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Date: Wed, 13 Dec 2006 14:53:40 +0100
From: Arjan van de Ven <arjan@...ux.intel.com>
To: ebiederm@...ssion.com, mingo@...e.hu
Cc: linux-kernel@...r.kernel.org
Subject: [patch] Add allowed_affinity to the irq_desc to make it possible
to have restricted irqs
[due to a broken libata in current -git I've not been able to test this patch enough]
This patch adds an "allowed_affinity" mask to each interrupt, in addition to the
existing actual affinity mask. In addition this new mask is exported to userspace
in a similar way as the actual affinity is exported. (this is so that irqbalance
can find out about the restriction and take it into account)
The purpose for having this mask is to allow for the situation where interrupts
just can't or shouldn't go to all cpus; one example is the "per cpu" IRQ thing
that powerpc and others have. Another soon-to-come example is MSIX devices that
can generate a different MSI interrupt for each cpu; in that case the MSI needs to
be strictly constrained to it's designated cpu.
Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
---
include/linux/irq.h | 2 ++
kernel/irq/chip.c | 1 +
kernel/irq/handle.c | 3 ++-
kernel/irq/manage.c | 5 ++++-
kernel/irq/proc.c | 27 +++++++++++++++++++++++++++
5 files changed, 36 insertions(+), 2 deletions(-)
Index: linux-2.6/include/linux/irq.h
===================================================================
--- linux-2.6.orig/include/linux/irq.h
+++ linux-2.6/include/linux/irq.h
@@ -137,6 +137,7 @@ struct irq_chip {
* @irqs_unhandled: stats field for spurious unhandled interrupts
* @lock: locking for SMP
* @affinity: IRQ affinity on SMP
+ * @allowed_affinity The allowed affinity for this IRQ
* @cpu: cpu index useful for balancing
* @pending_mask: pending rebalanced interrupts
* @dir: /proc/irq/ procfs entry
@@ -160,6 +161,7 @@ struct irq_desc {
spinlock_t lock;
#ifdef CONFIG_SMP
cpumask_t affinity;
+ cpumask_t allowed_affinity;
unsigned int cpu;
#endif
#if defined(CONFIG_GENERIC_PENDING_IRQ) || defined(CONFIG_IRQBALANCE)
Index: linux-2.6/kernel/irq/chip.c
===================================================================
--- linux-2.6.orig/kernel/irq/chip.c
+++ linux-2.6/kernel/irq/chip.c
@@ -46,6 +46,7 @@ void dynamic_irq_init(unsigned int irq)
desc->irqs_unhandled = 0;
#ifdef CONFIG_SMP
desc->affinity = CPU_MASK_ALL;
+ desc->allowed_affinity = CPU_MASK_ALL;
#endif
spin_unlock_irqrestore(&desc->lock, flags);
}
Index: linux-2.6/kernel/irq/handle.c
===================================================================
--- linux-2.6.orig/kernel/irq/handle.c
+++ linux-2.6/kernel/irq/handle.c
@@ -56,7 +56,8 @@ struct irq_desc irq_desc[NR_IRQS] __cach
.depth = 1,
.lock = __SPIN_LOCK_UNLOCKED(irq_desc->lock),
#ifdef CONFIG_SMP
- .affinity = CPU_MASK_ALL
+ .affinity = CPU_MASK_ALL,
+ .allowed_affinity = CPU_MASK_ALL
#endif
}
};
Index: linux-2.6/kernel/irq/manage.c
===================================================================
--- linux-2.6.orig/kernel/irq/manage.c
+++ linux-2.6/kernel/irq/manage.c
@@ -278,8 +278,13 @@ int setup_irq(unsigned int irq, struct i
*p = new;
#if defined(CONFIG_IRQ_PER_CPU)
- if (new->flags & IRQF_PERCPU)
+ if (new->flags & IRQF_PERCPU) {
desc->status |= IRQ_PER_CPU;
+ /* don't allow affinity to be set for per cpu interrupts */
+#ifdef CONFIG_SMP
+ desc->allowed_affinity = CPU_MASK_NONE;
+#endif
+ }
#endif
if (!shared) {
irq_chip_set_defaults(desc->chip);
Index: linux-2.6/kernel/irq/proc.c
===================================================================
--- linux-2.6.orig/kernel/irq/proc.c
+++ linux-2.6/kernel/irq/proc.c
@@ -47,6 +47,20 @@ static int irq_affinity_read_proc(char *
return len;
}
+
+static int irq_affinity_read_allowed_proc(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len = cpumask_scnprintf(page, count, irq_desc[(long)data].allowed_affinity);
+
+ if (count - len < 2)
+ return -EINVAL;
+ len += sprintf(page + len, "\n");
+ return len;
+}
+
+
+
int no_irq_affinity;
static int irq_affinity_write_proc(struct file *file, const char __user *buffer,
unsigned long count, void *data)
@@ -62,6 +76,9 @@ static int irq_affinity_write_proc(struc
if (err)
return err;
+ /* mask off the allowed_affinity mask to only leave legal cpus */
+ cpus_and(new_value, new_value, irq_desc[irq].allowed_affinity);
+
/*
* Do not allow disabling IRQs completely - it's a too easy
* way to make the system unusable accidentally :-) At least
@@ -141,6 +158,16 @@ void register_irq_proc(unsigned int irq)
entry->read_proc = irq_affinity_read_proc;
entry->write_proc = irq_affinity_write_proc;
}
+
+ /* create /proc/irq/<irq>/smp_affinity */
+ entry = create_proc_entry("allowed_affinity", 0400, irq_desc[irq].dir);
+
+ if (entry) {
+ entry->nlink = 1;
+ entry->data = (void *)(long)irq;
+ entry->read_proc = irq_affinity_read_allowed_proc;
+ }
+
}
#endif
}
-
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