[PATCH 5.4 004/132] regulator: push allocation in regulator_ena_gpio_request() out of lock

From: Michał Mirosław mirq-linux@rere.qmqm.pl

[ Upstream commit 467bf30142c64f2eb64e2ac67fa4595126230efd ]

Move another allocation out of regulator_list_mutex-protected region, as reclaim might want to take the same lock.

WARNING: possible circular locking dependency detected 5.7.13+ #534 Not tainted ------------------------------------------------------ kswapd0/383 is trying to acquire lock: c0e5d920 (regulator_list_mutex){+.+.}-{3:3}, at: regulator_lock_dependent+0x54/0x2c0

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:

-> #1 (fs_reclaim){+.+.}-{0:0}: fs_reclaim_acquire.part.11+0x40/0x50 fs_reclaim_acquire+0x24/0x28 kmem_cache_alloc_trace+0x40/0x1e8 regulator_register+0x384/0x1630 devm_regulator_register+0x50/0x84 reg_fixed_voltage_probe+0x248/0x35c [...] other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(regulator_list_mutex); lock(fs_reclaim); lock(regulator_list_mutex);

*** DEADLOCK *** [...] 2 locks held by kswapd0/383: #0: c0e38518 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x0/0x50 #1: cb70e5e0 (hctx->srcu){....}-{0:0}, at: hctx_lock+0x60/0xb8 [...]

Fixes: 541d052d7215 ("regulator: core: Only support passing enable GPIO descriptors") [this commit only changes context] Fixes: f8702f9e4aa7 ("regulator: core: Use ww_mutex for regulators locking") [this is when the regulator_list_mutex was introduced in reclaim locking path]

Signed-off-by: Michał Mirosław mirq-linux@rere.qmqm.pl Link: https://lore.kernel.org/r/41fe6a9670335721b48e8f5195038c3d67a3bf92.159719532... Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/regulator/core.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c index a17aebe0aa7a7..19826641881bb 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -2217,10 +2217,13 @@ EXPORT_SYMBOL_GPL(regulator_bulk_unregister_supply_alias); static int regulator_ena_gpio_request(struct regulator_dev *rdev, const struct regulator_config *config) { - struct regulator_enable_gpio *pin; + struct regulator_enable_gpio *pin, *new_pin; struct gpio_desc *gpiod;

gpiod = config->ena_gpiod; + new_pin = kzalloc(sizeof(*new_pin), GFP_KERNEL); + + mutex_lock(&regulator_list_mutex);

list_for_each_entry(pin, &regulator_ena_gpio_list, list) { if (pin->gpiod == gpiod) { @@ -2229,9 +2232,13 @@ static int regulator_ena_gpio_request(struct regulator_dev *rdev, } }

- pin = kzalloc(sizeof(struct regulator_enable_gpio), GFP_KERNEL); - if (pin == NULL) + if (new_pin == NULL) { + mutex_unlock(&regulator_list_mutex); return -ENOMEM; + } + + pin = new_pin; + new_pin = NULL;

pin->gpiod = gpiod; list_add(&pin->list, &regulator_ena_gpio_list); @@ -2239,6 +2246,10 @@ static int regulator_ena_gpio_request(struct regulator_dev *rdev, update_ena_gpio_to_rdev: pin->request_count++; rdev->ena_pin = pin; + + mutex_unlock(&regulator_list_mutex); + kfree(new_pin); + return 0; }

@@ -5108,9 +5119,7 @@ regulator_register(const struct regulator_desc *regulator_desc, }

if (config->ena_gpiod) { - mutex_lock(&regulator_list_mutex); ret = regulator_ena_gpio_request(rdev, config); - mutex_unlock(&regulator_list_mutex); if (ret != 0) { rdev_err(rdev, "Failed to request enable GPIO: %d\n", ret);