linux-kernel - Re: [PATCH -tip 1/3] [CLEANUP] perf-probe: Expand given path to absolute path

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Date:	Mon, 23 Dec 2013 11:28:32 -0300
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>,
	lkml <linux-kernel@...r.kernel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"David A. Long" <dave.long@...aro.org>, systemtap@...rceware.org,
	yrl.pp-manager.tt@...achi.com, Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH -tip 1/3] [CLEANUP] perf-probe: Expand given path to
 absolute path

Em Mon, Dec 23, 2013 at 06:35:09AM +0900, Masami Hiramatsu escreveu:
> (2013/12/21 3:00), Arnaldo Carvalho de Melo wrote:
> > Em Fri, Dec 20, 2013 at 10:02:57AM +0000, Masami Hiramatsu escreveu:
> >> Expand given path to absolute path in option parser,
> >> except for a module name. Instead of expanding it later,
> >> this get the absolute path in early stage.
> > 
> > What is the problem this solves?
> > 
> > Can you provide some output showing the problem, i.e. before you apply
> > this patch?
> 
> No, this is just a code cleanup, for the later enhancements.

Ok, this is just a cleanup, but what does this cleanup achieves? Why is
it better to "getting the absolute path in early stage"?

I.e. you're describing what the patch does, and I can see it from
reading code, but why is it good to do it in an early stage?

> Should I put it into the next patch?

No need for that, just, please, clarify why it is needed.
 
> Thank you,
> 
> > 
> > Then can you provide the output after the patch is applied?
> > 
> > - Arnaldo
> >  
> >> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> >> ---
> >>  tools/perf/builtin-probe.c    |    9 +++++++++
> >>  tools/perf/util/probe-event.c |   11 ++---------
> >>  2 files changed, 11 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
> >> index 6ea9e85..b40d064 100644
> >> --- a/tools/perf/builtin-probe.c
> >> +++ b/tools/perf/builtin-probe.c
> >> @@ -180,6 +180,15 @@ static int opt_set_target(const struct option *opt, const char *str,
> >>  		else
> >>  			return ret;
> >>  
> >> +		/* Expand given path to absolute path, except for modulename */
> >> +		if (params.uprobes || strchr(str, '/')) {
> >> +			str = realpath(str, NULL);
> >> +			if (!str) {
> >> +				pr_warning("Failed to find the path of %s.\n",
> >> +					   str);
> >> +				return ret;
> >> +			}
> >> +		}
> >>  		params.target = str;
> >>  		ret = 0;
> >>  	}
> >> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> >> index d7cff57..05be5de 100644
> >> --- a/tools/perf/util/probe-event.c
> >> +++ b/tools/perf/util/probe-event.c
> >> @@ -2281,7 +2281,7 @@ static int convert_name_to_addr(struct perf_probe_event *pev, const char *exec)
> >>  	struct perf_probe_point *pp = &pev->point;
> >>  	struct symbol *sym;
> >>  	struct map *map = NULL;
> >> -	char *function = NULL, *name = NULL;
> >> +	char *function = NULL;
> >>  	int ret = -EINVAL;
> >>  	unsigned long long vaddr = 0;
> >>  
> >> @@ -2297,12 +2297,7 @@ static int convert_name_to_addr(struct perf_probe_event *pev, const char *exec)
> >>  		goto out;
> >>  	}
> >>  
> >> -	name = realpath(exec, NULL);
> >> -	if (!name) {
> >> -		pr_warning("Cannot find realpath for %s.\n", exec);
> >> -		goto out;
> >> -	}
> >> -	map = dso__new_map(name);
> >> +	map = dso__new_map(exec);
> >>  	if (!map) {
> >>  		pr_warning("Cannot find appropriate DSO for %s.\n", exec);
> >>  		goto out;
> >> @@ -2367,7 +2362,5 @@ out:
> >>  	}
> >>  	if (function)
> >>  		free(function);
> >> -	if (name)
> >> -		free(name);
> >>  	return ret;
> >>  }
> >>
> > 
> 
> 
> -- 
> Masami HIRAMATSU
> IT Management Research Dept. Linux Technology Center
> Hitachi, Ltd., Yokohama Research Laboratory
> E-mail: masami.hiramatsu.pt@...achi.com
> 
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