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Subject: Re: [PATCH v2 0/4] Fix perf bench numa, futex and epoll to work with
 machines having #CPUs > 1K
From:   Athira Rajeev <atrajeev@linux.vnet.ibm.com>
In-Reply-To: <YlG/1cegJ3Fh/zj/@kernel.org>
Date:   Tue, 12 Apr 2022 22:03:14 +0530
Cc:     Ian Rogers <irogers@google.com>, maddy@linux.vnet.ibm.com,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        Nageswara Sastry <rnsastry@linux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-perf-users@vger.kernel.org, Jiri Olsa <jolsa@kernel.org>,
        kajoljain <kjain@linux.ibm.com>, disgoel@linux.vnet.ibm.com,
        linuxppc-dev@lists.ozlabs.org
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Message-Id: <64B99006-B94E-485E-8382-91E50244A5E4@linux.vnet.ibm.com>
References: <20220406175113.87881-1-atrajeev@linux.vnet.ibm.com>
 <YlGmAd3LEh9He6Pg@kernel.org> <YlG/1cegJ3Fh/zj/@kernel.org>
To:     Arnaldo Carvalho de Melo <acme@kernel.org>
Precedence: bulk


> On 09-Apr-2022, at 10:48 PM, Arnaldo Carvalho de Melo =
<acme@kernel.org> wrote:
>=20
> Em Sat, Apr 09, 2022 at 12:28:01PM -0300, Arnaldo Carvalho de Melo =
escreveu:
>> Em Wed, Apr 06, 2022 at 11:21:09PM +0530, Athira Rajeev escreveu:
>>> The perf benchmark for collections: numa, futex and epoll
>>> hits failure in system configuration with CPU's more than 1024.
>>> These benchmarks uses "sched_getaffinity" and "sched_setaffinity"
>>> in the code to work with affinity.
>>=20
>> Applied 1-3, 4 needs some reworking and can wait for v5.19, the first =
3
>> are fixes, so can go now.
>=20
> Now trying to fix this:
>=20
>  26     7.89 debian:9                      : FAIL gcc version 6.3.0 =
20170516 (Debian 6.3.0-18+deb9u1)
>    bench/numa.c: In function 'alloc_data':
>    bench/numa.c:359:6: error: 'orig_mask' may be used uninitialized in =
this function [-Werror=3Dmaybe-uninitialized]
>      ret =3D sched_setaffinity(0, size, mask);
>      ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    bench/numa.c:409:13: note: 'orig_mask' was declared here
>      cpu_set_t *orig_mask;
>                 ^~~~~~~~~
>    cc1: all warnings being treated as errors
>    /git/perf-5.18.0-rc1/tools/build/Makefile.build:139: recipe for =
target 'bench' failed
>    make[3]: *** [bench] Error 2
>=20
>=20
> Happened in several distros.

Hi Arnaldo

Thanks for pointing it. I could be able to recreate this compile error =
in Debian.
The reason for this issue is variable orig_mask which is used and =
initialised in =E2=80=9Calloc_data"
function within if condition for "init_cpu0=E2=80=9D. We can fix this =
issue by initialising it to NULL since
it is accessed conditionally. I also made some changes to CPU_FREE the =
mask in other error paths.
I will post a V3 with these changes.

Athira

>=20
> - Arnaldo