How to ensure a thread cannot be blocked by the GC?

[ponce via Digitalmars-d-learn]

I have a DLL written in D that gets called by two different 
threads, created by a non-D host program (audio plugin). I did 
not create those threads, but my understanding is that they get 
"attached" to the D runtime.

Thread A is a real-time callback and should not ever block. @nogc 
seems perfect for this.

Thread B and it's impractical to make it @nogc.

How to ensure that a collection triggered by thread B never stop 
thread A in stop the world collections?