Re: Waiting on Sockets or File Descriptors

If I understood this right, then I can use forkIO to run a "safe" FFI function which blocks, but in the threaded RTS this will not block all other FFI calls.

Right.

So what happens in the non-threaded RTS? Now the blocking yet "safe" FFI invocation _would_ block other FFI calls but not evaluation of "pure Haskell" code. Is that right?

No. All execution of Haskell code is blocked, as there is really only one operating system thread in the whole system. Cheers, Wolfgang