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    SubjectRe: Is 386 processor still supported?

    * Maciej W. Rozycki <> 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 ...


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