[erlang-questions] When to release resources in NIF?

[Soup]

Theoretically, you should be able to use the "upgrade" or "reload"
callbacks in your NIF instead of the unload callback. It may be necessary
to perform the upgrade as an app/relup to use that feature, though. Perhaps
someone a bit more versed on NIF modules can shed some light.

At the very least you need to specify one of those two callback functions.

~Soup


On Fri, Mar 21, 2014 at 1:15 PM, Attila Rajmund Nohl <
attila.r.nohl@REDACTED> wrote:

> Hello!
>
> I have a NIF module that uses a locks to protect a common resource.
> The locks are created using enif_rwlock_create in the load function
> and destroyed in the unload function. When I first load the Erlang
> module, the locks are initialized and everything is OK. When I compile
> the module in the same VM the first time, everything is still OK. When
> I compile it the second time, the old version of the module is
> unloaded, so unload is called. At this point I'm in trouble, because
> the unload function destroys the lock.
>
> I'm not quite sure how to correctly handle this situation. Somehow I
> should keep (or destroy/create) the locks in the upgrade step, but
> after the second compilation the locks are already deleted by unload.
> I could add a flag to the private data stating that the locks were
> already destroyed or not, but it feels hackish. What is the correct
> way?
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