1 files changed, 22 insertions, 0 deletions
diff --git a/spec/ruby/optional/capi/thread_spec.rb b/spec/ruby/optional/capi/thread_spec.rb
index f60e9ba065..52070198fd 100644
--- a/spec/ruby/optional/capi/thread_spec.rb
+++ b/spec/ruby/optional/capi/thread_spec.rb
@@ -123,5 +123,27 @@ describe "C-API Thread function" do
       # And we got a proper value
       thr.value.should be_true
     end
+
+    it "runs a C function with the global lock unlocked amd unlocks IO with the generic RUBY_UBF_IO" do
+      thr = Thread.new do
+        @t.rb_thread_call_without_gvl_with_ubf_io
+      end
+
+      # Wait until it's blocking...
+      Thread.pass while thr.status and thr.status != "sleep"
+
+      # The thread status is set to sleep by rb_thread_call_without_gvl(),
+      # but the thread might not be in the blocking read(2) yet, so wait a bit.
+      sleep 0.1
+
+      # Wake it up, causing the unblock function to be run.
+      thr.wakeup
+
+      # Make sure it stopped
+      thr.join(1).should_not be_nil
+
+      # And we got a proper value
+      thr.value.should be_true
+    end
   end
 end