On 21/11/13 19:31, Michael S. Tsirkin wrote:
On Thu, Nov 21, 2013 at 06:12:21PM +0100, Heinz Graalfs wrote:
On 21/11/13 16:15, Michael S. Tsirkin wrote:
On Thu, Nov 21, 2013 at 03:45:33PM +0100, Heinz Graalfs wrote:
virtio_ccw's notify() callback for the common IO layer invokes
virtio_driver's notify() callback to pass-on information to a
backend driver if an online device disappeared.
Signed-off-by: Heinz Graalfs <graalfs@xxxxxxxxxxxxxxxxxx>
simple question: is this serialized with device removal?
If this races with removal we have a problem.
notify and remove callbacks are not serialized.
Additional processing in the notify handler is now locked by the queue lock.
If remove is already active (e.g. driver unregister) and performing
its cleanup (via virtblk_remove), we should definitely perform the
(locked) request queue processing in notify (little later), because
if a notify comes in, the device is GONE (not going away). Earlier
triggered cleanup processing is about to fail anyway.
I don't get it. It's possible nothing is in queue
or everything timed out.
Then this notify will address freed memory.
I'm starting to think the right solution is to pass
a flag to remove: bool surprize_removal.
Then you will cleanly set flags before removing the device.
No new callbacks and no races.
OK, I will send a v3 RFC.
However, I suppose we will always have some kind of 'race' wrt this
weird scenario, ending up in different kind of hang situations.
---
drivers/s390/kvm/virtio_ccw.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index 35b9aaa..682f688 100644
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -27,6 +27,7 @@
#include <linux/module.h>
#include <linux/io.h>
#include <linux/kvm_para.h>
+#include <linux/notifier.h>
#include <asm/setup.h>
#include <asm/irq.h>
#include <asm/cio.h>
@@ -1064,8 +1065,18 @@ out_free:
static int virtio_ccw_cio_notify(struct ccw_device *cdev, int event)
{
- /* TODO: Check whether we need special handling here. */
- return 0;
+ int rc;
+ struct virtio_ccw_device *vcdev = dev_get_drvdata(&cdev->dev);
+
+ switch (event) {
+ case CIO_GONE:
+ rc = notify_virtio_device(&vcdev->vdev, VDEV_GONE);
+ break;
+ default:
+ rc = NOTIFY_DONE;
+ break;
+ }
+ return rc;
}
static struct ccw_device_id virtio_ids[] = {
--
1.8.3.1
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