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SubjectRe: [PATCH 2/3] perf kvm: Allow running without stdin
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.
>
> The following now works as expected:
>
> $ perf kvm top --stdio < /dev/null
>
> Signed-off-by: Igor Lubashev <ilubashe@akamai.com>
> ---
> tools/perf/builtin-kvm.c | 33 ++++++++++++++++++++-------------
> 1 file changed, 20 insertions(+), 13 deletions(-)
>
> 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)
>
> static int perf_kvm__handle_stdin(void)
> {
> - int c;
> -
> - c = getc(stdin);
> - if (c == 'q')
> + switch (getc(stdin)) {
> + case 'q':
> + done = 1;
> return 1;
> -
> - return 0;
> + case EOF:
> + return 0;
> + default:
> + return 1;
> + }
> }
>
> static int kvm_events_live_report(struct perf_kvm_stat *kvm)
> {
> - int nr_stdin, ret, err = -EINVAL;
> + int nr_stdin = -1, ret, err = -EINVAL;
> struct termios save;
>
> /* live flag must be set first */
> @@ -972,13 +974,16 @@ static int kvm_events_live_report(struct perf_kvm_stat *kvm)
> if (evlist__add_pollfd(kvm->evlist, kvm->timerfd) < 0)
> goto out;
>
> - nr_stdin = evlist__add_pollfd(kvm->evlist, fileno(stdin));
> - if (nr_stdin < 0)
> - goto out;
> -
> if (fd_set_nonblock(fileno(stdin)) != 0)
> goto out;
>
> + /* add stdin, if it is connected */
> + if (getc(stdin) != EOF) {
> + nr_stdin = evlist__add_pollfd(kvm->evlist, fileno(stdin));
> + if (nr_stdin < 0)
> + goto out;
> + }
> +
> /* everything is good - enable the events and process */
> evlist__enable(kvm->evlist);
>
> @@ -994,8 +999,10 @@ static int kvm_events_live_report(struct perf_kvm_stat *kvm)
> if (err)
> goto out;
>
> - if (fda->entries[nr_stdin].revents & POLLIN)
> - done = perf_kvm__handle_stdin();
> + if (nr_stdin >= 0 && fda->entries[nr_stdin].revents & POLLIN) {
> + if (!perf_kvm__handle_stdin())

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

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

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

thanks,
jirka

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