Commit 09afa276 authored Jan 13, 2015 by Semen Protsenko Committed by Linus Walleij Jan 15, 2015

gpio: max732x: Fix possible deadlock



This patch was derived from next one:
"gpio: fix pca953x set_type 'scheduling while atomic' bug".

After adding entry that consumes max732x GPIO as interrupt line to dts
file, deadlock appears somewhere in max732x probe function.

Deadlock caught by lockdep (from kernel log):
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< cut here >>>>>>>>>>>>>>>>>>>>>>>>>>>
[    0.473419] ======================================================
[    0.473419] [ INFO: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected ]
[    0.473449] 3.x.xx-xxxxx-xxxxxxxx-dirty #2 Tainted: G        W
[    0.473449] ------------------------------------------------------
[    0.473449] swapper/0/1 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
[    0.473449]  (&lock->wait_lock){+.+...}, at: [<c072e350>] rt_mutex_trylock+0xc/0x74
[    0.473480]
[    0.473480] and this task is already holding:
[    0.473510]  (&chip->lock){......}, at: [<c0314514>] max732x_gpio_set_value+0x2c/0xa4
[    0.473541] which would create a new lock dependency:
[    0.473541]  (&chip->lock){......} -> (&lock->wait_lock){+.+...}

...

[    0.474273]  *** DEADLOCK ***
[    0.474273]
[    0.474273] 5 locks held by swapper/0/1:
[    0.474273]  #0:  (&__lockdep_no_validate__){......}, at: [<c03b2328>] __driver_attach+0x48/0x98
[    0.474304]  #1:  (&__lockdep_no_validate__){......}, at: [<c03b2338>] __driver_attach+0x58/0x98
[    0.474334]  #2:  (&chip->irq_lock){+.+...}, at: [<c0313e3c>] max732x_irq_bus_lock+0x14/0x20
[    0.474365]  #3:  (&irq_desc_lock_class){-.....}, at: [<c00a65a4>] __irq_get_desc_lock+0x48/0x88
[    0.474365]  #4:  (&chip->lock){......}, at: [<c0314514>] max732x_gpio
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< cut here >>>>>>>>>>>>>>>>>>>>>>>>>>>

Signed-off-by: Semen Protsenko <semen.protsenko@globallogic.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

parent 479f8a57

drivers/gpio/gpio-max732x.c

+11 −1

Original line number	Diff line number	Diff line
		@@ -377,8 +377,18 @@ static void max732x_irq_bus_lock(struct irq_data *d)
		static void max732x_irq_bus_sync_unlock(struct irq_data *d)
		{
		struct max732x_chip *chip = irq_data_get_irq_chip_data(d);
		uint16_t new_irqs;
		uint16_t level;

		max732x_irq_update_mask(chip);

		new_irqs = chip->irq_trig_fall \| chip->irq_trig_raise;
		while (new_irqs) {
		level = __ffs(new_irqs);
		max732x_gpio_direction_input(&chip->gpio_chip, level);
		new_irqs &= ~(1 << level);
		}

		mutex_unlock(&chip->irq_lock);
		}

		@@ -410,7 +420,7 @@ static int max732x_irq_set_type(struct irq_data *d, unsigned int type)
		else
		chip->irq_trig_raise &= ~mask;

		return max732x_gpio_direction_input(&chip->gpio_chip, off);
		return 0;
		}

		static struct irq_chip max732x_irq_chip = {