kernel/sched/cpudeadline.c

   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, &p->cpus_allowed)) {
 107                 best_cpu = cpumask_any(later_mask);
 108                 goto out;
 109         } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
 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 }