move package loading behind a lock (#339)

* move package loading behind a lock

* add threaded loading test

only run threaded test on Julia >= 1.3

Co-authored-by: Johnny Chen <johnnychen94@hotmail.com>

Author: Kristoffer Carlsson

src/loadsave.jl

@@ -192,14 +192,15 @@ const fileiofuncs = Dict{Symbol,Function}(:load => load,
                                           :save => save,
                                           :savestreaming => savestreaming)
 
+const require_lock = ReentrantLock()
 function action(call::Symbol, libraries::Vector{ActionSource}, @nospecialize(file::Formatted), args...; options...)
     issave = call ∈ (:save, :savestreaming)
     failures = Tuple{Any,ActionSource,Vector}[]
     pkgfuncname = Symbol("fileio_", call)
     local mod
     for library in libraries
         try
-            mod = isa(library, Module) ? library : Base.require(library)
+            mod = isa(library, Module) ? library : lock(() -> Base.require(library), require_lock)
             f = if isdefined(mod, pkgfuncname)
                 getfield(mod, pkgfuncname)
             else

test/runtests.jl

@@ -12,6 +12,12 @@ struct MimeSaveTestType
 end
 
 @testset "FileIO" begin
+    # This threaded test should be put before `CSVFiles` is loaded
+    if VERSION >= v"1.3"
+        # FIXME: threaded file io is still somehow broken in old Julia versions
+        include("threaded_loading.jl")
+    end
+
     include("query.jl")
     include("loadsave.jl")
     include("error_handling.jl")

test/threaded_loading.jl

@@ -0,0 +1,14 @@
+@testset "Threaded loading" begin
+    if Threads.nthreads() > 1
+        pkgid = Base.PkgId(FileIO.idCSVFiles.second, "CSVFiles")
+        @assert !Base.root_module_exists(pkgid) "threaded loaidng test requires CSVFiles not loaded"
+        # When threaded, loading a new backend should be locked
+        # https://github.com/JuliaIO/FileIO.jl/issues/336
+        files = map(["data.csv", "file.csv"]) do filename
+            joinpath(@__DIR__, "files", filename)
+        end
+        @test_nowarn Threads.@threads for file in files
+            load(file)
+        end
+    end
+end