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selftests/bpf: improve reliability of test_perf_branches_no_hw() #10334

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selftests/bpf: improve reliability of test_perf_branches_no_hw() #10334

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16 changes: 14 additions & 2 deletions tools/testing/selftests/bpf/prog_tests/perf_branches.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,10 @@ static void check_good_sample(struct test_perf_branches *skel)
int pbe_size = sizeof(struct perf_branch_entry);
int duration = 0;

if (CHECK(!skel->bss->run_cnt, "invalid run_cnt",
"checked sample validity before prog run"))
return;

if (CHECK(!skel->bss->valid, "output not valid",
"no valid sample from prog"))
return;
Expand Down Expand Up @@ -45,6 +49,10 @@ static void check_bad_sample(struct test_perf_branches *skel)
int written_stack = skel->bss->written_stack_out;
int duration = 0;

if (CHECK(!skel->bss->run_cnt, "invalid run_cnt",
"checked sample validity before prog run"))
return;

if (CHECK(!skel->bss->valid, "output not valid",
"no valid sample from prog"))
return;
Expand Down Expand Up @@ -83,8 +91,12 @@ static void test_perf_branches_common(int perf_fd,
err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set), &cpu_set);
if (CHECK(err, "set_affinity", "cpu #0, err %d\n", err))
goto out_destroy;
/* spin the loop for a while (random high number) */
for (i = 0; i < 1000000; ++i)

/* Spin the loop for a while by using a high iteration count, and by
* checking whether the specific run count marker has been explicitly
* incremented at least once by the backing perf_event BPF program.
*/
for (i = 0; i < 100000000 && !*(volatile int *)&skel->bss->run_cnt; ++i)
++j;

test_perf_branches__detach(skel);
Expand Down
3 changes: 3 additions & 0 deletions tools/testing/selftests/bpf/progs/test_perf_branches.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
#include <bpf/bpf_tracing.h>

int valid = 0;
int run_cnt = 0;
int required_size_out = 0;
int written_stack_out = 0;
int written_global_out = 0;
Expand All @@ -24,6 +25,8 @@ int perf_branches(void *ctx)
__u64 entries[4 * 3] = {0};
int required_size, written_stack, written_global;

++run_cnt;

/* write to stack */
written_stack = bpf_read_branch_records(ctx, entries, sizeof(entries), 0);
/* ignore spurious events */
Expand Down
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