/* * kernel/sched.c * * Kernel scheduler and related syscalls * * Copyright (C) 1991-2002 Linus Torvalds * * 1996-12-23 Modified by Dave Grothe to fix bugs in semaphores and * make semaphores SMP safe * 1998-11-19 Implemented schedule_timeout() and related stuff * by Andrea Arcangeli * 2002-01-04 New ultra-scalable O(1) scheduler by Ingo Molnar: * hybrid priority-list and round-robin design with * an array-switch method of distributing timeslices * and per-CPU runqueues. Cleanups and useful suggestions * by Davide Libenzi, preemptible kernel bits by Robert Love. * 2003-09-03 Interactivity tuning by Con Kolivas. * 2004-04-02 Scheduler domains code by Nick Piggin */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Convert user-nice values [ -20 ... 0 ... 19 ] * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ], * and back. */ #define NICE_TO_PRIO(nice) (MAX_RT_PRIO + (nice) + 20) #define PRIO_TO_NICE(prio) ((prio) - MAX_RT_PRIO - 20) #define TASK_NICE(p) PRIO_TO_NICE((p)->static_prio) /* * 'User priority' is the nice value converted to something we * can work with better when scaling various scheduler parameters, * it's a [ 0 ... 39 ] range. */ #define USER_PRIO(p) ((p)-MAX_RT_PRIO) #define TASK_USER_PRIO(p) USER_PRIO((p)->static_prio) #define MAX_USER_PRIO (USER_PRIO(MAX_PRIO)) /* * Some helpers for converting nanosecond timing to jiffy resolution */ #define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ)) #define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ)) /* * These are the 'tuning knobs' of the scheduler: * * Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger), * default timeslice is 100 msecs, maximum timeslice is 800 msecs. * Timeslices get refilled after they expire. */ #define MIN_TIMESLICE max(5 * HZ / 1000, 1) #define DEF_TIMESLICE (100 * HZ / 1000) #define ON_RUNQUEUE_WEIGHT 30 #define CHILD_PENALTY 95 #define PARENT_PENALTY 100 #define EXIT_WEIGHT 3 #define PRIO_BONUS_RATIO 25 #define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100) #define INTERACTIVE_DELTA 2 #define MAX_SLEEP_AVG (DEF_TIMESLICE * MAX_BONUS) #define STARVATION_LIMIT (MAX_SLEEP_AVG) #define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG)) /* * If a task is 'interactive' then we reinsert it in the active * array after it has expired its current timeslice. (it will not * continue to run immediately, it will still roundrobin with * other interactive tasks.) * * This part scales the interactivity limit depending on niceness. * * We scale it linearly, offset by the INTERACTIVE_DELTA delta. * Here are a few examples of different nice levels: * * TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0] * TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0] * TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0] * TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0] * TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0] * * (the X axis represents the possible -5 ... 0 ... +5 dynamic * priority range a task can explore, a value of '1' means the * task is rated interactive.) * * Ie. nice +19 tasks can never get 'interactive' enough to be * reinserted into the active array. And only heavily CPU-hog nice -20 * tasks will be expired. Default nice 0 tasks are somewhere between, * it takes some effort for them to get interactive, but it's not * too hard. */ #define CURRENT_BONUS(p) \ (NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \ MAX_SLEEP_AVG) #define GRANULARITY (10 * HZ / 1000 ? : 1) #ifdef CONFIG_SMP #define TIMESLICE_GRANULARITY(p) (GRANULARITY * \ (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \ num_online_cpus()) #else #define TIMESLICE_GRANULARITY(p) (GRANULARITY * \ (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1))) #endif #define SCALE(v1,v1_max,v2_max) \ (v1) * (v2_max) / (v1_max) #define DELTA(p) \ (SCALE(TASK_NICE(p) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \ INTERACTIVE_DELTA) #define TASK_INTERACTIVE(p) \ ((p)->prio <= (p)->static_prio - DELTA(p)) #define INTERACTIVE_SLEEP(p) \ (JIFFIES_TO_NS(MAX_SLEEP_AVG * \ (MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1)) #define TASK_PREEMPTS_CURR(p, rq) \ ((p)->prio < (rq)->curr->prio) /* * task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ] * to time slice values: [800ms ... 100ms ... 5ms] * * The higher a thread's priority, the bigger timeslices * it gets during one round of execution. But even the lowest * priority thread gets MIN_TIMESLICE worth of execution time. */ #define SCALE_PRIO(x, prio) \ max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO/2), MIN_TIMESLICE) static unsigned int task_timeslice(task_t *p) { if (p->static_prio < NICE_TO_PRIO(0)) return SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio); else return SCALE_PRIO(DEF_TIMESLICE, p->static_prio); } #define task_hot(p, now, sd) ((long long) ((now) - (p)->last_ran) \ < (long long) (sd)->cache_hot_time) /* * These are the runqueue data structures: */ #define BITMAP_SIZE ((((MAX_PRIO+1+7)/8)+sizeof(long)-1)/sizeof(long)) typedef struct runqueue runqueue_t; struct prio_array { unsigned int nr_active; unsigned long bitmap[BITMAP_SIZE]; struct list_head queue[MAX_PRIO]; }; /* * This is the main, per-CPU runqueue data structure. * * Locking rule: those places that want to lock multiple runqueues * (such as the load balancing or the thread migration code), lock * acquire operations must be ordered by ascending &runqueue. */ struct runqueue { spinlock_t lock; /* * nr_running and cpu_load should be in the same cacheline because * remote CPUs use both these fields when doing load calculation. */ unsigned long nr_running; #ifdef CONFIG_SMP unsigned long cpu_load[3]; #endif unsigned long long nr_switches; /* * This is part of a global counter where only the total sum * over all CPUs matters. A task can increase this counter on * one CPU and if it got migrated afterwards it may decrease * it on another CPU. Always updated under the runqueue lock: */ unsigned long nr_uninterruptible; unsigned long expired_timestamp; unsigned long long timestamp_last_tick; task_t *curr, *idle; struct mm_struct *prev_mm; prio_array_t *active, *expired, arrays[2]; int best_expired_prio; atomic_t nr_iowait; #ifdef CONFIG_SMP struct sched_domain *sd; /* For active balancing */ int active_balance; int push_cpu; task_t *migration_thread; struct list_head migration_queue; int cpu; #endif #ifdef CONFIG_SCHEDSTATS /* latency stats */ struct sched_info rq_sched_info; /* sys_sched_yield() stats */ unsigned long yld_exp_empty; unsigned long yld_act_empty; unsigned long yld_both_empty; unsigned long yld_cnt; /* schedule() stats */ unsigned long sched_switch; unsigned long sched_cnt; unsigned long sched_goidle; /* try_to_wake_up() stats */ unsigned long ttwu_cnt; unsigned long ttwu_local; #endif }; static DEFINE_PER_CPU(struct runqueue, runqueues); /* * The domain tree (rq->sd) is protected by RCU's quiescent state transition. * See detach_destroy_domains: synchronize_sched for details. * * The domain tree of any CPU may only be accessed from within * preempt-disabled sections. */ #define for_each_domain(cpu, domain) \ for (domain = rcu_dereference(cpu_rq(cpu)->sd); domain; domain = domain->parent) #define cpu_rq(cpu) (&per_cpu(runqueues, (cpu))) #define this_rq() (&__get_cpu_var(runqueues)) #define task_rq(p) cpu_rq(task_cpu(p)) #define cpu_curr(cpu) (cpu_rq(cpu)->curr) #ifndef prepare_arch_switch # define prepare_arch_switch(next) do { } while (0) #endif #ifndef finish_arch_switch # define finish_arch_switch(prev) do { } while (0) #endif #ifndef __ARCH_WANT_UNLOCKED_CTXSW static inline int task_running(runqueue_t *rq, task_t *p) { return rq->curr == p; } static inline void prepare_lock_switch(runqueue_t *rq, task_t *next) { } static inline void finish_lock_switch(runqueue_t *rq, task_t *prev) { #ifdef CONFIG_DEBUG_SPINLOCK /* this is a valid case when another task releases the spinlock */ rq->lock.owner = current; #endif spin_unlock_irq(&rq->lock); } #else /* __ARCH_WANT_UNLOCKED_CTXSW */ static inline int task_running(runqueue_t *rq, task_t *p) { #ifdef CONFIG_SMP return p->oncpu; #else return rq->curr == p; #endif } static inline void prepare_lock_switch(runqueue_t *rq, task_t *next) { #ifdef CONFIG_SMP /* * We can optimise this out completely for !SMP, because the * SMP rebalancing from interrupt is the only thing that cares * here. */ next->oncpu = 1; #endif #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW spin_unlock_irq(&rq->lock); #else spin_unlock(&rq->lock); #endif } static inline void finish_lock_switch(runqueue_t *rq, task_t *prev) { #ifdef CONFIG_SMP /* * After ->oncpu is cleared, the task can be moved to a different CPU. * We must ensure this doesn't happen until the switch is completely * finished. */ smp_wmb(); prev->oncpu = 0; #endif #ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW local_irq_enable(); #endif } #endif /* __ARCH_WANT_UNLOCKED_CTXSW */ /* * task_rq_lock - lock the runqueue a given task resides on and disable * interrupts. Note the ordering: we can safely lookup the task_rq without * explicitly disabling preemption. */ static inline runqueue_t *task_rq_lock(task_t *p, unsigned long *flags) __acquires(rq->lock) { struct runqueue *rq; repeat_lock_task: local_irq_save(*flags); rq = task_rq(p); spin_lock(&rq->lock); if (unlikely(rq != task_rq(p))) { spin_unlock_irqrestore(&rq->lock, *flags); goto repeat_lock_task; } return rq; } static inline void task_rq_unlock(runqueue_t *rq, unsigned long *flags) __releases(rq->lock) { spin_unlock_irqrestore(&rq->lock, *flags); } #ifdef CONFIG_SCHEDSTATS /* * bump this up when changing the output format or the meaning of an existing * format, so that tools can adapt (or abort) */ #define SCHEDSTAT_VERSION 12 static int show_schedstat(struct seq_file *seq, void *v) { int cpu; seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION); seq_printf(seq, "timestamp %lu\n", jiffies); for_each_online_cpu(cpu) { runqueue_t *rq = cpu_rq(cpu); #ifdef CONFIG_SMP struct sched_domain *sd; int dcnt = 0; #endif /* runqueue-specific stats */ seq_printf(seq, "cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu", cpu, rq->yld_both_empty, rq->yld_act_empty, rq->yld_exp_empty, rq->yld_cnt, rq->sched_switch, rq->sched_cnt, rq->sched_goidle, rq->ttwu_cnt, rq->ttwu_local, rq->rq_sched_info.cpu_time, rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt); seq_printf(seq, "\n"); #ifdef CONFIG_SMP /* domain-specific stats */ preempt_disable(); for_each_domain(cpu, sd) { enum idle_type itype; char mask_str[NR_CPUS]; cpumask_scnprintf(mask_str, NR_CPUS, sd->span); seq_printf(seq, "domain%d %s", dcnt++, mask_str); for (itype = SCHED_IDLE; itype < MAX_IDLE_TYPES; itype++) { seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu", sd->lb_cnt[itype], sd->lb_balanced[itype], sd->lb_failed[itype], sd->lb_imbalance[itype], sd->lb_gained[itype], sd->lb_hot_gained[itype], sd->lb_nobusyq[itype], sd->lb_nobusyg[itype]); } seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n", sd->alb_cnt, sd->alb_failed, sd->alb_pushed, sd->sbe_cnt, sd->sbe_balanced, sd->sbe_pushed, sd->sbf_cnt, sd->sbf_balanced, sd->sbf_pushed, sd->ttwu_wake_remote, sd->ttwu_move_affine, sd->ttwu_move_balance); } preempt_enable(); #endif } return 0; } static int schedstat_open(struct inode *inode, struct file *file) { unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32); char *buf = kmalloc(size, GFP_KERNEL); struct seq_file *m; int res; if (!buf) return -ENOMEM; res = single_open(file, show_schedstat, NULL); if (!res) { m = file->private_data; m->buf = buf; m->size = size; } else kfree(buf); return res; } struct file_operations proc_schedstat_operations = { .open = schedstat_open, .read = seq_read, .llseek = seq_lseek, .release = single_release, }; # define schedstat_inc(rq, field) do { (rq)->field++; } while (0) # define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0) #else /* !CONFIG_SCHEDSTATS */ # define schedstat_inc(rq, field) do { } while (0) # define schedstat_add(rq, field, amt) do { } while (0) #endif /* * rq_lock - lock a given runqueue and disable interrupts. */ static inline runqueue_t *this_rq_lock(void) __acquires(rq->lock) { runqueue_t *rq; local_irq_disable(); rq = this_rq(); spin_lock(&rq->lock); return rq; } #ifdef CONFIG_SCHEDSTATS /* * Called when a process is dequeued from the active array and given * the cpu. We should note that with the exception of interactive * tasks, the expired queue will become the active queue after the active * queue is empty, without explicitly dequeuing and requeuing tasks in the * expired queue. (Interactive tasks may be requeued directly to the * active queue, thus delaying tasks in the expired queue from running; * see scheduler_tick()). * * This function is only called from sched_info_arrive(), rather than * dequeue_task(). Even though a task may be queued and dequeued multiple * times as it is shuffled about, we're really interested in knowing how * long it was from the *first* time it was queued to the time that it * finally hit a cpu. */ static inline void sched_info_dequeued(task_t *t) { t->sched_info.last_queued = 0; } /* * Called when a task finally hits the cpu. We can now calculate how * long it was waiting to run. We also note when it began so that we * can keep stats on how long its timeslice is. */ static void sched_info_arrive(task_t *t) { unsigned long now = jiffies, diff = 0; struct runqueue *rq = task_rq(t); if (t->sched_info.last_queued) diff = now - t->sched_info.last_queued; sched_info_dequeued(t); t->sched_info.run_delay += diff; t->sched_info.last_arrival = now; t->sched_info.pcnt++; if (!rq) return; rq->rq_sched_info.run_delay += diff; rq->rq_sched_info.pcnt++; } /* * Called when a process is queued into either the active or expired * array. The time is noted and later used to determine how long we * had to wait for us to reach the cpu. Since the expired queue will * become the active queue after active queue is empty, without dequeuing * and requeuing any tasks, we are interested in queuing to either. It * is unusual but not impossible for tasks to be dequeued and immediately * requeued in the same or another array: this can happen in sched_yield(), * set_user_nice(), and even load_balance() as it moves tasks from runqueue * to runqueue. * * This function is only called from enqueue_task(), but also only updates * the timestamp if it is already not set. It's assumed that * sched_info_dequeued() will clear that stamp when appropriate. */ static inline void sched_info_queued(task_t *t) { if (!t->sched_info.last_queued) t->sched_info.last_queued = jiffies; } /* * Called when a process ceases being the active-running process, either * voluntarily or involuntarily. Now we can calculate how long we ran. */ static inline void sched_info_depart(task_t *t) { struct runqueue *rq = task_rq(t); unsigned long diff = jiffies - t->sched_info.last_arrival; t->sched_info.cpu_time += diff; if (rq) rq->rq_sched_info.cpu_time += diff; } /* * Called when tasks are switched involuntarily due, typically, to expiring * their time slice. (This may also be called when switching to or from * the idle task.) We are only called when prev != next. */ static inline void sched_info_switch(task_t *prev, task_t *next) { struct runqueue *rq = task_rq(prev); /* * prev now departs the cpu. It's not interesting to record * stats about how efficient we were at scheduling the idle * process, however. */ if (prev != rq->idle) sched_info_depart(prev); if (next != rq->idle) sched_info_arrive(next); } #else #define sched_info_queued(t) do { } while (0) #define sched_info_switch(t, next) do { } while (0) #endif /* CONFIG_SCHEDSTATS */ /* * Adding/removing a task to/from a priority array: */ static void dequeue_task(struct task_struct *p, prio_array_t *array) { array->nr_active--; list_del(&p->run_list); if (list_empty(array->queue + p->prio)) __clear_bit(p->prio, array->bitmap); } static void enqueue_task(struct task_struct *p, prio_array_t *array) { sched_info_queued(p); list_add_tail(&p->run_list, array->queue + p->prio); __set_bit(p->prio, array->bitmap); array->nr_active++; p->array = array; } /* * Put task to the end of the run list without the overhead of dequeue * followed by enqueue. */ static void requeue_task(struct task_struct *p, prio_array_t *array) { list_move_tail(&p->run_list, array->queue + p->prio); } static inline void enqueue_task_head(struct task_struct *p, prio_array_t *array) { list_add(&p->run_list, array->queue + p->prio); __set_bit(p->prio, array->bitmap); array->nr_active++; p->array = array; } /* * effective_prio - return the priority that is based on the static * priority but is modified by bonuses/penalties. * * We scale the actual sleep average [0 .... MAX_SLEEP_AVG] * into the -5 ... 0 ... +5 bonus/penalty range. * * We use 25% of the full 0...39 priority range so that: * * 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs. * 2) nice -20 CPU hogs do not get preempted by nice 0 tasks. * * Both properties are important to certain workloads. */ static int effective_prio(task_t *p) { int bonus, prio; if (rt_task(p)) return p->prio; bonus = CURRENT_BONUS(p) - MAX_BONUS / 2; prio = p->static_prio - bonus; if (prio < MAX_RT_PRIO) prio = MAX_RT_PRIO; if (prio > MAX_PRIO-1) prio = MAX_PRIO-1; return prio; } /* * __activate_task - move a task to the runqueue. */ static void __activate_task(task_t *p, runqueue_t *rq) { prio_array_t *target = rq->active; if (batch_task(p)) target = rq->expired; enqueue_task(p, target); rq->nr_running++; } /* * __activate_idle_task - move idle task to the _front_ of runqueue. */ static inline void __activate_idle_task(task_t *p, runqueue_t *rq) { enqueue_task_head(p, rq->active); rq->nr_running++; } static int recalc_task_prio(task_t *p, unsigned long long now) { /* Caller must always ensure 'now >= p->timestamp' */ unsigned long long __sleep_time = now - p->timestamp; unsigned long sleep_time; if (batch_task(p)) sleep_time = 0; else { if (__sleep_time > NS_MAX_SLEEP_AVG) sleep_time = NS_MAX_SLEEP_AVG; else sleep_time = (unsigned long)__sleep_time; } if (likely(sleep_time > 0)) { /* * User tasks that sleep a long time are categorised as * idle. They will only have their sleep_avg increased to a * level that makes them just interactive priority to stay * active yet prevent them suddenly becoming cpu hogs and * starving other processes. */ if (p->mm && sleep_time > INTERACTIVE_SLEEP(p)) { unsigned long ceiling; ceiling = JIFFIES_TO_NS(MAX_SLEEP_AVG - DEF_TIMESLICE); if (p->sleep_avg < ceiling) p->sleep_avg = ceiling; } else { /* * Tasks waking from uninterruptible sleep are * limited in their sleep_avg rise as they * are likely to be waiting on I/O */ if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) { if (p->sleep_avg >= INTERACTIVE_SLEEP(p)) sleep_time = 0; else if (p->sleep_avg + sleep_time >= INTERACTIVE_SLEEP(p)) { p->sleep_avg = INTERACTIVE_SLEEP(p); sleep_time = 0; } } /* * This code gives a bonus to interactive tasks. * * The boost works by updating the 'average sleep time' * value here, based on ->timestamp. The more time a * task spends sleeping, the higher the average gets - * and the higher the priority boost gets as well. */ p->sleep_avg += sleep_time; if (p->sleep_avg > NS_MAX_SLEEP_AVG) p->sleep_avg = NS_MAX_SLEEP_AVG; } } return effective_prio(p); } /* * activate_task - move a task to the runqueue and do priority recalculation * * Update all the scheduling statistics stuff. (sleep average * calculation, priority modifiers, etc.) */ static void activate_task(task_t *p, runqueue_t *rq, int local) { unsigned long long now; now = sched_clock(); #ifdef CONFIG_SMP if (!local) { /* Compensate for drifting sched_clock */ runqueue_t *this_rq = this_rq(); now = (now - this_rq->timestamp_last_tick) + rq->timestamp_last_tick; } #endif if (!rt_task(p)) p->prio = recalc_task_prio(p, now); /* * This checks to make sure it's not an uninterruptible task * that is now waking up. */ if (p->sleep_type == SLEEP_NORMAL) { /* * Tasks which were woken up by interrupts (ie. hw events) * are most likely of interactive nature. So we give them * the credit of extending their sleep time to the period * of time they spend on the runqueue, waiting for execution * on a CPU, first time around: */ if (in_interrupt()) p->sleep_type = SLEEP_INTERRUPTED; else { /* * Normal first-time wakeups get a credit too for * on-runqueue time, but it will be weighted down: */ p->sleep_type = SLEEP_INTERACTIVE; } } p->timestamp = now; __activate_task(p, rq); } /* * deactivate_task - remove a task from the runqueue. */ static void deactivate_task(struct task_struct *p, runqueue_t *rq) { rq->nr_running--; dequeue_task(p, p->array); p->array = NULL; } /* * resched_task - mark a task 'to be rescheduled now'. * * On UP this means the setting of the need_resched flag, on SMP it * might also involve a cross-CPU call to trigger the scheduler on * the target CPU. */ #ifdef CONFIG_SMP static void resched_task(task_t *p) { int cpu; assert_spin_locked(&task_rq(p)->lock); if (unlikely(test_tsk_thread_flag(p, TIF_NEED_RESCHED))) return; set_tsk_thread_flag(p, TIF_NEED_RESCHED); cpu = task_cpu(p); if (cpu == smp_processor_id()) return; /* NEED_RESCHED must be visible before we test POLLING_NRFLAG */ smp_mb(); if (!test_tsk_thread_flag(p, TIF_POLLING_NRFLAG)) smp_send_reschedule(cpu); } #else static inline void resched_task(task_t *p) { assert_spin_locked(&task_rq(p)->lock); set_tsk_need_resched(p); } #endif /** * task_curr - is this task currently executing on a CPU? * @p: the task in question. */ inline int task_curr(const task_t *p) { return cpu_curr(task_cpu(p)) == p; } #ifdef CONFIG_SMP typedef struct { struct list_head list; task_t *task; int dest_cpu; struct completion done; } migration_req_t; /* * The task's runqueue lock must be held. * Returns true if you have to wait for migration thread. */ static int migrate_task(task_t *p, int dest_cpu, migration_req_t *req) { runqueue_t *rq = task_rq(p); /* * If the task is not on a runqueue (and not running), then * it is sufficient to simply update the task's cpu field. */ if (!p->array && !task_running(rq, p)) { set_task_cpu(p, dest_cpu); return 0; } init_completion(&req->done); req->task = p; req->dest_cpu = dest_cpu; list_add(&req->list, &rq->migration_queue); return 1; } /* * wait_task_inactive - wait for a thread to unschedule. * * The caller must ensure that the task *will* unschedule sometime soon, * else this function might spin for a *long* time. This function can't * be called with interrupts off, or it may introduce deadlock with * smp_call_function() if an IPI is sent by the same process we are * waiting to become inactive. */ void wait_task_inactive(task_t *p) { unsigned long flags; runqueue_t *rq; int preempted; repeat: rq = task_rq_lock(p, &flags); /* Must be off runqueue entirely, not preempted. */ if (unlikely(p->array || task_running(rq, p))) { /* If it's preempted, we yield. It could be a while. */ preempted = !task_running(rq, p); task_rq_unlock(rq, &flags); cpu_relax(); if (preempted) yield(); goto repeat; } task_rq_unlock(rq, &flags); } /*** * kick_process - kick a running thread to enter/exit the kernel * @p: the to-be-kicked thread * * Cause a process which is running on another CPU to enter * kernel-mode, without any delay. (to get signals handled.) * * NOTE: this function doesnt have to take the runqueue lock, * because all it wants to ensure is that the remote task enters * the kernel. If the IPI races and the task has been migrated * to another CPU then no harm is done and the purpose has been * achieved as well. */ void kick_process(task_t *p) { int cpu; preempt_disable(); cpu = task_cpu(p); if ((cpu != smp_processor_id()) && task_curr(p)) smp_send_reschedule(cpu); preempt_enable(); } /* * Return a low guess at the load of a migration-source cpu. * * We want to under-estimate the load of migration sources, to * balance conservatively. */ static inline unsigned long source_load(int cpu, int type) { runqueue_t *rq = cpu_rq(cpu); unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE; if (type == 0) return load_now; return min(rq->cpu_load[type-1], load_now); } /* * Return a high guess at the load of a migration-target cpu */ static inline unsigned long target_load(int cpu, int type) { runqueue_t *rq = cpu_rq(cpu); unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE; if (type == 0) return load_now; return max(rq->cpu_load[type-1], load_now); } /* * find_idlest_group finds and returns the least busy CPU group within the * domain. */ static struct sched_group * find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu) { struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups; unsigned long min_load = ULONG_MAX, this_load = 0; int load_idx = sd->forkexec_idx; int imbalance = 100 + (sd->imbalance_pct-100)/2; do { unsigned long load, avg_load; int local_group; int i; /* Skip over this group if it has no CPUs allowed */ if (!cpus_intersects(group->cpumask, p->cpus_allowed)) goto nextgroup; local_group = cpu_isset(this_cpu, group->cpumask); /* Tally up the load of all CPUs in the group */ avg_load = 0; for_each_cpu_mask(i, group->cpumask) { /* Bias balancing toward cpus of our domain */ if (local_group) load = source_load(i, load_idx); else load = target_load(i, load_idx); avg_load += load; } /* Adjust by relative CPU power of the group */ avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power; if (local_group) { this_load = avg_load; this = group; } else if (avg_load < min_load) { min_load = avg_load; idlest = group; } nextgroup: group = group->next; } while (group != sd->groups); if (!idlest || 100*this_load < imbalance*min_load) return NULL; return idlest; } /* * find_idlest_queue - find the idlest runqueue among the cpus in group. */ static int find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) { cpumask_t tmp; unsigned long load, min_load = ULONG_MAX; int idlest = -1; int i; /* Traverse only the allowed CPUs */ cpus_and(tmp, group->cpumask, p->cpus_allowed); for_each_cpu_mask(i, tmp) { load = source_load(i, 0); if (load < min_load || (load == min_load && i == this_cpu)) { min_load = load; idlest = i; } } return idlest; } /* * sched_balance_self: balance the current task (running on cpu) in domains * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and * SD_BALANCE_EXEC. * * Balance, ie. select the least loaded group. * * Returns the target CPU number, or the same CPU if no balancing is needed. * * preempt must be disabled. */ static int sched_balance_self(int cpu, int flag) { struct task_struct *t = current; struct sched_domain *tmp, *sd = NULL; for_each_domain(cpu, tmp) if (tmp->flags & flag) sd = tmp; while (sd) { cpumask_t span; struct sched_group *group; int new_cpu; int weight; span = sd->span; group = find_idlest_group(sd, t, cpu); if (!group) goto nextlevel; new_cpu = find_idlest_cpu(group, t, cpu); if (new_cpu == -1 || new_cpu == cpu) goto nextlevel; /* Now try balancing at a lower domain level */ cpu = new_cpu; nextlevel: sd = NULL; weight = cpus_weight(span); for_each_domain(cpu, tmp) { if (weight <= cpus_weight(tmp->span)) break; if (tmp->flags & flag) sd = tmp; } /* while loop will break here if sd == NULL */ } return cpu; } #endif /* CONFIG_SMP */ /* * wake_idle() will wake a task on an idle cpu if task->cpu is * not idle and an idle cpu is available. The span of cpus to * search starts with cpus closest then further out as needed, * so we always favor a closer, idle cpu. * * Returns the CPU we should wake onto. */ #if defined(ARCH_HAS_SCHED_WAKE_IDLE) static int wake_idle(int cpu, task_t *p) { cpumask_t tmp; struct sched_domain *sd; int i; if (idle_cpu(cpu)) return cpu; for_each_domain(cpu, sd) { if (sd->flags & SD_WAKE_IDLE) { cpus_and(tmp, sd->span, p->cpus_allowed); for_each_cpu_mask(i, tmp) { if (idle_cpu(i)) return i; } } else break; } return cpu; } #else static inline int wake_idle(int cpu, task_t *p) { return cpu; } #endif /*** * try_to_wake_up - wake up a thread * @p: the to-be-woken-up thread * @state: the mask of task states that can be woken * @sync: do a synchronous wakeup? * * Put it on the run-queue if it's not already there. The "current" * thread is always on the run-queue (except when the actual * re-schedule is in progress), and as such you're allowed to do * the simpler "current->state = TASK_RUNNING" to mark yourself * runnable without the overhead of this. * * returns failure only if the task is already active. */ static int try_to_wake_up(task_t *p, unsigned int state, int sync) { int cpu, this_cpu, success = 0; unsigned long flags; long old_state; runqueue_t *rq; #ifdef CONFIG_SMP unsigned long load, this_load; struct sched_domain *sd, *this_sd = NULL; int new_cpu; #endif rq = task_rq_lock(p, &flags); old_state = p->state; if (!(old_state & state)) goto out; if (p->array) goto out_running; cpu = task_cpu(p); this_cpu = smp_processor_id(); #ifdef CONFIG_SMP if (unlikely(task_running(rq, p))) goto out_activate; new_cpu = cpu; schedstat_inc(rq, ttwu_cnt); if (cpu == this_cpu) { schedstat_inc(rq, ttwu_local); goto out_set_cpu; } for_each_domain(this_cpu, sd) { if (cpu_isset(cpu, sd->span)) { schedstat_inc(sd, ttwu_wake_remote); this_sd = sd; break; } } if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed))) goto out_set_cpu; /* * Check for affine wakeup and passive balancing possibilities. */ if (this_sd) { int idx = this_sd->wake_idx; unsigned int imbalance; imbalance = 100 + (this_sd->imbalance_pct - 100) / 2; load = source_load(cpu, idx); this_load = target_load(this_cpu, idx); new_cpu = this_cpu; /* Wake to this CPU if we can */ if (this_sd->flags & SD_WAKE_AFFINE) { unsigned long tl = this_load; /* * If sync wakeup then subtract the (maximum possible) * effect of the currently running task from the load * of the current CPU: */ if (sync) tl -= SCHED_LOAD_SCALE; if ((tl <= load && tl + target_load(cpu, idx) <= SCHED_LOAD_SCALE) || 100*(tl + SCHED_LOAD_SCALE) <= imbalance*load) { /* * This domain has SD_WAKE_AFFINE and * p is cache cold in this domain, and * there is no bad imbalance. */ schedstat_inc(this_sd, ttwu_move_affine); goto out_set_cpu; } } /* * Start passive balancing when half the imbalance_pct * limit is reached. */ if (this_sd->flags & SD_WAKE_BALANCE) { if (imbalance*this_load <= 100*load) { schedstat_inc(this_sd, ttwu_move_balance); goto out_set_cpu; } } } new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */ out_set_cpu: new_cpu = wake_idle(new_cpu, p); if (new_cpu != cpu) { set_task_cpu(p, new_cpu); task_rq_unlock(rq, &flags); /* might preempt at this point */ rq = task_rq_lock(p, &flags); old_state = p->state; if (!(old_state & state)) goto out; if (p->array) goto out_running; this_cpu = smp_processor_id(); cpu = task_cpu(p); } out_activate: #endif /* CONFIG_SMP */ if (old_state == TASK_UNINTERRUPTIBLE) { rq->nr_uninterruptible--; /* * Tasks on involuntary sleep don't earn * sleep_avg beyond just interactive state. */ p->sleep_type = SLEEP_NONINTERACTIVE; } else /* * Tasks that have marked their sleep as noninteractive get * woken up with their sleep average not weighted in an * interactive way. */ if (old_state & TASK_NONINTERACTIVE) p->sleep_type = SLEEP_NONINTERACTIVE; activate_task(p, rq, cpu == this_cpu); /* * Sync wakeups (i.e. those types of wakeups where the waker * has indicated that it will leave the CPU in short order) * don't trigger a preemption, if the woken up task will run on * this cpu. (in this case the 'I will reschedule' promise of * the waker guarantees that the freshly woken up task is going * to be considered on this CPU.) */ if (!sync || cpu != this_cpu) { if (TASK_PREEMPTS_CURR(p, rq)) resched_task(rq->curr); } success = 1; out_running: p->state = TASK_RUNNING; out: task_rq_unlock(rq, &flags); return success; } int fastcall wake_up_process(task_t *p) { return try_to_wake_up(p, TASK_STOPPED | TASK_TRACED | TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, 0); } EXPORT_SYMBOL(wake_up_process); int fastcall wake_up_state(task_t *p, unsigned int state) { return try_to_wake_up(p, state, 0); } /* * Perform scheduler related setup for a newly forked process p. * p is forked by current. */ void fastcall sched_fork(task_t *p, int clone_flags) { int cpu = get_cpu(); #ifdef CONFIG_SMP cpu = sched_balance_self(cpu, SD_BALANCE_FORK); #endif set_task_cpu(p, cpu); /* * We mark the process as running here, but have not actually * inserted it onto the runqueue yet. This guarantees that * nobody will actually run it, and a signal or other external * event cannot wake it up and insert it on the runqueue either. */ p->state = TASK_RUNNING; INIT_LIST_HEAD(&p->run_list); p->array = NULL; #ifdef CONFIG_SCHEDSTATS memset(&p->sched_info, 0, sizeof(p->sched_info)); #endif #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW) p->oncpu = 0; #endif #ifdef CONFIG_PREEMPT /* Want to start with kernel preemption disabled. */ task_thread_info(p)->preempt_count = 1; #endif /* * Share the timeslice between parent and child, thus the * total amount of pending timeslices in the system doesn't change, * resulting in more scheduling fairness. */ local_irq_disable(); p->time_slice = (current->time_slice + 1) >> 1; /* * The remainder of the first timeslice might be recovered by * the parent if the child exits early enough. */ p->first_time_slice = 1; current->time_slice >>= 1; p->timestamp = sched_clock(); if (unlikely(!current->time_slice)) { /* * This case is rare, it happens when the parent has only * a single jiffy left from its timeslice. Taking the * runqueue lock is not a problem. */ current->time_slice = 1; scheduler_tick(); } local_irq_enable(); put_cpu(); } /* * wake_up_new_task - wake up a newly created task for the first time. * * This function will do some initial scheduler statistics housekeeping * that must be done for every newly created context, then puts the task * on the runqueue and wakes it. */ void fastcall wake_up_new_task(task_t *p, unsigned long clone_flags) { unsigned long flags; int this_cpu, cpu; runqueue_t *rq, *this_rq; rq = task_rq_lock(p, &flags); BUG_ON(p->state != TASK_RUNNING); this_cpu = smp_processor_id(); cpu = task_cpu(p); /* * We decrease the sleep average of forking parents * and children as well, to keep max-interactive tasks * from forking tasks that are max-interactive. The parent * (current) is done further down, under its lock. */ p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) * CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS); p->prio = effective_prio(p); if (likely(cpu == this_cpu)) { if (!(clone_flags & CLONE_VM)) { /* * The VM isn't cloned, so we're in a good position to * do child-runs-first in anticipation of an exec. This * usually avoids a lot of COW overhead. */ if (unlikely(!current->array)) __activate_task(p, rq); else { p->prio = current->prio; list_add_tail(&p->run_list, ¤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); /* * Parent and child are on different CPUs, now get the * parent runqueue to update the parent's ->sleep_avg: */ task_rq_unlock(rq, &flags); this_rq = task_rq_lock(current, &flags); } current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) * PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS); task_rq_unlock(this_rq, &flags); } /* * Potentially available exiting-child timeslices are * retrieved here - this way the parent does not get * penalized for creating too many threads. * * (this cannot be used to 'generate' timeslices * artificially, because any timeslice recovered here * was given away by the parent in the first place.) */ void fastcall sched_exit(task_t *p) { unsigned long flags; runqueue_t *rq; /* * If the child was a (relative-) CPU hog then decrease * the sleep_avg of the parent as well. */ rq = task_rq_lock(p->parent, &flags); if (p->first_time_slice && task_cpu(p) == task_cpu(p->parent)) { p->parent->time_slice += p->time_slice; if (unlikely(p->parent->time_slice > task_timeslice(p))) p->parent->time_slice = task_timeslice(p); } if (p->sleep_avg < p->parent->sleep_avg) p->parent->sleep_avg = p->parent->sleep_avg / (EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg / (EXIT_WEIGHT + 1); task_rq_unlock(rq, &flags); } /** * prepare_task_switch - prepare to switch tasks * @rq: the runqueue preparing to switch * @next: the task we are going to switch to. * * This is called with the rq lock held and interrupts off. It must * be paired with a subsequent finish_task_switch after the context * switch. * * prepare_task_switch sets up locking and calls architecture specific * hooks. */ static inline void prepare_task_switch(runqueue_t *rq, task_t *next) { prepare_lock_switch(rq, next); prepare_arch_switch(next); } /** * finish_task_switch - clean up after a task-switch * @rq: runqueue associated with task-switch * @prev: the thread we just switched away from. * * finish_task_switch must be called after the context switch, paired * with a prepare_task_switch call before the context switch. * finish_task_switch will reconcile locking set up by prepare_task_switch, * and do any other architecture-specific cleanup actions. * * Note that we may have delayed dropping an mm in context_switch(). If * so, we finish that here outside of the runqueue lock. (Doing it * with the lock held can cause deadlocks; see schedule() for * details.) */ static inline void finish_task_switch(runqueue_t *rq, task_t *prev) __releases(rq->lock) { struct mm_struct *mm = rq->prev_mm; unsigned long prev_task_flags; rq->prev_mm = NULL; /* * A task struct has one reference for the use as "current". * If a task dies, then it sets EXIT_ZOMBIE in tsk->exit_state and * calls schedule one last time. The schedule call will never return, * and the scheduled task must drop that reference. * The test for EXIT_ZOMBIE must occur while the runqueue locks are * still held, otherwise prev could be scheduled on another cpu, die * there before we look at prev->state, and then the reference would * be dropped twice. * Manfred Spraul */ prev_task_flags = prev->flags; finish_arch_switch(prev); finish_lock_switch(rq, prev); if (mm) mmdrop(mm); if (unlikely(prev_task_flags & PF_DEAD)) { /* * Remove function-return probe instances associated with this * task and put them back on the free list. */ kprobe_flush_task(prev); put_task_struct(prev); } } /** * schedule_tail - first thing a freshly forked thread must call. * @prev: the thread we just switched away from. */ asmlinkage void schedule_tail(task_t *prev) __releases(rq->lock) { runqueue_t *rq = this_rq(); finish_task_switch(rq, prev); #ifdef __ARCH_WANT_UNLOCKED_CTXSW /* In this case, finish_task_switch does not reenable preemption */ preempt_enable(); #endif if (current->set_child_tid) put_user(current->pid, current->set_child_tid); } /* * context_switch - switch to the new MM and the new * thread's register state. */ static inline task_t * context_switch(runqueue_t *rq, task_t *prev, task_t *next) { struct mm_struct *mm = next->mm; struct mm_struct *oldmm = prev->active_mm; if (unlikely(!mm)) { next->active_mm = oldmm; atomic_inc(&oldmm->mm_count); enter_lazy_tlb(oldmm, next); } else switch_mm(oldmm, mm, next); if (unlikely(!prev->mm)) { prev->active_mm = NULL; WARN_ON(rq->prev_mm); rq->prev_mm = oldmm; } /* Here we just switch the register state and the stack. */ switch_to(prev, next, prev); return prev; } /* * nr_running, nr_uninterruptible and nr_context_switches: * * externally visible scheduler statistics: current number of runnable * threads, current number of uninterruptible-sleeping threads, total * number of context switches performed since bootup. */ unsigned long nr_running(void) { unsigned long i, sum = 0; for_each_online_cpu(i) sum += cpu_rq(i)->nr_running; return sum; } unsigned long nr_uninterruptible(void) { unsigned long i, sum = 0; for_each_possible_cpu(i) sum += cpu_rq(i)->nr_uninterruptible; /* * Since we read the counters lockless, it might be slightly * inaccurate. Do not allow it to go below zero though: */ if (unlikely((long)sum < 0)) sum = 0; return sum; } unsigned long long nr_context_switches(void) { unsigned long long i, sum = 0; for_each_possible_cpu(i) sum += cpu_rq(i)->nr_switches; return sum; } unsigned long nr_iowait(void) { unsigned long i, sum = 0; for_each_possible_cpu(i) sum += atomic_read(&cpu_rq(i)->nr_iowait); return sum; } unsigned long nr_active(void) { unsigned long i, running = 0, uninterruptible = 0; for_each_online_cpu(i) { running += cpu_rq(i)->nr_running; uninterruptible += cpu_rq(i)->nr_uninterruptible; } if (unlikely((long)uninterruptible < 0)) uninterruptible = 0; return running + uninterruptible; } #ifdef CONFIG_SMP /* * double_rq_lock - safely lock two runqueues * * We must take them in cpu order to match code in * dependent_sleeper and wake_dependent_sleeper. * * Note this does not disable interrupts like task_rq_lock, * you need to do so manually before calling. */ static void double_rq_lock(runqueue_t *rq1, runqueue_t *rq2) __acquires(rq1->lock) __acquires(rq2->lock) { if (rq1 == rq2) { spin_lock(&rq1->lock); __acquire(rq2->lock); /* Fake it out ;) */ } else { if (rq1->cpu < rq2->cpu) { spin_lock(&rq1->lock); spin_lock(&rq2->lock); } else { spin_lock(&rq2->lock); spin_lock(&rq1->lock); } } } /* * double_rq_unlock - safely unlock two runqueues * * Note this does not restore interrupts like task_rq_unlock, * you need to do so manually after calling. */ static void double_rq_unlock(runqueue_t *rq1, runqueue_t *rq2) __releases(rq1->lock) __releases(rq2->lock) { spin_unlock(&rq1->lock); if (rq1 != rq2) spin_unlock(&rq2->lock); else __release(rq2->lock); } /* * double_lock_balance - lock the busiest runqueue, this_rq is locked already. */ static void double_lock_balance(runqueue_t *this_rq, runqueue_t *busiest) __releases(this_rq->lock) __acquires(busiest->lock) __acquires(this_rq->lock) { if (unlikely(!spin_trylock(&busiest->lock))) { if (busiest->cpu < this_rq->cpu) { spin_unlock(&this_rq->lock); spin_lock(&busiest->lock); spin_lock(&this_rq->lock); } else spin_lock(&busiest->lock); } } /* * If dest_cpu is allowed for this process, migrate the task to it. * This is accomplished by forcing the cpu_allowed mask to only * allow dest_cpu, which will force the cpu onto dest_cpu. Then * the cpu_allowed mask is restored. */ static void sched_migrate_task(task_t *p, int dest_cpu) { migration_req_t req; runqueue_t *rq; unsigned long flags; rq = task_rq_lock(p, &flags); if (!cpu_isset(dest_cpu, p->cpus_allowed) || unlikely(cpu_is_offline(dest_cpu))) goto out; /* force the process onto the specified CPU */ if (migrate_task(p, dest_cpu, &req)) { /* Need to wait for migration thread (might exit: take ref). */ struct task_struct *mt = rq->migration_thread; get_task_struct(mt); task_rq_unlock(rq, &flags); wake_up_process(mt); put_task_struct(mt); wait_for_completion(&req.done); return; } out: task_rq_unlock(rq, &flags); } /* * sched_exec - execve() is a valuable balancing opportunity, because at * this point the task has the smallest effective memory and cache footprint. */ void sched_exec(void) { int new_cpu, this_cpu = get_cpu(); new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC); put_cpu(); if (new_cpu != this_cpu) sched_migrate_task(current, new_cpu); } /* * pull_task - move a task from a remote runqueue to the local runqueue. * Both runqueues must be locked. */ static void pull_task(runqueue_t *src_rq, prio_array_t *src_array, task_t *p, runqueue_t *this_rq, prio_array_t *this_array, int this_cpu) { dequeue_task(p, src_array); src_rq->nr_running--; set_task_cpu(p, this_cpu); this_rq->nr_running++; enqueue_task(p, this_array); p->timestamp = (p->timestamp - src_rq->timestamp_last_tick) + this_rq->timestamp_last_tick; /* * Note that idle threads have a prio of MAX_PRIO, for this test * to be always true for them. */ if (TASK_PREEMPTS_CURR(p, this_rq)) resched_task(this_rq->curr); } /* * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? */ static int can_migrate_task(task_t *p, runqueue_t *rq, int this_cpu, struct sched_domain *sd, enum idle_type idle, int *all_pinned) { /* * We do not migrate tasks that are: * 1) running (obviously), or * 2) cannot be migrated to this CPU due to cpus_allowed, or * 3) are cache-hot on their current CPU. */ if (!cpu_isset(this_cpu, p->cpus_allowed)) return 0; *all_pinned = 0; if (task_running(rq, p)) return 0; /* * Aggressive migration if: * 1) task is cache cold, or * 2) too many balance attempts have failed. */ if (sd->nr_balance_failed > sd->cache_nice_tries) return 1; if (task_hot(p, rq->timestamp_last_tick, sd)) return 0; return 1; } /* * move_tasks tries to move up to max_nr_move tasks from busiest to this_rq, * as part of a balancing operation within "domain". Returns the number of * tasks moved. * * Called with both runqueues locked. */ static int move_tasks(runqueue_t *this_rq, int this_cpu, runqueue_t *busiest, unsigned long max_nr_move, struct sched_domain *sd, enum idle_type idle, int *all_pinned) { prio_array_t *array, *dst_array; struct list_head *head, *curr; int idx, pulled = 0, pinned = 0; task_t *tmp; if (max_nr_move == 0) goto out; pinned = 1; /* * We first consider expired tasks. Those will likely not be * executed in the near future, and they are most likely to * be cache-cold, thus switching CPUs has the least effect * on them. */ if (busiest->expired->nr_active) { array = busiest->expired; dst_array = this_rq->expired; } else { array = busiest->active; dst_array = this_rq->active; } new_array: /* Start searching at priority 0: */ idx = 0; skip_bitmap: if (!idx) idx = sched_find_first_bit(array->bitmap); else idx = find_next_bit(array->bitmap, MAX_PRIO, idx); if (idx >= MAX_PRIO) { if (array == busiest->expired && busiest->active->nr_active) { array = busiest->active; dst_array = this_rq->active; goto new_array; } goto out; } head = array->queue + idx; curr = head->prev; skip_queue: tmp = list_entry(curr, task_t, run_list); curr = curr->prev; if (!can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) { if (curr != head) goto skip_queue; idx++; goto skip_bitmap; } #ifdef CONFIG_SCHEDSTATS if (task_hot(tmp, busiest->timestamp_last_tick, sd)) schedstat_inc(sd, lb_hot_gained[idle]); #endif pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu); pulled++; /* We only want to steal up to the prescribed number of tasks. */ if (pulled < max_nr_move) { if (curr != head) goto skip_queue; idx++; goto skip_bitmap; } out: /* * Right now, this is the only place pull_task() is called, * so we can safely collect pull_task() stats here rather than * inside pull_task(). */ schedstat_add(sd, lb_gained[idle], pulled); if (all_pinned) *all_pinned = pinned; return pulled; } /* * find_busiest_group finds and returns the busiest CPU group within the * domain. It calculates and returns the number of tasks which should be * moved to restore balance via the imbalance parameter. */ static struct sched_group * find_busiest_group(struct sched_domain *sd, int this_cpu, unsigned long *imbalance, enum idle_type idle, int *sd_idle) { struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups; unsigned long max_load, avg_load, total_load, this_load, total_pwr; unsigned long max_pull; int load_idx; max_load = this_load = total_load = total_pwr = 0; if (idle == NOT_IDLE) load_idx = sd->busy_idx; else if (idle == NEWLY_IDLE) load_idx = sd->newidle_idx; else load_idx = sd->idle_idx; do { unsigned long load; int local_group; int i; local_group = cpu_isset(this_cpu, group->cpumask); /* Tally up the load of all CPUs in the group */ avg_load = 0; for_each_cpu_mask(i, group->cpumask) { if (*sd_idle && !idle_cpu(i)) *sd_idle = 0; /* Bias balancing toward cpus of our domain */ if (local_group) load = target_load(i, load_idx); else load = source_load(i, load_idx); avg_load += load; } total_load += avg_load; total_pwr += group->cpu_power; /* Adjust by relative CPU power of the group */ avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power; if (local_group) { this_load = avg_load; this = group; } else if (avg_load > max_load) { max_load = avg_load; busiest = group; } group = group->next; } while (group != sd->groups); if (!busiest || this_load >= max_load || max_load <= SCHED_LOAD_SCALE) goto out_balanced; avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr; if (this_load >= avg_load || 100*max_load <= sd->imbalance_pct*this_load) goto out_balanced; /* * We're trying to get all the cpus to the average_load, so we don't * want to push ourselves above the average load, nor do we wish to * reduce the max loaded cpu below the average load, as either of these * actions would just result in more rebalancing later, and ping-pong * tasks around. Thus we look for the minimum possible imbalance. * Negative imbalances (*we* are more loaded than anyone else) will * be counted as no imbalance for these purposes -- we can't fix that * by pulling tasks to us. Be careful of negative numbers as they'll * appear as very large values with unsigned longs. */ /* Don't want to pull so many tasks that a group would go idle */ max_pull = min(max_load - avg_load, max_load - SCHED_LOAD_SCALE); /* How much load to actually move to equalise the imbalance */ *imbalance = min(max_pull * busiest->cpu_power, (avg_load - this_load) * this->cpu_power) / SCHED_LOAD_SCALE; if (*imbalance < SCHED_LOAD_SCALE) { unsigned long pwr_now = 0, pwr_move = 0; unsigned long tmp; if (max_load - this_load >= SCHED_LOAD_SCALE*2) { *imbalance = 1; return busiest; } /* * OK, we don't have enough imbalance to justify moving tasks, * however we may be able to increase total CPU power used by * moving them. */ pwr_now += busiest->cpu_power*min(SCHED_LOAD_SCALE, max_load); pwr_now += this->cpu_power*min(SCHED_LOAD_SCALE, this_load); pwr_now /= SCHED_LOAD_SCALE; /* Amount of load we'd subtract */ tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/busiest->cpu_power; if (max_load > tmp) pwr_move += busiest->cpu_power*min(SCHED_LOAD_SCALE, max_load - tmp); /* Amount of load we'd add */ if (max_load*busiest->cpu_power < SCHED_LOAD_SCALE*SCHED_LOAD_SCALE) tmp = max_load*busiest->cpu_power/this->cpu_power; else tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/this->cpu_power; pwr_move += this->cpu_power*min(SCHED_LOAD_SCALE, this_load + tmp); pwr_move /= SCHED_LOAD_SCALE; /* Move if we gain throughput */ if (pwr_move <= pwr_now) goto out_balanced; *imbalance = 1; return busiest; } /* Get rid of the scaling factor, rounding down as we divide */ *imbalance = *imbalance / SCHED_LOAD_SCALE; return busiest; out_balanced: *imbalance = 0; return NULL; } /* * find_busiest_queue - find the busiest runqueue among the cpus in group. */ static runqueue_t *find_busiest_queue(struct sched_group *group, enum idle_type idle) { unsigned long load, max_load = 0; runqueue_t *busiest = NULL; int i; for_each_cpu_mask(i, group->cpumask) { load = source_load(i, 0); if (load > max_load) { max_load = load; busiest = cpu_rq(i); } } return busiest; } /* * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but * so long as it is large enough. */ #define MAX_PINNED_INTERVAL 512 /* * Check this_cpu to ensure it is balanced within domain. Attempt to move * tasks if there is an imbalance. * * Called with this_rq unlocked. */ static int load_balance(int this_cpu, runqueue_t *this_rq, struct sched_domain *sd, enum idle_type idle) { struct sched_group *group; runqueue_t *busiest; unsigned long imbalance; int nr_moved, all_pinned = 0; int active_balance = 0; int sd_idle = 0; if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER) sd_idle = 1; schedstat_inc(sd, lb_cnt[idle]); group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle); if (!group) { schedstat_inc(sd, lb_nobusyg[idle]); goto out_balanced; } busiest = find_busiest_queue(group, idle); if (!busiest) { schedstat_inc(sd, lb_nobusyq[idle]); goto out_balanced; } BUG_ON(busiest == this_rq); schedstat_add(sd, lb_imbalance[idle], imbalance); nr_moved = 0; if (busiest->nr_running > 1) { /* * Attempt to move tasks. If find_busiest_group has found * an imbalance but busiest->nr_running <= 1, the group is * still unbalanced. nr_moved simply stays zero, so it is * correctly treated as an imbalance. */ double_rq_lock(this_rq, busiest); nr_moved = move_tasks(this_rq, this_cpu, busiest, imbalance, sd, idle, &all_pinned); double_rq_unlock(this_rq, busiest); /* All tasks on this runqueue were pinned by CPU affinity */ if (unlikely(all_pinned)) goto out_balanced; } if (!nr_moved) { schedstat_inc(sd, lb_failed[idle]); sd->nr_balance_failed++; if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) { spin_lock(&busiest->lock); /* don't kick the migration_thread, if the curr * task on busiest cpu can't be moved to this_cpu */ if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) { spin_unlock(&busiest->lock); all_pinned = 1; goto out_one_pinned; } if (!busiest->active_balance) { busiest->active_balance = 1; busiest->push_cpu = this_cpu; active_balance = 1; } spin_unlock(&busiest->lock); if (active_balance) wake_up_process(busiest->migration_thread); /* * We've kicked active balancing, reset the failure * counter. */ sd->nr_balance_failed = sd->cache_nice_tries+1; } } else sd->nr_balance_failed = 0; if (likely(!active_balance)) { /* We were unbalanced, so reset the balancing interval */ sd->balance_interval = sd->min_interval; } else { /* * If we've begun active balancing, start to back off. This * case may not be covered by the all_pinned logic if there * is only 1 task on the busy runqueue (because we don't call * move_tasks). */ if (sd->balance_interval < sd->max_interval) sd->balance_interval *= 2; } if (!nr_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER) return -1; return nr_moved; out_balanced: schedstat_inc(sd, lb_balanced[idle]); sd->nr_balance_failed = 0; out_one_pinned: /* tune up the balancing interval */ if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) || (sd->balance_interval < sd->max_interval)) sd->balance_interval *= 2; if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER) return -1; return 0; } /* * Check this_cpu to ensure it is balanced within domain. Attempt to move * tasks if there is an imbalance. * * Called from schedule when this_rq is about to become idle (NEWLY_IDLE). * this_rq is locked. */ static int load_balance_newidle(int this_cpu, runqueue_t *this_rq, struct sched_domain *sd) { struct sched_group *group; runqueue_t *busiest = NULL; unsigned long imbalance; int nr_moved = 0; int sd_idle = 0; if (sd->flags & SD_SHARE_CPUPOWER) sd_idle = 1; schedstat_inc(sd, lb_cnt[NEWLY_IDLE]); group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE, &sd_idle); if (!group) { schedstat_inc(sd, lb_nobusyg[NEWLY_IDLE]); goto out_balanced; } busiest = find_busiest_queue(group, NEWLY_IDLE); if (!busiest) { schedstat_inc(sd, lb_nobusyq[NEWLY_IDLE]); goto out_balanced; } BUG_ON(busiest == this_rq); schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance); nr_moved = 0; if (busiest->nr_running > 1) { /* Attempt to move tasks */ double_lock_balance(this_rq, busiest); nr_moved = move_tasks(this_rq, this_cpu, busiest, imbalance, sd, NEWLY_IDLE, NULL); spin_unlock(&busiest->lock); } if (!nr_moved) { schedstat_inc(sd, lb_failed[NEWLY_IDLE]); if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER) return -1; } else sd->nr_balance_failed = 0; return nr_moved; out_balanced: schedstat_inc(sd, lb_balanced[NEWLY_IDLE]); if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER) return -1; sd->nr_balance_failed = 0; return 0; } /* * idle_balance is called by schedule() if this_cpu is about to become * idle. Attempts to pull tasks from other CPUs. */ static void idle_balance(int this_cpu, runqueue_t *this_rq) { struct sched_domain *sd; for_each_domain(this_cpu, sd) { if (sd->flags & SD_BALANCE_NEWIDLE) { if (load_balance_newidle(this_cpu, this_rq, sd)) { /* We've pulled tasks over so stop searching */ break; } } } } /* * active_load_balance is run by migration threads. It pushes running tasks * off the busiest CPU onto idle CPUs. It requires at least 1 task to be * running on each physical CPU where possible, and avoids physical / * logical imbalances. * * Called with busiest_rq locked. */ static void active_load_balance(runqueue_t *busiest_rq, int busiest_cpu) { struct sched_domain *sd; runqueue_t *target_rq; int target_cpu = busiest_rq->push_cpu; if (busiest_rq->nr_running <= 1) /* no task to move */ return; target_rq = cpu_rq(target_cpu); /* * This condition is "impossible", if it occurs * we need to fix it. Originally reported by * Bjorn Helgaas on a 128-cpu setup. */ BUG_ON(busiest_rq == target_rq); /* move a task from busiest_rq to target_rq */ double_lock_balance(busiest_rq, target_rq); /* Search for an sd spanning us and the target CPU. */ for_each_domain(target_cpu, sd) if ((sd->flags & SD_LOAD_BALANCE) && cpu_isset(busiest_cpu, sd->span)) break; if (unlikely(sd == NULL)) goto out; schedstat_inc(sd, alb_cnt); if (move_tasks(target_rq, target_cpu, busiest_rq, 1, sd, SCHED_IDLE, NULL)) schedstat_inc(sd, alb_pushed); else schedstat_inc(sd, alb_failed); out: spin_unlock(&target_rq->lock); } /* * rebalance_tick will get called every timer tick, on every CPU. * * It checks each scheduling domain to see if it is due to be balanced, * and initiates a balancing operation if so. * * Balancing parameters are set up in arch_init_sched_domains. */ /* Don't have all balancing operations going off at once */ #define CPU_OFFSET(cpu) (HZ * cpu / NR_CPUS) static void rebalance_tick(int this_cpu, runqueue_t *this_rq, enum idle_type idle) { unsigned long old_load, this_load; unsigned long j = jiffies + CPU_OFFSET(this_cpu); struct sched_domain *sd; int i; this_load = this_rq->nr_running * SCHED_LOAD_SCALE; /* Update our load */ for (i = 0; i < 3; i++) { unsigned long new_load = this_load; int scale = 1 << i; old_load = this_rq->cpu_load[i]; /* * Round up the averaging division if load is increasing. This * prevents us from getting stuck on 9 if the load is 10, for * example. */ if (new_load > old_load) new_load += scale-1; this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) / scale; } for_each_domain(this_cpu, sd) { unsigned long interval; if (!(sd->flags & SD_LOAD_BALANCE)) continue; interval = sd->balance_interval; if (idle != SCHED_IDLE) interval *= sd->busy_factor; /* scale ms to jiffies */ interval = msecs_to_jiffies(interval); if (unlikely(!interval)) interval = 1; if (j - sd->last_balance >= interval) { if (load_balance(this_cpu, this_rq, sd, idle)) { /* * We've pulled tasks over so either we're no * longer idle, or one of our SMT siblings is * not idle. */ idle = NOT_IDLE; } sd->last_balance += interval; } } } #else /* * on UP we do not need to balance between CPUs: */ static inline void rebalance_tick(int cpu, runqueue_t *rq, enum idle_type idle) { } static inline void idle_balance(int cpu, runqueue_t *rq) { } #endif static inline int wake_priority_sleeper(runqueue_t *rq) { int ret = 0; #ifdef CONFIG_SCHED_SMT spin_lock(&rq->lock); /* * If an SMT sibling task has been put to sleep for priority * reasons reschedule the idle task to see if it can now run. */ if (rq->nr_running) { resched_task(rq->idle); ret = 1; } spin_unlock(&rq->lock); #endif return ret; } DEFINE_PER_CPU(struct kernel_stat, kstat); EXPORT_PER_CPU_SYMBOL(kstat); /* * This is called on clock ticks and on context switches. * Bank in p->sched_time the ns elapsed since the last tick or switch. */ static inline void update_cpu_clock(task_t *p, runqueue_t *rq, unsigned long long now) { unsigned long long last = max(p->timestamp, rq->timestamp_last_tick); p->sched_time += now - last; } /* * Return current->sched_time plus any more ns on the sched_clock * that have not yet been banked. */ unsigned long long current_sched_time(const task_t *tsk) { unsigned long long ns; unsigned long flags; local_irq_save(flags); ns = max(tsk->timestamp, task_rq(tsk)->timestamp_last_tick); ns = tsk->sched_time + (sched_clock() - ns); local_irq_restore(flags); return ns; } /* * We place interactive tasks back into the active array, if possible. * * To guarantee that this does not starve expired tasks we ignore the * interactivity of a task if the first expired task had to wait more * than a 'reasonable' amount of time. This deadline timeout is * load-dependent, as the frequency of array switched decreases with * increasing number of running tasks. We also ignore the interactivity * if a better static_prio task has expired: */ #define EXPIRED_STARVING(rq) \ ((STARVATION_LIMIT && ((rq)->expired_timestamp && \ (jiffies - (rq)->expired_timestamp >= \ STARVATION_LIMIT * ((rq)->nr_running) + 1))) || \ ((rq)->curr->static_prio > (rq)->best_expired_prio)) /* * Account user cpu time to a process. * @p: the process that the cpu time gets accounted to * @hardirq_offset: the offset to subtract from hardirq_count() * @cputime: the cpu time spent in user space since the last update */ void account_user_time(struct task_struct *p, cputime_t cputime) { struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat; cputime64_t tmp; p->utime = cputime_add(p->utime, cputime); /* Add user time to cpustat. */ tmp = cputime_to_cputime64(cputime); if (TASK_NICE(p) > 0) cpustat->nice = cputime64_add(cpustat->nice, tmp); else cpustat->user = cputime64_add(cpustat->user, tmp); } /* * Account system cpu time to a process. * @p: the process that the cpu time gets accounted to * @hardirq_offset: the offset to subtract from hardirq_count() * @cputime: the cpu time spent in kernel space since the last update */ void account_system_time(struct task_struct *p, int hardirq_offset, cputime_t cputime) { struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat; runqueue_t *rq = this_rq(); cputime64_t tmp; p->stime = cputime_add(p->stime, cputime); /* Add system time to cpustat. */ tmp = cputime_to_cputime64(cputime); if (hardirq_count() - hardirq_offset) cpustat->irq = cputime64_add(cpustat->irq, tmp); else if (softirq_count()) cpustat->softirq = cputime64_add(cpustat->softirq, tmp); else if (p != rq->idle) cpustat->system = cputime64_add(cpustat->system, tmp); else if (atomic_read(&rq->nr_iowait) > 0) cpustat->iowait = cputime64_add(cpustat->iowait, tmp); else cpustat->idle = cputime64_add(cpustat->idle, tmp); /* Account for system time used */ acct_update_integrals(p); } /* * Account for involuntary wait time. * @p: the process from which the cpu time has been stolen * @steal: the cpu time spent in involuntary wait */ void account_steal_time(struct task_struct *p, cputime_t steal) { struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat; cputime64_t tmp = cputime_to_cputime64(steal); runqueue_t *rq = this_rq(); if (p == rq->idle) { p->stime = cputime_add(p->stime, steal); if (atomic_read(&rq->nr_iowait) > 0) cpustat->iowait = cputime64_add(cpustat->iowait, tmp); else cpustat->idle = cputime64_add(cpustat->idle, tmp); } else cpustat->steal = cputime64_add(cpustat->steal, tmp); } /* * This function gets called by the timer code, with HZ frequency. * We call it with interrupts disabled. * * It also gets called by the fork code, when changing the parent's * timeslices. */ void scheduler_tick(void) { int cpu = smp_processor_id(); runqueue_t *rq = this_rq(); task_t *p = current; unsigned long long now = sched_clock(); update_cpu_clock(p, rq, now); rq->timestamp_last_tick = now; if (p == rq->idle) { if (wake_priority_sleeper(rq)) goto out; rebalance_tick(cpu, rq, SCHED_IDLE); return; } /* Task might have expired already, but not scheduled off yet */ if (p->array != rq->active) { set_tsk_need_resched(p); goto out; } spin_lock(&rq->lock); /* * The task was running during this tick - update the * time slice counter. Note: we do not update a thread's * priority until it either goes to sleep or uses up its * timeslice. This makes it possible for interactive tasks * to use up their timeslices at their highest priority levels. */ if (rt_task(p)) { /* * RR tasks need a special form of timeslice management. * FIFO tasks have no timeslices. */ if ((p->policy == SCHED_RR) && !--p->time_slice) { p->time_slice = task_timeslice(p); p->first_time_slice = 0; set_tsk_need_resched(p); /* put it at the end of the queue: */ requeue_task(p, rq->active); } goto out_unlock; } if (!--p->time_slice) { dequeue_task(p, rq->active); set_tsk_need_resched(p); p->prio = effective_prio(p); p->time_slice = task_timeslice(p); p->first_time_slice = 0; if (!rq->expired_timestamp) rq->expired_timestamp = jiffies; if (!TASK_INTERACTIVE(p) || EXPIRED_STARVING(rq)) { enqueue_task(p, rq->expired); if (p->static_prio < rq->best_expired_prio) rq->best_expired_prio = p->static_prio; } else enqueue_task(p, rq->active); } else { /* * Prevent a too long timeslice allowing a task to monopolize * the CPU. We do this by splitting up the timeslice into * smaller pieces. * * Note: this does not mean the task's timeslices expire or * get lost in any way, they just might be preempted by * another task of equal priority. (one with higher * priority would have preempted this task already.) We * requeue this task to the end of the list on this priority * level, which is in essence a round-robin of tasks with * equal priority. * * This only applies to tasks in the interactive * delta range with at least TIMESLICE_GRANULARITY to requeue. */ if (TASK_INTERACTIVE(p) && !((task_timeslice(p) - p->time_slice) % TIMESLICE_GRANULARITY(p)) && (p->time_slice >= TIMESLICE_GRANULARITY(p)) && (p->array == rq->active)) { requeue_task(p, rq->active); set_tsk_need_resched(p); } } out_unlock: spin_unlock(&rq->lock); out: rebalance_tick(cpu, rq, NOT_IDLE); } #ifdef CONFIG_SCHED_SMT static inline void wakeup_busy_runqueue(runqueue_t *rq) { /* If an SMT runqueue is sleeping due to priority reasons wake it up */ if (rq->curr == rq->idle && rq->nr_running) resched_task(rq->idle); } static void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq) { struct sched_domain *tmp, *sd = NULL; cpumask_t sibling_map; int i; for_each_domain(this_cpu, tmp) if (tmp->flags & SD_SHARE_CPUPOWER) sd = tmp; if (!sd) return; /* * Unlock the current runqueue because we have to lock in * CPU order to avoid deadlocks. Caller knows that we might * unlock. We keep IRQs disabled. */ spin_unlock(&this_rq->lock); sibling_map = sd->span; for_each_cpu_mask(i, sibling_map) spin_lock(&cpu_rq(i)->lock); /* * We clear this CPU from the mask. This both simplifies the * inner loop and keps this_rq locked when we exit: */ cpu_clear(this_cpu, sibling_map); for_each_cpu_mask(i, sibling_map) { runqueue_t *smt_rq = cpu_rq(i); wakeup_busy_runqueue(smt_rq); } for_each_cpu_mask(i, sibling_map) spin_unlock(&cpu_rq(i)->lock); /* * We exit with this_cpu's rq still held and IRQs * still disabled: */ } /* * number of 'lost' timeslices this task wont be able to fully * utilize, if another task runs on a sibling. This models the * slowdown effect of other tasks running on siblings: */ static inline unsigned long smt_slice(task_t *p, struct sched_domain *sd) { return p->time_slice * (100 - sd->per_cpu_gain) / 100; } static int dependent_sleeper(int this_cpu, runqueue_t *this_rq) { struct sched_domain *tmp, *sd = NULL; cpumask_t sibling_map; prio_array_t *array; int ret = 0, i; task_t *p; for_each_domain(this_cpu, tmp) if (tmp->flags & SD_SHARE_CPUPOWER) sd = tmp; if (!sd) return 0; /* * The same locking rules and details apply as for * wake_sleeping_dependent(): */ spin_unlock(&this_rq->lock); sibling_map = sd->span; for_each_cpu_mask(i, sibling_map) spin_lock(&cpu_rq(i)->lock); cpu_clear(this_cpu, sibling_map); /* * Establish next task to be run - it might have gone away because * we released the runqueue lock above: */ if (!this_rq->nr_running) goto out_unlock; array = this_rq->active; if (!array->nr_active) array = this_rq->expired; BUG_ON(!array->nr_active); p = list_entry(array->queue[sched_find_first_bit(array->bitmap)].next, task_t, run_list); for_each_cpu_mask(i, sibling_map) { runqueue_t *smt_rq = cpu_rq(i); task_t *smt_curr = smt_rq->curr; /* Kernel threads do not participate in dependent sleeping */ if (!p->mm || !smt_curr->mm || rt_task(p)) goto check_smt_task; /* * If a user task with lower static priority than the * running task on the SMT sibling is trying to schedule, * delay it till there is proportionately less timeslice * left of the sibling task to prevent a lower priority * task from using an unfair proportion of the * physical cpu's resources. -ck */ if (rt_task(smt_curr)) { /* * With real time tasks we run non-rt tasks only * per_cpu_gain% of the time. */ if ((jiffies % DEF_TIMESLICE) > (sd->per_cpu_gain * DEF_TIMESLICE / 100)) ret = 1; } else if (smt_curr->static_prio < p->static_prio && !TASK_PREEMPTS_CURR(p, smt_rq) && smt_slice(smt_curr, sd) > task_timeslice(p)) ret = 1; check_smt_task: if ((!smt_curr->mm && smt_curr != smt_rq->idle) || rt_task(smt_curr)) continue; if (!p->mm) { wakeup_busy_runqueue(smt_rq); continue; } /* * Reschedule a lower priority task on the SMT sibling for * it to be put to sleep, or wake it up if it has been put to * sleep for priority reasons to see if it should run now. */ if (rt_task(p)) { if ((jiffies % DEF_TIMESLICE) > (sd->per_cpu_gain * DEF_TIMESLICE / 100)) resched_task(smt_curr); } else { if (TASK_PREEMPTS_CURR(p, smt_rq) && smt_slice(p, sd) > task_timeslice(smt_curr)) resched_task(smt_curr); else wakeup_busy_runqueue(smt_rq); } } out_unlock: for_each_cpu_mask(i, sibling_map) spin_unlock(&cpu_rq(i)->lock); return ret; } #else static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq) { } static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq) { return 0; } #endif #if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT) void fastcall add_preempt_count(int val) { /* * Underflow? */ BUG_ON((preempt_count() < 0)); preempt_count() += val; /* * Spinlock count overflowing soon? */ BUG_ON((preempt_count() & PREEMPT_MASK) >= PREEMPT_MASK-10); } EXPORT_SYMBOL(add_preempt_count); void fastcall sub_preempt_count(int val) { /* * Underflow? */ BUG_ON(val > preempt_count()); /* * Is the spinlock portion underflowing? */ BUG_ON((val < PREEMPT_MASK) && !(preempt_count() & PREEMPT_MASK)); preempt_count() -= val; } EXPORT_SYMBOL(sub_preempt_count); #endif static inline int interactive_sleep(enum sleep_type sleep_type) { return (sleep_type == SLEEP_INTERACTIVE || sleep_type == SLEEP_INTERRUPTED); } /* * schedule() is the main scheduler function. */ asmlinkage void __sched schedule(void) { long *switch_count; task_t *prev, *next; runqueue_t *rq; prio_array_t *array; struct list_head *queue; unsigned long long now; unsigned long run_time; int cpu, idx, new_prio; /* * Test if we are atomic. Since do_exit() needs to call into * schedule() atomically, we ignore that path for now. * Otherwise, whine if we are scheduling when we should not be. */ if (unlikely(in_atomic() && !current->exit_state)) { printk(KERN_ERR "BUG: scheduling while atomic: " "%s/0x%08x/%d\n", current->comm, preempt_count(), current->pid); dump_stack(); } profile_hit(SCHED_PROFILING, __builtin_return_address(0)); need_resched: preempt_disable(); prev = current; release_kernel_lock(prev); need_resched_nonpreemptible: rq = this_rq(); /* * The idle thread is not allowed to schedule! * Remove this check after it has been exercised a bit. */ if (unlikely(prev == rq->idle) && prev->state != TASK_RUNNING) { printk(KERN_ERR "bad: scheduling from the idle thread!\n"); dump_stack(); } schedstat_inc(rq, sched_cnt); now = sched_clock(); if (likely((long long)(now - prev->timestamp) < NS_MAX_SLEEP_AVG)) { run_time = now - prev->timestamp; if (unlikely((long long)(now - prev->timestamp) < 0)) run_time = 0; } else run_time = NS_MAX_SLEEP_AVG; /* * Tasks charged proportionately less run_time at high sleep_avg to * delay them losing their interactive status */ run_time /= (CURRENT_BONUS(prev) ? : 1); spin_lock_irq(&rq->lock); if (unlikely(prev->flags & PF_DEAD)) prev->state = EXIT_DEAD; 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 { if (prev->state == TASK_UNINTERRUPTIBLE) rq->nr_uninterruptible++; 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)) { 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; } idx = sched_find_first_bit(array->bitmap); queue = array->queue + idx; next = list_entry(queue->next, task_t, run_list); if (!rt_task(next) && interactive_sleep(next->sleep_type)) { unsigned long long delta = now - next->timestamp; if (unlikely((long long)(now - next->timestamp) < 0)) delta = 0; if (next->sleep_type == SLEEP_INTERACTIVE) delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128; array = next->array; new_prio = recalc_task_prio(next, next->timestamp + delta); if (unlikely(next->prio != new_prio)) { dequeue_task(next, array); next->prio = new_prio; enqueue_task(next, array); } } next->sleep_type = SLEEP_NORMAL; switch_tasks: if (next == rq->idle) schedstat_inc(rq, sched_goidle); prefetch(next); prefetch_stack(next); clear_tsk_need_resched(prev); rcu_qsctr_inc(task_cpu(prev)); update_cpu_clock(prev, rq, now); prev->sleep_avg -= run_time; if ((long)prev->sleep_avg <= 0) prev->sleep_avg = 0; 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_task_switch(rq, next); prev = context_switch(rq, prev, next); barrier(); /* * this_rq must be evaluated again because prev may have moved * CPUs since it called schedule(), thus the 'rq' on its stack * frame will be invalid. */ finish_task_switch(this_rq(), prev); } else spin_unlock_irq(&rq->lock); prev = current; if (unlikely(reacquire_kernel_lock(prev) < 0)) goto need_resched_nonpreemptible; 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(); #ifdef CONFIG_PREEMPT_BKL struct task_struct *task = current; int saved_lock_depth; #endif /* * 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: add_preempt_count(PREEMPT_ACTIVE); /* * We keep the big kernel semaphore locked, but we * clear ->lock_depth so that schedule() doesnt * auto-release the semaphore: */ #ifdef CONFIG_PREEMPT_BKL saved_lock_depth = task->lock_depth; task->lock_depth = -1; #endif schedule(); #ifdef CONFIG_PREEMPT_BKL task->lock_depth = saved_lock_depth; #endif sub_preempt_count(PREEMPT_ACTIVE); /* 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); /* * this is is the entry point to schedule() from kernel preemption * off of irq context. * Note, that this is called and return with irqs disabled. This will * protect us against recursive calling from irq. */ asmlinkage void __sched preempt_schedule_irq(void) { struct thread_info *ti = current_thread_info(); #ifdef CONFIG_PREEMPT_BKL struct task_struct *task = current; int saved_lock_depth; #endif /* Catch callers which need to be fixed*/ BUG_ON(ti->preempt_count || !irqs_disabled()); need_resched: add_preempt_count(PREEMPT_ACTIVE); /* * We keep the big kernel semaphore locked, but we * clear ->lock_depth so that schedule() doesnt * auto-release the semaphore: */ #ifdef CONFIG_PREEMPT_BKL saved_lock_depth = task->lock_depth; task->lock_depth = -1; #endif local_irq_enable(); schedule(); local_irq_disable(); #ifdef CONFIG_PREEMPT_BKL task->lock_depth = saved_lock_depth; #endif sub_preempt_count(PREEMPT_ACTIVE); /* we could miss a preemption opportunity between schedule and now */ barrier(); if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) goto need_resched; } #endif /* CONFIG_PREEMPT */ int default_wake_function(wait_queue_t *curr, unsigned mode, int sync, void *key) { task_t *p = curr->private; 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 * @key: is directly passed to the wakeup function */ 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); unsigned long fastcall __sched wait_for_completion_timeout(struct completion *x, unsigned long timeout) { 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); timeout = schedule_timeout(timeout); spin_lock_irq(&x->wait.lock); if (!timeout) { __remove_wait_queue(&x->wait, &wait); goto out; } } while (!x->done); __remove_wait_queue(&x->wait, &wait); } x->done--; out: spin_unlock_irq(&x->wait.lock); return timeout; } EXPORT_SYMBOL(wait_for_completion_timeout); int fastcall __sched wait_for_completion_interruptible(struct completion *x) { int ret = 0; 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 { if (signal_pending(current)) { ret = -ERESTARTSYS; __remove_wait_queue(&x->wait, &wait); goto out; } __set_current_state(TASK_INTERRUPTIBLE); spin_unlock_irq(&x->wait.lock); schedule(); spin_lock_irq(&x->wait.lock); } while (!x->done); __remove_wait_queue(&x->wait, &wait); } x->done--; out: spin_unlock_irq(&x->wait.lock); return ret; } EXPORT_SYMBOL(wait_for_completion_interruptible); unsigned long fastcall __sched wait_for_completion_interruptible_timeout(struct completion *x, unsigned long timeout) { 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 { if (signal_pending(current)) { timeout = -ERESTARTSYS; __remove_wait_queue(&x->wait, &wait); goto out; } __set_current_state(TASK_INTERRUPTIBLE); spin_unlock_irq(&x->wait.lock); timeout = schedule_timeout(timeout); spin_lock_irq(&x->wait.lock); if (!timeout) { __remove_wait_queue(&x->wait, &wait); goto out; } } while (!x->done); __remove_wait_queue(&x->wait, &wait); } x->done--; out: spin_unlock_irq(&x->wait.lock); return timeout; } EXPORT_SYMBOL(wait_for_completion_interruptible_timeout); #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 sched_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/SCHED_BATCH: */ 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); /* * can_nice - check if a task can reduce its nice value * @p: task * @nice: nice value */ int can_nice(const task_t *p, const int nice) { /* convert nice value [19,-20] to rlimit style value [1,40] */ int nice_rlim = 20 - nice; return (nice_rlim <= p->signal->rlim[RLIMIT_NICE].rlim_cur || capable(CAP_SYS_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 < -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; if (increment < 0 && !can_nice(current, nice)) return -EPERM; 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_GPL(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; } /** * idle_task - return the idle task for a given cpu. * @cpu: the processor in question. */ task_t *idle_task(int cpu) { return cpu_rq(cpu)->idle; } /** * 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 && policy != SCHED_BATCH) { p->prio = MAX_RT_PRIO-1 - p->rt_priority; } else { p->prio = p->static_prio; /* * SCHED_BATCH tasks are treated as perpetual CPU hogs: */ if (policy == SCHED_BATCH) p->sleep_avg = 0; } } /** * sched_setscheduler - change the scheduling policy and/or RT priority of * a thread. * @p: the task in question. * @policy: new policy. * @param: structure containing the new RT priority. */ int sched_setscheduler(struct task_struct *p, int policy, struct sched_param *param) { int retval; int oldprio, oldpolicy = -1; prio_array_t *array; unsigned long flags; runqueue_t *rq; recheck: /* double check policy once rq lock held */ if (policy < 0) policy = oldpolicy = p->policy; else if (policy != SCHED_FIFO && policy != SCHED_RR && policy != SCHED_NORMAL && policy != SCHED_BATCH) return -EINVAL; /* * Valid priorities for SCHED_FIFO and SCHED_RR are * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL and * SCHED_BATCH is 0. */ if (param->sched_priority < 0 || (p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) || (!p->mm && param->sched_priority > MAX_RT_PRIO-1)) return -EINVAL; if ((policy == SCHED_NORMAL || policy == SCHED_BATCH) != (param->sched_priority == 0)) return -EINVAL; /* * Allow unprivileged RT tasks to decrease priority: */ if (!capable(CAP_SYS_NICE)) { /* * can't change policy, except between SCHED_NORMAL * and SCHED_BATCH: */ if (((policy != SCHED_NORMAL && p->policy != SCHED_BATCH) && (policy != SCHED_BATCH && p->policy != SCHED_NORMAL)) && !p->signal->rlim[RLIMIT_RTPRIO].rlim_cur) return -EPERM; /* can't increase priority */ if ((policy != SCHED_NORMAL && policy != SCHED_BATCH) && param->sched_priority > p->rt_priority && param->sched_priority > p->signal->rlim[RLIMIT_RTPRIO].rlim_cur) return -EPERM; /* can't change other user's priorities */ if ((current->euid != p->euid) && (current->euid != p->uid)) return -EPERM; } retval = security_task_setscheduler(p, policy, param); if (retval) return retval; /* * To be able to change p->policy safely, the apropriate * runqueue lock must be held. */ rq = task_rq_lock(p, &flags); /* recheck policy now with rq lock held */ if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) { policy = oldpolicy = -1; task_rq_unlock(rq, &flags); goto recheck; } array = p->array; if (array) deactivate_task(p, rq); oldprio = p->prio; __setscheduler(p, policy, param->sched_priority); if (array) { __activate_task(p, rq); /* * 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); } task_rq_unlock(rq, &flags); return 0; } EXPORT_SYMBOL_GPL(sched_setscheduler); static int do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param) { int retval; struct sched_param lparam; struct task_struct *p; if (!param || pid < 0) return -EINVAL; if (copy_from_user(&lparam, param, sizeof(struct sched_param))) return -EFAULT; read_lock_irq(&tasklist_lock); p = find_process_by_pid(pid); if (!p) { read_unlock_irq(&tasklist_lock); return -ESRCH; } retval = sched_setscheduler(p, policy, &lparam); read_unlock_irq(&tasklist_lock); 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) { /* negative values for policy are not valid */ if (policy < 0) return -EINVAL; return do_sched_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 do_sched_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; cpumask_t cpus_allowed; 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 = security_task_setscheduler(p, 0, NULL); if (retval) goto out_unlock; cpus_allowed = cpuset_cpus_allowed(p); cpus_and(new_mask, new_mask, cpus_allowed); 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 __read_mostly; EXPORT_SYMBOL(cpu_present_map); #ifndef CONFIG_SMP cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL; cpumask_t cpu_possible_map __read_mostly = 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 = security_task_getscheduler(p); if (retval) goto out_unlock; cpus_and(*mask, p->cpus_allowed, cpu_online_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 (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); if (array != target) { dequeue_task(current, array); enqueue_task(current, target); } else /* * requeue_task is cheaper so perform that if possible. */ requeue_task(current, array); /* * Since we are going to call schedule() anyway, there's * no need to preempt or enable interrupts: */ __release(rq->lock); _raw_spin_unlock(&rq->lock); preempt_enable_no_resched(); schedule(); return 0; } static inline void __cond_resched(void) { #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP __might_sleep(__FILE__, __LINE__); #endif /* * The BKS might be reacquired before we have dropped * PREEMPT_ACTIVE, which could trigger a second * cond_resched() call. */ if (unlikely(preempt_count())) return; if (unlikely(system_state != SYSTEM_RUNNING)) return; do { add_preempt_count(PREEMPT_ACTIVE); schedule(); sub_preempt_count(PREEMPT_ACTIVE); } while (need_resched()); } int __sched cond_resched(void) { if (need_resched()) { __cond_resched(); return 1; } return 0; } EXPORT_SYMBOL(cond_resched); /* * cond_resched_lock() - if a reschedule is pending, drop the given lock, * call schedule, and on return reacquire the lock. * * This works OK both with and without CONFIG_PREEMPT. We do strange low-level * operations here to prevent schedule() from being called twice (once via * spin_unlock(), once by hand). */ int cond_resched_lock(spinlock_t *lock) { int ret = 0; if (need_lockbreak(lock)) { spin_unlock(lock); cpu_relax(); ret = 1; spin_lock(lock); } if (need_resched()) { _raw_spin_unlock(lock); preempt_enable_no_resched(); __cond_resched(); ret = 1; spin_lock(lock); } return ret; } EXPORT_SYMBOL(cond_resched_lock); int __sched cond_resched_softirq(void) { BUG_ON(!in_softirq()); if (need_resched()) { __local_bh_enable(); __cond_resched(); local_bh_disable(); return 1; } return 0; } EXPORT_SYMBOL(cond_resched_softirq); /** * 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 = &__raw_get_cpu_var(runqueues); 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 = &__raw_get_cpu_var(runqueues); 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: case SCHED_BATCH: 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: case SCHED_BATCH: 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 = end_of_stack(p); while (!*n) n++; free = (unsigned long)n - (unsigned long)end_of_stack(p); } #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); mutex_debug_show_all_locks(); } /** * init_idle - set up an idle thread for a given CPU * @idle: task in question * @cpu: cpu the idle task belongs to * * NOTE: this function does not set the idle thread's NEED_RESCHED * flag, to make booting more robust. */ void __devinit init_idle(task_t *idle, int cpu) { runqueue_t *rq = cpu_rq(cpu); unsigned long flags; idle->timestamp = sched_clock(); idle->sleep_avg = 0; idle->array = NULL; idle->prio = MAX_PRIO; idle->state = TASK_RUNNING; idle->cpus_allowed = cpumask_of_cpu(cpu); set_task_cpu(idle, cpu); spin_lock_irqsave(&rq->lock, flags); rq->curr = rq->idle = idle; #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW) idle->oncpu = 1; #endif spin_unlock_irqrestore(&rq->lock, flags); /* Set the preempt count _outside_ the spinlocks! */ #if defined(CONFIG_PREEMPT) && !defined(CONFIG_PREEMPT_BKL) task_thread_info(idle)->preempt_count = (idle->lock_depth >= 0); #else task_thread_info(idle)->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; try_to_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); spin_unlock(&rq->lock); __migrate_task(req->task, cpu, req->dest_cpu); local_irq_enable(); 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); } /* * While a dead CPU has no uninterruptible tasks queued at this point, * it might still have a nonzero ->nr_uninterruptible counter, because * for performance reasons the counter is not stricly tracking tasks to * their home CPUs. So we just add the counter to another CPU's counter, * to keep the global sum constant after CPU-down: */ static void migrate_nr_uninterruptible(runqueue_t *rq_src) { runqueue_t *rq_dest = cpu_rq(any_online_cpu(CPU_MASK_ALL)); unsigned long flags; local_irq_save(flags); double_rq_lock(rq_src, rq_dest); rq_dest->nr_uninterruptible += rq_src->nr_uninterruptible; rq_src->nr_uninterruptible = 0; double_rq_unlock(rq_src, rq_dest); local_irq_restore(flags); } /* 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); } /* Ensures that the idle task is using init_mm right before its cpu goes * offline. */ void idle_task_exit(void) { struct mm_struct *mm = current->active_mm; BUG_ON(cpu_online(smp_processor_id())); if (mm != &init_mm) switch_mm(mm, &init_mm, current); mmdrop(mm); } 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->exit_state != EXIT_ZOMBIE && tsk->exit_state != EXIT_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: if (!cpu_rq(cpu)->migration_thread) break; /* Unbind it from offline cpu so it can run. Fall thru. */ kthread_bind(cpu_rq(cpu)->migration_thread, any_online_cpu(cpu_online_map)); 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); migrate_nr_uninterruptible(rq); 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); 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 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 #ifdef CONFIG_SMP #undef SCHED_DOMAIN_DEBUG #ifdef SCHED_DOMAIN_DEBUG static void sched_domain_debug(struct sched_domain *sd, int cpu) { int level = 0; if (!sd) { printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu); return; } printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu); do { int i; 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 (i = 0; i < level + 1; i++) printk(" "); printk("domain %d: ", level); if (!(sd->flags & SD_LOAD_BALANCE)) { printk("does not load-balance\n"); if (sd->parent) printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain has parent"); break; } printk("span %s\n", str); if (!cpu_isset(cpu, sd->span)) printk(KERN_ERR "ERROR: domain->span does not contain CPU%d\n", cpu); if (!cpu_isset(cpu, group->cpumask)) printk(KERN_ERR "ERROR: domain->groups does not contain CPU%d\n", cpu); printk(KERN_DEBUG); for (i = 0; i < level + 2; i++) printk(" "); printk("groups:"); do { if (!group) { printk("\n"); printk(KERN_ERR "ERROR: group is NULL\n"); break; } if (!group->cpu_power) { printk("\n"); printk(KERN_ERR "ERROR: domain->cpu_power not set\n"); } if (!cpus_weight(group->cpumask)) { printk("\n"); printk(KERN_ERR "ERROR: empty group\n"); } if (cpus_intersects(groupmask, group->cpumask)) { printk("\n"); printk(KERN_ERR "ERROR: repeated CPUs\n"); } 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_ERR "ERROR: groups don't span domain->span\n"); level++; sd = sd->parent; if (sd) { if (!cpus_subset(groupmask, sd->span)) printk(KERN_ERR "ERROR: parent span is not a superset of domain->span\n"); } } while (sd); } #else #define sched_domain_debug(sd, cpu) {} #endif static int sd_degenerate(struct sched_domain *sd) { if (cpus_weight(sd->span) == 1) return 1; /* Following flags need at least 2 groups */ if (sd->flags & (SD_LOAD_BALANCE | SD_BALANCE_NEWIDLE | SD_BALANCE_FORK | SD_BALANCE_EXEC)) { if (sd->groups != sd->groups->next) return 0; } /* Following flags don't use groups */ if (sd->flags & (SD_WAKE_IDLE | SD_WAKE_AFFINE | SD_WAKE_BALANCE)) return 0; return 1; } static int sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent) { unsigned long cflags = sd->flags, pflags = parent->flags; if (sd_degenerate(parent)) return 1; if (!cpus_equal(sd->span, parent->span)) return 0; /* Does parent contain flags not in child? */ /* WAKE_BALANCE is a subset of WAKE_AFFINE */ if (cflags & SD_WAKE_AFFINE) pflags &= ~SD_WAKE_BALANCE; /* Flags needing groups don't count if only 1 group in parent */ if (parent->groups == parent->groups->next) { pflags &= ~(SD_LOAD_BALANCE | SD_BALANCE_NEWIDLE | SD_BALANCE_FORK | SD_BALANCE_EXEC); } if (~cflags & pflags) return 0; return 1; } /* * Attach the domain 'sd' to 'cpu' as its base domain. Callers must * hold the hotplug lock. */ static void cpu_attach_domain(struct sched_domain *sd, int cpu) { runqueue_t *rq = cpu_rq(cpu); struct sched_domain *tmp; /* Remove the sched domains which do not contribute to scheduling. */ for (tmp = sd; tmp; tmp = tmp->parent) { struct sched_domain *parent = tmp->parent; if (!parent) break; if (sd_parent_degenerate(tmp, parent)) tmp->parent = parent->parent; } if (sd && sd_degenerate(sd)) sd = sd->parent; sched_domain_debug(sd, cpu); rcu_assign_pointer(rq->sd, sd); } /* cpus with isolated domains */ static cpumask_t __devinitdata cpu_isolated_map = CPU_MASK_NONE; /* 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++) if (ints[i] < NR_CPUS) 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. */ 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; } #define SD_NODES_PER_DOMAIN 16 /* * Self-tuning task migration cost measurement between source and target CPUs. * * This is done by measuring the cost of manipulating buffers of varying * sizes. For a given buffer-size here are the steps that are taken: * * 1) the source CPU reads+dirties a shared buffer * 2) the target CPU reads+dirties the same shared buffer * * We measure how long they take, in the following 4 scenarios: * * - source: CPU1, target: CPU2 | cost1 * - source: CPU2, target: CPU1 | cost2 * - source: CPU1, target: CPU1 | cost3 * - source: CPU2, target: CPU2 | cost4 * * We then calculate the cost3+cost4-cost1-cost2 difference - this is * the cost of migration. * * We then start off from a small buffer-size and iterate up to larger * buffer sizes, in 5% steps - measuring each buffer-size separately, and * doing a maximum search for the cost. (The maximum cost for a migration * normally occurs when the working set size is around the effective cache * size.) */ #define SEARCH_SCOPE 2 #define MIN_CACHE_SIZE (64*1024U) #define DEFAULT_CACHE_SIZE (5*1024*1024U) #define ITERATIONS 1 #define SIZE_THRESH 130 #define COST_THRESH 130 /* * The migration cost is a function of 'domain distance'. Domain * distance is the number of steps a CPU has to iterate down its * domain tree to share a domain with the other CPU. The farther * two CPUs are from each other, the larger the distance gets. * * Note that we use the distance only to cache measurement results, * the distance value is not used numerically otherwise. When two * CPUs have the same distance it is assumed that the migration * cost is the same. (this is a simplification but quite practical) */ #define MAX_DOMAIN_DISTANCE 32 static unsigned long long migration_cost[MAX_DOMAIN_DISTANCE] = { [ 0 ... MAX_DOMAIN_DISTANCE-1 ] = /* * Architectures may override the migration cost and thus avoid * boot-time calibration. Unit is nanoseconds. Mostly useful for * virtualized hardware: */ #ifdef CONFIG_DEFAULT_MIGRATION_COST CONFIG_DEFAULT_MIGRATION_COST #else -1LL #endif }; /* * Allow override of migration cost - in units of microseconds. * E.g. migration_cost=1000,2000,3000 will set up a level-1 cost * of 1 msec, level-2 cost of 2 msecs and level3 cost of 3 msecs: */ static int __init migration_cost_setup(char *str) { int ints[MAX_DOMAIN_DISTANCE+1], i; str = get_options(str, ARRAY_SIZE(ints), ints); printk("#ints: %d\n", ints[0]); for (i = 1; i <= ints[0]; i++) { migration_cost[i-1] = (unsigned long long)ints[i]*1000; printk("migration_cost[%d]: %Ld\n", i-1, migration_cost[i-1]); } return 1; } __setup ("migration_cost=", migration_cost_setup); /* * Global multiplier (divisor) for migration-cutoff values, * in percentiles. E.g. use a value of 150 to get 1.5 times * longer cache-hot cutoff times. * * (We scale it from 100 to 128 to long long handling easier.) */ #define MIGRATION_FACTOR_SCALE 128 static unsigned int migration_factor = MIGRATION_FACTOR_SCALE; static int __init setup_migration_factor(char *str) { get_option(&str, &migration_factor); migration_factor = migration_factor * MIGRATION_FACTOR_SCALE / 100; return 1; } __setup("migration_factor=", setup_migration_factor); /* * Estimated distance of two CPUs, measured via the number of domains * we have to pass for the two CPUs to be in the same span: */ static unsigned long domain_distance(int cpu1, int cpu2) { unsigned long distance = 0; struct sched_domain *sd; for_each_domain(cpu1, sd) { WARN_ON(!cpu_isset(cpu1, sd->span)); if (cpu_isset(cpu2, sd->span)) return distance; distance++; } if (distance >= MAX_DOMAIN_DISTANCE) { WARN_ON(1); distance = MAX_DOMAIN_DISTANCE-1; } return distance; } static unsigned int migration_debug; static int __init setup_migration_debug(char *str) { get_option(&str, &migration_debug); return 1; } __setup("migration_debug=", setup_migration_debug); /* * Maximum cache-size that the scheduler should try to measure. * Architectures with larger caches should tune this up during * bootup. Gets used in the domain-setup code (i.e. during SMP * bootup). */ unsigned int max_cache_size; static int __init setup_max_cache_size(char *str) { get_option(&str, &max_cache_size); return 1; } __setup("max_cache_size=", setup_max_cache_size); /* * Dirty a big buffer in a hard-to-predict (for the L2 cache) way. This * is the operation that is timed, so we try to generate unpredictable * cachemisses that still end up filling the L2 cache: */ static void touch_cache(void *__cache, unsigned long __size) { unsigned long size = __size/sizeof(long), chunk1 = size/3, chunk2 = 2*size/3; unsigned long *cache = __cache; int i; for (i = 0; i < size/6; i += 8) { switch (i % 6) { case 0: cache[i]++; case 1: cache[size-1-i]++; case 2: cache[chunk1-i]++; case 3: cache[chunk1+i]++; case 4: cache[chunk2-i]++; case 5: cache[chunk2+i]++; } } } /* * Measure the cache-cost of one task migration. Returns in units of nsec. */ static unsigned long long measure_one(void *cache, unsigned long size, int source, int target) { cpumask_t mask, saved_mask; unsigned long long t0, t1, t2, t3, cost; saved_mask = current->cpus_allowed; /* * Flush source caches to RAM and invalidate them: */ sched_cacheflush(); /* * Migrate to the source CPU: */ mask = cpumask_of_cpu(source); set_cpus_allowed(current, mask); WARN_ON(smp_processor_id() != source); /* * Dirty the working set: */ t0 = sched_clock(); touch_cache(cache, size); t1 = sched_clock(); /* * Migrate to the target CPU, dirty the L2 cache and access * the shared buffer. (which represents the working set * of a migrated task.) */ mask = cpumask_of_cpu(target); set_cpus_allowed(current, mask); WARN_ON(smp_processor_id() != target); t2 = sched_clock(); touch_cache(cache, size); t3 = sched_clock(); cost = t1-t0 + t3-t2; if (migration_debug >= 2) printk("[%d->%d]: %8Ld %8Ld %8Ld => %10Ld.\n", source, target, t1-t0, t1-t0, t3-t2, cost); /* * Flush target caches to RAM and invalidate them: */ sched_cacheflush(); set_cpus_allowed(current, saved_mask); return cost; } /* * Measure a series of task migrations and return the average * result. Since this code runs early during bootup the system * is 'undisturbed' and the average latency makes sense. * * The algorithm in essence auto-detects the relevant cache-size, * so it will properly detect different cachesizes for different * cache-hierarchies, depending on how the CPUs are connected. * * Architectures can prime the upper limit of the search range via * max_cache_size, otherwise the search range defaults to 20MB...64K. */ static unsigned long long measure_cost(int cpu1, int cpu2, void *cache, unsigned int size) { unsigned long long cost1, cost2; int i; /* * Measure the migration cost of 'size' bytes, over an * average of 10 runs: * * (We perturb the cache size by a small (0..4k) * value to compensate size/alignment related artifacts. * We also subtract the cost of the operation done on * the same CPU.) */ cost1 = 0; /* * dry run, to make sure we start off cache-cold on cpu1, * and to get any vmalloc pagefaults in advance: */ measure_one(cache, size, cpu1, cpu2); for (i = 0; i < ITERATIONS; i++) cost1 += measure_one(cache, size - i*1024, cpu1, cpu2); measure_one(cache, size, cpu2, cpu1); for (i = 0; i < ITERATIONS; i++) cost1 += measure_one(cache, size - i*1024, cpu2, cpu1); /* * (We measure the non-migrating [cached] cost on both * cpu1 and cpu2, to handle CPUs with different speeds) */ cost2 = 0; measure_one(cache, size, cpu1, cpu1); for (i = 0; i < ITERATIONS; i++) cost2 += measure_one(cache, size - i*1024, cpu1, cpu1); measure_one(cache, size, cpu2, cpu2); for (i = 0; i < ITERATIONS; i++) cost2 += measure_one(cache, size - i*1024, cpu2, cpu2); /* * Get the per-iteration migration cost: */ do_div(cost1, 2*ITERATIONS); do_div(cost2, 2*ITERATIONS); return cost1 - cost2; } static unsigned long long measure_migration_cost(int cpu1, int cpu2) { unsigned long long max_cost = 0, fluct = 0, avg_fluct = 0; unsigned int max_size, size, size_found = 0; long long cost = 0, prev_cost; void *cache; /* * Search from max_cache_size*5 down to 64K - the real relevant * cachesize has to lie somewhere inbetween. */ if (max_cache_size) { max_size = max(max_cache_size * SEARCH_SCOPE, MIN_CACHE_SIZE); size = max(max_cache_size / SEARCH_SCOPE, MIN_CACHE_SIZE); } else { /* * Since we have no estimation about the relevant * search range */ max_size = DEFAULT_CACHE_SIZE * SEARCH_SCOPE; size = MIN_CACHE_SIZE; } if (!cpu_online(cpu1) || !cpu_online(cpu2)) { printk("cpu %d and %d not both online!\n", cpu1, cpu2); return 0; } /* * Allocate the working set: */ cache = vmalloc(max_size); if (!cache) { printk("could not vmalloc %d bytes for cache!\n", 2*max_size); return 1000000; // return 1 msec on very small boxen } while (size <= max_size) { prev_cost = cost; cost = measure_cost(cpu1, cpu2, cache, size); /* * Update the max: */ if (cost > 0) { if (max_cost < cost) { max_cost = cost; size_found = size; } } /* * Calculate average fluctuation, we use this to prevent * noise from triggering an early break out of the loop: */ fluct = abs(cost - prev_cost); avg_fluct = (avg_fluct + fluct)/2; if (migration_debug) printk("-> [%d][%d][%7d] %3ld.%ld [%3ld.%ld] (%ld): (%8Ld %8Ld)\n", cpu1, cpu2, size, (long)cost / 1000000, ((long)cost / 100000) % 10, (long)max_cost / 1000000, ((long)max_cost / 100000) % 10, domain_distance(cpu1, cpu2), cost, avg_fluct); /* * If we iterated at least 20% past the previous maximum, * and the cost has dropped by more than 20% already, * (taking fluctuations into account) then we assume to * have found the maximum and break out of the loop early: */ if (size_found && (size*100 > size_found*SIZE_THRESH)) if (cost+avg_fluct <= 0 || max_cost*100 > (cost+avg_fluct)*COST_THRESH) { if (migration_debug) printk("-> found max.\n"); break; } /* * Increase the cachesize in 10% steps: */ size = size * 10 / 9; } if (migration_debug) printk("[%d][%d] working set size found: %d, cost: %Ld\n", cpu1, cpu2, size_found, max_cost); vfree(cache); /* * A task is considered 'cache cold' if at least 2 times * the worst-case cost of migration has passed. * * (this limit is only listened to if the load-balancing * situation is 'nice' - if there is a large imbalance we * ignore it for the sake of CPU utilization and * processing fairness.) */ return 2 * max_cost * migration_factor / MIGRATION_FACTOR_SCALE; } static void calibrate_migration_costs(const cpumask_t *cpu_map) { int cpu1 = -1, cpu2 = -1, cpu, orig_cpu = raw_smp_processor_id(); unsigned long j0, j1, distance, max_distance = 0; struct sched_domain *sd; j0 = jiffies; /* * First pass - calculate the cacheflush times: */ for_each_cpu_mask(cpu1, *cpu_map) { for_each_cpu_mask(cpu2, *cpu_map) { if (cpu1 == cpu2) continue; distance = domain_distance(cpu1, cpu2); max_distance = max(max_distance, distance); /* * No result cached yet? */ if (migration_cost[distance] == -1LL) migration_cost[distance] = measure_migration_cost(cpu1, cpu2); } } /* * Second pass - update the sched domain hierarchy with * the new cache-hot-time estimations: */ for_each_cpu_mask(cpu, *cpu_map) { distance = 0; for_each_domain(cpu, sd) { sd->cache_hot_time = migration_cost[distance]; distance++; } } /* * Print the matrix: */ if (migration_debug) printk("migration: max_cache_size: %d, cpu: %d MHz:\n", max_cache_size, #ifdef CONFIG_X86 cpu_khz/1000 #else -1 #endif ); if (system_state == SYSTEM_BOOTING) { printk("migration_cost="); for (distance = 0; distance <= max_distance; distance++) { if (distance) printk(","); printk("%ld", (long)migration_cost[distance] / 1000); } printk("\n"); } j1 = jiffies; if (migration_debug) printk("migration: %ld seconds\n", (j1-j0)/HZ); /* * Move back to the original CPU. NUMA-Q gets confused * if we migrate to another quad during bootup. */ if (raw_smp_processor_id() != orig_cpu) { cpumask_t mask = cpumask_of_cpu(orig_cpu), saved_mask = current->cpus_allowed; set_cpus_allowed(current, mask); set_cpus_allowed(current, saved_mask); } } #ifdef CONFIG_NUMA /** * 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 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 < MAX_NUMNODES; i++) { /* Start at @node */ n = (node + i) % MAX_NUMNODES; if (!nr_cpus_node(n)) continue; /* Skip already used nodes */ if (test_bit(n, used_nodes)) continue; /* Simple min distance search */ val = node_distance(node, n); 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. */ static cpumask_t sched_domain_node_span(int node) { int i; cpumask_t span, nodemask; DECLARE_BITMAP(used_nodes, MAX_NUMNODES); cpus_clear(span); bitmap_zero(used_nodes, MAX_NUMNODES); nodemask = node_to_cpumask(node); cpus_or(span, span, nodemask); set_bit(node, used_nodes); for (i = 1; i < SD_NODES_PER_DOMAIN; i++) { int next_node = find_next_best_node(node, used_nodes); nodemask = node_to_cpumask(next_node); cpus_or(span, span, nodemask); } return span; } #endif /* * At the moment, CONFIG_SCHED_SMT is never defined, but leave it in so we * can switch it on easily if needed. */ #ifdef CONFIG_SCHED_SMT static DEFINE_PER_CPU(struct sched_domain, cpu_domains); static struct sched_group sched_group_cpus[NR_CPUS]; static int cpu_to_cpu_group(int cpu) { return cpu; } #endif #ifdef CONFIG_SCHED_MC static DEFINE_PER_CPU(struct sched_domain, core_domains); static struct sched_group sched_group_core[NR_CPUS]; #endif #if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT) static int cpu_to_core_group(int cpu) { return first_cpu(cpu_sibling_map[cpu]); } #elif defined(CONFIG_SCHED_MC) static int cpu_to_core_group(int cpu) { return cpu; } #endif static DEFINE_PER_CPU(struct sched_domain, phys_domains); static struct sched_group sched_group_phys[NR_CPUS]; static int cpu_to_phys_group(int cpu) { #if defined(CONFIG_SCHED_MC) cpumask_t mask = cpu_coregroup_map(cpu); return first_cpu(mask); #elif defined(CONFIG_SCHED_SMT) return first_cpu(cpu_sibling_map[cpu]); #else return cpu; #endif } #ifdef CONFIG_NUMA /* * The init_sched_build_groups can't handle what we want to do with node * groups, so roll our own. Now each node has its own list of groups which * gets dynamically allocated. */ static DEFINE_PER_CPU(struct sched_domain, node_domains); static struct sched_group **sched_group_nodes_bycpu[NR_CPUS]; static DEFINE_PER_CPU(struct sched_domain, allnodes_domains); static struct sched_group *sched_group_allnodes_bycpu[NR_CPUS]; static int cpu_to_allnodes_group(int cpu) { return cpu_to_node(cpu); } static void init_numa_sched_groups_power(struct sched_group *group_head) { struct sched_group *sg = group_head; int j; if (!sg) return; next_sg: for_each_cpu_mask(j, sg->cpumask) { struct sched_domain *sd; sd = &per_cpu(phys_domains, j); if (j != first_cpu(sd->groups->cpumask)) { /* * Only add "power" once for each * physical package. */ continue; } sg->cpu_power += sd->groups->cpu_power; } sg = sg->next; if (sg != group_head) goto next_sg; } #endif /* * Build sched domains for a given set of cpus and attach the sched domains * to the individual cpus */ void build_sched_domains(const cpumask_t *cpu_map) { int i; #ifdef CONFIG_NUMA struct sched_group **sched_group_nodes = NULL; struct sched_group *sched_group_allnodes = NULL; /* * Allocate the per-node list of sched groups */ sched_group_nodes = kmalloc(sizeof(struct sched_group*)*MAX_NUMNODES, GFP_ATOMIC); if (!sched_group_nodes) { printk(KERN_WARNING "Can not alloc sched group node list\n"); return; } sched_group_nodes_bycpu[first_cpu(*cpu_map)] = sched_group_nodes; #endif /* * Set up domains for cpus specified by the cpu_map. */ for_each_cpu_mask(i, *cpu_map) { int group; struct sched_domain *sd = NULL, *p; cpumask_t nodemask = node_to_cpumask(cpu_to_node(i)); cpus_and(nodemask, nodemask, *cpu_map); #ifdef CONFIG_NUMA if (cpus_weight(*cpu_map) > SD_NODES_PER_DOMAIN*cpus_weight(nodemask)) { if (!sched_group_allnodes) { sched_group_allnodes = kmalloc(sizeof(struct sched_group) * MAX_NUMNODES, GFP_KERNEL); if (!sched_group_allnodes) { printk(KERN_WARNING "Can not alloc allnodes sched group\n"); break; } sched_group_allnodes_bycpu[i] = sched_group_allnodes; } sd = &per_cpu(allnodes_domains, i); *sd = SD_ALLNODES_INIT; sd->span = *cpu_map; group = cpu_to_allnodes_group(i); sd->groups = &sched_group_allnodes[group]; p = sd; } else p = NULL; sd = &per_cpu(node_domains, i); *sd = SD_NODE_INIT; sd->span = sched_domain_node_span(cpu_to_node(i)); sd->parent = p; cpus_and(sd->span, sd->span, *cpu_map); #endif p = sd; sd = &per_cpu(phys_domains, i); group = cpu_to_phys_group(i); *sd = SD_CPU_INIT; sd->span = nodemask; sd->parent = p; sd->groups = &sched_group_phys[group]; #ifdef CONFIG_SCHED_MC p = sd; sd = &per_cpu(core_domains, i); group = cpu_to_core_group(i); *sd = SD_MC_INIT; sd->span = cpu_coregroup_map(i); cpus_and(sd->span, sd->span, *cpu_map); sd->parent = p; sd->groups = &sched_group_core[group]; #endif #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_map); sd->parent = p; sd->groups = &sched_group_cpus[group]; #endif } #ifdef CONFIG_SCHED_SMT /* Set up CPU (sibling) groups */ for_each_cpu_mask(i, *cpu_map) { cpumask_t this_sibling_map = cpu_sibling_map[i]; cpus_and(this_sibling_map, this_sibling_map, *cpu_map); if (i != first_cpu(this_sibling_map)) continue; init_sched_build_groups(sched_group_cpus, this_sibling_map, &cpu_to_cpu_group); } #endif #ifdef CONFIG_SCHED_MC /* Set up multi-core groups */ for_each_cpu_mask(i, *cpu_map) { cpumask_t this_core_map = cpu_coregroup_map(i); cpus_and(this_core_map, this_core_map, *cpu_map); if (i != first_cpu(this_core_map)) continue; init_sched_build_groups(sched_group_core, this_core_map, &cpu_to_core_group); } #endif /* Set up physical groups */ for (i = 0; i < MAX_NUMNODES; i++) { cpumask_t nodemask = node_to_cpumask(i); cpus_and(nodemask, nodemask, *cpu_map); if (cpus_empty(nodemask)) continue; init_sched_build_groups(sched_group_phys, nodemask, &cpu_to_phys_group); } #ifdef CONFIG_NUMA /* Set up node groups */ if (sched_group_allnodes) init_sched_build_groups(sched_group_allnodes, *cpu_map, &cpu_to_allnodes_group); for (i = 0; i < MAX_NUMNODES; i++) { /* Set up node groups */ struct sched_group *sg, *prev; cpumask_t nodemask = node_to_cpumask(i); cpumask_t domainspan; cpumask_t covered = CPU_MASK_NONE; int j; cpus_and(nodemask, nodemask, *cpu_map); if (cpus_empty(nodemask)) { sched_group_nodes[i] = NULL; continue; } domainspan = sched_domain_node_span(i); cpus_and(domainspan, domainspan, *cpu_map); sg = kmalloc(sizeof(struct sched_group), GFP_KERNEL); sched_group_nodes[i] = sg; for_each_cpu_mask(j, nodemask) { struct sched_domain *sd; sd = &per_cpu(node_domains, j); sd->groups = sg; if (sd->groups == NULL) { /* Turn off balancing if we have no groups */ sd->flags = 0; } } if (!sg) { printk(KERN_WARNING "Can not alloc domain group for node %d\n", i); continue; } sg->cpu_power = 0; sg->cpumask = nodemask; cpus_or(covered, covered, nodemask); prev = sg; for (j = 0; j < MAX_NUMNODES; j++) { cpumask_t tmp, notcovered; int n = (i + j) % MAX_NUMNODES; cpus_complement(notcovered, covered); cpus_and(tmp, notcovered, *cpu_map); cpus_and(tmp, tmp, domainspan); if (cpus_empty(tmp)) break; nodemask = node_to_cpumask(n); cpus_and(tmp, tmp, nodemask); if (cpus_empty(tmp)) continue; sg = kmalloc(sizeof(struct sched_group), GFP_KERNEL); if (!sg) { printk(KERN_WARNING "Can not alloc domain group for node %d\n", j); break; } sg->cpu_power = 0; sg->cpumask = tmp; cpus_or(covered, covered, tmp); prev->next = sg; prev = sg; } prev->next = sched_group_nodes[i]; } #endif /* Calculate CPU power for physical packages and nodes */ for_each_cpu_mask(i, *cpu_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 #ifdef CONFIG_SCHED_MC sd = &per_cpu(core_domains, i); power = SCHED_LOAD_SCALE + (cpus_weight(sd->groups->cpumask)-1) * SCHED_LOAD_SCALE / 10; sd->groups->cpu_power = power; sd = &per_cpu(phys_domains, i); /* * This has to be < 2 * SCHED_LOAD_SCALE * Lets keep it SCHED_LOAD_SCALE, so that * while calculating NUMA group's cpu_power * we can simply do * numa_group->cpu_power += phys_group->cpu_power; * * See "only add power once for each physical pkg" * comment below */ sd->groups->cpu_power = SCHED_LOAD_SCALE; #else 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; #endif } #ifdef CONFIG_NUMA for (i = 0; i < MAX_NUMNODES; i++) init_numa_sched_groups_power(sched_group_nodes[i]); init_numa_sched_groups_power(sched_group_allnodes); #endif /* Attach the domains */ for_each_cpu_mask(i, *cpu_map) { struct sched_domain *sd; #ifdef CONFIG_SCHED_SMT sd = &per_cpu(cpu_domains, i); #elif defined(CONFIG_SCHED_MC) sd = &per_cpu(core_domains, i); #else sd = &per_cpu(phys_domains, i); #endif cpu_attach_domain(sd, i); } /* * Tune cache-hot values: */ calibrate_migration_costs(cpu_map); } /* * Set up scheduler domains and groups. Callers must hold the hotplug lock. */ static void arch_init_sched_domains(const cpumask_t *cpu_map) { 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_andnot(cpu_default_map, *cpu_map, cpu_isolated_map); build_sched_domains(&cpu_default_map); } static void arch_destroy_sched_domains(const cpumask_t *cpu_map) { #ifdef CONFIG_NUMA int i; int cpu; for_each_cpu_mask(cpu, *cpu_map) { struct sched_group *sched_group_allnodes = sched_group_allnodes_bycpu[cpu]; struct sched_group **sched_group_nodes = sched_group_nodes_bycpu[cpu]; if (sched_group_allnodes) { kfree(sched_group_allnodes); sched_group_allnodes_bycpu[cpu] = NULL; } if (!sched_group_nodes) continue; for (i = 0; i < MAX_NUMNODES; i++) { cpumask_t nodemask = node_to_cpumask(i); struct sched_group *oldsg, *sg = sched_group_nodes[i]; cpus_and(nodemask, nodemask, *cpu_map); if (cpus_empty(nodemask)) continue; if (sg == NULL) continue; sg = sg->next; next_sg: oldsg = sg; sg = sg->next; kfree(oldsg); if (oldsg != sched_group_nodes[i]) goto next_sg; } kfree(sched_group_nodes); sched_group_nodes_bycpu[cpu] = NULL; } #endif } /* * Detach sched domains from a group of cpus specified in cpu_map * These cpus will now be attached to the NULL domain */ static void detach_destroy_domains(const cpumask_t *cpu_map) { int i; for_each_cpu_mask(i, *cpu_map) cpu_attach_domain(NULL, i); synchronize_sched(); arch_destroy_sched_domains(cpu_map); } /* * Partition sched domains as specified by the cpumasks below. * This attaches all cpus from the cpumasks to the NULL domain, * waits for a RCU quiescent period, recalculates sched * domain information and then attaches them back to the * correct sched domains * Call with hotplug lock held */ void partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2) { cpumask_t change_map; cpus_and(*partition1, *partition1, cpu_online_map); cpus_and(*partition2, *partition2, cpu_online_map); cpus_or(change_map, *partition1, *partition2); /* Detach sched domains from all of the affected cpus */ detach_destroy_domains(&change_map); if (!cpus_empty(*partition1)) build_sched_domains(partition1); if (!cpus_empty(*partition2)) build_sched_domains(partition2); } #ifdef CONFIG_HOTPLUG_CPU /* * Force a reinitialization of the sched domains hierarchy. The domains * and groups cannot be updated in place without racing with the balancing * code, so we temporarily attach all running cpus to the NULL domain * which will prevent rebalancing while the sched domains are recalculated. */ static int update_sched_domains(struct notifier_block *nfb, unsigned long action, void *hcpu) { switch (action) { case CPU_UP_PREPARE: case CPU_DOWN_PREPARE: detach_destroy_domains(&cpu_online_map); return NOTIFY_OK; case CPU_UP_CANCELED: case CPU_DOWN_FAILED: case CPU_ONLINE: case CPU_DEAD: /* * Fall through and re-initialise the domains. */ break; default: return NOTIFY_DONE; } /* The hotplug lock is already held by cpu_up/cpu_down */ arch_init_sched_domains(&cpu_online_map); return NOTIFY_OK; } #endif void __init sched_init_smp(void) { lock_cpu_hotplug(); arch_init_sched_domains(&cpu_online_map); unlock_cpu_hotplug(); /* XXX: Theoretical race here - CPU may be hotplugged now */ hotcpu_notifier(update_sched_domains, 0); } #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; for_each_possible_cpu(i) { prio_array_t *array; rq = cpu_rq(i); spin_lock_init(&rq->lock); rq->nr_running = 0; rq->active = rq->arrays; rq->expired = rq->arrays + 1; rq->best_expired_prio = MAX_PRIO; #ifdef CONFIG_SMP rq->sd = NULL; for (j = 1; j < 3; j++) rq->cpu_load[j] = 0; rq->active_balance = 0; rq->push_cpu = 0; rq->migration_thread = NULL; INIT_LIST_HEAD(&rq->migration_queue); rq->cpu = i; #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 && !oops_in_progress) { if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) return; prev_jiffy = jiffies; printk(KERN_ERR "BUG: 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 #ifdef CONFIG_MAGIC_SYSRQ void normalize_rt_tasks(void) { struct task_struct *p; prio_array_t *array; unsigned long flags; runqueue_t *rq; read_lock_irq(&tasklist_lock); for_each_process (p) { if (!rt_task(p)) continue; rq = task_rq_lock(p, &flags); array = p->array; if (array) deactivate_task(p, task_rq(p)); __setscheduler(p, SCHED_NORMAL, 0); if (array) { __activate_task(p, task_rq(p)); resched_task(rq->curr); } task_rq_unlock(rq, &flags); } read_unlock_irq(&tasklist_lock); } #endif /* CONFIG_MAGIC_SYSRQ */ #ifdef CONFIG_IA64 /* * These functions are only useful for the IA64 MCA handling. * * They can only be called when the whole system has been * stopped - every CPU needs to be quiescent, and no scheduling * activity can take place. Using them for anything else would * be a serious bug, and as a result, they aren't even visible * under any other configuration. */ /** * curr_task - return the current task for a given cpu. * @cpu: the processor in question. * * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED! */ task_t *curr_task(int cpu) { return cpu_curr(cpu); } /** * set_curr_task - set the current task for a given cpu. * @cpu: the processor in question. * @p: the task pointer to set. * * Description: This function must only be used when non-maskable interrupts * are serviced on a separate stack. It allows the architecture to switch the * notion of the current task on a cpu in a non-blocking manner. This function * must be called with all CPU's synchronized, and interrupts disabled, the * and caller must save the original value of the current task (see * curr_task() above) and restore that value before reenabling interrupts and * re-starting the system. * * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED! */ void set_curr_task(int cpu, task_t *p) { cpu_curr(cpu) = p; } #endif