[PATCH v2 2/8] regulator: core: fix locking in regulator_resolve_supply() error path

["André Draszik" <andre.draszik@linaro.org>]

If late enabling of a supply regulator fails in
regulator_resolve_supply(), the code currently triggers a lockdep
warning:

    WARNING: drivers/regulator/core.c:2649 at _regulator_put+0x80/0xa0, CPU#6: kworker/u32:4/596
    ...
    Call trace:
     _regulator_put+0x80/0xa0 (P)
     regulator_resolve_supply+0x7cc/0xbe0
     regulator_register_resolve_supply+0x28/0xb8

as the regulator_list_mutex must be held when calling _regulator_put().

To solve this, simply switch to using regulator_put().

While at it, we should also make sure that no concurrent access happens
to our rdev while we clear out the supply pointer. Add appropriate
locking to ensure that.

While the code in question will be removed altogether in a follow-up
commit, I believe it is still beneficial to have this corrected before
removal for future reference.

Fixes: 36a1f1b6ddc6 ("regulator: core: Fix memory leak in regulator_resolve_supply()")
Fixes: 8e5356a73604 ("regulator: core: Clear the supply pointer if enabling fails")
Signed-off-by: André Draszik <andre.draszik@linaro.org>
---
 drivers/regulator/core.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index a723bd00e1716c2c3899c63314c6249015698216..48c091de68d81e3e89eacecd8526255ab9a446b2 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2285,8 +2285,16 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 	if (rdev->use_count) {
 		ret = regulator_enable(rdev->supply);
 		if (ret < 0) {
-			_regulator_put(rdev->supply);
+			struct regulator *supply;
+
+			regulator_lock_two(rdev, rdev->supply->rdev, &ww_ctx);
+
+			supply = rdev->supply;
 			rdev->supply = NULL;
+
+			regulator_unlock_two(rdev, supply->rdev, &ww_ctx);
+
+			regulator_put(supply);
 			goto out;
 		}
 	}

-- 
2.52.0.457.g6b5491de43-goog