Re: [patch] i386 spinlocks: disable interrupts only if we enabledthem

[Nick Piggin]

Andrew Morton wrote:
> Benjamin LaHaise <bcrl@xxxxxxxxx> wrote:
>
> > On Wed, Mar 08, 2006 at 01:43:08AM +0100, Ingo Molnar wrote:
> > > we dont inline that code anymore. So i think the optimization is fine.
> >
> > Why is that?  It adds memory traffic that has to be synchronized 
> > before the lock occurs and clobbered registers now in the caller.
>
>
> Is the inlined lock;decb+jns likely to worsen the text size?  I doubt it. 
> Overall text will get bigger due to the out-of-line stuff, but that's OK.
>
> I'm sure we went over all this, but I don't recall the thinking.

Seems like a very good idea not to clobber any registers in
lock fastpaths. I don't see how that could have been a win
(especially for i386) but still, Ingo must have had a reason
behind it.

--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/