REPL locks up after `using Gtk4` in julia 1.11 with multiple threads

[jwahlstrand]

When Julia 1.11 is started with more than one interactive thread, or started with 2 or more default threads and no interactive thread, the REPL locks up after calling using Gtk4. So this occurs when starting julia with julia -t y or julia -t x,y for y>1.

Reported here jwahlstrand/AravisCameras.jl#5 but it's a Gtk4 issue. I can reproduce it on Linux and others have reported it on Mac OS and Windows.

It doesn't happen in Julia 1.10.

[srikumarks]

Just encountered this. It looks like it is not locked entirely (at least on MacOS), every key stroke take several seconds to be delivered, but they eventually do get delivered. So this is perhaps due to some cross-event loop communication issues (between Julia's event loop and Gtk's) ... perhaps.

[jwahlstrand]

Thanks, good to know it's an issue on MacOS too. I do think it's an event loop conflict of some kind but am not sure what do to about it. For me at least, it can be avoided by starting Julia with julia -t N,1 (or setting the environment variable JULIA_NUM_THREADS = N,1). It deserves a note in the README and the documentation.

[RechercheStochastique]

It happens on Windows 11 as well.