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