/*
* 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);
}
