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 | * Return: >= 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 | */ |
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, srcp: 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 | * |
53 | * Return: TRUE if memory allocation succeeded, FALSE otherwise. |
54 | * |
55 | * In addition, mask will be NULL if this fails. Note that gcc is |
56 | * usually smart enough to know that mask can never be NULL if |
57 | * CONFIG_CPUMASK_OFFSTACK=n, so does code elimination in that case |
58 | * too. |
59 | */ |
60 | bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node) |
61 | { |
62 | *mask = kmalloc_node(size: cpumask_size(), flags, node); |
63 | |
64 | #ifdef CONFIG_DEBUG_PER_CPU_MAPS |
65 | if (!*mask) { |
66 | printk(KERN_ERR "=> alloc_cpumask_var: failed!\n" ); |
67 | dump_stack(); |
68 | } |
69 | #endif |
70 | |
71 | return *mask != NULL; |
72 | } |
73 | EXPORT_SYMBOL(alloc_cpumask_var_node); |
74 | |
75 | /** |
76 | * alloc_bootmem_cpumask_var - allocate a struct cpumask from the bootmem arena. |
77 | * @mask: pointer to cpumask_var_t where the cpumask is returned |
78 | * |
79 | * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is |
80 | * a nop (in <linux/cpumask.h>). |
81 | * Either returns an allocated (zero-filled) cpumask, or causes the |
82 | * system to panic. |
83 | */ |
84 | void __init alloc_bootmem_cpumask_var(cpumask_var_t *mask) |
85 | { |
86 | *mask = memblock_alloc(size: cpumask_size(), SMP_CACHE_BYTES); |
87 | if (!*mask) |
88 | panic(fmt: "%s: Failed to allocate %u bytes\n" , __func__, |
89 | cpumask_size()); |
90 | } |
91 | |
92 | /** |
93 | * free_cpumask_var - frees memory allocated for a struct cpumask. |
94 | * @mask: cpumask to free |
95 | * |
96 | * This is safe on a NULL mask. |
97 | */ |
98 | void free_cpumask_var(cpumask_var_t mask) |
99 | { |
100 | kfree(objp: mask); |
101 | } |
102 | EXPORT_SYMBOL(free_cpumask_var); |
103 | |
104 | /** |
105 | * free_bootmem_cpumask_var - frees result of alloc_bootmem_cpumask_var |
106 | * @mask: cpumask to free |
107 | */ |
108 | void __init free_bootmem_cpumask_var(cpumask_var_t mask) |
109 | { |
110 | memblock_free(ptr: mask, size: cpumask_size()); |
111 | } |
112 | #endif |
113 | |
114 | /** |
115 | * cpumask_local_spread - select the i'th cpu based on NUMA distances |
116 | * @i: index number |
117 | * @node: local numa_node |
118 | * |
119 | * Return: online CPU according to a numa aware policy; local cpus are returned |
120 | * first, followed by non-local ones, then it wraps around. |
121 | * |
122 | * For those who wants to enumerate all CPUs based on their NUMA distances, |
123 | * i.e. call this function in a loop, like: |
124 | * |
125 | * for (i = 0; i < num_online_cpus(); i++) { |
126 | * cpu = cpumask_local_spread(i, node); |
127 | * do_something(cpu); |
128 | * } |
129 | * |
130 | * There's a better alternative based on for_each()-like iterators: |
131 | * |
132 | * for_each_numa_hop_mask(mask, node) { |
133 | * for_each_cpu_andnot(cpu, mask, prev) |
134 | * do_something(cpu); |
135 | * prev = mask; |
136 | * } |
137 | * |
138 | * It's simpler and more verbose than above. Complexity of iterator-based |
139 | * enumeration is O(sched_domains_numa_levels * nr_cpu_ids), while |
140 | * cpumask_local_spread() when called for each cpu is |
141 | * O(sched_domains_numa_levels * nr_cpu_ids * log(nr_cpu_ids)). |
142 | */ |
143 | unsigned int cpumask_local_spread(unsigned int i, int node) |
144 | { |
145 | unsigned int cpu; |
146 | |
147 | /* Wrap: we always want a cpu. */ |
148 | i %= num_online_cpus(); |
149 | |
150 | cpu = sched_numa_find_nth_cpu(cpu_online_mask, cpu: i, node); |
151 | |
152 | WARN_ON(cpu >= nr_cpu_ids); |
153 | return cpu; |
154 | } |
155 | EXPORT_SYMBOL(cpumask_local_spread); |
156 | |
157 | static DEFINE_PER_CPU(int, distribute_cpu_mask_prev); |
158 | |
159 | /** |
160 | * cpumask_any_and_distribute - Return an arbitrary cpu within src1p & src2p. |
161 | * @src1p: first &cpumask for intersection |
162 | * @src2p: second &cpumask for intersection |
163 | * |
164 | * Iterated calls using the same srcp1 and srcp2 will be distributed within |
165 | * their intersection. |
166 | * |
167 | * Return: >= nr_cpu_ids if the intersection is empty. |
168 | */ |
169 | unsigned int cpumask_any_and_distribute(const struct cpumask *src1p, |
170 | const struct cpumask *src2p) |
171 | { |
172 | unsigned int next, prev; |
173 | |
174 | /* NOTE: our first selection will skip 0. */ |
175 | prev = __this_cpu_read(distribute_cpu_mask_prev); |
176 | |
177 | next = find_next_and_bit_wrap(cpumask_bits(src1p), cpumask_bits(src2p), |
178 | nr_cpumask_bits, offset: prev + 1); |
179 | if (next < nr_cpu_ids) |
180 | __this_cpu_write(distribute_cpu_mask_prev, next); |
181 | |
182 | return next; |
183 | } |
184 | EXPORT_SYMBOL(cpumask_any_and_distribute); |
185 | |
186 | /** |
187 | * cpumask_any_distribute - Return an arbitrary cpu from srcp |
188 | * @srcp: &cpumask for selection |
189 | * |
190 | * Return: >= nr_cpu_ids if the intersection is empty. |
191 | */ |
192 | unsigned int cpumask_any_distribute(const struct cpumask *srcp) |
193 | { |
194 | unsigned int next, prev; |
195 | |
196 | /* NOTE: our first selection will skip 0. */ |
197 | prev = __this_cpu_read(distribute_cpu_mask_prev); |
198 | next = find_next_bit_wrap(cpumask_bits(srcp), nr_cpumask_bits, offset: prev + 1); |
199 | if (next < nr_cpu_ids) |
200 | __this_cpu_write(distribute_cpu_mask_prev, next); |
201 | |
202 | return next; |
203 | } |
204 | EXPORT_SYMBOL(cpumask_any_distribute); |
205 | |