Re: [Q] Looking for an emulation for CMOV* instructions.

H. Peter Anvin (hpa@zytor.com)
11 Jan 2002 23:52:50 -0800

Followup to: <p737kqpp60w.fsf@oldwotan.suse.de>
By author: Andi Kleen <ak@suse.de>
In newsgroup: linux.dev.kernel
>
> One corner case where emulation would IMHO make sense would be CMPXCHG8.
> It would allow to do efficient inline mutexes in pthreads, and hit the
> emulation only on 386/486. cpu feature flag checking is unfortunately
> not an option normally for inline code.
>

You don't need CMPXCHG8B to do efficient inline mutexes. In fact, the
pthreads code for i386 uses the same mutexes the kernel does (LOCK INC
based, I believe), complete with section hacking to make them
efficiently inlinable -- and then they're put inside a function call.
I believe "kill me now" is an appropriate response.

-hpa

-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt	<amsp@zytor.com>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/