On Thu, 2003-06-12 at 16:34, Patrick Mochel wrote:
> > Nice thinking. It is a shame we need a lock for this, but we don't
> > have an atomic_inc_and_return().
>
> Those were my sentiments exactly:
Heh.
> +static inline int atomic_inc_and_read(atomic_t *v)
> +{
> + __asm__ __volatile__(
> + LOCK "incl %0"
> + :"=m" (v->counter)
> + :"m" (v->counter));
> + return v->counter;
> +}
What prevents a race between the increment and the return (i.e. you
return v->counter after another person also increments it)? Only the
increment is guaranteed atomic.
I think you need to copy the result of the increment into a local
variable _inside_ of the LOCK and return that. Whether or not that will
work sanely on all architectures I dunno.
Robert Love
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This archive was generated by hypermail 2b29 : Sun Jun 15 2003 - 22:00:35 EST