Re: [PATCH] Make futex waiters take an mm or inode reference

[Linus Torvalds]

On Mon, 8 Sep 2003, Jamie Lokier wrote:
> 
> This patch makes each futex waiter hold a reference to the mm or inode
> that a futex is keyed on.

I get the inode part, but let's think about the mm part a bit more.

In particular, passing off a futex that points to private memory to
somebody else just _doesn't_work_. It's insane. So I'd suggest saying that
an anonymous futex is only an <address,offset> pair, and drop the "mm"  
entirely. Let's make an anonymous futex _really_ anonymous, and document
that it's only an "address" - passing it off via UNIX domain sockets is
fine, it just doesn't do anything useful.

So is there any reason to really having "private.mm" AT ALL? From what I
can tell, it is not actually ever used (all "mm" users are "current->mm"),
so I don't see the point of incrementing a count for it either.

Or did I miss something?

			Linus

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