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

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Date:	Fri, 28 Jun 2013 13:17:33 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.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

(2013/06/28 1:27), Oleg Nesterov wrote:
> On 06/27, Srikar Dronamraju wrote:
>>
>> * zhangwei(Jovi) <jovi.zhangwei@...wei.com> [2013-06-25 11:30:20]:
>>> +	if (!enabled) {
>>> +		tu->consumer.filter = filter;
>>> +		ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
>>> +		if (ret)
>>> +			tu->flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;
>>
>> Dont we need to free link here? or where does the link that got
>> allocated freed?
> 
> Agreed...
> 
> Masami, it seems that (just in case, with or without "Turn trace_probe->files
> into list_head" I sent) trace_kpobes needs the similar fix too? Plus it should
> clear TP_FLAG_* if enable_k.*probe() fails.

Oops, right! this problem also happens on the latest kernel. I must fix that
before introducing list_head...

> Or enable_trace_probe() assumes that enable_kprobe() must succeed? In this
> case probably WARN_ON(ret) makes sense.

In the case of probing a module function, the event can be gone when the
module is unloaded. At that time, enable_trace_probe must fails.

BTW, Steven, could you control the traffic of recent tracing works? :)
There are several works on the ftrace we made, but each of them
sometimes conflicting. We'd better make a merge plan or a working
branch on your tracing tree which allows us to work together on it.

Thank you!

-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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