Re: [PATCH v1 3/3] usb: typec: fusb302: Switch to threaded interrupt handler

[Hans de Goede <hansg@kernel.org>]

Hi,

On 7-Jan-26 10:52, 张永波 wrote:
>> Still ideally we would solve this in another way then
>> switching to a threaded IRQ handler.
>>
>> As the commit message of the mei-vsc fix mentions
>> the root cause of these errors is typically an interrupt
>> chip driver which uses IRQF_NO_THREAD disabling the auto
>> threading of all interrupt handlers in RT mode.
>>
>> So the first question here would be to see if that flag is
>> used in the interrupt chip and if yes, is that flag really
>> necessary ?
> This is very similar to the issue addressed in commit 24b176d8827d
> ("drm/msm/dsi: Remove spurious IRQF_ONESHOT flag").
> The IRQF_ONESHOT flag is preventing forced threading here.
> 
> In irq_setup_forced_threading(), the conversion to threaded interrupts
> is explicitly skipped if any of the IRQF_NO_THREAD, IRQF_PERCPU,
> or IRQF_ONESHOT flags are present. In this case, IRQF_ONESHOT
> appears to be the reason.

Ah, well the code effectively does its own IRQF_ONESHOT handling,
since it needs to do its own threaded-irq like handling for
suspend/resume reasons. It disables the IRQ when it fires and
then only re-enables it once the work has done processing the IRQ.

So it should be perfectly safe to drop the IRQF_ONESHOT flag.

If that also works to resolve the lockdep issue that would be
the preferred way of fixing this IMHO.

Regards,

Hans