linux-kernel - Re: [PATCH 1/3] perf daemon: Check err before calling setup_server_config in __cmd

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Date:   Mon, 24 Oct 2022 08:46:44 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...nel.org>, Yang Jihong <yangjihong1@...wei.com>
Cc:     peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
        adrian.hunter@...el.com, ak@...ux.intel.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] perf daemon: Check err before calling
 setup_server_config in __cmd_start

Em Sat, Oct 22, 2022 at 05:27:33PM +0800, Yang Jihong escreveu:
> If err!=0 before calling setup_server_config and reconfig==true,
> setup_server_config function may return 0 and err becomes 0.
> As a result, previous error is overwritten, need to check value of err first.
> 
> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
> ---
>  tools/perf/builtin-daemon.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-daemon.c b/tools/perf/builtin-daemon.c
> index 6cb3f6cc36d0..b82bd902602a 100644
> --- a/tools/perf/builtin-daemon.c
> +++ b/tools/perf/builtin-daemon.c
> @@ -1333,7 +1333,7 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
>  			if (fda.entries[signal_pos].revents & POLLIN)
>  				err = handle_signalfd(daemon) < 0;
>  
> -			if (reconfig)
> +			if (!err && reconfig)
>  				err = setup_server_config(daemon);
>  		}

Expanding the context a bit:

        while (!done && !err) {
                err = daemon__reconfig(daemon);

                if (!err && fdarray__poll(&fda, -1)) {
                        bool reconfig = false;

                        if (fda.entries[sock_pos].revents & POLLIN)
                                err = handle_server_socket(daemon, sock_fd);
                        if (fda.entries[file_pos].revents & POLLIN)
                                err = handle_config_changes(daemon, conf_fd, &reconfig);
                        if (fda.entries[signal_pos].revents & POLLIN)
                                err = handle_signalfd(daemon) < 0;

                        if (!err && reconfig)
                                err = setup_server_config(daemon);
                }
        }

The err you're checking may be the last one, that may have overwritten
'err' from handle_config_changes(), perhaps moving things around helps?
I.e.:
                if (!err && fdarray__poll(&fda, -1)) {
                        bool reconfig = false;

                        if (fda.entries[sock_pos].revents & POLLIN)
                                err = handle_server_socket(daemon, sock_fd);
                        if (fda.entries[signal_pos].revents & POLLIN)
                                err = handle_signalfd(daemon) < 0;
                        if (fda.entries[file_pos].revents & POLLIN)
                                err = handle_config_changes(daemon, conf_fd, &reconfig);

                        if (!err && reconfig)
                                err = setup_server_config(daemon);
                }


?

Jiri?

- Arnaldo

>  	}
> -- 
> 2.30.GIT

-- 

- Arnaldo