wasi-nn + threads

[yamt]

wasm_deinstantiate and aot_deinstantiate call wasi_nn_destroy only for !is_sub_inst.

on the other hand, wasm_runtime_get_wasi_nn_ctx seems to allocate the context for each instances.

probaby it just means that (this implementation of?) wasi-nn is not compatible with threads.

[tonibofarull]

wasi-nn context is managed within the library.
The motivations are the following:

1. Allowing the user to build it as a native library.
2. Avoid coupling with WAMR as much as possible.

What would be required to support it with threads? Reduce the granularity of the context from wasm instance to thread?

[yamt]

What would be required to support it with threads?

i don't know.
probably

• share the context among instances. (wasi-threads and lib-pthread are using instance per thread model)
• add some locks