Messages in this thread | | | Date | Thu, 15 Jan 2009 15:20:47 +0100 | From | Jan-Benedict Glaw <> | Subject | Re: Is 386 processor still supported? |
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On Thu, 2009-01-15 14:15:56 +0000, 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.
I just searched for the old patch, but couldn't find it ad hoc. (But it must be somewhere, at least in the archives, I guess?)
The kernel emulator has the benefit of no overhead when not switched on, and low-to-no overhead when not being used (i386 capable kernel on i486 hardware).
Heck, I'd dig out my two test systems and give them a try with current Debian unstable. Should be fun with four to eight megabytes of RAM.
MfG, JBG
-- Jan-Benedict Glaw jbglaw@lug-owl.de +49-172-7608481 Signature of: 23:53 <@jbglaw> So, ich kletter' jetzt mal ins Bett. the second : 23:57 <@jever2> .oO( kletter ..., hat er noch Gitter vorm Bett, wie früher meine Kinder?) 00:00 <@jbglaw> jever2: *patsch* 00:01 <@jever2> *aua*, wofür, Gedanken sind frei! 00:02 <@jbglaw> Nee, freie Gedanken, die sind seit 1984 doch aus! 00:03 <@jever2> 1984? ich bin erst seit 1985 verheiratet! [unhandled content-type:application/pgp-signature] | |