Re: spin_unlock optimization(i386)

Stefan Monnier (monnier+lists/linux/kernel/news/@tequila.cs.yale.edu)
30 Nov 1999 02:34:01 -0500

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>>>>> "Andrea" == Andrea Arcangeli <andrea@suse.de> writes:
> Because the write buffer as documented is not allowed to show changes to
> the other cpus not in processor order. It can only delay the writes
> undefinitely but that make no difference at all for SMP.

Of course it makes a difference:

A = 1 B = 0
read B read A

You might very well get `read A=0' and `read B=1' even though this
does not correspond to any UP interleaving of the two threads.

Stefan

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