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Date:   Tue, 22 Oct 2019 10:01:00 +0200
From:   Jiri Olsa <jolsa@redhat.com>
To:     Andi Kleen <andi@firstfloor.org>
Cc:     acme@kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org,
        eranian@google.com, kan.liang@linux.intel.com,
        peterz@infradead.org, Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v2 1/9] perf evsel: Always preserve errno while cleaning
 up perf_event_open failures
Message-ID: <20191022080100.GA28177@krava>
References: <20191020175202.32456-1-andi@firstfloor.org>
 <20191020175202.32456-2-andi@firstfloor.org>
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On Sun, Oct 20, 2019 at 10:51:54AM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>=20
> In some cases when perf_event_open fails, it may do some closes to clean
> up. In special cases these closes can fail too, which overwrites the
> errno of the perf_event_open, which is then incorrectly reported.
>=20
> Save/restore errno around closes.
>=20
> Signed-off-by: Andi Kleen <ak@linux.intel.com>

Acked-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka

> ---
>  tools/perf/util/evsel.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>=20
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index abc7fda4a0fe..d831038b55f2 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1574,7 +1574,7 @@ int evsel__open(struct evsel *evsel, struct perf_cp=
u_map *cpus,
>  {
>  =09int cpu, thread, nthreads;
>  =09unsigned long flags =3D PERF_FLAG_FD_CLOEXEC;
> -=09int pid =3D -1, err;
> +=09int pid =3D -1, err, old_errno;
>  =09enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit =3D NO_CHANG=
E;
> =20
>  =09if ((perf_missing_features.write_backward && evsel->core.attr.write_b=
ackward) ||
> @@ -1727,8 +1727,8 @@ int evsel__open(struct evsel *evsel, struct perf_cp=
u_map *cpus,
>  =09 */
>  =09if (err =3D=3D -EMFILE && set_rlimit < INCREASED_MAX) {
>  =09=09struct rlimit l;
> -=09=09int old_errno =3D errno;
> =20
> +=09=09old_errno =3D errno;
>  =09=09if (getrlimit(RLIMIT_NOFILE, &l) =3D=3D 0) {
>  =09=09=09if (set_rlimit =3D=3D NO_CHANGE)
>  =09=09=09=09l.rlim_cur =3D l.rlim_max;
> @@ -1812,6 +1812,7 @@ int evsel__open(struct evsel *evsel, struct perf_cp=
u_map *cpus,
>  =09if (err)
>  =09=09threads->err_thread =3D thread;
> =20
> +=09old_errno =3D errno;
>  =09do {
>  =09=09while (--thread >=3D 0) {
>  =09=09=09close(FD(evsel, cpu, thread));
> @@ -1819,6 +1820,7 @@ int evsel__open(struct evsel *evsel, struct perf_cp=
u_map *cpus,
>  =09=09}
>  =09=09thread =3D nthreads;
>  =09} while (--cpu >=3D 0);
> +=09errno =3D old_errno;
>  =09return err;
>  }
> =20
> --=20
> 2.21.0
>=20