[ARM] Fix Neponset IRQ handling
While testing the genirq code on ARM, a condition was found whereby
the Neponset IRQ handler was being re-entered, causing the system
to deadlock.
Under the ARM IRQ code, this would not have been a visible problem
because the "simple" IRQ handling had no re-entrancy protection.
Resolve this by acknowledging the parent interrupt after we mask it
when we are going to handle one of our "special" level-based sources
(from ethernet or USAR chip.)
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mach-sa1100/neponset.c b/arch/arm/mach-sa1100/neponset.c
index 9e02bc3..af6d277 100644
--- a/arch/arm/mach-sa1100/neponset.c
+++ b/arch/arm/mach-sa1100/neponset.c
@@ -59,6 +59,14 @@
if (irr & (IRR_ETHERNET | IRR_USAR)) {
desc->chip->mask(irq);
+ /*
+ * Ack the interrupt now to prevent re-entering
+ * this neponset handler. Again, this is safe
+ * since we'll check the IRR register prior to
+ * leaving.
+ */
+ desc->chip->ack(irq);
+
if (irr & IRR_ETHERNET) {
d = irq_desc + IRQ_NEPONSET_SMC9196;
desc_handle_irq(IRQ_NEPONSET_SMC9196, d, regs);