thread.c: deadlock in backtrace

* thread.c (unblock_function_set): check interrupts just once
  during raising exceptions, as they are deferred since r16651.
  [ruby-core:85939] [Bug #14577]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62673 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_exception.rb

@@ -1200,6 +1200,28 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
     end;
   end
 
+  def test_blocking_backtrace
+    assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
+    begin;
+      class Bug < RuntimeError
+        def backtrace
+          IO.readlines(IO::NULL)
+        end
+      end
+      bug = Bug.new '[ruby-core:85939] [Bug #14577]'
+      n = 10000
+      i = 0
+      n.times do
+        begin
+          raise bug
+        rescue Bug
+          i += 1
+        end
+      end
+      assert_equal(n, i)
+    end;
+  end
+
   def test_wrong_backtrace
     assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
     begin;

thread.c

@@ -428,7 +428,7 @@ unblock_function_set(rb_thread_t *th, rb_unblock_function_t *func, void *arg, in
 	}
 
         rb_native_mutex_lock(&th->interrupt_lock);
-    } while (RUBY_VM_INTERRUPTED_ANY(th->ec) &&
+    } while (!th->ec->raised_flag && RUBY_VM_INTERRUPTED_ANY(th->ec) &&
              (rb_native_mutex_unlock(&th->interrupt_lock), TRUE));
 
     VM_ASSERT(th->unblock.func == NULL);