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