[PATCH v3 hmm 08/12] mm/hmm: Remove racy protection against double-unregistration

[Christoph Hellwig]

On Thu, Jun 13, 2019 at 09:44:46PM -0300, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg at mellanox.com>
> 
> No other register/unregister kernel API attempts to provide this kind of
> protection as it is inherently racy, so just drop it.
> 
> Callers should provide their own protection, it appears nouveau already
> does, but just in case drop a debugging POISON.

I don't even think we even need to bother with the POISON, normal list
debugging will already catch a double unregistration anyway.

Otherwise looks fine:

Reviewed-by: Christoph Hellwig <hch at lst.de>