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From: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
To: Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>,
	Dmitry Osipenko <digetx@gmail.com>,
	Vladimir Zapolskiy <vz@mleia.com>
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH v2 1/7] regulator: push allocation in regulator_init_coupling() outside of lock
Date: Wed, 12 Aug 2020 03:31:34 +0200
Message-ID: <1a889cf7f61c6429c9e6b34ddcdde99be77a26b6.1597195321.git.mirq-linux@rere.qmqm.pl> (raw)
In-Reply-To: <cover.1597195321.git.mirq-linux@rere.qmqm.pl>

Allocating memory with regulator_list_mutex held makes lockdep unhappy
when memory pressure makes the system do fs_reclaim on eg. eMMC using
a regulator. Push the lock inside regulator_init_coupling() after the
allocation.

======================================================
WARNING: possible circular locking dependency detected
5.7.13+ #533 Not tainted
------------------------------------------------------
kswapd0/383 is trying to acquire lock:
cca78ca4 (&sbi->write_io[i][j].io_rwsem){++++}-{3:3}, at: __submit_merged_write_cond+0x104/0x154
but task is already holding lock:
c0e38518 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x0/0x50
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (fs_reclaim){+.+.}-{0:0}:
       fs_reclaim_acquire.part.11+0x40/0x50
       fs_reclaim_acquire+0x24/0x28
       __kmalloc+0x54/0x218
       regulator_register+0x860/0x1584
       dummy_regulator_probe+0x60/0xa8
[...]
other info that might help us debug this:

Chain exists of:
  &sbi->write_io[i][j].io_rwsem --> regulator_list_mutex --> fs_reclaim

Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(regulator_list_mutex);
                               lock(fs_reclaim);
  lock(&sbi->write_io[i][j].io_rwsem);
 *** DEADLOCK ***

1 lock held by kswapd0/383:
 #0: c0e38518 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x0/0x50
[...]

Cc: stable@vger.kernel.org
Fixes: d8ca7d184b33 ("regulator: core: Introduce API for regulators coupling customization")
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/regulator/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 0a32c3da0e26..510d234f6c46 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -5010,7 +5010,10 @@ static int regulator_init_coupling(struct regulator_dev *rdev)
 	if (!of_check_coupling_data(rdev))
 		return -EPERM;
 
+	mutex_lock(&regulator_list_mutex);
 	rdev->coupling_desc.coupler = regulator_find_coupler(rdev);
+	mutex_unlock(&regulator_list_mutex);
+
 	if (IS_ERR(rdev->coupling_desc.coupler)) {
 		err = PTR_ERR(rdev->coupling_desc.coupler);
 		rdev_err(rdev, "failed to get coupler: %d\n", err);
@@ -5218,9 +5221,7 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	if (ret < 0)
 		goto wash;
 
-	mutex_lock(&regulator_list_mutex);
 	ret = regulator_init_coupling(rdev);
-	mutex_unlock(&regulator_list_mutex);
 	if (ret < 0)
 		goto wash;
 
-- 
2.20.1


  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-12  1:31 [PATCH v2 0/7] regulator: fix deadlock vs memory reclaim Michał Mirosław
2020-08-12  1:31 ` Michał Mirosław [this message]
2020-08-12  1:31 ` [PATCH v2 2/7] regulator: push allocation in regulator_ena_gpio_request() out of lock Michał Mirosław
2020-08-18  0:25   ` Dmitry Osipenko
2020-08-12  1:31 ` [PATCH v2 3/7] regulator: push allocations in create_regulator() outside " Michał Mirosław
2020-08-12  1:31 ` [PATCH v2 5/7] regulator: plug of_node leak in regulator_register()'s error path Michał Mirosław
2020-08-12  6:29   ` Vladimir Zapolskiy
2020-08-12 14:09     ` Michał Mirosław
2020-08-13  8:29       ` Vladimir Zapolskiy
2020-08-12  1:31 ` [PATCH v2 4/7] regulator: push allocation in set_consumer_device_supply() out of lock Michał Mirosław
2020-08-12  1:31 ` [PATCH v2 6/7] regulator: cleanup regulator_ena_gpio_free() Michał Mirosław
2020-08-12  1:31 ` [PATCH v2 7/7] regulator: remove superfluous lock in regulator_resolve_coupling() Michał Mirosław

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