Re: [patch 2/8] mutex subsystem, add asm-generic/mutex-[dec|xchg].h implementations

[Posted January 3, 2006 by corbet]

From:		Linus Torvalds <torvalds-AT-osdl.org>
To:		Ingo Molnar <mingo-AT-elte.hu>
Subject:		Re: [patch 2/8] mutex subsystem, add asm-generic/mutex-[dec\|xchg].h implementations
Date:		Thu, 22 Dec 2005 15:56:32 -0800 (PST)
Cc:		lkml <linux-kernel-AT-vger.kernel.org>, Andrew Morton <akpm-AT-osdl.org>, Arjan van de Ven <arjanv-AT-infradead.org>, Nicolas Pitre <nico-AT-cam.org>, Jes Sorensen <jes-AT-trained-monkey.org>, Zwane Mwaikambo <zwane-AT-arm.linux.org.uk>, Oleg Nesterov <oleg-AT-tv-sign.ru>, David Howells <dhowells-AT-redhat.com>, Alan Cox <alan-AT-lxorguk.ukuu.org.uk>, Benjamin LaHaise <bcrl-AT-kvack.org>, Steven Rostedt <rostedt-AT-goodmis.org>, Christoph Hellwig <hch-AT-infradead.org>, Andi Kleen <ak-AT-suse.de>, Russell King <rmk+lkml-AT-arm.linux.org.uk>

On Fri, 23 Dec 2005, Ingo Molnar wrote:
>
> add the two generic mutex fastpath implementations.

Now this looks more like it. This is readable code without any #ifdef's in 
the middle.

Now the only #ifdef's seem to be for mutex debugging. Might it be 
worthwhile to have a generic debugging, that just uses spinlocks and just 
accept that it's going to be slow, but shared across absolutely all 
architectures?

Then you could have <linux/mutex.h> just doing a single

	#ifdef CONFIG_MUTEX_DEBUG
	# include <asm-generic/mutex-dbg.h>
	#else
	# include <asm/mutex.h>
	#endif

and have muted-dbg.h just contain prototypes (no point in inlining them, 
they're going to be big anyway) and then have a 

	obj$(CONFIG_MUTEX_DEBUG) += mutex-debug.c

in the kernel/ subdirectory? That way you could _really_ have a clean 
separation, with absolutely zero pollution of any architecture mess or 
debugging #ifdef's in any implementation code.

At that point I'd like to switch to mutexes just because the code is 
cleaner!

		Linus