Commit 65c7cded authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

genirq: Provide new interfaces for affinity hints 



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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarNitesh Narayan Lal <nitesh@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210501021832.743094-1-jesse.brandeburg@intel.com
Link: https://lore.kernel.org/r/20210903152430.244937-2-nitesh@redhat.com
parent 4946f15e

include/linux/interrupt.h

+52 −1
Original line number Diff line number Diff line
@@ -329,7 +329,46 @@ extern int irq_force_affinity(unsigned int irq, const struct cpumask *cpumask); 
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

 * @m:		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, false);

}



/**

 * irq_set_affinity_and_hint - Update the affinity hint and apply the provided

 *			     cpumask to the interrupt

 * @irq:	Interrupt to update

 * @m:		cpumask pointer (NULL to clear the hint)

 *

 * Updates the affinity hint and if @m is not NULL it applies it as the

 * affinity of that interrupt.

 */

static inline int

irq_set_affinity_and_hint(unsigned int irq, const struct cpumask *m)

{

	return __irq_apply_affinity_hint(irq, m, true);

}



/*

 * Deprecated. Use irq_update_affinity_hint() or irq_set_affinity_and_hint()

 * instead.

 */

static inline int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)

{

	return irq_set_affinity_and_hint(irq, m);

}



extern int irq_update_affinity_desc(unsigned int irq,

				    struct irq_affinity_desc *affinity);
@@ -361,6 +400,18 @@ static inline int irq_can_set_affinity(unsigned int irq) 


static inline int irq_select_affinity(unsigned int irq)  { return 0; }



static inline int irq_update_affinity_hint(unsigned int irq,

					   const struct cpumask *m)

{

	return -EINVAL;

}



static inline int irq_set_affinity_and_hint(unsigned int irq,

					    const struct cpumask *m)

{

	return -EINVAL;

}



static inline int irq_set_affinity_hint(unsigned int irq,

					const struct cpumask *m)

{

kernel/irq/manage.c

+4 −4
Original line number Diff line number Diff line
@@ -486,7 +486,8 @@ int irq_force_affinity(unsigned int irq, const struct cpumask *cpumask) 
}

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);
@@ -495,12 +496,11 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m) 
		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)

{