Can I guarentee two tasks run on different threads?

General Usage
1

I have what I though would be a simple problem but have been disappointed in julia’s ability regarding it. I have a program that send a bunch of packets over UDP. I want to receive them in julia as follows:

Have a “listener thread” that repeatedly calls recv(...) to read a new UDP packet and update some data (protected by a lock)

using Base.Threads
using Sockets

socket = UDPSocket()
bind(socket, Sockets.localhost, 49691)
lck = ReentrantLock()

data = Vector{UInt8}()
timestamp = Ref(time())

listener = @spawn begin
    println("Thread: $(Threads.threadid())")
    while true
        newdata = recv(socket)
        lock(lck) do
            copy!(data, newdata)
            timestamp[] = time()
        end
    end    
end

Have a “Main thread” that will access the shared data.

println("Thread: $(Threads.threadid())")
while true
    Libc.systemsleep(0.05) # Do stuff
    lock(lck) do
        if timestamp[] < (time() - 0.2)
            @warn "data too old"
        else
            println("Success")
        end
    end
end

The problem I have is that despite running julia with 4 threads, the listener-thread decides to run on thread 1, the same as the main thread. Therefore recv is not called while the main task is running.

As far as I can tell there is NO WAY to ensure that these two tasks run on different threads…

Unfortunately, the example I have given above DOES NOT reproduce the problem I have described… hopefully it helps explain my goal though. Can anyone help? :cry:

2

Julia 1.10 adds an interactive threadpool which should let you do what you want. See Multi-Threading · The Julia Language for the docs

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