Re: [PATCH/RFC] Futex mmap_sem deadlock

Arjan van de Ven
2005-02-23T17:37:21Z

On Wed, 2005-02-23 at 11:10 -0600, Olof Johansson wrote:
> On Wed, Feb 23, 2005 at 07:54:06AM -0800, Linus Torvalds wrote:
>
> > > Otherwise, a preempt attempt in get_user would not be seen
> > > until some future preempt_enable was executed.
> >
> > True. I guess we should have a "preempt_check_resched()" there too. That's
> > what "kunmap_atomic()" does too (which is what we rely on in the other
> > case we do this..)
>
> Ok, this is getting complex enough to warrant get_user_inatomic(),
> which means adding it to every arch's uaccess.h.
>
> Below patch does so. Unfortunately I don't have a Viro setup with cross
> compilers for nearly every arch, so I can't make sure it doesn't break
> anything. But since I pasted the same code everywhere it shouldn't.

I hate to do this to you, but get_user is a bit horrible in that it is
an untyped interface. Fixing it is hard (ugh) but when adding new
variants should/could we consider to please make it a typed (eg inline
and not a define) interface please ?