linux-kernel - Re: [PATCHv2] tracing - support multiple pids in set_pid

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Message-ID: <4AB038A7.2070108@cn.fujitsu.com>
Date:	Wed, 16 Sep 2009 09:00:23 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	jolsa@...hat.com
CC:	mingo@...e.hu, rostedt@...dmis.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2] tracing - support multiple pids in set_pid_ftrace file

jolsa@...hat.com wrote:
> Adding the possibility to set more than 1 pid in the set_pid_ftrace file,
> thus allowing to trace more than 1 independent processes.
> 
> Usage:
> 
> sh-4.0# echo 284 > ./set_ftrace_pid 
> sh-4.0# cat ./set_ftrace_pid 
> 284
> sh-4.0# echo 1 >> ./set_ftrace_pid 
> sh-4.0# echo 0 >> ./set_ftrace_pid 
> sh-4.0# cat ./set_ftrace_pid 
> swapper tasks
> 1
> 284
> sh-4.0# echo 4 > ./set_ftrace_pid 
> sh-4.0# cat ./set_ftrace_pid 
> 4
> sh-4.0# echo > ./set_ftrace_pid 
> sh-4.0# cat ./set_ftrace_pid 
> no pid
> sh-4.0# 
> 
> 
> wbr,
> jirka
> 
> Signed-off-by: Jiri Olsa <jolsa@...hat.com>

Looks good.

Reviewed-by: Li Zefan <lizf@...fujitsu.com>

a few nitpicks.

>  /* set when tracing only a pid */

This comment should be removed too.

> -struct pid *ftrace_pid_trace;
>  static struct pid * const ftrace_swapper_pid = &init_struct_pid;
>  
...
> +static int ftrace_pid_add(int p)
> +{
> +	struct pid *pid;
> +	struct ftrace_pid *fpid;
> +	int ret = -EINVAL;
> +
> +	mutex_lock(&ftrace_lock);
> +
> +	if (!p)
> +		pid = ftrace_swapper_pid;
> +	else
> +		pid = find_get_pid(p);
> +
> +	if (!pid)
> +		goto out;
> +
> +	list_for_each_entry(fpid, &ftrace_pids, list)
> +		if (fpid->pid == pid)
> +			goto out_put;

rather than returning EINVAL, return EEXIST or just return 0?

> +
> +	ret = -ENOMEM;
--
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