Re: [PATCH v2] vpci: introduce per-domain lock to protect vpci structure

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

On 15.02.22 18:18, Jan Beulich wrote:
> On 15.02.2022 16:46, Oleksandr Andrushchenko wrote:
>> Question: can anyone please explain why pcidevs is a recursive lock?
> Well, assuming you did look at the change making it so, can you be a
> little more specific with your question? Are you perhaps suggesting
> the original reason has disappeared, and no new one has appeared? I'm
> afraid I have to repeat what I did say before: If you want to remove
> the recursive nature of the lock, then it is all on you to prove that
> there's no code path where the lock is taken recursively. IOW even if
> no-one knew of a reason, you'd still need to provide this proof.
> Unless of course we'd all agree we're okay to take the risk; I don't
> see us doing so, though.
The question was exactly as asked: I don't understand why it is
recursive and for what reason. I am not suggesting we blindly
change it to a normal spinlock.

My impression was that the code is structured in a way
that the same functionality is coded such as functions,
which already hold the lock, can call others which are
about to acquire the same. So, that allowed not introducing
XXX and XXX_unlocked function pairs which can be done
for many reasons.

That's it

> Jan
>
>
Thank you,
Oleksandr