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Re: [PATCH/RFC] Futex mmap_sem deadlock

From:  Arjan van de Ven <arjan-AT-infradead.org>
To:  Olof Johansson <olof-AT-austin.ibm.com>
Subject:  Re: [PATCH/RFC] Futex mmap_sem deadlock
Date:  Wed, 23 Feb 2005 18:37:01 +0100
Cc:  Linus Torvalds <torvalds-AT-osdl.org>, Joe Korty <joe.korty-AT-ccur.com>, Jamie Lokier <jamie-AT-shareable.org>, Andrew Morton <akpm-AT-osdl.org>, linux-kernel-AT-vger.kernel.org, rusty-AT-rustcorp.com.au
Archive-link:  Article, Thread

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 ?




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