sched/core: WARN() when migrating to an offline CPU

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

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170907150614.094206976@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 136a76d80dbf6e6cfeb19a0b75a43f420b4789e6..18a6966567daf30517a9f832e4a88b20ae705401 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1173,6 +1173,10 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
        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);