linux-kernel - Re: [patch 2/9] Conditional Calls

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Message-ID: <20070601170739.GA11115@waste.org>
Date:	Fri, 1 Jun 2007 12:07:40 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 2/9] Conditional Calls - Hash Table

On Fri, Jun 01, 2007 at 12:46:23PM -0400, Mathieu Desnoyers wrote:
> * Matt Mackall (mpm@...enic.com) wrote:
> > On Thu, May 31, 2007 at 03:42:50PM +0200, Andi Kleen wrote:
> > > Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> writes:
> > > 
> > > > Reimplementation of the cond calls which uses a hash table to hold the active
> > > > cond_calls. It permits to first arm a cond_call and then load supplementary
> > > > modules that contain this cond_call.
> > > 
> > > Hash table is probably overkill. This is a very very slow path operation.
> > > Can you simplify the code? Just a linked list of all the condcall segments
> > > should be enough  and then walk it.
> > 
> > I think it could be greatly simplified by using symbols instead of
> > strings.
> > 
> > That is, doing cond_call(foo, func()) rather than cond_call("foo",
> > func()). Here foo is a structure or type holding the relevant info to
> > deal with the cond_call infrastructure. For unoptimized architectures,
> > it can simply be a bool, which will be faster.
> > 
> > This has the added advantage that the compiler will automatically pick
> > up any misspellings of these things. And it saves the space we'd use
> > on the hash table too.
> > 
> 
> The idea is interesting, but does not fit the problem: AFAIK, it will
> not be possible to do multiple declarations of the same symbol, which is
> needed whenever we want to declare a cond_call() more than once or to
> embed it in an inline function.

It's not clear to me why either of those things are necessary. An
example please?

-- 
Mathematics is the supreme nostalgia of our time.
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