[RFC][PATCH 0/5] RFS hardware acceleration (v2)

[RFC][PATCH 0/5] RFS hardware acceleration (v2)

[Ben Hutchings]

This patch series extends RFS to use hardware RX filters where
available.  Depending on the number of hardware RX queues and their
IRQs' affinity, this should reduce the need for IPIs or at least get
packets delivered to the right NUMA node.

The first patch implements IRQ affinity notifiers, based on the outline
that Thomas Gleixner wrote in response to the previous version of this
patch series.

The second patch is a generalisation of the CPU affinity reverse-
mapping, plus functions to maintain such a mapping based on the new IRQ
affinity notifiers.

The remaining patches add the RFS acceleration hooks and an
implementation in the sfc driver.  These are largely unchanged from the
previous version of this patch series; I haven't yet had the time to do
further tuning yet.  However I have done some more benchmarking and will
send some results in a separate follow-up to this.

Ben.

Ben Hutchings (5):
  genirq: Add IRQ affinity notifiers
  lib: cpu_rmap: CPU affinity reverse-mapping
  net: RPS: Enable hardware acceleration
  sfc: Limit filter search depth further for performance hints (i.e.
    RFS)
  sfc: Implement RFS acceleration

 drivers/net/sfc/Kconfig   |    4 +
 drivers/net/sfc/efx.c     |   66 ++++++++++--
 drivers/net/sfc/efx.h     |    9 ++
 drivers/net/sfc/filter.c  |  113 ++++++++++++++++++-
 include/linux/cpu_rmap.h  |   73 ++++++++++++
 include/linux/interrupt.h |   41 +++++++
 include/linux/irqdesc.h   |    3 +
 include/linux/netdevice.h |   31 +++++-
 kernel/irq/manage.c       |   81 +++++++++++++
 lib/Kconfig               |    4 +
 lib/Makefile              |    2 +
 lib/cpu_rmap.c            |  272 +++++++++++++++++++++++++++++++++++++++++++++
 net/Kconfig               |    1 +
 net/core/dev.c            |   89 ++++++++++++++-
 14 files changed, 767 insertions(+), 22 deletions(-)
 create mode 100644 include/linux/cpu_rmap.h
 create mode 100644 lib/cpu_rmap.c

-- 
1.7.3.2


-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

[RFC][PATCH 1/5] genirq: Add IRQ affinity notifiers

[Ben Hutchings]

When initiating I/O on a multiqueue and multi-IRQ device, we may want
to select a queue for which the response will be handled on the same
or a nearby CPU.  This requires a reverse-map of IRQ affinity.  Add a
notification mechanism to support this.

This is based closely on work by Thomas Gleixner <tglx@linutronix.de>.
---
 include/linux/interrupt.h |   41 +++++++++++++++++++++++
 include/linux/irqdesc.h   |    3 ++
 kernel/irq/manage.c       |   81 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 125 insertions(+), 0 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 79d0c4f..1649b30 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -14,6 +14,8 @@
 #include <linux/smp.h>
 #include <linux/percpu.h>
 #include <linux/hrtimer.h>
+#include <linux/kref.h>
+#include <linux/workqueue.h>
 
 #include <asm/atomic.h>
 #include <asm/ptrace.h>
@@ -231,6 +233,28 @@ static inline void resume_device_irqs(void) { };
 static inline int check_wakeup_irqs(void) { return 0; }
 #endif
 
+/**
+ * struct irq_affinity_notify - context for notification of IRQ affinity changes
+ * @irq:		Interrupt to which notification applies
+ * @kref:		Reference count, for internal use
+ * @work:		Work item, for internal use
+ * @notify:		Function to be called on change.  This will be
+ *			called in process context.
+ * @release:		Function to be called on release.  This will be
+ *			called in process context.  Once registered, the
+ *			structure must only be freed when this function is
+ *			called or later.
+ */
+struct irq_affinity_notify {
+        unsigned int irq;
+        struct kref kref;
+#if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_HARDIRQS)
+        struct work_struct work;
+#endif
+        void (*notify)(struct irq_affinity_notify *, const cpumask_t *mask);
+        void (*release)(struct kref *ref);
+};
+
 #if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_HARDIRQS)
 
 extern cpumask_var_t irq_default_affinity;
@@ -240,6 +264,13 @@ 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_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify);
+
+static inline void irq_run_affinity_notifiers(void)
+{
+	flush_scheduled_work();
+}
 #else /* CONFIG_SMP */
 
 static inline int irq_set_affinity(unsigned int irq, const struct cpumask *m)
@@ -259,6 +290,16 @@ static inline int irq_set_affinity_hint(unsigned int irq,
 {
 	return -EINVAL;
 }
+
+static inline int
+irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
+{
+	return 0;
+}
+
+static inline void irq_run_affinity_notifiers(void)
+{
+}
 #endif /* CONFIG_SMP && CONFIG_GENERIC_HARDIRQS */
 
 #ifdef CONFIG_GENERIC_HARDIRQS
diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index 979c68c..5e0d2e4 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -8,6 +8,7 @@
  * For now it's included from <linux/irq.h>
  */
 
+struct irq_affinity_notify;
 struct proc_dir_entry;
 struct timer_rand_state;
 /**
@@ -24,6 +25,7 @@ struct timer_rand_state;
  * @last_unhandled:	aging timer for unhandled count
  * @irqs_unhandled:	stats field for spurious unhandled interrupts
  * @lock:		locking for SMP
+ * @affinity_notify:	context for notification of affinity changes
  * @pending_mask:	pending rebalanced interrupts
  * @threads_active:	number of irqaction threads currently running
  * @wait_for_threads:	wait queue for sync_irq to wait for threaded handlers
@@ -70,6 +72,7 @@ struct irq_desc {
 	raw_spinlock_t		lock;
 #ifdef CONFIG_SMP
 	const struct cpumask	*affinity_hint;
+	struct irq_affinity_notify *affinity_notify;
 #ifdef CONFIG_GENERIC_PENDING_IRQ
 	cpumask_var_t		pending_mask;
 #endif
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 5f92acc..82b48d0 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -134,6 +134,10 @@ int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask)
 		irq_set_thread_affinity(desc);
 	}
 #endif
+	if (desc->affinity_notify) {
+		kref_get(&desc->affinity_notify->kref);
+		schedule_work(&desc->affinity_notify->work);
+	}
 	desc->status |= IRQ_AFFINITY_SET;
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 	return 0;
@@ -155,6 +159,79 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
 }
 EXPORT_SYMBOL_GPL(irq_set_affinity_hint);
 
+static void irq_affinity_notify(struct work_struct *work)
+{
+	struct irq_affinity_notify *notify =
+		container_of(work, struct irq_affinity_notify, work);
+	struct irq_desc *desc = irq_to_desc(notify->irq);
+	cpumask_var_t cpumask;
+	unsigned long flags;
+
+	if (!desc)
+		goto out;
+
+	if (!alloc_cpumask_var(&cpumask, GFP_KERNEL))
+		goto out;
+
+	raw_spin_lock_irqsave(&desc->lock, flags);
+#ifdef CONFIG_GENERIC_PENDING_IRQ
+	if (desc->status & IRQ_MOVE_PENDING)
+		cpumask_copy(cpumask, desc->pending_mask);
+	else
+#endif
+		cpumask_copy(cpumask, desc->affinity);
+	raw_spin_unlock_irqrestore(&desc->lock, flags);
+
+	notify->notify(notify, cpumask);
+
+	free_cpumask_var(cpumask);
+out:
+	kref_put(&notify->kref, notify->release);
+}
+
+/**
+ *	irq_set_affinity_notifier - control notification of IRQ affinity changes
+ *	@irq:		Interrupt for which to enable/disable notification
+ *	@notify:	Context for notification, or %NULL to disable
+ *			notification.  Function pointers must be initialised;
+ *			the other fields will be initialised by this function.
+ *
+ *	Must be called in process context.  Notification may only be enabled
+ *	after the IRQ is allocated but before it is bound with request_irq()
+ *	and must be disabled before the IRQ is freed using free_irq().
+ */
+int
+irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+	struct irq_affinity_notify *old_notify;
+	unsigned long flags;
+
+	/* The release function is promised process context */
+	might_sleep();
+
+	if (!desc)
+		return -EINVAL;
+
+	/* Complete initialisation of *notify */
+	if (notify) {
+		notify->irq = irq;
+		kref_init(&notify->kref);
+		INIT_WORK(&notify->work, irq_affinity_notify);
+	}
+
+	raw_spin_lock_irqsave(&desc->lock, flags);
+	old_notify = desc->affinity_notify;
+	desc->affinity_notify = notify;
+	raw_spin_unlock_irqrestore(&desc->lock, flags);
+
+	if (old_notify)
+		kref_put(&old_notify->kref, old_notify->release);
+	
+	return 0;
+}
+EXPORT_SYMBOL_GPL(irq_set_affinity_notifier);
+
 #ifndef CONFIG_AUTO_IRQ_AFFINITY
 /*
  * Generic version of the affinity autoselector.
@@ -1002,6 +1079,10 @@ void free_irq(unsigned int irq, void *dev_id)
 	if (!desc)
 		return;
 
+#ifdef CONFIG_SMP
+	BUG_ON(desc->affinity_notify);
+#endif
+
 	chip_bus_lock(desc);
 	kfree(__free_irq(irq, dev_id));
 	chip_bus_sync_unlock(desc);
-- 
1.7.3.2



-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

[RFC][PATCH 2/5] lib: cpu_rmap: CPU affinity reverse-mapping

[Ben Hutchings]

When initiating I/O on a multiqueue and multi-IRQ device, we may want
to select a queue for which the response will be handled on the same
or a nearby CPU.  This requires a reverse-map of IRQ affinity.  Add
library functions to support a generic reverse-mapping from CPUs to
objects with affinity and the specific case where the objects are
IRQs.
---
 include/linux/cpu_rmap.h |   73 ++++++++++++
 lib/Kconfig              |    4 +
 lib/Makefile             |    2 +
 lib/cpu_rmap.c           |  272 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 351 insertions(+), 0 deletions(-)
 create mode 100644 include/linux/cpu_rmap.h
 create mode 100644 lib/cpu_rmap.c

diff --git a/include/linux/cpu_rmap.h b/include/linux/cpu_rmap.h
new file mode 100644
index 0000000..4771e95
--- /dev/null
+++ b/include/linux/cpu_rmap.h
@@ -0,0 +1,73 @@
+/*
+ * cpu_rmap.c: CPU affinity reverse-map support
+ * Copyright 2010 Solarflare Communications Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation, incorporated herein by reference.
+ */
+
+#include <linux/cpumask.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+
+/**
+ * struct cpu_rmap - CPU affinity reverse-map
+ * @near: For each CPU, the index and distance to the nearest object,
+ *      based on affinity masks
+ * @size: Number of objects to be reverse-mapped
+ * @used: Number of objects added
+ * @obj: Array of object pointers
+ */
+struct cpu_rmap {
+	struct {
+		u16     index;
+		u16     dist;
+	} near[NR_CPUS];
+	u16		size, used;
+	void		*obj[0];
+};
+#define CPU_RMAP_DIST_INF 0xffff
+
+extern struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags);
+
+/**
+ * free_cpu_rmap - free CPU affinity reverse-map
+ * @rmap: Reverse-map allocated with alloc_cpu_rmap(), or %NULL
+ */
+static inline void free_cpu_rmap(struct cpu_rmap *rmap)
+{
+	kfree(rmap);
+}
+
+extern int cpu_rmap_add(struct cpu_rmap *rmap, void *obj);
+extern void cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
+			    const struct cpumask *affinity);
+
+static inline u16 cpu_rmap_lookup_index(struct cpu_rmap *rmap, unsigned int cpu)
+{
+	return rmap->near[cpu].index;
+}
+
+static inline void *cpu_rmap_lookup_obj(struct cpu_rmap *rmap, unsigned int cpu)
+{
+	return rmap->obj[rmap->near[cpu].index];
+}
+
+#ifdef CONFIG_GENERIC_HARDIRQS
+
+/**
+ * alloc_irq_cpu_rmap - allocate CPU affinity reverse-map for IRQs
+ * @size: Number of objects to be mapped
+ *
+ * Must be called in process context.
+ */
+static inline struct cpu_rmap *alloc_irq_cpu_rmap(unsigned int size)
+{
+	return alloc_cpu_rmap(size, GFP_KERNEL);
+}
+extern void free_irq_cpu_rmap(struct cpu_rmap *rmap);
+
+extern int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq);
+
+#endif
diff --git a/lib/Kconfig b/lib/Kconfig
index fa9bf2c..a66c76d 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -195,6 +195,10 @@ config DISABLE_OBSOLETE_CPUMASK_FUNCTIONS
        bool "Disable obsolete cpumask functions" if DEBUG_PER_CPU_MAPS
        depends on EXPERIMENTAL && BROKEN
 
+config CPU_RMAP
+	bool
+	depends on SMP
+
 #
 # Netlink attribute parsing support is select'ed if needed
 #
diff --git a/lib/Makefile b/lib/Makefile
index e6a3763..ded1a81 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -106,6 +106,8 @@ obj-$(CONFIG_GENERIC_ATOMIC64) += atomic64.o
 
 obj-$(CONFIG_ATOMIC64_SELFTEST) += atomic64_test.o
 
+obj-$(CONFIG_CPU_RMAP) += cpu_rmap.o
+
 hostprogs-y	:= gen_crc32table
 clean-files	:= crc32table.h
 
diff --git a/lib/cpu_rmap.c b/lib/cpu_rmap.c
new file mode 100644
index 0000000..394f277
--- /dev/null
+++ b/lib/cpu_rmap.c
@@ -0,0 +1,272 @@
+/*
+ * cpu_rmap.c: CPU affinity reverse-map support
+ * Copyright 2010 Solarflare Communications Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation, incorporated herein by reference.
+ */
+
+#include <linux/cpu_rmap.h>
+#ifdef CONFIG_GENERIC_HARDIRQS
+#include <linux/interrupt.h>
+#endif
+#include <linux/module.h>
+
+/*
+ * These functions maintain a mapping from CPUs to some ordered set of
+ * objects with CPU affinities.  This can be seen as a reverse-map of
+ * CPU affinity.  However, we do not assume that the object affinities
+ * cover all CPUs in the system.  For those CPUs not directly covered
+ * by object affinities, we attempt to find a nearest object based on
+ * CPU topology.
+ */
+
+/**
+ * alloc_cpu_rmap - allocate CPU affinity reverse-map
+ * @size: Number of objects to be mapped
+ * @flags: Allocation flags e.g. %GFP_KERNEL
+ */
+struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags)
+{
+	struct cpu_rmap *rmap;
+	unsigned int cpu;
+
+	/* This is a silly number of objects, and we use u16 indices. */
+	if (size > 0xffff)
+		return NULL;
+
+	rmap = kzalloc(sizeof(*rmap) + size * sizeof(rmap->obj[0]), flags);
+	if (!rmap)
+		return NULL;
+
+	/* Initially assign CPUs to objects on a rota, since we have
+	 * no idea where the objects are.  Use infinite distance, so
+	 * any object with known distance is preferable.  Include the
+	 * CPUs that are not present/online, since we definitely want
+	 * any newly-hotplugged CPUs to have some object assigned.
+	 */
+	for (cpu = 0; cpu < NR_CPUS; cpu++) {
+		rmap->near[cpu].index = cpu % size;
+		rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
+	}
+
+	rmap->size = size;
+	return rmap;
+}
+EXPORT_SYMBOL(alloc_cpu_rmap);
+
+/* Reevaluate nearest object for neighbours of given object at the
+ * given distance.
+ */
+static void cpu_rmap_update_neigh(struct cpu_rmap *rmap,
+				  const struct cpumask *mask,
+				  u16 index, u16 dist)
+{
+	int neigh;
+
+	for_each_cpu(neigh, mask) {
+		if (dist < rmap->near[neigh].dist) {
+			rmap->near[neigh].index = index;
+			rmap->near[neigh].dist = dist;
+		}
+	}
+}
+
+/* Reevaluate nearest object for given CPU, comparing with the given
+ * neighbours at the given distance.
+ */
+static bool cpu_rmap_copy_neigh(struct cpu_rmap *rmap, unsigned int cpu,
+				const struct cpumask *mask, u16 dist)
+{
+	int neigh;
+
+	for_each_cpu(neigh, mask) {
+		if (rmap->near[neigh].dist <= dist) {
+			rmap->near[cpu].index = rmap->near[neigh].index;
+			rmap->near[cpu].dist = dist;
+			return true;
+		}
+	}
+	return false;
+}
+
+#ifdef DEBUG
+static void debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
+{
+	unsigned index;
+	unsigned int cpu;
+
+	pr_info("cpu_rmap %p, %s:\n", rmap, prefix);
+
+	for_each_possible_cpu(cpu) {
+		index = rmap->near[cpu].index;
+		pr_info("cpu %d -> obj %u (distance %u)\n",
+			cpu, index, rmap->near[cpu].dist);
+	}
+}
+#else
+static inline void
+debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
+{
+}
+#endif
+
+/**
+ * cpu_rmap_add - add object to a rmap
+ * @rmap: CPU rmap allocated with alloc_cpu_rmap()
+ * @obj: Object to add to rmap
+ *
+ * Return index of object.
+ */
+int cpu_rmap_add(struct cpu_rmap *rmap, void *obj)
+{
+	u16 index;
+
+	BUG_ON(rmap->used >= rmap->size);
+	index = rmap->used++;
+	rmap->obj[index] = obj;
+	return index;
+}
+EXPORT_SYMBOL(cpu_rmap_add);
+
+/**
+ * cpu_rmap_update - update CPU rmap following a change of object affinity
+ * @rmap: CPU rmap to update
+ * @index: Index of object whose affinity changed
+ * @affinity: New CPU affinity of object
+ */
+void cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
+		     const struct cpumask *affinity)
+{
+	unsigned int cpu;
+
+	/* Invalidate old distances to this object */
+	for_each_online_cpu(cpu)
+		if (rmap->near[cpu].index == index)
+			rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
+
+	debug_print_rmap(rmap, "after invalidating old distances");
+
+	/* Set this as the nearest object for all CPUs in the affinity mask,
+	 * plus the following CPUs if they don't have a nearer object:
+	 * - all other threads in the same core (distance 1);
+	 * - all other cores in the same package (distance 2);
+	 * - all other packages in the same NUMA node (distance 3).
+	 */
+	for_each_cpu(cpu, affinity) {
+		rmap->near[cpu].index = index;
+		rmap->near[cpu].dist = 0;
+		cpu_rmap_update_neigh(rmap, topology_thread_cpumask(cpu),
+				      index, 1);
+		cpu_rmap_update_neigh(rmap, topology_core_cpumask(cpu),
+				      index, 2);
+		cpu_rmap_update_neigh(rmap, cpumask_of_node(cpu_to_node(cpu)),
+				      index, 3);
+	}
+
+	debug_print_rmap(rmap, "after updating neighbours");
+
+	/* Find new nearest object for any CPUs left with invalid distances */
+	for_each_online_cpu(cpu) {
+		if (!(rmap->near[cpu].index == index &&
+		      rmap->near[cpu].dist == CPU_RMAP_DIST_INF))
+			continue;
+		if (cpu_rmap_copy_neigh(rmap, cpu,
+					topology_thread_cpumask(cpu), 1))
+			continue;
+		if (cpu_rmap_copy_neigh(rmap, cpu,
+					topology_core_cpumask(cpu), 2))
+			continue;
+		if (cpu_rmap_copy_neigh(rmap, cpu,
+					cpumask_of_node(cpu_to_node(cpu)), 3))
+			continue;
+		/* We could continue into NUMA node distances, but for now
+		 * we give up.
+		 */
+	}
+
+	debug_print_rmap(rmap, "after copying neighbours");
+}
+EXPORT_SYMBOL(cpu_rmap_update);
+
+#ifdef CONFIG_GENERIC_HARDIRQS
+
+/* Glue between IRQ affinity notifiers and CPU rmaps */
+
+struct irq_glue {
+	struct irq_affinity_notify notify;
+	struct cpu_rmap *rmap;
+	u16 index;
+};
+
+/**
+ * free_irq_cpu_rmap - free a CPU affinity reverse-map used for IRQs
+ * @rmap: Reverse-map allocated with alloc_irq_cpu_map(), or %NULL
+ *
+ * Must be called in process context, before freeing the IRQs, and
+ * without holding any locks required by global workqueue items.
+ */
+void free_irq_cpu_rmap(struct cpu_rmap *rmap)
+{
+	struct irq_glue *glue;
+	u16 index;
+
+	if (!rmap)
+		return;
+
+	for (index = 0; index < rmap->used; index++) {
+		glue = rmap->obj[index];
+		irq_set_affinity_notifier(glue->notify.irq, NULL);
+	}
+	irq_run_affinity_notifiers();
+
+	kfree(rmap);
+}
+EXPORT_SYMBOL(free_irq_cpu_rmap);
+
+static void
+irq_cpu_rmap_notify(struct irq_affinity_notify *notify, const cpumask_t *mask)
+{
+	struct irq_glue *glue =
+		container_of(notify, struct irq_glue, notify);
+	cpu_rmap_update(glue->rmap, glue->index, mask);
+}
+
+static void irq_cpu_rmap_release(struct kref *ref)
+{
+	struct irq_glue *glue =
+		container_of(ref, struct irq_glue, notify.kref);
+	kfree(glue);
+}
+
+/**
+ * irq_cpu_rmap_add - add an IRQ to a CPU affinity reverse-map
+ * @rmap: The reverse-map
+ * @irq: The IRQ number
+ *
+ * This adds an IRQ affinity notifier that will update the reverse-map
+ * automatically.
+ *
+ * Must be called in process context, after the IRQ is allocated but
+ * before it is bound with request_irq().
+ */
+int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
+{
+	struct irq_glue *glue = kzalloc(sizeof(*glue), GFP_KERNEL);
+	int rc;
+
+	if (!glue)
+		return -ENOMEM;
+	glue->notify.notify = irq_cpu_rmap_notify;
+	glue->notify.release = irq_cpu_rmap_release;
+	glue->rmap = rmap;
+	glue->index = cpu_rmap_add(rmap, glue);
+	rc = irq_set_affinity_notifier(irq, &glue->notify);
+	if (rc)
+		kfree(glue);
+	return rc;
+}
+EXPORT_SYMBOL(irq_cpu_rmap_add);
+
+#endif /* CONFIG_GENERIC_HARDIRQS */
-- 
1.7.3.2



-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.