Linux 2.6.9 Scheduler
Структура runqueue определена в kernel/sched.c
struct runqueue {
spinlock_t lock;
unsigned long nr_running;
unsigned long cpu_load;
unsigned long long nr_switches;
unsigned long expired_timestamp, nr_uninterruptible;
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;
struct sched_domain *sd;
int active_balance;
int push_cpu;
task_t *migration_thread;
struct list_head migration_queue;
};
spinlock_t lock; - блокировщик и "телохранитель"
очереди процессов. Только один процесс может модифицировать runqueue .
unsigned long nr_running; - порядковый номер задачи в очереди.
unsigned long cpu_load; - загрузка процессора
unsigned long long nr_switches; - время с последнего переключения приоритета
unsigned long nr_uninterruptible; - число задач , не
имеющих прерываний
unsigned long long timestamp_last_tick; - время последнего scheduler tick
task_t *curr; - указатель на текущий процесс
task_t *idle; - указатель на "пустышку"-процесс
struct mm_struct *prev_mm; - указатель на виртуальную память предыдущего процесса
prio_array_t *active; - массив приоритетных задач
prio_array_t *expired; - массив задач с просроченным временем
int best_expired_prio; - наивысший приоритет для всех задач
atomic_t nr_iowait; - число задач в очереди , ждущих I/O
struct sched_domain *sd; - домен , которому принадлежит очередь
int active_balance; - балансировка очереди
int push_cpu; - id процессора
struct list_head migration_queue; - список задач для миграции на много-процессорной системе
Блокировка
Только один процесс может блокировать очередь в данный момент времени.
Функция для получения 2-х последовательных блокировок - double_rq_lock(rq1, rq2) ,
и ее обратный аналог - double_rq_unlock(rq1, rq2).
Сама блокировка - task_rq_lock(task, &flags).
Массивы приоритетов
Планировщик всегда выполняет задачу с наивысшим приоритетом.
Если несколько задач имеют наивысший одинаковый приоритет ,
то вступает в силу т.н. алгоритм round-robin .
Имеются 2 массива - active и expired - для 2-х категорий задач.
unsigned int nr_active - число задач в таком массиве
unsigned long bitmap[BITMAP_SIZE] - битовый массив приоритетов задач в таком массиве задач.
Этот битовый массив позволяет оптимизировать поиск приоритетов с помощью вызова __ffs().
struct list_head queue[MAX_PRIO] - список массивов. Каждый массив включает задачи
со своим уровнем приоритета.
timeslice - время , которое отводится процессу на выполнение.
Каждый приоритет - их всего 140 - имеет свой массив. После того как задача внутри
такого массива получила шанс на выполнение и использовала его , она перемещается
на вершину этого списка .
После того как timeslice заканчивается , задача удаляется из active priority array
и перемещается в expired priority array. Когда все задачи окажутся перемещенными
в expired priority array, происходит своппинг указателей active priority array и expired priority array.
Задачи имеют статический приоритет , который колеблется в пределах от -20 до 19.
Чем выше это число , тем ниже приоритет.
Любая задача начинает свою работу с нулевого приоритета , но потом он может быть изменен
системным вызовом nice(). Статический приоритет хранится в static_prio.
Задачи также имеют динамический приоритет , который хранится в prio
Когда задача выходит из спячки , время засыпания прибавляется к sleep_avg.
Время , в течение которого процесс выполняется , вычитается из sleep_avg.
Чем выше sleep_avg , тем выше динамический приоритет у задачи.
Когда форкается новый процесс , функция wake_up_forked_thread()
уменьшает sleep_avg для родителя и потомка. Это делается для того ,
чтобы не произошло подавления со стороны более интерактивного процесса.
Каждую микросекунду срабатывает прерывание таймера - scheduler_tick().
Это событие порождает перемещение задач из expired array в active array.
Это улучшает общую интерактивность и ротацию задач в системе.
Каждый процесс имеет переменную - interactive_credit.
Чем больше спит процесс , тем выше это значение.
Если это значение больше 100 , то это высокий интерактивный приоритет.
Задачи спят по-многим причинам - иногда они могут ожидать каких-то событий
от устройств , иногда это причины программные , иногда из-за блокировки и т.д.
Во время спячки они либо могут немедленно реагировать на внешние сигналы , либо нет -
говорят , что они находятся в прерываемом либо в непрерываемом состоянии.
Waitqueue - очередь , в которой спящие задачи ожидают события .
Процесс ухода в спячку порождает следующие атомарные события :
1 Генерится DECLARE_WAIYQUEUE()
2 Вызывается add_wait_queue()
3 Задача маркируется с помощью TASK_INTERRUPTIBLE либо TASK_UNINTERRUPTIBLE
4 Вызывается цикл schedule()
5 Вызывается remove_wait_queue()
shedule() - главная функция шедулятора . Она переключает задачу и запускает ее.
sheduler_tick() играет роль часового механизма, проверяя статус текущей задачи
и выполняя балансировку очереди .
Функция shedule() каждый раз проверяет время выполнения текущей задачи.
Это время уменьшается , если выполняемая задача имеет высокий interactive credit.
Далее , если функция получает сигнал прерывания от ядра для какой-то задачи ,
эта задача получает статус TASK_RUNNING .
Далее , ищется следующая задача , если она есть в очереди на выполнение .
Если таковых нет , происходит балансировка выполняемых задач .
Файл kernel/sched.c :
/*
* 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.
*/
/*
* 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)
enum idle_type
{
IDLE,
NOT_IDLE,
NEWLY_IDLE,
MAX_IDLE_TYPES
};
struct sched_domain;
/*
* 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;
#endif
unsigned long long nr_switches;
unsigned long expired_timestamp, nr_uninterruptible;
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;
#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_noswitch;
unsigned long sched_switch;
unsigned long sched_cnt;
unsigned long sched_goidle;
/* pull_task() stats */
unsigned long pt_gained[MAX_IDLE_TYPES];
unsigned long pt_lost[MAX_IDLE_TYPES];
/* active_load_balance() stats */
unsigned long alb_cnt;
unsigned long alb_lost;
unsigned long alb_gained;
unsigned long alb_failed;
/* try_to_wake_up() stats */
unsigned long ttwu_cnt;
unsigned long ttwu_attempts;
unsigned long ttwu_moved;
/* wake_up_new_task() stats */
unsigned long wunt_cnt;
unsigned long wunt_moved;
/* sched_migrate_task() stats */
unsigned long smt_cnt;
/* sched_balance_exec() stats */
unsigned long sbe_cnt;
#endif
};
static DEFINE_PER_CPU(struct runqueue, runqueues);
/*
* sched-domains (multiprocessor balancing) declarations:
*/
#ifdef CONFIG_SMP
#define SCHED_LOAD_SCALE 128UL /* increase resolution of load */
#define SD_BALANCE_NEWIDLE 1 /* Balance when about to become idle */
#define SD_BALANCE_EXEC 2 /* Balance on exec */
#define SD_WAKE_IDLE 4 /* Wake to idle CPU on task wakeup */
#define SD_WAKE_AFFINE 8 /* Wake task to waking CPU */
#define SD_WAKE_BALANCE 16 /* Perform balancing at task wakeup */
#define SD_SHARE_CPUPOWER 32 /* Domain members share cpu power */
struct sched_group {
struct sched_group *next; /* Must be a circular list */
cpumask_t cpumask;
/*
* CPU power of this group, SCHED_LOAD_SCALE being max power for a
* single CPU. This should be read only (except for setup). Although
* it will need to be written to at cpu hot(un)plug time, perhaps the
* cpucontrol semaphore will provide enough exclusion?
*/
unsigned long cpu_power;
};
struct sched_domain {
/* These fields must be setup */
struct sched_domain *parent; /* top domain must be null terminated */
struct sched_group *groups; /* the balancing groups of the domain */
cpumask_t span; /* span of all CPUs in this domain */
unsigned long min_interval; /* Minimum balance interval ms */
unsigned long max_interval; /* Maximum balance interval ms */
unsigned int busy_factor; /* less balancing by factor if busy */
unsigned int imbalance_pct; /* No balance until over watermark */
unsigned long long cache_hot_time; /* Task considered cache hot (ns) */
unsigned int cache_nice_tries; /* Leave cache hot tasks for # tries */
unsigned int per_cpu_gain; /* CPU % gained by adding domain cpus */
int flags; /* See SD_* */
/* Runtime fields. */
unsigned long last_balance; /* init to jiffies. units in jiffies */
unsigned int balance_interval; /* initialise to 1. units in ms. */
unsigned int nr_balance_failed; /* initialise to 0 */
#ifdef CONFIG_SCHEDSTATS
/* load_balance() stats */
unsigned long lb_cnt[MAX_IDLE_TYPES];
unsigned long lb_failed[MAX_IDLE_TYPES];
unsigned long lb_imbalance[MAX_IDLE_TYPES];
unsigned long lb_nobusyg[MAX_IDLE_TYPES];
unsigned long lb_nobusyq[MAX_IDLE_TYPES];
/* sched_balance_exec() stats */
unsigned long sbe_attempts;
unsigned long sbe_pushed;
/* try_to_wake_up() stats */
unsigned long ttwu_wake_affine;
unsigned long ttwu_wake_balance;
#endif
};
#ifndef ARCH_HAS_SCHED_TUNE
#ifdef CONFIG_SCHED_SMT
#define ARCH_HAS_SCHED_WAKE_IDLE
/* Common values for SMT siblings */
#define SD_SIBLING_INIT (struct sched_domain) { \
.span = CPU_MASK_NONE, \
.parent = NULL, \
.groups = NULL, \
.min_interval = 1, \
.max_interval = 2, \
.busy_factor = 8, \
.imbalance_pct = 110, \
.cache_hot_time = 0, \
.cache_nice_tries = 0, \
.per_cpu_gain = 25, \
.flags = SD_BALANCE_NEWIDLE \
| SD_BALANCE_EXEC \
| SD_WAKE_AFFINE \
| SD_WAKE_IDLE \
| SD_SHARE_CPUPOWER, \
.last_balance = jiffies, \
.balance_interval = 1, \
.nr_balance_failed = 0, \
}
#endif
/* Common values for CPUs */
#define SD_CPU_INIT (struct sched_domain) { \
.span = CPU_MASK_NONE, \
.parent = NULL, \
.groups = NULL, \
.min_interval = 1, \
.max_interval = 4, \
.busy_factor = 64, \
.imbalance_pct = 125, \
.cache_hot_time = cache_decay_ticks*1000000 ? : (5*1000000/2),\
.cache_nice_tries = 1, \
.per_cpu_gain = 100, \
.flags = SD_BALANCE_NEWIDLE \
| SD_BALANCE_EXEC \
| SD_WAKE_AFFINE \
| SD_WAKE_BALANCE, \
.last_balance = jiffies, \
.balance_interval = 1, \
.nr_balance_failed = 0, \
}
/* Arch can override this macro in processor.h */
#if defined(CONFIG_NUMA) && !defined(SD_NODE_INIT)
#define SD_NODE_INIT (struct sched_domain) { \
.span = CPU_MASK_NONE, \
.parent = NULL, \
.groups = NULL, \
.min_interval = 8, \
.max_interval = 32, \
.busy_factor = 32, \
.imbalance_pct = 125, \
.cache_hot_time = (10*1000000), \
.cache_nice_tries = 1, \
.per_cpu_gain = 100, \
.flags = SD_BALANCE_EXEC \
| SD_WAKE_BALANCE, \
.last_balance = jiffies, \
.balance_interval = 1, \
.nr_balance_failed = 0, \
}
#endif
#endif /* ARCH_HAS_SCHED_TUNE */
#endif
#define for_each_domain(cpu, domain) \
for (domain = 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)
/*
* Default context-switch locking:
*/
#ifndef prepare_arch_switch
# define prepare_arch_switch(rq, next) do { } while (0)
# define finish_arch_switch(rq, next) spin_unlock_irq(&(rq)->lock)
# define task_running(rq, p) ((rq)->curr == (p))
#endif
/*
* 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 runqueue_t *task_rq_lock(task_t *p, unsigned long *flags)
{
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)
{
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 10
static int show_schedstat(struct seq_file *seq, void *v)
{
int cpu;
enum idle_type itype;
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 "
"%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_noswitch,
rq->sched_switch, rq->sched_cnt, rq->sched_goidle,
rq->alb_cnt, rq->alb_gained, rq->alb_lost,
rq->alb_failed,
rq->ttwu_cnt, rq->ttwu_moved, rq->ttwu_attempts,
rq->wunt_cnt, rq->wunt_moved,
rq->smt_cnt, rq->sbe_cnt, rq->rq_sched_info.cpu_time,
rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt);
for (itype = IDLE; itype < MAX_IDLE_TYPES; itype++)
seq_printf(seq, " %lu %lu", rq->pt_gained[itype],
rq->pt_lost[itype]);
seq_printf(seq, "\n");
#ifdef CONFIG_SMP
/* domain-specific stats */
for_each_domain(cpu, sd) {
char mask_str[NR_CPUS];
cpumask_scnprintf(mask_str, NR_CPUS, sd->span);
seq_printf(seq, "domain%d %s", dcnt++, mask_str);
for (itype = IDLE; itype < MAX_IDLE_TYPES; itype++) {
seq_printf(seq, " %lu %lu %lu %lu %lu",
sd->lb_cnt[itype],
sd->lb_failed[itype],
sd->lb_imbalance[itype],
sd->lb_nobusyq[itype],
sd->lb_nobusyg[itype]);
}
seq_printf(seq, " %lu %lu %lu %lu\n",
sd->sbe_pushed, sd->sbe_attempts,
sd->ttwu_wake_affine, sd->ttwu_wake_balance);
}
#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) rq->field++;
# define schedstat_add(rq, field, amt) rq->field += amt;
#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 runqueue_t *this_rq_lock(void)
{
runqueue_t *rq;
local_irq_disable();
rq = this_rq();
spin_lock(&rq->lock);
return rq;
}
static inline void rq_unlock(runqueue_t *rq)
{
spin_unlock_irq(&rq->lock);
}
#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 inline 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;
}
/*
* Used by the migration code - we pull tasks from the head of the
* remote queue so we want these tasks to show up at the head of the
* local queue:
*/
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 inline void __activate_task(task_t *p, runqueue_t *rq)
{
enqueue_task(p, rq->active);
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 void recalc_task_prio(task_t *p, unsigned long long now)
{
unsigned long long __sleep_time = now - p->timestamp;
unsigned long sleep_time;
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 and will get just interactive status to stay active &
* prevent them suddenly becoming cpu hogs and starving
* other processes.
*/
if (p->mm && p->activated != -1 &&
sleep_time > INTERACTIVE_SLEEP(p)) {
p->sleep_avg = JIFFIES_TO_NS(MAX_SLEEP_AVG -
DEF_TIMESLICE);
if (!HIGH_CREDIT(p))
p->interactive_credit++;
} else {
/*
* The lower the sleep avg a task has the more
* rapidly it will rise with sleep time.
*/
sleep_time *= (MAX_BONUS - CURRENT_BONUS(p)) ? : 1;
/*
* Tasks with low interactive_credit are limited to
* one timeslice worth of sleep avg bonus.
*/
if (LOW_CREDIT(p) &&
sleep_time > JIFFIES_TO_NS(task_timeslice(p)))
sleep_time = JIFFIES_TO_NS(task_timeslice(p));
/*
* Non high_credit tasks waking from uninterruptible
* sleep are limited in their sleep_avg rise as they
* are likely to be cpu hogs waiting on I/O
*/
if (p->activated == -1 && !HIGH_CREDIT(p) && 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;
if (!HIGH_CREDIT(p))
p->interactive_credit++;
}
}
}
p->prio = 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
recalc_task_prio(p, now);
/*
* This checks to make sure it's not an uninterruptible task
* that is now waking up.
*/
if (!p->activated) {
/*
* 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->activated = 2;
else {
/*
* Normal first-time wakeups get a credit too for
* on-runqueue time, but it will be weighted down:
*/
p->activated = 1;
}
}
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--;
if (p->state == TASK_UNINTERRUPTIBLE)
rq->nr_uninterruptible++;
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 need_resched, nrpolling;
BUG_ON(!spin_is_locked(&task_rq(p)->lock));
/* minimise the chance of sending an interrupt to poll_idle() */
nrpolling = test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
need_resched = test_and_set_tsk_thread_flag(p,TIF_NEED_RESCHED);
nrpolling |= test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
if (!need_resched && !nrpolling && (task_cpu(p) != smp_processor_id()))
smp_send_reschedule(task_cpu(p));
}
#else
static inline void resched_task(task_t *p)
{
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
enum request_type {
REQ_MOVE_TASK,
REQ_SET_DOMAIN,
};
typedef struct {
struct list_head list;
enum request_type type;
/* For REQ_MOVE_TASK */
task_t *task;
int dest_cpu;
/* For REQ_SET_DOMAIN */
struct sched_domain *sd;
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->type = REQ_MOVE_TASK;
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)) {
/* 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.)
*/
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();
}
EXPORT_SYMBOL_GPL(kick_process);
/*
* 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)
{
runqueue_t *rq = cpu_rq(cpu);
unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;
return min(rq->cpu_load, load_now);
}
/*
* Return a high guess at the load of a migration-target cpu
*/
static inline unsigned long target_load(int cpu)
{
runqueue_t *rq = cpu_rq(cpu);
unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE;
return max(rq->cpu_load, load_now);
}
#endif
/*
* wake_idle() is useful especially on SMT architectures to wake a
* task onto an idle sibling if we would otherwise wake it onto a
* busy sibling.
*
* 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;
runqueue_t *rq = cpu_rq(cpu);
struct sched_domain *sd;
int i;
if (idle_cpu(cpu))
return cpu;
sd = rq->sd;
if (!(sd->flags & SD_WAKE_IDLE))
return cpu;
cpus_and(tmp, sd->span, cpu_online_map);
cpus_and(tmp, tmp, p->cpus_allowed);
for_each_cpu_mask(i, tmp) {
if (idle_cpu(i))
return i;
}
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;
int new_cpu;
#endif
rq = task_rq_lock(p, &flags);
schedstat_inc(rq, ttwu_cnt);
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;
if (cpu == this_cpu || unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
goto out_set_cpu;
load = source_load(cpu);
this_load = target_load(this_cpu);
/*
* If sync wakeup then subtract the (maximum possible) effect of
* the currently running task from the load of the current CPU:
*/
if (sync)
this_load -= SCHED_LOAD_SCALE;
/* Don't pull the task off an idle CPU to a busy one */
if (load < SCHED_LOAD_SCALE/2 && this_load > SCHED_LOAD_SCALE/2)
goto out_set_cpu;
new_cpu = this_cpu; /* Wake to this CPU if we can */
/*
* Scan domains for affine wakeup and passive balancing
* possibilities.
*/
for_each_domain(this_cpu, sd) {
unsigned int imbalance;
/*
* Start passive balancing when half the imbalance_pct
* limit is reached.
*/
imbalance = sd->imbalance_pct + (sd->imbalance_pct - 100) / 2;
if ((sd->flags & SD_WAKE_AFFINE) &&
!task_hot(p, rq->timestamp_last_tick, sd)) {
/*
* This domain has SD_WAKE_AFFINE and p is cache cold
* in this domain.
*/
if (cpu_isset(cpu, sd->span)) {
schedstat_inc(sd, ttwu_wake_affine);
goto out_set_cpu;
}
} else if ((sd->flags & SD_WAKE_BALANCE) &&
imbalance*this_load <= 100*load) {
/*
* This domain has SD_WAKE_BALANCE and there is
* an imbalance.
*/
if (cpu_isset(cpu, sd->span)) {
schedstat_inc(sd, ttwu_wake_balance);
goto out_set_cpu;
}
}
}
new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */
out_set_cpu:
schedstat_inc(rq, ttwu_attempts);
new_cpu = wake_idle(new_cpu, p);
if (new_cpu != cpu && cpu_isset(new_cpu, p->cpus_allowed)) {
schedstat_inc(rq, ttwu_moved);
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->activated = -1;
}
/*
* 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.)
*/
activate_task(p, rq, cpu == 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);
}
#ifdef CONFIG_SMP
static int find_idlest_cpu(struct task_struct *p, int this_cpu,
struct sched_domain *sd);
#endif
/*
* Perform scheduler related setup for a newly forked process p.
* p is forked by current.
*/
void fastcall sched_fork(task_t *p)
{
/*
* 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;
spin_lock_init(&p->switch_lock);
#ifdef CONFIG_SCHEDSTATS
memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#ifdef CONFIG_PREEMPT
/*
* During context-switch we hold precisely one spinlock, which
* schedule_tail drops. (in the common case it's this_rq()->lock,
* but it also can be p->switch_lock.) So we compensate with a count
* of 1. Also, we want to start with kernel preemption disabled.
*/
p->thread_info->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;
preempt_disable();
scheduler_tick(0, 0);
local_irq_enable();
preempt_enable();
} else
local_irq_enable();
}
/*
* 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);
cpu = task_cpu(p);
this_cpu = smp_processor_id();
BUG_ON(p->state != TASK_RUNNING);
schedstat_inc(rq, wunt_cnt);
/*
* 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->interactive_credit = 0;
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, ¤t->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);
schedstat_inc(rq, wunt_moved);
/*
* 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) {
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);
}
/**
* finish_task_switch - clean up after a task-switch
* @prev: the thread we just switched away from.
*
* We enter this with the runqueue still locked, and finish_arch_switch()
* will unlock it along with doing 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 void finish_task_switch(task_t *prev)
{
runqueue_t *rq = this_rq();
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 TASK_ZOMBIE in tsk->state and calls
* schedule one last time. The schedule call will never return,
* and the scheduled task must drop that reference.
* The test for TASK_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
*/
prev_task_flags = prev->flags;
finish_arch_switch(rq, prev);
if (mm)
mmdrop(mm);
if (unlikely(prev_task_flags & PF_DEAD))
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)
{
finish_task_switch(prev);
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_cpu(i)
sum += cpu_rq(i)->nr_uninterruptible;
return sum;
}
unsigned long long nr_context_switches(void)
{
unsigned long long i, sum = 0;
for_each_cpu(i)
sum += cpu_rq(i)->nr_switches;
return sum;
}
unsigned long nr_iowait(void)
{
unsigned long i, sum = 0;
for_each_cpu(i)
sum += atomic_read(&cpu_rq(i)->nr_iowait);
return sum;
}
#ifdef CONFIG_SMP
/*
* double_rq_lock - safely lock two runqueues
*
* 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)
{
if (rq1 == rq2)
spin_lock(&rq1->lock);
else {
if (rq1 < rq2) {
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)
{
spin_unlock(&rq1->lock);
if (rq1 != rq2)
spin_unlock(&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)
{
if (unlikely(!spin_trylock(&busiest->lock))) {
if (busiest < this_rq) {
spin_unlock(&this_rq->lock);
spin_lock(&busiest->lock);
spin_lock(&this_rq->lock);
} else
spin_lock(&busiest->lock);
}
}
/*
* find_idlest_cpu - find the least busy runqueue.
*/
static int find_idlest_cpu(struct task_struct *p, int this_cpu,
struct sched_domain *sd)
{
unsigned long load, min_load, this_load;
int i, min_cpu;
cpumask_t mask;
min_cpu = UINT_MAX;
min_load = ULONG_MAX;
cpus_and(mask, sd->span, cpu_online_map);
cpus_and(mask, mask, p->cpus_allowed);
for_each_cpu_mask(i, mask) {
load = target_load(i);
if (load < min_load) {
min_cpu = i;
min_load = load;
/* break out early on an idle CPU: */
if (!min_load)
break;
}
}
/* add +1 to account for the new task */
this_load = source_load(this_cpu) + SCHED_LOAD_SCALE;
/*
* Would with the addition of the new task to the
* current CPU there be an imbalance between this
* CPU and the idlest CPU?
*
* Use half of the balancing threshold - new-context is
* a good opportunity to balance.
*/
if (min_load*(100 + (sd->imbalance_pct-100)/2) < this_load*100)
return min_cpu;
return this_cpu;
}
/*
* 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;
schedstat_inc(rq, smt_cnt);
/* 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(): find the highest-level, exec-balance-capable
* domain and try to migrate the task to the least loaded CPU.
*
* execve() is a valuable balancing opportunity, because at this point
* the task has the smallest effective memory and cache footprint.
*/
void sched_exec(void)
{
struct sched_domain *tmp, *sd = NULL;
int new_cpu, this_cpu = get_cpu();
schedstat_inc(this_rq(), sbe_cnt);
/* Prefer the current CPU if there's only this task running */
if (this_rq()->nr_running <= 1)
goto out;
for_each_domain(this_cpu, tmp)
if (tmp->flags & SD_BALANCE_EXEC)
sd = tmp;
if (sd) {
schedstat_inc(sd, sbe_attempts);
new_cpu = find_idlest_cpu(current, this_cpu, sd);
if (new_cpu != this_cpu) {
schedstat_inc(sd, sbe_pushed);
put_cpu();
sched_migrate_task(current, new_cpu);
return;
}
}
out:
put_cpu();
}
/*
* pull_task - move a task from a remote runqueue to the local runqueue.
* Both runqueues must be locked.
*/
static inline
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 inline
int can_migrate_task(task_t *p, runqueue_t *rq, int this_cpu,
struct sched_domain *sd, enum idle_type idle)
{
/*
* 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 (task_running(rq, p))
return 0;
if (!cpu_isset(this_cpu, p->cpus_allowed))
return 0;
/* Aggressive migration if we've failed balancing */
if (idle == NEWLY_IDLE ||
sd->nr_balance_failed < sd->cache_nice_tries) {
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)
{
prio_array_t *array, *dst_array;
struct list_head *head, *curr;
int idx, pulled = 0;
task_t *tmp;
if (max_nr_move <= 0 || busiest->nr_running <= 1)
goto out;
/*
* 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)) {
if (curr != head)
goto skip_queue;
idx++;
goto skip_bitmap;
}
/*
* 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_inc(this_rq, pt_gained[idle]);
schedstat_inc(busiest, pt_lost[idle]);
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:
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)
{
struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
unsigned long max_load, avg_load, total_load, this_load, total_pwr;
max_load = this_load = total_load = total_pwr = 0;
do {
cpumask_t tmp;
unsigned long load;
int local_group;
int i, nr_cpus = 0;
local_group = cpu_isset(this_cpu, group->cpumask);
/* Tally up the load of all CPUs in the group */
avg_load = 0;
cpus_and(tmp, group->cpumask, cpu_online_map);
if (unlikely(cpus_empty(tmp)))
goto nextgroup;
for_each_cpu_mask(i, tmp) {
/* Bias balancing toward cpus of our domain */
if (local_group)
load = target_load(i);
else
load = source_load(i);
nr_cpus++;
avg_load += load;
}
if (!nr_cpus)
goto nextgroup;
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;
goto nextgroup;
} else if (avg_load > max_load) {
max_load = avg_load;
busiest = group;
}
nextgroup:
group = group->next;
} while (group != sd->groups);
if (!busiest || this_load >= max_load)
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.
*/
*imbalance = min(max_load - avg_load, avg_load - this_load);
/* How much load to actually move to equalise the imbalance */
*imbalance = (*imbalance * min(busiest->cpu_power, this->cpu_power))
/ SCHED_LOAD_SCALE;
if (*imbalance < SCHED_LOAD_SCALE - 1) {
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 */
tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/this->cpu_power;
if (max_load < tmp)
tmp = max_load;
pwr_move += this->cpu_power*min(SCHED_LOAD_SCALE, this_load + tmp);
pwr_move /= SCHED_LOAD_SCALE;
/* Move if we gain another 8th of a CPU worth of throughput */
if (pwr_move < pwr_now + SCHED_LOAD_SCALE / 8)
goto out_balanced;
*imbalance = 1;
return busiest;
}
/* Get rid of the scaling factor, rounding down as we divide */
*imbalance = (*imbalance + 1) / SCHED_LOAD_SCALE;
return busiest;
out_balanced:
if (busiest && (idle == NEWLY_IDLE ||
(idle == IDLE && max_load > SCHED_LOAD_SCALE)) ) {
*imbalance = 1;
return busiest;
}
*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)
{
cpumask_t tmp;
unsigned long load, max_load = 0;
runqueue_t *busiest = NULL;
int i;
cpus_and(tmp, group->cpumask, cpu_online_map);
for_each_cpu_mask(i, tmp) {
load = source_load(i);
if (load > max_load) {
max_load = load;
busiest = cpu_rq(i);
}
}
return busiest;
}
/*
* 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;
spin_lock(&this_rq->lock);
schedstat_inc(sd, lb_cnt[idle]);
group = find_busiest_group(sd, this_cpu, &imbalance, idle);
if (!group) {
schedstat_inc(sd, lb_nobusyg[idle]);
goto out_balanced;
}
busiest = find_busiest_queue(group);
if (!busiest) {
schedstat_inc(sd, lb_nobusyq[idle]);
goto out_balanced;
}
/*
* This should be "impossible", but since load
* balancing is inherently racy and statistical,
* it could happen in theory.
*/
if (unlikely(busiest == this_rq)) {
WARN_ON(1);
goto out_balanced;
}
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_lock_balance(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
imbalance, sd, idle);
spin_unlock(&busiest->lock);
}
spin_unlock(&this_rq->lock);
if (!nr_moved) {
schedstat_inc(sd, lb_failed[idle]);
sd->nr_balance_failed++;
if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
int wake = 0;
spin_lock(&busiest->lock);
if (!busiest->active_balance) {
busiest->active_balance = 1;
busiest->push_cpu = this_cpu;
wake = 1;
}
spin_unlock(&busiest->lock);
if (wake)
wake_up_process(busiest->migration_thread);
/*
* We've kicked active balancing, reset the failure
* counter.
*/
sd->nr_balance_failed = sd->cache_nice_tries;
}
} else
sd->nr_balance_failed = 0;
/* We were unbalanced, so reset the balancing interval */
sd->balance_interval = sd->min_interval;
return nr_moved;
out_balanced:
spin_unlock(&this_rq->lock);
/* tune up the balancing interval */
if (sd->balance_interval < sd->max_interval)
sd->balance_interval *= 2;
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;
schedstat_inc(sd, lb_cnt[NEWLY_IDLE]);
group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE);
if (!group) {
schedstat_inc(sd, lb_nobusyg[NEWLY_IDLE]);
goto out;
}
busiest = find_busiest_queue(group);
if (!busiest || busiest == this_rq) {
schedstat_inc(sd, lb_nobusyq[NEWLY_IDLE]);
goto out;
}
/* Attempt to move tasks */
double_lock_balance(this_rq, busiest);
schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
imbalance, sd, NEWLY_IDLE);
if (!nr_moved)
schedstat_inc(sd, lb_failed[NEWLY_IDLE]);
spin_unlock(&busiest->lock);
out:
return nr_moved;
}
/*
* idle_balance is called by schedule() if this_cpu is about to become
* idle. Attempts to pull tasks from other CPUs.
*/
static inline 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 a running
* task off the cpu. It can be required to correctly have at least 1 task
* running on each physical CPU where possible, and not have a physical /
* logical imbalance.
*
* Called with busiest locked.
*/
static void active_load_balance(runqueue_t *busiest, int busiest_cpu)
{
struct sched_domain *sd;
struct sched_group *group, *busy_group;
int i;
schedstat_inc(busiest, alb_cnt);
if (busiest->nr_running <= 1)
return;
for_each_domain(busiest_cpu, sd)
if (cpu_isset(busiest->push_cpu, sd->span))
break;
if (!sd)
return;
group = sd->groups;
while (!cpu_isset(busiest_cpu, group->cpumask))
group = group->next;
busy_group = group;
group = sd->groups;
do {
cpumask_t tmp;
runqueue_t *rq;
int push_cpu = 0;
if (group == busy_group)
goto next_group;
cpus_and(tmp, group->cpumask, cpu_online_map);
if (!cpus_weight(tmp))
goto next_group;
for_each_cpu_mask(i, tmp) {
if (!idle_cpu(i))
goto next_group;
push_cpu = i;
}
rq = cpu_rq(push_cpu);
/*
* This condition is "impossible", but since load
* balancing is inherently a bit racy and statistical,
* it can trigger.. Reported by Bjorn Helgaas on a
* 128-cpu setup.
*/
if (unlikely(busiest == rq))
goto next_group;
double_lock_balance(busiest, rq);
if (move_tasks(rq, push_cpu, busiest, 1, sd, IDLE)) {
schedstat_inc(busiest, alb_lost);
schedstat_inc(rq, alb_gained);
} else {
schedstat_inc(busiest, alb_failed);
}
spin_unlock(&rq->lock);
next_group:
group = group->next;
} while (group != sd->groups);
}
/*
* 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;
/* Update our load */
old_load = this_rq->cpu_load;
this_load = this_rq->nr_running * SCHED_LOAD_SCALE;
/*
* 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 (this_load > old_load)
old_load++;
this_rq->cpu_load = (old_load + this_load) / 2;
for_each_domain(this_cpu, sd) {
unsigned long interval = sd->balance_interval;
if (idle != 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 no longer 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);
/*
* 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))
/*
* 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(int user_ticks, int sys_ticks)
{
int cpu = smp_processor_id();
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
runqueue_t *rq = this_rq();
task_t *p = current;
rq->timestamp_last_tick = sched_clock();
if (rcu_pending(cpu))
rcu_check_callbacks(cpu, user_ticks);
/* note: this timer irq context must be accounted for as well */
if (hardirq_count() - HARDIRQ_OFFSET) {
cpustat->irq += sys_ticks;
sys_ticks = 0;
} else if (softirq_count()) {
cpustat->softirq += sys_ticks;
sys_ticks = 0;
}
if (p == rq->idle) {
if (atomic_read(&rq->nr_iowait) > 0)
cpustat->iowait += sys_ticks;
else
cpustat->idle += sys_ticks;
if (wake_priority_sleeper(rq))
goto out;
rebalance_tick(cpu, rq, IDLE);
return;
}
if (TASK_NICE(p) > 0)
cpustat->nice += user_ticks;
else
cpustat->user += user_ticks;
cpustat->system += sys_ticks;
/* 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: */
dequeue_task(p, rq->active);
enqueue_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)) {
dequeue_task(p, rq->active);
set_tsk_need_resched(p);
p->prio = effective_prio(p);
enqueue_task(p, rq->active);
}
}
out_unlock:
spin_unlock(&rq->lock);
out:
rebalance_tick(cpu, rq, NOT_IDLE);
}
#ifdef CONFIG_SCHED_SMT
static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
{
struct sched_domain *sd = this_rq->sd;
cpumask_t sibling_map;
int i;
if (!(sd->flags & SD_SHARE_CPUPOWER))
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);
cpus_and(sibling_map, sd->span, cpu_online_map);
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);
/*
* If an SMT sibling task is sleeping due to priority
* reasons wake it up now.
*/
if (smt_rq->curr == smt_rq->idle && smt_rq->nr_running)
resched_task(smt_rq->idle);
}
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:
*/
}
static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
{
struct sched_domain *sd = this_rq->sd;
cpumask_t sibling_map;
prio_array_t *array;
int ret = 0, i;
task_t *p;
if (!(sd->flags & SD_SHARE_CPUPOWER))
return 0;
/*
* The same locking rules and details apply as for
* wake_sleeping_dependent():
*/
spin_unlock(&this_rq->lock);
cpus_and(sibling_map, sd->span, cpu_online_map);
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;
/*
* 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 (((smt_curr->time_slice * (100 - sd->per_cpu_gain) / 100) >
task_timeslice(p) || rt_task(smt_curr)) &&
p->mm && smt_curr->mm && !rt_task(p))
ret = 1;
/*
* Reschedule a lower priority task on the SMT sibling,
* or wake it up if it has been put to sleep for priority
* reasons.
*/
if ((((p->time_slice * (100 - sd->per_cpu_gain) / 100) >
task_timeslice(smt_curr) || rt_task(p)) &&
smt_curr->mm && p->mm && !rt_task(smt_curr)) ||
(smt_curr == smt_rq->idle && smt_rq->nr_running))
resched_task(smt_curr);
}
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
/*
* 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;
/*
* 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 (likely(!(current->state & (TASK_DEAD | TASK_ZOMBIE)))) {
if (unlikely(in_atomic())) {
printk(KERN_ERR "bad: scheduling while atomic!\n");
dump_stack();
}
}
need_resched:
preempt_disable();
prev = current;
rq = this_rq();
/*
* The idle thread is not allowed to schedule!
* Remove this check after it has been exercised a bit.
*/
if (unlikely(current == rq->idle) && current->state != TASK_RUNNING) {
printk(KERN_ERR "bad: scheduling from the idle thread!\n");
dump_stack();
}
release_kernel_lock(prev);
schedstat_inc(rq, sched_cnt);
now = sched_clock();
if (likely(now - prev->timestamp < NS_MAX_SLEEP_AVG))
run_time = now - prev->timestamp;
else
run_time = NS_MAX_SLEEP_AVG;
/*
* Tasks with interactive credits get charged less run_time
* at high sleep_avg to delay them losing their interactive
* status
*/
if (HIGH_CREDIT(prev))
run_time /= (CURRENT_BONUS(prev) ? : 1);
spin_lock_irq(&rq->lock);
/*
* if entering off of a kernel preemption go straight
* to picking the next task.
*/
switch_count = &prev->nivcsw;
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
switch_count = &prev->nvcsw;
if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
unlikely(signal_pending(prev))))
prev->state = TASK_RUNNING;
else
deactivate_task(prev, rq);
}
cpu = smp_processor_id();
if (unlikely(!rq->nr_running)) {
go_idle:
idle_balance(cpu, rq);
if (!rq->nr_running) {
next = rq->idle;
rq->expired_timestamp = 0;
wake_sleeping_dependent(cpu, rq);
/*
* wake_sleeping_dependent() might have released
* the runqueue, so break out if we got new
* tasks meanwhile:
*/
if (!rq->nr_running)
goto switch_tasks;
}
} else {
if (dependent_sleeper(cpu, rq)) {
schedstat_inc(rq, sched_goidle);
next = rq->idle;
goto switch_tasks;
}
/*
* dependent_sleeper() releases and reacquires the runqueue
* lock, hence go into the idle loop if the rq went
* empty meanwhile:
*/
if (unlikely(!rq->nr_running))
goto go_idle;
}
array = rq->active;
if (unlikely(!array->nr_active)) {
/*
* Switch the active and expired arrays.
*/
schedstat_inc(rq, sched_switch);
rq->active = rq->expired;
rq->expired = array;
array = rq->active;
rq->expired_timestamp = 0;
rq->best_expired_prio = MAX_PRIO;
} else
schedstat_inc(rq, sched_noswitch);
idx = sched_find_first_bit(array->bitmap);
queue = array->queue + idx;
next = list_entry(queue->next, task_t, run_list);
if (!rt_task(next) && next->activated > 0) {
unsigned long long delta = now - next->timestamp;
if (next->activated == 1)
delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
array = next->array;
dequeue_task(next, array);
recalc_task_prio(next, next->timestamp + delta);
enqueue_task(next, array);
}
next->activated = 0;
switch_tasks:
prefetch(next);
clear_tsk_need_resched(prev);
rcu_qsctr_inc(task_cpu(prev));
prev->sleep_avg -= run_time;
if ((long)prev->sleep_avg <= 0) {
prev->sleep_avg = 0;
if (!(HIGH_CREDIT(prev) || LOW_CREDIT(prev)))
prev->interactive_credit--;
}
prev->timestamp = prev->last_ran = now;
sched_info_switch(prev, next);
if (likely(prev != next)) {
next->timestamp = now;
rq->nr_switches++;
rq->curr = next;
++*switch_count;
prepare_arch_switch(rq, next);
prev = context_switch(rq, prev, next);
barrier();
finish_task_switch(prev);
} else
spin_unlock_irq(&rq->lock);
reacquire_kernel_lock(current);
preempt_enable_no_resched();
if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
goto need_resched;
}
EXPORT_SYMBOL(schedule);
#ifdef CONFIG_PREEMPT
/*
* this is is the entry point to schedule() from in-kernel preemption
* off of preempt_enable. Kernel preemptions off return from interrupt
* occur there and call schedule directly.
*/
asmlinkage void __sched preempt_schedule(void)
{
struct thread_info *ti = current_thread_info();
/*
* If there is a non-zero preempt_count or interrupts are disabled,
* we do not want to preempt the current task. Just return..
*/
if (unlikely(ti->preempt_count || irqs_disabled()))
return;
need_resched:
ti->preempt_count = PREEMPT_ACTIVE;
schedule();
ti->preempt_count = 0;
/* we could miss a preemption opportunity between schedule and now */
barrier();
if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
goto need_resched;
}
EXPORT_SYMBOL(preempt_schedule);
#endif /* CONFIG_PREEMPT */
int default_wake_function(wait_queue_t *curr, unsigned mode, int sync, void *key)
{
task_t *p = curr->task;
return try_to_wake_up(p, mode, sync);
}
EXPORT_SYMBOL(default_wake_function);
/*
* The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
* wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
* number) then we wake all the non-exclusive tasks and one exclusive task.
*
* There are circumstances in which we can try to wake a task which has already
* started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
* zero in this (rare) case, and we handle it by continuing to scan the queue.
*/
static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
int nr_exclusive, int sync, void *key)
{
struct list_head *tmp, *next;
list_for_each_safe(tmp, next, &q->task_list) {
wait_queue_t *curr;
unsigned flags;
curr = list_entry(tmp, wait_queue_t, task_list);
flags = curr->flags;
if (curr->func(curr, mode, sync, key) &&
(flags & WQ_FLAG_EXCLUSIVE) &&
!--nr_exclusive)
break;
}
}
/**
* __wake_up - wake up threads blocked on a waitqueue.
* @q: the waitqueue
* @mode: which threads
* @nr_exclusive: how many wake-one or wake-many threads to wake up
*/
void fastcall __wake_up(wait_queue_head_t *q, unsigned int mode,
int nr_exclusive, void *key)
{
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
__wake_up_common(q, mode, nr_exclusive, 0, key);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(__wake_up);
/*
* Same as __wake_up but called with the spinlock in wait_queue_head_t held.
*/
void fastcall __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
{
__wake_up_common(q, mode, 1, 0, NULL);
}
/**
* __wake_up - sync- wake up threads blocked on a waitqueue.
* @q: the waitqueue
* @mode: which threads
* @nr_exclusive: how many wake-one or wake-many threads to wake up
*
* The sync wakeup differs that the waker knows that it will schedule
* away soon, so while the target thread will be woken up, it will not
* be migrated to another CPU - ie. the two threads are 'synchronized'
* with each other. This can prevent needless bouncing between CPUs.
*
* On UP it can prevent extra preemption.
*/
void fastcall __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
{
unsigned long flags;
int sync = 1;
if (unlikely(!q))
return;
if (unlikely(!nr_exclusive))
sync = 0;
spin_lock_irqsave(&q->lock, flags);
__wake_up_common(q, mode, nr_exclusive, sync, NULL);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
void fastcall complete(struct completion *x)
{
unsigned long flags;
spin_lock_irqsave(&x->wait.lock, flags);
x->done++;
__wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
1, 0, NULL);
spin_unlock_irqrestore(&x->wait.lock, flags);
}
EXPORT_SYMBOL(complete);
void fastcall complete_all(struct completion *x)
{
unsigned long flags;
spin_lock_irqsave(&x->wait.lock, flags);
x->done += UINT_MAX/2;
__wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
0, 0, NULL);
spin_unlock_irqrestore(&x->wait.lock, flags);
}
EXPORT_SYMBOL(complete_all);
void fastcall __sched wait_for_completion(struct completion *x)
{
might_sleep();
spin_lock_irq(&x->wait.lock);
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(&x->wait, &wait);
do {
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
schedule();
spin_lock_irq(&x->wait.lock);
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
spin_unlock_irq(&x->wait.lock);
}
EXPORT_SYMBOL(wait_for_completion);
#define SLEEP_ON_VAR \
unsigned long flags; \
wait_queue_t wait; \
init_waitqueue_entry(&wait, current);
#define SLEEP_ON_HEAD \
spin_lock_irqsave(&q->lock,flags); \
__add_wait_queue(q, &wait); \
spin_unlock(&q->lock);
#define SLEEP_ON_TAIL \
spin_lock_irq(&q->lock); \
__remove_wait_queue(q, &wait); \
spin_unlock_irqrestore(&q->lock, flags);
void fastcall __sched interruptible_sleep_on(wait_queue_head_t *q)
{
SLEEP_ON_VAR
current->state = TASK_INTERRUPTIBLE;
SLEEP_ON_HEAD
schedule();
SLEEP_ON_TAIL
}
EXPORT_SYMBOL(interruptible_sleep_on);
long fastcall __sched interruptible_sleep_on_timeout(wait_queue_head_t *q,
long timeout)
{
SLEEP_ON_VAR
current->state = TASK_INTERRUPTIBLE;
SLEEP_ON_HEAD
timeout = schedule_timeout(timeout);
SLEEP_ON_TAIL
return timeout;
}
EXPORT_SYMBOL(interruptible_sleep_on_timeout);
void fastcall __sched sleep_on(wait_queue_head_t *q)
{
SLEEP_ON_VAR
current->state = TASK_UNINTERRUPTIBLE;
SLEEP_ON_HEAD
schedule();
SLEEP_ON_TAIL
}
EXPORT_SYMBOL(sleep_on);
long fastcall __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
{
SLEEP_ON_VAR
current->state = TASK_UNINTERRUPTIBLE;
SLEEP_ON_HEAD
timeout = schedule_timeout(timeout);
SLEEP_ON_TAIL
return timeout;
}
EXPORT_SYMBOL(sleep_on_timeout);
void set_user_nice(task_t *p, long nice)
{
unsigned long flags;
prio_array_t *array;
runqueue_t *rq;
int old_prio, new_prio, delta;
if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
return;
/*
* We have to be careful, if called from sys_setpriority(),
* the task might be in the middle of scheduling on another CPU.
*/
rq = task_rq_lock(p, &flags);
/*
* The RT priorities are set via setscheduler(), but we still
* allow the 'normal' nice value to be set - but as expected
* it wont have any effect on scheduling until the task is
* not SCHED_NORMAL:
*/
if (rt_task(p)) {
p->static_prio = NICE_TO_PRIO(nice);
goto out_unlock;
}
array = p->array;
if (array)
dequeue_task(p, array);
old_prio = p->prio;
new_prio = NICE_TO_PRIO(nice);
delta = new_prio - old_prio;
p->static_prio = NICE_TO_PRIO(nice);
p->prio += delta;
if (array) {
enqueue_task(p, array);
/*
* If the task increased its priority or is running and
* lowered its priority, then reschedule its CPU:
*/
if (delta < 0 || (delta > 0 && task_running(rq, p)))
resched_task(rq->curr);
}
out_unlock:
task_rq_unlock(rq, &flags);
}
EXPORT_SYMBOL(set_user_nice);
#ifdef __ARCH_WANT_SYS_NICE
/*
* sys_nice - change the priority of the current process.
* @increment: priority increment
*
* sys_setpriority is a more generic, but much slower function that
* does similar things.
*/
asmlinkage long sys_nice(int increment)
{
int retval;
long nice;
/*
* Setpriority might change our priority at the same moment.
* We don't have to worry. Conceptually one call occurs first
* and we have a single winner.
*/
if (increment < 0) {
if (!capable(CAP_SYS_NICE))
return -EPERM;
if (increment < -40)
increment = -40;
}
if (increment > 40)
increment = 40;
nice = PRIO_TO_NICE(current->static_prio) + increment;
if (nice < -20)
nice = -20;
if (nice > 19)
nice = 19;
retval = security_task_setnice(current, nice);
if (retval)
return retval;
set_user_nice(current, nice);
return 0;
}
#endif
/**
* task_prio - return the priority value of a given task.
* @p: the task in question.
*
* This is the priority value as seen by users in /proc.
* RT tasks are offset by -200. Normal tasks are centered
* around 0, value goes from -16 to +15.
*/
int task_prio(const task_t *p)
{
return p->prio - MAX_RT_PRIO;
}
/**
* task_nice - return the nice value of a given task.
* @p: the task in question.
*/
int task_nice(const task_t *p)
{
return TASK_NICE(p);
}
EXPORT_SYMBOL(task_nice);
/**
* idle_cpu - is a given cpu idle currently?
* @cpu: the processor in question.
*/
int idle_cpu(int cpu)
{
return cpu_curr(cpu) == cpu_rq(cpu)->idle;
}
EXPORT_SYMBOL_GPL(idle_cpu);
/**
* find_process_by_pid - find a process with a matching PID value.
* @pid: the pid in question.
*/
static inline task_t *find_process_by_pid(pid_t pid)
{
return pid ? find_task_by_pid(pid) : current;
}
/* Actually do priority change: must hold rq lock. */
static void __setscheduler(struct task_struct *p, int policy, int prio)
{
BUG_ON(p->array);
p->policy = policy;
p->rt_priority = prio;
if (policy != SCHED_NORMAL)
p->prio = MAX_USER_RT_PRIO-1 - p->rt_priority;
else
p->prio = p->static_prio;
}
/*
* setscheduler - change the scheduling policy and/or RT priority of a thread.
*/
static int setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
struct sched_param lp;
int retval = -EINVAL;
int oldprio;
prio_array_t *array;
unsigned long flags;
runqueue_t *rq;
task_t *p;
if (!param || pid < 0)
goto out_nounlock;
retval = -EFAULT;
if (copy_from_user(&lp, param, sizeof(struct sched_param)))
goto out_nounlock;
/*
* We play safe to avoid deadlocks.
*/
read_lock_irq(&tasklist_lock);
p = find_process_by_pid(pid);
retval = -ESRCH;
if (!p)
goto out_unlock_tasklist;
/*
* To be able to change p->policy safely, the apropriate
* runqueue lock must be held.
*/
rq = task_rq_lock(p, &flags);
if (policy < 0)
policy = p->policy;
else {
retval = -EINVAL;
if (policy != SCHED_FIFO && policy != SCHED_RR &&
policy != SCHED_NORMAL)
goto out_unlock;
}
profile_hit(SCHED_PROFILING, __builtin_return_address(0));
/*
* Valid priorities for SCHED_FIFO and SCHED_RR are
* 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL is 0.
*/
retval = -EINVAL;
if (lp.sched_priority < 0 || lp.sched_priority > MAX_USER_RT_PRIO-1)
goto out_unlock;
if ((policy == SCHED_NORMAL) != (lp.sched_priority == 0))
goto out_unlock;
retval = -EPERM;
if ((policy == SCHED_FIFO || policy == SCHED_RR) &&
!capable(CAP_SYS_NICE))
goto out_unlock;
if ((current->euid != p->euid) && (current->euid != p->uid) &&
!capable(CAP_SYS_NICE))
goto out_unlock;
retval = security_task_setscheduler(p, policy, &lp);
if (retval)
goto out_unlock;
array = p->array;
if (array)
deactivate_task(p, task_rq(p));
retval = 0;
oldprio = p->prio;
__setscheduler(p, policy, lp.sched_priority);
if (array) {
__activate_task(p, task_rq(p));
/*
* Reschedule if we are currently running on this runqueue and
* our priority decreased, or if we are not currently running on
* this runqueue and our priority is higher than the current's
*/
if (task_running(rq, p)) {
if (p->prio > oldprio)
resched_task(rq->curr);
} else if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
}
out_unlock:
task_rq_unlock(rq, &flags);
out_unlock_tasklist:
read_unlock_irq(&tasklist_lock);
out_nounlock:
return retval;
}
/**
* sys_sched_setscheduler - set/change the scheduler policy and RT priority
* @pid: the pid in question.
* @policy: new policy
* @param: structure containing the new RT priority.
*/
asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
struct sched_param __user *param)
{
return setscheduler(pid, policy, param);
}
/**
* sys_sched_setparam - set/change the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the new RT priority.
*/
asmlinkage long sys_sched_setparam(pid_t pid, struct sched_param __user *param)
{
return setscheduler(pid, -1, param);
}
/**
* sys_sched_getscheduler - get the policy (scheduling class) of a thread
* @pid: the pid in question.
*/
asmlinkage long sys_sched_getscheduler(pid_t pid)
{
int retval = -EINVAL;
task_t *p;
if (pid < 0)
goto out_nounlock;
retval = -ESRCH;
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (p) {
retval = security_task_getscheduler(p);
if (!retval)
retval = p->policy;
}
read_unlock(&tasklist_lock);
out_nounlock:
return retval;
}
/**
* sys_sched_getscheduler - get the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the RT priority.
*/
asmlinkage long sys_sched_getparam(pid_t pid, struct sched_param __user *param)
{
struct sched_param lp;
int retval = -EINVAL;
task_t *p;
if (!param || pid < 0)
goto out_nounlock;
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
retval = -ESRCH;
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
lp.sched_priority = p->rt_priority;
read_unlock(&tasklist_lock);
/*
* This one might sleep, we cannot do it with a spinlock held ...
*/
retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
out_nounlock:
return retval;
out_unlock:
read_unlock(&tasklist_lock);
return retval;
}
long sched_setaffinity(pid_t pid, cpumask_t new_mask)
{
task_t *p;
int retval;
lock_cpu_hotplug();
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (!p) {
read_unlock(&tasklist_lock);
unlock_cpu_hotplug();
return -ESRCH;
}
/*
* It is not safe to call set_cpus_allowed with the
* tasklist_lock held. We will bump the task_struct's
* usage count and then drop tasklist_lock.
*/
get_task_struct(p);
read_unlock(&tasklist_lock);
retval = -EPERM;
if ((current->euid != p->euid) && (current->euid != p->uid) &&
!capable(CAP_SYS_NICE))
goto out_unlock;
retval = set_cpus_allowed(p, new_mask);
out_unlock:
put_task_struct(p);
unlock_cpu_hotplug();
return retval;
}
static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
cpumask_t *new_mask)
{
if (len < sizeof(cpumask_t)) {
memset(new_mask, 0, sizeof(cpumask_t));
} else if (len > sizeof(cpumask_t)) {
len = sizeof(cpumask_t);
}
return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
}
/**
* sys_sched_setaffinity - set the cpu affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to the new cpu mask
*/
asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
unsigned long __user *user_mask_ptr)
{
cpumask_t new_mask;
int retval;
retval = get_user_cpu_mask(user_mask_ptr, len, &new_mask);
if (retval)
return retval;
return sched_setaffinity(pid, new_mask);
}
/*
* Represents all cpu's present in the system
* In systems capable of hotplug, this map could dynamically grow
* as new cpu's are detected in the system via any platform specific
* method, such as ACPI for e.g.
*/
cpumask_t cpu_present_map;
EXPORT_SYMBOL(cpu_present_map);
#ifndef CONFIG_SMP
cpumask_t cpu_online_map = CPU_MASK_ALL;
cpumask_t cpu_possible_map = CPU_MASK_ALL;
#endif
long sched_getaffinity(pid_t pid, cpumask_t *mask)
{
int retval;
task_t *p;
lock_cpu_hotplug();
read_lock(&tasklist_lock);
retval = -ESRCH;
p = find_process_by_pid(pid);
if (!p)
goto out_unlock;
retval = 0;
cpus_and(*mask, p->cpus_allowed, cpu_possible_map);
out_unlock:
read_unlock(&tasklist_lock);
unlock_cpu_hotplug();
if (retval)
return retval;
return 0;
}
/**
* sys_sched_getaffinity - get the cpu affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to hold the current cpu mask
*/
asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
unsigned long __user *user_mask_ptr)
{
int ret;
cpumask_t mask;
if (len < sizeof(cpumask_t))
return -EINVAL;
ret = sched_getaffinity(pid, &mask);
if (ret < 0)
return ret;
if (copy_to_user(user_mask_ptr, &mask, sizeof(cpumask_t)))
return -EFAULT;
return sizeof(cpumask_t);
}
/**
* sys_sched_yield - yield the current processor to other threads.
*
* this function yields the current CPU by moving the calling thread
* to the expired array. If there are no other threads running on this
* CPU then this function will return.
*/
asmlinkage long sys_sched_yield(void)
{
runqueue_t *rq = this_rq_lock();
prio_array_t *array = current->array;
prio_array_t *target = rq->expired;
schedstat_inc(rq, yld_cnt);
/*
* We implement yielding by moving the task into the expired
* queue.
*
* (special rule: RT tasks will just roundrobin in the active
* array.)
*/
if (rt_task(current))
target = rq->active;
if (current->array->nr_active == 1) {
schedstat_inc(rq, yld_act_empty);
if (!rq->expired->nr_active)
schedstat_inc(rq, yld_both_empty);
} else if (!rq->expired->nr_active)
schedstat_inc(rq, yld_exp_empty);
dequeue_task(current, array);
enqueue_task(current, target);
/*
* Since we are going to call schedule() anyway, there's
* no need to preempt or enable interrupts:
*/
_raw_spin_unlock(&rq->lock);
preempt_enable_no_resched();
schedule();
return 0;
}
void __sched __cond_resched(void)
{
set_current_state(TASK_RUNNING);
schedule();
}
EXPORT_SYMBOL(__cond_resched);
/**
* yield - yield the current processor to other threads.
*
* this is a shortcut for kernel-space yielding - it marks the
* thread runnable and calls sys_sched_yield().
*/
void __sched yield(void)
{
set_current_state(TASK_RUNNING);
sys_sched_yield();
}
EXPORT_SYMBOL(yield);
/*
* This task is about to go to sleep on IO. Increment rq->nr_iowait so
* that process accounting knows that this is a task in IO wait state.
*
* But don't do that if it is a deliberate, throttling IO wait (this task
* has set its backing_dev_info: the queue against which it should throttle)
*/
void __sched io_schedule(void)
{
struct runqueue *rq = this_rq();
atomic_inc(&rq->nr_iowait);
schedule();
atomic_dec(&rq->nr_iowait);
}
EXPORT_SYMBOL(io_schedule);
long __sched io_schedule_timeout(long timeout)
{
struct runqueue *rq = this_rq();
long ret;
atomic_inc(&rq->nr_iowait);
ret = schedule_timeout(timeout);
atomic_dec(&rq->nr_iowait);
return ret;
}
/**
* sys_sched_get_priority_max - return maximum RT priority.
* @policy: scheduling class.
*
* this syscall returns the maximum rt_priority that can be used
* by a given scheduling class.
*/
asmlinkage long sys_sched_get_priority_max(int policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = MAX_USER_RT_PRIO-1;
break;
case SCHED_NORMAL:
ret = 0;
break;
}
return ret;
}
/**
* sys_sched_get_priority_min - return minimum RT priority.
* @policy: scheduling class.
*
* this syscall returns the minimum rt_priority that can be used
* by a given scheduling class.
*/
asmlinkage long sys_sched_get_priority_min(int policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = 1;
break;
case SCHED_NORMAL:
ret = 0;
}
return ret;
}
/**
* sys_sched_rr_get_interval - return the default timeslice of a process.
* @pid: pid of the process.
* @interval: userspace pointer to the timeslice value.
*
* this syscall writes the default timeslice value of a given process
* into the user-space timespec buffer. A value of '0' means infinity.
*/
asmlinkage
long sys_sched_rr_get_interval(pid_t pid, struct timespec __user *interval)
{
int retval = -EINVAL;
struct timespec t;
task_t *p;
if (pid < 0)
goto out_nounlock;
retval = -ESRCH;
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
jiffies_to_timespec(p->policy & SCHED_FIFO ?
0 : task_timeslice(p), &t);
read_unlock(&tasklist_lock);
retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
out_nounlock:
return retval;
out_unlock:
read_unlock(&tasklist_lock);
return retval;
}
static inline struct task_struct *eldest_child(struct task_struct *p)
{
if (list_empty(&p->children)) return NULL;
return list_entry(p->children.next,struct task_struct,sibling);
}
static inline struct task_struct *older_sibling(struct task_struct *p)
{
if (p->sibling.prev==&p->parent->children) return NULL;
return list_entry(p->sibling.prev,struct task_struct,sibling);
}
static inline struct task_struct *younger_sibling(struct task_struct *p)
{
if (p->sibling.next==&p->parent->children) return NULL;
return list_entry(p->sibling.next,struct task_struct,sibling);
}
static void show_task(task_t * p)
{
task_t *relative;
unsigned state;
unsigned long free = 0;
static const char *stat_nam[] = { "R", "S", "D", "T", "t", "Z", "X" };
printk("%-13.13s ", p->comm);
state = p->state ? __ffs(p->state) + 1 : 0;
if (state < ARRAY_SIZE(stat_nam))
printk(stat_nam[state]);
else
printk("?");
#if (BITS_PER_LONG == 32)
if (state == TASK_RUNNING)
printk(" running ");
else
printk(" %08lX ", thread_saved_pc(p));
#else
if (state == TASK_RUNNING)
printk(" running task ");
else
printk(" %016lx ", thread_saved_pc(p));
#endif
#ifdef CONFIG_DEBUG_STACK_USAGE
{
unsigned long * n = (unsigned long *) (p->thread_info+1);
while (!*n)
n++;
free = (unsigned long) n - (unsigned long)(p->thread_info+1);
}
#endif
printk("%5lu %5d %6d ", free, p->pid, p->parent->pid);
if ((relative = eldest_child(p)))
printk("%5d ", relative->pid);
else
printk(" ");
if ((relative = younger_sibling(p)))
printk("%7d", relative->pid);
else
printk(" ");
if ((relative = older_sibling(p)))
printk(" %5d", relative->pid);
else
printk(" ");
if (!p->mm)
printk(" (L-TLB)\n");
else
printk(" (NOTLB)\n");
if (state != TASK_RUNNING)
show_stack(p, NULL);
}
void show_state(void)
{
task_t *g, *p;
#if (BITS_PER_LONG == 32)
printk("\n"
" sibling\n");
printk(" task PC pid father child younger older\n");
#else
printk("\n"
" sibling\n");
printk(" task PC pid father child younger older\n");
#endif
read_lock(&tasklist_lock);
do_each_thread(g, p) {
/*
* reset the NMI-timeout, listing all files on a slow
* console might take alot of time:
*/
touch_nmi_watchdog();
show_task(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
}
void __devinit init_idle(task_t *idle, int cpu)
{
runqueue_t *rq = cpu_rq(cpu);
unsigned long flags;
idle->sleep_avg = 0;
idle->interactive_credit = 0;
idle->array = NULL;
idle->prio = MAX_PRIO;
idle->state = TASK_RUNNING;
set_task_cpu(idle, cpu);
spin_lock_irqsave(&rq->lock, flags);
rq->curr = rq->idle = idle;
set_tsk_need_resched(idle);
spin_unlock_irqrestore(&rq->lock, flags);
/* Set the preempt count _outside_ the spinlocks! */
#ifdef CONFIG_PREEMPT
idle->thread_info->preempt_count = (idle->lock_depth >= 0);
#else
idle->thread_info->preempt_count = 0;
#endif
}
/*
* In a system that switches off the HZ timer nohz_cpu_mask
* indicates which cpus entered this state. This is used
* in the rcu update to wait only for active cpus. For system
* which do not switch off the HZ timer nohz_cpu_mask should
* always be CPU_MASK_NONE.
*/
cpumask_t nohz_cpu_mask = CPU_MASK_NONE;
#ifdef CONFIG_SMP
/*
* This is how migration works:
*
* 1) we queue a migration_req_t structure in the source CPU's
* runqueue and wake up that CPU's migration thread.
* 2) we down() the locked semaphore => thread blocks.
* 3) migration thread wakes up (implicitly it forces the migrated
* thread off the CPU)
* 4) it gets the migration request and checks whether the migrated
* task is still in the wrong runqueue.
* 5) if it's in the wrong runqueue then the migration thread removes
* it and puts it into the right queue.
* 6) migration thread up()s the semaphore.
* 7) we wake up and the migration is done.
*/
/*
* Change a given task's CPU affinity. Migrate the thread to a
* proper CPU and schedule it away if the CPU it's executing on
* is removed from the allowed bitmask.
*
* NOTE: the caller must have a valid reference to the task, the
* task must not exit() & deallocate itself prematurely. The
* call is not atomic; no spinlocks may be held.
*/
int set_cpus_allowed(task_t *p, cpumask_t new_mask)
{
unsigned long flags;
int ret = 0;
migration_req_t req;
runqueue_t *rq;
rq = task_rq_lock(p, &flags);
if (!cpus_intersects(new_mask, cpu_online_map)) {
ret = -EINVAL;
goto out;
}
p->cpus_allowed = new_mask;
/* Can the task run on the task's current CPU? If so, we're done */
if (cpu_isset(task_cpu(p), new_mask))
goto out;
if (migrate_task(p, any_online_cpu(new_mask), &req)) {
/* Need help from migration thread: drop lock and wait. */
task_rq_unlock(rq, &flags);
wake_up_process(rq->migration_thread);
wait_for_completion(&req.done);
tlb_migrate_finish(p->mm);
return 0;
}
out:
task_rq_unlock(rq, &flags);
return ret;
}
EXPORT_SYMBOL_GPL(set_cpus_allowed);
/*
* Move (not current) task off this cpu, onto dest cpu. We're doing
* this because either it can't run here any more (set_cpus_allowed()
* away from this CPU, or CPU going down), or because we're
* attempting to rebalance this task on exec (sched_exec).
*
* So we race with normal scheduler movements, but that's OK, as long
* as the task is no longer on this CPU.
*/
static void __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
runqueue_t *rq_dest, *rq_src;
if (unlikely(cpu_is_offline(dest_cpu)))
return;
rq_src = cpu_rq(src_cpu);
rq_dest = cpu_rq(dest_cpu);
double_rq_lock(rq_src, rq_dest);
/* Already moved. */
if (task_cpu(p) != src_cpu)
goto out;
/* Affinity changed (again). */
if (!cpu_isset(dest_cpu, p->cpus_allowed))
goto out;
set_task_cpu(p, dest_cpu);
if (p->array) {
/*
* Sync timestamp with rq_dest's before activating.
* The same thing could be achieved by doing this step
* afterwards, and pretending it was a local activate.
* This way is cleaner and logically correct.
*/
p->timestamp = p->timestamp - rq_src->timestamp_last_tick
+ rq_dest->timestamp_last_tick;
deactivate_task(p, rq_src);
activate_task(p, rq_dest, 0);
if (TASK_PREEMPTS_CURR(p, rq_dest))
resched_task(rq_dest->curr);
}
out:
double_rq_unlock(rq_src, rq_dest);
}
/*
* migration_thread - this is a highprio system thread that performs
* thread migration by bumping thread off CPU then 'pushing' onto
* another runqueue.
*/
static int migration_thread(void * data)
{
runqueue_t *rq;
int cpu = (long)data;
rq = cpu_rq(cpu);
BUG_ON(rq->migration_thread != current);
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
struct list_head *head;
migration_req_t *req;
if (current->flags & PF_FREEZE)
refrigerator(PF_FREEZE);
spin_lock_irq(&rq->lock);
if (cpu_is_offline(cpu)) {
spin_unlock_irq(&rq->lock);
goto wait_to_die;
}
if (rq->active_balance) {
active_load_balance(rq, cpu);
rq->active_balance = 0;
}
head = &rq->migration_queue;
if (list_empty(head)) {
spin_unlock_irq(&rq->lock);
schedule();
set_current_state(TASK_INTERRUPTIBLE);
continue;
}
req = list_entry(head->next, migration_req_t, list);
list_del_init(head->next);
if (req->type == REQ_MOVE_TASK) {
spin_unlock(&rq->lock);
__migrate_task(req->task, smp_processor_id(),
req->dest_cpu);
local_irq_enable();
} else if (req->type == REQ_SET_DOMAIN) {
rq->sd = req->sd;
spin_unlock_irq(&rq->lock);
} else {
spin_unlock_irq(&rq->lock);
WARN_ON(1);
}
complete(&req->done);
}
__set_current_state(TASK_RUNNING);
return 0;
wait_to_die:
/* Wait for kthread_stop */
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
schedule();
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
return 0;
}
#ifdef CONFIG_HOTPLUG_CPU
/* Figure out where task on dead CPU should go, use force if neccessary. */
static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *tsk)
{
int dest_cpu;
cpumask_t mask;
/* On same node? */
mask = node_to_cpumask(cpu_to_node(dead_cpu));
cpus_and(mask, mask, tsk->cpus_allowed);
dest_cpu = any_online_cpu(mask);
/* On any allowed CPU? */
if (dest_cpu == NR_CPUS)
dest_cpu = any_online_cpu(tsk->cpus_allowed);
/* No more Mr. Nice Guy. */
if (dest_cpu == NR_CPUS) {
cpus_setall(tsk->cpus_allowed);
dest_cpu = any_online_cpu(tsk->cpus_allowed);
/*
* Don't tell them about moving exiting tasks or
* kernel threads (both mm NULL), since they never
* leave kernel.
*/
if (tsk->mm && printk_ratelimit())
printk(KERN_INFO "process %d (%s) no "
"longer affine to cpu%d\n",
tsk->pid, tsk->comm, dead_cpu);
}
__migrate_task(tsk, dead_cpu, dest_cpu);
}
/* Run through task list and migrate tasks from the dead cpu. */
static void migrate_live_tasks(int src_cpu)
{
struct task_struct *tsk, *t;
write_lock_irq(&tasklist_lock);
do_each_thread(t, tsk) {
if (tsk == current)
continue;
if (task_cpu(tsk) == src_cpu)
move_task_off_dead_cpu(src_cpu, tsk);
} while_each_thread(t, tsk);
write_unlock_irq(&tasklist_lock);
}
/* Schedules idle task to be the next runnable task on current CPU.
* It does so by boosting its priority to highest possible and adding it to
* the _front_ of runqueue. Used by CPU offline code.
*/
void sched_idle_next(void)
{
int cpu = smp_processor_id();
runqueue_t *rq = this_rq();
struct task_struct *p = rq->idle;
unsigned long flags;
/* cpu has to be offline */
BUG_ON(cpu_online(cpu));
/* Strictly not necessary since rest of the CPUs are stopped by now
* and interrupts disabled on current cpu.
*/
spin_lock_irqsave(&rq->lock, flags);
__setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
/* Add idle task to _front_ of it's priority queue */
__activate_idle_task(p, rq);
spin_unlock_irqrestore(&rq->lock, flags);
}
static void migrate_dead(unsigned int dead_cpu, task_t *tsk)
{
struct runqueue *rq = cpu_rq(dead_cpu);
/* Must be exiting, otherwise would be on tasklist. */
BUG_ON(tsk->state != TASK_ZOMBIE && tsk->state != TASK_DEAD);
/* Cannot have done final schedule yet: would have vanished. */
BUG_ON(tsk->flags & PF_DEAD);
get_task_struct(tsk);
/*
* Drop lock around migration; if someone else moves it,
* that's OK. No task can be added to this CPU, so iteration is
* fine.
*/
spin_unlock_irq(&rq->lock);
move_task_off_dead_cpu(dead_cpu, tsk);
spin_lock_irq(&rq->lock);
put_task_struct(tsk);
}
/* release_task() removes task from tasklist, so we won't find dead tasks. */
static void migrate_dead_tasks(unsigned int dead_cpu)
{
unsigned arr, i;
struct runqueue *rq = cpu_rq(dead_cpu);
for (arr = 0; arr < 2; arr++) {
for (i = 0; i < MAX_PRIO; i++) {
struct list_head *list = &rq->arrays[arr].queue[i];
while (!list_empty(list))
migrate_dead(dead_cpu,
list_entry(list->next, task_t,
run_list));
}
}
}
#endif /* CONFIG_HOTPLUG_CPU */
/*
* migration_call - callback that gets triggered when a CPU is added.
* Here we can start up the necessary migration thread for the new CPU.
*/
static int migration_call(struct notifier_block *nfb, unsigned long action,
void *hcpu)
{
int cpu = (long)hcpu;
struct task_struct *p;
struct runqueue *rq;
unsigned long flags;
switch (action) {
case CPU_UP_PREPARE:
p = kthread_create(migration_thread, hcpu, "migration/%d",cpu);
if (IS_ERR(p))
return NOTIFY_BAD;
p->flags |= PF_NOFREEZE;
kthread_bind(p, cpu);
/* Must be high prio: stop_machine expects to yield to it. */
rq = task_rq_lock(p, &flags);
__setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
task_rq_unlock(rq, &flags);
cpu_rq(cpu)->migration_thread = p;
break;
case CPU_ONLINE:
/* Strictly unneccessary, as first user will wake it. */
wake_up_process(cpu_rq(cpu)->migration_thread);
break;
#ifdef CONFIG_HOTPLUG_CPU
case CPU_UP_CANCELED:
/* Unbind it from offline cpu so it can run. Fall thru. */
kthread_bind(cpu_rq(cpu)->migration_thread,smp_processor_id());
kthread_stop(cpu_rq(cpu)->migration_thread);
cpu_rq(cpu)->migration_thread = NULL;
break;
case CPU_DEAD:
migrate_live_tasks(cpu);
rq = cpu_rq(cpu);
kthread_stop(rq->migration_thread);
rq->migration_thread = NULL;
/* Idle task back to normal (off runqueue, low prio) */
rq = task_rq_lock(rq->idle, &flags);
deactivate_task(rq->idle, rq);
rq->idle->static_prio = MAX_PRIO;
__setscheduler(rq->idle, SCHED_NORMAL, 0);
migrate_dead_tasks(cpu);
task_rq_unlock(rq, &flags);
BUG_ON(rq->nr_running != 0);
/* No need to migrate the tasks: it was best-effort if
* they didn't do lock_cpu_hotplug(). Just wake up
* the requestors. */
spin_lock_irq(&rq->lock);
while (!list_empty(&rq->migration_queue)) {
migration_req_t *req;
req = list_entry(rq->migration_queue.next,
migration_req_t, list);
BUG_ON(req->type != REQ_MOVE_TASK);
list_del_init(&req->list);
complete(&req->done);
}
spin_unlock_irq(&rq->lock);
break;
#endif
}
return NOTIFY_OK;
}
/* Register at highest priority so that task migration (migrate_all_tasks)
* happens before everything else.
*/
static struct notifier_block __devinitdata migration_notifier = {
.notifier_call = migration_call,
.priority = 10
};
int __init migration_init(void)
{
void *cpu = (void *)(long)smp_processor_id();
/* Start one for boot CPU. */
migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
migration_call(&migration_notifier, CPU_ONLINE, cpu);
register_cpu_notifier(&migration_notifier);
return 0;
}
#endif
/*
* The 'big kernel lock'
*
* This spinlock is taken and released recursively by lock_kernel()
* and unlock_kernel(). It is transparently dropped and reaquired
* over schedule(). It is used to protect legacy code that hasn't
* been migrated to a proper locking design yet.
*
* Don't use in new code.
*
* Note: spinlock debugging needs this even on !CONFIG_SMP.
*/
spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
EXPORT_SYMBOL(kernel_flag);
#ifdef CONFIG_SMP
/* Attach the domain 'sd' to 'cpu' as its base domain */
static void cpu_attach_domain(struct sched_domain *sd, int cpu)
{
migration_req_t req;
unsigned long flags;
runqueue_t *rq = cpu_rq(cpu);
int local = 1;
lock_cpu_hotplug();
spin_lock_irqsave(&rq->lock, flags);
if (cpu == smp_processor_id() || !cpu_online(cpu)) {
rq->sd = sd;
} else {
init_completion(&req.done);
req.type = REQ_SET_DOMAIN;
req.sd = sd;
list_add(&req.list, &rq->migration_queue);
local = 0;
}
spin_unlock_irqrestore(&rq->lock, flags);
if (!local) {
wake_up_process(rq->migration_thread);
wait_for_completion(&req.done);
}
unlock_cpu_hotplug();
}
/*
* To enable disjoint top-level NUMA domains, define SD_NODES_PER_DOMAIN
* in arch code. That defines the number of nearby nodes in a node's top
* level scheduling domain.
*/
#if defined(CONFIG_NUMA) && defined(SD_NODES_PER_DOMAIN)
/**
* find_next_best_node - find the next node to include in a sched_domain
* @node: node whose sched_domain we're building
* @used_nodes: nodes already in the sched_domain
*
* Find the next node to include in a given scheduling domain. Simply
* finds the closest node not already in the @used_nodes map.
*
* Should use nodemask_t.
*/
static int __init find_next_best_node(int node, unsigned long *used_nodes)
{
int i, n, val, min_val, best_node = 0;
min_val = INT_MAX;
for (i = 0; i < numnodes; i++) {
/* Start at @node */
n = (node + i) % numnodes;
/* Skip already used nodes */
if (test_bit(n, used_nodes))
continue;
/* Simple min distance search */
val = node_distance(node, i);
if (val < min_val) {
min_val = val;
best_node = n;
}
}
set_bit(best_node, used_nodes);
return best_node;
}
/**
* sched_domain_node_span - get a cpumask for a node's sched_domain
* @node: node whose cpumask we're constructing
* @size: number of nodes to include in this span
*
* Given a node, construct a good cpumask for its sched_domain to span. It
* should be one that prevents unnecessary balancing, but also spreads tasks
* out optimally.
*/
cpumask_t __init sched_domain_node_span(int node)
{
int i;
cpumask_t span;
DECLARE_BITMAP(used_nodes, MAX_NUMNODES);
cpus_clear(span);
bitmap_zero(used_nodes, MAX_NUMNODES);
for (i = 0; i < SD_NODES_PER_DOMAIN; i++) {
int next_node = find_next_best_node(node, used_nodes);
cpumask_t nodemask;
nodemask = node_to_cpumask(next_node);
cpus_or(span, span, nodemask);
}
return span;
}
#else /* CONFIG_NUMA && SD_NODES_PER_DOMAIN */
cpumask_t __init sched_domain_node_span(int node)
{
return cpu_possible_map;
}
#endif /* CONFIG_NUMA && SD_NODES_PER_DOMAIN */
#ifdef CONFIG_SCHED_SMT
static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
static struct sched_group sched_group_cpus[NR_CPUS];
__init static int cpu_to_cpu_group(int cpu)
{
return cpu;
}
#endif
static DEFINE_PER_CPU(struct sched_domain, phys_domains);
static struct sched_group sched_group_phys[NR_CPUS];
__init static int cpu_to_phys_group(int cpu)
{
#ifdef CONFIG_SCHED_SMT
return first_cpu(cpu_sibling_map[cpu]);
#else
return cpu;
#endif
}
#ifdef CONFIG_NUMA
static DEFINE_PER_CPU(struct sched_domain, node_domains);
static struct sched_group sched_group_nodes[MAX_NUMNODES];
__init static int cpu_to_node_group(int cpu)
{
return cpu_to_node(cpu);
}
#endif
/* Groups for isolated scheduling domains */
static struct sched_group sched_group_isolated[NR_CPUS];
/* cpus with isolated domains */
cpumask_t __initdata cpu_isolated_map = CPU_MASK_NONE;
__init static int cpu_to_isolated_group(int cpu)
{
return cpu;
}
/* Setup the mask of cpus configured for isolated domains */
static int __init isolated_cpu_setup(char *str)
{
int ints[NR_CPUS], i;
str = get_options(str, ARRAY_SIZE(ints), ints);
cpus_clear(cpu_isolated_map);
for (i = 1; i <= ints[0]; i++)
cpu_set(ints[i], cpu_isolated_map);
return 1;
}
__setup ("isolcpus=", isolated_cpu_setup);
/*
* init_sched_build_groups takes an array of groups, the cpumask we wish
* to span, and a pointer to a function which identifies what group a CPU
* belongs to. The return value of group_fn must be a valid index into the
* groups[] array, and must be >= 0 and < NR_CPUS (due to the fact that we
* keep track of groups covered with a cpumask_t).
*
* init_sched_build_groups will build a circular linked list of the groups
* covered by the given span, and will set each group's ->cpumask correctly,
* and ->cpu_power to 0.
*/
__init static void init_sched_build_groups(struct sched_group groups[],
cpumask_t span, int (*group_fn)(int cpu))
{
struct sched_group *first = NULL, *last = NULL;
cpumask_t covered = CPU_MASK_NONE;
int i;
for_each_cpu_mask(i, span) {
int group = group_fn(i);
struct sched_group *sg = &groups[group];
int j;
if (cpu_isset(i, covered))
continue;
sg->cpumask = CPU_MASK_NONE;
sg->cpu_power = 0;
for_each_cpu_mask(j, span) {
if (group_fn(j) != group)
continue;
cpu_set(j, covered);
cpu_set(j, sg->cpumask);
}
if (!first)
first = sg;
if (last)
last->next = sg;
last = sg;
}
last->next = first;
}
__init static void arch_init_sched_domains(void)
{
int i;
cpumask_t cpu_default_map;
/*
* Setup mask for cpus without special case scheduling requirements.
* For now this just excludes isolated cpus, but could be used to
* exclude other special cases in the future.
*/
cpus_complement(cpu_default_map, cpu_isolated_map);
cpus_and(cpu_default_map, cpu_default_map, cpu_possible_map);
/* Set up domains */
for_each_cpu(i) {
int group;
struct sched_domain *sd = NULL, *p;
cpumask_t nodemask = node_to_cpumask(cpu_to_node(i));
cpus_and(nodemask, nodemask, cpu_default_map);
/*
* Set up isolated domains.
* Unlike those of other cpus, the domains and groups are
* single level, and span a single cpu.
*/
if (cpu_isset(i, cpu_isolated_map)) {
#ifdef CONFIG_SCHED_SMT
sd = &per_cpu(cpu_domains, i);
#else
sd = &per_cpu(phys_domains, i);
#endif
group = cpu_to_isolated_group(i);
*sd = SD_CPU_INIT;
cpu_set(i, sd->span);
sd->balance_interval = INT_MAX; /* Don't balance */
sd->flags = 0; /* Avoid WAKE_ */
sd->groups = &sched_group_isolated[group];
printk(KERN_INFO "Setting up cpu %d isolated.\n", i);
/* Single level, so continue with next cpu */
continue;
}
#ifdef CONFIG_NUMA
sd = &per_cpu(node_domains, i);
group = cpu_to_node_group(i);
*sd = SD_NODE_INIT;
/* FIXME: should be multilevel, in arch code */
sd->span = sched_domain_node_span(i);
cpus_and(sd->span, sd->span, cpu_default_map);
sd->groups = &sched_group_nodes[group];
#endif
p = sd;
sd = &per_cpu(phys_domains, i);
group = cpu_to_phys_group(i);
*sd = SD_CPU_INIT;
#ifdef CONFIG_NUMA
sd->span = nodemask;
#else
sd->span = cpu_possible_map;
#endif
sd->parent = p;
sd->groups = &sched_group_phys[group];
#ifdef CONFIG_SCHED_SMT
p = sd;
sd = &per_cpu(cpu_domains, i);
group = cpu_to_cpu_group(i);
*sd = SD_SIBLING_INIT;
sd->span = cpu_sibling_map[i];
cpus_and(sd->span, sd->span, cpu_default_map);
sd->parent = p;
sd->groups = &sched_group_cpus[group];
#endif
}
#ifdef CONFIG_SCHED_SMT
/* Set up CPU (sibling) groups */
for_each_cpu(i) {
cpumask_t this_sibling_map = cpu_sibling_map[i];
cpus_and(this_sibling_map, this_sibling_map, cpu_default_map);
if (i != first_cpu(this_sibling_map))
continue;
init_sched_build_groups(sched_group_cpus, this_sibling_map,
&cpu_to_cpu_group);
}
#endif
/* Set up isolated groups */
for_each_cpu_mask(i, cpu_isolated_map) {
cpumask_t mask;
cpus_clear(mask);
cpu_set(i, mask);
init_sched_build_groups(sched_group_isolated, mask,
&cpu_to_isolated_group);
}
#ifdef CONFIG_NUMA
/* Set up physical groups */
for (i = 0; i < MAX_NUMNODES; i++) {
cpumask_t nodemask = node_to_cpumask(i);
cpus_and(nodemask, nodemask, cpu_default_map);
if (cpus_empty(nodemask))
continue;
init_sched_build_groups(sched_group_phys, nodemask,
&cpu_to_phys_group);
}
#else
init_sched_build_groups(sched_group_phys, cpu_possible_map,
&cpu_to_phys_group);
#endif
#ifdef CONFIG_NUMA
/* Set up node groups */
init_sched_build_groups(sched_group_nodes, cpu_default_map,
&cpu_to_node_group);
#endif
/* Calculate CPU power for physical packages and nodes */
for_each_cpu_mask(i, cpu_default_map) {
int power;
struct sched_domain *sd;
#ifdef CONFIG_SCHED_SMT
sd = &per_cpu(cpu_domains, i);
power = SCHED_LOAD_SCALE;
sd->groups->cpu_power = power;
#endif
sd = &per_cpu(phys_domains, i);
power = SCHED_LOAD_SCALE + SCHED_LOAD_SCALE *
(cpus_weight(sd->groups->cpumask)-1) / 10;
sd->groups->cpu_power = power;
#ifdef CONFIG_NUMA
if (i == first_cpu(sd->groups->cpumask)) {
/* Only add "power" once for each physical package. */
sd = &per_cpu(node_domains, i);
sd->groups->cpu_power += power;
}
#endif
}
/* Attach the domains */
for_each_cpu(i) {
struct sched_domain *sd;
#ifdef CONFIG_SCHED_SMT
sd = &per_cpu(cpu_domains, i);
#else
sd = &per_cpu(phys_domains, i);
#endif
cpu_attach_domain(sd, i);
}
}
#undef SCHED_DOMAIN_DEBUG
#ifdef SCHED_DOMAIN_DEBUG
void sched_domain_debug(void)
{
int i;
for_each_cpu(i) {
runqueue_t *rq = cpu_rq(i);
struct sched_domain *sd;
int level = 0;
sd = rq->sd;
printk(KERN_DEBUG "CPU%d: %s\n",
i, (cpu_online(i) ? " online" : "offline"));
do {
int j;
char str[NR_CPUS];
struct sched_group *group = sd->groups;
cpumask_t groupmask;
cpumask_scnprintf(str, NR_CPUS, sd->span);
cpus_clear(groupmask);
printk(KERN_DEBUG);
for (j = 0; j < level + 1; j++)
printk(" ");
printk("domain %d: span %s\n", level, str);
if (!cpu_isset(i, sd->span))
printk(KERN_DEBUG "ERROR domain->span does not contain CPU%d\n", i);
if (!cpu_isset(i, group->cpumask))
printk(KERN_DEBUG "ERROR domain->groups does not contain CPU%d\n", i);
if (!group->cpu_power)
printk(KERN_DEBUG "ERROR domain->cpu_power not set\n");
printk(KERN_DEBUG);
for (j = 0; j < level + 2; j++)
printk(" ");
printk("groups:");
do {
if (!group) {
printk(" ERROR: NULL");
break;
}
if (!cpus_weight(group->cpumask))
printk(" ERROR empty group:");
if (cpus_intersects(groupmask, group->cpumask))
printk(" ERROR repeated CPUs:");
cpus_or(groupmask, groupmask, group->cpumask);
cpumask_scnprintf(str, NR_CPUS, group->cpumask);
printk(" %s", str);
group = group->next;
} while (group != sd->groups);
printk("\n");
if (!cpus_equal(sd->span, groupmask))
printk(KERN_DEBUG "ERROR groups don't span domain->span\n");
level++;
sd = sd->parent;
if (sd) {
if (!cpus_subset(groupmask, sd->span))
printk(KERN_DEBUG "ERROR parent span is not a superset of domain->span\n");
}
} while (sd);
}
}
#else
#define sched_domain_debug() {}
#endif
void __init sched_init_smp(void)
{
arch_init_sched_domains();
sched_domain_debug();
}
#else
void __init sched_init_smp(void)
{
}
#endif /* CONFIG_SMP */
int in_sched_functions(unsigned long addr)
{
/* Linker adds these: start and end of __sched functions */
extern char __sched_text_start[], __sched_text_end[];
return in_lock_functions(addr) ||
(addr >= (unsigned long)__sched_text_start
&& addr < (unsigned long)__sched_text_end);
}
void __init sched_init(void)
{
runqueue_t *rq;
int i, j, k;
#ifdef CONFIG_SMP
/* Set up an initial dummy domain for early boot */
static struct sched_domain sched_domain_init;
static struct sched_group sched_group_init;
memset(&sched_domain_init, 0, sizeof(struct sched_domain));
sched_domain_init.span = CPU_MASK_ALL;
sched_domain_init.groups = &sched_group_init;
sched_domain_init.last_balance = jiffies;
sched_domain_init.balance_interval = INT_MAX; /* Don't balance */
sched_domain_init.busy_factor = 1;
memset(&sched_group_init, 0, sizeof(struct sched_group));
sched_group_init.cpumask = CPU_MASK_ALL;
sched_group_init.next = &sched_group_init;
sched_group_init.cpu_power = SCHED_LOAD_SCALE;
#endif
for (i = 0; i < NR_CPUS; i++) {
prio_array_t *array;
rq = cpu_rq(i);
spin_lock_init(&rq->lock);
rq->active = rq->arrays;
rq->expired = rq->arrays + 1;
rq->best_expired_prio = MAX_PRIO;
#ifdef CONFIG_SMP
rq->sd = &sched_domain_init;
rq->cpu_load = 0;
rq->active_balance = 0;
rq->push_cpu = 0;
rq->migration_thread = NULL;
INIT_LIST_HEAD(&rq->migration_queue);
#endif
atomic_set(&rq->nr_iowait, 0);
for (j = 0; j < 2; j++) {
array = rq->arrays + j;
for (k = 0; k < MAX_PRIO; k++) {
INIT_LIST_HEAD(array->queue + k);
__clear_bit(k, array->bitmap);
}
// delimiter for bitsearch
__set_bit(MAX_PRIO, array->bitmap);
}
}
/*
* The boot idle thread does lazy MMU switching as well:
*/
atomic_inc(&init_mm.mm_count);
enter_lazy_tlb(&init_mm, current);
/*
* Make us the idle thread. Technically, schedule() should not be
* called from this thread, however somewhere below it might be,
* but because we are the idle thread, we just pick up running again
* when this runqueue becomes "idle".
*/
init_idle(current, smp_processor_id());
}
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
void __might_sleep(char *file, int line)
{
#if defined(in_atomic)
static unsigned long prev_jiffy; /* ratelimiting */
if ((in_atomic() || irqs_disabled()) &&
system_state == SYSTEM_RUNNING) {
if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
return;
prev_jiffy = jiffies;
printk(KERN_ERR "Debug: sleeping function called from invalid"
" context at %s:%d\n", file, line);
printk("in_atomic():%d, irqs_disabled():%d\n",
in_atomic(), irqs_disabled());
dump_stack();
}
#endif
}
EXPORT_SYMBOL(__might_sleep);
#endif
| 
LINUX 
Kernels
