[PATCH 3.2 105/221] virtio_console: avoid config access from irq

Ben Hutchings
2015-05-05T01:34:46Z

From: "Michael S. Tsirkin" <mst@redhat.com>

commit eeb8a7e8bb123e84daeef84f5a2eab99ad2839a2 upstream.

when multiport is off, virtio console invokes config access from irq
context, config access is blocking on s390.
Fix this up by scheduling work from config irq - similar to what we do
for multiport configs.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
[bwh: Backported to 3.2:
- Adjust context
- Drop changes to virtcons_freeze()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/char/virtio_console.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -124,6 +124,7 @@ struct ports_device {
* notification
*/
struct work_struct control_work;
+ struct work_struct config_work;

struct list_head ports;

@@ -1556,10 +1557,21 @@ static void config_intr(struct virtio_de

portdev = vdev->priv;

+ if (!use_multiport(portdev))
+ schedule_work(&portdev->config_work);
+}
+
+static void config_work_handler(struct work_struct *work)
+{
+ struct ports_device *portdev;
+
+ portdev = container_of(work, struct ports_device, control_work);
if (!use_multiport(portdev)) {
+ struct virtio_device *vdev;
struct port *port;
u16 rows, cols;

+ vdev = portdev->vdev;
vdev->config->get(vdev,
offsetof(struct virtio_console_config, cols),
&cols, sizeof(u16));
@@ -1731,6 +1743,8 @@ static int __devinit virtcons_probe(stru
spin_lock_init(&portdev->ports_lock);
INIT_LIST_HEAD(&portdev->ports);

+ INIT_WORK(&portdev->config_work, &config_work_handler);
+
if (multiport) {
unsigned int nr_added_bufs;

@@ -1806,6 +1820,8 @@ static void virtcons_remove(struct virti
/* Finish up work that's lined up */
if (use_multiport(portdev))
cancel_work_sync(&portdev->control_work);
+ else
+ cancel_work_sync(&portdev->config_work);

list_for_each_entry_safe(port, port2, &portdev->ports, list)
unplug_port(port);