Re: [PATCH] PCI/AER: Use IRQF_NO_THREAD on aer_irq

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2025-09-04 15:18:50 [+0200], Lukas Wunner wrote:
> On Thu, Sep 04, 2025 at 02:48:21PM +0200, Lukas Wunner wrote:
> > On Thu, Sep 04, 2025 at 09:30:24AM +0200, Sebastian Andrzej Siewior wrote:
> > > On 2025-09-02 17:44:41 [-0500], Crystal Wood wrote:
> > > > +++ b/drivers/pci/pcie/aer.c
> > > > @@ -1671,7 +1671,8 @@ static int aer_probe(struct pcie_device *dev)
> > > >  	set_service_data(dev, rpc);
> > > >  
> > > >  	status = devm_request_threaded_irq(device, dev->irq, aer_irq, aer_isr,
> > > > -					   IRQF_SHARED, "aerdrv", dev);
> > > > +					   IRQF_NO_THREAD | IRQF_SHARED,
> > > > +					   "aerdrv", dev);
> > > 
> > > I'm not sure if this works with IRQF_SHARED. Your primary handler is
> > > IRQF_SHARED + IRQF_NO_THREAD and another shared handler which is
> > > forced-threaded will have IRQF_SHARED + IRQF_ONESHOT. 
> > > If the core does not complain, all good. Worst case might be the shared
> > > ONESHOT lets your primary handler starve. It would be nice if you could
> > > check if you have shared handler here (I have no aer I three boxes I
> > > checked).
> > 
> > Yes, interrupt sharing can happen if the Root Port uses legacy INTx
> > interrupts.  In that case other port services such as hotplug,
> > bandwidth control, PME or DPC may use the same interrupt.
> 
> I should add that none of these other port service drivers use
> IRQF_ONESHOT.  They're all IRQF_SHARED only.

Yes. But. If they get forced-threaded then we have a primary handler
irq_default_primary_handler() as the hardirq handler. This one would be
marked IRQF_ONESHOT. The other primary handler would be aer_irq() in
this case. As long as all (or none) are forced-threaded then it is fine.
In this case it could be a miss match, I'm not sure.

> Thanks,
> 
> Lukas

Sebastian