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Date:   Thu, 21 Jan 2021 15:44:18 +0000
From:   Mark Brown <broonie@kernel.org>
To:     Marek Szyprowski <m.szyprowski@samsung.com>
Cc:     David Collins <collinsd@codeaurora.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        'Linux Samsung SOC' <linux-samsung-soc@vger.kernel.org>
Subject: Re: [PATCH] regulator: core: avoid regulator_resolve_supply() race
 condition
Message-ID: <20210121154418.GE4588@sirena.org.uk>
References: <1610068562-4410-1-git-send-email-collinsd@codeaurora.org>
 <CGME20210112213419eucas1p24231e4d0ac11c31184f2f8f3f20cbd9d@eucas1p2.samsung.com>
 <e512ee85-7fa6-e5fe-eb30-f088bb83cf23@samsung.com>
 <20210118204958.GS4455@sirena.org.uk>
 <5f37ae96-c5f9-6619-d88f-21c5e483ff8e@samsung.com>
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On Thu, Jan 21, 2021 at 10:41:59AM +0100, Marek Szyprowski wrote:
> On 18.01.2021 21:49, Mark Brown wrote:

> > Does this help (completely untested):

> Sadly nope. I get same warning:

Try this instead:

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 3ae5ccd9277d..31503776dbd7 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1823,17 +1823,6 @@ static int regulator_resolve_supply(struct regulator=
_dev *rdev)
 	if (rdev->supply)
 		return 0;
=20
-	/*
-	 * Recheck rdev->supply with rdev->mutex lock held to avoid a race
-	 * between rdev->supply null check and setting rdev->supply in
-	 * set_supply() from concurrent tasks.
-	 */
-	regulator_lock(rdev);
-
-	/* Supply just resolved by a concurrent task? */
-	if (rdev->supply)
-		goto out;
-
 	r =3D regulator_dev_lookup(dev, rdev->supply_name);
 	if (IS_ERR(r)) {
 		ret =3D PTR_ERR(r);
@@ -1885,12 +1874,29 @@ static int regulator_resolve_supply(struct regulato=
r_dev *rdev)
 		goto out;
 	}
=20
+	/*
+	 * Recheck rdev->supply with rdev->mutex lock held to avoid a race
+	 * between rdev->supply null check and setting rdev->supply in
+	 * set_supply() from concurrent tasks.
+	 */
+	regulator_lock(rdev);
+
+	/* Supply just resolved by a concurrent task? */
+	if (rdev->supply) {
+		regulator_unlock(rdev);
+		put_device(&r->dev);
+		return ret;
+	}
+
 	ret =3D set_supply(rdev, r);
 	if (ret < 0) {
+		regulator_unlock(rdev);
 		put_device(&r->dev);
-		goto out;
+		return ret;
 	}
=20
+	regulator_unlock(rdev);
+
 	/*
 	 * In set_machine_constraints() we may have turned this regulator on
 	 * but we couldn't propagate to the supply if it hadn't been resolved
@@ -1901,12 +1907,11 @@ static int regulator_resolve_supply(struct regulato=
r_dev *rdev)
 		if (ret < 0) {
 			_regulator_put(rdev->supply);
 			rdev->supply =3D NULL;
-			goto out;
+			goto out_rdev_lock;
 		}
 	}
=20
 out:
-	regulator_unlock(rdev);
 	return ret;
 }
=20

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