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#include <linux/compiler.h>
#include "../tests.h"
typedef struct _buf {
char data1;
char reserved[55];
char data2;
} buf __attribute__((aligned(64)));
static buf buf1 = {
/* to have this in the data section */
.reserved[0] = 1,
};
static int datasym(int argc __maybe_unused, const char **argv __maybe_unused)
{
for (;;) {
buf1.data1++;
if (buf1.data1 == 123) {
/*
* Add some 'noise' in the loop to work around errata
* 1694299 on Arm N1.
*
* Bias exists in SPE sampling which can cause the load
* and store instructions to be skipped entirely. This
* comes and goes randomly depending on the offset the
* linker places the datasym loop at in the Perf binary.
* With an extra branch in the middle of the loop that
* isn't always taken, the instruction stream is no
* longer a continuous repeating pattern that interacts
* badly with the bias.
*/
buf1.data1++;
}
buf1.data2 += buf1.data1;
}
return 0;
}
DEFINE_WORKLOAD(datasym);
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