linux-kernel - Re: [PATCH 00/10] jump label: introduce very

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Message-ID: <1329923583.24994.21.camel@twins>
Date:	Wed, 22 Feb 2012 16:13:03 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Jason Baron <jbaron@...hat.com>,
	mathieu.desnoyers@...icios.com, davem@...emloft.net,
	ddaney.cavm@...il.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	rth <rth@...hat.com>
Subject: Re: [PATCH 00/10] jump label: introduce very_[un]likely + cleanups
 + docs

On Wed, 2012-02-22 at 08:54 -0500, Steven Rostedt wrote:
> But we could push a "unlikely(static_branch())" for
> such a case (or keep it as very_unlikely()). 

If only that would work.. GCC assumes a bunch of things when you use
'asm goto'. An unbiased 'asm goto' that would take likely() and
unlikely() hints would be ideal, but alas that's not how the thing got
implemented.

Now arguable we could maybe just stick with the static_branch() thing
and decide that GCC is broken for adding bias and not respecting
likely() and unlikely(), but the GCC folks might have an opinion there.

Anyway, if we have to stick with the current implementation then an
unbiased version is impossible to implement.

If we get GCC folks on board to change stuff, who knows.
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