linux-kernel - [RFC PATCH v2 1/2] regulator: core: Consistently set mutex_owner when using ww_mutex_lock

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Message-Id: <20230329143317.RFC.v2.1.I4e9d433ea26360c06dd1381d091c82bb1a4ce843@changeid>
Date:   Wed, 29 Mar 2023 14:33:53 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Dmitry Osipenko <digetx@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        David Collins <quic_collinsd@...cinc.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [RFC PATCH v2 1/2] regulator: core: Consistently set mutex_owner when using ww_mutex_lock_slow()

When a codepath locks a rdev using ww_mutex_lock_slow() directly then
that codepath is responsible for incrementing the "ref_cnt" and also
setting the "mutex_owner" to "current".

The regulator core consistently got that right for "ref_cnt" but
didn't always get it right for "mutex_owner". Let's fix this.

It's unlikely that this truly matters because the "mutex_owner" is
only needed if we're going to do subsequent locking of the same
rdev. However, even though it's not truly needed it seems less
surprising if we consistently set "mutex_owner" properly.

Fixes: f8702f9e4aa7 ("regulator: core: Use ww_mutex for regulators locking")
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

Changes in v2:
- "Consistently set mutex_owner when using ww_mutex_lock_slow()" new for v2.

 drivers/regulator/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 1490eb40c973..9a13240f3084 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -334,6 +334,7 @@ static void regulator_lock_dependent(struct regulator_dev *rdev,
 			ww_mutex_lock_slow(&new_contended_rdev->mutex, ww_ctx);
 			old_contended_rdev = new_contended_rdev;
 			old_contended_rdev->ref_cnt++;
+			old_contended_rdev->mutex_owner = current;
 		}
 
 		err = regulator_lock_recursive(rdev,
@@ -6048,6 +6049,7 @@ static void regulator_summary_lock(struct ww_acquire_ctx *ww_ctx)
 			ww_mutex_lock_slow(&new_contended_rdev->mutex, ww_ctx);
 			old_contended_rdev = new_contended_rdev;
 			old_contended_rdev->ref_cnt++;
+			old_contended_rdev->mutex_owner = current;
 		}
 
 		err = regulator_summary_lock_all(ww_ctx,
-- 
2.40.0.348.gf938b09366-goog