aboutsummaryrefslogtreecommitdiff
path: root/lib/percpu_test.c
blob: 0b5d14dadd1a3f256e50ea4929d739540b2962ed (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
#include <linux/module.h>

/* validate @native and @pcp counter values match @expected */
#define CHECK(native, pcp, expected)                                    \
	do {                                                            \
		WARN((native) != (expected),                            \
		     "raw %ld (0x%lx) != expected %lld (0x%llx)",	\
		     (native), (native),				\
		     (long long)(expected), (long long)(expected));	\
		WARN(__this_cpu_read(pcp) != (expected),                \
		     "pcp %ld (0x%lx) != expected %lld (0x%llx)",	\
		     __this_cpu_read(pcp), __this_cpu_read(pcp),	\
		     (long long)(expected), (long long)(expected));	\
	} while (0)

static DEFINE_PER_CPU(long, long_counter);
static DEFINE_PER_CPU(unsigned long, ulong_counter);

static int __init percpu_test_init(void)
{
	/*
	 * volatile prevents compiler from optimizing it uses, otherwise the
	 * +ul_one/-ul_one below would replace with inc/dec instructions.
	 */
	volatile unsigned int ui_one = 1;
	long l = 0;
	unsigned long ul = 0;

	pr_info("percpu test start\n");

	preempt_disable();

	l += -1;
	__this_cpu_add(long_counter, -1);
	CHECK(l, long_counter, -1);

	l += 1;
	__this_cpu_add(long_counter, 1);
	CHECK(l, long_counter, 0);

	ul = 0;
	__this_cpu_write(ulong_counter, 0);

	ul += 1UL;
	__this_cpu_add(ulong_counter, 1UL);
	CHECK(ul, ulong_counter, 1);

	ul += -1UL;
	__this_cpu_add(ulong_counter, -1UL);
	CHECK(ul, ulong_counter, 0);

	ul += -(unsigned long)1;
	__this_cpu_add(ulong_counter, -(unsigned long)1);
	CHECK(ul, ulong_counter, -1);

	ul = 0;
	__this_cpu_write(ulong_counter, 0);

	ul -= 1;
	__this_cpu_dec(ulong_counter);
	CHECK(ul, ulong_counter, -1);
	CHECK(ul, ulong_counter, ULONG_MAX);

	l += -ui_one;
	__this_cpu_add(long_counter, -ui_one);
	CHECK(l, long_counter, 0xffffffff);

	l += ui_one;
	__this_cpu_add(long_counter, ui_one);
	CHECK(l, long_counter, (long)0x100000000LL);


	l = 0;
	__this_cpu_write(long_counter, 0);

	l -= ui_one;
	__this_cpu_sub(long_counter, ui_one);
	CHECK(l, long_counter, -1);

	l = 0;
	__this_cpu_write(long_counter, 0);

	l += ui_one;
	__this_cpu_add(long_counter, ui_one);
	CHECK(l, long_counter, 1);

	l += -ui_one;
	__this_cpu_add(long_counter, -ui_one);
	CHECK(l, long_counter, (long)0x100000000LL);

	l = 0;
	__this_cpu_write(long_counter, 0);

	l -= ui_one;
	this_cpu_sub(long_counter, ui_one);
	CHECK(l, long_counter, -1);
	CHECK(l, long_counter, ULONG_MAX);

	ul = 0;
	__this_cpu_write(ulong_counter, 0);

	ul += ui_one;
	__this_cpu_add(ulong_counter, ui_one);
	CHECK(ul, ulong_counter, 1);

	ul = 0;
	__this_cpu_write(ulong_counter, 0);

	ul -= ui_one;
	__this_cpu_sub(ulong_counter, ui_one);
	CHECK(ul, ulong_counter, -1);
	CHECK(ul, ulong_counter, ULONG_MAX);

	ul = 3;
	__this_cpu_write(ulong_counter, 3);

	ul = this_cpu_sub_return(ulong_counter, ui_one);
	CHECK(ul, ulong_counter, 2);

	ul = __this_cpu_sub_return(ulong_counter, ui_one);
	CHECK(ul, ulong_counter, 1);

	preempt_enable();

	pr_info("percpu test done\n");
	return -EAGAIN;  /* Fail will directly unload the module */
}

static void __exit percpu_test_exit(void)
{
}

module_init(percpu_test_init)
module_exit(percpu_test_exit)

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Greg Thelen");
MODULE_DESCRIPTION("percpu operations test");