linux-kernel - Re: [PATCH 1/2 v3] tracing/uprobes: Support ftrace_event

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Message-ID: <20130625202405.GA16143@redhat.com>
Date:	Tue, 25 Jun 2013 22:24:05 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2 v3] tracing/uprobes: Support ftrace_event_file base
	multibuffer

Sorry again, didn't have time to review, will try tomorrow.

Looks good but a couple of minor nits, and perhaps we should
fix the bugs with unregister_trace_uprobe first... in kprobes
too _if_ I am right. I'll return tomorrow.

On 06/25, zhangwei(Jovi) wrote:
>
> -probe_event_enable(struct trace_uprobe *tu, int flag, filter_func_t filter)
> +probe_event_enable(struct trace_uprobe *tu, struct ftrace_event_file *file,
> +		   filter_func_t filter)
>  {
> +	int enabled = 0;
>  	int ret = 0;
> 
> +	/* we cannot call uprobe_register twice for same tu */
>  	if (is_trace_uprobe_enabled(tu))
> -		return -EINTR;
> +		enabled = 1;

Cosmetic again, "int enabled = 0" and then "if (is_trace_uprobe_enabled)"
looks a bit strange,

	enabled = is_trace_uprobe_enabled();

looks a bit more clean.

> +	if (file) {
> +		struct event_file_link *link;
> +
> +		if (tu->flags & TP_FLAG_PROFILE)
> +			return -EINTR;
> +
> +		link = kmalloc(sizeof(*link), GFP_KERNEL);
> +		if (!link)
> +			return -ENOMEM;
> +
> +		link->file = file;
> +		list_add_rcu(&link->list, &tu->files);

I agree with Masami, list_add_rcu_tail() looks better even if this
doesn't really matter.

Oleg.

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