[PATCH] IRQ: Validate irq_ack function pointer before calling it

[Yang, Fei]

handle_edge_irq doesn't validate function pointer irq_ack
before calling it. We need to check the pointer for NULL or the
drivers have to implement irq_ack even an empty one. I think the
former is better in case driver doesn't really need irq_ack.

Signed-off-by: Fei Yang <fei.yang@xxxxxxxxx>
Acked-by: Alan Cox <alan@xxxxxxxxxxxxxxx>
---
kernel/irq/chip.c |    3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index dc5114b..12f9550 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -448,7 +448,8 @@ handle_edge_irq(unsigned int irq, struct irq_desc *desc)
    kstat_incr_irqs_this_cpu(irq, desc);

     /* Start handling the irq */
-    desc->irq_data.chip->irq_ack(&desc->irq_data);
+    if (desc->irq_data.chip->irq_ack)
+          desc->irq_data.chip->irq_ack(&desc->irq_data);

     do {
          if (unlikely(!desc->action)) {
-- 
1.7.0.4

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