Re: [Xen-devel] [PATCH 6/7] mini-os: Added rmb to xenbus code

[Thomas Leonard <talex5@xxxxxxxxx>]

On 9 June 2014 14:56, Thomas Leonard <talex5@xxxxxxxxx> wrote:
> On 6 June 2014 17:40, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
>> On Fri, 2014-06-06 at 17:10 +0200, Samuel Thibault wrote:
>>> Ian Campbell, le Fri 06 Jun 2014 15:15:42 +0100, a Ãcrit :
>>> > On Fri, 2014-06-06 at 05:59 +0100, karim.allah.ahmed@xxxxxxxxx wrote:
>>> > > In any case, by looking at the patch it seems like rmb was required to
>>> > > make sure that the reply message is visible to the current processor
>>> > > when this thread wakes up and starts reading it.
>>> >
>>> > Can we assume (or arrange) that schedule() gives us this guarantee? Do
>>> > we want to?
>>>
>>> I'd tend to think something like that, yes. More precisely, thread
>>> wait/wake primitives usually provide a barrier: events before the wake
>>> are supposed to complete before the wait returns. So both should have a
>>> memory barrier.
>>
>> Makes sense to me.
>
> I'm not sure I understand this. Looking again at the code:

Sorry. I was looking at the wrong rmb.


-- 
Dr Thomas Leonard        http://0install.net/
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