Subject: [PATCH 01/10] sched: Trigger warning if ->migration_disabled counter underflows.
From: Sebastian Andrzej Siewior <[email-masked]>
Date: Thu, 12 Aug 2021 14:40:05 +0200

If migrate_enable() is used more often than its counter part then it
remains undetected and rq::nr_pinned will underflow, too.

Add a warning if migrate_enable() is attempted if without a matching a
migrate_disable().

Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
---
 kernel/sched/core.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2152,6 +2152,8 @@ void migrate_enable(void)
 	if (p->migration_disabled > 1) {
 		p->migration_disabled--;
 		return;
+	} else if (WARN_ON_ONCE(p->migration_disabled == 0)) {
+		return;
 	}
 
 	/*