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Message-Id: <b305adf8bcde9417cdd5c9d84ef5ed99541f0e2c.1597107682.git.mirq-linux@rere.qmqm.pl>
Date: Tue, 11 Aug 2020 03:07:37 +0200
From: Michał Mirosław <mirq-linux@...e.qmqm.pl>
To: Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>,
Dmitry Osipenko <digetx@...il.com>
Cc: linux-kernel@...r.kernel.org, Vladimir Zapolskiy <vz@...ia.com>
Subject: [PATCH 1/7] regulator: push allocation in regulator_init_coupling()
outside of lock
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@...r.kernel.org
Fixes: d8ca7d184b33 ("regulator: core: Introduce API for regulators coupling customization")
Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
---
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(®ulator_list_mutex);
rdev->coupling_desc.coupler = regulator_find_coupler(rdev);
+ mutex_unlock(®ulator_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(®ulator_list_mutex);
ret = regulator_init_coupling(rdev);
- mutex_unlock(®ulator_list_mutex);
if (ret < 0)
goto wash;
--
2.20.1
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