From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <juergen.gross@ts.fujitsu.com>
Subject: Re: [PATCH] Avoid panic when adjusting sedf parameters
Date: Thu, 17 Nov 2011 15:04:57 +0100
Message-ID: <4EC51489.4090609@ts.fujitsu.com>
References: <CAEAC230.25135%keir.xen@gmail.com>
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To: Keir Fraser <keir.xen@gmail.com>
Cc: xen-devel@lists.xensource.com, Jan Beulich <JBeulich@suse.com>
List-Id: xen-devel@lists.xenproject.org

On 11/17/2011 02:52 PM, Keir Fraser wrote:
> On 17/11/2011 13:30, "Jan Beulich"<JBeulich@suse.com>  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@ts.fujitsu.com
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html