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#include <litmus/sched_plugin.h>
#include <litmus/trace.h>
#include <litmus/litmus.h>
#ifdef CONFIG_REALTIME_AUX_TASKS
#include <litmus/rt_param.h>
#include <litmus/aux_tasks.h>
#include <linux/time.h>
#define AUX_SLICE_NR_JIFFIES 4
#define AUX_SLICE_NS ((NSEC_PER_SEC / HZ) * AUX_SLICE_NR_JIFFIES)
static int admit_aux_task(struct task_struct *t)
{
int retval = 0;
struct task_struct *leader = t->group_leader;
/* budget enforcement increments job numbers. job numbers are used in
* tie-breaking of aux_tasks. method helps ensure:
* 1) aux threads with no inherited priority can starve another (they share
* the CPUs equally.
* 2) aux threads that inherit the same priority cannot starve each other.
*
* Assuming aux threads are well-behavied (they do very little work and
* suspend), risk of starvation should not be an issue, but this is a
* fail-safe.
*/
struct rt_task tp = {
.exec_cost = AUX_SLICE_NS,
.period = AUX_SLICE_NS,
.relative_deadline = AUX_SLICE_NS,
.phase = 0,
.cpu = task_cpu(leader), /* take CPU of group leader */
.priority = LITMUS_LOWEST_PRIORITY,
.cls = RT_CLASS_BEST_EFFORT,
.budget_policy = QUANTUM_ENFORCEMENT,
.drain_policy = DRAIN_SIMPLE,
.budget_signal_policy = NO_SIGNALS,
/* use SPORADIC instead of EARLY since util = 1.0 */
.release_policy = SPORADIC,
};
struct sched_param param = { .sched_priority = 0};
tsk_rt(t)->task_params = tp;
retval = sched_setscheduler_nocheck(t, SCHED_LITMUS, ¶m);
return retval;
}
int exit_aux_task(struct task_struct *t)
{
int retval = 0;
BUG_ON(!tsk_rt(t)->is_aux_task);
TRACE_CUR("Aux task %s/%d is exiting from %s/%d.\n",
t->comm, t->pid,
t->group_leader->comm, t->group_leader->pid);
tsk_rt(t)->is_aux_task = 0;
#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
list_del(&tsk_rt(t)->aux_task_node);
if (tsk_rt(t)->inh_task) {
litmus->__decrease_prio(t, NULL, 0);
}
#endif
return retval;
}
#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
static int aux_tasks_increase_priority(struct task_struct *leader, struct task_struct *hp)
{
int retval = 0;
struct list_head *pos;
// TRACE_CUR("Increasing priority of aux tasks in group %s/%d.\n", leader->comm, leader->pid);
list_for_each(pos, &tsk_aux(leader)->aux_tasks) {
struct task_struct *aux =
container_of(list_entry(pos, struct rt_param, aux_task_node),
struct task_struct, rt_param);
if (!is_realtime(aux)) {
TRACE_CUR("skipping non-real-time aux task %s/%d\n", aux->comm, aux->pid);
}
else if(tsk_rt(aux)->inh_task == hp) {
TRACE_CUR("skipping real-time aux task %s/%d that already inherits from %s/%d\n",
aux->comm, aux->pid, hp->comm, hp->pid);
}
else {
// aux tasks don't touch rt locks, so no nested call needed.
// TRACE_CUR("increasing %s/%d.\n", aux->comm, aux->pid);
retval = litmus->__increase_prio(aux, hp);
}
}
return retval;
}
static int aux_tasks_decrease_priority(struct task_struct *leader, struct task_struct *hp)
{
int retval = 0;
struct list_head *pos;
// TRACE_CUR("Decreasing priority of aux tasks in group %s/%d.\n", leader->comm, leader->pid);
list_for_each(pos, &tsk_aux(leader)->aux_tasks) {
struct task_struct *aux =
container_of(list_entry(pos, struct rt_param, aux_task_node),
struct task_struct, rt_param);
if (!is_realtime(aux)) {
TRACE_CUR("skipping non-real-time aux task %s/%d\n", aux->comm, aux->pid);
}
else {
// TRACE_CUR("decreasing %s/%d.\n", aux->comm, aux->pid);
retval = litmus->__decrease_prio(aux, hp, 0);
}
}
return retval;
}
#endif
int aux_task_owner_increase_priority(struct task_struct *t)
{
int retval = 0;
#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
struct task_struct *leader;
struct task_struct *hp = NULL;
struct task_struct *hp_eff = NULL;
int increase_aux = 0;
BUG_ON(!is_realtime(t));
BUG_ON(!tsk_rt(t)->has_aux_tasks);
leader = t->group_leader;
if (!binheap_is_in_heap(&tsk_rt(t)->aux_task_owner_node)) {
//WARN_ON(!is_running(t));
TRACE_CUR("aux tasks may not inherit from %s/%d in group %s/%d\n",
t->comm, t->pid, leader->comm, leader->pid);
goto out;
}
// TRACE_CUR("task %s/%d in group %s/%d increasing priority.\n", t->comm, t->pid, leader->comm, leader->pid);
hp = container_of(
binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
hp_eff = effective_priority(hp);
if (hp != t) { /* our position in the heap may have changed. hp is already at the root. */
binheap_decrease(&tsk_rt(t)->aux_task_owner_node, &tsk_aux(leader)->aux_task_owners);
}
else {
/* unconditionally propagate - t already has the updated eff and is at the root,
so we can't detect a change in inheritance, but we know that priority has
indeed increased/changed. */
increase_aux = 1;
}
hp = container_of(
binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
/* check if the eff. prio. of hp has changed */
if (increase_aux || (effective_priority(hp) != hp_eff)) {
hp_eff = effective_priority(hp);
// TRACE_CUR("%s/%d is new hp in group %s/%d.\n", t->comm, t->pid, leader->comm, leader->pid);
retval = aux_tasks_increase_priority(leader, hp_eff);
}
out:
#endif
return retval;
}
int aux_task_owner_decrease_priority(struct task_struct *t)
{
int retval = 0;
#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
struct task_struct *leader;
struct task_struct *hp = NULL;
struct task_struct *hp_eff = NULL;
BUG_ON(!is_realtime(t));
BUG_ON(!tsk_rt(t)->has_aux_tasks);
leader = t->group_leader;
if (!binheap_is_in_heap(&tsk_rt(t)->aux_task_owner_node)) {
//WARN_ON(!is_running(t));
TRACE_CUR("aux tasks may not inherit from %s/%d in group %s/%d\n",
t->comm, t->pid, leader->comm, leader->pid);
goto out;
}
// TRACE_CUR("task %s/%d in group %s/%d decresing priority.\n", t->comm, t->pid, leader->comm, leader->pid);
hp = container_of(
binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
hp_eff = effective_priority(hp);
binheap_delete(&tsk_rt(t)->aux_task_owner_node, &tsk_aux(leader)->aux_task_owners);
binheap_add(&tsk_rt(t)->aux_task_owner_node, &tsk_aux(leader)->aux_task_owners,
struct rt_param, aux_task_owner_node);
if (hp == t) { /* t was originally the hp */
struct task_struct *new_hp =
container_of(
binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
/* if the new_hp is still t, or if the effective priority has changed */
if ((new_hp == t) || (effective_priority(new_hp) != hp_eff)) {
hp_eff = effective_priority(new_hp);
// TRACE_CUR("%s/%d is no longer hp in group %s/%d.\n", t->comm, t->pid, leader->comm, leader->pid);
retval = aux_tasks_decrease_priority(leader, hp_eff);
}
}
out:
#endif
return retval;
}
int make_aux_task_if_required(struct task_struct *t)
{
struct task_struct *leader;
int retval = 0;
read_lock_irq(&tasklist_lock);
leader = t->group_leader;
if(!tsk_aux(leader)->initialized || !tsk_aux(leader)->aux_future) {
goto out;
}
TRACE_CUR("Making %s/%d in %s/%d an aux thread.\n", t->comm, t->pid, leader->comm, leader->pid);
INIT_LIST_HEAD(&tsk_rt(t)->aux_task_node);
INIT_BINHEAP_NODE(&tsk_rt(t)->aux_task_owner_node);
retval = admit_aux_task(t);
if (retval == 0) {
tsk_rt(t)->is_aux_task = 1;
#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
list_add_tail(&tsk_rt(t)->aux_task_node, &tsk_aux(leader)->aux_tasks);
if (!binheap_empty(&tsk_aux(leader)->aux_task_owners)) {
struct task_struct *hp =
container_of(
binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
TRACE_CUR("hp in group: %s/%d\n", hp->comm, hp->pid);
retval = litmus->__increase_prio(t, (tsk_rt(hp)->inh_task)? tsk_rt(hp)->inh_task : hp);
if (retval != 0) {
/* don't know how to recover from bugs with prio inheritance. better just crash. */
read_unlock_irq(&tasklist_lock);
BUG();
}
}
#endif
}
out:
read_unlock_irq(&tasklist_lock);
return retval;
}
long enable_aux_task_owner(struct task_struct *t)
{
long retval = 0;
#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
struct task_struct *leader = t->group_leader;
struct task_struct *hp;
if (!tsk_rt(t)->has_aux_tasks) {
TRACE_CUR("task %s/%d is not an aux owner\n", t->comm, t->pid);
return -1;
}
BUG_ON(!is_realtime(t));
if (binheap_is_in_heap(&tsk_rt(t)->aux_task_owner_node)) {
TRACE_CUR("task %s/%d is already active\n", t->comm, t->pid);
goto out;
}
binheap_add(&tsk_rt(t)->aux_task_owner_node, &tsk_aux(leader)->aux_task_owners,
struct rt_param, aux_task_owner_node);
hp = container_of(
binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
if (hp == t) {
/* we're the new hp */
TRACE_CUR("%s/%d is new hp in group %s/%d.\n", t->comm, t->pid, leader->comm, leader->pid);
retval = aux_tasks_increase_priority(leader,
(tsk_rt(hp)->inh_task)? tsk_rt(hp)->inh_task : hp);
}
out:
#endif
return retval;
}
long disable_aux_task_owner(struct task_struct *t)
{
long retval = 0;
#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
struct task_struct *leader = t->group_leader;
struct task_struct *hp;
struct task_struct *new_hp = NULL;
if (!tsk_rt(t)->has_aux_tasks) {
TRACE_CUR("task %s/%d is not an aux owner\n", t->comm, t->pid);
return -1;
}
BUG_ON(!is_realtime(t));
if (!binheap_is_in_heap(&tsk_rt(t)->aux_task_owner_node)) {
TRACE_CUR("task %s/%d is already not active\n", t->comm, t->pid);
goto out;
}
TRACE_CUR("task %s/%d exiting from group %s/%d.\n", t->comm, t->pid, leader->comm, leader->pid);
hp = container_of(
binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
binheap_delete(&tsk_rt(t)->aux_task_owner_node, &tsk_aux(leader)->aux_task_owners);
if (!binheap_empty(&tsk_aux(leader)->aux_task_owners)) {
new_hp = container_of(
binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
}
if (hp == t && new_hp != t) {
struct task_struct *to_inh = NULL;
TRACE_CUR("%s/%d is no longer hp in group %s/%d.\n", t->comm, t->pid, leader->comm, leader->pid);
if (new_hp) {
to_inh = (tsk_rt(new_hp)->inh_task) ? tsk_rt(new_hp)->inh_task : new_hp;
}
retval = aux_tasks_decrease_priority(leader, to_inh);
}
out:
#endif
return retval;
}
static int aux_task_owner_max_priority_order(struct binheap_node *a,
struct binheap_node *b)
{
struct task_struct *d_a = container_of(binheap_entry(a, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
struct task_struct *d_b = container_of(binheap_entry(b, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
BUG_ON(!d_a);
BUG_ON(!d_b);
return litmus->compare(d_a, d_b);
}
static long __do_enable_aux_tasks(int flags)
{
long retval = 0;
struct task_struct *leader;
struct task_struct *t;
int aux_tasks_added = 0;
leader = current->group_leader;
if (!tsk_aux(leader)->initialized) {
INIT_LIST_HEAD(&tsk_aux(leader)->aux_tasks);
INIT_BINHEAP_HANDLE(&tsk_aux(leader)->aux_task_owners, aux_task_owner_max_priority_order);
tsk_aux(leader)->initialized = 1;
}
if (flags & AUX_FUTURE) {
tsk_aux(leader)->aux_future = 1;
}
t = leader;
do {
if (!tsk_rt(t)->has_aux_tasks && !tsk_rt(t)->is_aux_task) {
/* This may harmlessly reinit unused nodes. TODO: Don't reinit already init nodes. */
/* doesn't hurt to initialize both nodes */
INIT_LIST_HEAD(&tsk_rt(t)->aux_task_node);
INIT_BINHEAP_NODE(&tsk_rt(t)->aux_task_owner_node);
}
TRACE_CUR("Checking task in %s/%d: %s/%d = (p = %llu):\n",
leader->comm, leader->pid, t->comm, t->pid,
tsk_rt(t)->task_params.period);
/* inspect period to see if it is an rt task */
if (tsk_rt(t)->task_params.period == 0) {
if (flags && AUX_CURRENT) {
if (!tsk_rt(t)->is_aux_task) {
int admit_ret;
TRACE_CUR("AUX task in %s/%d: %s/%d:\n", leader->comm, leader->pid, t->comm, t->pid);
admit_ret = admit_aux_task(t);
if (admit_ret == 0) {
/* hasn't been aux_tasks_increase_priorityted into rt. make it a aux. */
tsk_rt(t)->is_aux_task = 1;
aux_tasks_added = 1;
#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
list_add_tail(&tsk_rt(t)->aux_task_node, &tsk_aux(leader)->aux_tasks);
#endif
}
}
else {
TRACE_CUR("AUX task in %s/%d is already set up: %s/%d\n", leader->comm, leader->pid, t->comm, t->pid);
}
}
else {
TRACE_CUR("Not changing thread in %s/%d to AUX task: %s/%d\n", leader->comm, leader->pid, t->comm, t->pid);
}
}
else if (!tsk_rt(t)->is_aux_task) { /* don't let aux tasks get aux tasks of their own */
if (!tsk_rt(t)->has_aux_tasks) {
TRACE_CUR("task in %s/%d: %s/%d:\n", leader->comm, leader->pid, t->comm, t->pid);
tsk_rt(t)->has_aux_tasks = 1;
}
else {
TRACE_CUR("task in %s/%d is already set up: %s/%d\n", leader->comm, leader->pid, t->comm, t->pid);
}
}
t = next_thread(t);
} while(t != leader);
#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
if (aux_tasks_added && !binheap_empty(&tsk_aux(leader)->aux_task_owners)) {
struct task_struct *hp = container_of(
binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
struct task_struct, rt_param);
TRACE_CUR("hp in group: %s/%d\n", hp->comm, hp->pid);
retval = aux_tasks_increase_priority(leader, (tsk_rt(hp)->inh_task)? tsk_rt(hp)->inh_task : hp);
}
#endif
return retval;
}
static long __do_disable_aux_tasks(int flags)
{
long retval = 0;
struct task_struct *leader;
struct task_struct *t;
leader = current->group_leader;
if (flags & AUX_FUTURE) {
tsk_aux(leader)->aux_future = 0;
}
if (flags & AUX_CURRENT) {
t = leader;
do {
if (tsk_rt(t)->is_aux_task) {
TRACE_CUR("%s/%d is an aux task.\n", t->comm, t->pid);
if (is_realtime(t)) {
long temp_retval;
struct sched_param param = { .sched_priority = 0};
TRACE_CUR("%s/%d is real-time. Changing policy to SCHED_NORMAL.\n", t->comm, t->pid);
temp_retval = sched_setscheduler_nocheck(t, SCHED_NORMAL, ¶m);
if (temp_retval != 0) {
TRACE_CUR("error changing policy of %s/%d to SCHED_NORMAL\n", t->comm, t->pid);
if (retval == 0) {
retval = temp_retval;
}
else {
TRACE_CUR("prior error (%d) masks new error (%d)\n", retval, temp_retval);
}
}
}
tsk_rt(t)->is_aux_task = 0;
}
t = next_thread(t);
} while(t != leader);
}
return retval;
}
asmlinkage long sys_set_aux_tasks(int flags)
{
long retval;
read_lock_irq(&tasklist_lock);
if (flags & AUX_ENABLE) {
retval = __do_enable_aux_tasks(flags);
}
else {
retval = __do_disable_aux_tasks(flags);
}
read_unlock_irq(&tasklist_lock);
return retval;
}
#else
asmlinkage long sys_set_aux_tasks(int flags)
{
printk("Unsupported. Recompile with CONFIG_REALTIME_AUX_TASKS.\n");
return -EINVAL;
}
#endif
|