linux-kernel - Re: [PATCH 0/3] jump label: updates for 2.6.37

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Message-ID: <20101124092123.GA4417@basil.fritz.box>
Date:	Wed, 24 Nov 2010 10:21:23 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Jason Baron <jbaron@...hat.com>, mingo@...e.hu,
	mathieu.desnoyers@...ymtl.ca, hpa@...or.com, tglx@...utronix.de,
	andi@...stfloor.org, roland@...hat.com, rth@...hat.com,
	masami.hiramatsu.pt@...achi.com, fweisbec@...il.com,
	avi@...hat.com, davem@...emloft.net, sam@...nborg.org,
	ddaney@...iumnetworks.com, michael@...erman.id.au,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] jump label: updates for 2.6.37

On Wed, Nov 24, 2010 at 09:29:22AM +0100, Peter Zijlstra wrote:
> On Tue, 2010-11-23 at 18:10 -0500, Steven Rostedt wrote:
> 
> > Anyway, I just tried what you explained with the current kernel, with
> > and without jump labels and, without jump labels, the module has its
> > kmalloc tracepoint traced, but with jump labels it does not. So we can
> > treat this as a regression, which is something that can go into an -rc.
> > 
> > The change log must state that this _is_ a regression, or Linus may not
> > accept it.
> 
> I really dislike the first patch... Preferably I'd simply fully revert
> all the jump-label stuff and try again next round with a saner
> interface.

Agreed.

> 
> There's a really good simple fix for this, simply disable the gcc
> trickery for .37 and use the fallback.
> 
> Then for .38, mandate the key type to be atomic_t * and switch to the
> SWITCH_POINT() interface from hpa.

This would also allow getting rid of the hash tables and use
binary search, which is imho much cleaner and simpler.

I will refresh my older patches to do that.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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