linux-kernel - Re: [RFC PATCH -v2 1/4] trace events: Interface to add files to debugfs

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Message-ID: <20120817072613.GA20591@aftab.osrc.amd.com>
Date:	Fri, 17 Aug 2012 09:26:13 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Borislav Petkov <borislav.petkov@....com>
Subject: Re: [RFC PATCH -v2 1/4] trace events: Interface to add files to
 debugfs

On Thu, Aug 16, 2012 at 06:06:48PM -0400, Steven Rostedt wrote:
> > /mnt/dbg/tracing/events/mce/mce_record/
> > |-- enable
> > |-- filter
> > |-- format
> > |-- id
> > `-- persistent
> 
> This looks rather hacky :-/

Ya think?! :-)

Well, this whole machinery is only for telling to userspace which is the
file descriptor of the persistent event. And yes, it could probably be
done with a lot less code.

Hell, I'm even fine with issuing it in dmesg and userspace parsing the
output - talk about efficient implementation.

> Can't this be added to the perf syscall, and have the user query the
> event instead?

Do you mean perf_ioctl? For that to work I need to have a file
descriptor of the "normal" event first and then query it to get the
persistent file descriptor... Or do you mean something easier?

> Note, this code will change drastically soon, and this change will
> break. I'll talk more about what will change at plumbers.

I'll try to get a video or something... :)

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
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