linux-kernel - Re: [PATCH] x86: remove byte locks

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Message-ID: <20090112124401.GA31939@elte.hu>
Date:	Mon, 12 Jan 2009 13:44:01 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Jeremy Fitzhardinge <jeremy@...source.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86: remove byte locks


* Jiri Kosina <jkosina@...e.cz> wrote:

> On Mon, 12 Jan 2009, Ingo Molnar wrote:
> 
> > > Remove byte locks implementation, which was introduced by Jeremy in 
> > > 8efcbab6 ("paravirt: introduce a "lock-byte" spinlock implementation"), 
> > > but turned out to be dead code that is not used by any in-kernel 
> > > virtualization guest (Xen uses its own variant of spinlocks implementation 
> > > and KVM is not planning to move to byte locks).
> > > 
> > > Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> > > ---
> > >  arch/x86/include/asm/paravirt.h      |    2 -
> > >  arch/x86/include/asm/spinlock.h      |   66 +--------------------------------
> > >  arch/x86/kernel/paravirt-spinlocks.c |   10 -----
> > >  3 files changed, 2 insertions(+), 76 deletions(-)
> > didnt you send a patch in this lkml thread:
> > 
> >   Subject: Re: Is 386 processor still supported?
> 
> > that makes use of byte-locks on i386 ?
> 
> I did, but that patch was bogus, as we indeed don't support smp on M386.
> 
> This is totally independent -- it just removes dead code (byte locks) that 
> has no in-tree user at all.
> 
> > But i guess we should solve M386 and M486 by only allowing it on !SMP, 
> > hence spinlock support is moot there, right?
> 
> Agreed. But that's a different issue.

ok. Jeremy, can we apply Jiri's patch or do you still have plans with that 
code?

	Ingo
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