linux-kernel - Re: [PATCH 01/12] perf tools: Separate generic code in dso__data_file

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Date:   Mon, 13 May 2019 16:47:54 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Stanislav Fomichev <sdf@...ichev.me>,
        Song Liu <songliubraving@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 01/12] perf tools: Separate generic code in
 dso__data_file_size

Em Wed, May 08, 2019 at 03:19:59PM +0200, Jiri Olsa escreveu:
> Moving file specific code in dso__data_file_size function
> into separate file_size function. I'll add bpf specific
> code in following patches.

I'm applying this patch, as it just moves things around, no logic
change, but can you please clarify a question I have after looking at
this patch?
 
> Link: http://lkml.kernel.org/n/tip-rkcsft4a0f8sw33p67llxf0d@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  tools/perf/util/dso.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index e059976d9d93..cb6199c1390a 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -898,18 +898,12 @@ static ssize_t cached_read(struct dso *dso, struct machine *machine,
>  	return r;
>  }
>  
> -int dso__data_file_size(struct dso *dso, struct machine *machine)
> +static int file_size(struct dso *dso, struct machine *machine)
>  {
>  	int ret = 0;
>  	struct stat st;
>  	char sbuf[STRERR_BUFSIZE];
>  
> -	if (dso->data.file_size)
> -		return 0;
> -
> -	if (dso->data.status == DSO_DATA_STATUS_ERROR)
> -		return -1;
> -
>  	pthread_mutex_lock(&dso__data_open_lock);
>  
>  	/*
> @@ -938,6 +932,17 @@ int dso__data_file_size(struct dso *dso, struct machine *machine)
>  	return ret;
>  }
>  
> +int dso__data_file_size(struct dso *dso, struct machine *machine)
> +{
> +	if (dso->data.file_size)
> +		return 0;
> +
> +	if (dso->data.status == DSO_DATA_STATUS_ERROR)
> +		return -1;
> +
> +	return file_size(dso, machine);
> +}


So the name of the function suggests we want to know the
"data_file_size" of a dso, then the logic in it returns _zero_ if a
member named "dso->data.file_size" is _not_ zero, can you please
clarify?

I was expecting something like:

	if (dso->data.file_size)
		return dso->data.file_size;

I.e. if we had already read it, return the cached value, otherwise go
and call some other function to get that info somehow.

- Arnaldo

> +
>  /**
>   * dso__data_size - Return dso data size
>   * @dso: dso object
> -- 
> 2.20.1

-- 

- Arnaldo