[PATCH 3/4] sched: WARN when migrating to an offline CPU

[Peter Zijlstra]

Migrating tasks to offline CPUs is a pretty big fail, warn about it.

Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
 kernel/sched/core.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1173,6 +1173,10 @@ void set_task_cpu(struct task_struct *p,
        WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
                                      lockdep_is_held(&task_rq(p)->lock)));
 #endif
+       /*
+        * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
+        */
+       WARN_ON_ONCE(!cpu_online(new_cpu));
 #endif
 
        trace_sched_migrate_task(p, new_cpu);