On 2011-Mar-16 16:34:04 -0400, Jung-uk Kim <j...@freebsd.org> wrote: >On Wednesday 16 March 2011 01:45 pm, Roman Divacky wrote: >> if we drop i486 I think it makes sense to require something that >> has at least SSE2, thus we can have the same expectations as on >> amd64.
I think it's stil a bit early for that - especially the SSE2 requirement. >This is a proof-of-concept patch for sys/x86/isa/clock.c: > >http://people.freebsd.org/~jkim/clock.diff > >You see the complexity, just because I wanted to load 64-bit value >atomically... :-( An alternative approach is to have _fetch_frequency() be uint64_t (*_fetch_frequency)(uint64_t *); if i386 and I486 are defined (otherwise it's just the #define (*(p))) then initialise it to either atomic_fetch_quad_i386 or atomic_fetch_quad_i586 as part of the CPU detection process. This is the way bcopy() is/was handled on Pentium. Another approach would be to always have cmpxchg8b instructions (followed by a suitably large NOP) always inlined in the code and if it traps, patch the code to call a function that emulates it. -- Peter Jeremy
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