On Mon, Jun 7, 2021 at 1:00 PM Nitesh Lal <nilal@xxxxxxxxxx> wrote: > > On Fri, May 21, 2021 at 8:03 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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 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> > > Link: https://lore.kernel.org/r/20210501021832.743094-1-jesse.brandeburg@xxxxxxxxx > > --- > > 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); > > Another change required here, the above should be 'm' instead of 'cpumask'. I am going to and make the suggested changes to this patch and will post it with driver patches. Please let me know if there are any objections to that. > > > +} > > + > > 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) > > { > > > > > -- > Thanks > Nitesh -- Thanks Nitesh
