/* * linux/kernel/sched.c * * Kernel scheduler and related syscalls * * Copyright (C) 1991, 1992 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 * 1998-12-28 Implemented better SMP scheduling by Ingo Molnar */ /* * 'sched.c' is the main kernel file. It contains scheduling primitives * (sleep_on, wakeup, schedule etc) as well as a number of simple system * call functions (type getpid()), which just extract a field from * current-task */ #include <linux/config.h> #include <linux/mm.h> #include <linux/init.h> #include <linux/smp_lock.h> #include <linux/nmi.h> #include <linux/interrupt.h> #include <linux/kernel_stat.h> #include <linux/completion.h> #include <linux/prefetch.h> #include <linux/compiler.h> #include <asm/uaccess.h> #include <asm/mmu_context.h> extern void timer_bh(void); extern void tqueue_bh(void); extern void immediate_bh(void); /* * scheduler variables */ unsigned securebits = SECUREBITS_DEFAULT; /* systemwide security settings */ extern void mem_use(void); /* * Scheduling quanta. * * NOTE! The unix "nice" value influences how long a process * gets. The nice value ranges from -20 to +19, where a -20 * is a "high-priority" task, and a "+10" is a low-priority * task. * * We want the time-slice to be around 50ms or so, so this * calculation depends on the value of HZ. */ #if HZ < 200 #define TICK_SCALE(x) ((x) >> 2) #elif HZ < 400 #define TICK_SCALE(x) ((x) >> 1) #elif HZ < 800 #define TICK_SCALE(x) (x) #elif HZ < 1600 #define TICK_SCALE(x) ((x) << 1) #else #define TICK_SCALE(x) ((x) << 2) #endif #define NICE_TO_TICKS(nice) (TICK_SCALE(20-(nice))+1) /* * Init task must be ok at boot for the ix86 as we will check its signals * via the SMP irq return path. */ struct task_struct * init_tasks[NR_CPUS] = {&init_task, }; /* * The tasklist_lock protects the linked list of processes. * * The runqueue_lock locks the parts that actually access * and change the run-queues, and have to be interrupt-safe. * * If both locks are to be concurrently held, the runqueue_lock * nests inside the tasklist_lock. * * task->alloc_lock nests inside tasklist_lock. */ spinlock_t runqueue_lock __cacheline_aligned = SPIN_LOCK_UNLOCKED; /* inner */ rwlock_t tasklist_lock __cacheline_aligned = RW_LOCK_UNLOCKED; /* outer */ static LIST_HEAD(runqueue_head); /* * We align per-CPU scheduling data on cacheline boundaries, * to prevent cacheline ping-pong. */ static union { struct schedule_data { struct task_struct * curr; cycles_t last_schedule; } schedule_data; char __pad [SMP_CACHE_BYTES]; } aligned_data [NR_CPUS] __cacheline_aligned = { {{&init_task,0}}}; #define cpu_curr(cpu) aligned_data[(cpu)].schedule_data.curr #define last_schedule(cpu) aligned_data[(cpu)].schedule_data.last_schedule struct kernel_stat kstat; extern struct task_struct *child_reaper; #ifdef CONFIG_SMP #define idle_task(cpu) (init_tasks[cpu_number_map(cpu)]) #define can_schedule(p,cpu) / ((p)->cpus_runnable & (p)->cpus_allowed & (1UL << cpu)) #else #define idle_task(cpu) (&init_task) #define can_schedule(p,cpu) (1) #endif void scheduling_functions_start_here(void) { } /* * This is the function that decides how desirable a process is.. * You can weigh different processes against each other depending * on what CPU they've run on lately etc to try to handle cache * and TLB miss penalties. * * Return values: * -1000: never select this * 0: out of time, recalculate counters (but it might still be * selected) * +ve: "goodness" value (the larger, the better) * +1000: realtime process, select this. */ static inline int goodness(struct task_struct * p, int this_cpu, struct mm_struct *this_mm) { int weight; /* * select the current process after every other * runnable process, but before the idle thread. * Also, dont trigger a counter recalculation. */ weight = -1; if (p->policy & SCHED_YIELD) goto out; /* * Non-RT process - normal case first. */ if (p->policy == SCHED_OTHER) { /* * Give the process a first-approximation goodness value * according to the number of clock-ticks it has left. * * Don't do any other calculations if the time slice is * over.. */ weight = p->counter; if (!weight) goto out; #ifdef CONFIG_SMP /* Give a largish advantage to the same processor... */ /* (this is equivalent to penalizing other processors) */ if (p->processor == this_cpu) weight += PROC_CHANGE_PENALTY; #endif /* .. and a slight advantage to the current MM */ if (p->mm == this_mm || !p->mm) weight += 1; weight += 20 - p->nice; goto out; } /* * Realtime process, select the first one on the * runqueue (taking priorities within processes * into account). */ weight = 1000 + p->rt_priority; out: return weight; } /* * the 'goodness value' of replacing a process on a given CPU. * positive value means 'replace', zero or negative means 'dont'. */ static inline int preemption_goodness(struct task_struct * prev, struct task_struct * p, int cpu) { return goodness(p, cpu, prev->active_mm) - goodness(prev, cpu, prev->active_mm); } /* * This is ugly, but reschedule_idle() is very timing-critical. * We are called with the runqueue spinlock held and we must * not claim the tasklist_lock. */ static FASTCALL(void reschedule_idle(struct task_struct * p)); static void fastcall reschedule_idle(struct task_struct * p) { #ifdef CONFIG_SMP int this_cpu = smp_processor_id(); struct task_struct *tsk, *target_tsk; int cpu, best_cpu, i, max_prio; cycles_t oldest_idle; /* * shortcut if the woken up task's last CPU is * idle now. */ best_cpu = p->processor; if (can_schedule(p, best_cpu)) { tsk = idle_task(best_cpu); if (cpu_curr(best_cpu) == tsk) { int need_resched; send_now_idle: /* * If need_resched == -1 then we can skip sending * the IPI altogether, tsk->need_resched is * actively watched by the idle thread. */ need_resched = tsk->need_resched; tsk->need_resched = 1; if ((best_cpu != this_cpu) && !need_resched) smp_send_reschedule(best_cpu); return; } } /* * We know that the preferred CPU has a cache-affine current * process, lets try to find a new idle CPU for the woken-up * process. Select the least recently active idle CPU. (that * one will have the least active cache context.) Also find * the executing process which has the least priority. */ oldest_idle = (cycles_t) -1; target_tsk = NULL; max_prio = 0; for (i = 0; i < smp_num_cpus; i++) { cpu = cpu_logical_map(i); if (!can_schedule(p, cpu)) continue; tsk = cpu_curr(cpu); /* * We use the first available idle CPU. This creates * a priority list between idle CPUs, but this is not * a problem. */ if (tsk == idle_task(cpu)) { #if defined(__i386__) && defined(CONFIG_SMP) /* * Check if two siblings are idle in the same * physical package. Use them if found. */ if (smp_num_siblings == 2) { if (cpu_curr(cpu_sibling_map[cpu]) == idle_task(cpu_sibling_map[cpu])) { oldest_idle = last_schedule(cpu); target_tsk = tsk; break; } } #endif if (last_schedule(cpu) < oldest_idle) { oldest_idle = last_schedule(cpu); target_tsk = tsk; } } else { if (oldest_idle == (cycles_t)-1) { int prio = preemption_goodness(tsk, p, cpu); if (prio > max_prio) { max_prio = prio; target_tsk = tsk; } } } } tsk = target_tsk; if (tsk) { if (oldest_idle != (cycles_t)-1) { best_cpu = tsk->processor; goto send_now_idle; } tsk->need_resched = 1; if (tsk->processor != this_cpu) smp_send_reschedule(tsk->processor); } return; #else /* UP */ int this_cpu = smp_processor_id(); struct task_struct *tsk; tsk = cpu_curr(this_cpu); if (preemption_goodness(tsk, p, this_cpu) > 0) tsk->need_resched = 1; #endif } /* * Careful! * * This has to add the process to the _end_ of the * run-queue, not the beginning. The goodness value will * determine whether this process will run next. This is * important to get SCHED_FIFO and SCHED_RR right, where * a process that is either pre-empted or its time slice * has expired, should be moved to the tail of the run * queue for its priority - Bhavesh Davda */ static inline void add_to_runqueue(struct task_struct * p) { list_add_tail(&p->run_list, &runqueue_head); nr_running++; } static inline void move_last_runqueue(struct task_struct * p) { list_del(&p->run_list); list_add_tail(&p->run_list, &runqueue_head); } /* * Wake up a process. Put it on the run-queue if it's not * already there. The "current" process 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. */ static inline int try_to_wake_up(struct task_struct * p, int synchronous) { unsigned long flags; int success = 0; /* * We want the common case fall through straight, thus the goto. */ spin_lock_irqsave(&runqueue_lock, flags); p->state = TASK_RUNNING; if (task_on_runqueue(p)) goto out; add_to_runqueue(p); if (!synchronous || !(p->cpus_allowed & (1UL << smp_processor_id()))) reschedule_idle(p); success = 1; out: spin_unlock_irqrestore(&runqueue_lock, flags); return success; } inline int fastcall wake_up_process(struct task_struct * p) { return try_to_wake_up(p, 0); } static void process_timeout(unsigned long __data) { struct task_struct * p = (struct task_struct *) __data; wake_up_process(p); } /** * schedule_timeout - sleep until timeout * @timeout: timeout value in jiffies * * Make the current task sleep until @timeout jiffies have * elapsed. The routine will return immediately unless * the current task state has been set (see set_current_state()). * * You can set the task state as follows - * * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to * pass before the routine returns. The routine will return 0 * * %TASK_INTERRUPTIBLE - the routine may return early if a signal is * delivered to the current task. In this case the remaining time * in jiffies will be returned, or 0 if the timer expired in time * * The current task state is guaranteed to be TASK_RUNNING when this * routine returns. * * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule * the CPU away without a bound on the timeout. In this case the return * value will be %MAX_SCHEDULE_TIMEOUT. * * In all cases the return value is guaranteed to be non-negative. */ signed long fastcall schedule_timeout(signed long timeout) { struct timer_list timer; unsigned long expire; switch (timeout) { case MAX_SCHEDULE_TIMEOUT: /* * These two special cases are useful to be comfortable * in the caller. Nothing more. We could take * MAX_SCHEDULE_TIMEOUT from one of the negative value * but I' d like to return a valid offset (>=0) to allow * the caller to do everything it want with the retval. */ schedule(); goto out; default: /* * Another bit of PARANOID. Note that the retval will be * 0 since no piece of kernel is supposed to do a check * for a negative retval of schedule_timeout() (since it * should never happens anyway). You just have the printk() * that will tell you if something is gone wrong and where. */ if (timeout < 0) { printk(KERN_ERR "schedule_timeout: wrong timeout " "value %lx from %p/n", timeout, __builtin_return_address(0)); current->state = TASK_RUNNING; goto out; } } expire = timeout + jiffies; init_timer(&timer); timer.expires = expire; timer.data = (unsigned long) current; timer.function = process_timeout; add_timer(&timer); schedule(); del_timer_sync(&timer); timeout = expire - jiffies; out: return timeout < 0 ? 0 : timeout; } /* * schedule_tail() is getting called from the fork return path. This * cleans up all remaining scheduler things, without impacting the * common case. */ static inline void __schedule_tail(struct task_struct *prev) { #ifdef CONFIG_SMP int policy; /* * prev->policy can be written from here only before `prev' * can be scheduled (before setting prev->cpus_runnable to ~0UL). * Of course it must also be read before allowing prev * to be rescheduled, but since the write depends on the read * to complete, wmb() is enough. (the spin_lock() acquired * before setting cpus_runnable is not enough because the spin_lock() * common code semantics allows code outside the critical section * to enter inside the critical section) */ policy = prev->policy; prev->policy = policy & ~SCHED_YIELD; wmb(); /* * fast path falls through. We have to clear cpus_runnable before * checking prev->state to avoid a wakeup race. Protect against * the task exiting early. */ task_lock(prev); task_release_cpu(prev); mb(); if (prev->state == TASK_RUNNING) goto needs_resched; out_unlock: task_unlock(prev); /* Synchronise here with release_task() if prev is TASK_ZOMBIE */ return; /* * Slow path - we 'push' the previous process and * reschedule_idle() will attempt to find a new * processor for it. (but it might preempt the * current process as well.) We must take the runqueue * lock and re-check prev->state to be correct. It might * still happen that this process has a preemption * 'in progress' already - but this is not a problem and * might happen in other circumstances as well. */ needs_resched: { unsigned long flags; /* * Avoid taking the runqueue lock in cases where * no preemption-check is necessery: */ if ((prev == idle_task(smp_processor_id())) || (policy & SCHED_YIELD)) goto out_unlock; spin_lock_irqsave(&runqueue_lock, flags); if ((prev->state == TASK_RUNNING) && !task_has_cpu(prev)) reschedule_idle(prev); spin_unlock_irqrestore(&runqueue_lock, flags); goto out_unlock; } #else prev->policy &= ~SCHED_YIELD; #endif /* CONFIG_SMP */ } asmlinkage void schedule_tail(struct task_struct *prev) { __schedule_tail(prev); } /* * 'schedule()' is the scheduler function. It's a very simple and nice * scheduler: it's not perfect, but certainly works for most things. * * The goto is "interesting". * * NOTE!! Task 0 is the 'idle' task, which gets called when no other * tasks can run. It can not be killed, and it cannot sleep. The 'state' * information in task[0] is never used. */ asmlinkage void schedule(void) { struct schedule_data * sched_data; struct task_struct *prev, *next, *p; struct list_head *tmp; int this_cpu, c; spin_lock_prefetch(&runqueue_lock); BUG_ON(!current->active_mm); need_resched_back: prev = current; this_cpu = prev->processor; if (unlikely(in_interrupt())) { printk("Scheduling in interrupt/n"); BUG(); } release_kernel_lock(prev, this_cpu); /* * 'sched_data' is protected by the fact that we can run * only one process per CPU. */ sched_data = & aligned_data[this_cpu].schedule_data; spin_lock_irq(&runqueue_lock); /* move an exhausted RR process to be last.. */ if (unlikely(prev->policy == SCHED_RR)) if (!prev->counter) { prev->counter = NICE_TO_TICKS(prev->nice); move_last_runqueue(prev); } switch (prev->state) { case TASK_INTERRUPTIBLE: if (signal_pending(prev)) { prev->state = TASK_RUNNING; break; } default: del_from_runqueue(prev); case TASK_RUNNING:; } prev->need_resched = 0; /* * this is the scheduler proper: */ repeat_schedule: /* * Default process to select.. */ next = idle_task(this_cpu); c = -1000; list_for_each(tmp, &runqueue_head) { p = list_entry(tmp, struct task_struct, run_list); if (can_schedule(p, this_cpu)) { int weight = goodness(p, this_cpu, prev->active_mm); if (weight > c) c = weight, next = p; } } /* Do we need to re-calculate counters? */ if (unlikely(!c)) { struct task_struct *p; spin_unlock_irq(&runqueue_lock); read_lock(&tasklist_lock); for_each_task(p) p->counter = (p->counter >> 1) + NICE_TO_TICKS(p->nice); read_unlock(&tasklist_lock); spin_lock_irq(&runqueue_lock); goto repeat_schedule; } /* * from this point on nothing can prevent us from * switching to the next task, save this fact in * sched_data. */ sched_data->curr = next; task_set_cpu(next, this_cpu); spin_unlock_irq(&runqueue_lock); if (unlikely(prev == next)) { /* We won't go through the normal tail, so do this by hand */ prev->policy &= ~SCHED_YIELD; goto same_process; } #ifdef CONFIG_SMP /* * maintain the per-process 'last schedule' value. * (this has to be recalculated even if we reschedule to * the same process) Currently this is only used on SMP, * and it's approximate, so we do not have to maintain * it while holding the runqueue spinlock. */ sched_data->last_schedule = get_cycles(); /* * We drop the scheduler lock early (it's a global spinlock), * thus we have to lock the previous process from getting * rescheduled during switch_to(). */ #endif /* CONFIG_SMP */ kstat.context_swtch++; /* * there are 3 processes which are affected by a context switch: * * prev == .... ==> (last => next) * * It's the 'much more previous' 'prev' that is on next's stack, * but prev is set to (the just run) 'last' process by switch_to(). * This might sound slightly confusing but makes tons of sense. */ prepare_to_switch(); { struct mm_struct *mm = next->mm; struct mm_struct *oldmm = prev->active_mm; if (!mm) { BUG_ON(next->active_mm); next->active_mm = oldmm; atomic_inc(&oldmm->mm_count); enter_lazy_tlb(oldmm, next, this_cpu); } else { BUG_ON(next->active_mm != mm); switch_mm(oldmm, mm, next, this_cpu); } if (!prev->mm) { prev->active_mm = NULL; mmdrop(oldmm); } } /* * This just switches the register state and the * stack. */ switch_to(prev, next, prev); __schedule_tail(prev); same_process: reacquire_kernel_lock(current); if (current->need_resched) goto need_resched_back; return; } /* * 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 contonuing to scan the queue. */ static inline void __wake_up_common (wait_queue_head_t *q, unsigned int mode, int nr_exclusive, const int sync) { struct list_head *tmp; struct task_struct *p; CHECK_MAGIC_WQHEAD(q); WQ_CHECK_LIST_HEAD(&q->task_list); list_for_each(tmp,&q->task_list) { unsigned int state; wait_queue_t *curr = list_entry(tmp, wait_queue_t, task_list); CHECK_MAGIC(curr->__magic); p = curr->task; state = p->state; if (state & mode) { WQ_NOTE_WAKER(curr); if (try_to_wake_up(p, sync) && (curr->flags&WQ_FLAG_EXCLUSIVE) && !--nr_exclusive) break; } } } void fastcall __wake_up(wait_queue_head_t *q, unsigned int mode, int nr) { if (q) { unsigned long flags; wq_read_lock_irqsave(&q->lock, flags); __wake_up_common(q, mode, nr, 0); wq_read_unlock_irqrestore(&q->lock, flags); } } void fastcall __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr) { if (q) { unsigned long flags; wq_read_lock_irqsave(&q->lock, flags); __wake_up_common(q, mode, nr, 1); wq_read_unlock_irqrestore(&q->lock, flags); } } 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); spin_unlock_irqrestore(&x->wait.lock, flags); } void fastcall wait_for_completion(struct completion *x) { 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); } #define SLEEP_ON_VAR / unsigned long flags; / wait_queue_t wait; / init_waitqueue_entry(&wait, current); #define SLEEP_ON_HEAD / wq_write_lock_irqsave(&q->lock,flags); / __add_wait_queue(q, &wait); / wq_write_unlock(&q->lock); #define SLEEP_ON_TAIL / wq_write_lock_irq(&q->lock); / __remove_wait_queue(q, &wait); / wq_write_unlock_irqrestore(&q->lock,flags); void fastcall interruptible_sleep_on(wait_queue_head_t *q) { SLEEP_ON_VAR current->state = TASK_INTERRUPTIBLE; SLEEP_ON_HEAD schedule(); SLEEP_ON_TAIL } long fastcall 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; } void fastcall sleep_on(wait_queue_head_t *q) { SLEEP_ON_VAR current->state = TASK_UNINTERRUPTIBLE; SLEEP_ON_HEAD schedule(); SLEEP_ON_TAIL } long fastcall 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; } void scheduling_functions_end_here(void) { } #if CONFIG_SMP /** * set_cpus_allowed() - change a given task's processor affinity * @p: task to bind * @new_mask: bitmask of allowed processors * * Upon return, the task is running on a legal processor. Note the caller * must have a valid reference to the task: it must not exit() prematurely. * This call can sleep; do not hold locks on call. */ void set_cpus_allowed(struct task_struct *p, unsigned long new_mask) { new_mask &= cpu_online_map; BUG_ON(!new_mask); p->cpus_allowed = new_mask; /* * If the task is on a no-longer-allowed processor, we need to move * it. If the task is not current, then set need_resched and send * its processor an IPI to reschedule. */ if (!(p->cpus_runnable & p->cpus_allowed)) { if (p != current) { p->need_resched = 1; smp_send_reschedule(p->processor); } /* * Wait until we are on a legal processor. If the task is * current, then we should be on a legal processor the next * time we reschedule. Otherwise, we need to wait for the IPI. */ while (!(p->cpus_runnable & p->cpus_allowed)) schedule(); } } #endif /* CONFIG_SMP */ #ifndef __alpha__ /* * This has been replaced by sys_setpriority. Maybe it should be * moved into the arch dependent tree for those ports that require * it for backward compatibility? */ asmlinkage long sys_nice(int increment) { long newprio; /* * Setpriority might change our priority at the same moment. * We don't have to worry. Conceptually one call occurs first * and we have a single winner. */ if (increment < 0) { if (!capable(CAP_SYS_NICE)) return -EPERM; if (increment < -40) increment = -40; } if (increment > 40) increment = 40; newprio = current->nice + increment; if (newprio < -20) newprio = -20; if (newprio > 19) newprio = 19; current->nice = newprio; return 0; } #endif static inline struct task_struct *find_process_by_pid(pid_t pid) { struct task_struct *tsk = current; if (pid) tsk = find_task_by_pid(pid); return tsk; } static int setscheduler(pid_t pid, int policy, struct sched_param *param) { struct sched_param lp; struct task_struct *p; int retval; retval = -EINVAL; if (!param || pid < 0) goto out_nounlock; retval = -EFAULT; if (copy_from_user(&lp, param, sizeof(struct sched_param))) goto out_nounlock; /* * We play safe to avoid deadlocks. */ read_lock_irq(&tasklist_lock); spin_lock(&runqueue_lock); p = find_process_by_pid(pid); retval = -ESRCH; if (!p) goto out_unlock; if (policy < 0) policy = p->policy; else { retval = -EINVAL; if (policy != SCHED_FIFO && policy != SCHED_RR && policy != SCHED_OTHER) goto out_unlock; } /* * Valid priorities for SCHED_FIFO and SCHED_RR are 1..99, valid * priority for SCHED_OTHER is 0. */ retval = -EINVAL; if (lp.sched_priority < 0 || lp.sched_priority > 99) goto out_unlock; if ((policy == SCHED_OTHER) != (lp.sched_priority == 0)) goto out_unlock; retval = -EPERM; if ((policy == SCHED_FIFO || policy == SCHED_RR) && !capable(CAP_SYS_NICE)) goto out_unlock; if ((current->euid != p->euid) && (current->euid != p->uid) && !capable(CAP_SYS_NICE)) goto out_unlock; retval = 0; p->policy = policy; p->rt_priority = lp.sched_priority; current->need_resched = 1; out_unlock: spin_unlock(&runqueue_lock); read_unlock_irq(&tasklist_lock); out_nounlock: return retval; } asmlinkage long sys_sched_setscheduler(pid_t pid, int policy, struct sched_param *param) { return setscheduler(pid, policy, param); } asmlinkage long sys_sched_setparam(pid_t pid, struct sched_param *param) { return setscheduler(pid, -1, param); } asmlinkage long sys_sched_getscheduler(pid_t pid) { struct task_struct *p; int retval; retval = -EINVAL; if (pid < 0) goto out_nounlock; retval = -ESRCH; read_lock(&tasklist_lock); p = find_process_by_pid(pid); if (p) retval = p->policy & ~SCHED_YIELD; read_unlock(&tasklist_lock); out_nounlock: return retval; } asmlinkage long sys_sched_getparam(pid_t pid, struct sched_param *param) { struct task_struct *p; struct sched_param lp; int retval; retval = -EINVAL; if (!param || pid < 0) goto out_nounlock; read_lock(&tasklist_lock); p = find_process_by_pid(pid); retval = -ESRCH; if (!p) 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; } asmlinkage long sys_sched_yield(void) { /* * Trick. sched_yield() first counts the number of truly * 'pending' runnable processes, then returns if it's * only the current processes. (This test does not have * to be atomic.) In threaded applications this optimization * gets triggered quite often. */ int nr_pending = nr_running; #if CONFIG_SMP int i; // Subtract non-idle processes running on other CPUs. for (i = 0; i < smp_num_cpus; i++) { int cpu = cpu_logical_map(i); if (aligned_data[cpu].schedule_data.curr != idle_task(cpu)) nr_pending--; } #else // on UP this process is on the runqueue as well nr_pending--; #endif if (nr_pending) { /* * This process can only be rescheduled by us, * so this is safe without any locking. */ if (current->policy == SCHED_OTHER) current->policy |= SCHED_YIELD; current->need_resched = 1; spin_lock_irq(&runqueue_lock); move_last_runqueue(current); spin_unlock_irq(&runqueue_lock); } return 0; } /** * 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 yield(void) { set_current_state(TASK_RUNNING); sys_sched_yield(); schedule(); } void __cond_resched(void) { set_current_state(TASK_RUNNING); schedule(); } asmlinkage long sys_sched_get_priority_max(int policy) { int ret = -EINVAL; switch (policy) { case SCHED_FIFO: case SCHED_RR: ret = 99; break; case SCHED_OTHER: ret = 0; break; } return ret; } 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_OTHER: ret = 0; } return ret; } asmlinkage long sys_sched_rr_get_interval(pid_t pid, struct timespec *interval) { struct timespec t; struct task_struct *p; int retval = -EINVAL; if (pid < 0) goto out_nounlock; retval = -ESRCH; read_lock(&tasklist_lock); p = find_process_by_pid(pid); if (p) jiffies_to_timespec(p->policy & SCHED_FIFO ? 0 : NICE_TO_TICKS(p->nice), &t); read_unlock(&tasklist_lock); if (p) retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0; out_nounlock: return retval; } static void show_task(struct task_struct * p) { unsigned long free = 0; int state; static const char * stat_nam[] = { "R", "S", "D", "Z", "T", "W" }; printk("%-13.13s ", p->comm); state = p->state ? ffz(~p->state) + 1 : 0; if (((unsigned) state) < sizeof(stat_nam)/sizeof(char *)) printk(stat_nam[state]); else printk(" "); #if (BITS_PER_LONG == 32) if (p == current) printk(" current "); else printk(" %08lX ", thread_saved_pc(&p->thread)); #else if (p == current) printk(" current task "); else printk(" %016lx ", thread_saved_pc(&p->thread)); #endif { unsigned long * n = (unsigned long *) (p+1); while (!*n) n++; free = (unsigned long) n - (unsigned long)(p+1); } printk("%5lu %5d %6d ", free, p->pid, p->p_pptr->pid); if (p->p_cptr) printk("%5d ", p->p_cptr->pid); else printk(" "); if (p->p_ysptr) printk("%7d", p->p_ysptr->pid); else printk(" "); if (p->p_osptr) printk(" %5d", p->p_osptr->pid); else printk(" "); if (!p->mm) printk(" (L-TLB)/n"); else printk(" (NOTLB)/n"); { extern void show_trace_task(struct task_struct *tsk); show_trace_task(p); } } char * render_sigset_t(sigset_t *set, char *buffer) { int i = _NSIG, x; do { i -= 4, x = 0; if (sigismember(set, i+1)) x |= 1; if (sigismember(set, i+2)) x |= 2; if (sigismember(set, i+3)) x |= 4; if (sigismember(set, i+4)) x |= 8; *buffer++ = (x < 10 ? '0' : 'a' - 10) + x; } while (i >= 4); *buffer = 0; return buffer; } void show_state(void) { struct task_struct *p; #if (BITS_PER_LONG == 32) printk("/n" " free sibling/n"); printk(" task PC stack pid father child younger older/n"); #else printk("/n" " free sibling/n"); printk(" task PC stack pid father child younger older/n"); #endif read_lock(&tasklist_lock); for_each_task(p) { /* * reset the NMI-timeout, listing all files on a slow * console might take alot of time: */ touch_nmi_watchdog(); show_task(p); } read_unlock(&tasklist_lock); } /** * reparent_to_init() - Reparent the calling kernel thread to the init task. * * If a kernel thread is launched as a result of a system call, or if * it ever exits, it should generally reparent itself to init so that * it is correctly cleaned up on exit. * * The various task state such as scheduling policy and priority may have * been inherited fro a user process, so we reset them to sane values here. * * NOTE that reparent_to_init() gives the caller full capabilities. */ void reparent_to_init(void) { struct task_struct *this_task = current; write_lock_irq(&tasklist_lock); /* Reparent to init */ REMOVE_LINKS(this_task); this_task->p_pptr = child_reaper; this_task->p_opptr = child_reaper; SET_LINKS(this_task); /* Set the exit signal to SIGCHLD so we signal init on exit */ this_task->exit_signal = SIGCHLD; /* We also take the runqueue_lock while altering task fields * which affect scheduling decisions */ spin_lock(&runqueue_lock); this_task->ptrace = 0; this_task->nice = DEF_NICE; this_task->policy = SCHED_OTHER; /* cpus_allowed? */ /* rt_priority? */ /* signals? */ this_task->cap_effective = CAP_INIT_EFF_SET; this_task->cap_inheritable = CAP_INIT_INH_SET; this_task->cap_permitted = CAP_FULL_SET; this_task->keep_capabilities = 0; memcpy(this_task->rlim, init_task.rlim, sizeof(*(this_task->rlim))); switch_uid(INIT_USER); spin_unlock(&runqueue_lock); write_unlock_irq(&tasklist_lock); } /* * Put all the gunge required to become a kernel thread without * attached user resources in one place where it belongs. */ void daemonize(void) { struct fs_struct *fs; /* * If we were started as result of loading a module, close all of the * user space pages. We don't need them, and if we didn't close them * they would be locked into memory. */ exit_mm(current); current->session = 1; current->pgrp = 1; current->tty = NULL; /* Become as one with the init task */ exit_fs(current); /* current->fs->count--; */ fs = init_task.fs; current->fs = fs; atomic_inc(&fs->count); exit_files(current); current->files = init_task.files; atomic_inc(¤t->files->count); } extern unsigned long wait_init_idle; void __init init_idle(void) { struct schedule_data * sched_data; sched_data = &aligned_data[smp_processor_id()].schedule_data; if (current != &init_task && task_on_runqueue(current)) { printk("UGH! (%d:%d) was on the runqueue, removing./n", smp_processor_id(), current->pid); del_from_runqueue(current); } sched_data->curr = current; sched_data->last_schedule = get_cycles(); clear_bit(current->processor, &wait_init_idle); } extern void init_timervecs (void); void __init sched_init(void) { /* * We have to do a little magic to get the first * process right in SMP mode. */ int cpu = smp_processor_id(); int nr; init_task.processor = cpu; for(nr = 0; nr < PIDHASH_SZ; nr++) pidhash[nr] = NULL; init_timervecs(); init_bh(TIMER_BH, timer_bh); init_bh(TQUEUE_BH, tqueue_bh); init_bh(IMMEDIATE_BH, immediate_bh); /* * The boot idle thread does lazy MMU switching as well: */ atomic_inc(&init_mm.mm_count); enter_lazy_tlb(&init_mm, current, cpu); }
