xen: credit1: fix mask to be used for tickling in Credit1

If there are idle pcpus inside the waking vcpu's
soft-affinity mask, we should really tickle one
of them (this is one of the purposes of the
__runq_tickle() function itself!), not just
any idle pcpu.

The issue has been introduced in 02ea503182
("credit1: properly deal with pCPUs not in any cpupool"),
where the usage of idle_mask is changed, without
updating the bottom of the function, where it
is also referenced.

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>

xen/common/sched_credit.c

@@ -463,11 +463,12 @@ static inline void __runq_tickle(struct csched_vcpu *new)
                 if ( opt_tickle_one_idle )
                 {
                     this_cpu(last_tickle_cpu) =
-                        cpumask_cycle(this_cpu(last_tickle_cpu), &idle_mask);
+                        cpumask_cycle(this_cpu(last_tickle_cpu),
+                                      cpumask_scratch_cpu(cpu));
                     __cpumask_set_cpu(this_cpu(last_tickle_cpu), &mask);
                 }
                 else
-                    cpumask_or(&mask, &mask, &idle_mask);
+                    cpumask_or(&mask, &mask, cpumask_scratch_cpu(cpu));
             }
 
             /* Did we find anyone? */