* Jan Engelhardt ([EMAIL PROTECTED]) wrote: > > On Aug 12 2007 10:54, Mathieu Desnoyers wrote: > > >Date: Sun, 12 Aug 2007 10:54:35 -0400 > >From: Mathieu Desnoyers <[EMAIL PROTECTED]> > >To: <[EMAIL PROTECTED]>, <[email protected]> > >Cc: Christoph Lameter <[EMAIL PROTECTED]>, > > Mathieu Desnoyers <[EMAIL PROTECTED]>, <[EMAIL PROTECTED]> > >Subject: [patch 01/23] Fall back on interrupt disable in cmpxchg8b on 80386 > >and > > 80486 > > > >Actually, on 386, cmpxchg and cmpxchg_local fall back on > >cmpxchg_386_u8/16/32: it disables interruptions around non atomic > >updates to mimic the cmpxchg behavior. > > > >The comment: > >/* Poor man's cmpxchg for 386. Unsuitable for SMP */ > > > >already present in cmpxchg_386_u32 tells much about how this cmpxchg > >implementation should not be used in a SMP context. However, the > >cmpxchg_local > >can perfectly use this fallback, since it only needs to be atomic wrt the > >local > >cpu. > > > >This patch adds a cmpxchg_486_u64 and uses it as a fallback for cmpxchg64 > >and cmpxchg64_local on 80386 and 80486. > > hm, but why is it called cmpxchg_486 when the other functions are called > cmpxchg_386? >
Because the standard cmpxchg is missing only on 386, but cmpxchg8b is missing both on 386 and 486. Citing Intel's Instruction set reference: cmpxchg: This instruction is not supported on Intel processors earlier than the Intel486 processors. cmpxchg8b: This instruction encoding is not supported on Intel processors earlier than the Pentium processors. Mathieu > > Jan > -- -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
