[PATCH v3 17/27] genirq: Bail out early in free_desc()

[Yinghai Lu <yinghai@kernel.org>]

We pre-reserve irq range for hot-added ioapic, and later only
some are used via realloc.
So during hot-remove, we need to clear bits in allocated_irqs
for both case.

Check if the irq_desc is there at first, and bail out early if
irq_desc is not allocated yet.
We can use irq_free_descs to clear allocated_irqs bits for
preserved irqs only.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
---
 kernel/irq/irqdesc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index b48f65b..32f099e 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -170,6 +170,9 @@ static void free_desc(unsigned int irq)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
 
+	if (!desc)
+		return;
+
 	unregister_irq_proc(irq, desc);
 
 	mutex_lock(&sparse_irq_lock);
-- 
1.8.1.4