From: Michał Mirosław mirq-linux@rere.qmqm.pl
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/1a889cf7f61c6429c9e6b34ddcdde99be77a26b6.159719532... Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/regulator/core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -4978,7 +4978,10 @@ static int regulator_init_coupling(struc 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); @@ -5184,9 +5187,7 @@ regulator_register(const struct regulato 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;