/* * kernel/sched/cpudl.c * * Global CPU deadline management * * Author: Juri Lelli <j.lelli@sssup.it> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; version 2 * of the License. */ #include <linux/gfp.h> #include <linux/kernel.h> #include "cpudeadline.h" static inline int parent(int i) { return (i - 1) >> 1; } static inline int left_child(int i) { return (i << 1) + 1; } static inline int right_child(int i) { return (i << 1) + 2; } static inline int dl_time_before(u64 a, u64 b) { return (s64)(a - b) < 0; } static void cpudl_exchange(struct cpudl *cp, int a, int b) { int cpu_a = cp->elements[a].cpu, cpu_b = cp->elements[b].cpu; swap(cp->elements[a], cp->elements[b]); swap(cp->cpu_to_idx[cpu_a], cp->cpu_to_idx[cpu_b]); } static void cpudl_heapify(struct cpudl *cp, int idx) { int l, r, largest; /* adapted from lib/prio_heap.c */ while(1) { l = left_child(idx); r = right_child(idx); largest = idx; if ((l < cp->size) && dl_time_before(cp->elements[idx].dl, cp->elements[l].dl)) largest = l; if ((r < cp->size) && dl_time_before(cp->elements[largest].dl, cp->elements[r].dl)) largest = r; if (largest == idx) break; /* Push idx down the heap one level and bump one up */ cpudl_exchange(cp, largest, idx); idx = largest; } } static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl) { WARN_ON(idx > num_present_cpus() || idx == IDX_INVALID); if (dl_time_before(new_dl, cp->elements[idx].dl)) { cp->elements[idx].dl = new_dl; cpudl_heapify(cp, idx); } else { cp->elements[idx].dl = new_dl; while (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl, cp->elements[idx].dl)) { cpudl_exchange(cp, idx, parent(idx)); idx = parent(idx); } } } static inline int cpudl_maximum(struct cpudl *cp) { return cp->elements[0].cpu; } /* * cpudl_find - find the best (later-dl) CPU in the system * @cp: the cpudl max-heap context * @p: the task * @later_mask: a mask to fill in with the selected CPUs (or NULL) * * Returns: int - best CPU (heap maximum if suitable) */ int cpudl_find(struct cpudl *cp, struct task_struct *p, struct cpumask *later_mask) { int best_cpu = -1; const struct sched_dl_entity *dl_se = &p->dl; if (later_mask && cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed) && cpumask_and(later_mask, later_mask, cpu_active_mask)) { best_cpu = cpumask_any(later_mask); goto out; } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) && dl_time_before(dl_se->deadline, cp->elements[0].dl)) { best_cpu = cpudl_maximum(cp); if (later_mask) cpumask_set_cpu(best_cpu, later_mask); } out: WARN_ON(best_cpu > num_present_cpus() && best_cpu != -1); return best_cpu; } /* * cpudl_set - update the cpudl max-heap * @cp: the cpudl max-heap context * @cpu: the target cpu * @dl: the new earliest deadline for this cpu * * Notes: assumes cpu_rq(cpu)->lock is locked * * Returns: (void) */ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid) { int old_idx, new_cpu; unsigned long flags; WARN_ON(cpu > num_present_cpus()); raw_spin_lock_irqsave(&cp->lock, flags); old_idx = cp->cpu_to_idx[cpu]; if (!is_valid) { /* remove item */ if (old_idx == IDX_INVALID) { /* * Nothing to remove if old_idx was invalid. * This could happen if a rq_offline_dl is * called for a CPU without -dl tasks running. */ goto out; } new_cpu = cp->elements[cp->size - 1].cpu; cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl; cp->elements[old_idx].cpu = new_cpu; cp->size--; cp->cpu_to_idx[new_cpu] = old_idx; cp->cpu_to_idx[cpu] = IDX_INVALID; while (old_idx > 0 && dl_time_before( cp->elements[parent(old_idx)].dl, cp->elements[old_idx].dl)) { cpudl_exchange(cp, old_idx, parent(old_idx)); old_idx = parent(old_idx); } cpumask_set_cpu(cpu, cp->free_cpus); cpudl_heapify(cp, old_idx); goto out; } if (old_idx == IDX_INVALID) { cp->size++; cp->elements[cp->size - 1].dl = 0; cp->elements[cp->size - 1].cpu = cpu; cp->cpu_to_idx[cpu] = cp->size - 1; cpudl_change_key(cp, cp->size - 1, dl); cpumask_clear_cpu(cpu, cp->free_cpus); } else { cpudl_change_key(cp, old_idx, dl); } out: raw_spin_unlock_irqrestore(&cp->lock, flags); } /* * cpudl_init - initialize the cpudl structure * @cp: the cpudl max-heap context */ int cpudl_init(struct cpudl *cp) { int i; memset(cp, 0, sizeof(*cp)); raw_spin_lock_init(&cp->lock); cp->size = 0; for (i = 0; i < NR_CPUS; i++) cp->cpu_to_idx[i] = IDX_INVALID; if (!alloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) return -ENOMEM; cpumask_setall(cp->free_cpus); return 0; } /* * cpudl_cleanup - clean up the cpudl structure * @cp: the cpudl max-heap context */ void cpudl_cleanup(struct cpudl *cp) { /* * nothing to do for the moment */ }