mutex-owned.patch

diff --git a/NEWS b/NEWS
index 41e836f..eec2848 100644
--- a/NEWS
+++ b/NEWS
@@ -93,6 +93,11 @@ with all sufficient information, see the ChangeLog file.
       * Module#const_get accepts a qualified constant string, e.g.
         Object.const_get("Foo::Bar::Baz")
 
+  * Mutex
+    * added method:
+      * added Mutex#owned? which returns the mutex is held by current
+        thread or not. [experimental]
+
   * NilClass
     * added method:
       * added nil.to_h which returns {}
diff --git a/test/ruby/test_thread.rb b/test/ruby/test_thread.rb
index 145e021..d2bdd91 100644
--- a/test/ruby/test_thread.rb
+++ b/test/ruby/test_thread.rb
@@ -863,4 +863,31 @@ class TestThreadGroup < Test::Unit::TestCase
     end
     assert_in_delta(t1 - t0, 1, 1, bug5757)
   end
+
+  def test_mutex_owned
+    mutex = Mutex.new
+
+    assert_equal(mutex.owned?, false)
+    mutex.synchronize {
+      assert_equal(mutex.owned?, true)
+    }
+    assert_equal(mutex.owned?, false)
+  end
+
+  def test_mutex_owned2
+    begin
+      mutex = Mutex.new
+      th = Thread.new {
+        mutex.lock
+        sleep
+      }
+
+      sleep 0.01 until th.status == "sleep"
+      assert_equal(mutex.locked?, true)
+      assert_equal(mutex.owned?, false)
+    ensure
+      th.kill if th
+    end
+  end
+
 end
diff --git a/thread.c b/thread.c
index 4b1adc1..ecdf279 100644
--- a/thread.c
+++ b/thread.c
@@ -4151,6 +4151,28 @@ rb_mutex_lock(VALUE self)
     return self;
 }
 
+/*
+ * call-seq:
+ *    mutex.owned?  -> true or false
+ *
+ * Returns +true+ if this lock is currently held by current thread.
+ * <em>This API is experimental, and subject to change.</em>
+ */
+static VALUE
+rb_mutex_owned_p(VALUE self)
+{
+    VALUE owned = Qfalse;
+    rb_thread_t *th = GET_THREAD();
+    rb_mutex_t *mutex;
+
+    GetMutexPtr(self, mutex);
+
+    if (mutex->th == th)
+	owned = Qtrue;
+
+    return owned;
+}
+
 static const char *
 rb_mutex_unlock_th(rb_mutex_t *mutex, rb_thread_t volatile *th)
 {
@@ -4733,6 +4755,7 @@ Init_Thread(void)
     rb_define_method(rb_cMutex, "lock", rb_mutex_lock, 0);
     rb_define_method(rb_cMutex, "unlock", rb_mutex_unlock, 0);
     rb_define_method(rb_cMutex, "sleep", mutex_sleep, -1);
+    rb_define_method(rb_cMutex, "owned?", rb_mutex_owned_p, 0);
 
     recursive_key = rb_intern("__recursive_key__");
     rb_eThreadError = rb_define_class("ThreadError", rb_eStandardError);