genirq: Add CPU mask affinity hint

This patch adds a cpumask affinity hint to the irq_desc structure,
along with a registration function and a read-only proc entry for each
interrupt.

This affinity_hint handle for each interrupt can be used by underlying
drivers that need a better mechanism to control interrupt affinity.
The underlying driver can register a cpumask for the interrupt, which
will allow the driver to provide the CPU mask for the interrupt to
anything that requests it.  The intent is to extend the userspace
daemon, irqbalance, to help hint to it a preferred CPU mask to balance
the interrupt into.

[ tglx: Fixed compile warnings, added WARN_ON, made SMP only ]

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Cc: davem@davemloft.net
Cc: arjan@linux.jf.intel.com
Cc: bhutchings@solarflare.com
LKML-Reference: <20100430214445.3992.41647.stgit@ppwaskie-hc2.jf.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 707ab122e2e6..c03243ad84b4 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -195,6 +195,7 @@ struct irq_desc {
         raw_spinlock_t          lock;
 #ifdef CONFIG_SMP
         cpumask_var_t           affinity;
+        const struct cpumask    *affinity_hint;
         unsigned int            node;
 #ifdef CONFIG_GENERIC_PENDING_IRQ
         cpumask_var_t           pending_mask;