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Date: Wed, 25 Jun 2008 01:36:00 -0000
From: Masami Hiramatsu <mhiramat@redhat.com>
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To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Takashi Nishiie <t-nishiie@np.css.fujitsu.com>,         "'Alexey Dobriyan'" <adobriyan@gmail.com>,         "'Mathieu Desnoyers'" <mathieu.desnoyers@polymtl.ca>,         "'Peter Zijlstra'" <peterz@infradead.org>,         "'Steven Rostedt'" <rostedt@goodmis.org>,         "'Frank Ch. Eigler'" <fche@redhat.com>,         "'Ingo Molnar'" <mingo@elte.hu>,         "'LKML'" <linux-kernel@vger.kernel.org>,         "'systemtap-ml'" <systemtap@sources.redhat.com>,         "'Hideo AOKI'" <haoki@redhat.com>
Subject: Re: [RFC] Tracepoint proposal
References: <007601c8d5ca$18fa0e10$4aee2a30$@css.fujitsu.com> <48611B03.1000003@redhat.com> <20080625011951.D83E.KOSAKI.MOTOHIRO@jp.fujitsu.com>
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KOSAKI Motohiro wrote:
>> Tracepoint
>>  - stored in a section
>>  - dynamic activation
>>  - no message
>>  - export kernel structure
>>  - arguments depending on points
>>  - high frequently called
>>  - no module support (kernel use only)
> 
> Why Shouldn't kernel module use tracepoint?
> technical problem? or any plicy exist?

Good question, I think we don't want to export so much
kernel internal structures. Since tracepoint tend to export
raw kernel structure to user module, I thought it might be
better not to export its interface to modules.

However, I thought that again, and knew what Peter worried was
about marker which exports marker list to user space.
So, the issue is exporting internal structures to user space,
not to modules. Thus, I think it can support modules also.

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com