check thread deadness correctly.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57595 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_thread.rb

@@ -1160,4 +1160,14 @@ q.pop
     c = Class.new(Thread) {def initialize() self.name = "foo"; super; end}
     assert_equal("foo", c.new {Thread.current.name}.value, bug12290)
   end
+
+  def test_thread_interrupt_for_killed_thread
+    assert_normal_exit(<<-_end, '[Bug #8996]', timeout: 5, timeout_error: nil)
+      trap(:TERM){exit}
+      while true
+        t = Thread.new{sleep 0}
+        t.raise Interrupt
+      end
+    _end
+  end
 end

thread.c

@@ -2107,6 +2107,13 @@ rb_threadptr_raise(rb_thread_t *th, int argc, VALUE *argv)
     else {
 	exc = rb_make_exception(argc, argv);
     }
+
+    /* making an exception object can switch thread,
+       so we need to check thread deadness again */
+    if (rb_threadptr_dead(th)) {
+	return Qnil;
+    }
+
     rb_threadptr_setup_exception(GET_THREAD(), exc, Qundef);
     rb_threadptr_pending_interrupt_enque(th, exc);
     rb_threadptr_interrupt(th);