1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * kernel/sched/cpudl.c
4 *
5 * Global CPU deadline management
6 *
7 * Author: Juri Lelli <j.lelli@sssup.it>
8 */
9 #include "sched.h"
10
parent(int i)11 static inline int parent(int i)
12 {
13 return (i - 1) >> 1;
14 }
15
left_child(int i)16 static inline int left_child(int i)
17 {
18 return (i << 1) + 1;
19 }
20
right_child(int i)21 static inline int right_child(int i)
22 {
23 return (i << 1) + 2;
24 }
25
cpudl_heapify_down(struct cpudl * cp,int idx)26 static void cpudl_heapify_down(struct cpudl *cp, int idx)
27 {
28 int l, r, largest;
29
30 int orig_cpu = cp->elements[idx].cpu;
31 u64 orig_dl = cp->elements[idx].dl;
32
33 if (left_child(idx) >= cp->size)
34 return;
35
36 /* adapted from lib/prio_heap.c */
37 while (1) {
38 u64 largest_dl;
39
40 l = left_child(idx);
41 r = right_child(idx);
42 largest = idx;
43 largest_dl = orig_dl;
44
45 if ((l < cp->size) && dl_time_before(orig_dl,
46 cp->elements[l].dl)) {
47 largest = l;
48 largest_dl = cp->elements[l].dl;
49 }
50 if ((r < cp->size) && dl_time_before(largest_dl,
51 cp->elements[r].dl))
52 largest = r;
53
54 if (largest == idx)
55 break;
56
57 /* pull largest child onto idx */
58 cp->elements[idx].cpu = cp->elements[largest].cpu;
59 cp->elements[idx].dl = cp->elements[largest].dl;
60 cp->elements[cp->elements[idx].cpu].idx = idx;
61 idx = largest;
62 }
63 /* actual push down of saved original values orig_* */
64 cp->elements[idx].cpu = orig_cpu;
65 cp->elements[idx].dl = orig_dl;
66 cp->elements[cp->elements[idx].cpu].idx = idx;
67 }
68
cpudl_heapify_up(struct cpudl * cp,int idx)69 static void cpudl_heapify_up(struct cpudl *cp, int idx)
70 {
71 int p;
72
73 int orig_cpu = cp->elements[idx].cpu;
74 u64 orig_dl = cp->elements[idx].dl;
75
76 if (idx == 0)
77 return;
78
79 do {
80 p = parent(idx);
81 if (dl_time_before(orig_dl, cp->elements[p].dl))
82 break;
83 /* pull parent onto idx */
84 cp->elements[idx].cpu = cp->elements[p].cpu;
85 cp->elements[idx].dl = cp->elements[p].dl;
86 cp->elements[cp->elements[idx].cpu].idx = idx;
87 idx = p;
88 } while (idx != 0);
89 /* actual push up of saved original values orig_* */
90 cp->elements[idx].cpu = orig_cpu;
91 cp->elements[idx].dl = orig_dl;
92 cp->elements[cp->elements[idx].cpu].idx = idx;
93 }
94
cpudl_heapify(struct cpudl * cp,int idx)95 static void cpudl_heapify(struct cpudl *cp, int idx)
96 {
97 if (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
98 cp->elements[idx].dl))
99 cpudl_heapify_up(cp, idx);
100 else
101 cpudl_heapify_down(cp, idx);
102 }
103
cpudl_maximum(struct cpudl * cp)104 static inline int cpudl_maximum(struct cpudl *cp)
105 {
106 return cp->elements[0].cpu;
107 }
108
109 /*
110 * cpudl_find - find the best (later-dl) CPU in the system
111 * @cp: the cpudl max-heap context
112 * @p: the task
113 * @later_mask: a mask to fill in with the selected CPUs (or NULL)
114 *
115 * Returns: int - CPUs were found
116 */
cpudl_find(struct cpudl * cp,struct task_struct * p,struct cpumask * later_mask)117 int cpudl_find(struct cpudl *cp, struct task_struct *p,
118 struct cpumask *later_mask)
119 {
120 const struct sched_dl_entity *dl_se = &p->dl;
121
122 if (later_mask &&
123 cpumask_and(later_mask, cp->free_cpus, p->cpus_ptr)) {
124 return 1;
125 } else {
126 int best_cpu = cpudl_maximum(cp);
127
128 WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
129
130 if (cpumask_test_cpu(best_cpu, p->cpus_ptr) &&
131 dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
132 if (later_mask)
133 cpumask_set_cpu(best_cpu, later_mask);
134
135 return 1;
136 }
137 }
138 return 0;
139 }
140
141 /*
142 * cpudl_clear - remove a CPU from the cpudl max-heap
143 * @cp: the cpudl max-heap context
144 * @cpu: the target CPU
145 *
146 * Notes: assumes cpu_rq(cpu)->lock is locked
147 *
148 * Returns: (void)
149 */
cpudl_clear(struct cpudl * cp,int cpu)150 void cpudl_clear(struct cpudl *cp, int cpu)
151 {
152 int old_idx, new_cpu;
153 unsigned long flags;
154
155 WARN_ON(!cpu_present(cpu));
156
157 raw_spin_lock_irqsave(&cp->lock, flags);
158
159 old_idx = cp->elements[cpu].idx;
160 if (old_idx == IDX_INVALID) {
161 /*
162 * Nothing to remove if old_idx was invalid.
163 * This could happen if a rq_offline_dl is
164 * called for a CPU without -dl tasks running.
165 */
166 } else {
167 new_cpu = cp->elements[cp->size - 1].cpu;
168 cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
169 cp->elements[old_idx].cpu = new_cpu;
170 cp->size--;
171 cp->elements[new_cpu].idx = old_idx;
172 cp->elements[cpu].idx = IDX_INVALID;
173 cpudl_heapify(cp, old_idx);
174
175 cpumask_set_cpu(cpu, cp->free_cpus);
176 }
177 raw_spin_unlock_irqrestore(&cp->lock, flags);
178 }
179
180 /*
181 * cpudl_set - update the cpudl max-heap
182 * @cp: the cpudl max-heap context
183 * @cpu: the target CPU
184 * @dl: the new earliest deadline for this CPU
185 *
186 * Notes: assumes cpu_rq(cpu)->lock is locked
187 *
188 * Returns: (void)
189 */
cpudl_set(struct cpudl * cp,int cpu,u64 dl)190 void cpudl_set(struct cpudl *cp, int cpu, u64 dl)
191 {
192 int old_idx;
193 unsigned long flags;
194
195 WARN_ON(!cpu_present(cpu));
196
197 raw_spin_lock_irqsave(&cp->lock, flags);
198
199 old_idx = cp->elements[cpu].idx;
200 if (old_idx == IDX_INVALID) {
201 int new_idx = cp->size++;
202
203 cp->elements[new_idx].dl = dl;
204 cp->elements[new_idx].cpu = cpu;
205 cp->elements[cpu].idx = new_idx;
206 cpudl_heapify_up(cp, new_idx);
207 cpumask_clear_cpu(cpu, cp->free_cpus);
208 } else {
209 cp->elements[old_idx].dl = dl;
210 cpudl_heapify(cp, old_idx);
211 }
212
213 raw_spin_unlock_irqrestore(&cp->lock, flags);
214 }
215
216 /*
217 * cpudl_set_freecpu - Set the cpudl.free_cpus
218 * @cp: the cpudl max-heap context
219 * @cpu: rd attached CPU
220 */
cpudl_set_freecpu(struct cpudl * cp,int cpu)221 void cpudl_set_freecpu(struct cpudl *cp, int cpu)
222 {
223 cpumask_set_cpu(cpu, cp->free_cpus);
224 }
225
226 /*
227 * cpudl_clear_freecpu - Clear the cpudl.free_cpus
228 * @cp: the cpudl max-heap context
229 * @cpu: rd attached CPU
230 */
cpudl_clear_freecpu(struct cpudl * cp,int cpu)231 void cpudl_clear_freecpu(struct cpudl *cp, int cpu)
232 {
233 cpumask_clear_cpu(cpu, cp->free_cpus);
234 }
235
236 /*
237 * cpudl_init - initialize the cpudl structure
238 * @cp: the cpudl max-heap context
239 */
cpudl_init(struct cpudl * cp)240 int cpudl_init(struct cpudl *cp)
241 {
242 int i;
243
244 raw_spin_lock_init(&cp->lock);
245 cp->size = 0;
246
247 cp->elements = kcalloc(nr_cpu_ids,
248 sizeof(struct cpudl_item),
249 GFP_KERNEL);
250 if (!cp->elements)
251 return -ENOMEM;
252
253 if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
254 kfree(cp->elements);
255 return -ENOMEM;
256 }
257
258 for_each_possible_cpu(i)
259 cp->elements[i].idx = IDX_INVALID;
260
261 return 0;
262 }
263
264 /*
265 * cpudl_cleanup - clean up the cpudl structure
266 * @cp: the cpudl max-heap context
267 */
cpudl_cleanup(struct cpudl * cp)268 void cpudl_cleanup(struct cpudl *cp)
269 {
270 free_cpumask_var(cp->free_cpus);
271 kfree(cp->elements);
272 }
273
