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");