[PATCH] irq/irq_sim: add locking

[Bartosz Golaszewski]

Two threads can try to fire the irq_sim with different offsets and will
end up fighting for the irq_work asignment. To fix it: add a mutex and
lock it before firing.

Suggested-by: Uwe Kleine-KÃnig <u.kleine-koenig@xxxxxxxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx>
---
 include/linux/irq_sim.h | 1 +
 kernel/irq/irq_sim.c    | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/linux/irq_sim.h b/include/linux/irq_sim.h
index 630a57e55db6..676bfa0c12b9 100644
--- a/include/linux/irq_sim.h
+++ b/include/linux/irq_sim.h
@@ -29,6 +29,7 @@ struct irq_sim {
 	int			irq_base;
 	unsigned int		irq_count;
 	struct irq_sim_irq_ctx	*irqs;
+	struct mutex		lock;
 };
 
 int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs);
diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
index dd20d0d528d4..2f06c24b51a0 100644
--- a/kernel/irq/irq_sim.c
+++ b/kernel/irq/irq_sim.c
@@ -74,6 +74,7 @@ int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
 	}
 
 	init_irq_work(&sim->work_ctx.work, irq_sim_handle_irq);
+	mutex_init(&sim->lock);
 	sim->irq_count = num_irqs;
 
 	return sim->irq_base;
@@ -142,10 +143,14 @@ EXPORT_SYMBOL_GPL(devm_irq_sim_init);
  */
 void irq_sim_fire(struct irq_sim *sim, unsigned int offset)
 {
+	mutex_lock(&sim->lock);
+
 	if (sim->irqs[offset].enabled) {
 		sim->work_ctx.irq = irq_sim_irqnum(sim, offset);
 		irq_work_queue(&sim->work_ctx.work);
 	}
+
+	mutex_unlock(&sim->lock);
 }
 EXPORT_SYMBOL_GPL(irq_sim_fire);
 
-- 
2.19.1