1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *  kernel/sched/cpudeadline.c
4 *
5 *  Global CPU deadline management
6 *
7 *  Author: Juri Lelli <j.lelli@sssup.it>
8 */
9
10static inline int parent(int i)
11{
12	return (i - 1) >> 1;
13}
14
15static inline int left_child(int i)
16{
17	return (i << 1) + 1;
18}
19
20static inline int right_child(int i)
21{
22	return (i << 1) + 2;
23}
24
25static void cpudl_heapify_down(struct cpudl *cp, int idx)
26{
27	int l, r, largest;
28
29	int orig_cpu = cp->elements[idx].cpu;
30	u64 orig_dl = cp->elements[idx].dl;
31
32	if (left_child(idx) >= cp->size)
33		return;
34
35	/* adapted from lib/prio_heap.c */
36	while (1) {
37		u64 largest_dl;
38
39		l = left_child(idx);
40		r = right_child(idx);
41		largest = idx;
42		largest_dl = orig_dl;
43
44		if ((l < cp->size) && dl_time_before(orig_dl,
45						cp->elements[l].dl)) {
46			largest = l;
47			largest_dl = cp->elements[l].dl;
48		}
49		if ((r < cp->size) && dl_time_before(largest_dl,
50						cp->elements[r].dl))
51			largest = r;
52
53		if (largest == idx)
54			break;
55
56		/* pull largest child onto idx */
57		cp->elements[idx].cpu = cp->elements[largest].cpu;
58		cp->elements[idx].dl = cp->elements[largest].dl;
59		cp->elements[cp->elements[idx].cpu].idx = idx;
60		idx = largest;
61	}
62	/* actual push down of saved original values orig_* */
63	cp->elements[idx].cpu = orig_cpu;
64	cp->elements[idx].dl = orig_dl;
65	cp->elements[cp->elements[idx].cpu].idx = idx;
66}
67
68static void cpudl_heapify_up(struct cpudl *cp, int idx)
69{
70	int p;
71
72	int orig_cpu = cp->elements[idx].cpu;
73	u64 orig_dl = cp->elements[idx].dl;
74
75	if (idx == 0)
76		return;
77
78	do {
79		p = parent(idx);
80		if (dl_time_before(orig_dl, cp->elements[p].dl))
81			break;
82		/* pull parent onto idx */
83		cp->elements[idx].cpu = cp->elements[p].cpu;
84		cp->elements[idx].dl = cp->elements[p].dl;
85		cp->elements[cp->elements[idx].cpu].idx = idx;
86		idx = p;
87	} while (idx != 0);
88	/* actual push up of saved original values orig_* */
89	cp->elements[idx].cpu = orig_cpu;
90	cp->elements[idx].dl = orig_dl;
91	cp->elements[cp->elements[idx].cpu].idx = idx;
92}
93
94static void cpudl_heapify(struct cpudl *cp, int idx)
95{
96	if (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
97				cp->elements[idx].dl))
98		cpudl_heapify_up(cp, idx);
99	else
100		cpudl_heapify_down(cp, idx);
101}
102
103static inline int cpudl_maximum(struct cpudl *cp)
104{
105	return cp->elements[0].cpu;
106}
107
108/*
109 * cpudl_find - find the best (later-dl) CPU in the system
110 * @cp: the cpudl max-heap context
111 * @p: the task
112 * @later_mask: a mask to fill in with the selected CPUs (or NULL)
113 *
114 * Returns: int - CPUs were found
115 */
116int cpudl_find(struct cpudl *cp, struct task_struct *p,
117	       struct cpumask *later_mask)
118{
119	const struct sched_dl_entity *dl_se = &p->dl;
120
121	if (later_mask &&
122	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_mask)) {
123		unsigned long cap, max_cap = 0;
124		int cpu, max_cpu = -1;
125
126		if (!sched_asym_cpucap_active())
127			return 1;
128
129		/* Ensure the capacity of the CPUs fits the task. */
130		for_each_cpu(cpu, later_mask) {
131			if (!dl_task_fits_capacity(p, cpu)) {
132				cpumask_clear_cpu(cpu, later_mask);
133
134				cap = arch_scale_cpu_capacity(cpu);
135
136				if (cap > max_cap ||
137				    (cpu == task_cpu(p) && cap == max_cap)) {
138					max_cap = cap;
139					max_cpu = cpu;
140				}
141			}
142		}
143
144		if (cpumask_empty(later_mask))
145			cpumask_set_cpu(max_cpu, later_mask);
146
147		return 1;
148	} else {
149		int best_cpu = cpudl_maximum(cp);
150
151		WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
152
153		if (cpumask_test_cpu(best_cpu, &p->cpus_mask) &&
154		    dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
155			if (later_mask)
156				cpumask_set_cpu(best_cpu, later_mask);
157
158			return 1;
159		}
160	}
161	return 0;
162}
163
164/*
165 * cpudl_clear - remove a CPU from the cpudl max-heap
166 * @cp: the cpudl max-heap context
167 * @cpu: the target CPU
168 *
169 * Notes: assumes cpu_rq(cpu)->lock is locked
170 *
171 * Returns: (void)
172 */
173void cpudl_clear(struct cpudl *cp, int cpu)
174{
175	int old_idx, new_cpu;
176	unsigned long flags;
177
178	WARN_ON(!cpu_present(cpu));
179
180	raw_spin_lock_irqsave(&cp->lock, flags);
181
182	old_idx = cp->elements[cpu].idx;
183	if (old_idx == IDX_INVALID) {
184		/*
185		 * Nothing to remove if old_idx was invalid.
186		 * This could happen if a rq_offline_dl is
187		 * called for a CPU without -dl tasks running.
188		 */
189	} else {
190		new_cpu = cp->elements[cp->size - 1].cpu;
191		cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
192		cp->elements[old_idx].cpu = new_cpu;
193		cp->size--;
194		cp->elements[new_cpu].idx = old_idx;
195		cp->elements[cpu].idx = IDX_INVALID;
196		cpudl_heapify(cp, old_idx);
197
198		cpumask_set_cpu(cpu, cp->free_cpus);
199	}
200	raw_spin_unlock_irqrestore(&cp->lock, flags);
201}
202
203/*
204 * cpudl_set - update the cpudl max-heap
205 * @cp: the cpudl max-heap context
206 * @cpu: the target CPU
207 * @dl: the new earliest deadline for this CPU
208 *
209 * Notes: assumes cpu_rq(cpu)->lock is locked
210 *
211 * Returns: (void)
212 */
213void cpudl_set(struct cpudl *cp, int cpu, u64 dl)
214{
215	int old_idx;
216	unsigned long flags;
217
218	WARN_ON(!cpu_present(cpu));
219
220	raw_spin_lock_irqsave(&cp->lock, flags);
221
222	old_idx = cp->elements[cpu].idx;
223	if (old_idx == IDX_INVALID) {
224		int new_idx = cp->size++;
225
226		cp->elements[new_idx].dl = dl;
227		cp->elements[new_idx].cpu = cpu;
228		cp->elements[cpu].idx = new_idx;
229		cpudl_heapify_up(cp, new_idx);
230		cpumask_clear_cpu(cpu, cp->free_cpus);
231	} else {
232		cp->elements[old_idx].dl = dl;
233		cpudl_heapify(cp, old_idx);
234	}
235
236	raw_spin_unlock_irqrestore(&cp->lock, flags);
237}
238
239/*
240 * cpudl_set_freecpu - Set the cpudl.free_cpus
241 * @cp: the cpudl max-heap context
242 * @cpu: rd attached CPU
243 */
244void cpudl_set_freecpu(struct cpudl *cp, int cpu)
245{
246	cpumask_set_cpu(cpu, cp->free_cpus);
247}
248
249/*
250 * cpudl_clear_freecpu - Clear the cpudl.free_cpus
251 * @cp: the cpudl max-heap context
252 * @cpu: rd attached CPU
253 */
254void cpudl_clear_freecpu(struct cpudl *cp, int cpu)
255{
256	cpumask_clear_cpu(cpu, cp->free_cpus);
257}
258
259/*
260 * cpudl_init - initialize the cpudl structure
261 * @cp: the cpudl max-heap context
262 */
263int cpudl_init(struct cpudl *cp)
264{
265	int i;
266
267	raw_spin_lock_init(&cp->lock);
268	cp->size = 0;
269
270	cp->elements = kcalloc(nr_cpu_ids,
271			       sizeof(struct cpudl_item),
272			       GFP_KERNEL);
273	if (!cp->elements)
274		return -ENOMEM;
275
276	if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
277		kfree(cp->elements);
278		return -ENOMEM;
279	}
280
281	for_each_possible_cpu(i)
282		cp->elements[i].idx = IDX_INVALID;
283
284	return 0;
285}
286
287/*
288 * cpudl_cleanup - clean up the cpudl structure
289 * @cp: the cpudl max-heap context
290 */
291void cpudl_cleanup(struct cpudl *cp)
292{
293	free_cpumask_var(cp->free_cpus);
294	kfree(cp->elements);
295}
296