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 void cpudl_exchange(struct cpudl *cp, int a, int b) 35 { 36 int cpu_a = cp->elements[a].cpu, cpu_b = cp->elements[b].cpu; 37 38 swap(cp->elements[a].cpu, cp->elements[b].cpu); 39 swap(cp->elements[a].dl , cp->elements[b].dl ); 40 41 swap(cp->elements[cpu_a].idx, cp->elements[cpu_b].idx); 42 } 43 44 static void cpudl_heapify(struct cpudl *cp, int idx) 45 { 46 int l, r, largest; 47 48 /* adapted from lib/prio_heap.c */ 49 while(1) { 50 l = left_child(idx); 51 r = right_child(idx); 52 largest = idx; 53 54 if ((l < cp->size) && dl_time_before(cp->elements[idx].dl, 55 cp->elements[l].dl)) 56 largest = l; 57 if ((r < cp->size) && dl_time_before(cp->elements[largest].dl, 58 cp->elements[r].dl)) 59 largest = r; 60 if (largest == idx) 61 break; 62 63 /* Push idx down the heap one level and bump one up */ 64 cpudl_exchange(cp, largest, idx); 65 idx = largest; 66 } 67 } 68 69 static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl) 70 { 71 WARN_ON(idx == IDX_INVALID || !cpu_present(idx)); 72 73 if (dl_time_before(new_dl, cp->elements[idx].dl)) { 74 cp->elements[idx].dl = new_dl; 75 cpudl_heapify(cp, idx); 76 } else { 77 cp->elements[idx].dl = new_dl; 78 while (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl, 79 cp->elements[idx].dl)) { 80 cpudl_exchange(cp, idx, parent(idx)); 81 idx = parent(idx); 82 } 83 } 84 } 85 86 static inline int cpudl_maximum(struct cpudl *cp) 87 { 88 return cp->elements[0].cpu; 89 } 90 91 /* 92 * cpudl_find - find the best (later-dl) CPU in the system 93 * @cp: the cpudl max-heap context 94 * @p: the task 95 * @later_mask: a mask to fill in with the selected CPUs (or NULL) 96 * 97 * Returns: int - best CPU (heap maximum if suitable) 98 */ 99 int cpudl_find(struct cpudl *cp, struct task_struct *p, 100 struct cpumask *later_mask) 101 { 102 int best_cpu = -1; 103 const struct sched_dl_entity *dl_se = &p->dl; 104 105 if (later_mask && 106 cpumask_and(later_mask, cp->free_cpus, tsk_cpus_allowed(p))) { 107 best_cpu = cpumask_any(later_mask); 108 goto out; 109 } else if (cpumask_test_cpu(cpudl_maximum(cp), tsk_cpus_allowed(p)) && 110 dl_time_before(dl_se->deadline, cp->elements[0].dl)) { 111 best_cpu = cpudl_maximum(cp); 112 if (later_mask) 113 cpumask_set_cpu(best_cpu, later_mask); 114 } 115 116 out: 117 WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); 118 119 return best_cpu; 120 } 121 122 /* 123 * cpudl_set - update the cpudl max-heap 124 * @cp: the cpudl max-heap context 125 * @cpu: the target cpu 126 * @dl: the new earliest deadline for this cpu 127 * 128 * Notes: assumes cpu_rq(cpu)->lock is locked 129 * 130 * Returns: (void) 131 */ 132 void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid) 133 { 134 int old_idx, new_cpu; 135 unsigned long flags; 136 137 WARN_ON(!cpu_present(cpu)); 138 139 raw_spin_lock_irqsave(&cp->lock, flags); 140 old_idx = cp->elements[cpu].idx; 141 if (!is_valid) { 142 /* remove item */ 143 if (old_idx == IDX_INVALID) { 144 /* 145 * Nothing to remove if old_idx was invalid. 146 * This could happen if a rq_offline_dl is 147 * called for a CPU without -dl tasks running. 148 */ 149 goto out; 150 } 151 new_cpu = cp->elements[cp->size - 1].cpu; 152 cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl; 153 cp->elements[old_idx].cpu = new_cpu; 154 cp->size--; 155 cp->elements[new_cpu].idx = old_idx; 156 cp->elements[cpu].idx = IDX_INVALID; 157 while (old_idx > 0 && dl_time_before( 158 cp->elements[parent(old_idx)].dl, 159 cp->elements[old_idx].dl)) { 160 cpudl_exchange(cp, old_idx, parent(old_idx)); 161 old_idx = parent(old_idx); 162 } 163 cpumask_set_cpu(cpu, cp->free_cpus); 164 cpudl_heapify(cp, old_idx); 165 166 goto out; 167 } 168 169 if (old_idx == IDX_INVALID) { 170 cp->size++; 171 cp->elements[cp->size - 1].dl = 0; 172 cp->elements[cp->size - 1].cpu = cpu; 173 cp->elements[cpu].idx = cp->size - 1; 174 cpudl_change_key(cp, cp->size - 1, dl); 175 cpumask_clear_cpu(cpu, cp->free_cpus); 176 } else { 177 cpudl_change_key(cp, old_idx, dl); 178 } 179 180 out: 181 raw_spin_unlock_irqrestore(&cp->lock, flags); 182 } 183 184 /* 185 * cpudl_set_freecpu - Set the cpudl.free_cpus 186 * @cp: the cpudl max-heap context 187 * @cpu: rd attached cpu 188 */ 189 void cpudl_set_freecpu(struct cpudl *cp, int cpu) 190 { 191 cpumask_set_cpu(cpu, cp->free_cpus); 192 } 193 194 /* 195 * cpudl_clear_freecpu - Clear the cpudl.free_cpus 196 * @cp: the cpudl max-heap context 197 * @cpu: rd attached cpu 198 */ 199 void cpudl_clear_freecpu(struct cpudl *cp, int cpu) 200 { 201 cpumask_clear_cpu(cpu, cp->free_cpus); 202 } 203 204 /* 205 * cpudl_init - initialize the cpudl structure 206 * @cp: the cpudl max-heap context 207 */ 208 int cpudl_init(struct cpudl *cp) 209 { 210 int i; 211 212 memset(cp, 0, sizeof(*cp)); 213 raw_spin_lock_init(&cp->lock); 214 cp->size = 0; 215 216 cp->elements = kcalloc(nr_cpu_ids, 217 sizeof(struct cpudl_item), 218 GFP_KERNEL); 219 if (!cp->elements) 220 return -ENOMEM; 221 222 if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) { 223 kfree(cp->elements); 224 return -ENOMEM; 225 } 226 227 for_each_possible_cpu(i) 228 cp->elements[i].idx = IDX_INVALID; 229 230 return 0; 231 } 232 233 /* 234 * cpudl_cleanup - clean up the cpudl structure 235 * @cp: the cpudl max-heap context 236 */ 237 void cpudl_cleanup(struct cpudl *cp) 238 { 239 free_cpumask_var(cp->free_cpus); 240 kfree(cp->elements); 241 } 242