Re: [PATCH v3 04/11] tpm: Provide strong locking for device removal

[Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

On Mon, Feb 22, 2016 at 03:20:17PM -0700, Jason Gunthorpe wrote:
> > I'm just thinking is the try_module_get() and module_put() even
> > necessary after this change? You know that device is not unregistered
> > from chip->ops field, which is protected by that RW-semaphore.
> 
> The module locking is not about correctness. Some subsystems will hold
> the module lock on their driver specifically to prevent rmmod as a
> hint to the user that the driver module is being used by an open
> /dev/tpmX for instance. Eg rtc does that.
> 
> We need to decide if we want that for TPM or not. Orthogonal issue.
> 
> I'm OK with getting rid of the module lock, TPM has a long lived
> user space daemon, rtc does not.

You might want to use TPM without a daemon on small embedded devices
but on the other hand in these use cases the environment is fairly
well controlled. I'm not sure which side to take.

> Jason

/Jarkko

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