kernel/sched/cpudeadline.c

   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
  10 static inline int parent(int i)
  11 {
  12         return (i - 1) >> 1;
  13 }
  14
  15 static inline int left_child(int i)
  16 {
  17         return (i << 1) + 1;
  18 }
  19
  20 static inline int right_child(int i)
  21 {
  22         return (i << 1) + 2;
  23 }
  24
  25 static 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
  68 static 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
  94 static 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
 103 static 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  */
 116 int 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  */
 173 void 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  */
 213 void 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  */
 244 void 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  */
 254 void 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  */
 263 int 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  */
 291 void cpudl_cleanup(struct cpudl *cp)
 292 {
 293         free_cpumask_var(cp->free_cpus);
 294         kfree(cp->elements);
 295 }