Re: [LAD] Atomic Operations

On Monday 14 December 2009, at 21.21.55, Paul Davis
<paul@email-addr-hidden> wrote:
> On Mon, Dec 14, 2009 at 3:04 PM, Nick Copeland
>
> <nickycopeland@email-addr-hidden> wrote:
> >> guaranteed for 24 bits of a 32 bit value. funny old world, eh? :)
> >
> > Wasn't that just for 32 bit floats though? They were implemented as a
> > structure
> > that implied multiple write operations, they only garanteed the mantissa,
> > not the exponent. I am pretty sure integer memory IO was guaranteed as
> > that is where the 24 bits came from.
>
> the kernel implementation of atomic integer writes suggested
> otherwise, if my memory holds correct.
> since the kernel doesn't have atomic float ops, and i did see kernel
> code for this that noted
> the issue, i think my memory is correct. but its been wrong so many
> times before.

I have a faint memory of this having to do with the memory subsystem of SPARC
SMP systems... I'm not so sure this has much to do with atomic reads and
writes, though. A quick search gave me this:

        http://lwn.net/Articles/71732/

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