I'd like some additional eyes-on please.
This is very old code that you're changing and some of the people who
made the largest contributions are not on Cc.
On Wed, 28 Jun 2023, Chengfeng Ye wrote:
> As &chip->pm_irq_lock is acquired by pm8xxx_irq_handler() under irq
> context, other process context code should disable irq before acquiring
> the lock.
>
> I think .irq_set_type and .irq_get_irqchip_state callbacks should be
> executed from process context without irq disabled by default. Thus the
> same lock acquision should disable irq.
>
> Possible deadlock scenario
> pm8xxx_irq_set_type()
> -> pm8xxx_config_irq()
> -> spin_lock(&chip->pm_irq_lock)
> <irq interrupt>
> -> pm8xxx_irq_handler()
> -> pm8xxx_irq_master_handler()
> -> pm8xxx_irq_block_handler()
> -> pm8xxx_read_block_irq()
> -> spin_lock(&chip->pm_irq_lock) (deadlock here)
>
> This flaw was found using an experimental static analysis tool we are
> developing for irq-related deadlock.
>
> The tentative patch fix the potential deadlock by spin_lock_irqsave().
>
> Signed-off-by: Chengfeng Ye <dg573847474@xxxxxxxxx>
> ---
> drivers/mfd/qcom-pm8xxx.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mfd/qcom-pm8xxx.c b/drivers/mfd/qcom-pm8xxx.c
> index 9a948df8c28d..07c531bd1236 100644
> --- a/drivers/mfd/qcom-pm8xxx.c
> +++ b/drivers/mfd/qcom-pm8xxx.c
> @@ -103,8 +103,9 @@ static int
> pm8xxx_config_irq(struct pm_irq_chip *chip, unsigned int bp, unsigned int cp)
> {
> int rc;
> + unsigned long flags;
>
> - spin_lock(&chip->pm_irq_lock);
> + spin_lock_irqsave(&chip->pm_irq_lock, flags);
> rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, bp);
> if (rc) {
> pr_err("Failed Selecting Block %d rc=%d\n", bp, rc);
> @@ -116,7 +117,7 @@ pm8xxx_config_irq(struct pm_irq_chip *chip, unsigned int bp, unsigned int cp)
> if (rc)
> pr_err("Failed Configuring IRQ rc=%d\n", rc);
> bail:
> - spin_unlock(&chip->pm_irq_lock);
> + spin_unlock_irqrestore(&chip->pm_irq_lock, flags);
> return rc;
> }
>
> @@ -321,6 +322,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
> struct pm_irq_chip *chip = irq_data_get_irq_chip_data(d);
> unsigned int pmirq = irqd_to_hwirq(d);
> unsigned int bits;
> + unsigned long flags;
> int irq_bit;
> u8 block;
> int rc;
> @@ -331,7 +333,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
> block = pmirq / 8;
> irq_bit = pmirq % 8;
>
> - spin_lock(&chip->pm_irq_lock);
> + spin_lock_irqsave(&chip->pm_irq_lock, flags);
> rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, block);
> if (rc) {
> pr_err("Failed Selecting Block %d rc=%d\n", block, rc);
> @@ -346,7 +348,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
>
> *state = !!(bits & BIT(irq_bit));
> bail:
> - spin_unlock(&chip->pm_irq_lock);
> + spin_unlock_irqrestore(&chip->pm_irq_lock, flags);
>
> return rc;
> }
> --
> 2.17.1
>
--
Lee Jones [李琼斯]
