[PATCH v3 5/6] platform/mellanox: mlxbf-tmfifo: implement synchronize_cbs()

[Karl Mehltretter <kmehltretter@gmail.com>]

TmFIFO invokes virtqueue callbacks from its FIFO work item under
spin_lock_irqsave(). The core's synchronize_rcu() fallback already
covers those sections.

Implement synchronize_cbs() using the existing per-direction locks
instead of waiting for an RCU grace period. fifo->spin_lock[0] covers
the transmit callbacks, including the callback from the timeout
handler. fifo->spin_lock[1] covers the receive callbacks. Take and
release each lock in turn to synchronize with callbacks running
under that lock.

Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
 drivers/platform/mellanox/mlxbf-tmfifo.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c
index 3c6408581373..664bec20a7ae 100644
--- a/drivers/platform/mellanox/mlxbf-tmfifo.c
+++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
@@ -1135,6 +1135,20 @@ static void mlxbf_tmfifo_virtio_reset(struct virtio_device *vdev)
 	tm_vdev->status = 0;
 }
 
+/* Synchronize with callbacks running in the FIFO work item. */
+static void mlxbf_tmfifo_virtio_synchronize_cbs(struct virtio_device *vdev)
+{
+	struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);
+	struct mlxbf_tmfifo *fifo = tm_vdev->vrings[0].fifo;
+	unsigned long flags;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(fifo->spin_lock); i++) {
+		spin_lock_irqsave(&fifo->spin_lock[i], flags);
+		spin_unlock_irqrestore(&fifo->spin_lock[i], flags);
+	}
+}
+
 /* Read the value of a configuration field. */
 static void mlxbf_tmfifo_virtio_get(struct virtio_device *vdev,
 				    unsigned int offset,
@@ -1179,6 +1193,7 @@ static const struct virtio_config_ops mlxbf_tmfifo_virtio_config_ops = {
 	.find_vqs = mlxbf_tmfifo_virtio_find_vqs,
 	.del_vqs = mlxbf_tmfifo_virtio_del_vqs,
 	.reset = mlxbf_tmfifo_virtio_reset,
+	.synchronize_cbs = mlxbf_tmfifo_virtio_synchronize_cbs,
 	.set_status = mlxbf_tmfifo_virtio_set_status,
 	.get_status = mlxbf_tmfifo_virtio_get_status,
 	.get = mlxbf_tmfifo_virtio_get,
-- 
2.39.5 (Apple Git-154)