linux-kernel - [PATCH 6/6] regulator: core: simplify lock

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Message-Id: <682e260d8cb75c34f79ff7fcc3c4bb8586140cc4.1692484240.git.mirq-linux@rere.qmqm.pl>
Date:   Sun, 20 Aug 2023 00:46:11 +0200
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Dmitry Osipenko <digetx@...il.com>,
        Douglas Anderson <dianders@...omium.org>
Subject: [PATCH 6/6] regulator: core: simplify lock_two()

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 | 28 ++++++++++------------------
 1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index d8c2277cea36..9736507b62ff 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -201,37 +201,29 @@ 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)
-		return 0;
-	if (WARN_ON(ret != -EDEADLOCK)) {
-		regulator_unlock(rdev1);
-		goto exit;
-	}
 
-	held = rdev1;
-	contended = rdev2;
 	while (true) {
-		regulator_unlock(held);
-
-		ww_mutex_lock_slow(&contended->mutex, ww_ctx);
-		contended->ref_cnt++;
-		contended->mutex_owner = current;
-		swap(held, contended);
-		ret = regulator_lock_nested(contended, ww_ctx);
+		ret = regulator_lock_nested(rdev2, ww_ctx);
 		if (!ret)
 			return 0;
+
+		regulator_unlock(rdev1);
+
 		if (WARN_ON(ret != -EDEADLOCK))
 			break;
+
+		swap(rdev1, rdev2);
+
+		ww_mutex_lock_slow(&rdev1->mutex, ww_ctx);
+		rdev1->ref_cnt++;
+		rdev1->mutex_owner = current;
 	}
 
 exit:
-- 
2.39.2