/* * litmus/sched_pfp.c * * Implementation of partitioned fixed-priority scheduling. * Based on PSN-EDF. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include typedef struct { rt_domain_t domain; struct fp_prio_queue ready_queue; int cpu; struct task_struct* scheduled; /* only RT tasks */ /* * scheduling lock slock * protects the domain and serializes scheduling decisions */ #define slock domain.ready_lock } pfp_domain_t; DEFINE_PER_CPU(pfp_domain_t, pfp_domains); pfp_domain_t* pfp_doms[NR_CPUS]; #define local_pfp (&__get_cpu_var(pfp_domains)) #define remote_dom(cpu) (&per_cpu(pfp_domains, cpu).domain) #define remote_pfp(cpu) (&per_cpu(pfp_domains, cpu)) #define task_dom(task) remote_dom(get_partition(task)) #define task_pfp(task) remote_pfp(get_partition(task)) /* we assume the lock is being held */ static void preempt(pfp_domain_t *pfp) { preempt_if_preemptable(pfp->scheduled, pfp->cpu); } static unsigned int priority_index(struct task_struct* t) { #ifdef CONFIG_LOCKING if (unlikely(t->rt_param.inh_task)) /* use effective priority */ t = t->rt_param.inh_task; if (is_priority_boosted(t)) { /* zero is reserved for priority-boosted tasks */ return 0; } else #endif return get_priority(t); } static void pfp_release_jobs(rt_domain_t* rt, struct bheap* tasks) { pfp_domain_t *pfp = container_of(rt, pfp_domain_t, domain); unsigned long flags; struct task_struct* t; struct bheap_node* hn; raw_spin_lock_irqsave(&pfp->slock, flags); while (!bheap_empty(tasks)) { hn = bheap_take(fp_ready_order, tasks); t = bheap2task(hn); TRACE_TASK(t, "released (part:%d prio:%d)\n", get_partition(t), get_priority(t)); fp_prio_add(&pfp->ready_queue, t, priority_index(t)); } /* do we need to preempt? */ if (fp_higher_prio(fp_prio_peek(&pfp->ready_queue), pfp->scheduled)) { TRACE_CUR("preempted by new release\n"); preempt(pfp); } raw_spin_unlock_irqrestore(&pfp->slock, flags); } static void pfp_preempt_check(pfp_domain_t *pfp) { if (fp_higher_prio(fp_prio_peek(&pfp->ready_queue), pfp->scheduled)) preempt(pfp); } static void pfp_domain_init(pfp_domain_t* pfp, int cpu) { fp_domain_init(&pfp->domain, NULL, pfp_release_jobs); pfp->cpu = cpu; pfp->scheduled = NULL; fp_prio_queue_init(&pfp->ready_queue); } static void requeue(struct task_struct* t, pfp_domain_t *pfp) { if (t->state != TASK_RUNNING) TRACE_TASK(t, "requeue: !TASK_RUNNING\n"); set_rt_flags(t, RT_F_RUNNING); if (is_released(t, litmus_clock())) fp_prio_add(&pfp->ready_queue, t, priority_index(t)); else add_release(&pfp->domain, t); /* it has got to wait */ } static void job_completion(struct task_struct* t, int forced) { sched_trace_task_completion(t,forced); TRACE_TASK(t, "job_completion().\n"); set_rt_flags(t, RT_F_SLEEP); prepare_for_next_period(t); } static void pfp_tick(struct task_struct *t) { pfp_domain_t *pfp = local_pfp; /* Check for inconsistency. We don't need the lock for this since * ->scheduled is only changed in schedule, which obviously is not * executing in parallel on this CPU */ BUG_ON(is_realtime(t) && t != pfp->scheduled); if (is_realtime(t) && budget_enforced(t) && budget_exhausted(t)) { if (!is_np(t)) { litmus_reschedule_local(); TRACE("pfp_scheduler_tick: " "%d is preemptable " " => FORCE_RESCHED\n", t->pid); } else if (is_user_np(t)) { TRACE("pfp_scheduler_tick: " "%d is non-preemptable, " "preemption delayed.\n", t->pid); request_exit_np(t); } } } static struct task_struct* pfp_schedule(struct task_struct * prev) { pfp_domain_t* pfp = local_pfp; struct task_struct* next; int out_of_time, sleep, preempt, np, exists, blocks, resched, migrate; raw_spin_lock(&pfp->slock); /* sanity checking * differently from gedf, when a task exits (dead) * pfp->schedule may be null and prev _is_ realtime */ BUG_ON(pfp->scheduled && pfp->scheduled != prev); BUG_ON(pfp->scheduled && !is_realtime(prev)); /* (0) Determine state */ exists = pfp->scheduled != NULL; blocks = exists && !is_running(pfp->scheduled); out_of_time = exists && budget_enforced(pfp->scheduled) && budget_exhausted(pfp->scheduled); np = exists && is_np(pfp->scheduled); sleep = exists && get_rt_flags(pfp->scheduled) == RT_F_SLEEP; migrate = exists && get_partition(pfp->scheduled) != pfp->cpu; preempt = migrate || fp_preemption_needed(&pfp->ready_queue, prev); /* If we need to preempt do so. * The following checks set resched to 1 in case of special * circumstances. */ resched = preempt; /* If a task blocks we have no choice but to reschedule. */ if (blocks) resched = 1; /* Request a sys_exit_np() call if we would like to preempt but cannot. * Multiple calls to request_exit_np() don't hurt. */ if (np && (out_of_time || preempt || sleep)) request_exit_np(pfp->scheduled); /* Any task that is preemptable and either exhausts its execution * budget or wants to sleep completes. We may have to reschedule after * this. */ if (!np && (out_of_time || sleep) && !blocks && !migrate) { job_completion(pfp->scheduled, !sleep); resched = 1; } /* The final scheduling decision. Do we need to switch for some reason? * Switch if we are in RT mode and have no task or if we need to * resched. */ next = NULL; if ((!np || blocks) && (resched || !exists)) { /* When preempting a task that does not block, then * re-insert it into either the ready queue or the * release queue (if it completed). requeue() picks * the appropriate queue. */ if (pfp->scheduled && !blocks && !migrate) requeue(pfp->scheduled, pfp); next = fp_prio_take(&pfp->ready_queue); } else /* Only override Linux scheduler if we have a real-time task * scheduled that needs to continue. */ if (exists) next = prev; if (next) { TRACE_TASK(next, "scheduled at %llu\n", litmus_clock()); set_rt_flags(next, RT_F_RUNNING); } else { TRACE("becoming idle at %llu\n", litmus_clock()); } pfp->scheduled = next; sched_state_task_picked(); raw_spin_unlock(&pfp->slock); return next; } #ifdef CONFIG_LITMUS_LOCKING /* prev is no longer scheduled --- see if it needs to migrate */ static void pfp_finish_switch(struct task_struct *prev) { pfp_domain_t *to; if (is_realtime(prev) && is_running(prev) && get_partition(prev) != smp_processor_id()) { TRACE_TASK(prev, "needs to migrate from P%d to P%d\n", smp_processor_id(), get_partition(prev)); to = task_pfp(prev); raw_spin_lock(&to->slock); TRACE_TASK(prev, "adding to queue on P%d\n", to->cpu); requeue(prev, to); if (fp_preemption_needed(&to->ready_queue, to->scheduled)) preempt(to); raw_spin_unlock(&to->slock); } } #endif /* Prepare a task for running in RT mode */ static void pfp_task_new(struct task_struct * t, int on_rq, int running) { pfp_domain_t* pfp = task_pfp(t); unsigned long flags; TRACE_TASK(t, "P-FP: task new, cpu = %d\n", t->rt_param.task_params.cpu); /* setup job parameters */ release_at(t, litmus_clock()); /* The task should be running in the queue, otherwise signal * code will try to wake it up with fatal consequences. */ raw_spin_lock_irqsave(&pfp->slock, flags); if (running) { /* there shouldn't be anything else running at the time */ BUG_ON(pfp->scheduled); pfp->scheduled = t; } else { requeue(t, pfp); /* maybe we have to reschedule */ pfp_preempt_check(pfp); } raw_spin_unlock_irqrestore(&pfp->slock, flags); } static void pfp_task_wake_up(struct task_struct *task) { unsigned long flags; pfp_domain_t* pfp = task_pfp(task); lt_t now; TRACE_TASK(task, "wake_up at %llu\n", litmus_clock()); raw_spin_lock_irqsave(&pfp->slock, flags); #ifdef CONFIG_LITMUS_LOCKING /* Should only be queued when processing a fake-wake up due to a * migration-related state change. */ if (unlikely(is_queued(task))) { TRACE_TASK(task, "WARNING: waking task still queued. Is this right?\n"); goto out_unlock; } #else BUG_ON(is_queued(task)); #endif now = litmus_clock(); if (is_tardy(task, now) #ifdef CONFIG_LITMUS_LOCKING /* 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. */ && !is_priority_boosted(task) #endif ) { /* new sporadic release */ release_at(task, now); sched_trace_task_release(task); } /* Only add to ready queue if it is not the currently-scheduled * task. This could be the case if a task was woken up concurrently * on a remote CPU before the executing CPU got around to actually * de-scheduling the task, i.e., wake_up() raced with schedule() * and won. Also, don't requeue if it is still queued, which can * happen under the DPCP due wake-ups racing with migrations. */ if (pfp->scheduled != task) { requeue(task, pfp); pfp_preempt_check(pfp); } out_unlock: raw_spin_unlock_irqrestore(&pfp->slock, flags); TRACE_TASK(task, "wake up done\n"); } static void pfp_task_block(struct task_struct *t) { /* only running tasks can block, thus t is in no queue */ TRACE_TASK(t, "block at %llu, state=%d\n", litmus_clock(), t->state); BUG_ON(!is_realtime(t)); /* If this task blocked normally, it shouldn't be queued. The exception is * if this is a simulated block()/wakeup() pair from the pull-migration code path. * This should only happen if the DPCP is being used. */ #ifdef CONFIG_LITMUS_LOCKING if (unlikely(is_queued(t))) TRACE_TASK(t, "WARNING: blocking task still queued. Is this right?\n"); #else BUG_ON(is_queued(t)); #endif } static void pfp_task_exit(struct task_struct * t) { unsigned long flags; pfp_domain_t* pfp = task_pfp(t); rt_domain_t* dom; raw_spin_lock_irqsave(&pfp->slock, flags); if (is_queued(t)) { BUG(); /* This currently doesn't work. */ /* dequeue */ dom = task_dom(t); remove(dom, t); } if (pfp->scheduled == t) { pfp->scheduled = NULL; preempt(pfp); } TRACE_TASK(t, "RIP, now reschedule\n"); raw_spin_unlock_irqrestore(&pfp->slock, flags); } #ifdef CONFIG_LITMUS_LOCKING #include #include static void fp_dequeue(pfp_domain_t* pfp, struct task_struct* t) { BUG_ON(pfp->scheduled == t && is_queued(t)); if (is_queued(t)) fp_prio_remove(&pfp->ready_queue, t, priority_index(t)); } static void fp_set_prio_inh(pfp_domain_t* pfp, struct task_struct* t, struct task_struct* prio_inh) { int requeue; if (!t || t->rt_param.inh_task == prio_inh) { /* no update required */ if (t) TRACE_TASK(t, "no prio-inh update required\n"); return; } requeue = is_queued(t); TRACE_TASK(t, "prio-inh: is_queued:%d\n", requeue); if (requeue) /* first remove */ fp_dequeue(pfp, t); t->rt_param.inh_task = prio_inh; if (requeue) /* add again to the right queue */ fp_prio_add(&pfp->ready_queue, t, priority_index(t)); } static int effective_agent_priority(int prio) { /* make sure agents have higher priority */ return prio - LITMUS_MAX_PRIORITY; } static lt_t prio_point(int eprio) { /* make sure we have non-negative prio points */ return eprio + LITMUS_MAX_PRIORITY; } static int prio_from_point(lt_t prio_point) { return ((int) prio_point) - LITMUS_MAX_PRIORITY; } static void boost_priority(struct task_struct* t, lt_t priority_point) { unsigned long flags; pfp_domain_t* pfp = task_pfp(t); raw_spin_lock_irqsave(&pfp->slock, flags); TRACE_TASK(t, "priority boosted at %llu\n", litmus_clock()); tsk_rt(t)->priority_boosted = 1; /* tie-break by protocol-specific priority point */ tsk_rt(t)->boost_start_time = priority_point; if (pfp->scheduled != t) { /* holder may be queued: first stop queue changes */ raw_spin_lock(&pfp->domain.release_lock); if (is_queued(t) && /* If it is queued, then we need to re-order. */ bheap_decrease(fp_ready_order, tsk_rt(t)->heap_node) && /* If we bubbled to the top, then we need to check for preemptions. */ fp_preemption_needed(&pfp->ready_queue, pfp->scheduled)) preempt(pfp); raw_spin_unlock(&pfp->domain.release_lock); } /* else: nothing to do since the job is not queued while scheduled */ raw_spin_unlock_irqrestore(&pfp->slock, flags); } static void unboost_priority(struct task_struct* t) { unsigned long flags; pfp_domain_t* pfp = task_pfp(t); lt_t now; raw_spin_lock_irqsave(&pfp->slock, flags); now = litmus_clock(); /* assumption: this only happens when the job is scheduled */ BUG_ON(pfp->scheduled != t); TRACE_TASK(t, "priority restored at %llu\n", now); /* priority boosted jobs must be scheduled */ BUG_ON(pfp->scheduled != t); tsk_rt(t)->priority_boosted = 0; tsk_rt(t)->boost_start_time = 0; /* check if this changes anything */ if (fp_preemption_needed(&pfp->ready_queue, pfp->scheduled)) preempt(pfp); raw_spin_unlock_irqrestore(&pfp->slock, flags); } /* ******************** SRP support ************************ */ static unsigned int pfp_get_srp_prio(struct task_struct* t) { return get_priority(t); } /* ******************** FMLP support ********************** */ struct fmlp_semaphore { struct litmus_lock litmus_lock; /* current resource holder */ struct task_struct *owner; /* 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); } int pfp_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; lt_t time_of_request; if (!is_realtime(t)) return -EPERM; spin_lock_irqsave(&sem->wait.lock, flags); /* tie-break by this point in time */ time_of_request = litmus_clock(); /* Priority-boost ourself *before* we suspend so that * our priority is boosted when we resume. */ boost_priority(t, time_of_request); 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); 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 pfp_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; } /* we lose the benefit of priority boosting */ unboost_priority(t); /* 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; /* Wake up next. The waiting job is already priority-boosted. */ wake_up_process(next); } else /* resource becomes available */ sem->owner = NULL; out: spin_unlock_irqrestore(&sem->wait.lock, flags); return err; } int pfp_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) pfp_fmlp_unlock(l); return 0; } void pfp_fmlp_free(struct litmus_lock* lock) { kfree(fmlp_from_lock(lock)); } static struct litmus_lock_ops pfp_fmlp_lock_ops = { .close = pfp_fmlp_close, .lock = pfp_fmlp_lock, .unlock = pfp_fmlp_unlock, .deallocate = pfp_fmlp_free, }; static struct litmus_lock* pfp_new_fmlp(void) { struct fmlp_semaphore* sem; sem = kmalloc(sizeof(*sem), GFP_KERNEL); if (!sem) return NULL; sem->owner = NULL; init_waitqueue_head(&sem->wait); sem->litmus_lock.ops = &pfp_fmlp_lock_ops; return &sem->litmus_lock; } /* ******************** MPCP support ********************** */ struct mpcp_semaphore { struct litmus_lock litmus_lock; /* current resource holder */ struct task_struct *owner; /* priority queue of waiting tasks */ wait_queue_head_t wait; /* priority ceiling per cpu */ unsigned int prio_ceiling[NR_CPUS]; /* should jobs spin "virtually" for this resource? */ int vspin; }; #define OMEGA_CEILING UINT_MAX /* Since jobs spin "virtually" while waiting to acquire a lock, * they first must aquire a local per-cpu resource. */ static DEFINE_PER_CPU(wait_queue_head_t, mpcpvs_vspin_wait); static DEFINE_PER_CPU(struct task_struct*, mpcpvs_vspin); /* called with preemptions off <=> no local modifications */ static void mpcp_vspin_enter(void) { struct task_struct* t = current; while (1) { if (__get_cpu_var(mpcpvs_vspin) == NULL) { /* good, we get to issue our request */ __get_cpu_var(mpcpvs_vspin) = t; break; } else { /* some job is spinning => enqueue in request queue */ prio_wait_queue_t wait; wait_queue_head_t* vspin = &__get_cpu_var(mpcpvs_vspin_wait); unsigned long flags; /* ordered by regular priority */ init_prio_waitqueue_entry(&wait, t, prio_point(get_priority(t))); spin_lock_irqsave(&vspin->lock, flags); set_task_state(t, TASK_UNINTERRUPTIBLE); __add_wait_queue_prio_exclusive(vspin, &wait); spin_unlock_irqrestore(&vspin->lock, flags); TS_LOCK_SUSPEND; preempt_enable_no_resched(); schedule(); preempt_disable(); TS_LOCK_RESUME; /* Recheck if we got it --- some higher-priority process might * have swooped in. */ } } /* ok, now it is ours */ } /* called with preemptions off */ static void mpcp_vspin_exit(void) { struct task_struct* t = current, *next; unsigned long flags; wait_queue_head_t* vspin = &__get_cpu_var(mpcpvs_vspin_wait); BUG_ON(__get_cpu_var(mpcpvs_vspin) != t); /* no spinning job */ __get_cpu_var(mpcpvs_vspin) = NULL; /* see if anyone is waiting for us to stop "spinning" */ spin_lock_irqsave(&vspin->lock, flags); next = __waitqueue_remove_first(vspin); if (next) wake_up_process(next); spin_unlock_irqrestore(&vspin->lock, flags); } static inline struct mpcp_semaphore* mpcp_from_lock(struct litmus_lock* lock) { return container_of(lock, struct mpcp_semaphore, litmus_lock); } int pfp_mpcp_lock(struct litmus_lock* l) { struct task_struct* t = current; struct mpcp_semaphore *sem = mpcp_from_lock(l); prio_wait_queue_t wait; unsigned long flags; if (!is_realtime(t)) return -EPERM; preempt_disable(); if (sem->vspin) mpcp_vspin_enter(); /* Priority-boost ourself *before* we suspend so that * our priority is boosted when we resume. Use the priority * ceiling for the local partition. */ boost_priority(t, sem->prio_ceiling[get_partition(t)]); spin_lock_irqsave(&sem->wait.lock, flags); preempt_enable_no_resched(); if (sem->owner) { /* resource is not free => must suspend and wait */ /* ordered by regular priority */ init_prio_waitqueue_entry(&wait, t, prio_point(get_priority(t))); /* FIXME: interruptible would be nice some day */ set_task_state(t, TASK_UNINTERRUPTIBLE); __add_wait_queue_prio_exclusive(&sem->wait, &wait); 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 pfp_mpcp_unlock(struct litmus_lock* l) { struct task_struct *t = current, *next; struct mpcp_semaphore *sem = mpcp_from_lock(l); unsigned long flags; int err = 0; spin_lock_irqsave(&sem->wait.lock, flags); if (sem->owner != t) { err = -EINVAL; goto out; } /* we lose the benefit of priority boosting */ unboost_priority(t); /* 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; /* Wake up next. The waiting job is already priority-boosted. */ wake_up_process(next); } else /* resource becomes available */ sem->owner = NULL; out: spin_unlock_irqrestore(&sem->wait.lock, flags); if (sem->vspin && err == 0) { preempt_disable(); mpcp_vspin_exit(); preempt_enable(); } return err; } int pfp_mpcp_open(struct litmus_lock* l, void* config) { struct task_struct *t = current; struct mpcp_semaphore *sem = mpcp_from_lock(l); int cpu, local_cpu; unsigned long flags; if (!is_realtime(t)) /* we need to know the real-time priority */ return -EPERM; local_cpu = get_partition(t); spin_lock_irqsave(&sem->wait.lock, flags); for (cpu = 0; cpu < NR_CPUS; cpu++) if (cpu != local_cpu) { sem->prio_ceiling[cpu] = min(sem->prio_ceiling[cpu], get_priority(t)); TRACE_CUR("priority ceiling for sem %p is now %d on cpu %d\n", sem, sem->prio_ceiling[cpu], cpu); } spin_unlock_irqrestore(&sem->wait.lock, flags); return 0; } int pfp_mpcp_close(struct litmus_lock* l) { struct task_struct *t = current; struct mpcp_semaphore *sem = mpcp_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) pfp_mpcp_unlock(l); return 0; } void pfp_mpcp_free(struct litmus_lock* lock) { kfree(mpcp_from_lock(lock)); } static struct litmus_lock_ops pfp_mpcp_lock_ops = { .close = pfp_mpcp_close, .lock = pfp_mpcp_lock, .open = pfp_mpcp_open, .unlock = pfp_mpcp_unlock, .deallocate = pfp_mpcp_free, }; static struct litmus_lock* pfp_new_mpcp(int vspin) { struct mpcp_semaphore* sem; int cpu; sem = kmalloc(sizeof(*sem), GFP_KERNEL); if (!sem) return NULL; sem->owner = NULL; init_waitqueue_head(&sem->wait); sem->litmus_lock.ops = &pfp_mpcp_lock_ops; for (cpu = 0; cpu < NR_CPUS; cpu++) sem->prio_ceiling[cpu] = OMEGA_CEILING; /* mark as virtual spinning */ sem->vspin = vspin; return &sem->litmus_lock; } /* ******************** PCP support ********************** */ struct pcp_semaphore { struct litmus_lock litmus_lock; struct list_head ceiling; /* current resource holder */ struct task_struct *owner; /* priority ceiling --- can be negative due to DPCP support */ int prio_ceiling; /* on which processor is this PCP semaphore allocated? */ int on_cpu; }; static inline struct pcp_semaphore* pcp_from_lock(struct litmus_lock* lock) { return container_of(lock, struct pcp_semaphore, litmus_lock); } struct pcp_state { struct list_head system_ceiling; /* highest-priority waiting task */ struct task_struct* hp_waiter; /* list of jobs waiting to get past the system ceiling */ wait_queue_head_t ceiling_blocked; }; static void pcp_init_state(struct pcp_state* s) { INIT_LIST_HEAD(&s->system_ceiling); s->hp_waiter = NULL; init_waitqueue_head(&s->ceiling_blocked); } static DEFINE_PER_CPU(struct pcp_state, pcp_state); /* assumes preemptions are off */ static struct pcp_semaphore* pcp_get_ceiling(void) { struct list_head* top = __get_cpu_var(pcp_state).system_ceiling.next; if (top) return list_entry(top, struct pcp_semaphore, ceiling); else return NULL; } /* assumes preempt off */ static void pcp_add_ceiling(struct pcp_semaphore* sem) { struct list_head *pos; struct list_head *in_use = &__get_cpu_var(pcp_state).system_ceiling; struct pcp_semaphore* held; BUG_ON(sem->on_cpu != smp_processor_id()); BUG_ON(in_list(&sem->ceiling)); list_for_each(pos, in_use) { held = list_entry(pos, struct pcp_semaphore, ceiling); if (held->prio_ceiling >= sem->prio_ceiling) { __list_add(&sem->ceiling, pos->prev, pos); return; } } /* we hit the end of the list */ list_add_tail(&sem->ceiling, in_use); } /* assumes preempt off */ static int pcp_exceeds_ceiling(struct pcp_semaphore* ceiling, struct task_struct* task, int effective_prio) { return ceiling == NULL || ceiling->prio_ceiling > effective_prio || ceiling->owner == task; } /* assumes preempt off */ static void pcp_priority_inheritance(void) { unsigned long flags; pfp_domain_t* pfp = local_pfp; struct pcp_semaphore* ceiling = pcp_get_ceiling(); struct task_struct *blocker, *blocked; blocker = ceiling ? ceiling->owner : NULL; blocked = __get_cpu_var(pcp_state).hp_waiter; raw_spin_lock_irqsave(&pfp->slock, flags); /* Current is no longer inheriting anything by default. This should be * the currently scheduled job, and hence not currently queued. */ BUG_ON(current != pfp->scheduled); fp_set_prio_inh(pfp, current, NULL); fp_set_prio_inh(pfp, blocked, NULL); fp_set_prio_inh(pfp, blocker, NULL); /* Let blocking job inherit priority of blocked job, if required. */ if (blocker && blocked && fp_higher_prio(blocked, blocker)) { TRACE_TASK(blocker, "PCP inherits from %s/%d (prio %u -> %u) \n", blocked->comm, blocked->pid, get_priority(blocker), get_priority(blocked)); fp_set_prio_inh(pfp, blocker, blocked); } /* check if anything changed */ if (fp_higher_prio(fp_prio_peek(&pfp->ready_queue), pfp->scheduled)) preempt(pfp); raw_spin_unlock_irqrestore(&pfp->slock, flags); } /* called with preemptions off */ static void pcp_raise_ceiling(struct pcp_semaphore* sem, int effective_prio) { struct task_struct* t = current; struct pcp_semaphore* ceiling; prio_wait_queue_t wait; unsigned int waiting_higher_prio; do { ceiling = pcp_get_ceiling(); if (pcp_exceeds_ceiling(ceiling, t, effective_prio)) break; TRACE_CUR("PCP ceiling-blocked, wanted sem %p, but %s/%d has the ceiling \n", sem, ceiling->owner->comm, ceiling->owner->pid); /* we need to wait until the ceiling is lowered */ /* enqueue in priority order */ init_prio_waitqueue_entry(&wait, t, prio_point(effective_prio)); set_task_state(t, TASK_UNINTERRUPTIBLE); waiting_higher_prio = add_wait_queue_prio_exclusive( &__get_cpu_var(pcp_state).ceiling_blocked, &wait); if (waiting_higher_prio == 0) { TRACE_CUR("PCP new highest-prio waiter => prio inheritance\n"); /* we are the new highest-priority waiting job * => update inheritance */ __get_cpu_var(pcp_state).hp_waiter = t; pcp_priority_inheritance(); } TS_LOCK_SUSPEND; preempt_enable_no_resched(); schedule(); preempt_disable(); /* pcp_resume_unblocked() removed us from wait queue */ TS_LOCK_RESUME; } while(1); TRACE_CUR("PCP got the ceiling and sem %p\n", sem); /* We are good to go. The semaphore should be available. */ BUG_ON(sem->owner != NULL); sem->owner = t; pcp_add_ceiling(sem); } static void pcp_resume_unblocked(void) { wait_queue_head_t *blocked = &__get_cpu_var(pcp_state).ceiling_blocked; unsigned long flags; prio_wait_queue_t* q; struct task_struct* t = NULL; struct pcp_semaphore* ceiling = pcp_get_ceiling(); spin_lock_irqsave(&blocked->lock, flags); while (waitqueue_active(blocked)) { /* check first == highest-priority waiting job */ q = list_entry(blocked->task_list.next, prio_wait_queue_t, wq.task_list); t = (struct task_struct*) q->wq.private; /* can it proceed now? => let it go */ if (pcp_exceeds_ceiling(ceiling, t, prio_from_point(q->priority))) { __remove_wait_queue(blocked, &q->wq); wake_up_process(t); } else { /* We are done. Update highest-priority waiter. */ __get_cpu_var(pcp_state).hp_waiter = t; goto out; } } /* If we get here, then there are no more waiting * jobs. */ __get_cpu_var(pcp_state).hp_waiter = NULL; out: spin_unlock_irqrestore(&blocked->lock, flags); } /* assumes preempt off */ static void pcp_lower_ceiling(struct pcp_semaphore* sem) { BUG_ON(!in_list(&sem->ceiling)); BUG_ON(sem->owner != current); BUG_ON(sem->on_cpu != smp_processor_id()); /* remove from ceiling list */ list_del(&sem->ceiling); /* release */ sem->owner = NULL; TRACE_CUR("PCP released sem %p\n", sem); /* Wake up all ceiling-blocked jobs that now pass the ceiling. */ pcp_resume_unblocked(); pcp_priority_inheritance(); } static void pcp_update_prio_ceiling(struct pcp_semaphore* sem, int effective_prio) { /* This needs to be synchronized on something. * Might as well use waitqueue lock for the processor. * We assume this happens only before the task set starts execution, * (i.e., during initialization), but it may happen on multiple processors * at the same time. */ unsigned long flags; struct pcp_state* s = &per_cpu(pcp_state, sem->on_cpu); spin_lock_irqsave(&s->ceiling_blocked.lock, flags); sem->prio_ceiling = min(sem->prio_ceiling, effective_prio); spin_unlock_irqrestore(&s->ceiling_blocked.lock, flags); } static void pcp_init_semaphore(struct pcp_semaphore* sem, int cpu) { sem->owner = NULL; INIT_LIST_HEAD(&sem->ceiling); sem->prio_ceiling = INT_MAX; sem->on_cpu = cpu; } int pfp_pcp_lock(struct litmus_lock* l) { struct task_struct* t = current; struct pcp_semaphore *sem = pcp_from_lock(l); int eprio = effective_agent_priority(get_priority(t)); int from = get_partition(t); int to = sem->on_cpu; if (!is_realtime(t) || from != to) return -EPERM; preempt_disable(); pcp_raise_ceiling(sem, eprio); preempt_enable(); return 0; } int pfp_pcp_unlock(struct litmus_lock* l) { struct task_struct *t = current; struct pcp_semaphore *sem = pcp_from_lock(l); int err = 0; preempt_disable(); if (sem->on_cpu != smp_processor_id() || sem->owner != t) { err = -EINVAL; goto out; } /* give it back */ pcp_lower_ceiling(sem); out: preempt_enable(); return err; } int pfp_pcp_open(struct litmus_lock* l, void* __user config) { struct task_struct *t = current; struct pcp_semaphore *sem = pcp_from_lock(l); int cpu, eprio; if (!is_realtime(t)) /* we need to know the real-time priority */ return -EPERM; if (get_user(cpu, (int*) config)) return -EFAULT; /* make sure the resource location matches */ if (cpu != sem->on_cpu) return -EINVAL; eprio = effective_agent_priority(get_priority(t)); pcp_update_prio_ceiling(sem, eprio); return 0; } int pfp_pcp_close(struct litmus_lock* l) { struct task_struct *t = current; struct pcp_semaphore *sem = pcp_from_lock(l); int owner = 0; preempt_disable(); if (sem->on_cpu == smp_processor_id()) owner = sem->owner == t; preempt_enable(); if (owner) pfp_pcp_unlock(l); return 0; } void pfp_pcp_free(struct litmus_lock* lock) { kfree(pcp_from_lock(lock)); } static struct litmus_lock_ops pfp_pcp_lock_ops = { .close = pfp_pcp_close, .lock = pfp_pcp_lock, .open = pfp_pcp_open, .unlock = pfp_pcp_unlock, .deallocate = pfp_pcp_free, }; static struct litmus_lock* pfp_new_pcp(int on_cpu) { struct pcp_semaphore* sem; sem = kmalloc(sizeof(*sem), GFP_KERNEL); if (!sem) return NULL; sem->litmus_lock.ops = &pfp_pcp_lock_ops; pcp_init_semaphore(sem, on_cpu); return &sem->litmus_lock; } /* ******************** DPCP support ********************** */ struct dpcp_semaphore { struct litmus_lock litmus_lock; struct pcp_semaphore pcp; int owner_cpu; }; static inline struct dpcp_semaphore* dpcp_from_lock(struct litmus_lock* lock) { return container_of(lock, struct dpcp_semaphore, litmus_lock); } /* called with preemptions disabled */ static void pfp_migrate_to(int target_cpu) { struct task_struct* t = current; pfp_domain_t *from; if (get_partition(t) == target_cpu) return; /* make sure target_cpu makes sense */ BUG_ON(!cpu_online(target_cpu)); local_irq_disable(); /* scheduled task should not be in any ready or release queue */ BUG_ON(is_queued(t)); /* lock both pfp domains in order of address */ from = task_pfp(t); raw_spin_lock(&from->slock); /* switch partitions */ tsk_rt(t)->task_params.cpu = target_cpu; raw_spin_unlock(&from->slock); /* Don't trace scheduler costs as part of * locking overhead. Scheduling costs are accounted for * explicitly. */ TS_LOCK_SUSPEND; local_irq_enable(); preempt_enable_no_resched(); /* deschedule to be migrated */ schedule(); /* we are now on the target processor */ preempt_disable(); /* start recording costs again */ TS_LOCK_RESUME; BUG_ON(smp_processor_id() != target_cpu); } int pfp_dpcp_lock(struct litmus_lock* l) { struct task_struct* t = current; struct dpcp_semaphore *sem = dpcp_from_lock(l); int eprio = effective_agent_priority(get_priority(t)); int from = get_partition(t); int to = sem->pcp.on_cpu; if (!is_realtime(t)) return -EPERM; preempt_disable(); /* Priority-boost ourself *before* we suspend so that * our priority is boosted when we resume. */ boost_priority(t, get_priority(t)); pfp_migrate_to(to); pcp_raise_ceiling(&sem->pcp, eprio); /* yep, we got it => execute request */ sem->owner_cpu = from; preempt_enable(); return 0; } int pfp_dpcp_unlock(struct litmus_lock* l) { struct task_struct *t = current; struct dpcp_semaphore *sem = dpcp_from_lock(l); int err = 0; int home; preempt_disable(); if (sem->pcp.on_cpu != smp_processor_id() || sem->pcp.owner != t) { err = -EINVAL; goto out; } home = sem->owner_cpu; /* give it back */ pcp_lower_ceiling(&sem->pcp); /* we lose the benefit of priority boosting */ unboost_priority(t); pfp_migrate_to(home); out: preempt_enable(); return err; } int pfp_dpcp_open(struct litmus_lock* l, void* __user config) { struct task_struct *t = current; struct dpcp_semaphore *sem = dpcp_from_lock(l); int cpu, eprio; if (!is_realtime(t)) /* we need to know the real-time priority */ return -EPERM; if (get_user(cpu, (int*) config)) return -EFAULT; /* make sure the resource location matches */ if (cpu != sem->pcp.on_cpu) return -EINVAL; eprio = effective_agent_priority(get_priority(t)); pcp_update_prio_ceiling(&sem->pcp, eprio); return 0; } int pfp_dpcp_close(struct litmus_lock* l) { struct task_struct *t = current; struct dpcp_semaphore *sem = dpcp_from_lock(l); int owner = 0; preempt_disable(); if (sem->pcp.on_cpu == smp_processor_id()) owner = sem->pcp.owner == t; preempt_enable(); if (owner) pfp_dpcp_unlock(l); return 0; } void pfp_dpcp_free(struct litmus_lock* lock) { kfree(dpcp_from_lock(lock)); } static struct litmus_lock_ops pfp_dpcp_lock_ops = { .close = pfp_dpcp_close, .lock = pfp_dpcp_lock, .open = pfp_dpcp_open, .unlock = pfp_dpcp_unlock, .deallocate = pfp_dpcp_free, }; static struct litmus_lock* pfp_new_dpcp(int on_cpu) { struct dpcp_semaphore* sem; sem = kmalloc(sizeof(*sem), GFP_KERNEL); if (!sem) return NULL; sem->litmus_lock.ops = &pfp_dpcp_lock_ops; sem->owner_cpu = NO_CPU; pcp_init_semaphore(&sem->pcp, on_cpu); return &sem->litmus_lock; } /* **** lock constructor **** */ static long pfp_allocate_lock(struct litmus_lock **lock, int type, void* __user config) { int err = -ENXIO, cpu; struct srp_semaphore* srp; /* P-FP currently supports the SRP for local resources and the FMLP * for global resources. */ switch (type) { case FMLP_SEM: /* FIFO Mutex Locking Protocol */ *lock = pfp_new_fmlp(); if (*lock) err = 0; else err = -ENOMEM; break; case MPCP_SEM: /* Multiprocesor Priority Ceiling Protocol */ *lock = pfp_new_mpcp(0); if (*lock) err = 0; else err = -ENOMEM; break; case MPCP_VS_SEM: /* Multiprocesor Priority Ceiling Protocol with virtual spinning */ *lock = pfp_new_mpcp(1); if (*lock) err = 0; else err = -ENOMEM; break; case DPCP_SEM: /* Distributed Priority Ceiling Protocol */ if (get_user(cpu, (int*) config)) return -EFAULT; if (!cpu_online(cpu)) return -EINVAL; *lock = pfp_new_dpcp(cpu); if (*lock) err = 0; else err = -ENOMEM; break; case SRP_SEM: /* Baker's Stack Resource Policy */ srp = allocate_srp_semaphore(); if (srp) { *lock = &srp->litmus_lock; err = 0; } else err = -ENOMEM; break; case PCP_SEM: /* Priority Ceiling Protocol */ if (get_user(cpu, (int*) config)) return -EFAULT; if (!cpu_online(cpu)) return -EINVAL; *lock = pfp_new_pcp(cpu); if (*lock) err = 0; else err = -ENOMEM; break; }; return err; } #endif static long pfp_admit_task(struct task_struct* tsk) { if (task_cpu(tsk) == tsk->rt_param.task_params.cpu && #ifdef CONFIG_RELEASE_MASTER /* don't allow tasks on release master CPU */ task_cpu(tsk) != remote_dom(task_cpu(tsk))->release_master && #endif litmus_is_valid_fixed_prio(get_priority(tsk))) return 0; else return -EINVAL; } static long pfp_activate_plugin(void) { #if defined(CONFIG_RELEASE_MASTER) || defined(CONFIG_LITMUS_LOCKING) int cpu; #endif #ifdef CONFIG_RELEASE_MASTER for_each_online_cpu(cpu) { remote_dom(cpu)->release_master = atomic_read(&release_master_cpu); } #endif #ifdef CONFIG_LITMUS_LOCKING get_srp_prio = pfp_get_srp_prio; for_each_online_cpu(cpu) { init_waitqueue_head(&per_cpu(mpcpvs_vspin_wait, cpu)); per_cpu(mpcpvs_vspin, cpu) = NULL; pcp_init_state(&per_cpu(pcp_state, cpu)); pfp_doms[cpu] = remote_pfp(cpu); } #endif return 0; } /* Plugin object */ static struct sched_plugin pfp_plugin __cacheline_aligned_in_smp = { .plugin_name = "P-FP", .tick = pfp_tick, .task_new = pfp_task_new, .complete_job = complete_job, .task_exit = pfp_task_exit, .schedule = pfp_schedule, .task_wake_up = pfp_task_wake_up, .task_block = pfp_task_block, .admit_task = pfp_admit_task, .activate_plugin = pfp_activate_plugin, #ifdef CONFIG_LITMUS_LOCKING .allocate_lock = pfp_allocate_lock, .finish_switch = pfp_finish_switch, #endif }; static int __init init_pfp(void) { int i; /* We do not really want to support cpu hotplug, do we? ;) * However, if we are so crazy to do so, * we cannot use num_online_cpu() */ for (i = 0; i < num_online_cpus(); i++) { pfp_domain_init(remote_pfp(i), i); } return register_sched_plugin(&pfp_plugin); } module_init(init_pfp);