[PATCH 3.2 084/152] virtio_pci: document why we defer kfree

[Ben Hutchings]

3.2.67-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>

commit a1eb03f546d651a8f39c7d0692b1f7f5b4e7e3cd upstream.

The reason we defer kfree until release function is because it's a
general rule for kobjects: kfree of the reference counter itself is only
legal in the release function.

Previous patch didn't make this clear, document this in code.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/virtio/virtio_pci.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -615,6 +615,9 @@ static void virtio_pci_release_dev(struc
 	struct virtio_device *vdev = dev_to_virtio(_d);
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 
+	/* As struct device is a kobject, it's not safe to
+	 * free the memory (including the reference counter itself)
+	 * until it's release callback. */
 	kfree(vp_dev);
 }
 

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