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 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 }