blob: 3268726b528f88b863abd030b339e8ee82f1d7eb [file] [log] [blame]
From 5a684f1a47bd64cc5bd9918c1e2db253b6bb26d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= <mirq-linux@rere.qmqm.pl>
Date: Wed, 12 Aug 2020 03:31:34 +0200
Subject: [PATCH] regulator: push allocation in regulator_init_coupling()
outside of lock
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commit 73a32129f8ccb556704a26b422f54e048bf14bd0 upstream.
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
[...]
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>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/1a889cf7f61c6429c9e6b34ddcdde99be77a26b6.1597195321.git.mirq-linux@rere.qmqm.pl
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index dbc4a90c6c4b..cb5f33b97082 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -4880,7 +4880,10 @@ 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);
@@ -5079,9 +5082,7 @@ 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;
--
2.27.0