Function count_pmc() needs a memory barrier to ensure that PMC reads are
fully consistent. The lack of it can occasionally fail pmc56_overflow test,
since depending on the workload on the system, PMC5 & 6 can have past val-
ues from the time the counters are frozen and turned back on. These past
values will be accounted as overflows and make the test fail.
=========
test: pmc56_overflow
...
ebb_state:
...
>>pmc[5] count = 0xfd4cbc8c
>>pmc[6] count = 0xddd8b3b6
HW state:
MMCR0 0x0000000084000000 FC PMAE
MMCR2 0x0000000000000000
EBBHR 0x0000000010003f68
BESCR 0x8000000000000000 GE
...
PMC5 0x0000000000000000
PMC6 0x0000000000000000
SIAR 0x0000000010003398
...
[3]: register SPRN_PMC2 = 0x0000000080000003
[4]: register SPRN_PMC5 = 0x0000000000000000
[5]: register SPRN_PMC6 = 0x0000000000000000
[6]: register SPRN_PMC2 = 0x0000000080000003
>>[7]: register SPRN_PMC5 = 0x000000008f21266d
>>[8]: register SPRN_PMC6 = 0x000000000da80f8d
[9]: register SPRN_PMC2 = 0x0000000080000003
>>[10]: register SPRN_PMC5 = 0x000000006e2b961f
>>[11]: register SPRN_PMC6 = 0x00000000d030a429
[12]: register SPRN_PMC2 = 0x0000000080000003
[13]: register SPRN_PMC5 = 0x0000000000000000
[14]: register SPRN_PMC6 = 0x0000000000000000
...
PMC5/6 overflow 2
[FAIL] Test FAILED on line 87
failure: pmc56_overflow
=========
Signed-off-by: Desnes A. Nunes do Rosario <desn...@linux.ibm.com>
---
tools/testing/selftests/powerpc/pmu/ebb/ebb.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/tools/testing/selftests/powerpc/pmu/ebb/ebb.c
b/tools/testing/selftests/powerpc/pmu/ebb/ebb.c
index bf6f25dfcf7b..6199f3cea0f9 100644
--- a/tools/testing/selftests/powerpc/pmu/ebb/ebb.c
+++ b/tools/testing/selftests/powerpc/pmu/ebb/ebb.c
@@ -258,6 +258,10 @@ int count_pmc(int pmc, uint32_t sample_period)
start_value = pmc_sample_period(sample_period);
val = read_pmc(pmc);
+
+ /* Ensure pmc value is consistent between freezes */
+ mb();
+
if (val < start_value)
ebb_state.stats.negative++;
else
--
2.21.1
