From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH] Do not disable driver and bus shutdown hook when class shutdown hook is set. Date: Thu, 10 Aug 2017 10:30:57 -0600 Message-ID: <20170810163057.GA21485@obsidianresearch.com> References: <20170809213420.2391-1-msuchanek@suse.de> <20170809215202.GA21867@obsidianresearch.com> <20170810121811.2741dccc@kitsune.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <20170810121811.2741dccc@kitsune.suse.cz> Sender: linux-kernel-owner@vger.kernel.org To: Michal =?iso-8859-1?Q?Such=E1nek?= Cc: Greg Kroah-Hartman , Peter Huewe , Marcel Selhorst , Jarkko Sakkinen , linux-kernel@vger.kernel.org, tpmdd-devel@lists.sourceforge.net List-Id: tpmdd-devel@lists.sourceforge.net On Thu, Aug 10, 2017 at 12:18:11PM +0200, Michal Suchánek wrote: > > The bus disables the driver callback, on the expectation that the bus > > implementation will do it. > > Which is totally sound design not prone to errors. Well, I agree it isn't the easiest... > > Existing bus implementations do properly chain to driver shutdown (eg > > look at mmc_bus_shutdown) and it appears to have been written like > > Neither isa nor ibmebus does. These are two random buses I tried to > look at. I'm not following, I see this: static void ibmebus_bus_device_shutdown(struct device *dev) { struct platform_device *of_dev = to_platform_device(dev); struct platform_driver *drv = to_platform_driver(dev->driver); if (dev->driver && drv->shutdown) drv->shutdown(of_dev); } It looks to me like in this case the struct device_driver shutdown is not used, and instead the struct platform_driver shutdown is called. > > this so that the bus can insert code before and after calling the > > driver shutdown. > > So basically there is bus pre-shutdown and post-shutdown hook jumbled > together in one function. and a redirect, apparently. > While I can understand the concept of post-shutdown hook I wonder > what gross hack would require a pre-shutdown hook. TPM requires pre-shutdown. It fences off access to the TPM so the TPM can have a clean shutdown. We cannot do a clean TPM shutdown if there is a possibility of another transaction being send to the TPM. TPM's have non-volatile state and record if they were not shut down properly, so doing this is actually quite important. > The Linux development process at its best. There is poor design > implemented so when touching the code it is extended to worse because I'm not sure I completely agree, there is obviously a lot going on with bus->shutdown. If you want to go ahead with your patch then please also rename the class shutdown to shutdown_pre to make it clear it is doing something different. > it is smaller patch more likely to get past maintainers than fixing the > mess. Yes, this is probably true, the TPM fix needed to be back ported to -stable. Jason