#include <linux/sched.h>
#include <linux/percpu.h>
#include <linux/hrtimer.h>
#include <linux/uaccess.h>
#include <litmus/litmus.h>
#include <litmus/preempt.h>
#include <litmus/sched_plugin.h>
#include <litmus/budget.h>
struct enforcement_timer {
/* The enforcement timer is used to accurately police
* slice budgets. */
struct hrtimer timer;
int armed;
};
DEFINE_PER_CPU(struct enforcement_timer, budget_timer);
static enum hrtimer_restart on_enforcement_timeout(struct hrtimer *timer)
{
struct enforcement_timer* et = container_of(timer,
struct enforcement_timer,
timer);
unsigned long flags;
local_irq_save(flags);
TRACE("enforcement timer fired.\n");
et->armed = 0;
/* activate scheduler */
litmus_reschedule_local();
local_irq_restore(flags);
return HRTIMER_NORESTART;
}
/* assumes called with IRQs off */
static void cancel_enforcement_timer(struct enforcement_timer* et)
{
int ret;
TRACE("cancelling enforcement timer.\n");
/* Since interrupts are disabled and et->armed is only
* modified locally, we do not need any locks.
*/
if (et->armed) {
ret = hrtimer_try_to_cancel(&et->timer);
/* Should never be inactive. */
BUG_ON(ret == 0);
/* Should never be running concurrently. */
BUG_ON(ret == -1);
et->armed = 0;
}
}
/* assumes called with IRQs off */
static void arm_enforcement_timer(struct enforcement_timer* et,
struct task_struct* t)
{
lt_t when_to_fire;
TRACE_TASK(t, "arming enforcement timer.\n");
WARN_ONCE(!hrtimer_is_hres_active(&et->timer),
KERN_ERR "WARNING: no high resolution timers available!?\n");
/* Calling this when there is no budget left for the task
* makes no sense, unless the task is non-preemptive. */
BUG_ON(budget_exhausted(t) && (!is_np(t)));
/* __hrtimer_start_range_ns() cancels the timer
* anyway, so we don't have to check whether it is still armed */
if (likely(!is_np(t))) {
when_to_fire = litmus_clock() + budget_remaining(t);
__hrtimer_start_range_ns(&et->timer,
ns_to_ktime(when_to_fire),
0 /* delta */,
HRTIMER_MODE_ABS_PINNED,
0 /* no wakeup */);
et->armed = 1;
}
}
/* expects to be called with IRQs off */
void update_enforcement_timer(struct task_struct* t)
{
struct enforcement_timer* et = this_cpu_ptr(&budget_timer);
if (t && budget_precisely_enforced(t)) {
/* Make sure we call into the scheduler when this budget
* expires. */
arm_enforcement_timer(et, t);
} else if (et->armed) {
/* Make sure we don't cause unnecessary interrupts. */
cancel_enforcement_timer(et);
}
}
static int __init init_budget_enforcement(void)
{
int cpu;
struct enforcement_timer* et;
for (cpu = 0; cpu < NR_CPUS; cpu++) {
et = &per_cpu(budget_timer, cpu);
hrtimer_init(&et->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
et->timer.function = on_enforcement_timeout;
}
return 0;
}
void litmus_current_budget(lt_t *used_so_far, lt_t *remaining)
{
struct task_struct *t = current;
unsigned long flags;
s64 delta;
local_irq_save(flags);
delta = sched_clock_cpu(smp_processor_id()) - t->se.exec_start;
if (delta < 0)
delta = 0;
TRACE_CUR("current_budget: sc:%llu start:%llu lt_t:%llu delta:%lld exec-time:%llu rem:%llu\n",
sched_clock_cpu(smp_processor_id()), t->se.exec_start,
litmus_clock(), delta,
tsk_rt(t)->job_params.exec_time,
budget_remaining(t));
if (used_so_far)
*used_so_far = tsk_rt(t)->job_params.exec_time + delta;
if (remaining) {
*remaining = budget_remaining(t);
if (*remaining > delta)
*remaining -= delta;
else
*remaining = 0;
}
local_irq_restore(flags);
}
asmlinkage long sys_get_current_budget(
lt_t __user * _expended,
lt_t __user *_remaining)
{
lt_t expended = 0, remaining = 0;
if (is_realtime(current))
litmus->current_budget(&expended, &remaining);
if (_expended && put_user(expended, _expended))
return -EFAULT;
if (_remaining && put_user(remaining, _remaining))
return -EFAULT;
return 0;
}
module_init(init_budget_enforcement);
