| From 877cef15978d35901dda7405fa1c5fea83e616d6 Mon Sep 17 00:00:00 2001 |
| From: Charles Keepax <ckeepax@opensource.cirrus.com> |
| Date: Thu, 4 Apr 2019 16:32:18 +0100 |
| Subject: regulator: core: Avoid potential deadlock on regulator_unregister |
| |
| [ Upstream commit 063773011d33bb36588a90385aa9eb75d13c6d80 ] |
| |
| Lockdep reports the following issue on my setup: |
| |
| Possible unsafe locking scenario: |
| |
| CPU0 CPU1 |
| ---- ---- |
| lock((work_completion)(&(&rdev->disable_work)->work)); |
| lock(regulator_list_mutex); |
| lock((work_completion)(&(&rdev->disable_work)->work)); |
| lock(regulator_list_mutex); |
| |
| The problem is that regulator_unregister takes the |
| regulator_list_mutex and then calls flush_work on disable_work. But |
| regulator_disable_work calls regulator_lock_dependent which will |
| also take the regulator_list_mutex. Resulting in a deadlock if the |
| flush_work call actually needs to flush the work. |
| |
| Fix this issue by moving the flush_work outside of the |
| regulator_list_mutex. The list mutex is not used to guard the point at |
| which the delayed work is queued, so its use adds no additional safety. |
| |
| Fixes: f8702f9e4aa7 ("regulator: core: Use ww_mutex for regulators locking") |
| Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com> |
| Reviewed-by: Dmitry Osipenko <digetx@gmail.com> |
| Signed-off-by: Mark Brown <broonie@kernel.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| drivers/regulator/core.c | 3 ++- |
| 1 file changed, 2 insertions(+), 1 deletion(-) |
| |
| diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c |
| index 6da41207e479a..35a7d020afecd 100644 |
| --- a/drivers/regulator/core.c |
| +++ b/drivers/regulator/core.c |
| @@ -5062,10 +5062,11 @@ void regulator_unregister(struct regulator_dev *rdev) |
| regulator_put(rdev->supply); |
| } |
| |
| + flush_work(&rdev->disable_work.work); |
| + |
| mutex_lock(®ulator_list_mutex); |
| |
| debugfs_remove_recursive(rdev->debugfs); |
| - flush_work(&rdev->disable_work.work); |
| WARN_ON(rdev->open_count); |
| regulator_remove_coupling(rdev); |
| unset_regulator_supplies(rdev); |
| -- |
| 2.20.1 |
| |