/* * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include /* 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); } } /* 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); if (last->linked) requeue(last->linked); 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. * Do not unlink since entry->scheduled is currently in the ready queue. * We don't process out_of_time and sleep until the job is preemptive again. */ if (np && (out_of_time || preempt || sleep)) { 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 /* 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; 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 * 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(); } } } static void set_priority_inheritance(struct task_struct* t, struct task_struct* prio_inh) { raw_spin_lock(&gsnedf_lock); __set_priority_inheritance(t, prio_inh); raw_spin_unlock(&gsnedf_lock); } static void __clear_priority_inheritance(struct task_struct* t) { /* 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); } /* set and clear at the same time to avoid having to * acquire the runqueue lock twice */ static void update_priority_inheritance( struct task_struct* deprived, struct task_struct* blocker, struct task_struct* blocked) { /* things to do: * 1) deprived no longer inherits anything. * 2) blocker gets blocked's priority. */ raw_spin_lock(&gsnedf_lock); if (tsk_rt(deprived)->inh_task) __clear_priority_inheritance(deprived); if (blocked) __set_priority_inheritance(blocker, blocked); 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); } TS_LOCK_SUSPEND; /* 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(); TS_LOCK_RESUME; /* 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, *blocked = NULL; 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. */ blocked = 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 || blocked) update_priority_inheritance(t, next, blocked); 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; } /* ******************** OMLP support ********************** */ /* struct for semaphore with priority inheritance */ struct omlp_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 fifo_wait; /* Priority queue of waiting tasks */ wait_queue_head_t prio_wait; /* How many slots remaining in FIFO queue? */ unsigned int num_free; }; static inline struct omlp_semaphore* omlp_from_lock(struct litmus_lock* lock) { return container_of(lock, struct omlp_semaphore, litmus_lock); } /* already locked */ static void omlp_enqueue(struct omlp_semaphore *sem, prio_wait_queue_t* wait) { if (sem->num_free) { /* there is space in the FIFO queue */ sem->num_free--; __add_wait_queue_tail_exclusive(&sem->fifo_wait, &wait->wq); } else { /* nope, gotta go to the priority queue */ __add_wait_queue_prio_exclusive(&sem->prio_wait, wait); } } /* already locked */ static int omlp_move(struct omlp_semaphore *sem) { struct list_head* first; if (waitqueue_active(&sem->prio_wait)) { first = sem->prio_wait.task_list.next; list_move_tail(first, &sem->fifo_wait.task_list); return 1; } else return 0; } static struct task_struct* omlp_dequeue(struct omlp_semaphore *sem) { struct task_struct* first = __waitqueue_remove_first(&sem->fifo_wait); if (first && !omlp_move(sem)) sem->num_free++; return first; } /* caller is responsible for locking */ static struct task_struct* omlp_find_hp_waiter(struct omlp_semaphore *sem, struct task_struct* skip) { struct list_head *pos; struct task_struct *queued, *found = NULL; /* check FIFO queue first */ list_for_each(pos, &sem->fifo_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; } /* check priority queue next */ if (waitqueue_active(&sem->prio_wait)) { /* first has highest priority */ pos = sem->prio_wait.task_list.next; queued = (struct task_struct*) list_entry(pos, wait_queue_t, task_list)->private; if (edf_higher_prio(queued, found)) found = queued; } return found; } int gsnedf_omlp_lock(struct litmus_lock* l) { struct task_struct* t = current; struct omlp_semaphore *sem = omlp_from_lock(l); prio_wait_queue_t wait; unsigned long flags; if (!is_realtime(t)) return -EPERM; spin_lock_irqsave(&sem->fifo_wait.lock, flags); if (sem->owner) { /* resource is not free => must suspend and wait */ init_prio_waitqueue_entry(&wait, t, get_deadline(t)); set_task_state(t, TASK_UNINTERRUPTIBLE); omlp_enqueue(sem, &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); } TS_LOCK_SUSPEND; /* release lock before sleeping */ spin_unlock_irqrestore(&sem->fifo_wait.lock, flags); schedule(); TS_LOCK_RESUME; /* 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->fifo_wait.lock, flags); } return 0; } static int gsnedf_omlp_unlock(struct litmus_lock* l) { struct task_struct *t = current, *next, *blocked = NULL; struct omlp_semaphore *sem = omlp_from_lock(l); unsigned long flags; int err = 0; spin_lock_irqsave(&sem->fifo_wait.lock, flags); if (sem->owner != t) { err = -EINVAL; goto out; } /* check if there are jobs waiting for this resource */ next = omlp_dequeue(sem); 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 = omlp_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. */ blocked = 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 || blocked) update_priority_inheritance(t, next, blocked); out: spin_unlock_irqrestore(&sem->fifo_wait.lock, flags); return err; } static int gsnedf_omlp_close(struct litmus_lock* l) { struct task_struct *t = current; struct omlp_semaphore *sem = omlp_from_lock(l); unsigned long flags; int owner; spin_lock_irqsave(&sem->fifo_wait.lock, flags); owner = sem->owner == t; spin_unlock_irqrestore(&sem->fifo_wait.lock, flags); if (owner) gsnedf_omlp_unlock(l); return 0; } static void gsnedf_omlp_free(struct litmus_lock* lock) { kfree(omlp_from_lock(lock)); } static struct litmus_lock_ops gsnedf_omlp_lock_ops = { .close = gsnedf_omlp_close, .lock = gsnedf_omlp_lock, .unlock = gsnedf_omlp_unlock, .deallocate = gsnedf_omlp_free, }; static struct litmus_lock* gsnedf_new_omlp(void) { struct omlp_semaphore* sem; sem = kmalloc(sizeof(*sem), GFP_KERNEL); if (!sem) return NULL; sem->owner = NULL; sem->hp_waiter = NULL; init_waitqueue_head(&sem->fifo_wait); init_waitqueue_head(&sem->prio_wait); sem->litmus_lock.ops = &gsnedf_omlp_lock_ops; /* free = cpus -1 since ->owner is the head and also counted */ sem->num_free = num_online_cpus() - 1; #ifdef CONFIG_RELEASE_MASTER /* If we use dedicated interrupt handling, then there are actually * only m - 1 CPUs around. */ if (gsnedf.release_master != NO_CPU) sem->num_free -= 1; #endif 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; case OMLP_SEM: /* O(m) Multiprocessor Locking Protocol */ *lock = gsnedf_new_omlp(); 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);