Messages in this thread Patch in this message | | | Date | Wed, 12 Aug 2020 03:31:34 +0200 | From | Michał Mirosław <> | Subject | [PATCH v2 2/7] regulator: push allocation in regulator_ena_gpio_request() out of lock |
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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> --- 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 510d234f6c46..3dd4d4914075 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -2203,10 +2203,13 @@ 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(®ulator_list_mutex); list_for_each_entry(pin, ®ulator_ena_gpio_list, list) { if (pin->gpiod == gpiod) { @@ -2215,9 +2218,13 @@ 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(®ulator_list_mutex); return -ENOMEM; + } + + pin = new_pin; + new_pin = NULL; pin->gpiod = gpiod; list_add(&pin->list, ®ulator_ena_gpio_list); @@ -2225,6 +2232,10 @@ static int regulator_ena_gpio_request(struct regulator_dev *rdev, update_ena_gpio_to_rdev: pin->request_count++; rdev->ena_pin = pin; + + mutex_unlock(®ulator_list_mutex); + kfree(new_pin); + return 0; } @@ -5179,9 +5190,7 @@ regulator_register(const struct regulator_desc *regulator_desc, } if (config->ena_gpiod) { - mutex_lock(®ulator_list_mutex); ret = regulator_ena_gpio_request(rdev, config); - mutex_unlock(®ulator_list_mutex); if (ret != 0) { rdev_err(rdev, "Failed to request enable GPIO: %d\n", ret); -- 2.20.1
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