linux-kernel - [PATCH] opp: Reduce the size of critical section in _opp_table_kref

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Date:   Tue, 27 Oct 2020 13:27:06 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Rob Clark <robdclark@...il.com>,
        Dmitry Osipenko <digetx@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] opp: Reduce the size of critical section in _opp_table_kref_release()

There is a lot of stuff here which can be done outside of the big
opp_table_lock, do that. This helps avoiding few circular dependency
lockdeps around debugfs and interconnects.

Reported-by: Rob Clark <robdclark@...il.com>
Reported-by: Dmitry Osipenko <digetx@...il.com>
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
Rob: I know this only fixes the issue partially for you and I am still
looking into that. I just wanted to get this merged in early as this
fixes lockdep for other users as well.

 drivers/opp/core.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 4ac4e7ce6b8b..0e0a5269dc82 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1181,6 +1181,10 @@ static void _opp_table_kref_release(struct kref *kref)
 	struct opp_device *opp_dev, *temp;
 	int i;
 
+	/* Drop the lock as soon as we can */
+	list_del(&opp_table->node);
+	mutex_unlock(&opp_table_lock);
+
 	_of_clear_opp_table(opp_table);
 
 	/* Release clk */
@@ -1208,10 +1212,7 @@ static void _opp_table_kref_release(struct kref *kref)
 
 	mutex_destroy(&opp_table->genpd_virt_dev_lock);
 	mutex_destroy(&opp_table->lock);
-	list_del(&opp_table->node);
 	kfree(opp_table);
-
-	mutex_unlock(&opp_table_lock);
 }
 
 void dev_pm_opp_put_opp_table(struct opp_table *opp_table)
-- 
2.25.0.rc1.19.g042ed3e048af