Re: [PATCH] genirq: Provide new interfaces for affinity hints
From: Nitesh Lal <hidden>
Date: 2021-05-21 16:13:42
Also in:
intel-wired-lan, linux-api, linux-pci, lkml
On Fri, May 21, 2021 at 8:03 AM Thomas Gleixner [off-list ref] wrote:
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_apply_affinity_hint() - Set the pointer and apply the affinity to
the interruptAny reason why you ruled out the usage of irq_set_affinity_and_hint()? IMHO the latter makes it very clear what the function is meant to do.
Make irq_set_affinity_hint() a wrapper around irq_apply_affinity_hint() and document it to be phased out.
Right, so eventually we will be only left with the following APIs that the driver will use: irq_set_affinity()- for drivers that only wants to set the affinity mask irq_apply_affinity_hint/irq_set_affinity_and_hint() - for drivers that wants to set same affinity and hint mask irq_update_affinity_hint() - for drivers that only wants to update the hint mask Thanks for clearing this.
quoted hunk ↗ jump to hunk
Signed-off-by: Thomas Gleixner <redacted> Link: https://lore.kernel.org/r/20210501021832.743094-1-jesse.brandeburg@intel.com (local) --- Applies on: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq/core --- include/linux/interrupt.h | 41 ++++++++++++++++++++++++++++++++++++++++- kernel/irq/manage.c | 8 ++++---- 2 files changed, 44 insertions(+), 5 deletions(-)--- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h@@ -328,7 +328,46 @@ extern int irq_force_affinity(unsigned i extern int irq_can_set_affinity(unsigned int irq); extern int irq_select_affinity(unsigned int irq); -extern int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m); +extern int __irq_apply_affinity_hint(unsigned int irq, const struct cpumask *m, + bool setaffinity); + +/** + * irq_update_affinity_hint - Update the affinity hint + * @irq: Interrupt to update + * @cpumask: cpumask pointer (NULL to clear the hint) + * + * Updates the affinity hint, but does not change the affinity of the interrupt. + */ +static inline int +irq_update_affinity_hint(unsigned int irq, const struct cpumask *m) +{ + return __irq_apply_affinity_hint(irq, m, true); +} + +/** + * irq_apply_affinity_hint - Update the affinity hint and apply the provided + * cpumask to the interrupt + * @irq: Interrupt to update + * @cpumask: cpumask pointer (NULL to clear the hint) + * + * Updates the affinity hint and if @cpumask is not NULL it applies it as + * the affinity of that interrupt. + */ +static inline int +irq_apply_affinity_hint(unsigned int irq, const struct cpumask *m) +{ + return __irq_apply_affinity_hint(irq, m, true); +} + +/* + * Deprecated. Use irq_update_affinity_hint() or irq_apply_affinity_hint() + * instead. + */ +static inline int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m) +{ + return irq_apply_affinity_hint(irq, cpumask); +} + extern int irq_update_affinity_desc(unsigned int irq, struct irq_affinity_desc *affinity); --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c@@ -487,7 +487,8 @@ int irq_force_affinity(unsigned int irq, } EXPORT_SYMBOL_GPL(irq_force_affinity); -int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m) +int __irq_apply_affinity_hint(unsigned int irq, const struct cpumask *m, + bool setaffinity) { unsigned long flags; struct irq_desc *desc = irq_get_desc_lock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);@@ -496,12 +497,11 @@ int irq_set_affinity_hint(unsigned int i return -EINVAL; desc->affinity_hint = m; irq_put_desc_unlock(desc, flags); - /* set the initial affinity to prevent every interrupt being on CPU0 */ - if (m) + if (m && setaffinity) __irq_set_affinity(irq, m, false); return 0; } -EXPORT_SYMBOL_GPL(irq_set_affinity_hint); +EXPORT_SYMBOL_GPL(__irq_apply_affinity_hint); static void irq_affinity_notify(struct work_struct *work) {
-- Nitesh