From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751034AbWJBJY2 (ORCPT ); Mon, 2 Oct 2006 05:24:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751038AbWJBJY2 (ORCPT ); Mon, 2 Oct 2006 05:24:28 -0400 Received: from crystal.sipsolutions.net ([195.210.38.204]:24024 "EHLO sipsolutions.net") by vger.kernel.org with ESMTP id S1751020AbWJBJY2 (ORCPT ); Mon, 2 Oct 2006 05:24:28 -0400 Subject: debugfs oddity From: Johannes Berg To: Greg KH , Takashi Iwai , linux-kernel , Joel Becker , Michael Buesch Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Mon, 02 Oct 2006 11:25:04 +0200 Message-Id: <1159781104.2655.47.camel@ux156> Mime-Version: 1.0 X-Mailer: Evolution 2.7.92 X-sips-origin: local Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Recently, I observed (in bcm43xx) that debugfs seems to keep things alive when userspace still has a directory open. Consider the following sequence of events: (a) kernel code creates a directory in debugfs (b) user changes current directory to that (c) kernel code removes that directory in debugfs Now, consider the equivalent sequence in a regular filesystem (or tmpfs): (a') user creates directory (b') user cd's into it (c') user deletes directory from a different shell The same thing should happen, in both cases the directory is kept around in a way until the process that has the current dir in the dead directory gives it up. Now, however, consider (d') user creates directory with the same name This works fine, and the old process sees nothing that happens in the new directory, as expected. However, (d) kernel code tries to create a debugfs directory with the same name does not work at all. Is this expected behaviour? It seems that once a driver requested that a directory is removed it can rightfully expect to be able to recreate it afterwards even if there's still the need to keep it lingering around for a bit. Similar things can probably happen when attributes are kept open, but I haven't tested this. I have also not tested sysfs or configfs. johannes