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1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/limits.h>
3#include <linux/module.h>
4
5/* validate @native and @pcp counter values match @expected */
6#define CHECK(native, pcp, expected) \
7 do { \
8 WARN((native) != (expected), \
9 "raw %ld (0x%lx) != expected %lld (0x%llx)", \
10 (native), (native), \
11 (long long)(expected), (long long)(expected)); \
12 WARN(__this_cpu_read(pcp) != (expected), \
13 "pcp %ld (0x%lx) != expected %lld (0x%llx)", \
14 __this_cpu_read(pcp), __this_cpu_read(pcp), \
15 (long long)(expected), (long long)(expected)); \
16 } while (0)
17
18static DEFINE_PER_CPU(long, long_counter);
19static DEFINE_PER_CPU(unsigned long, ulong_counter);
20
21static int __init percpu_test_init(void)
22{
23 /*
24 * volatile prevents compiler from optimizing it uses, otherwise the
25 * +ul_one/-ul_one below would replace with inc/dec instructions.
26 */
27 volatile unsigned int ui_one = 1;
28 unsigned long long ull = 0;
29 unsigned long ul = 0;
30 long l = 0;
31
32 pr_info("percpu test start\n");
33
34 preempt_disable();
35
36 l += -1;
37 __this_cpu_add(long_counter, -1);
38 CHECK(l, long_counter, -1);
39
40 l += 1;
41 __this_cpu_add(long_counter, 1);
42 CHECK(l, long_counter, 0);
43
44 ul = 0;
45 __this_cpu_write(ulong_counter, 0);
46
47 ul += 1UL;
48 __this_cpu_add(ulong_counter, 1UL);
49 CHECK(ul, ulong_counter, 1);
50
51 ul += -1UL;
52 __this_cpu_add(ulong_counter, -1UL);
53 CHECK(ul, ulong_counter, 0);
54
55 ul += -(unsigned long)1;
56 __this_cpu_add(ulong_counter, -(unsigned long)1);
57 CHECK(ul, ulong_counter, -1);
58
59 ul = 0;
60 __this_cpu_write(ulong_counter, 0);
61
62 ul -= 1;
63 __this_cpu_dec(ulong_counter);
64 CHECK(ul, ulong_counter, -1);
65 CHECK(ul, ulong_counter, ULONG_MAX);
66
67 l += -ui_one;
68 __this_cpu_add(long_counter, -ui_one);
69 CHECK(l, long_counter, 0xffffffff);
70
71 l += ui_one;
72 __this_cpu_add(long_counter, ui_one);
73 CHECK(l, long_counter, (long)0x100000000LL);
74
75
76 l = 0;
77 __this_cpu_write(long_counter, 0);
78
79 l -= ui_one;
80 __this_cpu_sub(long_counter, ui_one);
81 CHECK(l, long_counter, -1);
82
83 l = 0;
84 __this_cpu_write(long_counter, 0);
85
86 l += ui_one;
87 __this_cpu_add(long_counter, ui_one);
88 CHECK(l, long_counter, 1);
89
90 l += -ui_one;
91 __this_cpu_add(long_counter, -ui_one);
92 CHECK(l, long_counter, (long)0x100000000LL);
93
94 l = 0;
95 __this_cpu_write(long_counter, 0);
96
97 l -= ui_one;
98 this_cpu_sub(long_counter, ui_one);
99 CHECK(l, long_counter, -1);
100 CHECK(l, long_counter, ULONG_MAX);
101
102 ul = 0;
103 __this_cpu_write(ulong_counter, 0);
104
105 ul += ui_one;
106 __this_cpu_add(ulong_counter, ui_one);
107 CHECK(ul, ulong_counter, 1);
108
109 ul = 0;
110 __this_cpu_write(ulong_counter, 0);
111
112 ul -= ui_one;
113 __this_cpu_sub(ulong_counter, ui_one);
114 CHECK(ul, ulong_counter, -1);
115 CHECK(ul, ulong_counter, ULONG_MAX);
116
117 ul = ull = 0;
118 __this_cpu_write(ulong_counter, 0);
119
120 ul = ull += UINT_MAX;
121 __this_cpu_add(ulong_counter, ull);
122 CHECK(ul, ulong_counter, UINT_MAX);
123
124 ul = 3;
125 __this_cpu_write(ulong_counter, 3);
126
127 ul = this_cpu_sub_return(ulong_counter, ui_one);
128 CHECK(ul, ulong_counter, 2);
129
130 ul = __this_cpu_sub_return(ulong_counter, ui_one);
131 CHECK(ul, ulong_counter, 1);
132
133 preempt_enable();
134
135 pr_info("percpu test done\n");
136 return -EAGAIN; /* Fail will directly unload the module */
137}
138
139static void __exit percpu_test_exit(void)
140{
141}
142
143module_init(percpu_test_init)
144module_exit(percpu_test_exit)
145
146MODULE_LICENSE("GPL");
147MODULE_AUTHOR("Greg Thelen");
148MODULE_DESCRIPTION("percpu operations test");
149

source code of linux/lib/percpu_test.c