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 /**
11 * cpumask_next_wrap - helper to implement for_each_cpu_wrap
12 * @n: the cpu prior to the place to search
13 * @mask: the cpumask pointer
14 * @start: the start point of the iteration
15 * @wrap: assume @n crossing @start terminates the iteration
16 *
17 * Returns >= nr_cpu_ids on completion
18 *
19 * Note: the @wrap argument is required for the start condition when
20 * we cannot assume @start is set in @mask.
21 */
cpumask_next_wrap(int n,const struct cpumask * mask,int start,bool wrap)22 unsigned int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
23 {
24 unsigned int next;
25
26 again:
27 next = cpumask_next(n, mask);
28
29 if (wrap && n < start && next >= start) {
30 return nr_cpumask_bits;
31
32 } else if (next >= nr_cpumask_bits) {
33 wrap = true;
34 n = -1;
35 goto again;
36 }
37
38 return next;
39 }
40 EXPORT_SYMBOL(cpumask_next_wrap);
41
42 /* These are not inline because of header tangles. */
43 #ifdef CONFIG_CPUMASK_OFFSTACK
44 /**
45 * alloc_cpumask_var_node - allocate a struct cpumask on a given node
46 * @mask: pointer to cpumask_var_t where the cpumask is returned
47 * @flags: GFP_ flags
48 * @node: memory node from which to allocate or %NUMA_NO_NODE
49 *
50 * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
51 * a nop returning a constant 1 (in <linux/cpumask.h>)
52 * Returns TRUE if memory allocation succeeded, FALSE otherwise.
53 *
54 * In addition, mask will be NULL if this fails. Note that gcc is
55 * usually smart enough to know that mask can never be NULL if
56 * CONFIG_CPUMASK_OFFSTACK=n, so does code elimination in that case
57 * too.
58 */
alloc_cpumask_var_node(cpumask_var_t * mask,gfp_t flags,int node)59 bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
60 {
61 *mask = kmalloc_node(cpumask_size(), flags, node);
62
63 #ifdef CONFIG_DEBUG_PER_CPU_MAPS
64 if (!*mask) {
65 printk(KERN_ERR "=> alloc_cpumask_var: failed!\n");
66 dump_stack();
67 }
68 #endif
69
70 return *mask != NULL;
71 }
72 EXPORT_SYMBOL(alloc_cpumask_var_node);
73
74 /**
75 * alloc_bootmem_cpumask_var - allocate a struct cpumask from the bootmem arena.
76 * @mask: pointer to cpumask_var_t where the cpumask is returned
77 *
78 * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
79 * a nop (in <linux/cpumask.h>).
80 * Either returns an allocated (zero-filled) cpumask, or causes the
81 * system to panic.
82 */
alloc_bootmem_cpumask_var(cpumask_var_t * mask)83 void __init alloc_bootmem_cpumask_var(cpumask_var_t *mask)
84 {
85 *mask = memblock_alloc(cpumask_size(), SMP_CACHE_BYTES);
86 if (!*mask)
87 panic("%s: Failed to allocate %u bytes\n", __func__,
88 cpumask_size());
89 }
90
91 /**
92 * free_cpumask_var - frees memory allocated for a struct cpumask.
93 * @mask: cpumask to free
94 *
95 * This is safe on a NULL mask.
96 */
free_cpumask_var(cpumask_var_t mask)97 void free_cpumask_var(cpumask_var_t mask)
98 {
99 kfree(mask);
100 }
101 EXPORT_SYMBOL(free_cpumask_var);
102
103 /**
104 * free_bootmem_cpumask_var - frees result of alloc_bootmem_cpumask_var
105 * @mask: cpumask to free
106 */
free_bootmem_cpumask_var(cpumask_var_t mask)107 void __init free_bootmem_cpumask_var(cpumask_var_t mask)
108 {
109 memblock_free(mask, cpumask_size());
110 }
111 #endif
112
113 /**
114 * cpumask_local_spread - select the i'th cpu based on NUMA distances
115 * @i: index number
116 * @node: local numa_node
117 *
118 * Returns online CPU according to a numa aware policy; local cpus are returned
119 * first, followed by non-local ones, then it wraps around.
120 *
121 * For those who wants to enumerate all CPUs based on their NUMA distances,
122 * i.e. call this function in a loop, like:
123 *
124 * for (i = 0; i < num_online_cpus(); i++) {
125 * cpu = cpumask_local_spread(i, node);
126 * do_something(cpu);
127 * }
128 *
129 * There's a better alternative based on for_each()-like iterators:
130 *
131 * for_each_numa_hop_mask(mask, node) {
132 * for_each_cpu_andnot(cpu, mask, prev)
133 * do_something(cpu);
134 * prev = mask;
135 * }
136 *
137 * It's simpler and more verbose than above. Complexity of iterator-based
138 * enumeration is O(sched_domains_numa_levels * nr_cpu_ids), while
139 * cpumask_local_spread() when called for each cpu is
140 * O(sched_domains_numa_levels * nr_cpu_ids * log(nr_cpu_ids)).
141 */
cpumask_local_spread(unsigned int i,int node)142 unsigned int cpumask_local_spread(unsigned int i, int node)
143 {
144 unsigned int cpu;
145
146 /* Wrap: we always want a cpu. */
147 i %= num_online_cpus();
148
149 cpu = (node == NUMA_NO_NODE) ?
150 cpumask_nth(i, cpu_online_mask) :
151 sched_numa_find_nth_cpu(cpu_online_mask, i, node);
152
153 WARN_ON(cpu >= nr_cpu_ids);
154 return cpu;
155 }
156 EXPORT_SYMBOL(cpumask_local_spread);
157
158 static DEFINE_PER_CPU(int, distribute_cpu_mask_prev);
159
160 /**
161 * cpumask_any_and_distribute - Return an arbitrary cpu within src1p & src2p.
162 * @src1p: first &cpumask for intersection
163 * @src2p: second &cpumask for intersection
164 *
165 * Iterated calls using the same srcp1 and srcp2 will be distributed within
166 * their intersection.
167 *
168 * Returns >= nr_cpu_ids if the intersection is empty.
169 */
cpumask_any_and_distribute(const struct cpumask * src1p,const struct cpumask * src2p)170 unsigned int cpumask_any_and_distribute(const struct cpumask *src1p,
171 const struct cpumask *src2p)
172 {
173 unsigned int next, prev;
174
175 /* NOTE: our first selection will skip 0. */
176 prev = __this_cpu_read(distribute_cpu_mask_prev);
177
178 next = find_next_and_bit_wrap(cpumask_bits(src1p), cpumask_bits(src2p),
179 nr_cpumask_bits, prev + 1);
180 if (next < nr_cpu_ids)
181 __this_cpu_write(distribute_cpu_mask_prev, next);
182
183 return next;
184 }
185 EXPORT_SYMBOL(cpumask_any_and_distribute);
186
cpumask_any_distribute(const struct cpumask * srcp)187 unsigned int cpumask_any_distribute(const struct cpumask *srcp)
188 {
189 unsigned int next, prev;
190
191 /* NOTE: our first selection will skip 0. */
192 prev = __this_cpu_read(distribute_cpu_mask_prev);
193 next = find_next_bit_wrap(cpumask_bits(srcp), nr_cpumask_bits, prev + 1);
194 if (next < nr_cpu_ids)
195 __this_cpu_write(distribute_cpu_mask_prev, next);
196
197 return next;
198 }
199 EXPORT_SYMBOL(cpumask_any_distribute);
200
