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

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Date:	Mon, 12 Jan 2009 13:36:19 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Jeremy Fitzhardinge <jeremy@...source.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: remove byte locks

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.

Thanks,

-- 
Jiri Kosina
SUSE Labs
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