sched/rt: Annotate the RT balancing logic irqwork as IRQ_WORK_HARD_IRQ

The push-IPI logic for RT tasks expects to be invoked from hardirq
context. One reason is that a RT task on the remote CPU would block the
softirq processing on PREEMPT_RT and so avoid pulling / balancing the RT
tasks as intended.

Annotate root_domain::rto_push_work as IRQ_WORK_HARD_IRQ.

Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: Sebastian Andrzej Siewior

kernel/sched/topology.c

@@ -526,7 +526,7 @@ static int init_rootdomain(struct root_domain *rd)
 #ifdef HAVE_RT_PUSH_IPI
 	rd->rto_cpu = -1;
 	raw_spin_lock_init(&rd->rto_lock);
-	init_irq_work(&rd->rto_push_work, rto_push_irq_work_func);
+	rd->rto_push_work = IRQ_WORK_INIT_HARD(rto_push_irq_work_func);
 #endif
 
 	rd->visit_gen = 0;