linux-kernel - Re: [PATCH v3 2/2] perf tool: Fix ppid for synthesized fork events

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Date:	Tue, 31 Mar 2015 16:10:26 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	David Ahern <dsahern@...il.com>
Cc:	acme@...nel.org, linux-kernel@...r.kernel.org,
	Don Zickus <dzickus@...hat.com>, Joe Mario <jmario@...hat.com>
Subject: Re: [PATCH v3 2/2] perf tool: Fix ppid for synthesized fork events

On Mon, Mar 30, 2015 at 02:35:58PM -0600, David Ahern wrote:
> 363b785f38 added synthesized fork events and set a thread's parent id
> to itself. Since we are already processing /proc/<pid>/status the ppid
> can be determined properly. Make it so.
> 
> Signed-off-by: David Ahern <dsahern@...il.com>
> Cc: Don Zickus <dzickus@...hat.com>
> Cc: Joe Mario <jmario@...hat.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> ---
> v3
> - removed isspace and newline checks; added brackets per Arnaldo's comments
> 
> v2:
> - removed changes to function signature for perf_event__synthesize_comm as
>   noted by Jiri
> 
>  tools/perf/util/event.c | 83 +++++++++++++++++++++++++++++--------------------
>  1 file changed, 50 insertions(+), 33 deletions(-)
> 
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index 023dd3548a94..5516236df6ab 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -51,29 +51,32 @@ static struct perf_sample synth_sample = {
>  
>  /*
>   * Assumes that the first 4095 bytes of /proc/pid/stat contains
> - * the comm and tgid.
> + * the comm, tgid and ppid.
>   */
> -static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len)
> +static int perf_event__get_comm_ids(pid_t pid, char *comm, size_t len,
> +				    pid_t *tgid, pid_t *ppid)
>  {
>  	char filename[PATH_MAX];
>  	char bf[4096];
>  	int fd;
>  	size_t size = 0, n;
> -	pid_t tgid = -1;
> -	char *nl, *name, *tgids;
> +	char *nl, *name, *tgids, *ppids;
> +
> +	*tgid = -1;
> +	*ppid = -1;
>  
>  	snprintf(filename, sizeof(filename), "/proc/%d/status", pid);
>  
>  	fd = open(filename, O_RDONLY);
>  	if (fd < 0) {
>  		pr_debug("couldn't open %s\n", filename);
> -		return 0;
> +		return -1;

hum, missed this one in previous version.. why did not we fail before?

jirka
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