Re: [PATCH 0/6] IRQ handling patches backport to 4.14 stable

[Bhatnagar, Rishabh]

On 10/9/22 10:50 AM, Bhatnagar, Rishabh wrote:
> On 10/6/22 8:07 PM, Herrenschmidt, Benjamin wrote:
> > (putting my @amazon.com hat on)
> >
> > On Sun, 2022-10-02 at 17:30 +0200, Greg KH wrote:
> >
> >
> > > On Thu, Sep 29, 2022 at 09:06:45PM +0000, Rishabh Bhatnagar wrote:
> > > > This patch series backports a bunch of patches related IRQ handling
> > > > with respect to freeing the irq line while IRQ is in flight at CPU
> > > > or at the hardware level.
> > > > Recently we saw this issue in serial 8250 driver where the IRQ was
> > > > being
> > > > freed while the irq was in flight or not yet delivered to the CPU.
> > > > As a
> > > > result the irqchip was going into a wedged state and IRQ was not
> > > > getting
> > > > delivered to the cpu. These patches helped fixed the issue in 4.14
> > > > kernel.
> > > Why is the serial driver freeing an irq while the system is running?
> > > Ah, this could happen on a tty hangup, right?
> > Right. Rishabh answered that separately.
> >
> > > > Let us know if more patches need backporting.
> > > What hardware platform were these patches tested on to verify they
> > > work properly?  And why can't they move to 4.19 or newer if they
> > > really need this fix?  What's preventing that?
> > >
> > > As Amazon doesn't seem to be testing 4.14.y -rc releases, I find it
> > > odd that you all did this backport.  Is this a kernel that you all
> > > care about?
> > These were tested on a collection of EC2 instances, virtual and metal I
> > believe (Rishabh, please confirm).
> Yes these patches were tested on multiple virt/metal EC2 instances.
> > Amazon Linux 2 runs 4.14 or 5.10. Unfortunately we still have to
> > support customers running the former.
> >
> > We'll be including these patches in our releases, we thought it would
> > be nice to have them in -stable as well for the sake of whoever else
> > might be still using this kernel. No huge deal if they don't.
> >
> > As for testing -rc's, yes, we need to get better at that (and publish
> > what we test). Point taken :-)
> >
> > Cheers,
> > Ben.
Hi Greg

Let us know if you think it would be beneficial to take these backports 
for 4.14 stable.
We can drop this patch set otherwise.

Thanks alot,
Rishabh