[Xen-changelog] [xen master] sched: fix onlining cpu with core scheduling active

[patchbot@xxxxxxx]

commit 4c7d340f75abc64f131b0f9bffd6d66d72e43528
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Tue Mar 24 17:36:44 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Mar 24 17:36:44 2020 +0100

    sched: fix onlining cpu with core scheduling active
    
    When onlining a cpu cpupool_cpu_add() checks whether all siblings of
    the new cpu are free in order to decide whether to add it to cpupool0.
    In case the added cpu is not the last sibling to be onlined this test
    is wrong as it only checks for all online siblings to be free. The
    test should include the check for the number of siblings having
    reached the scheduling granularity of cpupool0, too.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>
---
 xen/common/sched/cpupool.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index 9f70c7ec17..d40345b585 100644
--- 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) )
         ret = cpupool_assign_cpu_locked(cpupool0, cpu);
 
     rcu_read_unlock(&sched_res_rculock);
--
generated by git-patchbot for /home/xen/git/xen.git#master

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