linux-kernel - Re: [RFC] gcc feature request: Moving blocks into sections

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Date:	Mon, 05 Aug 2013 10:02:24 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	LKML <linux-kernel@...r.kernel.org>, gcc <gcc@....gnu.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Daney <ddaney.cavm@...il.com>,
	Behan Webster <behanw@...verseincode.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC] gcc feature request: Moving blocks into sections

On 08/05/2013 09:55 AM, Steven Rostedt wrote:
> 
> Almost a full year ago, Mathieu suggested something like:
> 
> if (unlikely(x)) __attribute__((section(".unlikely"))) {
>         ...
> } else __attribute__((section(".likely"))) {
>         ...
> }
> 
> https://lkml.org/lkml/2012/8/9/658
> 
> Which got me thinking. How hard would it be to set a block in its own
> section. Like what Mathieu suggested, but it doesn't have to be
> ".unlikely".
> 
> if (x) __attibute__((section(".foo"))) {
> 	/* do something */
> }
> 

One concern I have is how this kind of code would work when embedded
inside a function which already has a section attribute.  This could
easily cause really weird bugs when someone "optimizes" an inline or
macro and breaks a single call site...

	-hpa


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