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#include "sched.h"
14
15static inline int parent(int i)
16{
17 return (i - 1) >> 1;
18}
19
20static inline int left_child(int i)
21{
22 return (i << 1) + 1;
23}
24
25static inline int right_child(int i)
26{
27 return (i << 1) + 2;
28}
29
30static void cpudl_heapify_down(struct cpudl *cp, int idx)
31{
32 int l, r, largest;
33
34 int orig_cpu = cp->elements[idx].cpu;
35 u64 orig_dl = cp->elements[idx].dl;
36
37 if (left_child(idx) >= cp->size)
38 return;
39
40 /* adapted from lib/prio_heap.c */
41 while (1) {
42 u64 largest_dl;
43
44 l = left_child(idx);
45 r = right_child(idx);
46 largest = idx;
47 largest_dl = orig_dl;
48
49 if ((l < cp->size) && dl_time_before(orig_dl,
50 cp->elements[l].dl)) {
51 largest = l;
52 largest_dl = cp->elements[l].dl;
53 }
54 if ((r < cp->size) && dl_time_before(largest_dl,
55 cp->elements[r].dl))
56 largest = r;
57
58 if (largest == idx)
59 break;
60
61 /* pull largest child onto idx */
62 cp->elements[idx].cpu = cp->elements[largest].cpu;
63 cp->elements[idx].dl = cp->elements[largest].dl;
64 cp->elements[cp->elements[idx].cpu].idx = idx;
65 idx = largest;
66 }
67 /* actual push down of saved original values orig_* */
68 cp->elements[idx].cpu = orig_cpu;
69 cp->elements[idx].dl = orig_dl;
70 cp->elements[cp->elements[idx].cpu].idx = idx;
71}
72
73static void cpudl_heapify_up(struct cpudl *cp, int idx)
74{
75 int p;
76
77 int orig_cpu = cp->elements[idx].cpu;
78 u64 orig_dl = cp->elements[idx].dl;
79
80 if (idx == 0)
81 return;
82
83 do {
84 p = parent(idx);
85 if (dl_time_before(orig_dl, cp->elements[p].dl))
86 break;
87 /* pull parent onto idx */
88 cp->elements[idx].cpu = cp->elements[p].cpu;
89 cp->elements[idx].dl = cp->elements[p].dl;
90 cp->elements[cp->elements[idx].cpu].idx = idx;
91 idx = p;
92 } while (idx != 0);
93 /* actual push up of saved original values orig_* */
94 cp->elements[idx].cpu = orig_cpu;
95 cp->elements[idx].dl = orig_dl;
96 cp->elements[cp->elements[idx].cpu].idx = idx;
97}
98
99static void cpudl_heapify(struct cpudl *cp, int idx)
100{
101 if (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
102 cp->elements[idx].dl))
103 cpudl_heapify_up(cp, idx);
104 else
105 cpudl_heapify_down(cp, idx);
106}
107
108static inline int cpudl_maximum(struct cpudl *cp)
109{
110 return cp->elements[0].cpu;
111}
112
113/*
114 * cpudl_find - find the best (later-dl) CPU in the system
115 * @cp: the cpudl max-heap context
116 * @p: the task
117 * @later_mask: a mask to fill in with the selected CPUs (or NULL)
118 *
119 * Returns: int - CPUs were found
120 */
121int cpudl_find(struct cpudl *cp, struct task_struct *p,
122 struct cpumask *later_mask)
123{
124 const struct sched_dl_entity *dl_se = &p->dl;
125
126 if (later_mask &&
127 cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
128 return 1;
129 } else {
130 int best_cpu = cpudl_maximum(cp);
131
132 WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
133
134 if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
135 dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
136 if (later_mask)
137 cpumask_set_cpu(best_cpu, later_mask);
138
139 return 1;
140 }
141 }
142 return 0;
143}
144
145/*
146 * cpudl_clear - remove a CPU from the cpudl max-heap
147 * @cp: the cpudl max-heap context
148 * @cpu: the target CPU
149 *
150 * Notes: assumes cpu_rq(cpu)->lock is locked
151 *
152 * Returns: (void)
153 */
154void cpudl_clear(struct cpudl *cp, int cpu)
155{
156 int old_idx, new_cpu;
157 unsigned long flags;
158
159 WARN_ON(!cpu_present(cpu));
160
161 raw_spin_lock_irqsave(&cp->lock, flags);
162
163 old_idx = cp->elements[cpu].idx;
164 if (old_idx == IDX_INVALID) {
165 /*
166 * Nothing to remove if old_idx was invalid.
167 * This could happen if a rq_offline_dl is
168 * called for a CPU without -dl tasks running.
169 */
170 } else {
171 new_cpu = cp->elements[cp->size - 1].cpu;
172 cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
173 cp->elements[old_idx].cpu = new_cpu;
174 cp->size--;
175 cp->elements[new_cpu].idx = old_idx;
176 cp->elements[cpu].idx = IDX_INVALID;
177 cpudl_heapify(cp, old_idx);
178
179 cpumask_set_cpu(cpu, cp->free_cpus);
180 }
181 raw_spin_unlock_irqrestore(&cp->lock, flags);
182}
183
184/*
185 * cpudl_set - update the cpudl max-heap
186 * @cp: the cpudl max-heap context
187 * @cpu: the target CPU
188 * @dl: the new earliest deadline for this CPU
189 *
190 * Notes: assumes cpu_rq(cpu)->lock is locked
191 *
192 * Returns: (void)
193 */
194void cpudl_set(struct cpudl *cp, int cpu, u64 dl)
195{
196 int old_idx;
197 unsigned long flags;
198
199 WARN_ON(!cpu_present(cpu));
200
201 raw_spin_lock_irqsave(&cp->lock, flags);
202
203 old_idx = cp->elements[cpu].idx;
204 if (old_idx == IDX_INVALID) {
205 int new_idx = cp->size++;
206
207 cp->elements[new_idx].dl = dl;
208 cp->elements[new_idx].cpu = cpu;
209 cp->elements[cpu].idx = new_idx;
210 cpudl_heapify_up(cp, new_idx);
211 cpumask_clear_cpu(cpu, cp->free_cpus);
212 } else {
213 cp->elements[old_idx].dl = dl;
214 cpudl_heapify(cp, old_idx);
215 }
216
217 raw_spin_unlock_irqrestore(&cp->lock, flags);
218}
219
220/*
221 * cpudl_set_freecpu - Set the cpudl.free_cpus
222 * @cp: the cpudl max-heap context
223 * @cpu: rd attached CPU
224 */
225void cpudl_set_freecpu(struct cpudl *cp, int cpu)
226{
227 cpumask_set_cpu(cpu, cp->free_cpus);
228}
229
230/*
231 * cpudl_clear_freecpu - Clear the cpudl.free_cpus
232 * @cp: the cpudl max-heap context
233 * @cpu: rd attached CPU
234 */
235void cpudl_clear_freecpu(struct cpudl *cp, int cpu)
236{
237 cpumask_clear_cpu(cpu, cp->free_cpus);
238}
239
240/*
241 * cpudl_init - initialize the cpudl structure
242 * @cp: the cpudl max-heap context
243 */
244int cpudl_init(struct cpudl *cp)
245{
246 int i;
247
248 raw_spin_lock_init(&cp->lock);
249 cp->size = 0;
250
251 cp->elements = kcalloc(nr_cpu_ids,
252 sizeof(struct cpudl_item),
253 GFP_KERNEL);
254 if (!cp->elements)
255 return -ENOMEM;
256
257 if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
258 kfree(cp->elements);
259 return -ENOMEM;
260 }
261
262 for_each_possible_cpu(i)
263 cp->elements[i].idx = IDX_INVALID;
264
265 return 0;
266}
267
268/*
269 * cpudl_cleanup - clean up the cpudl structure
270 * @cp: the cpudl max-heap context
271 */
272void cpudl_cleanup(struct cpudl *cp)
273{
274 free_cpumask_var(cp->free_cpus);
275 kfree(cp->elements);
276}
277