linux-kernel - Re: [PATCH ftrace/core V5] ftrace: Introduce saved_cmdlines

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Date:	Mon, 09 Jun 2014 17:21:12 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>
Cc:	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Ingo Molnar <mingo@...hat.com>, yrl.pp-manager.tt@...achi.com
Subject: Re: [PATCH ftrace/core V5] ftrace: Introduce saved_cmdlines_size file

Hi Yoshihiro,

Sorry for being late, but just wanna give you some (minor) feedbacks..


On Thu, 05 Jun 2014 10:24:27 +0900, Yoshihiro YUNOMAE wrote:
> +static int trace_create_savedcmd(void)
> +{
> +	int ret;
> +
> +	savedcmd = kmalloc(sizeof(struct saved_cmdlines_buffer), GFP_KERNEL);

s/sizeof(struct saved_cmdlines_buffer)/sizeof(*savedcmd)/


> +	if (!savedcmd)
> +		return -ENOMEM;
> +
> +	ret = allocate_cmdlines_buffer(SAVED_CMDLINES_DEFAULT, savedcmd);
> +	if (ret < 0) {
> +		kfree(savedcmd);
> +		savedcmd = NULL;
> +		return -ENOMEM;
> +	}
> +
> +	return 0;
>  }

[SNIP]
>  static ssize_t
> +tracing_saved_cmdlines_size_read(struct file *filp, char __user *ubuf,
> +				 size_t cnt, loff_t *ppos)
> +{
> +	char buf[64];
> +	int r;
> +
> +	arch_spin_lock(&trace_cmdline_lock);
> +	r = sprintf(buf, "%u\n", savedcmd->cmdline_num);

In general, it's better to use scnprintf() instead.


> +	arch_spin_unlock(&trace_cmdline_lock);
> +
> +	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
> +}
> +
> +static void free_saved_cmdlines_buffer(struct saved_cmdlines_buffer *s)
> +{
> +	kfree(s->saved_cmdlines);
> +	kfree(s->map_cmdline_to_pid);
> +	kfree(s);
> +}
> +
> +static int tracing_resize_saved_cmdlines(unsigned int val)
> +{
> +	struct saved_cmdlines_buffer *s, *savedcmd_temp;
> +
> +	s = kmalloc(sizeof(struct saved_cmdlines_buffer), GFP_KERNEL);

s/sizeof(struct saved_cmdlines_buffer)/sizeof(*s)/

Thanks,
Namhyung


> +	if (!s)
> +		return -ENOMEM;
> +
> +	if (allocate_cmdlines_buffer(val, s) < 0) {
> +		kfree(s);
> +		return -ENOMEM;
> +	}
> +
> +	arch_spin_lock(&trace_cmdline_lock);
> +	savedcmd_temp = savedcmd;
> +	savedcmd = s;
> +	arch_spin_unlock(&trace_cmdline_lock);
> +	free_saved_cmdlines_buffer(savedcmd_temp);
> +
> +	return 0;
> +}
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