genirq: Use the correct variable for note_interrupt

note_interrupt wants to be called with the combined result of all
handlers called, not with the last one. If it's a shared interrupt
then the last handler might return IRQ_NONE often enough to trigger
the spurious dectector which turns off a perfectly fine working
interrupt line. Bug was introduced in commit 1277a532(genirq: Simplify
handle_irq_event()).

Yes, I really messed up there. First the variable ret should not have
been named differently to avoid similarity with retval. Second it
should have been declared in the do {} loop.

Rename it to res and move it into the do {} loop and vanish under a
huge brown paperbag.

Reported-bisected-tested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 9 insertions, 7 deletions

diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index cb62e2d0df4e..e099e9e9de0b 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -54,24 +54,26 @@ static void warn_no_thread(unsigned int irq, struct irqaction *action)
 irqreturn_t
 handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
 {
-        irqreturn_t ret, retval = IRQ_NONE;
+        irqreturn_t retval = IRQ_NONE;
         unsigned int random = 0, irq = desc->irq_data.irq;
 
         do {
+                irqreturn_t res;
+
                 trace_irq_handler_entry(irq, action);
-                ret = action->handler(irq, action->dev_id);
-                trace_irq_handler_exit(irq, action, ret);
+                res = action->handler(irq, action->dev_id);
+                trace_irq_handler_exit(irq, action, res);
 
                 if (WARN_ON_ONCE(!irqs_disabled()))
                         local_irq_disable();
 
-                switch (ret) {
+                switch (res) {
                 case IRQ_WAKE_THREAD:
                         /*
                          * Set result to handled so the spurious check
                          * does not trigger.
                          */
-                        ret = IRQ_HANDLED;
+                        res = IRQ_HANDLED;
 
                         /*
                          * Catch drivers which return WAKE_THREAD but
@@ -105,7 +107,7 @@ handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
                         break;
                 }
 
-                retval |= ret;
+                retval |= res;
                 action = action->next;
         } while (action);
 
@@ -113,7 +115,7 @@ handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
                 add_interrupt_randomness(irq);
 
         if (!noirqdebug)
-                note_interrupt(irq, desc, ret);
+                note_interrupt(irq, desc, retval);
         return retval;
 }