genirq: Sanitize state handling in check_irq_resend()

The code sets IRQS_REPLAY unconditionally whether the resend happens or
not. That doesn't have bad side effects right now, but inconsistent state
is always a latent source of problems.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lkml.kernel.org/r/20200306130623.882129117@linutronix.de

diff --git a/kernel/irq/resend.c b/kernel/irq/resend.c
index a21fc4e..bef72dc 100644 (file)
--- a/kernel/irq/resend.c
+++ b/kernel/irq/resend.c
@@ -93,6 +93,8 @@ static int irq_sw_resend(struct irq_desc *desc)
  */
 int check_irq_resend(struct irq_desc *desc)
 {
+       int err = 0;
+
        /*
         * We do not resend level type interrupts. Level type interrupts
         * are resent by hardware when they are still active. Clear the
@@ -106,13 +108,17 @@ int check_irq_resend(struct irq_desc *desc)
        if (desc->istate & IRQS_REPLAY)
                return -EBUSY;
 
-       if (desc->istate & IRQS_PENDING) {
-               desc->istate &= ~IRQS_PENDING;
-               desc->istate |= IRQS_REPLAY;
+       if (!(desc->istate & IRQS_PENDING))
+               return 0;
 
-               if (!desc->irq_data.chip->irq_retrigger ||
-                   !desc->irq_data.chip->irq_retrigger(&desc->irq_data))
-                   return irq_sw_resend(desc);
-       }
-       return 0;
+       desc->istate &= ~IRQS_PENDING;
+
+       if (!desc->irq_data.chip->irq_retrigger ||
+           !desc->irq_data.chip->irq_retrigger(&desc->irq_data))
+               err = irq_sw_resend(desc);
+
+       /* If the retrigger was successfull, mark it with the REPLAY bit */
+       if (!err)
+               desc->istate |= IRQS_REPLAY;
+       return err;
 }