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@@ -0,0 +1,138 @@
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+#include <linux/module.h>
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+
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+/* validate @native and @pcp counter values match @expected */
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+#define CHECK(native, pcp, expected) \
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+ do { \
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+ WARN((native) != (expected), \
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+ "raw %ld (0x%lx) != expected %lld (0x%llx)", \
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+ (native), (native), \
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+ (long long)(expected), (long long)(expected)); \
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+ WARN(__this_cpu_read(pcp) != (expected), \
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+ "pcp %ld (0x%lx) != expected %lld (0x%llx)", \
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+ __this_cpu_read(pcp), __this_cpu_read(pcp), \
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+ (long long)(expected), (long long)(expected)); \
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+ } while (0)
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+
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+static DEFINE_PER_CPU(long, long_counter);
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+static DEFINE_PER_CPU(unsigned long, ulong_counter);
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+
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+static int __init percpu_test_init(void)
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+{
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+ /*
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+ * volatile prevents compiler from optimizing it uses, otherwise the
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+ * +ul_one/-ul_one below would replace with inc/dec instructions.
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+ */
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+ volatile unsigned int ui_one = 1;
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+ long l = 0;
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+ unsigned long ul = 0;
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+
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+ pr_info("percpu test start\n");
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+
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+ preempt_disable();
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+
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+ l += -1;
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+ __this_cpu_add(long_counter, -1);
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+ CHECK(l, long_counter, -1);
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+
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+ l += 1;
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+ __this_cpu_add(long_counter, 1);
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+ CHECK(l, long_counter, 0);
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+
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+ ul = 0;
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+ __this_cpu_write(ulong_counter, 0);
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+
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+ ul += 1UL;
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+ __this_cpu_add(ulong_counter, 1UL);
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+ CHECK(ul, ulong_counter, 1);
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+
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+ ul += -1UL;
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+ __this_cpu_add(ulong_counter, -1UL);
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+ CHECK(ul, ulong_counter, 0);
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+
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+ ul += -(unsigned long)1;
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+ __this_cpu_add(ulong_counter, -(unsigned long)1);
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+ CHECK(ul, ulong_counter, -1);
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+
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+ ul = 0;
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+ __this_cpu_write(ulong_counter, 0);
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+
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+ ul -= 1;
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+ __this_cpu_dec(ulong_counter);
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+ CHECK(ul, ulong_counter, -1);
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+ CHECK(ul, ulong_counter, ULONG_MAX);
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+
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+ l += -ui_one;
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+ __this_cpu_add(long_counter, -ui_one);
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+ CHECK(l, long_counter, 0xffffffff);
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+
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+ l += ui_one;
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+ __this_cpu_add(long_counter, ui_one);
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+ CHECK(l, long_counter, (long)0x100000000LL);
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+
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+
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+ l = 0;
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+ __this_cpu_write(long_counter, 0);
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+
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+ l -= ui_one;
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+ __this_cpu_sub(long_counter, ui_one);
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+ CHECK(l, long_counter, -1);
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+
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+ l = 0;
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+ __this_cpu_write(long_counter, 0);
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+
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+ l += ui_one;
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+ __this_cpu_add(long_counter, ui_one);
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+ CHECK(l, long_counter, 1);
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+
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+ l += -ui_one;
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+ __this_cpu_add(long_counter, -ui_one);
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+ CHECK(l, long_counter, (long)0x100000000LL);
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+
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+ l = 0;
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+ __this_cpu_write(long_counter, 0);
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+
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+ l -= ui_one;
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+ this_cpu_sub(long_counter, ui_one);
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+ CHECK(l, long_counter, -1);
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+ CHECK(l, long_counter, ULONG_MAX);
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+
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+ ul = 0;
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+ __this_cpu_write(ulong_counter, 0);
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+
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+ ul += ui_one;
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+ __this_cpu_add(ulong_counter, ui_one);
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+ CHECK(ul, ulong_counter, 1);
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+
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+ ul = 0;
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+ __this_cpu_write(ulong_counter, 0);
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+
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+ ul -= ui_one;
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+ __this_cpu_sub(ulong_counter, ui_one);
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+ CHECK(ul, ulong_counter, -1);
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+ CHECK(ul, ulong_counter, ULONG_MAX);
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+
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+ ul = 3;
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+ __this_cpu_write(ulong_counter, 3);
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+
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+ ul = this_cpu_sub_return(ulong_counter, ui_one);
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+ CHECK(ul, ulong_counter, 2);
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+
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+ ul = __this_cpu_sub_return(ulong_counter, ui_one);
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+ CHECK(ul, ulong_counter, 1);
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+
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+ preempt_enable();
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+
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+ pr_info("percpu test done\n");
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+ return -EAGAIN; /* Fail will directly unload the module */
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+}
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+
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+static void __exit percpu_test_exit(void)
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+{
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+}
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+
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+module_init(percpu_test_init)
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+module_exit(percpu_test_exit)
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+
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+MODULE_LICENSE("GPL");
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+MODULE_AUTHOR("Greg Thelen");
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+MODULE_DESCRIPTION("percpu operations test");
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