linux-kernel - Re: [PATCH 2/4] perf tools: Introduce cpu_map__snprint

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Message-ID: <20170224210853.GB15145@kernel.org>
Date:   Fri, 24 Feb 2017 18:08:53 -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@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@....com,
        Steven Rostedt <rostedt@...dmis.org>,
        Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 2/4] perf tools: Introduce cpu_map__snprint_mask()

Em Fri, Feb 24, 2017 at 10:12:49AM +0900, Namhyung Kim escreveu:
> The cpu_map__snprint_mask() is to generate string representation of
> cpumask bitmap.  For cpu 0 to 11, it'll return "fff".
> 
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/util/cpumap.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  tools/perf/util/cpumap.h |  1 +
>  2 files changed, 47 insertions(+)
> 
> diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
> index 8c7504939113..08540ab2a891 100644
> --- a/tools/perf/util/cpumap.c
> +++ b/tools/perf/util/cpumap.c
> @@ -673,3 +673,49 @@ size_t cpu_map__snprint(struct cpu_map *map, char *buf, size_t size)
>  	pr_debug("cpumask list: %s\n", buf);
>  	return ret;
>  }
> +
> +static char hex_char(char val)

Why do you use 'char' above and...

> +{
> +	if (0 <= val && val <= 9)
> +		return val + '0';
> +	if (10 <= val && val < 16)
> +		return val - 10 + 'a';
> +	return '?';
> +}
> +size_t cpu_map__snprint_mask(struct cpu_map *map, char *buf, size_t size)
<SNIP>
> +	for (cpu = last_cpu / 4 * 4; cpu >= 0; cpu -= 4) {
> +		unsigned char bits = bitmap[cpu / 8];

'unsigned char' here?

Some compilers don't like it, for instance:

  19 fedora:24-x-ARC-uClibc: FAIL

  CC       /tmp/build/perf/util/cpumap.o
util/cpumap.c: In function 'hex_char':
util/cpumap.c:679:2: error: comparison is always true due to limited range of data type [-Werror=type-limits]
  if (0 <= val && val <= 9)
  ^
cc1: all warnings being treated as errors

And:

  10 debian:experimental-x-arm64: FAIL

  CC       /tmp/build/perf/util/cpumap.o
util/cpumap.c: In function 'hex_char':
util/cpumap.c:679:8: error: comparison is always true due to limited range of data type [-Werror=type-limits]
  if (0 <= val && val <= 9)
        ^~

Are you ok with the patch below?

diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index 6ab8699f0233..405f56ad5c24 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -687,7 +687,7 @@ size_t cpu_map__snprint_mask(struct cpu_map *map, char *buf, size_t size)
 {
 	int i, cpu;
 	char *ptr = buf;
-	unsigned char *bitmap;
+	char *bitmap;
 	int last_cpu = cpu_map__cpu(map, map->nr - 1);
 
 	bitmap = zalloc((last_cpu + 7) / 8);
@@ -702,7 +702,7 @@ size_t cpu_map__snprint_mask(struct cpu_map *map, char *buf, size_t size)
 	}
 
 	for (cpu = last_cpu / 4 * 4; cpu >= 0; cpu -= 4) {
-		unsigned char bits = bitmap[cpu / 8];
+		char bits = bitmap[cpu / 8];
 
 		if (cpu % 8)
 			bits >>= 4;


> +		if (cpu % 8)
> +			bits >>= 4;
> +		else
> +			bits &= 0xf;
> +
> +		*ptr++ = hex_char(bits);
> +		if ((cpu % 32) == 0 && cpu > 0)
> +			*ptr++ = ',';
> +	}
> +	*ptr = '\0';
> +	free(bitmap);
> +
> +	buf[size - 1] = '\0';
> +	return ptr - buf;
> +}
> diff --git a/tools/perf/util/cpumap.h b/tools/perf/util/cpumap.h
> index 1a0549af8f5c..4d231c6eac0c 100644
> --- a/tools/perf/util/cpumap.h
> +++ b/tools/perf/util/cpumap.h
> @@ -20,6 +20,7 @@ struct cpu_map *cpu_map__dummy_new(void);
>  struct cpu_map *cpu_map__new_data(struct cpu_map_data *data);
>  struct cpu_map *cpu_map__read(FILE *file);
>  size_t cpu_map__snprint(struct cpu_map *map, char *buf, size_t size);
> +size_t cpu_map__snprint_mask(struct cpu_map *map, char *buf, size_t size);
>  size_t cpu_map__fprintf(struct cpu_map *map, FILE *fp);
>  int cpu_map__get_socket_id(int cpu);
>  int cpu_map__get_socket(struct cpu_map *map, int idx, void *data);
> -- 
> 2.11.1