Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753632AbaDYNyh (ORCPT ); Fri, 25 Apr 2014 09:54:37 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:42501 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753438AbaDYNye (ORCPT ); Fri, 25 Apr 2014 09:54:34 -0400 Date: Fri, 25 Apr 2014 09:54:33 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Li Zhong cc: Tejun Heo , Johan Hovold , Greg Kroah-Hartman , , , Subject: Re: [PATCH] USB: serial: fix sysfs-attribute removal deadlock In-Reply-To: <1398392134.2805.149.camel@ThinkPad-T5421.cn.ibm.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 25 Apr 2014, Li Zhong wrote: > > I don't get why try_module_get() matters here. We can't call into > > ->store if the object at hand is already destroyed and the underlying > > module can't go away if the target device is still alive. > > try_module_get() doesn't actually protect the object. Why does that > > matter? This is self removal, right? Can you please take a look at > > kernfs_remove_self()? > > This is about one process writing something to driver attributes, and > one process trying to unload this driver. > > I think try_module_get() could detect whether the driver is being > unloaded, and if not, prevent it from being unloaded, so it could > protect the object here by not allow the driver to be unloaded. That isn't how try_module_get() works. If the module is being unloaded, try_module_get() simply fails. It does not prevent the module from being unloaded -- that's why its name begins with "try". Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/