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
 10/* These are not inline because of header tangles. */
 11#ifdef CONFIG_CPUMASK_OFFSTACK
 12/**
 13 * alloc_cpumask_var_node - allocate a struct cpumask on a given node
 14 * @mask: pointer to cpumask_var_t where the cpumask is returned
 15 * @flags: GFP_ flags
 16 * @node: memory node from which to allocate or %NUMA_NO_NODE
 17 *
 18 * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 19 * a nop returning a constant 1 (in <linux/cpumask.h>).
 20 *
 21 * Return: TRUE if memory allocation succeeded, FALSE otherwise.
 22 *
 23 * In addition, mask will be NULL if this fails.  Note that gcc is
 24 * usually smart enough to know that mask can never be NULL if
 25 * CONFIG_CPUMASK_OFFSTACK=n, so does code elimination in that case
 26 * too.
 27 */
 28bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
 29{
 30	*mask = kmalloc_node(cpumask_size(), flags, node);
 31
 32#ifdef CONFIG_DEBUG_PER_CPU_MAPS
 33	if (!*mask) {
 34		printk(KERN_ERR "=> alloc_cpumask_var: failed!\n");
 35		dump_stack();
 36	}
 37#endif
 38
 39	return *mask != NULL;
 40}
 41EXPORT_SYMBOL(alloc_cpumask_var_node);
 42
 43/**
 44 * alloc_bootmem_cpumask_var - allocate a struct cpumask from the bootmem arena.
 45 * @mask: pointer to cpumask_var_t where the cpumask is returned
 46 *
 47 * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 48 * a nop (in <linux/cpumask.h>).
 49 * Either returns an allocated (zero-filled) cpumask, or causes the
 50 * system to panic.
 51 */
 52void __init alloc_bootmem_cpumask_var(cpumask_var_t *mask)
 53{
 54	*mask = memblock_alloc_or_panic(cpumask_size(), SMP_CACHE_BYTES);
 55}
 56
 57/**
 58 * free_cpumask_var - frees memory allocated for a struct cpumask.
 59 * @mask: cpumask to free
 60 *
 61 * This is safe on a NULL mask.
 62 */
 63void free_cpumask_var(cpumask_var_t mask)
 64{
 65	kfree(mask);
 66}
 67EXPORT_SYMBOL(free_cpumask_var);
 68
 69/**
 70 * free_bootmem_cpumask_var - frees result of alloc_bootmem_cpumask_var
 71 * @mask: cpumask to free
 72 */
 73void __init free_bootmem_cpumask_var(cpumask_var_t mask)
 74{
 75	memblock_free(mask, cpumask_size());
 76}
 77#endif
 78
 79/**
 80 * cpumask_local_spread - select the i'th cpu based on NUMA distances
 81 * @i: index number
 82 * @node: local numa_node
 83 *
 84 * Return: online CPU according to a numa aware policy; local cpus are returned
 85 * first, followed by non-local ones, then it wraps around.
 86 *
 87 * For those who wants to enumerate all CPUs based on their NUMA distances,
 88 * i.e. call this function in a loop, like:
 89 *
 90 * for (i = 0; i < num_online_cpus(); i++) {
 91 *	cpu = cpumask_local_spread(i, node);
 92 *	do_something(cpu);
 93 * }
 94 *
 95 * There's a better alternative based on for_each()-like iterators:
 96 *
 97 *	for_each_numa_hop_mask(mask, node) {
 98 *		for_each_cpu_andnot(cpu, mask, prev)
 99 *			do_something(cpu);
100 *		prev = mask;
101 *	}
102 *
103 * It's simpler and more verbose than above. Complexity of iterator-based
104 * enumeration is O(sched_domains_numa_levels * nr_cpu_ids), while
105 * cpumask_local_spread() when called for each cpu is
106 * O(sched_domains_numa_levels * nr_cpu_ids * log(nr_cpu_ids)).
107 */
108unsigned int cpumask_local_spread(unsigned int i, int node)
109{
110	unsigned int cpu;
111
112	/* Wrap: we always want a cpu. */
113	i %= num_online_cpus();
114
115	cpu = sched_numa_find_nth_cpu(cpu_online_mask, i, node);
116
117	WARN_ON(cpu >= nr_cpu_ids);
118	return cpu;
119}
120EXPORT_SYMBOL(cpumask_local_spread);
121
122static DEFINE_PER_CPU(int, distribute_cpu_mask_prev);
123
124/**
125 * cpumask_any_and_distribute - Return an arbitrary cpu within src1p & src2p.
126 * @src1p: first &cpumask for intersection
127 * @src2p: second &cpumask for intersection
128 *
129 * Iterated calls using the same srcp1 and srcp2 will be distributed within
130 * their intersection.
131 *
132 * Return: >= nr_cpu_ids if the intersection is empty.
133 */
134unsigned int cpumask_any_and_distribute(const struct cpumask *src1p,
135			       const struct cpumask *src2p)
136{
137	unsigned int next, prev;
138
139	/* NOTE: our first selection will skip 0. */
140	prev = __this_cpu_read(distribute_cpu_mask_prev);
141
142	next = cpumask_next_and_wrap(prev, src1p, src2p);
143	if (next < nr_cpu_ids)
144		__this_cpu_write(distribute_cpu_mask_prev, next);
145
146	return next;
147}
148EXPORT_SYMBOL(cpumask_any_and_distribute);
149
150/**
151 * cpumask_any_distribute - Return an arbitrary cpu from srcp
152 * @srcp: &cpumask for selection
153 *
154 * Return: >= nr_cpu_ids if the intersection is empty.
155 */
156unsigned int cpumask_any_distribute(const struct cpumask *srcp)
157{
158	unsigned int next, prev;
159
160	/* NOTE: our first selection will skip 0. */
161	prev = __this_cpu_read(distribute_cpu_mask_prev);
162	next = cpumask_next_wrap(prev, srcp);
163	if (next < nr_cpu_ids)
164		__this_cpu_write(distribute_cpu_mask_prev, next);
165
166	return next;
167}
168EXPORT_SYMBOL(cpumask_any_distribute);