lib/cpumask.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/slab.h>
   3 #include <linux/kernel.h>
   4 #include <linux/bitops.h>
   5 #include <linux/cpumask.h>
   6 #include <linux/export.h>
   7 #include <linux/memblock.h>
   8 #include <linux/numa.h>
   9 #include <linux/sched/isolation.h>
  10
  11 /**
  12  * cpumask_next - get the next cpu in a cpumask
  13  * @n: the cpu prior to the place to search (ie. return will be > @n)
  14  * @srcp: the cpumask pointer
  15  *
  16  * Returns >= nr_cpu_ids if no further cpus set.
  17  */
  18 unsigned int cpumask_next(int n, const struct cpumask *srcp)
  19 {
  20         /* -1 is a legal arg here. */
  21         if (n != -1)
  22                 cpumask_check(n);
  23         return find_next_bit(cpumask_bits(srcp), nr_cpumask_bits, n + 1);
  24 }
  25 EXPORT_SYMBOL(cpumask_next);
  26
  27 /**
  28  * cpumask_next_and - get the next cpu in *src1p & *src2p
  29  * @n: the cpu prior to the place to search (ie. return will be > @n)
  30  * @src1p: the first cpumask pointer
  31  * @src2p: the second cpumask pointer
  32  *
  33  * Returns >= nr_cpu_ids if no further cpus set in both.
  34  */
  35 int cpumask_next_and(int n, const struct cpumask *src1p,
  36                      const struct cpumask *src2p)
  37 {
  38         /* -1 is a legal arg here. */
  39         if (n != -1)
  40                 cpumask_check(n);
  41         return find_next_and_bit(cpumask_bits(src1p), cpumask_bits(src2p),
  42                 nr_cpumask_bits, n + 1);
  43 }
  44 EXPORT_SYMBOL(cpumask_next_and);
  45
  46 /**
  47  * cpumask_any_but - return a "random" in a cpumask, but not this one.
  48  * @mask: the cpumask to search
  49  * @cpu: the cpu to ignore.
  50  *
  51  * Often used to find any cpu but smp_processor_id() in a mask.
  52  * Returns >= nr_cpu_ids if no cpus set.
  53  */
  54 int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
  55 {
  56         unsigned int i;
  57
  58         cpumask_check(cpu);
  59         for_each_cpu(i, mask)
  60                 if (i != cpu)
  61                         break;
  62         return i;
  63 }
  64 EXPORT_SYMBOL(cpumask_any_but);
  65
  66 /**
  67  * cpumask_next_wrap - helper to implement for_each_cpu_wrap
  68  * @n: the cpu prior to the place to search
  69  * @mask: the cpumask pointer
  70  * @start: the start point of the iteration
  71  * @wrap: assume @n crossing @start terminates the iteration
  72  *
  73  * Returns >= nr_cpu_ids on completion
  74  *
  75  * Note: the @wrap argument is required for the start condition when
  76  * we cannot assume @start is set in @mask.
  77  */
  78 int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
  79 {
  80         int next;
  81
  82 again:
  83         next = cpumask_next(n, mask);
  84
  85         if (wrap && n < start && next >= start) {
  86                 return nr_cpumask_bits;
  87
  88         } else if (next >= nr_cpumask_bits) {
  89                 wrap = true;
  90                 n = -1;
  91                 goto again;
  92         }
  93
  94         return next;
  95 }
  96 EXPORT_SYMBOL(cpumask_next_wrap);
  97
  98 /* These are not inline because of header tangles. */
  99 #ifdef CONFIG_CPUMASK_OFFSTACK
 100 /**
 101  * alloc_cpumask_var_node - allocate a struct cpumask on a given node
 102  * @mask: pointer to cpumask_var_t where the cpumask is returned
 103  * @flags: GFP_ flags
 104  *
 105  * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 106  * a nop returning a constant 1 (in <linux/cpumask.h>)
 107  * Returns TRUE if memory allocation succeeded, FALSE otherwise.
 108  *
 109  * In addition, mask will be NULL if this fails.  Note that gcc is
 110  * usually smart enough to know that mask can never be NULL if
 111  * CONFIG_CPUMASK_OFFSTACK=n, so does code elimination in that case
 112  * too.
 113  */
 114 bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
 115 {
 116         *mask = kmalloc_node(cpumask_size(), flags, node);
 117
 118 #ifdef CONFIG_DEBUG_PER_CPU_MAPS
 119         if (!*mask) {
 120                 printk(KERN_ERR "=> alloc_cpumask_var: failed!\n");
 121                 dump_stack();
 122         }
 123 #endif
 124
 125         return *mask != NULL;
 126 }
 127 EXPORT_SYMBOL(alloc_cpumask_var_node);
 128
 129 bool zalloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
 130 {
 131         return alloc_cpumask_var_node(mask, flags | __GFP_ZERO, node);
 132 }
 133 EXPORT_SYMBOL(zalloc_cpumask_var_node);
 134
 135 /**
 136  * alloc_cpumask_var - allocate a struct cpumask
 137  * @mask: pointer to cpumask_var_t where the cpumask is returned
 138  * @flags: GFP_ flags
 139  *
 140  * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 141  * a nop returning a constant 1 (in <linux/cpumask.h>).
 142  *
 143  * See alloc_cpumask_var_node.
 144  */
 145 bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
 146 {
 147         return alloc_cpumask_var_node(mask, flags, NUMA_NO_NODE);
 148 }
 149 EXPORT_SYMBOL(alloc_cpumask_var);
 150
 151 bool zalloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
 152 {
 153         return alloc_cpumask_var(mask, flags | __GFP_ZERO);
 154 }
 155 EXPORT_SYMBOL(zalloc_cpumask_var);
 156
 157 /**
 158  * alloc_bootmem_cpumask_var - allocate a struct cpumask from the bootmem arena.
 159  * @mask: pointer to cpumask_var_t where the cpumask is returned
 160  *
 161  * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 162  * a nop (in <linux/cpumask.h>).
 163  * Either returns an allocated (zero-filled) cpumask, or causes the
 164  * system to panic.
 165  */
 166 void __init alloc_bootmem_cpumask_var(cpumask_var_t *mask)
 167 {
 168         *mask = memblock_alloc(cpumask_size(), SMP_CACHE_BYTES);
 169         if (!*mask)
 170                 panic("%s: Failed to allocate %u bytes\n", __func__,
 171                       cpumask_size());
 172 }
 173
 174 /**
 175  * free_cpumask_var - frees memory allocated for a struct cpumask.
 176  * @mask: cpumask to free
 177  *
 178  * This is safe on a NULL mask.
 179  */
 180 void free_cpumask_var(cpumask_var_t mask)
 181 {
 182         kfree(mask);
 183 }
 184 EXPORT_SYMBOL(free_cpumask_var);
 185
 186 /**
 187  * free_bootmem_cpumask_var - frees result of alloc_bootmem_cpumask_var
 188  * @mask: cpumask to free
 189  */
 190 void __init free_bootmem_cpumask_var(cpumask_var_t mask)
 191 {
 192         memblock_free_early(__pa(mask), cpumask_size());
 193 }
 194 #endif
 195
 196 /**
 197  * cpumask_local_spread - select the i'th cpu with local numa cpu's first
 198  * @i: index number
 199  * @node: local numa_node
 200  *
 201  * This function selects an online CPU according to a numa aware policy;
 202  * local cpus are returned first, followed by non-local ones, then it
 203  * wraps around.
 204  *
 205  * It's not very efficient, but useful for setup.
 206  */
 207 unsigned int cpumask_local_spread(unsigned int i, int node)
 208 {
 209         int cpu, hk_flags;
 210         const struct cpumask *mask;
 211
 212         hk_flags = HK_FLAG_DOMAIN | HK_FLAG_MANAGED_IRQ;
 213         mask = housekeeping_cpumask(hk_flags);
 214         /* Wrap: we always want a cpu. */
 215         i %= cpumask_weight(mask);
 216
 217         if (node == NUMA_NO_NODE) {
 218                 for_each_cpu(cpu, mask) {
 219                         if (i-- == 0)
 220                                 return cpu;
 221                 }
 222         } else {
 223                 /* NUMA first. */
 224                 for_each_cpu_and(cpu, cpumask_of_node(node), mask) {
 225                         if (i-- == 0)
 226                                 return cpu;
 227                 }
 228
 229                 for_each_cpu(cpu, mask) {
 230                         /* Skip NUMA nodes, done above. */
 231                         if (cpumask_test_cpu(cpu, cpumask_of_node(node)))
 232                                 continue;
 233
 234                         if (i-- == 0)
 235                                 return cpu;
 236                 }
 237         }
 238         BUG();
 239 }
 240 EXPORT_SYMBOL(cpumask_local_spread);
 241
 242 static DEFINE_PER_CPU(int, distribute_cpu_mask_prev);
 243
 244 /**
 245  * Returns an arbitrary cpu within srcp1 & srcp2.
 246  *
 247  * Iterated calls using the same srcp1 and srcp2 will be distributed within
 248  * their intersection.
 249  *
 250  * Returns >= nr_cpu_ids if the intersection is empty.
 251  */
 252 int cpumask_any_and_distribute(const struct cpumask *src1p,
 253                                const struct cpumask *src2p)
 254 {
 255         int next, prev;
 256
 257         /* NOTE: our first selection will skip 0. */
 258         prev = __this_cpu_read(distribute_cpu_mask_prev);
 259
 260         next = cpumask_next_and(prev, src1p, src2p);
 261         if (next >= nr_cpu_ids)
 262                 next = cpumask_first_and(src1p, src2p);
 263
 264         if (next < nr_cpu_ids)
 265                 __this_cpu_write(distribute_cpu_mask_prev, next);
 266
 267         return next;
 268 }
 269 EXPORT_SYMBOL(cpumask_any_and_distribute);
 270
 271 int cpumask_any_distribute(const struct cpumask *srcp)
 272 {
 273         int next, prev;
 274
 275         /* NOTE: our first selection will skip 0. */
 276         prev = __this_cpu_read(distribute_cpu_mask_prev);
 277
 278         next = cpumask_next(prev, srcp);
 279         if (next >= nr_cpu_ids)
 280                 next = cpumask_first(srcp);
 281
 282         if (next < nr_cpu_ids)
 283                 __this_cpu_write(distribute_cpu_mask_prev, next);
 284
 285         return next;
 286 }
 287 EXPORT_SYMBOL(cpumask_any_distribute);