[RFC,1/3] irq: Allow multiple clients to register for irq affinity notification

diff --git a/drivers/infiniband/hw/qib/qib_iba7322.c b/drivers/infiniband/hw/qib/qib_iba7322.c
index a7eb325..62cb77d 100644
--- a/drivers/infiniband/hw/qib/qib_iba7322.c
+++ b/drivers/infiniband/hw/qib/qib_iba7322.c
@@ -3345,9 +3345,7 @@  static void reset_dca_notifier(struct qib_devdata *dd, struct qib_msix_entry *m)
 		"Disabling notifier on HCA %d irq %d\n",
 		dd->unit,
 		m->msix.vector);
-	irq_set_affinity_notifier(
-		m->msix.vector,
-		NULL);
+	irq_release_affinity_notifier(m->notifier);
 	m->notifier = NULL;
 }
 
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 698ad05..c1e227c 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -203,7 +203,7 @@  static inline int check_wakeup_irqs(void) { return 0; }
  * 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
+ * @list:		Add to the notifier list, 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
@@ -214,7 +214,7 @@  static inline int check_wakeup_irqs(void) { return 0; }
 struct irq_affinity_notify {
 	unsigned int irq;
 	struct kref kref;
-	struct work_struct work;
+	struct list_head list;
 	void (*notify)(struct irq_affinity_notify *, const cpumask_t *mask);
 	void (*release)(struct kref *ref);
 };
@@ -265,6 +265,8 @@  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);
 
+extern int
+irq_release_affinity_notifier(struct irq_affinity_notify *notify);
 #else /* CONFIG_SMP */
 
 static inline int irq_set_affinity(unsigned int irq, const struct cpumask *m)
@@ -295,6 +297,12 @@  irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
 {
 	return 0;
 }
+
+static inline int
+irq_release_affinity_notifier(struct irq_affinity_notify *notify)
+{
+	return 0;
+}
 #endif /* CONFIG_SMP */
 
 /*
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 62af592..2634a48 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -20,6 +20,7 @@ 
 #include <linux/errno.h>
 #include <linux/topology.h>
 #include <linux/wait.h>
+#include <linux/list.h>
 
 #include <asm/irq.h>
 #include <asm/ptrace.h>
diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index 472c021..10d8155 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -31,7 +31,7 @@  struct irq_desc;
  * @threads_handled_last: comparator field for deferred spurious detection of theraded handlers
  * @lock:		locking for SMP
  * @affinity_hint:	hint to user space for preferred irq affinity
- * @affinity_notify:	context for notification of affinity changes
+ * @affinity_notify:	list head for notification of affinity changes
  * @pending_mask:	pending rebalanced interrupts
  * @threads_oneshot:	bitfield to handle shared oneshot threads
  * @threads_active:	number of irqaction threads currently running
@@ -60,7 +60,8 @@  struct irq_desc {
 	struct cpumask		*percpu_enabled;
 #ifdef CONFIG_SMP
 	const struct cpumask	*affinity_hint;
-	struct irq_affinity_notify *affinity_notify;
+	struct list_head	affinity_notify;
+	struct work_struct	affinity_work;
 #ifdef CONFIG_GENERIC_PENDING_IRQ
 	cpumask_var_t		pending_mask;
 #endif
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 1487a12..c95e1f3 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -91,6 +91,7 @@  static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node,
 	for_each_possible_cpu(cpu)
 		*per_cpu_ptr(desc->kstat_irqs, cpu) = 0;
 	desc_smp_init(desc, node);
+	INIT_LIST_HEAD(&desc->affinity_notify);
 }
 
 int nr_irqs = NR_IRQS;
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 88657d7..de5008b4 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -209,10 +209,9 @@  int irq_set_affinity_locked(struct irq_data *data, const struct cpumask *mask,
 		irq_copy_pending(desc, mask);
 	}
 
-	if (desc->affinity_notify) {
-		kref_get(&desc->affinity_notify->kref);
-		schedule_work(&desc->affinity_notify->work);
-	}
+	if (!list_empty(&desc->affinity_notify))
+		schedule_work(&desc->affinity_work);
+
 	irqd_set(data, IRQD_AFFINITY_SET);
 
 	return ret;
@@ -248,14 +247,14 @@  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);
+	struct irq_desc *desc =
+			container_of(work, struct irq_desc, affinity_work);
 	cpumask_var_t cpumask;
 	unsigned long flags;
+	struct irq_affinity_notify *notify;
 
 	if (!desc || !alloc_cpumask_var(&cpumask, GFP_KERNEL))
-		goto out;
+		return;
 
 	raw_spin_lock_irqsave(&desc->lock, flags);
 	if (irq_move_pending(&desc->irq_data))
@@ -264,11 +263,14 @@  static void irq_affinity_notify(struct work_struct *work)
 		cpumask_copy(cpumask, desc->irq_data.affinity);
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 
-	notify->notify(notify, cpumask);
+	list_for_each_entry(notify, &desc->affinity_notify, list) {
+		if (!kref_get_unless_zero(&notify->kref))
+			continue;
+		notify->notify(notify, cpumask);
+		kref_put(&notify->kref, notify->release);
+	}
 
 	free_cpumask_var(cpumask);
-out:
-	kref_put(&notify->kref, notify->release);
 }
 
 /**
@@ -286,8 +288,6 @@  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();
@@ -295,25 +295,37 @@  irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
 	if (!desc)
 		return -EINVAL;
 
-	/* Complete initialisation of *notify */
-	if (notify) {
-		notify->irq = irq;
-		kref_init(&notify->kref);
-		INIT_WORK(&notify->work, irq_affinity_notify);
+	if (!notify) {
+		WARN("%s: Use irq_release_affinity_notifier function instead.\n",
+				__func__);
+		return -EINVAL;
 	}
 
-	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);
+	notify->irq = irq;
+	kref_init(&notify->kref);
+	INIT_LIST_HEAD(&notify->list);
+	list_add(&desc->affinity_notify, &notify->list);
 
 	return 0;
 }
 EXPORT_SYMBOL_GPL(irq_set_affinity_notifier);
 
+/**
+ *	irq_release_affinity_notifier - Remove us from notifications
+ *	@notify: Context for notification
+ */
+int irq_release_affinity_notifier(struct irq_affinity_notify *notify)
+{
+	if (!notify)
+		return -EINVAL;
+
+	list_del(&notify->list);
+	kref_put(&notify->kref, notify->release);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(irq_release_affinity_notifier);
+
 #ifndef CONFIG_AUTO_IRQ_AFFINITY
 /*
  * Generic version of the affinity autoselector.
@@ -348,6 +360,8 @@  setup_affinity(unsigned int irq, struct irq_desc *desc, struct cpumask *mask)
 		if (cpumask_intersects(mask, nodemask))
 			cpumask_and(mask, mask, nodemask);
 	}
+	INIT_LIST_HEAD(&desc->affinity_notify);
+	INIT_WORK(&desc->affinity_work, irq_affinity_notify);
 	irq_do_set_affinity(&desc->irq_data, mask, false);
 	return 0;
 }
@@ -1418,11 +1432,6 @@  void free_irq(unsigned int irq, void *dev_id)
 	if (!desc || WARN_ON(irq_settings_is_per_cpu_devid(desc)))
 		return;
 
-#ifdef CONFIG_SMP
-	if (WARN_ON(desc->affinity_notify))
-		desc->affinity_notify = NULL;
-#endif
-
 	chip_bus_lock(desc);
 	kfree(__free_irq(irq, dev_id));
 	chip_bus_sync_unlock(desc);
diff --git a/lib/cpu_rmap.c b/lib/cpu_rmap.c
index 4f134d8..0c8da50 100644
--- a/lib/cpu_rmap.c
+++ b/lib/cpu_rmap.c
@@ -235,7 +235,7 @@  void free_irq_cpu_rmap(struct cpu_rmap *rmap)
 
 	for (index = 0; index < rmap->used; index++) {
 		glue = rmap->obj[index];
-		irq_set_affinity_notifier(glue->notify.irq, NULL);
+		irq_release_affinity_notifier(&glue->notify);
 	}
 
 	cpu_rmap_put(rmap);