Re: +atomic-improve-atomic_inc_unless_negative-atomic_dec_unless_positive.patch added to -mm tree

[Oleg Nesterov]

On 03/15, Ming Lei wrote:
>
> On Fri, Mar 15, 2013 at 12:24 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> >  static inline int atomic_inc_unless_negative(atomic_t *p)
> >  {
> >         int v, v1;
> > -       for (v = 0; v >= 0; v = v1) {
> > +       for (v = atomic_read(p); v >= 0; v = v1) {
> >                 v1 = atomic_cmpxchg(p, v, v + 1);
>
> Unfortunately, the above will exchange the current value even though
> it is negative, so it isn't correct.

Hmm, why? We always check "v >= 0" before we try to do
atomic_cmpxchg(old => v) ?

Oleg.

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