[openib-general] Re: [PATCH (updated)] ipoib: dont lock tx on completion

[Michael S. Tsirkin]

Quoting r. Roland Dreier <roland at topspin.com>:
> Subject: Re: [PATCH (updated)] ipoib: dont lock tx on completion
> 
>     Michael> Can they be moved to before the wmb? I think not.
> 
> Why not?  All wmb() does is guarantee that stores issued before the
> wmb() will complete before stores issued after the wmb().  It doesn't
> even say anything about when the stores have to complete, let alone
> the order of loads.  The most obvious definition is for sparc64, where
> we have
> 
> 	#define wmb()           membar("#StoreStore")
> 
> which my Sparc reference manual says only means
> 
>     Forces all stores after the MEMBAR to wait until all stores before
>     the MEMBAR have reached global visibility.
> 
> ppc is similar, where wmb() is just "eieio."
> 
>  - R.
> 

OK, so means we must make them both mb(). Sigh.

-- 
MST - Michael S. Tsirkin