linux-kernel - Re: [PATCH v8 12/13] perf record: implement control commands handling

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Date:   Tue, 23 Jun 2020 16:54:34 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 12/13] perf record: implement control commands handling

On Wed, Jun 17, 2020 at 11:43:58AM +0300, Alexey Budankov wrote:
> 
> Implement handling of 'enable' and 'disable' control commands
> coming from control file descriptor.
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
> ---
>  tools/perf/builtin-record.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index d0b29a1070a0..0394e068dde8 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1527,6 +1527,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>  	bool disabled = false, draining = false;
>  	int fd;
>  	float ratio = 0;
> +	enum evlist_ctl_cmd cmd = EVLIST_CTL_CMD_UNSUPPORTED;
>  
>  	atexit(record__sig_exit);
>  	signal(SIGCHLD, sig_handler);
> @@ -1830,6 +1831,21 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>  				alarm(rec->switch_output.time);
>  		}
>  
> +		if (evlist__ctlfd_process(rec->evlist, &cmd) > 0) {
> +			switch (cmd) {
> +			case EVLIST_CTL_CMD_ENABLE:
> +				pr_info(EVLIST_ENABLED_MSG);
> +				break;
> +			case EVLIST_CTL_CMD_DISABLE:
> +				pr_info(EVLIST_DISABLED_MSG);
> +				break;
> +			case EVLIST_CTL_CMD_ACK:
> +			case EVLIST_CTL_CMD_UNSUPPORTED:
> +			default:
> +				break;
> +			}
> +		}

so there's still the filter call like:

                        if (evlist__filter_pollfd(rec->evlist, POLLERR | POLLHUP) == 0)
                                draining = true;

it will never be 0 if the control fds are stil alive no?

jirka