merges r21148 from trunk into ruby_1_9_1.

* thread.c (rb_mutex_trylock): return false if Mutex owned
  by current thread.  [ruby-core:20943]
* thread.c (rb_mutex_lock): check dead lock (recursive lock) here.
* test/ruby/test_thread.rb: add a test.

git-svn-id: http://svn.ruby-lang.org/repos/ruby/branches/ruby_1_9_1@21160 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 12 insertions, 0 deletions

diff --git a/test/ruby/test_thread.rb b/test/ruby/test_thread.rb
index 97e58cd9e..b460cadea 100644
--- a/test/ruby/test_thread.rb
+++ b/test/ruby/test_thread.rb
@@ -438,6 +438,18 @@ class TestThread < Test::Unit::TestCase
     assert_equal(false, m3.locked?)
   end
 
+  def test_mutex_trylock
+    m = Mutex.new
+    assert_equal(true, m.try_lock)
+    assert_equal(false, m.try_lock, '[ruby-core:20943]')
+
+    Thread.new{
+      assert_equal(false, m.try_lock)
+    }.join
+
+    m.unlock
+  end
+
   def test_recursive_error
     o = Object.new
     def o.inspect