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SubjectRe: Is 386 processor still supported?

* Maciej W. Rozycki <macro@linux-mips.org> wrote:

> On Thu, 15 Jan 2009, Alan Cox wrote:
>
> > > UP emulation of CMPXCHG and XADD for userland should be rather trivial,
> > > so why not include it like with LL/SC for MIPS?
> >
> > Why not just ship an additional libc with the right options ?
>
> Does not work for MIPS as glibc has no equivalent code for pre-LL/SC
> CPUs and LL/SC is always used. For the i386 the situation seems worse
> yet as for pre-i486 CPUs a generic C implementation of
> compare-and-exchange is used guaranteeing silent thread unsafety. :(
>
> IMO, a kernel emulation of CMPXCHG and XADD (both are used by
> sysdeps/i386/i486/bits/atomic.h in glibc) with an optional LOCK prefix,
> guaranteeing UP atomicity would be a cheap way to provide long-term i386
> userland support with little burden for both Linux and respective user
> software maintainers. Certainly it adds some bloat to the kernel, but I
> think it is not an option that should be outright dismissed without
> consideration.

patches are welcome ...

Ingo


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