Re: [PATCH] Alternate futex non-page-pinning and COW fix
From: Jamie Lokier
Date: Thu Sep 04 2003 - 17:14:20 EST
Linus Torvalds wrote:
> > * A futex on a MAP_PRIVATE must be mm-local: the canonical
> > * example being MAP_PRIVATE of /dev/zero.
>
> Actually, /dev/zero is a special case in itself. It is an anonymous
> mapping, and is equivalent to MAP_ANON for private mappings. For
> MAP_SHARED it is something _totally_ different.
Well yes, but conceptually it's behaviour is that of a private mapping
of a file-like object. But fine, let's not get sidetracked by /dev/zero.
I'll restate it:
* A futex on a MAP_PRIVATE must be mm-local. The canonical
example being the data section of your executable.
> > Unfortunately I think the above 5 conditions do not have a consistent
> > solution. Please prove me wrong :)
>
> I don't think there is any inconsistency.
I can't think of a behaviour which satisfies all 5 conditions, so
you'll have to help me out. :/
-- Jamie
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