// SPDX-License-Identifier: GPL-2.0-only#include <linux/limits.h>#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;	unsigned long long ull = 0;	unsigned long ul = 0;	long l = 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 = ull = 0;	__this_cpu_write(ulong_counter, 0); 	ul = ull += UINT_MAX;	__this_cpu_add(ulong_counter, ull);	CHECK(ul, ulong_counter, UINT_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");