Re: [Xen-devel] [PATCH] Avoid panic when adjusting sedf parameters

[Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>]

On 11/17/2011 02:52 PM, Keir Fraser wrote:
> On 17/11/2011 13:30, "Jan Beulich"<JBeulich@xxxxxxxx>  wrote:
>
> > which would now associate the else with the wrong (inner) if. One
> > possible solution that comes to mind would be
> >
> > #define for_each_domain_in_cpupool(_d,_c) \
> >      for_each_domain_in_cpupool (_d) \
> >          if ((_d)->cpupool != (_c)) \
> >              continue; \
> >          else
> >
> > but I think I had seen a more clever solution to this problem, but cannot
> > remember/locate it right now.
> Given the gcc ({}) construction, you could do a double-loop:
>   for ( (_d) = rcu_dereference(domain_list);     \
>         (_d) != NULL;                            \
>         ({ while ((_d) = rcu_dereference((_d)->next_in_list != NULL)
>               if ((_d)->cpupool == (_c)) break;
>            (_d); }) )
>
> A bit ugly. ;-) And I still worry about cpupool locking...
What about:

static inline struct domain *next_domain_in_cpupool(
    struct domain *d, struct cpupool *c)
{
    for (d = rcu_dereference(d->next_in_list); d && d->cpupool != c;
         d = rcu_dereference(d->next_in_list));
    return d;
}

#define for_each_domain_in_cpupool(_d,_c)       \
 for ( (_d) = rcu_dereference(domain_list);     \
       (_d) != NULL;                            \
       (_d) = next_domain_in_cpupool((_d), (_c)))


Juergen

--
Juergen Gross                 Principal Developer Operating Systems
PDG ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@xxxxxxxxxxxxxx
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D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html


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