linux-kernel - Re: [PATCH 02/29] x86, tsx: Add RTM intrinsics

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Message-ID: <15400.1364201661@ale.ozlabs.ibm.com>
Date:	Mon, 25 Mar 2013 19:54:21 +1100
From:	Michael Neuling <mikey@...ling.org>
To:	Andi Kleen <ak@...ux.intel.com>
cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	x86@...nel.org
Subject: Re: [PATCH 02/29] x86, tsx: Add RTM intrinsics

Andi Kleen <ak@...ux.intel.com> wrote:

> > FYI the TM spec can be downloaded here:
> >   https://www.power.org/documentation/power-isa-transactional-memory/
> > 
> > You're example code looks like this:
> 
> I don't think portable code will use this directly. Note it's in arch/x86/
> 
> Generally portable code should use higher level interfaces, like
> elide_lock/elide_lock_adapt that hide the architecture specific 
> details.
> 
> If you want to do lock elision you would plug in some elision
> algorithm that works well at that level.
> 
> > Secondly, can we make xbegin just return true/false and get the status
> > later if needed?
> 
> I now removed xbegin() from the portable file, as it's only used
> in arch specific code. 

OK, well most of my objections go away now.

> And FWIW I'm considering to change it to save a few instructions and
> go for the more efficient goto based interface in glibc.
> 
> > 
> > ppc = tcheck... should be fine, other than the name.
> 
> Well x and tm doesn't really matter, but I already have x* so i'm inclined
> to keep it, unless people bikeshed too strongly. It should work for PPC too.

Well if you're moving it out of generic code then it doesn't really
matter anymore.  

Mikey

> 
> BTW if the percpu include loop hell is ever sorted out _xtest may
> even stop using XTEST.
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