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Re: [Xen-devel] [PATCH] Avoid panic when adjusting sedf parameters
- To: Jan Beulich <JBeulich@xxxxxxxx>
- From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
- Date: Thu, 17 Nov 2011 15:41:11 +0100
- Cc: Keir Fraser <keir.xen@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 17 Nov 2011 14:43:56 +0000
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On 11/17/2011 03:32 PM, Jan Beulich wrote:
On 17.11.11 at 15:04, Juergen Gross<juergen.gross@xxxxxxxxxxxxxx> wrote:
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)))
Same problem as with Keir's variant - you'd enter the loop body for
the first domain on the list regardless of its cpupool. But with a
first_domain_in_cpupool() counterpart this might be usable. Or, as
said in the other reply, putting a more complex construct in the
middle clause.
I think adding first_domain_in_cpupool() is a good way to go.
Sending out adjusted patch with appropriate locking added in
cpupool_unassign_cpu() soon.
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
Domagkstr. 28 Internet: ts.fujitsu.com
D-80807 Muenchen Company details: ts.fujitsu.com/imprint.html
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