Patch "regulator: Fix lockdep warning resolving supplies" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    regulator: Fix lockdep warning resolving supplies

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     regulator-fix-lockdep-warning-resolving-supplies.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit b5d4423f125c87cdc5c5df88e67dab91d091ba7a
Author: Mark Brown <broonie@xxxxxxxxxx>
Date:   Fri Jan 22 13:20:42 2021 +0000

    regulator: Fix lockdep warning resolving supplies
    
    [ Upstream commit 14a71d509ac809dcf56d7e3ca376b15d17bd0ddd ]
    
    With commit eaa7995c529b54 (regulator: core: avoid
    regulator_resolve_supply() race condition) we started holding the rdev
    lock while resolving supplies, an operation that requires holding the
    regulator_list_mutex. This results in lockdep warnings since in other
    places we take the list mutex then the mutex on an individual rdev.
    
    Since the goal is to make sure that we don't call set_supply() twice
    rather than a concern about the cost of resolution pull the rdev lock
    and check for duplicate resolution down to immediately before we do the
    set_supply() and drop it again once the allocation is done.
    
    Fixes: eaa7995c529b54 (regulator: core: avoid regulator_resolve_supply() race condition)
    Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
    Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
    Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20210122132042.10306-1-broonie@xxxxxxxxxx
    Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index b79ecf37e40f8..65e1cde13d59e 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1587,17 +1587,6 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 	if (rdev->supply)
 		return 0;
 
-	/*
-	 * 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 = regulator_dev_lookup(dev, rdev->supply_name);
 	if (IS_ERR(r)) {
 		ret = PTR_ERR(r);
@@ -1649,12 +1638,29 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 		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);
 		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
@@ -1670,7 +1676,6 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 	}
 
 out:
-	regulator_unlock(rdev);
 	return ret;
 }