Julia hangs on `using PProf`

I’m trying to do some allocation profiling.

I start a thread, which is reading from a pipe, and I want to check that it is not allocating.

Then, I do using PProf and julia hangs.

If I do using PProf before starting this thread, it does not hang.

What is causing this?

Done a little more investigation - probably more to do with what’s going in the thread than with PProf.

It seems to be causing other things to hang as well