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SubjectRe: [RFC] [PATCH] Pre-emption control for userspace
On Thu, Mar 06, 2014 at 02:45:00PM +0100, Rasmus Villemoes wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
>
> > On Thu, Mar 06, 2014 at 02:24:43PM +0100, Rasmus Villemoes wrote:
> >> Is it possible to implement non-sleeping versions of {get,put}_user()?
> >
> > __{get,put}_user()
>
> Huh?
>
> arch/x86/include/asm/uaccess.h:
>
> /**
> * __get_user: - Get a simple variable from user space, with less checking.
> * @x: Variable to store result.
> * @ptr: Source address, in user space.
> *
> * Context: User context only. This function may sleep.
>
> What am I missing?

__get_user() -> __get_user_nocheck() -> __get_user_size() -> __get_user_asm()

And __get_user_asm() seems to generate the required .fixup section for
this to work in pagefault_disable() context.


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