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
+        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
+        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

thread_sync.c

@@ -321,14 +321,21 @@ rb_mutex_owned_p(VALUE self)
     return owned;
 }
 
-static void
-mutex_do_unlock(rb_mutex_t *mutex, rb_thread_t *th)
+static const char *
+rb_mutex_unlock_th(rb_mutex_t *mutex, rb_thread_t *th)
 {
+    const char *err = NULL;
+
+    if (mutex->th == 0) {
+	err = "Attempt to unlock a mutex which is not locked";
+    }
+    else if (mutex->th != th) {
+	err = "Attempt to unlock a mutex which is locked by another thread";
+    }
+    else {
 	struct sync_waiter *cur = 0, *next = 0;
 	rb_mutex_t **th_mutex = &th->keeping_mutexes;
 
-    VM_ASSERT(mutex->th == th);
-
 	mutex->th = 0;
 	list_for_each_safe(&mutex->waitq, cur, next, node) {
 	    list_del_init(&cur->node);
@@ -351,21 +358,6 @@ mutex_do_unlock(rb_mutex_t *mutex, rb_thread_t *th)
 	}
 	*th_mutex = mutex->next_mutex;
 	mutex->next_mutex = NULL;
-}
-
-static const char *
-rb_mutex_unlock_th(rb_mutex_t *mutex, rb_thread_t *th)
-{
-    const char *err = NULL;
-
-    if (mutex->th == 0) {
-	err = "Attempt to unlock a mutex which is not locked";
-    }
-    else if (mutex->th != th) {
-	err = "Attempt to unlock a mutex which is locked by another thread";
-    }
-    else {
-        mutex_do_unlock(mutex, th);
     }
 
     return err;
@@ -505,20 +497,6 @@ mutex_sleep(int argc, VALUE *argv, VALUE self)
     return rb_mutex_sleep(self, timeout);
 }
 
-static VALUE
-mutex_unlock_if_owned(VALUE self)
-{
-    rb_thread_t *th = GET_THREAD();
-    rb_mutex_t *mutex;
-    GetMutexPtr(self, mutex);
-
-    /* we may not own the mutex if an exception occured */
-    if (mutex->th == th) {
-        mutex_do_unlock(mutex, th);
-    }
-    return Qfalse;
-}
-
 /*
  * call-seq:
  *    mutex.synchronize { ... }    -> result of the block
@@ -531,7 +509,7 @@ VALUE
 rb_mutex_synchronize(VALUE mutex, VALUE (*func)(VALUE arg), VALUE arg)
 {
     rb_mutex_lock(mutex);
-    return rb_ensure(func, arg, mutex_unlock_if_owned, mutex);
+    return rb_ensure(func, arg, rb_mutex_unlock, mutex);
 }
 
 /*