linux-kernel - [patch 5/7] genirq: Sanitize state handling in check_irq

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Message-Id: <20200306130623.882129117@linutronix.de>
Date:   Fri, 06 Mar 2020 14:03:46 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Marc Zyngier <maz@...nel.org>, x86@...nel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        Keith Busch <kbusch@...nel.org>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: [patch 5/7] 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@...utronix.de>
---
 kernel/irq/resend.c |   22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

--- a/kernel/irq/resend.c
+++ b/kernel/irq/resend.c
@@ -93,6 +93,8 @@ static int irq_sw_resend(struct irq_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 *de
 	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;
 }