On 4/18/10, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Sat, 2010-04-17 at 16:48 -0400, Tom Lane wrote:
> > There are some places where we suppose that a *single* write into shared
> > memory can safely be done without a lock, if we're not too concerned
> > about how soon other transactions will see the effects. But what you
> > are proposing here requires more than one related write.
> > I've been burnt by this myself:
> > http://archives.postgresql.org/pgsql-committers/2008-06/msg00228.php
> W O W - thank you for sharing.
> What I'm not clear on is why you've used a spinlock everywhere when only
> weak-memory thang CPUs are a problem. Why not have a weak-memory-protect
> macro that does does nada when the hardware already protects us? (i.e. a
> spinlock only for the hardware that needs it).
Um, you have been burned by exactly this on x86 also:
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