Re: [PATCH 1/4] arch: local64_t

From: David Howells
Date: Fri May 21 2010 - 10:53:20 EST

Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote:

> + * This is the default implementation, which uses atomic64_t. Which is
> + * rather pointless. The whole point behind local64_t is that some processors
> + * can perform atomic adds and subtracts in a manner which is atomic wrt IRQs
> + * running on this CPU. local64_t allows exploitation of such capabilities.

Interesting... What FRV does in atomic64-ops.S should probably be rebranded
local64_t, and atomic64_t ops be based on that in non-SMP mode.

What I did on FRV was to emulate LL/ST instructions using some of the
excessive numbers of conditional bits to do so - but it only works on UP

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