linux-kernel - [PATCH v2 7/7] regulator/core: regulator_lock

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Date:   Wed, 30 Aug 2023 19:35:33 +0200
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 7/7] regulator/core: regulator_lock_two: remove duplicate
 locking code

Make regulator_lock_two() shorter by observing that we have only two
locks and when swapped earlier the retry code becomes identical to the
normal (optimistic) path.

Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
---
 drivers/regulator/core.c | 30 +++++++++-------------------
 1 file changed, 11 insertions(+), 19 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 3f9621621da9..36cec3fbcdea 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -216,37 +216,29 @@ static int regulator_lock_two(struct regulator_dev *rdev1,
 			      struct regulator_dev *rdev2,
 			      struct ww_acquire_ctx *ww_ctx)
 {
-	struct regulator_dev *held, *contended;
 	int ret;
 
 	ww_acquire_init(ww_ctx, &regulator_ww_class);
 
-	/* Try to just grab both of them */
 	ret = regulator_lock_nested(rdev1, ww_ctx);
 	if (WARN_ON(ret))
 		goto exit;
-	ret = regulator_lock_nested(rdev2, ww_ctx);
-	if (!ret)
-		goto exit;
-	if (WARN_ON(ret != -EDEADLOCK)) {
-		regulator_unlock(rdev1);
-		goto exit;
-	}
 
-	held = rdev1;
-	contended = rdev2;
 	while (true) {
-		regulator_unlock(held);
+		ret = regulator_lock_nested(rdev2, ww_ctx);
+		if (!ret)
+			break;
 
-		regulator_lock_contended(contended, ww_ctx);
-		swap(held, contended);
-		ret = regulator_lock_nested(contended, ww_ctx);
+		regulator_unlock(rdev1);
 
-		if (ret != -EDEADLOCK) {
-			if (WARN_ON(ret))
-				regulator_unlock(held);
+		if (WARN_ON(ret != -EDEADLOCK))
 			break;
-		}
+
+		/* Swap the locking order and retry. */
+
+		swap(rdev1, rdev2);
+
+		regulator_lock_contended(rdev1, ww_ctx);
 	}
 
 exit:
-- 
2.39.2