linux-kernel - [PATCH] genirq: Use irqd_get_trigger_type to compare the trigger type for shared IRQs

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Message-Id: <20170415100831.17073-1-hdegoede@redhat.com>
Date:   Sat, 15 Apr 2017 12:08:31 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Marc Zyngier <marc.zyngier@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] genirq: Use irqd_get_trigger_type to compare the trigger type for shared IRQs

When requesting a shared irq with IRQF_TRIGGER_NONE then the irqaction
flags get filled with the trigger type from the irq_data:

        if (!(new->flags & IRQF_TRIGGER_MASK))
                new->flags |= irqd_get_trigger_type(&desc->irq_data);

On the first setup_irq() the trigger type in irq_data is NONE when the
above code executes, then the irq is started up for the first time and
then the actual trigger type gets established, but that's too late to fix
up new->flags.

When then a second user of the irq requests the irq with IRQF_TRIGGER_NONE
its irqaction's triggertype gets set to the actual trigger type and the
following check fails:

        if (!((old->flags ^ new->flags) & IRQF_TRIGGER_MASK))

Resulting in the request_irq failing with -EBUSY even though both
users requested the irq with IRQF_SHARED | IRQF_TRIGGER_NONE

This commit fixes this by comparing the new irqaction's trigger type
to the trigger type stored in the irq_data which correctly reflects
the actual trigger type being used for the irq.

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Hans de Goede <hdegoede@...hat.com>
---
 kernel/irq/manage.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index a4afe5c..d63e91f 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1212,8 +1212,10 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		 * set the trigger type must match. Also all must
 		 * agree on ONESHOT.
 		 */
+		unsigned int oldtype = irqd_get_trigger_type(&desc->irq_data);
+
 		if (!((old->flags & new->flags) & IRQF_SHARED) ||
-		    ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK) ||
+		    (oldtype != (new->flags & IRQF_TRIGGER_MASK)) ||
 		    ((old->flags ^ new->flags) & IRQF_ONESHOT))
 			goto mismatch;
 
-- 
2.9.3