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SubjectRe: [PATCH v3 01/29] asm-generic: add generic futex for !CONFIG_SMP
On Tue, 23 Sep 2014, LF.Tan wrote:
> On Mon, Sep 8, 2014 at 5:22 PM, Ley Foon Tan <lftan@altera.com> wrote:
> > Follow m68k futex implementation for !CONFIG_SMP.

Great. Follow arch/random implementation blindly and copy all the bugs
in it.

> > +static inline int
> > +futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
> > + u32 oldval, u32 newval)
> > +{
> > + u32 val;
> > +
> > + if (unlikely(get_user(val, uaddr) != 0))
> > + return -EFAULT;
> > +
> > + if (val == oldval && unlikely(put_user(newval, uaddr) != 0))
> > + return -EFAULT;
> > +
> > + *uval = val;
> > +
> > + return 0;
> > +}

Care to explain how this works reliably and resembles proper cmpxchg
semantics under all circumstances?

Thanks,

tglx


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