On Sat, Jun 15, 2019 at 07:16:12AM -0700, Christoph Hellwig wrote: > On Thu, Jun 13, 2019 at 09:44:46PM -0300, Jason Gunthorpe wrote: > > From: Jason Gunthorpe <jgg@xxxxxxxxxxxx> > > > > 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. mirror->hmm isn't a list so list debugging won't help. My concern when I wrote this was that one of the in flight patches I can't see might be depending on this double-unregister-is-safe behavior, so I wanted them to crash reliably. It is a really overly conservative thing to do.. Thanks, Jason
