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
16 static DEFINE_PER_CPU(long, long_counter);
17 static DEFINE_PER_CPU(unsigned long, ulong_counter);
18
percpu_test_init(void)19 static 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
percpu_test_exit(void)129 static void __exit percpu_test_exit(void)
130 {
131 }
132
133 module_init(percpu_test_init)
134 module_exit(percpu_test_exit)
135
136 MODULE_LICENSE("GPL");
137 MODULE_AUTHOR("Greg Thelen");
138 MODULE_DESCRIPTION("percpu operations test");
139