[PATCH v2 2/5] irqchip/mips-gic: Fix recursive acquisition of gic_lock in gic_set_affinity()

["Benoît Monin" <benoit.monin@bootlin.com>]

Commit 322a90638768 ("irqchip/mips-gic: Multi-cluster support")
made gic_set_affinity() call gic_set_type() when an interrupt's
affinity is moved between clusters. gic_set_type() takes gic_lock with
raw_spin_lock_irqsave(), but gic_set_affinity() holds gic_lock at that
point, so the same raw spinlock is acquired twice, triggering a deadlock.

Split gic_set_type() into a gic_set_type_locked() helper that assumes
gic_lock is already held. gic_set_type() takes gic_lock and calls the
helper, and gic_set_affinity() calls gic_set_type_locked() directly,
since it already holds gic_lock.

Fixes: 322a90638768 ("irqchip/mips-gic: Multi-cluster support")
Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>
---
 drivers/irqchip/irq-mips-gic.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index 3b31cbcbed6f..f2ae60d39d66 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -297,14 +297,14 @@ static void gic_ack_irq(struct irq_data *d)
 	}
 }
 
-static int gic_set_type(struct irq_data *d, unsigned int type)
+static int gic_set_type_locked(struct irq_data *d, unsigned int type)
 {
 	unsigned int irq, pol, trig, dual;
-	unsigned long flags;
+
+	lockdep_assert_held(&gic_lock);
 
 	irq = GIC_HWIRQ_TO_SHARED(d->hwirq);
 
-	raw_spin_lock_irqsave(&gic_lock, flags);
 	switch (type & IRQ_TYPE_SENSE_MASK) {
 	case IRQ_TYPE_EDGE_FALLING:
 		pol = GIC_POL_FALLING_EDGE;
@@ -351,11 +351,16 @@ static int gic_set_type(struct irq_data *d, unsigned int type)
 	else
 		irq_set_chip_handler_name_locked(d, &gic_level_irq_controller,
 						 handle_level_irq, NULL);
-	raw_spin_unlock_irqrestore(&gic_lock, flags);
 
 	return 0;
 }
 
+static int gic_set_type(struct irq_data *d, unsigned int type)
+{
+	guard(raw_spinlock_irqsave)(&gic_lock);
+	return gic_set_type_locked(d, type);
+}
+
 #ifdef CONFIG_SMP
 static int gic_set_affinity(struct irq_data *d, const struct cpumask *cpumask,
 			    bool force)
@@ -407,7 +412,7 @@ static int gic_set_affinity(struct irq_data *d, const struct cpumask *cpumask,
 	 * trigger type in the new cluster.
 	 */
 	if (cl != old_cl)
-		gic_set_type(d, irqd_get_trigger_type(d));
+		gic_set_type_locked(d, irqd_get_trigger_type(d));
 
 	/* Route the interrupt to its new VP(E) */
 	if (gic_irq_lock_cluster(d)) {

-- 
2.55.0