Re: [PATCH v3 01/29] asm-generic: add generic futex for !CONFIG_SMP

[Thomas Gleixner]

On Tue, 23 Sep 2014, LF.Tan wrote:
> On Mon, Sep 8, 2014 at 5:22 PM, Ley Foon Tan <lftan@xxxxxxxxxx> 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/