Messages in this thread | | | Date | Thu, 10 Aug 2017 10:30:57 -0600 | From | Jason Gunthorpe <> | Subject | Re: [PATCH] Do not disable driver and bus shutdown hook when class shutdown hook is set. |
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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
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