Re: [PATCH for-4.21 01/10] x86/HPET: limit channel changes

["Roger Pau Monné" <roger.pau@citrix.com>]

On Thu, Oct 16, 2025 at 09:31:21AM +0200, Jan Beulich wrote:
> Despite 1db7829e5657 ("x86/hpet: do local APIC EOI after interrupt
> processing") we can still observe nested invocations of
> hpet_interrupt_handler(). This is, afaict, a result of previously used
> channels retaining their IRQ affinity until some other CPU re-uses them.
> Such nesting is increasingly problematic with higher CPU counts, as both
> handle_hpet_broadcast() and cpumask_raise_softirq() have a cpumask_t local
> variable. IOW already a single level of nesting may require more stack
> space (2 times above 4k) than we have available (8k), when NR_CPUS=16383
> (the maximum value presently possible).
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> Whether this is still worthwhile with "x86/HPET: use single, global, low-
> priority vector for broadcast IRQ" isn't quite clear to me.

Seeing the rest of the series, I don't think this is necessary
anymore?  Also the comment you here is made stale by the patch that
uses a global vector.

Thanks, Roger.