Re: Is 386 processor still supported?

[Ingo Molnar]

* Maciej W. Rozycki <macro@xxxxxxxxxxxxxx> 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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