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Re: [Xen-devel] [PATCH] xen/sched: fix onlining cpu with core scheduling active

On 03.03.20 17:04, Jürgen Groß wrote:
On 03.03.20 14:31, Jan Beulich wrote:
On 03.03.2020 13:27, Juergen Gross wrote:
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -616,7 +616,8 @@ static int cpupool_cpu_add(unsigned int cpu)
      get_sched_res(cpu)->cpupool = NULL;
      cpus = sched_get_opt_cpumask(cpupool0->gran, cpu);
-    if ( cpumask_subset(cpus, &cpupool_free_cpus) )
+    if ( cpumask_subset(cpus, &cpupool_free_cpus) &&
+         cpumask_weight(cpus) >= cpupool_get_granularity(cpupool0) )

Why >= , not == ? And is the other part of the condition needed?

I can switch to ==.

Isn't this rather a condition that could be ASSERT()ed, as CPUs
shouldn't move out of the "free" set before reaching the

Probably, yes. I'll give it some testing and change it in the case
of (expected) success.

Thinking more about it I'm inclined to keep testing both conditions.
In case we are supporting cpupools with different granularities we'll
need to test for all cpus to be free in case the other sibling has been
moved to a cpupool with gran=1 already.


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