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Date:   Wed, 23 Oct 2019 12:42:45 +0200
From:   Jiri Olsa <jolsa@redhat.com>
To:     Igor Lubashev <ilubashe@akamai.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/3] perf kvm: Allow running without stdin
Message-ID: <20191023104245.GL22919@krava>
References: <1571795693-23558-1-git-send-email-ilubashe@akamai.com>
 <1571795693-23558-3-git-send-email-ilubashe@akamai.com>
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On Tue, Oct 22, 2019 at 09:54:52PM -0400, Igor Lubashev wrote:
> Allow perf kvm --stdio to run without access to stdin.
> This lets perf kvm to run in a batch mode until interrupted.
>=20
> The following now works as expected:
>=20
>   $ perf kvm top --stdio < /dev/null
>=20
> Signed-off-by: Igor Lubashev <ilubashe@akamai.com>
> ---
>  tools/perf/builtin-kvm.c | 33 ++++++++++++++++++++-------------
>  1 file changed, 20 insertions(+), 13 deletions(-)
>=20
> diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
> index 858da896b518..5217aa3596c7 100644
> --- a/tools/perf/builtin-kvm.c
> +++ b/tools/perf/builtin-kvm.c
> @@ -930,18 +930,20 @@ static int fd_set_nonblock(int fd)
> =20
>  static int perf_kvm__handle_stdin(void)
>  {
> -=09int c;
> -
> -=09c =3D getc(stdin);
> -=09if (c =3D=3D 'q')
> +=09switch (getc(stdin)) {
> +=09case 'q':
> +=09=09done =3D 1;
>  =09=09return 1;
> -
> -=09return 0;
> +=09case EOF:
> +=09=09return 0;
> +=09default:
> +=09=09return 1;
> +=09}
>  }
> =20
>  static int kvm_events_live_report(struct perf_kvm_stat *kvm)
>  {
> -=09int nr_stdin, ret, err =3D -EINVAL;
> +=09int nr_stdin =3D -1, ret, err =3D -EINVAL;
>  =09struct termios save;
> =20
>  =09/* live flag must be set first */
> @@ -972,13 +974,16 @@ static int kvm_events_live_report(struct perf_kvm_s=
tat *kvm)
>  =09if (evlist__add_pollfd(kvm->evlist, kvm->timerfd) < 0)
>  =09=09goto out;
> =20
> -=09nr_stdin =3D evlist__add_pollfd(kvm->evlist, fileno(stdin));
> -=09if (nr_stdin < 0)
> -=09=09goto out;
> -
>  =09if (fd_set_nonblock(fileno(stdin)) !=3D 0)
>  =09=09goto out;
> =20
> +=09/* add stdin, if it is connected */
> +=09if (getc(stdin) !=3D EOF) {
> +=09=09nr_stdin =3D evlist__add_pollfd(kvm->evlist, fileno(stdin));
> +=09=09if (nr_stdin < 0)
> +=09=09=09goto out;
> +=09}
> +
>  =09/* everything is good - enable the events and process */
>  =09evlist__enable(kvm->evlist);
> =20
> @@ -994,8 +999,10 @@ static int kvm_events_live_report(struct perf_kvm_st=
at *kvm)
>  =09=09if (err)
>  =09=09=09goto out;
> =20
> -=09=09if (fda->entries[nr_stdin].revents & POLLIN)
> -=09=09=09done =3D perf_kvm__handle_stdin();
> +=09=09if (nr_stdin >=3D 0 && fda->entries[nr_stdin].revents & POLLIN) {
> +=09=09=09if (!perf_kvm__handle_stdin())

can this return 0 ? if stdin is EOF then nr_stdin stays -1

> +=09=09=09=09fda->entries[nr_stdin].events =3D 0;

why do you need to set events to 0 in here?

thanks,
jirka