1 files changed, 33 insertions, 11 deletions

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index ca03d8e70bd1..67a768fe5b2a 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1813,13 +1813,13 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 {
 	struct regulator_dev *r;
 	struct device *dev = rdev->dev.parent;
-	int ret;
+	int ret = 0;
 
 	/* No supply to resolve? */
 	if (!rdev->supply_name)
 		return 0;
 
-	/* Supply already resolved? */
+	/* Supply already resolved? (fast-path without locking contention) */
 	if (rdev->supply)
 		return 0;
 
@@ -1829,7 +1829,7 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 
 		/* Did the lookup explicitly defer for us? */
 		if (ret == -EPROBE_DEFER)
-			return ret;
+			goto out;
 
 		if (have_full_constraints()) {
 			r = dummy_regulator_rdev;
@@ -1837,15 +1837,18 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 		} else {
 			dev_err(dev, "Failed to resolve %s-supply for %s\n",
 				rdev->supply_name, rdev->desc->name);
-			return -EPROBE_DEFER;
+			ret = -EPROBE_DEFER;
+			goto out;
 		}
 	}
 
 	if (r == rdev) {
 		dev_err(dev, "Supply for %s (%s) resolved to itself\n",
 			rdev->desc->name, rdev->supply_name);
-		if (!have_full_constraints())
-			return -EINVAL;
+		if (!have_full_constraints()) {
+			ret = -EINVAL;
+			goto out;
+		}
 		r = dummy_regulator_rdev;
 		get_device(&r->dev);
 	}
@@ -1859,7 +1862,8 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 	if (r->dev.parent && r->dev.parent != rdev->dev.parent) {
 		if (!device_is_bound(r->dev.parent)) {
 			put_device(&r->dev);
-			return -EPROBE_DEFER;
+			ret = -EPROBE_DEFER;
+			goto out;
 		}
 	}
 
@@ -1867,15 +1871,32 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 	ret = regulator_resolve_supply(r);
 	if (ret < 0) {
 		put_device(&r->dev);
-		return ret;
+		goto out;
+	}
+
+	/*
+	 * 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);
+		goto out;
 	}
 
 	ret = set_supply(rdev, r);
 	if (ret < 0) {
+		regulator_unlock(rdev);
 		put_device(&r->dev);
-		return ret;
+		goto out;
 	}
 
+	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
@@ -1886,11 +1907,12 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 		if (ret < 0) {
 			_regulator_put(rdev->supply);
 			rdev->supply = NULL;
-			return ret;
+			goto out;
 		}
 	}
 
-	return 0;
+out:
+	return ret;
 }
 
 /* Internal regulator request function */