Revert r64441

* This reverts commit 647fc1227a:
  "thread_sync.c (rb_mutex_synchronize): only unlock if we own the mutex"
* Let's try to preserve the semantics of always being locked inside
  Mutex#synchronize, even if an exception interrupts ConditionVariable#wait.
* As discussed on [Bug #14999].

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64448 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/ruby/library/conditionvariable/wait_spec.rb

@@ -23,15 +23,21 @@ describe "ConditionVariable#wait" do
     th.join
   end
 
-  it "the lock remains usable even if the thread is killed" do
+  it "reacquires the lock even if the thread is killed" do
     m = Mutex.new
     cv = ConditionVariable.new
     in_synchronize = false
+    owned = nil
 
     th = Thread.new do
       m.synchronize do
         in_synchronize = true
-        cv.wait(m)
+        begin
+          cv.wait(m)
+        ensure
+          owned = m.owned?
+          $stderr.puts "\nThe Thread doesn't own the Mutex!" unless owned
+        end
       end
     end
 
@@ -43,19 +49,24 @@ describe "ConditionVariable#wait" do
     th.kill
     th.join
 
-    m.try_lock.should == true
-    m.unlock
+    owned.should == true
   end
 
-  it "lock remains usable even if the thread is killed after being signaled" do
+  it "reacquires the lock even if the thread is killed after being signaled" do
     m = Mutex.new
     cv = ConditionVariable.new
     in_synchronize = false
+    owned = nil
 
     th = Thread.new do
       m.synchronize do
         in_synchronize = true
-        cv.wait(m)
+        begin
+          cv.wait(m)
+        ensure
+          owned = m.owned?
+          $stderr.puts "\nThe Thread doesn't own the Mutex!" unless owned
+        end
       end
     end
 
@@ -73,8 +84,7 @@ describe "ConditionVariable#wait" do
     }
 
     th.join
-    m.try_lock.should == true
-    m.unlock
+    owned.should == true
   end
 
   it "supports multiple Threads waiting on the same ConditionVariable and Mutex" do