/* 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);
/*
* litmus_tick gets called by scheduler_tick() with HZ freq
* Interrupts are disabled
*/
static void litmus_tick(struct rq *rq, struct task_struct *p)
{
TS_PLUGIN_TICK_START;
if (is_realtime(p))
update_time_litmus(rq, p);
/* plugin tick */
litmus->tick(p);
TS_PLUGIN_TICK_END;
return;
}
static struct task_struct *
litmus_schedule(struct rq *rq, struct task_struct *prev)
{
struct rq* other_rq;
struct task_struct *next;
long was_running;
lt_t _maybe_deadlock = 0;
/* let the plugin schedule */
next = litmus->schedule(prev);
/* check if a global plugin pulled a task from a different RQ */
if (next && task_rq(next) != rq) {
/* we need to migrate the task */
other_rq = task_rq(next);
TRACE_TASK(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();
raw_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(next, "stack_in_use=%d\n",
next->rt_param.stack_in_use);
if (next->rt_param.stack_in_use != NO_CPU) {
TRACE_TASK(next, "waiting to deschedule\n");
_maybe_deadlock = litmus_clock();
}
while (next->rt_param.stack_in_use != NO_CPU) {
cpu_relax();
mb();
if (next->rt_param.stack_in_use == NO_CPU)
TRACE_TASK(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(next,"stack too long in use. "
"Deadlock?\n");
next = NULL;
/* bail out */
raw_spin_lock(&rq->lock);
return next;
}
}
#ifdef __ARCH_WANT_UNLOCKED_CTXSW
if (next->oncpu)
TRACE_TASK(next, "waiting for !oncpu");
while (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(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(next) || !is_running(next)) {
/* BAD BAD BAD */
TRACE_TASK(next,"BAD: migration invariant FAILED: "
"rt=%d running=%d\n",
is_realtime(next),
is_running(next));
/* drop the task */
next = NULL;
}
/* release the other CPU's runqueue, but keep ours */
raw_spin_unlock(&other_rq->lock);
}
if (next) {
next->rt_param.stack_in_use = rq->cpu;
next->se.exec_start = rq->clock;
}
return next;
}
static void enqueue_task_litmus(struct rq *rq, struct task_struct *p,
int wakeup, bool head)
{
if (wakeup) {
sched_trace_task_resume(p);
tsk_rt(p)->present = 1;
/* LITMUS^RT plugins need to update the state
* _before_ making it available in global structures.
* Linux gets away with being lazy about the task state
* update. We can't do that, hence we update the task
* state already here.
*
* WARNING: this needs to be re-evaluated when porting
* to newer kernel versions.
*/
p->state = TASK_RUNNING;
litmus->task_wake_up(p);
rq->litmus.nr_running++;
} 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);
rq->litmus.nr_running--;
} 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);
/* sched_yield() is called to trigger delayed preemptions.
* Thus, mark the current task as needing to be rescheduled.
* This will cause the scheduler plugin to be invoked, which can
* then determine if a preemption is still required.
*/
clear_exit_np(current);
set_tsk_need_resched(current);
}
/* Plugins are responsible for this.
*/
static void check_preempt_curr_litmus(struct rq *rq, struct task_struct *p, int flags)
{
}
static void put_prev_task_litmus(struct rq *rq, struct task_struct *p)
{
}
static void pre_schedule_litmus(struct rq *rq, struct task_struct *prev)
{
update_time_litmus(rq, prev);
if (!is_running(prev))
tsk_rt(prev)->present = 0;
}
/* pick_next_task_litmus() - litmus_schedule() function
*
* return the next task to be scheduled
*/
static struct task_struct *pick_next_task_litmus(struct rq *rq)
{
/* get the to-be-switched-out task (prev) */
struct task_struct *prev = rq->litmus.prev;
struct task_struct *next;
/* if not called from schedule() but from somewhere
* else (e.g., migration), return now!
*/
if(!rq->litmus.prev)
return NULL;
rq->litmus.prev = NULL;
TS_PLUGIN_SCHED_START;
next = litmus_schedule(rq, prev);
TS_PLUGIN_SCHED_END;
return next;
}
static void task_tick_litmus(struct rq *rq, struct task_struct *p, int queued)
{
/* nothing to do; tick related tasks are done by litmus_tick() */
return;
}
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 rq *rq, 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.
* We don't care about the scheduling domain; can gets called from
* exec, fork, wakeup.
*/
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 task_cpu(p);
}
#endif
static 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,
.pre_schedule = pre_schedule_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,
};
