linux-kernel - Re: [PATCH 5/9] jump label: Add register_jump_label_key/unregister_jump_label

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Message-ID: <1287403521.29097.1554.camel@twins>
Date:	Mon, 18 Oct 2010 14:05:21 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jason Baron <jbaron@...hat.com>
Subject: Re: [PATCH 5/9] jump label: Add
 register_jump_label_key/unregister_jump_label_key

On Fri, 2010-10-15 at 23:13 +0200, Peter Zijlstra wrote:
> On Fri, 2010-10-15 at 17:09 -0400, Steven Rostedt wrote:
> > On Fri, 2010-10-15 at 23:03 +0200, Peter Zijlstra wrote:
> > 
> > > Urgh, this sucks.. :-(
> > > 
> > > So now we have to actually track all JUMP_LABEL() sites and call
> > > register muck on them.. even though we already track them through the
> > > special data section.
> > > 
> > > Is there really no way around this?
> > 
> > I'll take a look to see if we can monkey with magic and automate it.
> 
> So the problem is something like:
> 
> core kernel:
> 
>  jump_label_enable()
> 
> module:
> 
>  JUMP_LABEL()
> 
> And then because we don't have a proper __jump_table section, the
> jump_label_enable() won't properly work?
> 
> Why not let jump_label_enable() add a dummy entry with the enabled bit
> and once you load the module merge the real entry into it.

Or actually use the value of the key pointer.. it would mean either
standardizing the size (int/atomic_t would work), or using a version of
the fallback JUMP_LABEL implementation to sort out the type issues.
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