* lib/monitor.rb (mon_try_enter, mon_enter): should reset @mon_count

just in case the previous owner thread dies without mon_exit.
  [fix GH-874] Patch by @chrisberkhout

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50525 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Mon May 18 13:55:01 2015  Shugo Maeda  <shugo@ruby-lang.org>
+
+	* lib/monitor.rb (mon_try_enter, mon_enter): should reset @mon_count
+	  just in case the previous owner thread dies without mon_exit.
+	  [fix GH-874] Patch by @chrisberkhout
+
 Sun May 17 17:21:29 2015  Eric Wong  <e@80x24.org>
 
 	* lib/webrick/utils.rb (set_non_blocking): use IO#nonblock=

lib/monitor.rb

@@ -170,6 +170,7 @@ module MonitorMixin
         return false
       end
       @mon_owner = Thread.current
+      @mon_count = 0
     end
     @mon_count += 1
     return true
@@ -184,6 +185,7 @@ module MonitorMixin
     if @mon_owner != Thread.current
       @mon_mutex.lock
       @mon_owner = Thread.current
+      @mon_count = 0
     end
     @mon_count += 1
   end

test/monitor/test_monitor.rb

@@ -33,6 +33,22 @@ class TestMonitor < Test::Unit::TestCase
     assert_equal((1..10).to_a, ary)
   end
 
+  def test_enter_second_after_killed_thread
+    th = Thread.start {
+      @monitor.enter
+      Thread.current.kill
+      @monitor.exit
+    }
+    th.join
+    @monitor.enter
+    @monitor.exit
+    th2 = Thread.start {
+      @monitor.enter
+      @monitor.exit
+    }
+    assert_join_threads([th, th2])
+  end
+
   def test_synchronize
     ary = []
     queue = Queue.new
@@ -111,6 +127,22 @@ class TestMonitor < Test::Unit::TestCase
     assert_join_threads([th, th2])
   end
 
+  def test_try_enter_second_after_killed_thread
+    th = Thread.start {
+      assert_equal(true, @monitor.try_enter)
+      Thread.current.kill
+      @monitor.exit
+    }
+    th.join
+    assert_equal(true, @monitor.try_enter)
+    @monitor.exit
+    th2 = Thread.start {
+      assert_equal(true, @monitor.try_enter)
+      @monitor.exit
+    }
+    assert_join_threads([th, th2])
+  end
+
   def test_cond
     cond = @monitor.new_cond