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