[tip: locking/core] sched: Trigger warning if ->migration_disabled counter underflows.

[tip-bot2 for Sebastian Andrzej Siewior]

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     9d0df37797453f168afdb2e6fd0353c73718ae9a
Gitweb:        https://git.kernel.org/tip/9d0df37797453f168afdb2e6fd0353c73718ae9a
Author:        Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
AuthorDate:    Mon, 29 Nov 2021 18:46:44 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Sat, 04 Dec 2021 10:56:22 +01:00

sched: Trigger warning if ->migration_disabled counter underflows.

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 <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20211129174654.668506-2-bigeasy@xxxxxxxxxxxxx
---
 kernel/sched/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3c9b0fd..300218a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2173,6 +2173,9 @@ void migrate_enable(void)
 		return;
 	}
 
+	if (WARN_ON_ONCE(!p->migration_disabled))
+		return;
+
 	/*
 	 * Ensure stop_task runs either before or after this, and that
 	 * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().