There is a race condition in virtscsi_handle_event, when many device
hotplug/unplug events flush in quickly.
The scsi_remove_device in virtscsi_handle_transport_reset may trigger
the BUG_ON in scsi_target_reap, because the state is altered behind it,
probably by scsi_scan_host of another event. I'm able to reproduce it by
repeatedly plugging and unplugging a scsi disk with the same lun number.
To make is safe, the mutex added in struct virtio_scsi is held in
virtscsi_handle_event, so that all the events are processed in a
synchronized way. With this lock, the panic goes away.
Signed-off-by: Fam Zheng <famz@xxxxxxxxxx>
---
drivers/scsi/virtio_scsi.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index c52bb5d..7f194d4 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -110,6 +110,9 @@ struct virtio_scsi {
/* CPU hotplug notifier */
struct notifier_block nb;
+ /* Protect the hotplug/unplug event handling */
+ struct mutex scan_lock;
+
/* Protected by event_vq lock */
bool stop_events;
@@ -377,6 +380,7 @@ static void virtscsi_handle_event(struct work_struct *work)
struct virtio_scsi *vscsi = event_node->vscsi;
struct virtio_scsi_event *event = &event_node->event;
+ mutex_lock(&vscsi->scan_lock);
if (event->event &
cpu_to_virtio32(vscsi->vdev, VIRTIO_SCSI_T_EVENTS_MISSED)) {
event->event &= ~cpu_to_virtio32(vscsi->vdev,
@@ -397,6 +401,7 @@ static void virtscsi_handle_event(struct work_struct *work)
pr_err("Unsupport virtio scsi event %x\n", event->event);
}
virtscsi_kick_event(vscsi, event_node);
+ mutex_unlock(&vscsi->scan_lock);
}
static void virtscsi_complete_event(struct virtio_scsi *vscsi, void *buf)
@@ -894,6 +899,7 @@ static int virtscsi_init(struct virtio_device *vdev,
const char **names;
struct virtqueue **vqs;
+ mutex_init(&vscsi->scan_lock);
num_vqs = vscsi->num_queues + VIRTIO_SCSI_VQ_BASE;
vqs = kmalloc(num_vqs * sizeof(struct virtqueue *), GFP_KERNEL);
callbacks = kmalloc(num_vqs * sizeof(vq_callback_t *), GFP_KERNEL);
--
1.9.3
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