static void demo_task_new(struct task_struct *tsk, int on_runqueue,
int is_running)
{
/* We'll use this to store IRQ flags. */
unsigned long flags;
struct demo_cpu_state *state = cpu_state_for(get_partition(tsk));
lt_t now;
TRACE_TASK(tsk, "is a new RT task %llu (on runqueue:%d, running:%d)\n",
litmus_clock(), on_runqueue, is_running);
/* Acquire the lock protecting the state and disable interrupts. */
raw_spin_lock_irqsave(&state->local_queues.ready_lock, flags);
now = litmus_clock();
/* Release the first job now. */
release_at(tsk, now);
if (is_running) {
/* If tsk is running, then no other task can be running
* on the local CPU. */
BUG_ON(state->scheduled != NULL);
state->scheduled = tsk;
} else if (on_runqueue) {
demo_requeue(tsk, state);
}
if (edf_preemption_needed(&state->local_queues, state->scheduled))
preempt_if_preemptable(state->scheduled, state->cpu);
raw_spin_unlock_irqrestore(&state->local_queues.ready_lock, flags);
}
/* Called when the state of tsk changes back to TASK_RUNNING.
* We need to requeue the task.
*
* NOTE: If a sporadic task is suspended for a long time,
* this might actually be an event-driven release of a new job.
*/
static void demo_task_resume(struct task_struct *tsk)
{
unsigned long flags;
struct demo_cpu_state *state = cpu_state_for(get_partition(tsk));
lt_t now;
TRACE_TASK(tsk, "wake_up at %llu\n", litmus_clock());
raw_spin_lock_irqsave(&state->local_queues.ready_lock, flags);
now = litmus_clock();
if (is_sporadic(tsk) && is_tardy(tsk, now)) {
/* This sporadic task was gone for a "long" time and woke up past
* its deadline. Give it a new budget by triggering a job
* release. */
release_at(tsk, now);
}
/* This check is required to avoid races with tasks that resume before
* the scheduler "noticed" that it resumed. That is, the wake up may
* race with the call to schedule(). */
if (state->scheduled != tsk) {
demo_requeue(tsk, state);
if (edf_preemption_needed(&state->local_queues, state->scheduled)) {
preempt_if_preemptable(state->scheduled, state->cpu);
}
}
raw_spin_unlock_irqrestore(&state->local_queues.ready_lock, flags);
}
static struct task_struct* pfair_schedule(struct task_struct * prev)
{
struct pfair_state* state = &__get_cpu_var(pfair_state);
int blocks;
struct task_struct* next = NULL;
raw_spin_lock(&pfair_lock);
blocks = is_realtime(prev) && !is_running(prev);
if (state->local && safe_to_schedule(state->local, state->cpu))
next = state->local;
if (prev != next) {
tsk_rt(prev)->scheduled_on = NO_CPU;
if (next)
tsk_rt(next)->scheduled_on = state->cpu;
}
raw_spin_unlock(&pfair_lock);
if (next)
TRACE_TASK(next, "scheduled rel=%lu at %lu (%llu)\n",
tsk_pfair(next)->release, pfair_time, litmus_clock());
else if (is_realtime(prev))
TRACE("Becomes idle at %lu (%llu)\n", pfair_time, litmus_clock());
return next;
}
static void pfair_task_wake_up(struct task_struct *t)
{
unsigned long flags;
lt_t now;
TRACE_TASK(t, "wakes at %llu, release=%lu, pfair_time:%lu\n",
litmus_clock(), cur_release(t), pfair_time);
raw_spin_lock_irqsave(&pfair_lock, flags);
/* It is a little unclear how to deal with Pfair
* tasks that block for a while and then wake. For now,
* if a task blocks and wakes before its next job release,
* then it may resume if it is currently linked somewhere
* (as if it never blocked at all). Otherwise, we have a
* new sporadic job release.
*/
if (tsk_pfair(t)->sporadic_release) {
now = litmus_clock();
release_at(t, now);
prepare_release(t, time2quanta(now, CEIL));
sched_trace_task_release(t);
/* FIXME: race with pfair_time advancing */
pfair_add_release(t);
tsk_pfair(t)->sporadic_release = 0;
}
check_preempt(t);
raw_spin_unlock_irqrestore(&pfair_lock, flags);
TRACE_TASK(t, "wake up done at %llu\n", litmus_clock());
}
void sobliv_on_blocked(struct task_struct* t)
{
if (bt_flag_is_set(t, BTF_IS_TOP_M)) {
/* there is a fraction of time where we're double-counting the
* time tracked by the rq and suspension time.
* TODO: Do this recording closer to suspension time. */
tsk_rt(t)->budget.suspend_timestamp = litmus_clock();
if (!tsk_rt(t)->budget.timer.armed) {
/* budget exhaustion timer fired as t was waking up, so budget
* routine thought t was running. We need to re-trigger the budget
* exhastion routine via timer. Schedulers do not call
* job_completion() when a task blocks, even if t's budget has been
* exhausted. Unfortunately, we cannot rerun the exhaustion routine
* here due to spinlock ordering issues. Just re-arm the timer with
* the exhausted time, re-running the timer routine immediately once
* interrupts have been re-enabled. */
/* clear the exhausted flag so handle will re-run. this will not
* trigger another exhaustion signal since signals are controled by
* BTF_SIG_BUDGET_SENT. */
bt_flag_clear(t, BTF_BUDGET_EXHAUSTED);
if (likely(!bt_flag_is_set(t, BTF_WAITING_FOR_RELEASE))) {
TRACE_TASK(t, "budget timer not armed. "
"Raced with exhaustion-resched? Re-arming.\n");
arm_enforcement_timer(t, 1);
}
else {
TRACE_TASK(t, "not arming timer because task is waiting "
"for release.\n");
}
}
}
}
static void boost_priority(struct task_struct* t)
{
unsigned long flags;
psnedf_domain_t* pedf = task_pedf(t);
lt_t now;
raw_readyq_lock_irqsave(&pedf->slock, flags);
now = litmus_clock();
TRACE_TASK(t, "priority boosted at %llu\n", now);
tsk_rt(t)->priority_boosted = 1;
tsk_rt(t)->boost_start_time = now;
if (pedf->scheduled != t) {
/* holder may be queued: first stop queue changes */
raw_spin_lock(&pedf->domain.release_lock);
if (is_queued(t) &&
/* If it is queued, then we need to re-order. */
bheap_decrease(edf_ready_order, tsk_rt(t)->heap_node) &&
/* If we bubbled to the top, then we need to check for preemptions. */
edf_preemption_needed(&pedf->domain, pedf->scheduled))
preempt(pedf);
raw_spin_unlock(&pedf->domain.release_lock);
} /* else: nothing to do since the job is not queued while scheduled */
raw_readyq_unlock_irqrestore(&pedf->slock, flags);
}
/* Prepare a task for running in RT mode
*/
static void psnedf_task_new(struct task_struct * t, int on_rq, int is_scheduled)
{
rt_domain_t* edf = task_edf(t);
psnedf_domain_t* pedf = task_pedf(t);
unsigned long flags;
TRACE_TASK(t, "psn edf: task new, cpu = %d\n",
t->rt_param.task_params.cpu);
/* setup job parameters */
release_at(t, litmus_clock());
/* The task should be running in the queue, otherwise signal
* code will try to wake it up with fatal consequences.
*/
raw_readyq_lock_irqsave(&pedf->slock, flags);
if (is_scheduled) {
/* there shouldn't be anything else scheduled at the time */
BUG_ON(pedf->scheduled);
pedf->scheduled = t;
} else {
/* !is_scheduled means it is not scheduled right now, but it
* does not mean that it is suspended. If it is not suspended,
* it still needs to be requeued. If it is suspended, there is
* nothing that we need to do as it will be handled by the
* wake_up() handler. */
if (is_running(t)) {
requeue(t, edf);
/* maybe we have to reschedule */
psnedf_preempt_check(pedf);
}
}
raw_readyq_unlock_irqrestore(&pedf->slock, flags);
}
static void unboost_priority(struct task_struct* t)
{
unsigned long flags;
psnedf_domain_t* pedf = task_pedf(t);
lt_t now;
raw_readyq_lock_irqsave(&pedf->slock, flags);
now = litmus_clock();
/* assumption: this only happens when the job is scheduled */
BUG_ON(pedf->scheduled != t);
TRACE_TASK(t, "priority restored at %llu\n", now);
/* priority boosted jobs must be scheduled */
BUG_ON(pedf->scheduled != t);
tsk_rt(t)->priority_boosted = 0;
tsk_rt(t)->boost_start_time = 0;
/* check if this changes anything */
if (edf_preemption_needed(&pedf->domain, pedf->scheduled))
preempt(pedf);
raw_readyq_unlock_irqrestore(&pedf->slock, flags);
}
inline static void arm_enforcement_timer(struct task_struct* t, int force)
{
struct enforcement_timer* et;
lt_t when_to_fire, remaining_budget;
lt_t now;
unsigned long flags;
BUG_ON(!t);
BUG_ON(!is_realtime(t));
et = &tsk_rt(t)->budget.timer;
if (et->armed) {
TRACE_TASK(t, "timer already armed!\n");
return;
}
if (!force) {
if ( (!budget_enforced(t) ||
(budget_enforced(t) &&
bt_flag_is_set(t, BTF_BUDGET_EXHAUSTED)))
&&
(!budget_signalled(t) ||
(budget_signalled(t) &&
bt_flag_is_set(t, BTF_SIG_BUDGET_SENT)))) {
TRACE_TASK(t,
"trying to arm timer when budget "
"has already been exhausted.\n");
return;
}
}
TRACE_TASK(t, "arming enforcement timer.\n");
/* __hrtimer_start_range_ns() cancels the timer
* anyway, so we don't have to check whether it is still armed */
raw_spin_lock_irqsave(&et->lock, flags);
if (et->armed) {
TRACE_TASK(t, "timer already armed (race)!\n");
goto out;
}
now = litmus_clock();
remaining_budget = budget_remaining(t);
when_to_fire = now + remaining_budget;
TRACE_TASK(t, "budget remaining: %ld, when_to_fire: %ld\n",
remaining_budget, when_to_fire);
__hrtimer_start_range_ns(&et->timer,
ns_to_ktime(when_to_fire),
0 /* delta */,
HRTIMER_MODE_ABS_PINNED, /* TODO: need to use non-pinned? */
0 /* no wakeup */);
et->armed = 1;
out:
raw_spin_unlock_irqrestore(&et->lock, flags);
}
static void psnedf_task_block(struct task_struct *t)
{
/* only running tasks can block, thus t is in no queue */
TRACE_TASK(t, "block at %llu, state=%d\n", litmus_clock(), t->state);
BUG_ON(!is_realtime(t));
BUG_ON(is_queued(t));
}
static void psnedf_task_wake_up(struct task_struct *task)
{
unsigned long flags;
psnedf_domain_t* pedf = task_pedf(task);
rt_domain_t* edf = task_edf(task);
lt_t now;
TRACE_TASK(task, "wake_up at %llu\n", litmus_clock());
raw_readyq_lock_irqsave(&pedf->slock, flags);
set_task_state(task, TASK_RUNNING);
BUG_ON(is_queued(task));
now = litmus_clock();
if (is_sporadic(task) && is_tardy(task, now)
#ifdef CONFIG_LITMUS_LOCKING
/* We need to take suspensions because of semaphores into
* account! If a job resumes after being suspended due to acquiring
* a semaphore, it should never be treated as a new job release.
*/
&& !is_priority_boosted(task)
#endif
) {
/* new sporadic release */
release_at(task, now);
sched_trace_task_release(task);
}
budget_state_machine(task,on_wakeup);
/* Only add to ready queue if it is not the currently-scheduled
* task. This could be the case if a task was woken up concurrently
* on a remote CPU before the executing CPU got around to actually
* de-scheduling the task, i.e., wake_up() raced with schedule()
* and won.
*/
if (pedf->scheduled != task) {
requeue(task, edf);
psnedf_preempt_check(pedf);
}
raw_readyq_unlock_irqrestore(&pedf->slock, flags);
TRACE_TASK(task, "wake up done\n");
}
static void schedule_next_quantum(quanta_t time)
{
int cpu;
/* called with interrupts disabled */
PTRACE("--- Q %lu at %llu PRE-SPIN\n",
time, litmus_clock());
raw_spin_lock(&pfair_lock);
PTRACE("<<< Q %lu at %llu\n",
time, litmus_clock());
sched_trace_quantum_boundary();
advance_subtasks(time);
poll_releases(time);
schedule_subtasks(time);
for (cpu = 0; cpu < num_online_cpus(); cpu++)
if (pstate[cpu]->linked)
PTRACE_TASK(pstate[cpu]->linked,
" linked on %d.\n", cpu);
else
PTRACE("(null) linked on %d.\n", cpu);
/* We are done. Advance time. */
mb();
for (cpu = 0; cpu < num_online_cpus(); cpu++) {
if (pstate[cpu]->local_tick != pstate[cpu]->cur_tick) {
TRACE("BAD Quantum not acked on %d "
"(l:%lu c:%lu p:%lu)\n",
cpu,
pstate[cpu]->local_tick,
pstate[cpu]->cur_tick,
pfair_time);
pstate[cpu]->missed_quanta++;
}
pstate[cpu]->cur_tick = time;
}
PTRACE(">>> Q %lu at %llu\n",
time, litmus_clock());
raw_spin_unlock(&pfair_lock);
}
/* Add the task `tsk` to the appropriate queue. Assumes the caller holds the ready lock.
*/
static void demo_requeue(struct task_struct *tsk, struct demo_cpu_state *cpu_state)
{
if (is_released(tsk, litmus_clock())) {
/* Uses __add_ready() instead of add_ready() because we already
* hold the ready lock. */
__add_ready(&cpu_state->local_queues, tsk);
} else {
/* Uses add_release() because we DON'T have the release lock. */
add_release(&cpu_state->local_queues, tsk);
}
}
static void requeue(struct task_struct* t, rt_domain_t *edf)
{
if (t->state != TASK_RUNNING)
TRACE_TASK(t, "requeue: !TASK_RUNNING\n");
tsk_rt(t)->completed = 0;
if (is_early_releasing(t) || is_released(t, litmus_clock()))
__add_ready(edf, t);
else
add_release(edf, t); /* it has got to wait */
}
/* pfair_tick - this function is called for every local timer
* interrupt.
*/
static void pfair_tick(struct task_struct* t)
{
struct pfair_state* state = &__get_cpu_var(pfair_state);
quanta_t time, cur;
int retry = 10;
do {
cur = current_quantum(state);
PTRACE("q %lu at %llu\n", cur, litmus_clock());
/* Attempt to advance time. First CPU to get here
* will prepare the next quantum.
*/
time = cmpxchg(&pfair_time,
cur - 1, /* expected */
cur /* next */
);
if (time == cur - 1) {
/* exchange succeeded */
wait_for_quantum(cur - 1, state);
schedule_next_quantum(cur);
retry = 0;
} else if (time_before(time, cur - 1)) {
/* the whole system missed a tick !? */
catchup_quanta(time, cur, state);
retry--;
} else if (time_after(time, cur)) {
/* our timer lagging behind!? */
TRACE("BAD pfair_time:%lu > cur:%lu\n", time, cur);
retry--;
} else {
/* Some other CPU already started scheduling
* this quantum. Let it do its job and then update.
*/
retry = 0;
}
} while (retry);
/* Spin locally until time advances. */
wait_for_quantum(cur, state);
/* copy assignment */
/* FIXME: what if we race with a future update? Corrupted state? */
state->local = state->linked;
/* signal that we are done */
mb();
state->local_tick = state->cur_tick;
if (state->local != current
&& (is_realtime(current) || is_present(state->local)))
set_tsk_need_resched(current);
}
void simple_io_on_wakeup(struct task_struct* t)
{
/* we're waking up from an io-based suspension */
if (tsk_rt(t)->budget.suspend_timestamp) {
lt_t suspend_cost = litmus_clock() -
tsk_rt(t)->budget.suspend_timestamp;
tsk_rt(t)->budget.suspend_timestamp = 0;
TRACE_TASK(t, "budget consumed while io-suspended: %llu\n",
suspend_cost);
get_exec_time(t) += suspend_cost;
}
else {
TRACE_TASK(t, "waking from non-io blocking\n");
}
}
void sobliv_on_exit_top_m(struct task_struct* t)
{
if (budget_precisely_tracked(t)) {
if (tsk_rt(t)->budget.timer.armed) {
if (!is_running(t)) {
/* the time at which we started draining budget while
* suspended is recorded in evt_timestamp. evt_timestamp
* was set either when 't' exited the top-m while suspended
* or when 't' blocked. */
lt_t suspend_cost;
BUG_ON(!tsk_rt(t)->budget.suspend_timestamp);
suspend_cost = litmus_clock() -
tsk_rt(t)->budget.suspend_timestamp;
TRACE_TASK(t, "budget consumed while suspended: %llu\n",
suspend_cost);
get_exec_time(t) += suspend_cost;
/* timer should have fired before now */
if (get_exec_time(t) + 1000000/10 > get_exec_cost(t)) {
TRACE_TASK(t,
"budget overrun while suspended by over 1/10 "
"millisecond! timer should have already fired!\n");
WARN_ON(1);
}
}
TRACE_TASK(t, "stops draining budget\n");
/* the callback will handle it if it is executing */
if (!hrtimer_callback_running(&tsk_rt(t)->budget.timer.timer)) {
/* TODO: record a timestamp if the task isn't running */
cancel_enforcement_timer(t);
}
else {
TRACE_TASK(t,
"within callback context. skipping operation.\n");
}
}
else {
TRACE_TASK(t, "was not draining budget\n");
}
}
}
void simple_io_on_blocked(struct task_struct* t)
{
/* hiding is turned on by locking protocols, so if there isn't any
hiding, then we're blocking for some other reason. assume it's I/O. */
int for_io = 0;
#ifdef CONFIG_LITMUS_NESTED_LOCKING
for_io |= !tsk_rt(t)->blocked_lock;
#endif
#ifdef CONFIG_REALTIME_AUX_TASKS
for_io |= tsk_rt(t)->has_aux_tasks && !tsk_rt(t)->hide_from_aux_tasks;
#endif
#ifdef CONFIG_LITMUS_NVIDIA
for_io |= tsk_rt(t)->held_gpus && !tsk_rt(t)->hide_from_gpu;
#endif
/* we drain budget for io-based suspensions */
if (for_io) {
/* there is a fraction of time where we're double-counting the
* time tracked by the rq and suspension time.
* TODO: Do this recording closer to suspension time. */
tsk_rt(t)->budget.suspend_timestamp = litmus_clock();
TRACE_TASK(t, "blocking for I/O.\n");
if (!tsk_rt(t)->budget.timer.armed) {
bt_flag_clear(t, BTF_BUDGET_EXHAUSTED);
if (likely(!bt_flag_is_set(t, BTF_WAITING_FOR_RELEASE))) {
TRACE_TASK(t, "budget timer not armed. "
"Raced with exhaustion-resched? Re-arming.\n");
arm_enforcement_timer(t, 1);
}
else {
TRACE_TASK(t, "not arming timer because task is waiting "
"for release.\n");
}
}
}
else {
TRACE_TASK(t, "blocking for litmus lock. stop draining.\n");
simple_on_blocked(t);
}
}
feather_callback void save_task_latency(unsigned long event,
unsigned long when_ptr)
{
lt_t now = litmus_clock();
lt_t *when = (lt_t*) when_ptr;
unsigned int seq_no;
int cpu = raw_smp_processor_id();
struct timestamp *ts;
seq_no = fetch_and_inc((int *) &ts_seq_no);
if (ft_buffer_start_write(trace_ts_buf, (void**) &ts)) {
ts->event = event;
ts->timestamp = now - *when;
ts->seq_no = seq_no;
ts->cpu = cpu;
ts->task_type = TSK_RT;
__save_irq_flags(ts);
ft_buffer_finish_write(trace_ts_buf, ts);
}
}
void sobliv_on_wakeup(struct task_struct* t)
{
if (bt_flag_is_set(t, BTF_IS_TOP_M)) {
/* we're waking up while in top-m. record the time spent
* suspended while draining in exec_cost. suspend_timestamp was
* either set when we entered top-m while asleep, or when we
* blocked. */
if (tsk_rt(t)->budget.suspend_timestamp) {
lt_t suspend_cost = litmus_clock() -
tsk_rt(t)->budget.suspend_timestamp;
tsk_rt(t)->budget.suspend_timestamp = 0;
TRACE_TASK(t, "budget consumed while suspended: %llu\n",
suspend_cost);
get_exec_time(t) += suspend_cost;
}
else {
WARN_ON(!bt_flag_is_set(t, BTF_WAITING_FOR_RELEASE));
}
}
}
static enum hrtimer_restart __on_timeout(struct hrtimer *timer)
{
enum hrtimer_restart restart = HRTIMER_NORESTART;
unsigned long flags;
struct budget_tracker* bt =
container_of(
container_of(timer,
struct enforcement_timer,
timer),
struct budget_tracker,
timer);
struct task_struct* t =
container_of(
container_of(bt, struct rt_param, budget),
struct task_struct,
rt_param);
TRACE_TASK(t, "budget timer interrupt fired at time %lu\n",
litmus_clock());
raw_spin_lock_irqsave(&bt->timer.lock, flags);
tsk_rt(t)->budget.timer.armed = 0;
raw_spin_unlock_irqrestore(&bt->timer.lock, flags);
if (unlikely(bt_flag_is_set(t, BTF_WAITING_FOR_RELEASE))) {
TRACE_TASK(t,
"spurious exhastion while waiting for release. dropping.\n");
goto out;
}
restart = bt->ops->on_exhausted(t,!IN_SCHEDULE);
raw_spin_lock_irqsave(&bt->timer.lock, flags);
tsk_rt(t)->budget.timer.armed = (restart == HRTIMER_RESTART);
raw_spin_unlock_irqrestore(&bt->timer.lock, flags);
out:
return restart;
}
void sobliv_on_enter_top_m(struct task_struct* t)
{
if (!bt_flag_is_set(t, BTF_SIG_BUDGET_SENT)) {
if (tsk_rt(t)->budget.timer.armed)
TRACE_TASK(t, "budget timer already armed.\n");
else {
/* if we're blocked, then record the time at which we
started measuring */
if (!is_running(t))
tsk_rt(t)->budget.suspend_timestamp = litmus_clock();
/* the callback will handle it if it is executing */
if (!hrtimer_callback_running(&tsk_rt(t)->budget.timer.timer)) {
arm_enforcement_timer(t, 0);
}
else {
TRACE_TASK(t,
"within callback context. deferring timer arm.\n");
}
}
}
}
static quanta_t current_quantum(struct pfair_state* state)
{
lt_t t = litmus_clock() - state->offset;
return time2quanta(t, FLOOR);
}
static void pfair_task_block(struct task_struct *t)
{
BUG_ON(!is_realtime(t));
TRACE_TASK(t, "blocks at %llu, state:%d\n",
litmus_clock(), t->state);
}
static struct task_struct* psnedf_schedule(struct task_struct * prev)
{
psnedf_domain_t* pedf = local_pedf;
rt_domain_t* edf = &pedf->domain;
struct task_struct* next;
int out_of_time, sleep, preempt,
np, exists, blocks, resched;
raw_readyq_lock(&pedf->slock);
/* sanity checking
* differently from gedf, when a task exits (dead)
* pedf->schedule may be null and prev _is_ realtime
*/
BUG_ON(pedf->scheduled && pedf->scheduled != prev);
BUG_ON(pedf->scheduled && !is_realtime(prev));
/* (0) Determine state */
exists = pedf->scheduled != NULL;
blocks = exists && !is_running(pedf->scheduled);
out_of_time = exists &&
budget_enforced(pedf->scheduled) &&
bt_flag_is_set(pedf->scheduled, BTF_BUDGET_EXHAUSTED);
np = exists && is_np(pedf->scheduled);
sleep = exists && is_completed(pedf->scheduled);
preempt = edf_preemption_needed(edf, prev);
/* If we need to preempt do so.
* The following checks set resched to 1 in case of special
* circumstances.
*/
resched = preempt;
/* Do budget stuff */
if (blocks)
budget_state_machine(prev,on_blocked);
else if (sleep)
budget_state_machine(prev,on_sleep);
else if (preempt)
budget_state_machine(prev,on_preempt);
/* If a task blocks we have no choice but to reschedule.
*/
if (blocks)
resched = 1;
/* Request a sys_exit_np() call if we would like to preempt but cannot.
* Multiple calls to request_exit_np() don't hurt.
*/
if (np && (out_of_time || preempt || sleep))
request_exit_np(pedf->scheduled);
/* Any task that is preemptable and either exhausts its execution
* budget or wants to sleep completes. We may have to reschedule after
* this.
*/
if (!np && (out_of_time || sleep) && !blocks) {
job_completion(pedf->scheduled, !sleep);
resched = 1;
}
/* The final scheduling decision. Do we need to switch for some reason?
* Switch if we are in RT mode and have no task or if we need to
* resched.
*/
next = NULL;
if ((!np || blocks) && (resched || !exists)) {
/* When preempting a task that does not block, then
* re-insert it into either the ready queue or the
* release queue (if it completed). requeue() picks
* the appropriate queue.
*/
if (pedf->scheduled && !blocks)
requeue(pedf->scheduled, edf);
next = __take_ready(edf);
} else
/* Only override Linux scheduler if we have a real-time task
* scheduled that needs to continue.
*/
if (exists)
next = prev;
if (next) {
TRACE_TASK(next, "scheduled at %llu\n", litmus_clock());
} else {
TRACE("becoming idle at %llu\n", litmus_clock());
}
pedf->scheduled = next;
sched_state_task_picked();
raw_readyq_unlock(&pedf->slock);
return next;
}