Message-ID: <1338486029.28384.93.camel@twins>
Subject: Re: [PATCH 1/5] ftrace: Synchronize variable setting with
 breakpoints
From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Andrew Morton <akpm@linux-foundation.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Dave Jones <davej@redhat.com>,
        Andi Kleen <ak@linux.intel.com>
Date: Thu, 31 May 2012 19:40:29 +0200
In-Reply-To: <1338473302.13348.336.camel@gandalf.stny.rr.com>
References: <20120531012829.160060586@goodmis.org>
	 <20120531020440.476352979@goodmis.org> <1338462398.28384.52.camel@twins>
	 <1338473302.13348.336.camel@gandalf.stny.rr.com>
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On Thu, 2012-05-31 at 10:08 -0400, Steven Rostedt wrote:
> > Also, why does this stuff live in ftrace? I always thought you were
> > going to replace text_poke() so everybody that uses cross-modifying code
> > could profit?
> 
> I discussed this with Masami at Collaboration Summit. The two are
> similar but also very different. But we want to start merging the two
> together where it makes sense. 

Argh,. I so disagree. You're doing it backwards.

First you merge whatever is there, regardless of who came first.

Then, when everybody doing text modification is using the same
interface, do a second implementation using a Kconfig knob. If the scary
new one breaks, no sweat, flip the config. If its proven stable, kill
off the old one.

I really don't see why ftrace would be special here.. if you have all
text_poke() users use the magic new way you'll have more coverage and
better chances of hitting any snags if there are any.


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