Root/lib/percpu_test.c

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

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