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);
}
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);
}
/* 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 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);
}
static int psnedf_preempt_check(psnedf_domain_t *pedf)
{
if (edf_preemption_needed(&pedf->domain, pedf->scheduled)) {
preempt(pedf);
return 1;
} else
return 0;
}
static int demo_check_for_preemption_on_release(rt_domain_t *local_queues)
{
struct demo_cpu_state *state = container_of(local_queues, struct demo_cpu_state,
local_queues);
/* Because this is a callback from rt_domain_t we already hold
* the necessary lock for the ready queue. */
if (edf_preemption_needed(local_queues, state->scheduled)) {
preempt_if_preemptable(state->scheduled, state->cpu);
return 1;
}
return 0;
}
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;
}
static struct task_struct* demo_schedule(struct task_struct * prev)
{
struct demo_cpu_state *local_state = local_cpu_state();
/* next == NULL means "schedule background work". */
struct task_struct *next = NULL;
/* prev's task state */
int exists, out_of_time, job_completed, self_suspends, preempt, resched;
raw_spin_lock(&local_state->local_queues.ready_lock);
BUG_ON(local_state->scheduled && local_state->scheduled != prev);
BUG_ON(local_state->scheduled && !is_realtime(prev));
exists = local_state->scheduled != NULL;
self_suspends = exists && !is_current_running();
out_of_time = exists && budget_enforced(prev) && budget_exhausted(prev);
job_completed = exists && is_completed(prev);
/* preempt is true if task `prev` has lower priority than something on
* the ready queue. */
preempt = edf_preemption_needed(&local_state->local_queues, prev);
/* check all conditions that make us reschedule */
resched = preempt;
/* if `prev` suspends, it CANNOT be scheduled anymore => reschedule */
if (self_suspends) {
resched = 1;
}
/* also check for (in-)voluntary job completions */
if (out_of_time || job_completed) {
demo_job_completion(prev, out_of_time);
resched = 1;
}
if (resched) {
/* First check if the previous task goes back onto the ready
* queue, which it does if it did not self_suspend.
*/
if (exists && !self_suspends) {
demo_requeue(prev, local_state);
}
next = __take_ready(&local_state->local_queues);
} else {
/* No preemption is required. */
next = local_state->scheduled;
}
local_state->scheduled = next;
if (exists && prev != next) {
TRACE_TASK(prev, "descheduled.\n");
}
if (next) {
TRACE_TASK(next, "scheduled.\n");
}
/* This mandatory. It triggers a transition in the LITMUS^RT remote
* preemption state machine. Call this AFTER the plugin has made a local
* scheduling decision.
*/
sched_state_task_picked();
raw_spin_unlock(&local_state->local_queues.ready_lock);
return next;
}
