Re: [PATCH] synchronize_irq needs a barrier

On Thu, 2007-10-18 at 22:35 +0800, Herbert Xu wrote:

Benjamin Herrenschmidt [off-list ref] wrote:

quoted

Note that some kind of read barrier or compiler barrier should be needed
regardless, or we are just not sync'ing with anything at all (we may
have loaded the value ages ago and thus operate on a totally stale
value). I prefer a full barrier to also ensure all previous stores are
pushed out.

We already have a compiler barrier there in the form of cpu_relax.

Isn't it too late ? The barrier should be before the test_bit, to
prevent it from moving up.

Ben.