Keith Owens wrote:
>
> Sigh. Why do you always spot the typos *after* pressing send?
>
> On Thu, 29 Mar 2001 00:07:02 +1000,
> Keith Owens <[EMAIL PROTECTED]> wrote:
> > copy_desired_counter_values()
> > {
> > volatile int *p_flag = /* address of flag for desired cpu */;
> > volatile __s64 *p_counter = /* address of counter for desired cpu and instance
>*/;
> > __s64 counter; /* local copy */
> >
> > do {
> > counter = *p_counter;
> > } while (!*p_flag && counter == *p_counter);
> > }
>
> Should be while (*p_flag || counter != *p_counter);
And here you've the race:
kernel: user:
++flag;
wmb();
counter += delta; (first 32 bits)
counter = *p_counter;
counter += delta; (last 32 bits)
wmb();
--flag;
wmb();
... *p_flag test
++flag;
counter += delta; (first 32 bits)
counter == *p_counter test
counter += delta; (last 32 bits)
wmb();
--flag;
wmb();
Improbable but theoretically possible.
--
Abramo Bagnara mailto:[EMAIL PROTECTED]
Opera Unica Phone: +39.546.656023
Via Emilia Interna, 140
48014 Castel Bolognese (RA) - Italy
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sponsored by SuSE Linux http://www.suse.com
It sounds good!
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