FileIO is not threadsafe about fileio.jl

[c42f]

Yes, the fact that the crash happens during a call to require() was concerning.

Perhaps this indicates that Base.require itself is not threadsafe, because it appears to use plain Base.Condition, rather than Threads.Condition.

[johnnychen94]

For the record, #339 fixes this for Julia >= 1.3. For old Julia versions, it's still broken.

[johnnychen94]

I see the require(uuidkey::Base.PkgId) is called in the error callstack, so this thread issue perhaps happens during the io backend loading time.

@IanButterworth is this the exact reason that we have checked_import in ImageIO.jl? https://github.com/JuliaIO/ImageIO.jl/blob/bae08524621a7b14c1d1d9e9d77c9117e3e85807/src/ImageIO.jl#L25-L32

[KristofferC]

Calls to require should very likely be behind a lock.