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Date: Mon, 30 Mar 2015 10:01:32 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: David Ahern <dsahern@gmail.com>
Cc: acme@kernel.org, linux-kernel@vger.kernel.org,
        Don Zickus <dzickus@redhat.com>, Joe Mario <jmario@redhat.com>
Subject: Re: [PATCH 1/2] perf tool: Refactor comm/tgid lookup
Message-ID: <20150330080132.GA8679@krava.brq.redhat.com>
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On Sun, Mar 29, 2015 at 04:30:01PM -0600, David Ahern wrote:

SNIP

> +	fd = open(filename, O_RDONLY);
> +	if (fd < 0) {
>  		pr_debug("couldn't open %s\n", filename);
>  		return 0;
>  	}
>  
> -	while (!comm[0] || (tgid < 0)) {
> -		if (fgets(bf, sizeof(bf), fp) == NULL) {
> -			pr_warning("couldn't get COMM and pgid, malformed %s\n",
> -				   filename);
> -			break;
> -		}
> -
> -		if (memcmp(bf, "Name:", 5) == 0) {
> -			char *name = bf + 5;
> -			while (*name && isspace(*name))
> -				++name;
> -			size = strlen(name) - 1;
> -			if (size >= len)
> -				size = len - 1;
> -			memcpy(comm, name, size);
> -			comm[size] = '\0';
> -
> -		} else if (memcmp(bf, "Tgid:", 5) == 0) {
> -			char *tgids = bf + 5;
> -			while (*tgids && isspace(*tgids))
> -				++tgids;
> -			tgid = atoi(tgids);
> -		}
> +	n = read(fd, bf, sizeof(bf) - 1);
> +	close(fd);

we have filename__read_str, which will read whole file into buffer,
and you dont need to worry about the file size.. not that there's
any worry wrt /proc/<pid>/status file, but who knows.. ;-)

jirka