1/*
  2 *  kernel/sched/cpudl.c
  3 *
  4 *  Global CPU deadline management
  5 *
  6 *  Author: Juri Lelli <j.lelli@sssup.it>
  7 *
  8 *  This program is free software; you can redistribute it and/or
  9 *  modify it under the terms of the GNU General Public License
 10 *  as published by the Free Software Foundation; version 2
 11 *  of the License.
 12 */
 13
 14#include <linux/gfp.h>
 15#include <linux/kernel.h>
 16#include <linux/slab.h>
 17#include "cpudeadline.h"
 18
 19static inline int parent(int i)
 20{
 21	return (i - 1) >> 1;
 22}
 23
 24static inline int left_child(int i)
 25{
 26	return (i << 1) + 1;
 27}
 28
 29static inline int right_child(int i)
 30{
 31	return (i << 1) + 2;
 32}
 33
 34static void cpudl_exchange(struct cpudl *cp, int a, int b)
 35{
 36	int cpu_a = cp->elements[a].cpu, cpu_b = cp->elements[b].cpu;
 37
 38	swap(cp->elements[a].cpu, cp->elements[b].cpu);
 39	swap(cp->elements[a].dl , cp->elements[b].dl );
 40
 41	swap(cp->elements[cpu_a].idx, cp->elements[cpu_b].idx);
 42}
 43
 44static void cpudl_heapify(struct cpudl *cp, int idx)
 45{
 46	int l, r, largest;
 47
 48	/* adapted from lib/prio_heap.c */
 49	while(1) {
 50		l = left_child(idx);
 51		r = right_child(idx);
 52		largest = idx;
 53
 54		if ((l < cp->size) && dl_time_before(cp->elements[idx].dl,
 55							cp->elements[l].dl))
 56			largest = l;
 57		if ((r < cp->size) && dl_time_before(cp->elements[largest].dl,
 58							cp->elements[r].dl))
 59			largest = r;
 60		if (largest == idx)
 61			break;
 62
 63		/* Push idx down the heap one level and bump one up */
 64		cpudl_exchange(cp, largest, idx);
 65		idx = largest;
 66	}
 67}
 68
 69static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl)
 70{
 71	WARN_ON(idx == IDX_INVALID || !cpu_present(idx));
 72
 73	if (dl_time_before(new_dl, cp->elements[idx].dl)) {
 74		cp->elements[idx].dl = new_dl;
 75		cpudl_heapify(cp, idx);
 76	} else {
 77		cp->elements[idx].dl = new_dl;
 78		while (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
 79					cp->elements[idx].dl)) {
 80			cpudl_exchange(cp, idx, parent(idx));
 81			idx = parent(idx);
 82		}
 83	}
 84}
 85
 86static inline int cpudl_maximum(struct cpudl *cp)
 87{
 88	return cp->elements[0].cpu;
 89}
 90
 91/*
 92 * cpudl_find - find the best (later-dl) CPU in the system
 93 * @cp: the cpudl max-heap context
 94 * @p: the task
 95 * @later_mask: a mask to fill in with the selected CPUs (or NULL)
 96 *
 97 * Returns: int - best CPU (heap maximum if suitable)
 98 */
 99int cpudl_find(struct cpudl *cp, struct task_struct *p,
100	       struct cpumask *later_mask)
101{
102	int best_cpu = -1;
103	const struct sched_dl_entity *dl_se = &p->dl;
104
105	if (later_mask &&
106	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
107		best_cpu = cpumask_any(later_mask);
108		goto out;
109	} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
110			dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
111		best_cpu = cpudl_maximum(cp);
112		if (later_mask)
113			cpumask_set_cpu(best_cpu, later_mask);
114	}
115
116out:
117	WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
118
119	return best_cpu;
120}
121
122/*
123 * cpudl_set - update the cpudl max-heap
124 * @cp: the cpudl max-heap context
125 * @cpu: the target cpu
126 * @dl: the new earliest deadline for this cpu
127 *
128 * Notes: assumes cpu_rq(cpu)->lock is locked
129 *
130 * Returns: (void)
131 */
132void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
133{
134	int old_idx, new_cpu;
135	unsigned long flags;
136
137	WARN_ON(!cpu_present(cpu));
138
139	raw_spin_lock_irqsave(&cp->lock, flags);
140	old_idx = cp->elements[cpu].idx;
141	if (!is_valid) {
142		/* remove item */
143		if (old_idx == IDX_INVALID) {
144			/*
145			 * Nothing to remove if old_idx was invalid.
146			 * This could happen if a rq_offline_dl is
147			 * called for a CPU without -dl tasks running.
148			 */
149			goto out;
150		}
151		new_cpu = cp->elements[cp->size - 1].cpu;
152		cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
153		cp->elements[old_idx].cpu = new_cpu;
154		cp->size--;
155		cp->elements[new_cpu].idx = old_idx;
156		cp->elements[cpu].idx = IDX_INVALID;
157		while (old_idx > 0 && dl_time_before(
158				cp->elements[parent(old_idx)].dl,
159				cp->elements[old_idx].dl)) {
160			cpudl_exchange(cp, old_idx, parent(old_idx));
161			old_idx = parent(old_idx);
162		}
163		cpumask_set_cpu(cpu, cp->free_cpus);
164                cpudl_heapify(cp, old_idx);
165
166		goto out;
167	}
168
169	if (old_idx == IDX_INVALID) {
170		cp->size++;
171		cp->elements[cp->size - 1].dl = 0;
172		cp->elements[cp->size - 1].cpu = cpu;
173		cp->elements[cpu].idx = cp->size - 1;
174		cpudl_change_key(cp, cp->size - 1, dl);
175		cpumask_clear_cpu(cpu, cp->free_cpus);
176	} else {
177		cpudl_change_key(cp, old_idx, dl);
178	}
179
180out:
181	raw_spin_unlock_irqrestore(&cp->lock, flags);
182}
183
184/*
185 * cpudl_set_freecpu - Set the cpudl.free_cpus
186 * @cp: the cpudl max-heap context
187 * @cpu: rd attached cpu
188 */
189void cpudl_set_freecpu(struct cpudl *cp, int cpu)
190{
191	cpumask_set_cpu(cpu, cp->free_cpus);
192}
193
194/*
195 * cpudl_clear_freecpu - Clear the cpudl.free_cpus
196 * @cp: the cpudl max-heap context
197 * @cpu: rd attached cpu
198 */
199void cpudl_clear_freecpu(struct cpudl *cp, int cpu)
200{
201	cpumask_clear_cpu(cpu, cp->free_cpus);
202}
203
204/*
205 * cpudl_init - initialize the cpudl structure
206 * @cp: the cpudl max-heap context
207 */
208int cpudl_init(struct cpudl *cp)
209{
210	int i;
211
212	memset(cp, 0, sizeof(*cp));
213	raw_spin_lock_init(&cp->lock);
214	cp->size = 0;
215
216	cp->elements = kcalloc(nr_cpu_ids,
217			       sizeof(struct cpudl_item),
218			       GFP_KERNEL);
219	if (!cp->elements)
220		return -ENOMEM;
221
222	if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
223		kfree(cp->elements);
224		return -ENOMEM;
225	}
226
227	for_each_possible_cpu(i)
228		cp->elements[i].idx = IDX_INVALID;
229
230	return 0;
231}
232
233/*
234 * cpudl_cleanup - clean up the cpudl structure
235 * @cp: the cpudl max-heap context
236 */
237void cpudl_cleanup(struct cpudl *cp)
238{
239	free_cpumask_var(cp->free_cpus);
240	kfree(cp->elements);
241}