sched: Teach the forced-newidle balancer about CPU affinity limitation.

BugLink: https://bugs.launchpad.net/bugs/1969107
commit 386ef214c3c6ab111d05e1790e79475363abaa05 upstream.

try_steal_cookie() looks at task_struct::cpus_mask to decide if the
task could be moved to `this' CPU. It ignores that the task might be in
a migration disabled section while not on the CPU. In this case the task
must not be moved otherwise per-CPU assumption are broken.

Use is_cpu_allowed(), as suggested by Peter Zijlstra, to decide if the a
task can be moved.

Fixes: d2dfa17bc7de6 ("sched: Trivial forced-newidle balancer")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YjNK9El+3fzGmswf@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit ff6505766565616deb65a203e62d4ca63c6c277b)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 07515cef38fb6272205cad748e04960fa376d2f5..2abefdb511b27471659ce7f6ab078f9a9ef15ce1 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5927,7 +5927,7 @@ static bool try_steal_cookie(int this, int that)
                if (p == src->core_pick || p == src->curr)
                        goto next;
 
-               if (!cpumask_test_cpu(this, &p->cpus_mask))
+               if (!is_cpu_allowed(p, this))
                        goto next;
 
                if (p->core_occupation > dst->idle->core_occupation)