From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754430Ab0AYRPB (ORCPT ); Mon, 25 Jan 2010 12:15:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754421Ab0AYRO7 (ORCPT ); Mon, 25 Jan 2010 12:14:59 -0500 Received: from mail-pw0-f42.google.com ([209.85.160.42]:34739 "EHLO mail-pw0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754290Ab0AYRO6 (ORCPT ); Mon, 25 Jan 2010 12:14:58 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:content-transfer-encoding :in-reply-to:user-agent; b=TnAX7BhpSgZJSFPJwl22lv8478PP2RHvmRsn+/XMAyn4Gfa/m2FBExCd5y2btLHMvE Xw8H/7GJQIcWdYjhORO5khdc4Hv73I9gkb7whTx2UwiwNQMwlaa9D/MJ+/0jzqt6Sz9a xsYaIe56VmDYi05elLLASJ8nFmkxHNtJLEA2Q= Date: Mon, 25 Jan 2010 09:14:39 -0800 From: Dmitry Torokhov To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Greg KH , linux-kernel@vger.kernel.org Subject: Re: [PATCH] platform_driver_register: warn if probe is in .init.text Message-ID: <20100125171439.GA27387@core.coreip.homeip.net> References: <20100122173846.GA11057@suse.de> <1264189758-7197-1-git-send-email-u.kleine-koenig@pengutronix.de> <20100122234936.GA14538@core.coreip.homeip.net> <20100123094916.GA24949@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20100123094916.GA24949@pengutronix.de> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 23, 2010 at 10:49:16AM +0100, Uwe Kleine-König wrote: > Helle Dmitry, > > On Fri, Jan 22, 2010 at 03:49:37PM -0800, Dmitry Torokhov wrote: > > On Fri, Jan 22, 2010 at 08:49:18PM +0100, Uwe Kleine-König wrote: > > > +int platform_driver_register(struct platform_driver *drv) > > > +{ > > > + int ret = __platform_driver_register(drv); > > > + > > > +#if defined(CONFIG_HOTPLUG) > > > + /* > > > + * drivers that are registered by platform_driver_register > > > + * should not have their probe function in .init.text. The > > > + * reason is that a probe can happen after .init.text is > > > + * discarded which then results in an oops. The alternatives > > > + * are using .devinit.text for the probe function or "register" > > > + * with platform_driver_probe. > > > + */ > > > > > > What about CONFIG_MODULE case (without hotplug)? The driver may be > > compiled in (and thus probe will be discarded) but device might be > > created by a loadable module which is loaded later. > I don't see the problem here. You are right, without hotplug we don't try to bind to devices that come in later so we are safe to discard probe. > If the driver is registered using > platform_driver_register and the probe function lives in .init.text it > doesn't matter where the device comes from. If there is one you can > unbind and bind at a later time when .init is already discarded. No? > Yes. > More general, using platform_driver_register the pointer to the probe > function have to stay valid as it is saved for later use, so it must not > be an .init pointer. > > > > + if (drv->probe && kernel_init_text_address((unsigned long)drv->probe)) > > > + pr_warning("oops-warning: probe function of platform driver %s" > > > + " lives in .init.text\n", drv->driver.name); > > > +#else > > > + /* > > > + * without HOTPLUG probe functions can be discarded after the driver is > > > + * loaded. > > > + * There is a little chance for false positives, namely if the driver is > > > + * registered after the .init sections are discarded. > > > + */ > > > + if (drv->probe && !kernel_init_text_address((unsigned long)drv->probe)) > > > + pr_info("probably the probe function of platform driver %s can" > > > + " be moved to .init.text\n", drv->driver.name); > > > > It really depends on the user's (or rather builder's) local > > configuration so how can we make this suggestion? > Can you point out a situation that makes the suggestion wrong? AFAIK > there only the possibility that the driver is loaded after .init is > discarded (as written in the comment). > The presence of CONFIG_HOTPLUG depends on particular .config, so, for example, you may not have it set while I have. So you will boot, get the suggestion, submit a patch, then I will boot and will get a warning that the probe function is in wrong section. So in general I wonder if it is possible to request that all probe functions are marked as __devinit or not marked at all, regardless of CONFIG_HOTPLUG and CONFIG_MODULE settings. -- Dmitry