Re: [Xen-devel] [PATCH 4/4] xen/x86: Correct mandatory and SMP barrier definitions

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.12.16 at 11:05, <andrew.cooper3@xxxxxxxxxx> wrote:
> Barriers are a complicated topic, a common source of confusion in submitted
> code, and their incorrect use is a common cause of bugs.  It *really* doesn't
> help when Xen's API is the same as Linux, but its ABI different.
> 
> Bring the two back in line, so programmers stand a chance of actually getting
> their use correct.
> 
> As Xen has no current need for mandatory barriers, leave them commented out to
> avoid accidential misue.

I'm not convinced of this part - common driver code could very well
need to use such barriers, and I would find it rather odd if I had to
first re-introduce them when adding any such. In fact I'm surprised
there's no such use anywhere. (Depending on the discussion on
earlier patches, there may in fact remain a few such uses.)

Jan


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