sched/fair: Add a few assertions

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.015639083@infradead.org

kernel/sched/fair.c

@@ -6288,6 +6288,11 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 		task_util = uclamp_task_util(p);
 	}
 
+	/*
+	 * per-cpu select_idle_mask usage
+	 */
+	lockdep_assert_irqs_disabled();
+
 	if ((available_idle_cpu(target) || sched_idle_cpu(target)) &&
 	    asym_fits_capacity(task_util, target))
 		return target;
@@ -6781,8 +6786,6 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
  * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
  *
  * Returns the target CPU number.
- *
- * preempt must be disabled.
  */
 static int
 select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
@@ -6795,6 +6798,10 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
 	/* SD_flags and WF_flags share the first nibble */
 	int sd_flag = wake_flags & 0xF;
 
+	/*
+	 * required for stable ->cpus_allowed
+	 */
+	lockdep_assert_held(&p->pi_lock);
 	if (wake_flags & WF_TTWU) {
 		record_wakee(p);