Provide pid in imports callback context

[ionull]

Then we can call exported functions in imported functions.

[ionull]

Sorry, there must be some other way to do this:
** (EXIT) process attempted to call itself

[ionull]

When I call the exported function in the imports function callback, there is a timeout exception. Any idea?

[tessi]

hey @ionull - I believe I know where the timeout comes from. My suspicion is that this is a rust-side mutex the code it waiting on indefinitely that causes the timeout in elixir-land.

What happens when rust calls into an elixir function is that we have an unlocked mutex on the store_or_caller (the place we all wasm state is stored). That mutex stays locked during the call. Now when you, in elixir-land, call back into rust we need to access that same store_or_caller to mutate the wasm state, trying to unlock that same mutex. But it will never unlock, because we're still running the imported elixir-function.

[ionull]

Hi @tessi , the problem is that GenServer has not replied, and the status is locked on the GenServer side, where you can't call with pid, but we still can use the instance to call the wasm exported function like this:
Wasmex.Instance.call_exported_function(store, instance, "__demo_export_0", [a,b],:from)
receive do {:returned_function_call, {:ok, [result]}, :from} -> :ok result after 1000 -> raise "timeout on exported function call" end
It's quite useful if we can get pid and instance from callback context.

[tessi]

uhh, interesting. so I was wrong. Nice to learn something :) I get why this is useful. Could you add a test for this scenario, please, so we can make sure not to break it in the future?

[ionull]

@tessi Hi, test case done.

[tessi]

@tessi Hi, test case done.

perfect! the case looks great to me. thanks a lot. let's see what CI says and merge when/if it's green :)

[ionull]

Is there anything else that I should do?

[tessi]

I wanted to say no, but the formatter is still upset. can you make sure mix format --check-formatted works? probably running mix format and a new commit is enough. Other than making formatters happy, I'm happy to merge :)

[ionull]

@tessi oh, I see. Have done the mix format, please check

[tessi]

@tessi oh, I see. Have done the mix format, please check

Thanks! And thanks again for your work 💚