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
 11static inline int parent(int i)
 12{
 13	return (i - 1) >> 1;
 14}
 15
 16static inline int left_child(int i)
 17{
 18	return (i << 1) + 1;
 19}
 20
 21static inline int right_child(int i)
 22{
 23	return (i << 1) + 2;
 24}
 25
 26static 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
 69static 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
 95static 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
104static 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 */
117int 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 */
150void 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 */
190void 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 */
221void 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 */
231void 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 */
240int 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 */
268void cpudl_cleanup(struct cpudl *cp)
269{
270	free_cpumask_var(cp->free_cpus);
271	kfree(cp->elements);
272}