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[111.220.24.150]) by smtp.googlemail.com with ESMTPSA id z25sm1398808pfa.213.2020.04.22.22.54.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Apr 2020 22:54:56 -0700 (PDT) Message-ID: <0ad1e32c27a7e4d14e992eee03587f3cd0fd76eb.camel@gmail.com> Subject: Re: [PATCH 3/3] selftests/powerpc: ensure PMC reads are set and ordered on count_pmc From: Rashmica Gupta To: "Desnes A. Nunes do Rosario" , linuxppc-dev@lists.ozlabs.org Date: Thu, 23 Apr 2020 15:54:51 +1000 In-Reply-To: <20200408223543.21168-4-desnesn@linux.ibm.com> References: <20200408223543.21168-1-desnesn@linux.ibm.com> <20200408223543.21168-4-desnesn@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.32.5 (3.32.5-1.fc30) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: shuah@kernel.org, gromero@linux.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, 2020-04-08 at 19:35 -0300, Desnes A. Nunes do Rosario wrote: > 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 Reviewed-by: Rashmica Gupta > --- > 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