static int hpsa_scsi_queue_command(struct scsi_cmnd *cmd,
                void (*done)(struct scsi_cmnd *));
+static void hpsa_scan_start(struct Scsi_Host *);
+static int hpsa_scan_finished(struct Scsi_Host *sh,
+       unsigned long elapsed_time);
 
 static int hpsa_eh_device_reset_handler(struct scsi_cmnd *scsicmd);
 static int hpsa_slave_alloc(struct scsi_device *sdev);
        .name                   = "hpsa",
        .proc_name              = "hpsa",
        .queuecommand           = hpsa_scsi_queue_command,
+       .scan_start             = hpsa_scan_start,
+       .scan_finished          = hpsa_scan_finished,
        .this_id                = -1,
        .sg_tablesize           = MAXSGENTRIES,
        .use_clustering         = ENABLE_CLUSTERING,
                        h->busy_scanning = 1;
                        mutex_unlock(&hpsa_scan_mutex);
                        host_no = h->scsi_host ?  h->scsi_host->host_no : -1;
-                       hpsa_update_scsi_devices(h, host_no);
+                       hpsa_scan_start(h->scsi_host);
                        complete_all(&h->scan_wait);
                        mutex_lock(&hpsa_scan_mutex);
                        h->busy_scanning = 0;
        return 0;
 }
 
+static void hpsa_scan_start(struct Scsi_Host *sh)
+{
+       struct ctlr_info *h = shost_to_hba(sh);
+       unsigned long flags;
+
+       /* wait until any scan already in progress is finished. */
+       while (1) {
+               spin_lock_irqsave(&h->scan_lock, flags);
+               if (h->scan_finished)
+                       break;
+               spin_unlock_irqrestore(&h->scan_lock, flags);
+               wait_event(h->scan_wait_queue, h->scan_finished);
+               /* Note: We don't need to worry about a race between this
+                * thread and driver unload because the midlayer will
+                * have incremented the reference count, so unload won't
+                * happen if we're in here.
+                */
+       }
+       h->scan_finished = 0; /* mark scan as in progress */
+       spin_unlock_irqrestore(&h->scan_lock, flags);
+
+       hpsa_update_scsi_devices(h, h->scsi_host->host_no);
+
+       spin_lock_irqsave(&h->scan_lock, flags);
+       h->scan_finished = 1; /* mark scan as finished. */
+       wake_up_all(&h->scan_wait_queue);
+       spin_unlock_irqrestore(&h->scan_lock, flags);
+}
+
+static int hpsa_scan_finished(struct Scsi_Host *sh,
+       unsigned long elapsed_time)
+{
+       struct ctlr_info *h = shost_to_hba(sh);
+       unsigned long flags;
+       int finished;
+
+       spin_lock_irqsave(&h->scan_lock, flags);
+       finished = h->scan_finished;
+       spin_unlock_irqrestore(&h->scan_lock, flags);
+       return finished;
+}
+
 static void hpsa_unregister_scsi(struct ctlr_info *h)
 {
        /* we are being forcibly unloaded, and may not refuse. */
 {
        int rc;
 
-       hpsa_update_scsi_devices(h, -1);
        rc = hpsa_scsi_detect(h);
        if (rc != 0)
                dev_err(&h->pdev->dev, "hpsa_register_scsi: failed"
        case CCISS_DEREGDISK:
        case CCISS_REGNEWDISK:
        case CCISS_REGNEWD:
-               hpsa_update_scsi_devices(h, dev->host->host_no);
+               hpsa_scan_start(h->scsi_host);
                return 0;
        case CCISS_GETPCIINFO:
                return hpsa_getpciinfo_ioctl(h, argp);
                goto clean4;
        }
        spin_lock_init(&h->lock);
+       spin_lock_init(&h->scan_lock);
+       init_waitqueue_head(&h->scan_wait_queue);
+       h->scan_finished = 1; /* no scan currently in progress */
 
        pci_set_drvdata(pdev, h);
        memset(h->cmd_pool_bits, 0,