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SubjectRe: [PATCH] mfd: qcom-pm8xxx: Fix potential deadlock on &chip->pm_irq_lock
On Wed, Jun 28, 2023 at 07:28:40AM +0000, 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

You are correct, so please drop "I think", and change "should be" to
"are generally".

> 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().

I don't think this is a "tentative patch fix", it is the patch to fix
the issue. I think you can omit this line, because you already described
your problem, and the solution above.

>
> Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>

Reviewed-by: Bjorn Andersson <quic_bjorande@quicinc.com>

Regards,
Bjorn

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