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

From: Bhatnagar, Rishabh
Date: Sun Oct 09 2022 - 13:50:25 EST

On 10/6/22 8:07 PM, Herrenschmidt, Benjamin wrote:
(putting my 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
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
delivered to the cpu. These patches helped fixed the issue in 4.14
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 :-)