Messages in this thread | | | Date | Fri, 15 Mar 2013 14:46:32 +0100 | From | Oleg Nesterov <> | Subject | Re: + atomic-improve-atomic_inc_unless_negative-atomic_dec_unless_positive .patch added to -mm tree |
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On 03/15, Ming Lei wrote: > > On Fri, Mar 15, 2013 at 12:24 AM, Oleg Nesterov <oleg@redhat.com> 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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