Re: [Xen-devel] [PATCH v5 1/4] VT-d PI: track the number of vcpus on pi blocking list

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 01.09.17 at 03:39, <chao.gao@xxxxxxxxx> wrote:
> After thinking it again, I want to define the counter as
> a unsigned int variable for the following reasion:
> 1. It is definite that the counter is closely related with
> list_add() and list_del(). If the list is protected by the
> lock, it is straightforward that the counter is also protected
> by the lock.
> 2. In patch 3, althought there are some lock-less readers, we
> will check the counter still meets our requirement with the lock
> held. Thus, I don't think there is a racing issue.

I think that's fine, but then you still don't need LOCKed accesses
to the counter for updating it; write_atomic() will suffice afaict.

Jan


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