virtio_scsi: fix race on device removal

We cancel event work on device removal, but an interrupt
could trigger immediately after this, and queue it
again.

To fix, set a flag.

Loosely based on patch by Paolo Bonzini

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index 29fd44a..0227d39 100644 (file)
--- 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;
 
+       /* Protected by event_vq lock */
+       bool stop_events;
+
        struct virtio_scsi_vq ctrl_vq;
        struct virtio_scsi_vq event_vq;
        struct virtio_scsi_vq req_vqs[];
@@ -303,6 +306,11 @@ static void virtscsi_cancel_event_work(struct virtio_scsi *vscsi)
 {
        int i;
 
+       /* Stop scheduling work before calling cancel_work_sync.  */
+       spin_lock_irq(&vscsi->event_vq.vq_lock);
+       vscsi->stop_events = true;
+       spin_unlock_irq(&vscsi->event_vq.vq_lock);
+
        for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++)
                cancel_work_sync(&vscsi->event_list[i].work);
 }
@@ -390,7 +398,8 @@ static void virtscsi_complete_event(struct virtio_scsi *vscsi, void *buf)
 {
        struct virtio_scsi_event_node *event_node = buf;
 
-       queue_work(system_freezable_wq, &event_node->work);
+       if (!vscsi->stop_events)
+               queue_work(system_freezable_wq, &event_node->work);
 }
 
 static void virtscsi_event_done(struct virtqueue *vq)