Re: [PATCH v4 01/14] genirq: Provide new interfaces for affinity hints
From: Jakub Kicinski
Date: Tue Jul 20 2021 - 07:05:47 EST
On Mon, 19 Jul 2021 14:07:33 -0400, Nitesh Narayan Lal wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> The discussion about removing the side effect of irq_set_affinity_hint() of
> actually applying the cpumask (if not NULL) as affinity to the interrupt,
> unearthed a few unpleasantries:
> 1) The modular perf drivers rely on the current behaviour for the very
> wrong reasons.
> 2) While none of the other drivers prevents user space from changing
> the affinity, a cursorily inspection shows that there are at least
> expectations in some drivers.
> #1 needs to be cleaned up anyway, so that's not a problem
> #2 might result in subtle regressions especially when irqbalanced (which
> nowadays ignores the affinity hint) is disabled.
> Provide new interfaces:
> irq_update_affinity_hint() - Only sets the affinity hint pointer
> irq_set_affinity_and_hint() - Set the pointer and apply the affinity to
> the interrupt
> Make irq_set_affinity_hint() a wrapper around irq_apply_affinity_hint() and
> document it to be phased out.
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Nitesh Narayan Lal <nitesh@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20210501021832.743094-1-jesse.brandeburg@xxxxxxxxx
include/linux/interrupt.h:343: warning: Function parameter or member 'm' not described in 'irq_update_affinity_hint'
include/linux/interrupt.h:343: warning: Excess function parameter 'cpumask' description in 'irq_update_affinity_hint'
include/linux/interrupt.h:358: warning: Function parameter or member 'm' not described in 'irq_set_affinity_and_hint'
include/linux/interrupt.h:358: warning: Excess function parameter 'cpumask' description in 'irq_set_affinity_and_hint'