Re: spin_unlock optimization(i386)

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Sun, 21 Nov 1999 14:08:45 +0100

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Richard B. Johnson wrote:
> The purpose of the lock prefix is not to make the current CPU operation
> atomic. It's to make all other CPUs halt until the operation is complete.
> This gurantees that only one CPU modifies the variable at the same
> time. You are not going to do that with a move.

AFAIK the reason the lock prefix is not permitted with move instructions
is that there's no need. Lock makes read-modify-write instructions
atomic. Aligned writes are atomic already.

-- Jamie

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