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 19 static inline int parent(int i) 20 { 21 return (i - 1) >> 1; 22 } 23 24 static inline int left_child(int i) 25 { 26 return (i << 1) + 1; 27 } 28 29 static inline int right_child(int i) 30 { 31 return (i << 1) + 2; 32 } 33 34 static inline int dl_time_before(u64 a, u64 b) 35 { 36 return (s64)(a - b) < 0; 37 } 38 39 static void cpudl_exchange(struct cpudl *cp, int a, int b) 40 { 41 int cpu_a = cp->elements[a].cpu, cpu_b = cp->elements[b].cpu; 42 43 swap(cp->elements[a].cpu, cp->elements[b].cpu); 44 swap(cp->elements[a].dl , cp->elements[b].dl ); 45 46 swap(cp->elements[cpu_a].idx, cp->elements[cpu_b].idx); 47 } 48 49 static void cpudl_heapify(struct cpudl *cp, int idx) 50 { 51 int l, r, largest; 52 53 /* adapted from lib/prio_heap.c */ 54 while(1) { 55 l = left_child(idx); 56 r = right_child(idx); 57 largest = idx; 58 59 if ((l < cp->size) && dl_time_before(cp->elements[idx].dl, 60 cp->elements[l].dl)) 61 largest = l; 62 if ((r < cp->size) && dl_time_before(cp->elements[largest].dl, 63 cp->elements[r].dl)) 64 largest = r; 65 if (largest == idx) 66 break; 67 68 /* Push idx down the heap one level and bump one up */ 69 cpudl_exchange(cp, largest, idx); 70 idx = largest; 71 } 72 } 73 74 static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl) 75 { 76 WARN_ON(idx == IDX_INVALID || !cpu_present(idx)); 77 78 if (dl_time_before(new_dl, cp->elements[idx].dl)) { 79 cp->elements[idx].dl = new_dl; 80 cpudl_heapify(cp, idx); 81 } else { 82 cp->elements[idx].dl = new_dl; 83 while (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl, 84 cp->elements[idx].dl)) { 85 cpudl_exchange(cp, idx, parent(idx)); 86 idx = parent(idx); 87 } 88 } 89 } 90 91 static inline int cpudl_maximum(struct cpudl *cp) 92 { 93 return cp->elements[0].cpu; 94 } 95 96 /* 97 * cpudl_find - find the best (later-dl) CPU in the system 98 * @cp: the cpudl max-heap context 99 * @p: the task 100 * @later_mask: a mask to fill in with the selected CPUs (or NULL) 101 * 102 * Returns: int - best CPU (heap maximum if suitable) 103 */ 104 int cpudl_find(struct cpudl *cp, struct task_struct *p, 105 struct cpumask *later_mask) 106 { 107 int best_cpu = -1; 108 const struct sched_dl_entity *dl_se = &p->dl; 109 110 if (later_mask && cpumask_and(later_mask, later_mask, cp->free_cpus)) { 111 best_cpu = cpumask_any(later_mask); 112 goto out; 113 } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) && 114 dl_time_before(dl_se->deadline, cp->elements[0].dl)) { 115 best_cpu = cpudl_maximum(cp); 116 if (later_mask) 117 cpumask_set_cpu(best_cpu, later_mask); 118 } 119 120 out: 121 WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); 122 123 return best_cpu; 124 } 125 126 /* 127 * cpudl_set - update the cpudl max-heap 128 * @cp: the cpudl max-heap context 129 * @cpu: the target cpu 130 * @dl: the new earliest deadline for this cpu 131 * 132 * Notes: assumes cpu_rq(cpu)->lock is locked 133 * 134 * Returns: (void) 135 */ 136 void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid) 137 { 138 int old_idx, new_cpu; 139 unsigned long flags; 140 141 WARN_ON(!cpu_present(cpu)); 142 143 raw_spin_lock_irqsave(&cp->lock, flags); 144 old_idx = cp->elements[cpu].idx; 145 if (!is_valid) { 146 /* remove item */ 147 if (old_idx == IDX_INVALID) { 148 /* 149 * Nothing to remove if old_idx was invalid. 150 * This could happen if a rq_offline_dl is 151 * called for a CPU without -dl tasks running. 152 */ 153 goto out; 154 } 155 new_cpu = cp->elements[cp->size - 1].cpu; 156 cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl; 157 cp->elements[old_idx].cpu = new_cpu; 158 cp->size--; 159 cp->elements[new_cpu].idx = old_idx; 160 cp->elements[cpu].idx = IDX_INVALID; 161 while (old_idx > 0 && dl_time_before( 162 cp->elements[parent(old_idx)].dl, 163 cp->elements[old_idx].dl)) { 164 cpudl_exchange(cp, old_idx, parent(old_idx)); 165 old_idx = parent(old_idx); 166 } 167 cpumask_set_cpu(cpu, cp->free_cpus); 168 cpudl_heapify(cp, old_idx); 169 170 goto out; 171 } 172 173 if (old_idx == IDX_INVALID) { 174 cp->size++; 175 cp->elements[cp->size - 1].dl = 0; 176 cp->elements[cp->size - 1].cpu = cpu; 177 cp->elements[cpu].idx = cp->size - 1; 178 cpudl_change_key(cp, cp->size - 1, dl); 179 cpumask_clear_cpu(cpu, cp->free_cpus); 180 } else { 181 cpudl_change_key(cp, old_idx, dl); 182 } 183 184 out: 185 raw_spin_unlock_irqrestore(&cp->lock, flags); 186 } 187 188 /* 189 * cpudl_init - initialize the cpudl structure 190 * @cp: the cpudl max-heap context 191 */ 192 int cpudl_init(struct cpudl *cp) 193 { 194 int i; 195 196 memset(cp, 0, sizeof(*cp)); 197 raw_spin_lock_init(&cp->lock); 198 cp->size = 0; 199 200 cp->elements = kcalloc(nr_cpu_ids, 201 sizeof(struct cpudl_item), 202 GFP_KERNEL); 203 if (!cp->elements) 204 return -ENOMEM; 205 206 if (!alloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) { 207 kfree(cp->elements); 208 return -ENOMEM; 209 } 210 211 for_each_possible_cpu(i) 212 cp->elements[i].idx = IDX_INVALID; 213 214 cpumask_setall(cp->free_cpus); 215 216 return 0; 217 } 218 219 /* 220 * cpudl_cleanup - clean up the cpudl structure 221 * @cp: the cpudl max-heap context 222 */ 223 void cpudl_cleanup(struct cpudl *cp) 224 { 225 free_cpumask_var(cp->free_cpus); 226 kfree(cp->elements); 227 } 228