Expose scheduler as public interface & bug fixes. (#3945)

* Rename `rb_scheduler` to `rb_fiber_scheduler`.

* Use public interface if available.

* Use `rb_check_funcall` where possible.

* Don't use `unblock` unless the fiber was non-blocking.

1 files changed, 45 insertions, 0 deletions

diff --git a/test/fiber/test_thread.rb b/test/fiber/test_thread.rb
new file mode 100644
index 0000000000..5fc80f0e6c
--- /dev/null
+++ b/test/fiber/test_thread.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+require "test/unit"
+require_relative 'scheduler'
+
+class TestFiberThread < Test::Unit::TestCase
+  def test_thread_join
+    thread = Thread.new do
+      scheduler = Scheduler.new
+      Fiber.set_scheduler scheduler
+
+      result = nil
+      Fiber.schedule do
+        result = Thread.new{:done}.value
+      end
+
+      scheduler.run
+      result
+    end
+
+    assert_equal :done, thread.value
+  end
+
+  def test_thread_join_blocking
+    thread = Thread.new do
+      scheduler = Scheduler.new
+      Fiber.set_scheduler scheduler
+
+      result = nil
+      Fiber.schedule do
+        Fiber.new(blocking: true) do
+          # This can deadlock if the blocking state is not taken into account:
+          Thread.new do
+            sleep(0)
+            result = :done
+          end.join
+        end.resume
+      end
+
+      scheduler.run
+      result
+    end
+
+    assert_equal :done, thread.value
+  end
+end