linux-kernel - Re: [PATCH v10 04/12] tracing: Add 'snapshot' event trigger command

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Message-ID: <525D099D.1010005@hitachi.com>
Date:	Tue, 15 Oct 2013 18:23:41 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc:	rostedt@...dmis.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 04/12] tracing: Add 'snapshot' event trigger command

(2013/10/11 23:04), Tom Zanussi wrote:
> On Fri, 2013-10-11 at 22:47 +0900, Masami Hiramatsu wrote:
>> (2013/10/11 9:48), Tom Zanussi wrote:
>>>  /**
>>> + * tracing_alloc_snapshot - allocate snapshot buffer.
>>> + *
>>> + * This only allocates the snapshot buffer if it isn't already
>>> + * allocated - it doesn't also take a snapshot.
>>> + *
>>> + * This is meant to be used in cases where the snapshot buffer needs
>>> + * to be set up for events that can't sleep but need to be able to
>>> + * trigger a snapshot.
>>> + */
>>> +int tracing_alloc_snapshot(void)
>>> +{
>>> +	struct trace_array *tr = &global_trace;
>>> +	int ret;
>>> +
>>> +	ret = alloc_snapshot(tr);
>>> +	WARN_ON(ret < 0);
>>> +
>>> +	return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(tracing_alloc_snapshot);
>>
>> Out of curiously, why this symbol is exported to modules?
>> The functions which are called directly from trace_event macros
>> should be exported because those macros can be used in module code,
>> but I couldn't find this in such code, at a glance.
>>
> 
> tracing_alloc_snapshot() goes along with tracing_snapshot() and
> tracing_snapshot_alloc() which are already exported - you should be able
> to take a snapshot from a module, or do a combined snapshot/alloc or
> (now) just the alloc.

Hmm, it seems that Steven added these EXPORT_SYMBOL_GPL at commit 1b22e382.
Steven, would you have any idea to call these functions from outside of
the ftrace?

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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