/* This file is included from kernel/sched.c */
#include <litmus/litmus.h>
#include <litmus/sched_plugin.h>
static void update_time_litmus(struct rq *rq, struct task_struct *p)
{
u64 delta = rq->clock - p->se.exec_start;
if (unlikely((s64)delta < 0))
delta = 0;
/* per job counter */
p->rt_param.job_params.exec_time += delta;
/* task counter */
p->se.sum_exec_runtime += delta;
/* sched_clock() */
p->se.exec_start = rq->clock;
cpuacct_charge(p, delta);
}
static void double_rq_lock(struct rq *rq1, struct rq *rq2);
static void double_rq_unlock(struct rq *rq1, struct rq *rq2);
static void litmus_tick(struct rq *rq, struct task_struct *p)
{
if (is_realtime(p))
update_time_litmus(rq, p);
litmus->tick(p);
}
static void litmus_schedule(struct rq *rq, struct task_struct *prev)
{
struct rq* other_rq;
long was_running;
lt_t _maybe_deadlock = 0;
/* WARNING: rq is _not_ locked! */
if (is_realtime(prev)) {
update_time_litmus(rq, prev);
if (!is_running(prev))
tsk_rt(prev)->present = 0;
}
/* let the plugin schedule */
rq->litmus_next = litmus->schedule(prev);
/* check if a global plugin pulled a task from a different RQ */
if (rq->litmus_next && task_rq(rq->litmus_next) != rq) {
/* we need to migrate the task */
other_rq = task_rq(rq->litmus_next);
TRACE_TASK(rq->litmus_next, "migrate from %d\n", other_rq->cpu);
/* while we drop the lock, the prev task could change its
* state
*/
was_running = is_running(prev);
mb();
spin_unlock(&rq->lock);
/* Don't race with a concurrent switch. This could deadlock in
* the case of cross or circular migrations. It's the job of
* the plugin to make sure that doesn't happen.
*/
TRACE_TASK(rq->litmus_next, "stack_in_use=%d\n",
rq->litmus_next->rt_param.stack_in_use);
if (rq->litmus_next->rt_param.stack_in_use != NO_CPU) {
TRACE_TASK(rq->litmus_next, "waiting to deschedule\n");
_maybe_deadlock = litmus_clock();
}
while (rq->litmus_next->rt_param.stack_in_use != NO_CPU) {
cpu_relax();
mb();
if (rq->litmus_next->rt_param.stack_in_use == NO_CPU)
TRACE_TASK(rq->litmus_next,
"descheduled. Proceeding.\n");
if (lt_before(_maybe_deadlock + 10000000,
litmus_clock())) {
/* We've been spinning for 10ms.
* Something can't be right!
* Let's abandon the task and bail out; at least
* we will have debug info instead of a hard
* deadlock.
*/
TRACE_TASK(rq->litmus_next,
"stack too long in use. "
"Deadlock?\n");
rq->litmus_next = NULL;
/* bail out */
spin_lock(&rq->lock);
return;
}
}
#ifdef __ARCH_WANT_UNLOCKED_CTXSW
if (rq->litmus_next->oncpu)
TRACE_TASK(rq->litmus_next, "waiting for !oncpu");
while (rq->litmus_next->oncpu) {
cpu_relax();
mb();
}
#endif
double_rq_lock(rq, other_rq);
mb();
if (is_realtime(prev) && is_running(prev) != was_running) {
TRACE_TASK(prev,
"state changed while we dropped"
" the lock: is_running=%d, was_running=%d\n",
is_running(prev), was_running);
if (is_running(prev) && !was_running) {
/* prev task became unblocked
* we need to simulate normal sequence of events
* to scheduler plugins.
*/
litmus->task_block(prev);
litmus->task_wake_up(prev);
}
}
set_task_cpu(rq->litmus_next, smp_processor_id());
/* DEBUG: now that we have the lock we need to make sure a
* couple of things still hold:
* - it is still a real-time task
* - it is still runnable (could have been stopped)
* If either is violated, then the active plugin is
* doing something wrong.
*/
if (!is_realtime(rq->litmus_next) ||
!is_running(rq->litmus_next)) {
/* BAD BAD BAD */
TRACE_TASK(rq->litmus_next,
"BAD: migration invariant FAILED: "
"rt=%d running=%d\n",
is_realtime(rq->litmus_next),
is_running(rq->litmus_next));
/* drop the task */
rq->litmus_next = NULL;
}
/* release the other CPU's runqueue, but keep ours */
spin_unlock(&other_rq->lock);
}
if (rq->litmus_next)
rq->litmus_next->rt_param.stack_in_use = rq->cpu;
}
static void enqueue_task_litmus(struct rq *rq, struct task_struct *p,
int wakeup)
{
if (wakeup) {
sched_trace_task_resume(p);
tsk_rt(p)->present = 1;
litmus->task_wake_up(p);
} else
TRACE_TASK(p, "ignoring an enqueue, not a wake up.\n");
}
static void dequeue_task_litmus(struct rq *rq, struct task_struct *p, int sleep)
{
if (sleep) {
litmus->task_block(p);
tsk_rt(p)->present = 0;
sched_trace_task_block(p);
} else
TRACE_TASK(p, "ignoring a dequeue, not going to sleep.\n");
}
static void yield_task_litmus(struct rq *rq)
{
BUG_ON(rq->curr != current);
litmus->complete_job();
}
/* Plugins are responsible for this.
*/
static void check_preempt_curr_litmus(struct rq *rq, struct task_struct *p, int flags)
{
}
/* has already been taken care of */
static void put_prev_task_litmus(struct rq *rq, struct task_struct *p)
{
}
static struct task_struct *pick_next_task_litmus(struct rq *rq)
{
struct task_struct* picked = rq->litmus_next;
rq->litmus_next = NULL;
if (picked)
picked->se.exec_start = rq->clock;
return picked;
}
static void task_tick_litmus(struct rq *rq, struct task_struct *p, int queued)
{
}
static void switched_to_litmus(struct rq *rq, struct task_struct *p, int running)
{
}
static void prio_changed_litmus(struct rq *rq, struct task_struct *p,
int oldprio, int running)
{
}
unsigned int get_rr_interval_litmus(struct task_struct *p)
{
/* return infinity */
return 0;
}
/* This is called when a task became a real-time task, either due to a SCHED_*
* class transition or due to PI mutex inheritance. We don't handle Linux PI
* mutex inheritance yet (and probably never will). Use LITMUS provided
* synchronization primitives instead.
*/
static void set_curr_task_litmus(struct rq *rq)
{
rq->curr->se.exec_start = rq->clock;
}
#ifdef CONFIG_SMP
/* execve tries to rebalance task in this scheduling domain */
static int select_task_rq_litmus(struct task_struct *p, int sd_flag, int flags)
{
/* preemption is already disabled.
* We don't want to change cpu here
*/
return smp_processor_id();
}
/* we don't repartition at runtime */
static unsigned long
load_balance_litmus(struct rq *this_rq, int this_cpu, struct rq *busiest,
unsigned long max_load_move,
struct sched_domain *sd, enum cpu_idle_type idle,
int *all_pinned, int *this_best_prio)
{
return 0;
}
static int
move_one_task_litmus(struct rq *this_rq, int this_cpu, struct rq *busiest,
struct sched_domain *sd, enum cpu_idle_type idle)
{
return 0;
}
#endif
const struct sched_class litmus_sched_class = {
.next = &rt_sched_class,
.enqueue_task = enqueue_task_litmus,
.dequeue_task = dequeue_task_litmus,
.yield_task = yield_task_litmus,
.check_preempt_curr = check_preempt_curr_litmus,
.pick_next_task = pick_next_task_litmus,
.put_prev_task = put_prev_task_litmus,
#ifdef CONFIG_SMP
.select_task_rq = select_task_rq_litmus,
.load_balance = load_balance_litmus,
.move_one_task = move_one_task_litmus,
#endif
.set_curr_task = set_curr_task_litmus,
.task_tick = task_tick_litmus,
.get_rr_interval = get_rr_interval_litmus,
.prio_changed = prio_changed_litmus,
.switched_to = switched_to_litmus,
};
