linux-kernel - Re: [RFC,PATCH 14/14] utrace core

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Message-ID: <20091124214450.GA12828@redhat.com>
Date:	Tue, 24 Nov 2009 22:44:50 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Alexey Dobriyan <adobriyan@...il.com>,
	Ananth Mavinakayanahalli <ananth@...ibm.com>,
	"Frank Ch. Eigler" <fche@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org, utrace-devel@...hat.com
Subject: Re: [RFC,PATCH 14/14] utrace core

(restore cc's)

On 11/24, Andi Kleen wrote:
>
> On Tue, Nov 24, 2009 at 09:41:52PM +0100, Oleg Nesterov wrote:
> > On 11/24, Andi Kleen wrote:
> > >
> > > Oleg Nesterov <oleg@...hat.com> writes:
> > >
> > > > From: Roland McGrath <roland@...hat.com>
> > > >
> > > > This adds the utrace facility, a new modular interface in the kernel
> > > > for implementing user thread tracing and debugging.  This fits on top
> > > > of the tracehook_* layer, so the new code is well-isolated.
> > >
> > > Could we just drop the tracehook layer if this finally merged
> > > and call the low level functions directly?
> >
> > Not sure I understand. Tracehooks are trivial inline wrappers on
> > top utrace calls,
>
> Yes that's the problem -- they are unnecessary obfuscation
> when you can just call directly.

This is subjective, but personally I disagree. Contrary, imho it
is good that tracehook hides the (simple) details. I do not understand
why the reader of, say, do_fork() should see the contents of
tracehook_report_clone_complete(). This will complicate the understanding.
Those people who want to understand/change fork() do not care about
utrace/ptrace usually.

And please note that it is much, much easier to change this code
when it lives in tracehooks.h instead of sched.c/signal.c/etc.

> > What is the point?
>
> Less code obfuscation.
>
> When it's a utrace call, call it a utrace call, not something else.

Why do you think this is obfuscation? Well, we can rename these
helpers, s/tracehook_/utrace_/, but I don't see how this can make
the code more readable.

Oleg.

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