/*
* litmus/sched_gsn_edf.c
*
* Implementation of the GSN-EDF scheduling algorithm.
*
* This version uses the simple approach and serializes all scheduling
* decisions by the use of a queue lock. This is probably not the
* best way to do it, but it should suffice for now.
*/
#include <linux/spinlock.h>
#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <litmus/litmus.h>
#include <litmus/jobs.h>
#include <litmus/sched_plugin.h>
#include <litmus/edf_common.h>
#include <litmus/sched_trace.h>
#include <litmus/preempt.h>
#include <litmus/bheap.h>
#ifdef CONFIG_SCHED_CPU_AFFINITY
#include <litmus/affinity.h>
#endif
#include <linux/module.h>
/* Overview of GSN-EDF operations.
*
* For a detailed explanation of GSN-EDF have a look at the FMLP paper. This
* description only covers how the individual operations are implemented in
* LITMUS.
*
* link_task_to_cpu(T, cpu) - Low-level operation to update the linkage
* structure (NOT the actually scheduled
* task). If there is another linked task To
* already it will set To->linked_on = NO_CPU
* (thereby removing its association with this
* CPU). However, it will not requeue the
* previously linked task (if any). It will set
* T's state to RT_F_RUNNING and check whether
* it is already running somewhere else. If T
* is scheduled somewhere else it will link
* it to that CPU instead (and pull the linked
* task to cpu). T may be NULL.
*
* unlink(T) - Unlink removes T from all scheduler data
* structures. If it is linked to some CPU it
* will link NULL to that CPU. If it is
* currently queued in the gsnedf queue it will
* be removed from the rt_domain. It is safe to
* call unlink(T) if T is not linked. T may not
* be NULL.
*
* requeue(T) - Requeue will insert T into the appropriate
* queue. If the system is in real-time mode and
* the T is released already, it will go into the
* ready queue. If the system is not in
* real-time mode is T, then T will go into the
* release queue. If T's release time is in the
* future, it will go into the release
* queue. That means that T's release time/job
* no/etc. has to be updated before requeu(T) is
* called. It is not safe to call requeue(T)
* when T is already queued. T may not be NULL.
*
* gsnedf_job_arrival(T) - This is the catch all function when T enters
* the system after either a suspension or at a
* job release. It will queue T (which means it
* is not safe to call gsnedf_job_arrival(T) if
* T is already queued) and then check whether a
* preemption is necessary. If a preemption is
* necessary it will update the linkage
* accordingly and cause scheduled to be called
* (either with an IPI or need_resched). It is
* safe to call gsnedf_job_arrival(T) if T's
* next job has not been actually released yet
* (releast time in the future). T will be put
* on the release queue in that case.
*
* job_completion(T) - Take care of everything that needs to be done
* to prepare T for its next release and place
* it in the right queue with
* gsnedf_job_arrival().
*
*
* When we now that T is linked to CPU then link_task_to_cpu(NULL, CPU) is
* equivalent to unlink(T). Note that if you unlink a task from a CPU none of
* the functions will automatically propagate pending task from the ready queue
* to a linked task. This is the job of the calling function ( by means of
* __take_ready).
*/
/* cpu_entry_t - maintain the linked and scheduled state
*/
typedef struct {
int cpu;
struct task_struct* linked; /* only RT tasks */
struct task_struct* scheduled; /* only RT tasks */
struct bheap_node* hn;
} cpu_entry_t;
DEFINE_PER_CPU(cpu_entry_t, gsnedf_cpu_entries);
cpu_entry_t* gsnedf_cpus[NR_CPUS];
/* the cpus queue themselves according to priority in here */
static struct bheap_node gsnedf_heap_node[NR_CPUS];
static struct bheap gsnedf_cpu_heap;
static rt_domain_t gsnedf;
#define gsnedf_lock (gsnedf.ready_lock)
/* Uncomment this if you want to see all scheduling decisions in the
* TRACE() log.
#define WANT_ALL_SCHED_EVENTS
*/
static int cpu_lower_prio(struct bheap_node *_a, struct bheap_node *_b)
{
cpu_entry_t *a, *b;
a = _a->value;
b = _b->value;
/* Note that a and b are inverted: we want the lowest-priority CPU at
* the top of the heap.
*/
return edf_higher_prio(b->linked, a->linked);
}
/* update_cpu_position - Move the cpu entry to the correct place to maintain
* order in the cpu queue. Caller must hold gsnedf lock.
*/
static void update_cpu_position(cpu_entry_t *entry)
{
if (likely(bheap_node_in_heap(entry->hn)))
bheap_delete(cpu_lower_prio, &gsnedf_cpu_heap, entry->hn);
bheap_insert(cpu_lower_prio, &gsnedf_cpu_heap, entry->hn);
}
/* caller must hold gsnedf lock */
static cpu_entry_t* lowest_prio_cpu(void)
{
struct bheap_node* hn;
hn = bheap_peek(cpu_lower_prio, &gsnedf_cpu_heap);
return hn->value;
}
/* link_task_to_cpu - Update the link of a CPU.
* Handles the case where the to-be-linked task is already
* scheduled on a different CPU.
*/
static noinline void link_task_to_cpu(struct task_struct* linked,
cpu_entry_t *entry)
{
cpu_entry_t *sched;
struct task_struct* tmp;
int on_cpu;
BUG_ON(linked && !is_realtime(linked));
/* Currently linked task is set to be unlinked. */
if (entry->linked) {
entry->linked->rt_param.linked_on = NO_CPU;
}
/* Link new task to CPU. */
if (linked) {
set_rt_flags(linked, RT_F_RUNNING);
/* handle task is already scheduled somewhere! */
on_cpu = linked->rt_param.scheduled_on;
if (on_cpu != NO_CPU) {
sched = &per_cpu(gsnedf_cpu_entries, on_cpu);
/* this should only happen if not linked already */
BUG_ON(sched->linked == linked);
/* If we are already scheduled on the CPU to which we
* wanted to link, we don't need to do the swap --
* we just link ourselves to the CPU and depend on
* the caller to get things right.
*/
if (entry != sched) {
TRACE_TASK(linked,
"already scheduled on %d, updating link.\n",
sched->cpu);
tmp = sched->linked;
linked->rt_param.linked_on = sched->cpu;
sched->linked = linked;
update_cpu_position(sched);
linked = tmp;
}
}
if (linked) /* might be NULL due to swap */
linked->rt_param.linked_on = entry->cpu;
}
entry->linked = linked;
#ifdef WANT_ALL_SCHED_EVENTS
if (linked)
TRACE_TASK(linked, "linked to %d.\n", entry->cpu);
else
TRACE("NULL linked to %d.\n", entry->cpu);
#endif
update_cpu_position(entry);
}
/* unlink - Make sure a task is not linked any longer to an entry
* where it was linked before. Must hold gsnedf_lock.
*/
static noinline void unlink(struct task_struct* t)
{
cpu_entry_t *entry;
if (t->rt_param.linked_on != NO_CPU) {
/* unlink */
entry = &per_cpu(gsnedf_cpu_entries, t->rt_param.linked_on);
t->rt_param.linked_on = NO_CPU;
link_task_to_cpu(NULL, entry);
} else if (is_queued(t)) {
/* This is an interesting situation: t is scheduled,
* but was just recently unlinked. It cannot be
* linked anywhere else (because then it would have
* been relinked to this CPU), thus it must be in some
* queue. We must remove it from the list in this
* case.
*/
remove(&gsnedf, t);
}
}
/* preempt - force a CPU to reschedule
*/
static void preempt(cpu_entry_t *entry)
{
preempt_if_preemptable(entry->scheduled, entry->cpu);
}
/* requeue - Put an unlinked task into gsn-edf domain.
* Caller must hold gsnedf_lock.
*/
static noinline void requeue(struct task_struct* task)
{
BUG_ON(!task);
/* sanity check before insertion */
BUG_ON(is_queued(task));
if (is_released(task, litmus_clock()))
__add_ready(&gsnedf, task);
else {
/* it has got to wait */
add_release(&gsnedf, task);
}
}
#ifdef CONFIG_SCHED_CPU_AFFINITY
static cpu_entry_t* gsnedf_get_nearest_available_cpu(cpu_entry_t* start)
{
cpu_entry_t* affinity;
get_nearest_available_cpu(affinity, start, gsnedf_cpu_entries,
#ifdef CONFIG_RELEASE_MASTER
gsnedf.release_master
#else
-1
#endif
);
return(affinity);
}
#endif
/* check for any necessary preemptions */
static void check_for_preemptions(void)
{
struct task_struct *task;
cpu_entry_t* last;
for (last = lowest_prio_cpu();
edf_preemption_needed(&gsnedf, last->linked);
last = lowest_prio_cpu()) {
/* preemption necessary */
task = __take_ready(&gsnedf);
TRACE("check_for_preemptions: attempting to link task %d to %d\n",
task->pid, last->cpu);
#ifdef CONFIG_SCHED_CPU_AFFINITY
{
cpu_entry_t* affinity =
gsnedf_get_nearest_available_cpu(
&per_cpu(gsnedf_cpu_entries, task_cpu(task)));
if (affinity)
last = affinity;
else if (last->linked)
requeue(last->linked);
}
#else
if (last->linked)
requeue(last->linked);
#endif
link_task_to_cpu(task, last);
preempt(last);
}
}
/* gsnedf_job_arrival: task is either resumed or released */
static noinline void gsnedf_job_arrival(struct task_struct* task)
{
BUG_ON(!task);
requeue(task);
check_for_preemptions();
}
static void gsnedf_release_jobs(rt_domain_t* rt, struct bheap* tasks)
{
unsigned long flags;
raw_spin_lock_irqsave(&gsnedf_lock, flags);
__merge_ready(rt, tasks);
check_for_preemptions();
raw_spin_unlock_irqrestore(&gsnedf_lock, flags);
}
/* caller holds gsnedf_lock */
static noinline void job_completion(struct task_struct *t, int forced)
{
BUG_ON(!t);
sched_trace_task_completion(t, forced);
TRACE_TASK(t, "job_completion().\n");
/* set flags */
set_rt_flags(t, RT_F_SLEEP);
/* prepare for next period */
prepare_for_next_period(t);
if (is_released(t, litmus_clock()))
sched_trace_task_release(t);
/* unlink */
unlink(t);
/* requeue
* But don't requeue a blocking task. */
if (is_running(t))
gsnedf_job_arrival(t);
}
/* gsnedf_tick - this function is called for every local timer
* interrupt.
*
* checks whether the current task has expired and checks
* whether we need to preempt it if it has not expired
*/
static void gsnedf_tick(struct task_struct* t)
{
if (is_realtime(t) && budget_enforced(t) && budget_exhausted(t)) {
if (!is_np(t)) {
/* np tasks will be preempted when they become
* preemptable again
*/
litmus_reschedule_local();
TRACE("gsnedf_scheduler_tick: "
"%d is preemptable "
" => FORCE_RESCHED\n", t->pid);
} else if (is_user_np(t)) {
TRACE("gsnedf_scheduler_tick: "
"%d is non-preemptable, "
"preemption delayed.\n", t->pid);
request_exit_np(t);
}
}
}
/* Getting schedule() right is a bit tricky. schedule() may not make any
* assumptions on the state of the current task since it may be called for a
* number of reasons. The reasons include a scheduler_tick() determined that it
* was necessary, because sys_exit_np() was called, because some Linux
* subsystem determined so, or even (in the worst case) because there is a bug
* hidden somewhere. Thus, we must take extreme care to determine what the
* current state is.
*
* The CPU could currently be scheduling a task (or not), be linked (or not).
*
* The following assertions for the scheduled task could hold:
*
* - !is_running(scheduled) // the job blocks
* - scheduled->timeslice == 0 // the job completed (forcefully)
* - get_rt_flag() == RT_F_SLEEP // the job completed (by syscall)
* - linked != scheduled // we need to reschedule (for any reason)
* - is_np(scheduled) // rescheduling must be delayed,
* sys_exit_np must be requested
*
* Any of these can occur together.
*/
static struct task_struct* gsnedf_schedule(struct task_struct * prev)
{
cpu_entry_t* entry = &__get_cpu_var(gsnedf_cpu_entries);
int out_of_time, sleep, preempt, np, exists, blocks;
struct task_struct* next = NULL;
#ifdef CONFIG_RELEASE_MASTER
/* Bail out early if we are the release master.
* The release master never schedules any real-time tasks.
*/
if (gsnedf.release_master == entry->cpu) {
sched_state_task_picked();
return NULL;
}
#endif
raw_spin_lock(&gsnedf_lock);
/* sanity checking */
BUG_ON(entry->scheduled && entry->scheduled != prev);
BUG_ON(entry->scheduled && !is_realtime(prev));
BUG_ON(is_realtime(prev) && !entry->scheduled);
/* (0) Determine state */
exists = entry->scheduled != NULL;
blocks = exists && !is_running(entry->scheduled);
out_of_time = exists &&
budget_enforced(entry->scheduled) &&
budget_exhausted(entry->scheduled);
np = exists && is_np(entry->scheduled);
sleep = exists && get_rt_flags(entry->scheduled) == RT_F_SLEEP;
preempt = entry->scheduled != entry->linked;
#ifdef WANT_ALL_SCHED_EVENTS
TRACE_TASK(prev, "invoked gsnedf_schedule.\n");
#endif
if (exists)
TRACE_TASK(prev,
"blocks:%d out_of_time:%d np:%d sleep:%d preempt:%d "
"state:%d sig:%d\n",
blocks, out_of_time, np, sleep, preempt,
prev->state, signal_pending(prev));
if (entry->linked && preempt)
TRACE_TASK(prev, "will be preempted by %s/%d\n",
entry->linked->comm, entry->linked->pid);
/* If a task blocks we have no choice but to reschedule.
*/
if (blocks)
unlink(entry->scheduled);
/* Request a sys_exit_np() call if we would like to preempt but cannot.
* We need to make sure to update the link structure anyway in case
* that we are still linked. Multiple calls to request_exit_np() don't
* hurt.
*/
if (np && (out_of_time || preempt || sleep)) {
unlink(entry->scheduled);
request_exit_np(entry->scheduled);
}
/* Any task that is preemptable and either exhausts its execution
* budget or wants to sleep completes. We may have to reschedule after
* this. Don't do a job completion if we block (can't have timers running
* for blocked jobs). Preemption go first for the same reason.
*/
if (!np && (out_of_time || sleep) && !blocks && !preempt)
job_completion(entry->scheduled, !sleep);
/* Link pending task if we became unlinked.
*/
if (!entry->linked)
link_task_to_cpu(__take_ready(&gsnedf), entry);
/* The final scheduling decision. Do we need to switch for some reason?
* If linked is different from scheduled, then select linked as next.
*/
if ((!np || blocks) &&
entry->linked != entry->scheduled) {
/* Schedule a linked job? */
if (entry->linked) {
entry->linked->rt_param.scheduled_on = entry->cpu;
next = entry->linked;
TRACE_TASK(next, "scheduled_on = P%d\n", smp_processor_id());
}
if (entry->scheduled) {
/* not gonna be scheduled soon */
entry->scheduled->rt_param.scheduled_on = NO_CPU;
TRACE_TASK(entry->scheduled, "scheduled_on = NO_CPU\n");
}
} else
/* Only override Linux scheduler if we have a real-time task
* scheduled that needs to continue.
*/
if (exists)
next = prev;
sched_state_task_picked();
raw_spin_unlock(&gsnedf_lock);
#ifdef WANT_ALL_SCHED_EVENTS
TRACE("gsnedf_lock released, next=0x%p\n", next);
if (next)
TRACE_TASK(next, "scheduled at %llu\n", litmus_clock());
else if (exists && !next)
TRACE("becomes idle at %llu.\n", litmus_clock());
#endif
return next;
}
/* _finish_switch - we just finished the switch away from prev
*/
static void gsnedf_finish_switch(struct task_struct *prev)
{
cpu_entry_t* entry = &__get_cpu_var(gsnedf_cpu_entries);
entry->scheduled = is_realtime(current) ? current : NULL;
#ifdef WANT_ALL_SCHED_EVENTS
TRACE_TASK(prev, "switched away from\n");
#endif
}
/* Prepare a task for running in RT mode
*/
static void gsnedf_task_new(struct task_struct * t, int on_rq, int running)
{
unsigned long flags;
cpu_entry_t* entry;
TRACE("gsn edf: task new %d\n", t->pid);
raw_spin_lock_irqsave(&gsnedf_lock, flags);
/* setup job params */
release_at(t, litmus_clock());
if (running) {
entry = &per_cpu(gsnedf_cpu_entries, task_cpu(t));
BUG_ON(entry->scheduled);
#ifdef CONFIG_RELEASE_MASTER
if (entry->cpu != gsnedf.release_master) {
#endif
entry->scheduled = t;
tsk_rt(t)->scheduled_on = task_cpu(t);
#ifdef CONFIG_RELEASE_MASTER
} else {
/* do not schedule on release master */
preempt(entry); /* force resched */
tsk_rt(t)->scheduled_on = NO_CPU;
}
#endif
} else {
t->rt_param.scheduled_on = NO_CPU;
}
t->rt_param.linked_on = NO_CPU;
gsnedf_job_arrival(t);
raw_spin_unlock_irqrestore(&gsnedf_lock, flags);
}
static void gsnedf_task_wake_up(struct task_struct *task)
{
unsigned long flags;
lt_t now;
TRACE_TASK(task, "wake_up at %llu\n", litmus_clock());
raw_spin_lock_irqsave(&gsnedf_lock, flags);
/* We need to take suspensions because of semaphores into
* account! If a job resumes after being suspended due to acquiring
* a semaphore, it should never be treated as a new job release.
*/
if (get_rt_flags(task) == RT_F_EXIT_SEM) {
set_rt_flags(task, RT_F_RUNNING);
} else {
now = litmus_clock();
if (is_tardy(task, now)) {
/* new sporadic release */
release_at(task, now);
sched_trace_task_release(task);
}
else {
if (task->rt.time_slice) {
/* came back in time before deadline
*/
set_rt_flags(task, RT_F_RUNNING);
}
}
}
gsnedf_job_arrival(task);
raw_spin_unlock_irqrestore(&gsnedf_lock, flags);
}
static void gsnedf_task_block(struct task_struct *t)
{
unsigned long flags;
TRACE_TASK(t, "block at %llu\n", litmus_clock());
/* unlink if necessary */
raw_spin_lock_irqsave(&gsnedf_lock, flags);
unlink(t);
raw_spin_unlock_irqrestore(&gsnedf_lock, flags);
BUG_ON(!is_realtime(t));
}
static void gsnedf_task_exit(struct task_struct * t)
{
unsigned long flags;
/* unlink if necessary */
raw_spin_lock_irqsave(&gsnedf_lock, flags);
unlink(t);
if (tsk_rt(t)->scheduled_on != NO_CPU) {
gsnedf_cpus[tsk_rt(t)->scheduled_on]->scheduled = NULL;
tsk_rt(t)->scheduled_on = NO_CPU;
}
raw_spin_unlock_irqrestore(&gsnedf_lock, flags);
BUG_ON(!is_realtime(t));
TRACE_TASK(t, "RIP\n");
}
static long gsnedf_admit_task(struct task_struct* tsk)
{
return 0;
}
#ifdef CONFIG_LITMUS_LOCKING
#include <litmus/fdso.h>
/* called with IRQs off */
static void set_priority_inheritance(struct task_struct* t, struct task_struct* prio_inh)
{
int linked_on;
int check_preempt = 0;
raw_spin_lock(&gsnedf_lock);
TRACE_TASK(t, "inherits priority from %s/%d\n", prio_inh->comm, prio_inh->pid);
tsk_rt(t)->inh_task = prio_inh;
linked_on = tsk_rt(t)->linked_on;
/* If it is scheduled, then we need to reorder the CPU heap. */
if (linked_on != NO_CPU) {
TRACE_TASK(t, "%s: linked on %d\n",
__FUNCTION__, linked_on);
/* Holder is scheduled; need to re-order CPUs.
* We can't use heap_decrease() here since
* the cpu_heap is ordered in reverse direction, so
* it is actually an increase. */
bheap_delete(cpu_lower_prio, &gsnedf_cpu_heap,
gsnedf_cpus[linked_on]->hn);
bheap_insert(cpu_lower_prio, &gsnedf_cpu_heap,
gsnedf_cpus[linked_on]->hn);
} else {
/* holder may be queued: first stop queue changes */
raw_spin_lock(&gsnedf.release_lock);
if (is_queued(t)) {
TRACE_TASK(t, "%s: is queued\n",
__FUNCTION__);
/* We need to update the position of holder in some
* heap. Note that this could be a release heap if we
* budget enforcement is used and this job overran. */
check_preempt =
!bheap_decrease(edf_ready_order,
tsk_rt(t)->heap_node);
} else {
/* Nothing to do: if it is not queued and not linked
* then it is either sleeping or currently being moved
* by other code (e.g., a timer interrupt handler) that
* will use the correct priority when enqueuing the
* task. */
TRACE_TASK(t, "%s: is NOT queued => Done.\n",
__FUNCTION__);
}
raw_spin_unlock(&gsnedf.release_lock);
/* If holder was enqueued in a release heap, then the following
* preemption check is pointless, but we can't easily detect
* that case. If you want to fix this, then consider that
* simply adding a state flag requires O(n) time to update when
* releasing n tasks, which conflicts with the goal to have
* O(log n) merges. */
if (check_preempt) {
/* heap_decrease() hit the top level of the heap: make
* sure preemption checks get the right task, not the
* potentially stale cache. */
bheap_uncache_min(edf_ready_order,
&gsnedf.ready_queue);
check_for_preemptions();
}
}
raw_spin_unlock(&gsnedf_lock);
}
/* called with IRQs off */
static void clear_priority_inheritance(struct task_struct* t)
{
raw_spin_lock(&gsnedf_lock);
/* A job only stops inheriting a priority when it releases a
* resource. Thus we can make the following assumption.*/
BUG_ON(tsk_rt(t)->scheduled_on == NO_CPU);
TRACE_TASK(t, "priority restored\n");
tsk_rt(t)->inh_task = NULL;
/* Check if rescheduling is necessary. We can't use heap_decrease()
* since the priority was effectively lowered. */
unlink(t);
gsnedf_job_arrival(t);
raw_spin_unlock(&gsnedf_lock);
}
/* ******************** FMLP support ********************** */
/* struct for semaphore with priority inheritance */
struct fmlp_semaphore {
struct litmus_lock litmus_lock;
/* current resource holder */
struct task_struct *owner;
/* highest-priority waiter */
struct task_struct *hp_waiter;
/* FIFO queue of waiting tasks */
wait_queue_head_t wait;
};
static inline struct fmlp_semaphore* fmlp_from_lock(struct litmus_lock* lock)
{
return container_of(lock, struct fmlp_semaphore, litmus_lock);
}
/* caller is responsible for locking */
struct task_struct* find_hp_waiter(struct fmlp_semaphore *sem,
struct task_struct* skip)
{
struct list_head *pos;
struct task_struct *queued, *found = NULL;
list_for_each(pos, &sem->wait.task_list) {
queued = (struct task_struct*) list_entry(pos, wait_queue_t,
task_list)->private;
/* Compare task prios, find high prio task. */
if (queued != skip && edf_higher_prio(queued, found))
found = queued;
}
return found;
}
int gsnedf_fmlp_lock(struct litmus_lock* l)
{
struct task_struct* t = current;
struct fmlp_semaphore *sem = fmlp_from_lock(l);
wait_queue_t wait;
unsigned long flags;
if (!is_realtime(t))
return -EPERM;
spin_lock_irqsave(&sem->wait.lock, flags);
if (sem->owner) {
/* resource is not free => must suspend and wait */
init_waitqueue_entry(&wait, t);
/* FIXME: interruptible would be nice some day */
set_task_state(t, TASK_UNINTERRUPTIBLE);
__add_wait_queue_tail_exclusive(&sem->wait, &wait);
/* check if we need to activate priority inheritance */
if (edf_higher_prio(t, sem->hp_waiter)) {
sem->hp_waiter = t;
if (edf_higher_prio(t, sem->owner))
set_priority_inheritance(sem->owner, sem->hp_waiter);
}
/* release lock before sleeping */
spin_unlock_irqrestore(&sem->wait.lock, flags);
/* We depend on the FIFO order. Thus, we don't need to recheck
* when we wake up; we are guaranteed to have the lock since
* there is only one wake up per release.
*/
schedule();
/* Since we hold the lock, no other task will change
* ->owner. We can thus check it without acquiring the spin
* lock. */
BUG_ON(sem->owner != t);
} else {
/* it's ours now */
sem->owner = t;
spin_unlock_irqrestore(&sem->wait.lock, flags);
}
return 0;
}
int gsnedf_fmlp_unlock(struct litmus_lock* l)
{
struct task_struct *t = current, *next;
struct fmlp_semaphore *sem = fmlp_from_lock(l);
unsigned long flags;
int err = 0;
spin_lock_irqsave(&sem->wait.lock, flags);
if (sem->owner != t) {
err = -EINVAL;
goto out;
}
/* check if there are jobs waiting for this resource */
next = __waitqueue_remove_first(&sem->wait);
if (next) {
/* next becomes the resouce holder */
sem->owner = next;
TRACE_CUR("lock ownership passed to %s/%d\n", next->comm, next->pid);
/* determine new hp_waiter if necessary */
if (next == sem->hp_waiter) {
TRACE_TASK(next, "was highest-prio waiter\n");
/* next has the highest priority --- it doesn't need to
* inherit. However, we need to make sure that the
* next-highest priority in the queue is reflected in
* hp_waiter. */
sem->hp_waiter = find_hp_waiter(sem, next);
if (sem->hp_waiter)
TRACE_TASK(sem->hp_waiter, "is new highest-prio waiter\n");
else
TRACE("no further waiters\n");
} else {
/* Well, if next is not the highest-priority waiter,
* then it ought to inherit the highest-priority
* waiter's priority. */
set_priority_inheritance(next, sem->hp_waiter);
}
/* wake up next */
wake_up_process(next);
} else
/* becomes available */
sem->owner = NULL;
/* we lose the benefit of priority inheritance (if any) */
if (tsk_rt(t)->inh_task)
clear_priority_inheritance(t);
out:
spin_unlock_irqrestore(&sem->wait.lock, flags);
return err;
}
int gsnedf_fmlp_close(struct litmus_lock* l)
{
struct task_struct *t = current;
struct fmlp_semaphore *sem = fmlp_from_lock(l);
unsigned long flags;
int owner;
spin_lock_irqsave(&sem->wait.lock, flags);
owner = sem->owner == t;
spin_unlock_irqrestore(&sem->wait.lock, flags);
if (owner)
gsnedf_fmlp_unlock(l);
return 0;
}
void gsnedf_fmlp_free(struct litmus_lock* lock)
{
kfree(fmlp_from_lock(lock));
}
static struct litmus_lock_ops gsnedf_fmlp_lock_ops = {
.close = gsnedf_fmlp_close,
.lock = gsnedf_fmlp_lock,
.unlock = gsnedf_fmlp_unlock,
.deallocate = gsnedf_fmlp_free,
};
static struct litmus_lock* gsnedf_new_fmlp(void)
{
struct fmlp_semaphore* sem;
sem = kmalloc(sizeof(*sem), GFP_KERNEL);
if (!sem)
return NULL;
sem->owner = NULL;
sem->hp_waiter = NULL;
init_waitqueue_head(&sem->wait);
sem->litmus_lock.ops = &gsnedf_fmlp_lock_ops;
return &sem->litmus_lock;
}
/* **** lock constructor **** */
static long gsnedf_allocate_lock(struct litmus_lock **lock, int type,
void* __user unused)
{
int err = -ENXIO;
/* GSN-EDF currently only supports the FMLP for global resources. */
switch (type) {
case FMLP_SEM:
/* Flexible Multiprocessor Locking Protocol */
*lock = gsnedf_new_fmlp();
if (*lock)
err = 0;
else
err = -ENOMEM;
break;
};
return err;
}
#endif
static long gsnedf_activate_plugin(void)
{
int cpu;
cpu_entry_t *entry;
bheap_init(&gsnedf_cpu_heap);
#ifdef CONFIG_RELEASE_MASTER
gsnedf.release_master = atomic_read(&release_master_cpu);
#endif
for_each_online_cpu(cpu) {
entry = &per_cpu(gsnedf_cpu_entries, cpu);
bheap_node_init(&entry->hn, entry);
entry->linked = NULL;
entry->scheduled = NULL;
#ifdef CONFIG_RELEASE_MASTER
if (cpu != gsnedf.release_master) {
#endif
TRACE("GSN-EDF: Initializing CPU #%d.\n", cpu);
update_cpu_position(entry);
#ifdef CONFIG_RELEASE_MASTER
} else {
TRACE("GSN-EDF: CPU %d is release master.\n", cpu);
}
#endif
}
return 0;
}
/* Plugin object */
static struct sched_plugin gsn_edf_plugin __cacheline_aligned_in_smp = {
.plugin_name = "GSN-EDF",
.finish_switch = gsnedf_finish_switch,
.tick = gsnedf_tick,
.task_new = gsnedf_task_new,
.complete_job = complete_job,
.task_exit = gsnedf_task_exit,
.schedule = gsnedf_schedule,
.task_wake_up = gsnedf_task_wake_up,
.task_block = gsnedf_task_block,
.admit_task = gsnedf_admit_task,
.activate_plugin = gsnedf_activate_plugin,
#ifdef CONFIG_LITMUS_LOCKING
.allocate_lock = gsnedf_allocate_lock,
#endif
};
static int __init init_gsn_edf(void)
{
int cpu;
cpu_entry_t *entry;
bheap_init(&gsnedf_cpu_heap);
/* initialize CPU state */
for (cpu = 0; cpu < NR_CPUS; cpu++) {
entry = &per_cpu(gsnedf_cpu_entries, cpu);
gsnedf_cpus[cpu] = entry;
entry->cpu = cpu;
entry->hn = &gsnedf_heap_node[cpu];
bheap_node_init(&entry->hn, entry);
}
edf_domain_init(&gsnedf, NULL, gsnedf_release_jobs);
return register_sched_plugin(&gsn_edf_plugin);
}
module_init(init_gsn_edf);
