On 2026-03-17 12:55:15 [+0100], Jan Kiszka wrote: > Point is that a task that was interrupted by a potentially threaded > interrupt keeps this flag longer that it needs it. And that is > apparently harmless, but fairly confusing.
correct. My only concern would be a shared handler where the second is not threaded. > >> With that in mind, the new logic here is no different from the one the > >> kernel used before. If both are not doing what they should, we likely > >> want to add a generic reset of hardirq_threaded to the IRQ exit path(s). > > > > The difference is that you expect that _everyone_ calling this driver > > has everything else threaded. This might not be the case. That is why > > this should be in core knowing what is called if threaded, use in driver > > after explicit killing that flag afterwards since you don't know what > > can follow or add a generic threaded infrastructure here. > > This driver is different, unfortunately. I'm not sure if we can / want > to thread everything that the platform interrupt does on x86. So far, > only the last part of it - vmbus handling - is threaded. On arm64, the > irq is exclusive (see vmbus_percpu_isr), thus everything can be and is > threaded. No, it is a percpu interrupt which are not forced-threaded. > >>> Couldn't the whole logic be integrated into the IRQ code? Then we could > >>> have mask/ unmask if supported/ provided and threaded interrupts. Then > >>> sysvec_hyperv_reenlightenment() could use a proper threaded interrupt > >>> instead apic_eoi() + schedule_delayed_work(). > >>> > >> > >> Again, you are thinking x86-only. We need a portable solution. > > > > well, ARM could use a threaded interrupt, too. > > For a reason we didn't explore in details, per-CPU interrupts aren't > threaded. See older version of this patch > (https://lore.kernel.org/lkml/[email protected]/) > where I thought I only had to fix x86, but arm64 was needing care as well. Per-CPU are usually timers or other things which are not threaded and have their own thing for the "second" port and I only remember MCE using a workqueue for notification. > Jan Sebastian
