Re: [PATCH] gpio: mpsse: fix race when arming the IRQ poll worker

[Fan Wu]

> On Sep 23, 2026, at 16:15, Bartosz Golaszewski <brgl@xxxxxxxxxx> wrote:
> 
> I probably wouldn't have noticed but Sashiko found an issue on PREEMPT_RT
> kernels[1].
> 
> Bart
> 
> [1] https://sashiko.dev/#/patchset/20260923030855.410109-1-fanwu01%40zju.edu.cn?part=1

Hi Bart,

You're right, thank you for catching this.

The new kfree() is called while holding priv->irq_spin. More importantly,
moving it just after that scoped guard would not be sufficient: irq_enable()
is invoked with the IRQ descriptor raw spinlock held by the IRQ core.

Thus, a normal kfree() cannot be used on this path on PREEMPT_RT. The
worker must instead be disposed of from a safe context, while keeping its
list publication and schedule_work() together under irq_spin so that the
disconnect race is not reintroduced.

I will rework the cleanup path accordingly and also recheck the pre-existing
GFP_NOWAIT allocation in this irqchip callback for PREEMPT_RT constraints.

Thanks,
Fan