possible deadlock due to irq_set_thread_affinity() calling into the scheduler (was Re: [PATCH v3 38/62] KVM: SVM: Take and hold ir_list_lock across IRTE updates in IOMMU)

[Thomas Gleixner]

On Wed, Jan 21 2026 at 19:13, Paolo Bonzini wrote:
> On 1/8/26 22:53, Thomas Gleixner wrote:
>> Are you still claiming that this is a kernel/irq bug?
>
> Not really, I did say I'd like to treat it as a kernel/irq bug...
> but certainly didn't have hopes high enough to "claim" that.
> I do think that it's ugly to have locks that are internal,
> non-leaf and held around callbacks; but people smarter than
> me have thought about it and you can't call it a bug anyway.

Deep core code has a tendency to be ugly. But if it makes your life
easier, then these wakeups can be delayed via an irq_work to be outside
of the lock. That needs some life-time issues to be addressed, but
should be doable.

Thanks,

        tglx