linux-kernel - Re: [PATCH 4/6] perf kmem: Print gfp flags in human readable string

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Message-ID: <20150511143536.GP28183@kernel.org>
Date:	Mon, 11 May 2015 11:35:36 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Joonsoo Kim <js1304@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	Pekka Enberg <penberg@...nel.org>, linux-mm@...ck.org
Subject: Re: [PATCH 4/6] perf kmem: Print gfp flags in human readable string

Em Tue, Apr 21, 2015 at 01:55:05PM +0900, Namhyung Kim escreveu:
> Save libtraceevent output and print it in the header.

<SNIP>

> +static int parse_gfp_flags(struct perf_evsel *evsel, struct perf_sample *sample,
> +			   unsigned int gfp_flags)
> +{
> +	struct pevent_record record = {
> +		.cpu = sample->cpu,
> +		.data = sample->raw_data,
> +		.size = sample->raw_size,
> +	};
> +	struct trace_seq seq;
> +	char *str, *pos;
> +
> +	if (nr_gfps) {
> +		struct gfp_flag key = {
> +			.flags = gfp_flags,
> +		};
> +
> +		if (bsearch(&key, gfps, nr_gfps, sizeof(*gfps), gfpcmp))
> +			return 0;
> +	}
> +
> +	trace_seq_init(&seq);
> +	pevent_event_info(&seq, evsel->tp_format, &record);
> +
> +	str = strtok_r(seq.buffer, " ", &pos);


This introduced a problem I only now noticed, possibly because my
compiler was upgraded:

[acme@zoo linux]$ git bisect good 
0e11115644b39ff9e986eb308b6c44ca75cd475f is the first bad commit
commit 0e11115644b39ff9e986eb308b6c44ca75cd475f
Author: Namhyung Kim <namhyung@...nel.org>
Date:   Tue Apr 21 13:55:05 2015 +0900

    perf kmem: Print gfp flags in human readable string
    
    Save libtraceevent output and print it in the header.

-------------------------------------------------


  GEN      /tmp/build/perf/common-cmds.h
  PERF_VERSION = 4.1.rc2.ga20d87
  CC       /tmp/build/perf/builtin-kmem.o
builtin-kmem.c: In function ‘perf_evsel__process_page_alloc_event’:
builtin-kmem.c:743:427: error: ‘pos’ may be used uninitialized in this
function [-Werror=maybe-uninitialized]
    new->human_readable = strdup(str + 10);
                                                                                                                                                                                                                                                                                                                                                                                                                                           ^
builtin-kmem.c:716:14: note: ‘pos’ was declared here
  char *str, *pos;
              ^
cc1: all warnings being treated as errors
/home/git/linux/tools/build/Makefile.build:68: recipe for target
'/tmp/build/perf/builtin-kmem.o' failed
make[2]: *** [/tmp/build/perf/builtin-kmem.o] Error 1
Makefile.perf:330: recipe for target '/tmp/build/perf/builtin-kmem.o'
failed
make[1]: *** [/tmp/build/perf/builtin-kmem.o] Error 2
Makefile:87: recipe for target 'builtin-kmem.o' failed
make: *** [builtin-kmem.o] Error 2
make: Leaving directory '/home/git/linux/tools/perf'

------

Trying to fix it by initializing it to NULL.

- Arnaldo
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