[PATCH v3 4/6] um: virtio_uml: implement synchronize_cbs()

[Karl Mehltretter <kmehltretter@gmail.com>]

virtio_uml invokes virtqueue callbacks from vu_interrupt() and
vu_req_interrupt(), which share vu_dev->irq. The core's
synchronize_rcu() fallback already covers these IRQ handlers.

Implement synchronize_cbs() with synchronize_irq() to synchronize with
that IRQ instead of waiting for an RCU grace period.

Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
 arch/um/drivers/virtio_uml.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c
index 7425a8548141..1f2e62e29a27 100644
--- a/arch/um/drivers/virtio_uml.c
+++ b/arch/um/drivers/virtio_uml.c
@@ -20,6 +20,7 @@
  *
  * Based on Virtio MMIO driver by Pawel Moll, copyright 2011-2014, ARM Ltd.
  */
+#include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
@@ -869,6 +870,14 @@ static void vu_reset(struct virtio_device *vdev)
 	vu_dev->status = 0;
 }
 
+static void vu_synchronize_cbs(struct virtio_device *vdev)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	if (vu_dev->irq != UM_IRQ_ALLOC)
+		synchronize_irq(vu_dev->irq);
+}
+
 static void vu_del_vq(struct virtqueue *vq)
 {
 	struct virtio_uml_vq_info *info = vq->priv;
@@ -1121,6 +1130,7 @@ static const struct virtio_config_ops virtio_uml_config_ops = {
 	.reset = vu_reset,
 	.find_vqs = vu_find_vqs,
 	.del_vqs = vu_del_vqs,
+	.synchronize_cbs = vu_synchronize_cbs,
 	.get_features = vu_get_features,
 	.finalize_features = vu_finalize_features,
 	.bus_name = vu_bus_name,
-- 
2.39.5 (Apple Git-154)