From 6478ecd2aeba5221cfc57ad2c17030c0c78c3b19 Mon Sep 17 00:00:00 2001
From: Ian <i.r.butterworth@gmail.com>
Date: Sat, 24 Oct 2020 08:32:47 -0400
Subject: [PATCH 1/3] do checked_import sequentially

---
 src/loadsave.jl | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/src/loadsave.jl b/src/loadsave.jl
index e457a520..db7a35cf 100644
--- a/src/loadsave.jl
+++ b/src/loadsave.jl
@@ -1,5 +1,6 @@
 const sym2loader = Dict{Symbol,Vector{Symbol}}()
 const sym2saver  = Dict{Symbol,Vector{Symbol}}()
+const load_locker = Base.ReentrantLock()
 
 is_installed(pkg::Symbol) = get(Pkg.installed(), string(pkg), nothing) != nothing
 
@@ -16,18 +17,20 @@ function topimport(modname)
 end
 
 function checked_import(pkg::Symbol)
-    # kludge for test suite
-    if isdefined(Main, pkg)
-        m1 = getfield(Main, pkg)
-        isa(m1, Module) && return m1
-    end
-    if isdefined(FileIO, pkg)
-        m1 = getfield(FileIO, pkg)
-        isa(m1, Module) && return m1
+    lock(load_locker) do
+        # kludge for test suite
+        if isdefined(Main, pkg)
+            m1 = getfield(Main, pkg)
+            isa(m1, Module) && return m1
+        end
+        if isdefined(FileIO, pkg)
+            m1 = getfield(FileIO, pkg)
+            isa(m1, Module) && return m1
+        end
+        m = _findmod(pkg)
+        m == nothing || return Base.loaded_modules[m]
+        topimport(pkg)
     end
-    m = _findmod(pkg)
-    m == nothing || return Base.loaded_modules[m]
-    topimport(pkg)
     return Base.loaded_modules[_findmod(pkg)]
 end
 

From f4ee837739f86d794a895fde285d0991d14f7db9 Mon Sep 17 00:00:00 2001
From: Ian <i.r.butterworth@gmail.com>
Date: Sat, 24 Oct 2020 08:44:33 -0400
Subject: [PATCH 2/3] bring return into lock

---
 src/loadsave.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/loadsave.jl b/src/loadsave.jl
index db7a35cf..a5dd85dc 100644
--- a/src/loadsave.jl
+++ b/src/loadsave.jl
@@ -30,8 +30,8 @@ function checked_import(pkg::Symbol)
         m = _findmod(pkg)
         m == nothing || return Base.loaded_modules[m]
         topimport(pkg)
+        return Base.loaded_modules[_findmod(pkg)]
     end
-    return Base.loaded_modules[_findmod(pkg)]
 end
 
 

From c292520802c7f995458a32406d9944c2343b9b5d Mon Sep 17 00:00:00 2001
From: Ian <i.r.butterworth@gmail.com>
Date: Sat, 24 Oct 2020 11:16:51 -0400
Subject: [PATCH 3/3] add multithreaded save test

---
 .appveyor.yml    | 1 +
 .travis.yml      | 2 ++
 test/loadsave.jl | 7 +++++++
 test/runtests.jl | 2 ++
 4 files changed, 12 insertions(+)

diff --git a/.appveyor.yml b/.appveyor.yml
index ffa0eb5f..6e6cf9ec 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -1,4 +1,5 @@
 environment:
+  JULIA_NUM_THREADS: 2
   matrix:
   - julia_version: 0.7
   - julia_version: 1.0
diff --git a/.travis.yml b/.travis.yml
index 48ad8cd9..b05a4d61 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,6 +7,8 @@ julia:
   - 1.0
   - 1
   - nightly
+env:
+  - JULIA_NUM_THREADS=2
 matrix:
   allow_failures:
     - julia: nightly
diff --git a/test/loadsave.jl b/test/loadsave.jl
index 7c85967a..d4dbd2dd 100644
--- a/test/loadsave.jl
+++ b/test/loadsave.jl
@@ -255,6 +255,13 @@ end # module Dummy
     @test load(fn) == a
     rm(fn)
 
+    if Threads.nthreads() > 1
+        Threads.@threads for i in 1:(Threads.nthreads() * 5)
+            fn = string(tempname(), ".dmy")
+            save(fn, a)
+        end
+    end
+
     # force format
     fn = string(tempname(), ".dmy")
     savestreaming(format"DUMMY", fn) do writer
diff --git a/test/runtests.jl b/test/runtests.jl
index aa39fb21..b8adb3bc 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -2,6 +2,8 @@ using FileIO
 using FilePathsBase
 using Test
 
+Threads.nthreads() <= 1 && @info "Threads.nthreads() = $(Threads.nthreads()), multithread tests will be disabled"
+
 # Both FileIO and FilePathsBase export filename, but we only want the FileIO definition.
 using FileIO: filename