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SubjectRe: [PATCH] unicore32 fix: remove arch-specific futex support
On Wed, 30 Mar 2011, Arnd Bergmann wrote:

> On Wednesday 30 March 2011, Guan Xuetao wrote:
> > The futex functions in unicore32 are not used and verified,
> > so just replaced by asm-generic version.
> >
> > Signed-off-by: Guan Xuetao <>
> Note that the a working futex implementation would be really useful
> to get efficient multithreaded applications. On uniprocessor
> machines, this can easily be done by disabling interrupts, like
> you also do for spinlock and atomic.
> I believe we could actually copy the arch/sh/include/asm/futex-irq.h
> implementation to include/asm-generic and use that whenever CONFIG_SMP
> is disabled. That would also help a lot of other architectures.

The problem is that you need cmpxchg in user space as well.

ARM does this with some syscall magic for machines which do not have


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