genirq: Sanitize state handling in check_irq_resend()

task #29600094

commit da90921acc62c71d27729ae211ccfda5370bf75b upstream.
Backport summary: for 4.19 kernel ICX PCIe Gen4 support.

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: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NMarc Zyngier <maz@kernel.org>
Link: https://lkml.kernel.org/r/20200306130623.882129117@linutronix.de

(cherry picked from commit da90921acc62c71d27729ae211ccfda5370bf75b)
Signed-off-by: NEthan Zhao <haifeng.zhao@intel.com>
Signed-off-by: NArtie Ding <artie.ding@linux.alibaba.com>
Acked-by: NCaspar Zhang <caspar@linux.alibaba.com>

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;
 }