = single_open(file, show_schedstat, NULL);
if (!res) {
m = file->private_data;
m->buf = buf;
m->size = size;
} else
kfree(buf);
return res;
}
struct file_operations proc_schedstat_operations = {
.open = schedstat_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
# define schedstat_inc(rq, field) do { (rq)->field++; } while (0)
# define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0)
#else /* !CONFIG_SCHEDSTATS */
# define schedstat_inc(rq, field) do { } while (0)
# define schedstat_add(rq, field, amt) do { } while (0)
#endif
/*
* rq_lock - lock a given runqueue and disable interrupts.
*/
static inline runqueue_t *this_rq_lock(void)
__acquires(rq->lock)
{
runqueue_t *rq;
local_irq_disable();
rq = this_rq();
spin_lock(&rq->lock);
return rq;
}
#ifdef CONFIG_SCHEDSTATS
/*
* Called when a process is dequeued from the active array and given
* the cpu. We should note that with the exception of interactive
* tasks, the expired queue will become the active queue after the active
* queue is empty, without explicitly dequeuing and requeuing tasks in the
* expired queue. (Interactive tasks may be requeued directly to the
* active queue, thus delaying tasks in the expired queue from running;
* see scheduler_tick()).
*
* This function is only called from sched_info_arrive(), rather than
* dequeue_task(). Even though a task may be queued and dequeued multiple
* times as it is shuffled about, we're really interested in knowing how
* long it was from the *first* time it was queued to the time that it
* finally hit a cpu.
*/
static inline void sched_info_dequeued(task_t *t)
{
t->sched_info.last_queued = 0;
}
/*
* Called when a task finally hits the cpu. We can now calculate how
* long it was waiting to run. We also note when it began so that we
* can keep stats on how long its timeslice is.
*/
static void sched_info_arrive(task_t *t)
{
unsigned long now = jiffies, diff = 0;
struct runqueue *rq = task_rq(t);
if (t->sched_info.last_queued)
diff = now - t->sched_info.last_queued;
sched_info_dequeued(t);
t->sched_info.run_delay += diff;
t->sched_info.last_arrival = now;
t->sched_info.pcnt++;
if (!rq)
return;
rq->rq_sched_info.run_delay += diff;
rq->rq_sched_info.pcnt++;
}
/*
* Called when a process is queued into either the active or expired
* array. The time is noted and later used to determine how long we
* had to wait for us to reach the cpu. Since the expired queue will
* become the active queue after active queue is empty, without dequeuing
* and requeuing any tasks, we are interested in queuing to either. It
* is unusual but not impossible for tasks to be dequeued and immediately
* requeued in the same or another array: this can happen in sched_yield(),
* set_user_nice(), and even load_balance() as it moves tasks from runqueue
* to runqueue.
*
* This function is only called from enqueue_task(), but also only updates
* the timestamp if it is already not set. It's assumed that
* sched_info_dequeued() will clear that stamp when appropriate.
*/
static inline void sched_info_queued(task_t *t)
{
if (!t->sched_info.last_queued)
t->sched_info.last_queued = jiffies;
}
/*
* Called when a process ceases being the active-running process, either
* voluntarily or involuntarily. Now we can calculate how long we ran.
*/
static inline void sched_info_depart(task_t *t)
{
struct runqueue *rq = task_rq(t);
unsigned long diff = jiffies - t->sched_info.last_arrival;
t->sched_info.cpu_time += diff;
if (rq)
rq->rq_sched_info.cpu_time += diff;
}
/*
* Called when tasks are switched involuntarily due, typically, to expiring
* their time slice. (This may also be called when switching to or from
* the idle task.) We are only called when prev != next.
*/
static inline void sched_info_switch(task_t *prev, task_t *next)
{
struct runqueue *rq = task_rq(prev);
/*
* prev now departs the cpu. It's not interesting to record
* stats about how efficient we were at scheduling the idle
* process, however.
*/
if (prev != rq->idle)
sched_info_depart(prev);
if (next != rq->idle)
sched_info_arrive(next);
}
#else
#define sched_info_queued(t) do { } while (0)
#define sched_info_switch(t, next) do { } while (0)
#endif /* CONFIG_SCHEDSTATS */
/*
* Adding/removing a task to/from a priority array:
*/
static void dequeue_task(struct task_struct *p, prio_array_t *array)
{
array->nr_active--;
list_del(&p->run_list);
if (list_empty(array->queue + p->prio))
__clear_bit(p->prio, array->bitmap);
}
static void enqueue_task(struct task_struct *p, prio_array_t *array)
{
sched_info_queued(p);
list_add_tail(&p->run_list, array->queue + p->prio);
__set_bit(p->prio, array->bitmap);
array->nr_active++;
p->array = array;
}
/*
* Put task to the end of the run list without the overhead of dequeue
* followed by enqueue.
*/
static void requeue_task(struct task_struct *p, prio_array_t *array)
{
list_move_tail(&p->run_list, array->queue + p->prio);
}
static inline void enqueue_task_head(struct task_struct *p, prio_array_t *array)
{
list_add(&p->run_list, array->queue + p->prio);
__set_bit(p->prio, array->bitmap);
array->nr_active++;
p->array = array;
}
/*
* effective_prio - return the priority that is based on the static
* priority but is modified by bonuses/penalties.
*
* We scale the actual sleep average [0 .... MAX_SLEEP_AVG]
* into the -5 ... 0 ... +5 bonus/penalty range.
*
* We use 25% of the full 0...39 priority range so that:
*
* 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs.
* 2) nice -20 CPU hogs do not get preempted by nice 0 tasks.
*
* Both properties are important to certain workloads.
*/
static int effective_prio(task_t *p)
{
int bonus, prio;
if (rt_task(p))
return p->prio;
bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;
prio = p->static_prio - bonus;
if (prio < MAX_RT_PRIO)
prio = MAX_RT_PRIO;
if (prio > MAX_PRIO-1)
prio = MAX_PRIO-1;
return prio;
}
/*
* __activate_task - move a task to the runqueue.
*/
static void __activate_task(task_t *p, runqueue_t *rq)
{
prio_array_t *target = rq->active;
if (batch_task(p))
target = rq->expired;
enqueue_task(p, target);
rq->nr_running++;
}
/*
* __activate_idle_task - move idle task to the _front_ of runqueue.
*/
static inline void __activate_idle_task(task_t *p, runqueue_t *rq)
{
enqueue_task_head(p, rq->active);
rq->nr_running++;
}
static int recalc_task_prio(task_t *p, unsigned long long now)
{
/* Caller must always ensure 'now >= p->timestamp' */
unsigned long long __sleep_time = now - p->timestamp;
unsigned long sleep_time;
if (batch_task(p))
sleep_time = 0;
else {
if (__sleep_time > NS_MAX_SLEEP_AVG)
sleep_time = NS_MAX_SLEEP_AVG;
else
sleep_time = (unsigned long)__sleep_time;
}
if (likely(sleep_time > 0)) {
/*
* User tasks that sleep a long time are categorised as
* idle. They will only have their sleep_avg increased to a
* level that makes them just interactive priority to stay
* active yet prevent them suddenly becoming cpu hogs and
* starving other processes.
*/
if (p->mm && sleep_time > INTERACTIVE_SLEEP(p)) {
unsigned long ceiling;
ceiling = JIFFIES_TO_NS(MAX_SLEEP_AVG -
DEF_TIMESLICE);
if (p->sleep_avg < ceiling)
p->sleep_avg = ceiling;
} else {
/*
* Tasks waking from uninterruptible sleep are
* limited in their sleep_avg rise as they
* are likely to be waiting on I/O
*/
if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) {
if (p->sleep_avg >= INTERACTIVE_SLEEP(p))
sleep_time = 0;
else if (p->sleep_avg + sleep_time >=
INTERACTIVE_SLEEP(p)) {
p->sleep_avg = INTERACTIVE_SLEEP(p);
sleep_time = 0;
}
}
/*
* This code gives a bonus to interactive tasks.
*
* The boost works by updating the 'average sleep time'
* value here, based on ->timestamp. The more time a
* task spends sleeping, the higher the average gets -
* and the higher the priority boost gets as well.
*/
p->sleep_avg += sleep_time;
if (p->sleep_avg > NS_MAX_SLEEP_AVG)
p->sleep_avg = NS_MAX_SLEEP_AVG;
}
}
return effective_prio(p);
}
/*
* activate_task - move a task to the runqueue and do priority recalculation
*
* Update all the scheduling statistics stuff. (sleep average
* calculation, priority modifiers, etc.)
*/
static void activate_task(task_t *p, runqueue_t *rq, int local)
{
unsigned long long now;
now = sched_clock();
#ifdef CONFIG_SMP
if (!local) {
/* Compensate for drifting sched_clock */
runqueue_t *this_rq = this_rq();
now = (now - this_rq->timestamp_last_tick)
+ rq->timestamp_last_tick;
}
#endif
if (!rt_task(p))
p->prio = recalc_task_prio(p, now);
/*
* This checks to make sure it's not an uninterruptible task
* that is now waking up.
*/
if (p->sleep_type == SLEEP_NORMAL) {
/*
* Tasks which were woken up by interrupts (ie. hw events)
* are most likely of interactive nature. So we give them
* the credit of extending their sleep time to the period
* of time they spend on the runqueue, waiting for execution
* on a CPU, first time around:
*/
if (in_interrupt())
p->sleep_type = SLEEP_INTERRUPTED;
else {
/*
* Normal first-time wakeups get a credit too for
* on-runqueue time, but it will be weighted down:
*/
p->sleep_type = SLEEP_INTERACTIVE;
}
}
p->timestamp = now;
__activate_task(p, rq);
}
/*
* deactivate_task - remove a task from the runqueue.
*/
static void deactivate_task(struct task_struct *p, runqueue_t *rq)
{
rq->nr_running--;
dequeue_task(p, p->array);
p->array = NULL;
}
/*
* resched_task - mark a task 'to be rescheduled now'.
*
* On UP this means the setting of the need_resched flag, on SMP it
* might also involve a cross-CPU call to trigger the scheduler on
* the target CPU.
*/
#ifdef CONFIG_SMP
static void resched_task(task_t *p)
{
int cpu;
assert_spin_locked(&task_rq(p)->lock);
if (unlikely(test_tsk_thread_flag(p, TIF_NEED_RESCHED)))
return;
set_tsk_thread_flag(p, TIF_NEED_RESCHED);
cpu = task_cpu(p);
if (cpu == smp_processor_id())
return;
/* NEED_RESCHED must be visible before we test POLLING_NRFLAG */
smp_mb();
if (!test_tsk_thread_flag(p, TIF_POLLING_NRFLAG))
smp_send_reschedule(cpu);
}
#else
static inline void resched_task(task_t *p)
{
assert_spin_locked(&task_rq(p)->lock);
set_tsk_need_resched(p);
}
#endif
/**
* task_curr - is this task currently executing on a CPU?
* @p: the task in question.
*/
inline int task_curr(const task_t *p)
{
return cpu_curr(task_cpu(p)) == p;
}
#ifdef CONFIG_SMP
typedef struct {
struct list_head list;
task_t *task;
int dest_cpu;
struct completion done;
} migration_req_t;
/*
* The task's runqueue lock must be held.
* Returns true if you have to wait for migration thread.
*/
static int migrate_task(task_t *p, int dest_cpu, migration_req_t *req)
{
runqueue_t *rq = task_rq(p);
/*
* If the task is not on a runqueue (and not running), then
* it is sufficient to simply update the task's cpu field.
*/
if (!p->array && !task_running(rq, p)) {
set_task_cpu(p, dest_cpu);
return 0;
}
init_completion(&req->done);
req->task = p;
req->dest_cpu = dest_cpu;
list_add(&req->list, &rq->migration_queue);
return 1;
}
/*
* wait_task_inactive - wait for a thread to unschedule.
*
* The caller must ensure that the task *will* unschedule sometime soon,
* else this function might spin for a *long* time. This function can't
* be called with interrupts off, or it may introduce deadlock with
* smp_call_function() if an IPI is sent by the same process we are
* waiting to become inactive.
*/
void wait_task_inactive(task_t *p)
{
unsigned long flags;
runqueue_t *rq;
int preempted;
repeat:
rq = task_rq_lock(p, &flags);
/* Must be off runqueue entirely, not preempted. */
if (unlikely(p->array || task_running(rq, p))) {
/* If it's preempted, we yield. It could be a while. */
preempted = !task_running(rq, p);
task_rq_unlock(rq, &flags);
cpu_relax();
if (preempted)
yield();
goto repeat;
}
task_rq_unlock(rq, &flags);
}
/***
* kick_process - kick a running thread to enter/exit the kernel
* @p: the to-be-kicked thread
*
* Cause a process which is running on another CPU to enter
* kernel-mode, without any delay. (to get signals handled.)
*
* NOTE: this function doesnt have to take the runqueue lock,
* because all it wants to ensure is that the remote task enters
* the kernel. If the IPI races and the task has been migrated
* to another CPU then no harm is done and the purpose has been
* achieved as well.
*/
void kick_process(task_t *p)
{
int cpu;
preempt_disable();
cpu = task_cpu(p);
if ((cpu != smp_processor_id()) && task_curr(p))
smp_send_reschedule(cpu);
preempt_enable();
}
/*
* Return a low guess at the load of a migration-source cpu.
*
* We want to under-estimate the load of migration sources, to
* balance conservatively.
*/
static inline unsigned long source_load(int cpu, int type)
{
runqueue_t *rq = cpu_rq(cpu);
unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;
if (type == 0)
return load_now;
return min(rq->cpu_load[type-1], load_now);
}
/*
* Return a high guess at the load of a migration-target cpu
*/
static inline unsigned long target_load(int cpu, int type)
{
runqueue_t *rq = cpu_rq(cpu);
unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;
if (type == 0)
return load_now;
return max(rq->cpu_load[type-1], load_now);
}
/*
* find_idlest_group finds and returns the least busy CPU group within the
* domain.
*/
static struct sched_group *
find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
{
struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups;
unsigned long min_load = ULONG_MAX, this_load = 0;
int load_idx = sd->forkexec_idx;
int imbalance = 100 + (sd->imbalance_pct-100)/2;
do {
unsigned long load, avg_load;
int local_group;
int i;
/* Skip over this group if it has no CPUs allowed */
if (!cpus_intersects(group->cpumask, p->cpus_allowed))
goto nextgroup;
local_group = cpu_isset(this_cpu, group->cpumask);
/* Tally up the load of all CPUs in the group */
avg_load = 0;
for_each_cpu_mask(i, group->cpumask) {
/* Bias balancing toward cpus of our domain */
if (local_group)
load = source_load(i, load_idx);
else
load = target_load(i, load_idx);
avg_load += load;
}
/* Adjust by relative CPU power of the group */
avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
if (local_group) {
this_load = avg_load;
this = group;
} else if (avg_load < min_load) {
min_load = avg_load;
idlest = group;
}
nextgroup:
group = group->next;
} while (group != sd->groups);
if (!idlest || 100*this_load < imbalance*min_load)
return NULL;
return idlest;
}
/*
* find_idlest_queue - find the idlest runqueue among the cpus in group.
*/
static int
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
cpumask_t tmp;
unsigned long load, min_load = ULONG_MAX;
int idlest = -1;
int i;
/* Traverse only the allowed CPUs */
cpus_and(tmp, group->cpumask, p->cpus_allowed);
for_each_cpu_mask(i, tmp) {
load = source_load(i, 0);
if (load < min_load || (load == min_load && i == this_cpu)) {
min_load = load;
idlest = i;
}
}
return idlest;
}
/*
* sched_balance_self: balance the current task (running on cpu) in domains
* that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
* SD_BALANCE_EXEC.
*
* Balance, ie. select the least loaded group.
*
* Returns the target CPU number, or the same CPU if no balancing is needed.
*
* preempt must be disabled.
*/
static int sched_balance_self(int cpu, int flag)
{
struct task_struct *t = current;
struct sched_domain *tmp, *sd = NULL;
for_each_domain(cpu, tmp)
if (tmp->flags & flag)
sd = tmp;
while (sd) {
cpumask_t span;
struct sched_group *group;
int new_cpu;
int weight;
span = sd->span;
group = find_idlest_group(sd, t, cpu);
if (!group)
goto nextlevel;
new_cpu = find_idlest_cpu(group, t, cpu);
if (new_cpu == -1 || new_cpu == cpu)
goto nextlevel;
/* Now try balancing at a lower domain level */
cpu = new_cpu;
nextlevel:
sd = NULL;
weight = cpus_weight(span);
for_each_domain(cpu, tmp) {
if (weight <= cpus_weight(tmp->span))
break;
if (tmp->flags & flag)
sd = tmp;
}
/* while loop will break here if sd == NULL */
}
return cpu;
}
#endif /* CONFIG_SMP */
/*
* wake_idle() will wake a task on an idle cpu if task->cpu is
* not idle and an idle cpu is available. The span of cpus to
* search starts with cpus closest then further out as needed,
* so we always favor a closer, idle cpu.
*
* Returns the CPU we should wake onto.
*/
#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
static int wake_idle(int cpu, task_t *p)
{
cpumask_t tmp;
struct sched_domain *sd;
int i;
if (idle_cpu(cpu))
return cpu;
for_each_domain(cpu, sd) {
if (sd->flags & SD_WAKE_IDLE) {
cpus_and(tmp, sd->span, p->cpus_allowed);
for_each_cpu_mask(i, tmp) {
if (idle_cpu(i))
return i;
}
}
else
break;
}
return cpu;
}
#else
static inline int wake_idle(int cpu, task_t *p)
{
return cpu;
}
#endif
/***
* try_to_wake_up - wake up a thread
* @p: the to-be-woken-up thread
* @state: the mask of task states that can be woken
* @sync: do a synchronous wakeup?
*
* Put it on the run-queue if it's not already there. The "current"
* thread is always on the run-queue (except when the actual
* re-schedule is in progress), and as such you're allowed to do
* the simpler "current->state = TASK_RUNNING" to mark yourself
* runnable without the overhead of this.
*
* returns failure only if the task is already active.
*/
static int try_to_wake_up(task_t *p, unsigned int state, int sync)
{
int cpu, this_cpu, success = 0;
unsigned long flags;
long old_state;
runqueue_t *rq;
#ifdef CONFIG_SMP
unsigned long load, this_load;
struct sched_domain *sd, *this_sd = NULL;
int new_cpu;
#endif
rq = task_rq_lock(p, &flags);
old_state = p->state;
if (!(old_state & state))
goto out;
if (p->array)
goto out_running;
cpu = task_cpu(p);
this_cpu = smp_processor_id();
#ifdef CONFIG_SMP
if (unlikely(task_running(rq, p)))
goto out_activate;
new_cpu = cpu;
schedstat_inc(rq, ttwu_cnt);
if (cpu == this_cpu) {
schedstat_inc(rq, ttwu_local);
goto out_set_cpu;
}
for_each_domain(this_cpu, sd) {
if (cpu_isset(cpu, sd->span)) {
schedstat_inc(sd, ttwu_wake_remote);
this_sd = sd;
break;
}
}
if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
goto out_set_cpu;
/*
* Check for affine wakeup and passive balancing possibilities.
*/
if (this_sd) {
int idx = this_sd->wake_idx;
unsigned int imbalance;
imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
load = source_load(cpu, idx);
this_load = target_load(this_cpu, idx);
new_cpu = this_cpu; /* Wake to this CPU if we can */
if (this_sd->flags & SD_WAKE_AFFINE) {
unsigned long tl = this_load;
/*
* If sync wakeup then subtract the (maximum possible)
* effect of the currently running task from the load
* of the current CPU:
*/
if (sync)
tl -= SCHED_LOAD_SCALE;
if ((tl <= load &&
tl + target_load(cpu, idx) <= SCHED_LOAD_SCALE) ||
100*(tl + SCHED_LOAD_SCALE) <= imbalance*load) {
/*
* This domain has SD_WAKE_AFFINE and
* p is cache cold in this domain, and
* there is no bad imbalance.
*/
schedstat_inc(this_sd, ttwu_move_affine);
goto out_set_cpu;
}
}
/*
* Start passive balancing when half the imbalance_pct
* limit is reached.
*/
if (this_sd->flags & SD_WAKE_BALANCE) {
if (imbalance*this_load <= 100*load) {
schedstat_inc(this_sd, ttwu_move_balance);
goto out_set_cpu;
}
}
}
new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */
out_set_cpu:
new_cpu = wake_idle(new_cpu, p);
if (new_cpu != cpu) {
set_task_cpu(p, new_cpu);
task_rq_unlock(rq, &flags);
/* might preempt at this point */
rq = task_rq_lock(p, &flags);
old_state = p->state;
if (!(old_state & state))
goto out;
if (p->array)
goto out_running;
this_cpu = smp_processor_id();
cpu = task_cpu(p);
}
out_activate:
#endif /* CONFIG_SMP */
if (old_state == TASK_UNINTERRUPTIBLE) {
rq->nr_uninterruptible--;
/*
* Tasks on involuntary sleep don't earn
* sleep_avg beyond just interactive state.
*/
p->sleep_type = SLEEP_NONINTERACTIVE;
} else
/*
* Tasks that have marked their sleep as noninteractive get
* woken up with their sleep average not weighted in an
* interactive way.
*/
if (old_state & TASK_NONINTERACTIVE)
p->sleep_type = SLEEP_NONINTERACTIVE;
activate_task(p, rq, cpu == this_cpu);
/*
* Sync wakeups (i.e. those types of wakeups where the waker
* has indicated that it will leave the CPU in short order)
* don't trigger a preemption, if the woken up task will run on
* this cpu. (in this case the 'I will reschedule' promise of
* the waker guarantees that the freshly woken up task is going
* to be considered on this CPU.)
*/
if (!sync || cpu != this_cpu) {
if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
}
success = 1;
out_running:
p->state = TASK_RUNNING;
out:
task_rq_unlock(rq, &flags);
return success;
}
int fastcall wake_up_process(task_t *p)
{
return try_to_wake_up(p, TASK_STOPPED | TASK_TRACED |
TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, 0);
}
EXPORT_SYMBOL(wake_up_process);
int fastcall wake_up_state(task_t *p, unsigned int state)
{
return try_to_wake_up(p, state, 0);
}
/*
* Perform scheduler related setup for a newly forked process p.
* p is forked by current.
*/
void fastcall sched_fork(task_t *p, int clone_flags)
{
int cpu = get_cpu();
#ifdef CONFIG_SMP
cpu = sched_balance_self(cpu, SD_BALANCE_FORK);
#endif
set_task_cpu(p, cpu);
/*
* We mark the process as running here, but have not actually
* inserted it onto the runqueue yet. This guarantees that
* nobody will actually run it, and a signal or other external
* event cannot wake it up and insert it on the runqueue either.
*/
p->state = TASK_RUNNING;
INIT_LIST_HEAD(&p->run_list);
p->array = NULL;
#ifdef CONFIG_SCHEDSTATS
memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
p->oncpu = 0;
#endif
#ifdef CONFIG_PREEMPT
/* Want to start with kernel preemption disabled. */
task_thread_info(p)->preempt_count = 1;
#endif
/*
* Share the timeslice between parent and child, thus the
* total amount of pending timeslices in the system doesn't change,
* resulting in more scheduling fairness.
*/
local_irq_disable();
p->time_slice = (current->time_slice + 1) >> 1;
/*
* The remainder of the first timeslice might be recovered by
* the parent if the child exits early enough.
*/
p->first_time_slice = 1;
current->time_slice >>= 1;
p->timestamp = sched_clock();
if (unlikely(!current->time_slice)) {
/*
* This case is rare, it happens when the parent has only
* a single jiffy left from its timeslice. Taking the
* runqueue lock is not a problem.
*/
current->time_slice = 1;
scheduler_tick();
}
local_irq_enable();
put_cpu();
}
/*
* wake_up_new_task - wake up a newly created task for the first time.
*
* This function will do some initial scheduler statistics housekeeping
* that must be done for every newly created context, then puts the task
* on the runqueue and wakes it.
*/
void fastcall wake_up_new_task(task_t *p, unsigned long clone_flags)
{
unsigned long flags;
int this_cpu, cpu;
runqueue_t *rq, *this_rq;
rq = task_rq_lock(p, &flags);
BUG_ON(p->state != TASK_RUNNING);
this_cpu = smp_processor_id();
cpu = task_cpu(p);
/*
* We decrease the sleep average of forking parents
* and children as well, to keep max-interactive tasks
* from forking tasks that are max-interactive. The parent
* (current) is done further down, under its lock.
*/
p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
p->prio = effective_prio(p);
if (likely(cpu == this_cpu)) {
if (!(clone_flags & CLONE_VM)) {
/*
* The VM isn't cloned, so we're in a good position to
* do child-runs-first in anticipation of an exec. This
* usually avoids a lot of COW overhead.
*/
if (unlikely(!current->array))
__activate_task(p, rq);
else {
p->prio = current->prio;
list_add_tail(&p->run_list, &current->run_list);
p->array = current->array;
p->array->nr_active++;
rq->nr_running++;
}
set_need_resched();
} else
/* Run child last */
__activate_task(p, rq);
/*
* We skip the following code due to cpu == this_cpu
*
* task_rq_unlock(rq, &flags);
* this_rq = task_rq_lock(current, &flags);
*/
this_rq = rq;
} else {
this_rq = cpu_rq(this_cpu);
/*
* Not the local CPU - must adjust timestamp. This should
* get optimised away in the !CONFIG_SMP case.
*/
p->timestamp = (p->timestamp - this_rq->timestamp_last_tick)
+ rq->timestamp_last_tick;
__activate_task(p, rq);
if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
/*
* Parent and child are on different CPUs, now get the
* parent runqueue to update the parent's ->sleep_avg:
*/
task_rq_unlock(rq, &flags);
this_rq = task_rq_lock(current, &flags);
}
current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
task_rq_unlock(this_rq, &flags);
}
/*
* Potentially available exiting-child timeslices are
* retrieved here - this way the parent does not get
* penalized for creating too many threads.
*
* (this cannot be used to 'generate' timeslices
* artificially, because any timeslice recovered here
* was given away by the parent in the first place.)
*/
void fastcall sched_exit(task_t *p)
{
unsigned long flags;
runqueue_t *rq;
/*
* If the child was a (relative-) CPU hog then decrease
* the sleep_avg of the parent as well.
*/
rq = task_rq_lock(p->parent, &flags);
if (p->first_time_slice && task_cpu(p) == task_cpu(p->parent)) {
p->parent->time_slice += p->time_slice;
if (unlikely(p->parent->time_slice > task_timeslice(p)))
p->parent->time_slice = task_timeslice(p);
}
if (p->sleep_avg < p->parent->sleep_avg)
p->parent->sleep_avg = p->parent->sleep_avg /
(EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
(EXIT_WEIGHT + 1);
task_rq_unlock(rq, &flags);
}
/**
* prepare_task_switch - prepare to switch tasks
* @rq: the runqueue preparing to switch
* @next: the task we are going to switch to.
*
* This is called with the rq lock held and interrupts off. It must
* be paired with a subsequent finish_task_switch after the context
* switch.
*
* prepare_task_switch sets up locking and calls architecture specific
* hooks.
*/
static inline void prepare_task_switch(runqueue_t *rq, task_t *next)
{
prepare_lock_switch(rq, next);
prepare_arch_switch(next);
}
/**
* finish_task_switch - clean up after a task-switch
* @rq: runqueue associated with task-switch
* @prev: the thread we just switched away from.
*
* finish_task_switch must be called after the context switch, paired
* with a prepare_task_switch call before the context switch.
* finish_task_switch will reconcile locking set up by prepare_task_switch,
* and do any other architecture-specific cleanup actions.
*
* Note that we may have delayed dropping an mm in context_switch(). If
* so, we finish that here outside of the runqueue lock. (Doing it
* with the lock held can cause deadlocks; see schedule() for
* details.)
*/
static inline void finish_task_switch(runqueue_t *rq, task_t *prev)
__releases(rq->lock)
{
struct mm_struct *mm = rq->prev_mm;
unsigned long prev_task_flags;
rq->prev_mm = NULL;
/*
* A task struct has one reference for the use as "current".
* If a task dies, then it sets EXIT_ZOMBIE in tsk->exit_state and
* calls schedule one last time. The schedule call will never return,
* and the scheduled task must drop that reference.
* The test for EXIT_ZOMBIE must occur while the runqueue locks are
* still held, otherwise prev could be scheduled on another cpu, die
* there before we look at prev->state, and then the reference would
* be dropped twice.
* Manfred Spraul <manfred@colorfullife.com>
*/
prev_task_flags = prev->flags;
finish_arch_switch(prev);
finish_lock_switch(rq, prev);
if (mm)
mmdrop(mm);
if (unlikely(prev_task_flags & PF_DEAD)) {
/*
* Remove function-return probe instances associated with this
* task and put them back on the free list.
*/
kprobe_flush_task(prev);
put_task_struct(prev);
}
}
/**
* schedule_tail - first thing a freshly forked thread must call.
* @prev: the thread we just switched away from.
*/
asmlinkage void schedule_tail(task_t *prev)
__releases(rq->lock)
{
runqueue_t *rq = this_rq();
finish_task_switch(rq, prev);
#ifdef __ARCH_WANT_UNLOCKED_CTXSW
/* In this case, finish_task_switch does not reenable preemption */
preempt_enable();
#endif
if (current->set_child_tid)
put_user(current->pid, current->set_child_tid);
}
/*
* context_switch - switch to the new MM and the new
* thread's register state.
*/
static inline
task_t * context_switch(runqueue_t *rq, task_t *prev, task_t *next)
{
struct mm_struct *mm = next->mm;
struct mm_struct *oldmm = prev->active_mm;
if (unlikely(!mm)) {
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);
enter_lazy_tlb(oldmm, next);
} else
switch_mm(oldmm, mm, next);
if (unlikely(!prev->mm)) {
prev->active_mm = NULL;
WARN_ON(rq->prev_mm);
rq->prev_mm = oldmm;
}
/* Here we just switch the register state and the stack. */
switch_to(prev, next, prev);
return prev;
}
/*
* nr_running, nr_uninterruptible and nr_context_switches:
*
* externally visible scheduler statistics: current number of runnable
* threads, current number of uninterruptible-sleeping threads, total
* number of context switches performed since bootup.
*/
unsigned long nr_running(void)
{
unsigned long i, sum = 0;
for_each_online_cpu(i)
sum += cpu_rq(i)->nr_running;
return sum;
}
unsigned long nr_uninterruptible(void)
{
unsigned long i, sum = 0;
for_each_possible_cpu(i)
sum += cpu_rq(i)->nr_uninterruptible;
/*
* Since we read the counters lockless, it might be slightly
* inaccurate. Do not allow it to go below zero though:
*/
if (unlikely((long)sum < 0))
sum = 0;
return sum;
}
unsigned long long nr_context_switches(void)
{
unsigned long long i, sum = 0;
for_each_possible_cpu(i)
sum += cpu_rq(i)->nr_switches;
return sum;
}
unsigned long nr_iowait(void)
{
unsigned long i, sum = 0;
for_each_possible_cpu(i)
sum += atomic_read(&cpu_rq(i)->nr_iowait);
return sum;
}
unsigned long nr_active(void)
{
unsigned long i, running = 0, uninterruptible = 0;
for_each_online_cpu(i) {
running += cpu_rq(i)->nr_running;
uninterruptible += cpu_rq(i)->nr_uninterruptible;
}
if (unlikely((long)uninterruptible < 0))
uninterruptible = 0;
return running + uninterruptible;
}
#ifdef CONFIG_SMP
/*
* double_rq_lock - safely lock two runqueues
*
* We must take them in cpu order to match code in
* dependent_sleeper and wake_dependent_sleeper.
*
* Note this does not disable interrupts like task_rq_lock,
* you need to do so manually before calling.
*/
static void double_rq_lock(runqueue_t *rq1, runqueue_t *rq2)
__acquires(rq1->lock)
__acquires(rq2->lock)
{
if (rq1 == rq2) {
spin_lock(&rq1->lock);
__acquire(rq2->lock); /* Fake it out ;) */
} else {
if (rq1->cpu < rq2->cpu) {
spin_lock(&rq1->lock);
spin_lock(&rq2->lock);
} else {
spin_lock(&rq2->lock);
spin_lock(&rq1->lock);
}
}
}
/*
* double_rq_unlock - safely unlock two runqueues
*
* Note this does not restore interrupts like task_rq_unlock,
* you need to do so manually after calling.
*/
static void double_rq_unlock(runqueue_t *rq1, runqueue_t *rq2)
__releases(rq1->lock)
__releases(rq2->lock)
{
spin_unlock(&rq1->lock);
if (rq1 != rq2)
spin_unlock(&rq2->lock);
else
__release(rq2->lock);
}
/*
* double_lock_balance - lock the busiest runqueue, this_rq is locked already.
*/
static void double_lock_balance(runqueue_t *this_rq, runqueue_t *busiest)
__releases(this_rq->lock)
__acquires(busiest->lock)
__acquires(this_rq->lock)
{
if (unlikely(!spin_trylock(&busiest->lock))) {
if (busiest->cpu < this_rq->cpu) {
spin_unlock(&this_rq->lock);
spin_lock(&busiest->lock);
spin_lock(&this_rq->lock);
} else
spin_lock(&busiest->lock);
}
}
/*
* If dest_cpu is allowed for this process, migrate the task to it.
* This is accomplished by forcing the cpu_allowed mask to only
* allow dest_cpu, which will force the cpu onto dest_cpu. Then
* the cpu_allowed mask is restored.
*/
static void sched_migrate_task(task_t *p, int dest_cpu)
{
migration_req_t req;
runqueue_t *rq;
unsigned long flags;
rq = task_rq_lock(p, &flags);
if (!cpu_isset(dest_cpu, p->cpus_allowed)
|| unlikely(cpu_is_offline(dest_cpu)))
goto out;
/* force the process onto the specified CPU */
if (migrate_task(p, dest_cpu, &req)) {
/* Need to wait for migration thread (might exit: take ref). */
struct task_struct *mt = rq->migration_thread;
get_task_struct(mt);
task_rq_unlock(rq, &flags);
wake_up_process(mt);
put_task_struct(mt);
wait_for_completion(&req.done);
return;
}
out:
task_rq_unlock(rq, &flags);
}
/*
* sched_exec - execve() is a valuable balancing opportunity, because at
* this point the task has the smallest effective memory and cache footprint.
*/
void sched_exec(void)
{
int new_cpu, this_cpu = get_cpu();
new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC);
put_cpu();
if (new_cpu != this_cpu)
sched_migrate_task(current, new_cpu);
}
/*
* pull_task - move a task from a remote runqueue to the local runqueue.
* Both runqueues must be locked.
*/
static
void pull_task(runqueue_t *src_rq, prio_array_t *src_array, task_t *p,
runqueue_t *this_rq, prio_array_t *this_array, int this_cpu)
{
dequeue_task(p, src_array);
src_rq->nr_running--;
set_task_cpu(p, this_cpu);
this_rq->nr_running++;
enqueue_task(p, this_array);
p->timestamp = (p->timestamp - src_rq->timestamp_last_tick)
+ this_rq->timestamp_last_tick;
/*
* Note that idle threads have a prio of MAX_PRIO, for this test
* to be always true for them.
*/
if (TASK_PREEMPTS_CURR(p, this_rq))
resched_task(this_rq->curr);
}
/*
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
*/
static
int can_migrate_task(task_t *p, runqueue_t *rq, int this_cpu,
struct sched_domain *sd, enum idle_type idle,
int *all_pinned)
{
/*
* We do not migrate tasks that are:
* 1) running (obviously), or
* 2) cannot be migrated to this CPU due to cpus_allowed, or
* 3) are cache-hot on their current CPU.
*/
if (!cpu_isset(this_cpu, p->cpus_allowed))
return 0;
*all_pinned = 0;
if (task_running(rq, p))
return 0;
/*
* Aggressive migration if:
* 1) task is cache cold, or
* 2) too many balance attempts have failed.
*/
if (sd->nr_balance_failed > sd->cache_nice_tries)
return 1;
if (task_hot(p, rq->timestamp_last_tick, sd))
return 0;
return 1;
}
/*
* move_tasks tries to move up to max_nr_move tasks from busiest to this_rq,
* as part of a balancing operation within "domain". Returns the number of
* tasks moved.
*
* Called with both runqueues locked.
*/
static int move_tasks(runqueue_t *this_rq, int this_cpu, runqueue_t *busiest,
unsigned long max_nr_move, struct sched_domain *sd,
enum idle_type idle, int *all_pinned)
{
prio_array_t *array, *dst_array;
struct list_head *head, *curr;
int idx, pulled = 0, pinned = 0;
task_t *tmp;
if (max_nr_move == 0)
goto out;
pinned = 1;
/*
* We first consider expired tasks. Those will likely not be
* executed in the near future, and they are most likely to
* be cache-cold, thus switching CPUs has the least effect
* on them.
*/
if (busiest->expired->nr_active) {
array = busiest->expired;
dst_array = this_rq->expired;
} else {
array = busiest->active;
dst_array = this_rq->active;
}
new_array:
/* Start searching at priority 0: */
idx = 0;
skip_bitmap:
if (!idx)
idx = sched_find_first_bit(array->bitmap);
else
idx = find_next_bit(array->bitmap, MAX_PRIO, idx);
if (idx >= MAX_PRIO) {
if (array == busiest->expired && busiest->active->nr_active) {
array = busiest->active;
dst_array = this_rq->active;
goto new_array;
}
goto out;
}
head = array->queue + idx;
curr = head->prev;
skip_queue:
tmp = list_entry(curr, task_t, run_list);
curr = curr->prev;
if (!can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) {
if (curr != head)
goto skip_queue;
idx++;
goto skip_bitmap;
}
#ifdef CONFIG_SCHEDSTATS
if (task_hot(tmp, busiest->timestamp_last_tick, sd))
schedstat_inc(sd, lb_hot_gained[idle]);
#endif
pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu);
pulled++;
/* We only want to steal up to the prescribed number of tasks. */
if (pulled < max_nr_move) {
if (curr != head)
goto skip_queue;
idx++;
goto skip_bitmap;
}
out:
/*
* Right now, this is the only place pull_task() is called,
* so we can safely collect pull_task() stats here rather than
* inside pull_task().
*/
schedstat_add(sd, lb_gained[idle], pulled);
if (all_pinned)
*all_pinned = pinned;
return pulled;
}
/*
* find_busiest_group finds and returns the busiest CPU group within the
* domain. It calculates and returns the number of tasks which should be
* moved to restore balance via the imbalance parameter.
*/
static struct sched_group *
find_busiest_group(struct sched_domain *sd, int this_cpu,
unsigned long *imbalance, enum idle_type idle, int *sd_idle)
{
struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
unsigned long max_load, avg_load, total_load, this_load, total_pwr;
unsigned long max_pull;
int load_idx;
max_load = this_load = total_load = total_pwr = 0;
if (idle == NOT_IDLE)
load_idx = sd->busy_idx;
else if (idle == NEWLY_IDLE)
load_idx = sd->newidle_idx;
else
load_idx = sd->idle_idx;
do {
unsigned long load;
int local_group;
int i;
local_group = cpu_isset(this_cpu, group->cpumask);
/* Tally up the load of all CPUs in the group */
avg_load = 0;
for_each_cpu_mask(i, group->cpumask) {
if (*sd_idle && !idle_cpu(i))
*sd_idle = 0;
/* Bias balancing toward cpus of our domain */
if (local_group)
load = target_load(i, load_idx);
else
load = source_load(i, load_idx);
avg_load += load;
}
total_load += avg_load;
total_pwr += group->cpu_power;
/* Adjust by relative CPU power of the group */
avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
if (local_group) {
this_load = avg_load;
this = group;
} else if (avg_load > max_load) {
max_load = avg_load;
busiest = group;
}
group = group->next;
} while (group != sd->groups);
if (!busiest || this_load >= max_load || max_load <= SCHED_LOAD_SCALE)
goto out_balanced;
avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;
if (this_load >= avg_load ||
100*max_load <= sd->imbalance_pct*this_load)
goto out_balanced;
/*
* We're trying to get all the cpus to the average_load, so we don't
* want to push ourselves above the average load, nor do we wish to
* reduce the max loaded cpu below the average load, as either of these
* actions would just result in more rebalancing later, and ping-pong
* tasks around. Thus we look for the minimum possible imbalance.
* Negative imbalances (*we* are more loaded than anyone else) will
* be counted as no imbalance for these purposes -- we can't fix that
* by pulling tasks to us. Be careful of negative numbers as they'll
* appear as very large values with unsigned longs.
*/
/* Don't want to pull so many tasks that a group would go idle */
max_pull = min(max_load - avg_load, max_load - SCHED_LOAD_SCALE);
/* How much load to actually move to equalise the imbalance */
*imbalance = min(max_pull * busiest->cpu_power,
(avg_load - this_load) * this->cpu_power)
/ SCHED_LOAD_SCALE;
if (*imbalance < SCHED_LOAD_SCALE) {
unsigned long pwr_now = 0, pwr_move = 0;
unsigned long tmp;
if (max_load - this_load >= SCHED_LOAD_SCALE*2) {
*imbalance = 1;
return busiest;
}
/*
* OK, we don't have enough imbalance to justify moving tasks,
* however we may be able to increase total CPU power used by
* moving them.
*/
pwr_now += busiest->cpu_power*min(SCHED_LOAD_SCALE, max_load);
pwr_now += this->cpu_power*min(SCHED_LOAD_SCALE, this_load);
pwr_now /= SCHED_LOAD_SCALE;
/* Amount of load we'd subtract */
tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/busiest->cpu_power;
if (max_load > tmp)
pwr_move += busiest->cpu_power*min(SCHED_LOAD_SCALE,
max_load - tmp);
/* Amount of load we'd add */
if (max_load*busiest->cpu_power <
SCHED_LOAD_SCALE*SCHED_LOAD_SCALE)
tmp = max_load*busiest->cpu_power/this->cpu_power;
else
tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/this->cpu_power;
pwr_move += this->cpu_power*min(SCHED_LOAD_SCALE, this_load + tmp);
pwr_move /= SCHED_LOAD_SCALE;
/* Move if we gain throughput */
if (pwr_move <= pwr_now)
goto out_balanced;
*imbalance = 1;
return busiest;
}
/* Get rid of the scaling factor, rounding down as we divide */
*imbalance = *imbalance / SCHED_LOAD_SCALE;
return busiest;
out_balanced:
*imbalance = 0;
return NULL;
}
/*
* find_busiest_queue - find the busiest runqueue among the cpus in group.
*/
static runqueue_t *find_busiest_queue(struct sched_group *group,
enum idle_type idle)
{
unsigned long load, max_load = 0;
runqueue_t *busiest = NULL;
int i;
for_each_cpu_mask(i, group->cpumask) {
load = source_load(i, 0);
if (load > max_load) {
max_load = load;
busiest = cpu_rq(i);
}
}
return busiest;
}
/*
* Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
* so long as it is large enough.
*/
#define MAX_PINNED_INTERVAL 512
/*
* Check this_cpu to ensure it is balanced within domain. Attempt to move
* tasks if there is an imbalance.
*
* Called with this_rq unlocked.
*/
static int load_balance(int this_cpu, runqueue_t *this_rq,
struct sched_domain *sd, enum idle_type idle)
{
struct sched_group *group;
runqueue_t *busiest;
unsigned long imbalance;
int nr_moved, all_pinned = 0;
int active_balance = 0;
int sd_idle = 0;
if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER)
sd_idle = 1;
schedstat_inc(sd, lb_cnt[idle]);
group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle);
if (!group) {
schedstat_inc(sd, lb_nobusyg[idle]);
goto out_balanced;
}
busiest = find_busiest_queue(group, idle);
if (!busiest) {
schedstat_inc(sd, lb_nobusyq[idle]);
goto out_balanced;
}
BUG_ON(busiest == this_rq);
schedstat_add(sd, lb_imbalance[idle], imbalance);
nr_moved = 0;
if (busiest->nr_running > 1) {
/*
* Attempt to move tasks. If find_busiest_group has found
* an imbalance but busiest->nr_running <= 1, the group is
* still unbalanced. nr_moved simply stays zero, so it is
* correctly treated as an imbalance.
*/
double_rq_lock(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
imbalance, sd, idle, &all_pinned);
double_rq_unlock(this_rq, busiest);
/* All tasks on this runqueue were pinned by CPU affinity */
if (unlikely(all_pinned))
goto out_balanced;
}
if (!nr_moved) {
schedstat_inc(sd, lb_failed[idle]);
sd->nr_balance_failed++;
if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
spin_lock(&busiest->lock);
/* don't kick the migration_thread, if the curr
* task on busiest cpu can't be moved to this_cpu
*/
if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) {
spin_unlock(&busiest->lock);
all_pinned = 1;
goto out_one_pinned;
}
if (!busiest->active_balance) {
busiest->active_balance = 1;
busiest->push_cpu = this_cpu;
active_balance = 1;
}
spin_unlock(&busiest->lock);
if (active_balance)
wake_up_process(busiest->migration_thread);
/*
* We've kicked active balancing, reset the failure
* counter.
*/
sd->nr_balance_failed = sd->cache_nice_tries+1;
}
} else
sd->nr_balance_failed = 0;
if (likely(!active_balance)) {
/* We were unbalanced, so reset the balancing interval */
sd->balance_interval = sd->min_interval;
} else {
/*
* If we've begun active balancing, start to back off. This
* case may not be covered by the all_pinned logic if there
* is only 1 task on the busy runqueue (because we don't call
* move_tasks).
*/
if (sd->balance_interval < sd->max_interval)
sd->balance_interval *= 2;
}
if (!nr_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER)
return -1;
return nr_moved;
out_balanced:
schedstat_inc(sd, lb_balanced[idle]);
sd->nr_balance_failed = 0;
out_one_pinned:
/* tune up the balancing interval */
if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
(sd->balance_interval < sd->max_interval))
sd->balance_interval *= 2;
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
return -1;
return 0;
}
/*
* Check this_cpu to ensure it is balanced within domain. Attempt to move
* tasks if there is an imbalance.
*
* Called from schedule when this_rq is about to become idle (NEWLY_IDLE).
* this_rq is locked.
*/
static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
struct sched_domain *sd)
{
struct sched_group *group;
runqueue_t *busiest = NULL;
unsigned long imbalance;
int nr_moved = 0;
int sd_idle = 0;
if (sd->flags & SD_SHARE_CPUPOWER)
sd_idle = 1;
schedstat_inc(sd, lb_cnt[NEWLY_IDLE]);
group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE, &sd_idle);
if (!group) {
schedstat_inc(sd, lb_nobusyg[NEWLY_IDLE]);
goto out_balanced;
}
busiest = find_busiest_queue(group, NEWLY_IDLE);
if (!busiest) {
schedstat_inc(sd, lb_nobusyq[NEWLY_IDLE]);
goto out_balanced;
}
BUG_ON(busiest == this_rq);
schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance);
nr_moved = 0;
if (busiest->nr_running > 1) {
/* Attempt to move tasks */
double_lock_balance(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
imbalance, sd, NEWLY_IDLE, NULL);
spin_unlock(&busiest->lock);
}
if (!nr_moved) {
schedstat_inc(sd, lb_failed[NEWLY_IDLE]);
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
return -1;
} else
sd->nr_balance_failed = 0;
return nr_moved;
out_balanced:
schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
return -1;
sd->nr_balance_failed = 0;
return 0;
}
/*
* idle_balance is called by schedule() if this_cpu is about to become
* idle. Attempts to pull tasks from other CPUs.
*/
static void idle_balance(int this_cpu, runqueue_t *this_rq)
{
struct sched_domain *sd;
for_each_domain(this_cpu, sd) {
if (sd->flags & SD_BALANCE_NEWIDLE) {
if (load_balance_newidle(this_cpu, this_rq, sd)) {
/* We've pulled tasks over so stop searching */
break;
}
}
}
}
/*
* active_load_balance is run by migration threads. It pushes running tasks
* off the busiest CPU onto idle CPUs. It requires at least 1 task to be
* running on each physical CPU where possible, and avoids physical /
* logical imbalances.
*
* Called with busiest_rq locked.
*/
static void active_load_balance(runqueue_t *busiest_rq, int busiest_cpu)
{
struct sched_domain *sd;
runqueue_t *target_rq;
int target_cpu = busiest_rq->push_cpu;
if (busiest_rq->nr_running <= 1)
/* no task to move */
return;
target_rq = cpu_rq(target_cpu);
/*
* This condition is "impossible", if it occurs
* we need to fix it. Originally reported by
* Bjorn Helgaas on a 128-cpu setup.
*/
BUG_ON(busiest_rq == target_rq);
/* move a task from busiest_rq to target_rq */
double_lock_balance(busiest_rq, target_rq);
/* Search for an sd spanning us and the target CPU. */
for_each_domain(target_cpu, sd)
if ((sd->flags & SD_LOAD_BALANCE) &&
cpu_isset(busiest_cpu, sd->span))
break;
if (unlikely(sd == NULL))
goto out;
schedstat_inc(sd, alb_cnt);
if (move_tasks(target_rq, target_cpu, busiest_rq, 1, sd, SCHED_IDLE, NULL))
schedstat_inc(sd, alb_pushed);
else
schedstat_inc(sd, alb_failed);
out:
spin_unlock(&target_rq->lock);
}
/*
* rebalance_tick will get called every timer tick, on every CPU.
*
* It checks each scheduling domain to see if it is due to be balanced,
* and initiates a balancing operation if so.
*
* Balancing parameters are set up in arch_init_sched_domains.
*/
/* Don't have all balancing operations going off at once */
#define CPU_OFFSET(cpu) (HZ * cpu / NR_CPUS)
static void rebalance_tick(int this_cpu, runqueue_t *this_rq,
enum idle_type idle)
{
unsigned long old_load, this_load;
unsigned long j = jiffies + CPU_OFFSET(this_cpu);
struct sched_domain *sd;
int i;
this_load = this_rq->nr_running * SCHED_LOAD_SCALE;
/* Update our load */
for (i = 0; i < 3; i++) {
unsigned long new_load = this_load;
int scale = 1 << i;
old_load = this_rq->cpu_load[i];
/*
* Round up the averaging division if load is increasing. This
* prevents us from getting stuck on 9 if the load is 10, for
* example.
*/
if (new_load > old_load)
new_load += scale-1;
this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) / scale;
}
for_each_domain(this_cpu, sd) {
unsigned long interval;
if (!(sd->flags & SD_LOAD_BALANCE))
continue;
interval = sd->balance_interval;
if (idle != SCHED_IDLE)
interval *= sd->busy_factor;
/* scale ms to jiffies */
interval = msecs_to_jiffies(interval);
if (unlikely(!interval))
interval = 1;
if (j - sd->last_balance >= interval) {
if (load_balance(this_cpu, this_rq, sd, idle)) {
/*
* We've pulled tasks over so either we're no
* longer idle, or one of our SMT siblings is
* not idle.
*/
idle = NOT_IDLE;
}
sd->last_balance += interval;
}
}
}
#else
/*
* on UP we do not need to balance between CPUs:
*/
static inline void rebalance_tick(int cpu, runqueue_t *rq, enum idle_type idle)
{
}
static inline void idle_balance(int cpu, runqueue_t *rq)
{
}
#endif
static inline int wake_priority_sleeper(runqueue_t *rq)
{
int ret = 0;
#ifdef CONFIG_SCHED_SMT
spin_lock(&rq->lock);
/*
* If an SMT sibling task has been put to sleep for priority
* reasons reschedule the idle task to see if it can now run.
*/
if (rq->nr_running) {
resched_task(rq->idle);
ret = 1;
}
spin_unlock(&rq->lock);
#endif
return ret;
}
DEFINE_PER_CPU(struct kernel_stat, kstat);
EXPORT_PER_CPU_SYMBOL(kstat);
/*
* This is called on clock ticks and on context switches.
* Bank in p->sched_time the ns elapsed since the last tick or switch.
*/
static inline void update_cpu_clock(task_t *p, runqueue_t *rq,
unsigned long long now)
{
unsigned long long last = max(p->timestamp, rq->timestamp_last_tick);
p->sched_time += now - last;
}
/*
* Return current->sched_time plus any more ns on the sched_clock
* that have not yet been banked.
*/
unsigned long long current_sched_time(const task_t *tsk)
{
unsigned long long ns;
unsigned long flags;
local_irq_save(flags);
ns = max(tsk->timestamp, task_rq(tsk)->timestamp_last_tick);
ns = tsk->sched_time + (sched_clock() - ns);
local_irq_restore(flags);
return ns;
}
/*
* We place interactive tasks back into the active array, if possible.
*
* To guarantee that this does not starve expired tasks we ignore the
* interactivity of a task if the first expired task had to wait more
* than a 'reasonable' amount of time. This deadline timeout is
* load-dependent, as the frequency of array switched decreases with
* increasing number of running tasks. We also ignore the interactivity
* if a better static_prio task has expired:
*/
#define EXPIRED_STARVING(rq) \
((STARVATION_LIMIT && ((rq)->expired_timestamp && \
(jiffies - (rq)->expired_timestamp >= \
STARVATION_LIMIT * ((rq)->nr_running) + 1))) || \
((rq)->curr->static_prio > (rq)->best_expired_prio))
/*
* Account user cpu time to a process.
* @p: the process that the cpu time gets accounted to
* @hardirq_offset: the offset to subtract from hardirq_count()
* @cputime: the cpu time spent in user space since the last update
*/
void account_user_time(struct task_struct *p, cputime_t cputime)
{
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
cputime64_t tmp;
p->utime = cputime_add(p->utime, cputime);
/* Add user time to cpustat. */
tmp = cputime_to_cputime64(cputime);
if (TASK_NICE(p) > 0)
cpustat->nice = cputime64_add(cpustat->nice, tmp);
else
cpustat->user = cputime64_add(cpustat->user, tmp);
}
/*
* Account system cpu time to a process.
* @p: the process that the cpu time gets accounted to
* @hardirq_offset: the offset to subtract from hardirq_count()
* @cputime: the cpu time spent in kernel space since the last update
*/
void account_system_time(struct task_struct *p, int hardirq_offset,
cputime_t cputime)
{
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
runqueue_t *rq = this_rq();
cputime64_t tmp;
p->stime = cputime_add(p->stime, cputime);
/* Add system time to cpustat. */
tmp = cputime_to_cputime64(cputime);
if (hardirq_count() - hardirq_offset)
cpustat->irq = cputime64_add(cpustat->irq, tmp);
else if (softirq_count())
cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
else if (p != rq->idle)
cpustat->system = cputime64_add(cpustat->system, tmp);
else if (atomic_read(&rq->nr_iowait) > 0)
cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
else
cpustat->idle = cputime64_add(cpustat->idle, tmp);
/* Account for system time used */
acct_update_integrals(p);
}
/*
* Account for involuntary wait time.
* @p: the process from which the cpu time has been stolen
* @steal: the cpu time spent in involuntary wait
*/
void account_steal_time(struct task_struct *p, cputime_t steal)
{
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
cputime64_t tmp = cputime_to_cputime64(steal);
runqueue_t *rq = this_rq();
if (p == rq->idle) {
p->stime = cputime_add(p->stime, steal);
if (atomic_read(&rq->nr_iowait) > 0)
cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
else
cpustat->idle = cputime64_add(cpustat->idle, tmp);
} else
cpustat->steal = cputime64_add(cpustat->steal, tmp);
}
/*
* This function gets called by the timer code, with HZ frequency.
* We call it with interrupts disabled.
*
* It also gets called by the fork code, when changing the parent's
* timeslices.
*/
void scheduler_tick(void)
{
int cpu = smp_processor_id();
runqueue_t *rq = this_rq();
task_t *p = current;
unsigned long long now = sched_clock();
update_cpu_clock(p, rq, now);
rq->timestamp_last_tick = now;
if (p == rq->idle) {
if (wake_priority_sleeper(rq))
goto out;
rebalance_tick(cpu, rq, SCHED_IDLE);
return;
}
/* Task might have expired already, but not scheduled off yet */
if (p->array != rq->active) {
set_tsk_need_resched(p);
goto out;
}
spin_lock(&rq->lock);
/*
* The task was running during this tick - update the
* time slice counter. Note: we do not update a thread's
* priority until it either goes to sleep or uses up its
* timeslice. This makes it possible for interactive tasks
* to use up their timeslices at their highest priority levels.
*/
if (rt_task(p)) {
/*
* RR tasks need a special form of timeslice management.
* FIFO tasks have no timeslices.
*/
if ((p->policy == SCHED_RR) && !--p->time_slice) {
p->time_slice = task_timeslice(p);
p->first_time_slice = 0;
set_tsk_need_resched(p);
/* put it at the end of the queue: */
requeue_task(p, rq->active);
}
goto out_unlock;
}
if (!--p->time_slice) {
dequeue_task(p, rq->active);
set_tsk_need_resched(p);
p->prio = effective_prio(p);
p->time_slice = task_timeslice(p);
p->first_time_slice = 0;
if (!rq->expired_timestamp)
rq->expired_timestamp = jiffies;
if (!TASK_INTERACTIVE(p) || EXPIRED_STARVING(rq)) {
enqueue_task(p, rq->expired);
if (p->static_prio < rq->best_expired_prio)
rq->best_expired_prio = p->static_prio;
} else
enqueue_task(p, rq->active);
} else {
/*
* Prevent a too long timeslice allowing a task to monopolize
* the CPU. We do this by splitting up the timeslice into
* smaller pieces.
*
* Note: this does not mean the task's timeslices expire or
* get lost in any way, they just might be preempted by
* another task of equal priority. (one with higher
* priority would have preempted this task already.) We
* requeue this task to the end of the list on this priority
* level, which is in essence a round-robin of tasks with
* equal priority.
*
* This only applies to tasks in the interactive
* delta range with at least TIMESLICE_GRANULARITY to requeue.
*/
if (TASK_INTERACTIVE(p) && !((task_timeslice(p) -
p->time_slice) % TIMESLICE_GRANULARITY(p)) &&
(p->time_slice >= TIMESLICE_GRANULARITY(p)) &&
(p->array == rq->active)) {
requeue_task(p, rq->active);
set_tsk_need_resched(p);
}
}
out_unlock:
spin_unlock(&rq->lock);
out:
rebalance_tick(cpu, rq, NOT_IDLE);
}
#ifdef CONFIG_SCHED_SMT
static inline void wakeup_busy_runqueue(runqueue_t *rq)
{
/* If an SMT runqueue is sleeping due to priority reasons wake it up */
if (rq->curr == rq->idle && rq->nr_running)
resched_task(rq->idle);
}
static void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
{
struct sched_domain *tmp, *sd = NULL;
cpumask_t sibling_map;
int i;
for_each_domain(this_cpu, tmp)
if (tmp->flags & SD_SHARE_CPUPOWER)
sd = tmp;
if (!sd)
return;
/*
* Unlock the current runqueue because we have to lock in
* CPU order to avoid deadlocks. Caller knows that we might
* unlock. We keep IRQs disabled.
*/
spin_unlock(&this_rq->lock);
sibling_map = sd->span;
for_each_cpu_mask(i, sibling_map)
spin_lock(&cpu_rq(i)->lock);
/*
* We clear this CPU from the mask. This both simplifies the
* inner loop and keps this_rq locked when we exit:
*/
cpu_clear(this_cpu, sibling_map);
for_each_cpu_mask(i, sibling_map) {
runqueue_t *smt_rq = cpu_rq(i);
wakeup_busy_runqueue(smt_rq);
}
for_each_cpu_mask(i, sibling_map)
spin_unlock(&cpu_rq(i)->lock);
/*
* We exit with this_cpu's rq still held and IRQs
* still disabled:
*/
}
/*
* number of 'lost' timeslices this task wont be able to fully
* utilize, if another task runs on a sibling. This models the
* slowdown effect of other tasks running on siblings:
*/
static inline unsigned long smt_slice(task_t *p, struct sched_domain *sd)
{
return p->time_slice * (100 - sd->per_cpu_gain) / 100;
}
static int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
{
struct sched_domain *tmp, *sd = NULL;
cpumask_t sibling_map;
prio_array_t *array;
int ret = 0, i;
task_t *p;
for_each_domain(this_cpu, tmp)
if (tmp->flags & SD_SHARE_CPUPOWER)
sd = tmp;
if (!sd)
return 0;
/*
* The same locking rules and details apply as for
* wake_sleeping_dependent():
*/
spin_unlock(&this_rq->lock);
sibling_map = sd->span;
for_each_cpu_mask(i, sibling_map)
spin_lock(&cpu_rq(i)->lock);
cpu_clear(this_cpu, sibling_map);
/*
* Establish next task to be run - it might have gone away because
* we released the runqueue lock above:
*/
if (!this_rq->nr_running)
goto out_unlock;
array = this_rq->active;
if (!array->nr_active)
array = this_rq->expired;
BUG_ON(!array->nr_active);
p = list_entry(array->queue[sched_find_first_bit(array->bitmap)].next,
task_t, run_list);
for_each_cpu_mask(i, sibling_map) {
runqueue_t *smt_rq = cpu_rq(i);
task_t *smt_curr = smt_rq->curr;
/* Kernel threads do not participate in dependent sleeping */
if (!p->mm || !smt_curr->mm || rt_task(p))
goto check_smt_task;
/*
* If a user task with lower static priority than the
* running task on the SMT sibling is trying to schedule,
* delay it till there is proportionately less timeslice
* left of the sibling task to prevent a lower priority
* task from using an unfair proportion of the
* physical cpu's resources. -ck
*/
if (rt_task(smt_curr)) {
/*
* With real time tasks we run non-rt tasks only
* per_cpu_gain% of the time.
*/
if ((jiffies % DEF_TIMESLICE) >
(sd->per_cpu_gain * DEF_TIMESLICE / 100))
ret = 1;
} else
if (smt_curr->static_prio < p->static_prio &&
!TASK_PREEMPTS_CURR(p, smt_rq) &&
smt_slice(smt_curr, sd) > task_timeslice(p))
ret = 1;
check_smt_task:
if ((!smt_curr->mm && smt_curr != smt_rq->idle) ||
rt_task(smt_curr))
continue;
if (!p->mm) {
wakeup_busy_runqueue(smt_rq);
continue;
}
/*
* Reschedule a lower priority task on the SMT sibling for
* it to be put to sleep, or wake it up if it has been put to
* sleep for priority reasons to see if it should run now.
*/
if (rt_task(p)) {
if ((jiffies % DEF_TIMESLICE) >
(sd->per_cpu_gain * DEF_TIMESLICE / 100))
resched_task(smt_curr);
} else {
if (TASK_PREEMPTS_CURR(p, smt_rq) &&
smt_slice(p, sd) > task_timeslice(smt_curr))
resched_task(smt_curr);
else
wakeup_busy_runqueue(smt_rq);
}
}
out_unlock:
for_each_cpu_mask(i, sibling_map)
spin_unlock(&cpu_rq(i)->lock);
return ret;
}
#else
static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
{
}
static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
{
return 0;
}
#endif
#if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT)
void fastcall add_preempt_count(int val)
{
/*
* Underflow?
*/
BUG_ON((preempt_count() < 0));
preempt_count() += val;
/*
* Spinlock count overflowing soon?
*/
BUG_ON((preempt_count() & PREEMPT_MASK) >= PREEMPT_MASK-10);
}
EXPORT_SYMBOL(add_preempt_count);
void fastcall sub_preempt_count(int val)
{
/*
* Underflow?
*/
BUG_ON(val > preempt_count());
/*
* Is the spinlock portion underflowing?
*/
BUG_ON((val < PREEMPT_MASK) && !(preempt_count() & PREEMPT_MASK));
preempt_count() -= val;
}
EXPORT_SYMBOL(sub_preempt_count);
#endif
static inline int interactive_sleep(enum sleep_type sleep_type)
{
return (sleep_type == SLEEP_INTERACTIVE ||
sleep_type == SLEEP_INTERRUPTED);
}
/*
* schedule() is the main scheduler function.
*/
asmlinkage void __sched schedule(void)
{
long *switch_count;
task_t *prev, *next;
runqueue_t *rq;
prio_array_t *array;
struct list_head *queue;
unsigned long long now;
unsigned long run_time;
int cpu, idx, new_prio;
/*
* Test if we are atomic. Since do_exit() needs to call into
* schedule() atomically, we ignore that path for now.
* Otherwise, whine if we are scheduling when we should not be.
*/
if (unlikely(in_atomic() && !current->exit_state)) {
printk(KERN_ERR "BUG: scheduling while atomic: "
"%s/0x%08x/%d\n",
current->comm, preempt_count(), current->pid);
dump_stack();
}
profile_hit(SCHED_PROFILING, __builtin_return_address(0));
need_resched:
preempt_disable();
prev = current;
release_kernel_lock(prev);
need_resched_nonpreemptible:
rq = this_rq();
/*
* The idle thread is not allowed to schedule!
* Remove this check after it has been exercised a bit.
*/
if (unlikely(prev == rq->idle) &&