[PATCH 01/11] sched: Trigger warning if ->migration_disabled counter underflows.

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: Ben Segall <bsegall@google.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>, Mel Gorman <mgorman@suse.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Waiman Long <longman@redhat.com>, Will Deacon <will@kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: [PATCH 01/11] sched: Trigger warning if ->migration_disabled counter underflows.
Date: Mon, 29 Nov 2021 18:46:44 +0100	[thread overview]
Message-ID: <20211129174654.668506-2-bigeasy@linutronix.de> (raw)
In-Reply-To: <20211129174654.668506-1-bigeasy@linutronix.de>

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@linutronix.de>
---
 kernel/sched/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 76f9deeaa9420..02be3f6144e97 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2171,6 +2171,8 @@ void migrate_enable(void)
 	if (p->migration_disabled > 1) {
 		p->migration_disabled--;
 		return;
+	} else if (WARN_ON_ONCE(p->migration_disabled == 0)) {
+		return;
 	}
 
 	/*
-- 
2.34.0

