Messages in this thread | | | Date | Sun, 12 Aug 2007 12:23:41 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [patch 01/23] Fall back on interrupt disable in cmpxchg8b on 80386 and 80486 |
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* Jan Engelhardt (jengelh@computergmbh.de) wrote: > > On Aug 12 2007 10:54, Mathieu Desnoyers wrote: > > >Date: Sun, 12 Aug 2007 10:54:35 -0400 > >From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> > >To: <akpm@linux-foundation.org>, <linux-kernel@vger.kernel.org> > >Cc: Christoph Lameter <clameter@sgi.com>, > > Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>, <mingo@redhat.com> > >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 majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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