1 files changed, 92 insertions, 0 deletions
diff --git a/spec/ruby/core/mutex/lock_spec.rb b/spec/ruby/core/mutex/lock_spec.rb
new file mode 100644
index 0000000000..4fee29091a
--- /dev/null
+++ b/spec/ruby/core/mutex/lock_spec.rb
@@ -0,0 +1,92 @@
+require_relative '../../spec_helper'
+
+describe "Mutex#lock" do
+  it "returns self" do
+    m = Mutex.new
+    m.lock.should == m
+    m.unlock
+  end
+
+  it "blocks the caller if already locked" do
+    m = Mutex.new
+    m.lock
+    -> { m.lock }.should block_caller
+  end
+
+  it "does not block the caller if not locked" do
+    m = Mutex.new
+    -> { m.lock }.should_not block_caller
+  end
+
+  # Unable to find a specific ticket but behavior change may be
+  # related to this ML thread.
+  it "raises a deadlock ThreadError when used recursively" do
+    m = Mutex.new
+    m.lock
+    -> {
+      m.lock
+    }.should.raise(ThreadError, /deadlock/)
+  end
+
+  it "raises a deadlock ThreadError when multiple fibers from the same thread try to lock" do
+    m = Mutex.new
+
+    m.lock
+    f0 = Fiber.new do
+      m.lock
+    end
+    -> { f0.resume }.should.raise(ThreadError, /deadlock/)
+
+    m.unlock
+    f1 = Fiber.new do
+      m.lock
+      Fiber.yield
+    end
+    f2 = Fiber.new do
+      m.lock
+    end
+    f1.resume
+    -> { f2.resume }.should.raise(ThreadError, /deadlock/)
+  end
+
+  it "does not raise deadlock if a fiber's attempt to lock was interrupted" do
+    lock = Mutex.new
+    main = Thread.current
+
+    t2 = nil
+    t1 = Thread.new do
+      loop do
+        # interrupt fiber below looping on synchronize
+        sleep 0.01
+        t2.raise if t2
+      end
+    end
+
+    # loop ten times to try to handle the interrupt during synchronize
+    t2 = Thread.new do
+      10.times do
+        Fiber.new do
+          begin
+            loop { lock.synchronize {} }
+          rescue RuntimeError
+          end
+        end.resume
+
+        Fiber.new do
+          -> do
+            lock.synchronize {}
+          end.should_not.raise(ThreadError)
+        end.resume
+      rescue RuntimeError
+        retry
+      end
+    end
+    t2.join
+  ensure
+    t1.kill rescue nil
+    t2.kill rescue nil
+
+    t1.join
+    t2.join
+  end
+end