/*
* Generic function to trigger preemption on either local or remote cpu
* from scheduler plugins. The key feature is that this function is
* non-preemptive section aware and does not invoke the scheduler / send
* IPIs if the to-be-preempted task is actually non-preemptive.
*/
void preempt_if_preemptable(struct task_struct* t, int cpu)
{
/* t is the real-time task executing on CPU on_cpu If t is NULL, then
* on_cpu is currently scheduling background work.
*/
int reschedule = 0;
if (!t)
/* move non-real-time task out of the way */
reschedule = 1;
else {
if (smp_processor_id() == cpu) {
/* local CPU case */
/* check if we need to poke userspace */
if (is_user_np(t))
/* Yes, poke it. This doesn't have to be atomic since
* the task is definitely not executing. */
request_exit_np(t);
else if (!is_kernel_np(t))
/* only if we are allowed to preempt the
* currently-executing task */
reschedule = 1;
} else {
/* Remote CPU case. Only notify if it's not a kernel
* NP section and if we didn't set the userspace
* flag. */
reschedule = !(is_kernel_np(t) || request_exit_np_atomic(t));
}
}
if (likely(reschedule))
litmus_reschedule(cpu);
}
static enum hrtimer_restart psnedf_simple_on_exhausted(struct task_struct *t, int in_schedule)
{
/* Assumption: t is scheduled on the CPU executing this callback */
if (budget_signalled(t) && !bt_flag_is_set(t, BTF_SIG_BUDGET_SENT)) {
/* signal exhaustion */
send_sigbudget(t); /* will set BTF_SIG_BUDGET_SENT */
}
if (budget_enforced(t) && !bt_flag_test_and_set(t, BTF_BUDGET_EXHAUSTED)) {
if (!is_np(t)) {
/* np tasks will be preempted when they become
* preemptable again
*/
litmus_reschedule_local();
TRACE("%d is preemptable => FORCE_RESCHED\n", t->pid);
} else if (is_user_np(t)) {
TRACE("%d is non-preemptable, preemption delayed.\n", t->pid);
request_exit_np(t);
}
}
return HRTIMER_NORESTART;
}
