linux-kernel - Re: [PATCH 4/6] perf_counter: Add PERF_COUNTER_IOC_SET

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Date:	Wed, 09 Sep 2009 23:45:57 -0500
From:	Tom Zanussi <tzanussi@...il.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jason Baron <jbaron@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] perf_counter: Add PERF_COUNTER_IOC_SET_FILTER ioctl

On Wed, 2009-09-09 at 10:18 +0800, Li Zefan wrote:
> >>>> Hrm,.. not at all sure about this.. what are the ABI implications?
> >>> I think the ABI should be fine if it's always a sub-set of C syntax. 
> >>> That would be C expressions initially. Hm?
> >> Right, so I've no clue what filter expressions look like, and the
> >> changelog doesn't help us at all. It doesn't mention its a well
> >> considered decision to henceforth freeze the expression syntax.
> >>
> >> Of course, since filters so far only work with tracepoint things, and
> >> since you can only come by tracepoint things through debugfs, and since
> >> anything debugfs is basically a free-for-all ABI-less world, we might be
> >> good, but then this is a very ill-defined ioctl() indeed.
> >>
> >> So please, consider this well -- there might not be a second chance.
> >>
> > 
> > I've been meaning to write up something about the event filters - here's
> > a first stab that hopefully helps explain them...
> > 
> 
> Great!
> 
> Reviewed-by: Li Zefan <lizf@...fujitsu.com>
> 
> Could you add your SOB and send it to Ingo?
> 
> Some nitpicks below:

Sure, I'll send a new version shortly - thanks for the suggestions.

Tom
 


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