[systemd-devel] [PATCH 2/2] domain: grab the domain's parent lock only when needed

[Daniel Mack]

On 03/21/2014 12:35 PM, Djalal Harouni wrote:
> I've two questions:
> 
> 1) Can we improve it in ordre to reduce the lock hold time ?

We don't consider that a very frequent operation, so we never thought
about optimizing this code path. What use case do you have in mind so
that performance would matter much?

> currently creating a domain will make create/disconnect/open... buses
> and endpoints on the parent of that domain block, these are separated
> operations on different domains.

I don't quite follow. Can you elaborate?

> Also it seems that now there is only support for one level of nested
> domains? will this be increased?

I don't think so. What's your use case here?

> 2) What about creating custom endpoints on the bus that was already
> unrefed ? IMHO this is the same scenario!

That shouldn't happen of course. We've been dealing with locking in that
area quite a bit, but we might have overlooked something. Please send a
patch if you see such an unsafe locking scenario.

> Hmm perhaps this can be improved by taking a ref ASAP and revalidate
> objects by checking the "*->disconnected" ?

->disconnected isn't so much of an issue, and we do check for it where
necessary. Apart from that, users that store a pointer to any object
should take a reference, so it can't disappear underneath them. But
again, if you think we've overlooked anything, let us know. Reviewing
all these details is certainly much appreciated.


Thanks,
Daniel