| Message ID | 20200122074302.69790-1-ejh@nvidia.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] usb: uas: fix a plug & unplug racing | expand |
Am Dienstag, den 21.01.2020, 23:43 -0800 schrieb EJ Hsu: > When a uas disk is plugged into an external hub, uas_probe() > will be called by the hub thread to do the probe. It will > first create a SCSI host and then do the scan for this host. > During the scan, it will probe the LUN using SCSI INQUERY command > which will be packed in the URB and submitted to uas disk. > > There might be a chance that this external hub with uas disk > attached is unplugged during the scan. In this case, uas driver > will fail to submit the URB (due to the NOTATTACHED state of uas > device) and try to put this SCSI command back to request queue > waiting for next chance to run. > > In normal case, this cycle will terminate when hub thread gets > disconnection event and calls into uas_disconnect() accordingly. > But in this case, uas_disconnect() will not be called because > hub thread of external hub gets stuck waiting for the completion > of this SCSI command. A deadlock happened. > > In this fix, uas will call scsi_scan_host() asynchronously to > avoid the blocking of hub thread. > > Signed-off-by: EJ Hsu <ejh@nvidia.com> Acked-by: Oliver Neukum <oneukum@suse.com>
On Thu, Jan 23, 2020 at 08:02:02AM +0100, Oliver Neukum wrote: > Am Dienstag, den 21.01.2020, 23:43 -0800 schrieb EJ Hsu: > > When a uas disk is plugged into an external hub, uas_probe() > > will be called by the hub thread to do the probe. It will > > first create a SCSI host and then do the scan for this host. > > During the scan, it will probe the LUN using SCSI INQUERY command > > which will be packed in the URB and submitted to uas disk. > > > > There might be a chance that this external hub with uas disk > > attached is unplugged during the scan. In this case, uas driver > > will fail to submit the URB (due to the NOTATTACHED state of uas > > device) and try to put this SCSI command back to request queue > > waiting for next chance to run. > > > > In normal case, this cycle will terminate when hub thread gets > > disconnection event and calls into uas_disconnect() accordingly. > > But in this case, uas_disconnect() will not be called because > > hub thread of external hub gets stuck waiting for the completion > > of this SCSI command. A deadlock happened. > > > > In this fix, uas will call scsi_scan_host() asynchronously to > > avoid the blocking of hub thread. > > > > Signed-off-by: EJ Hsu <ejh@nvidia.com> > Acked-by: Oliver Neukum <oneukum@suse.com> EJ can you resend this with Oliver's ack as I lost the original patch in my archives now as it was so long ago... thanks, greg k-h
diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c index 95bba3ba6ac6..3670fda02c34 100644 --- a/drivers/usb/storage/uas.c +++ b/drivers/usb/storage/uas.c @@ -45,6 +45,7 @@ struct uas_dev_info { struct scsi_cmnd *cmnd[MAX_CMNDS]; spinlock_t lock; struct work_struct work; + struct work_struct scan_work; /* for async scanning */ }; enum { @@ -114,6 +115,17 @@ static void uas_do_work(struct work_struct *work) spin_unlock_irqrestore(&devinfo->lock, flags); } +static void uas_scan_work(struct work_struct *work) +{ + struct uas_dev_info *devinfo = + container_of(work, struct uas_dev_info, scan_work); + struct Scsi_Host *shost = usb_get_intfdata(devinfo->intf); + + dev_dbg(&devinfo->intf->dev, "starting scan\n"); + scsi_scan_host(shost); + dev_dbg(&devinfo->intf->dev, "scan complete\n"); +} + static void uas_add_work(struct uas_cmd_info *cmdinfo) { struct scsi_pointer *scp = (void *)cmdinfo; @@ -982,6 +994,7 @@ static int uas_probe(struct usb_interface *intf, const struct usb_device_id *id) init_usb_anchor(&devinfo->data_urbs); spin_lock_init(&devinfo->lock); INIT_WORK(&devinfo->work, uas_do_work); + INIT_WORK(&devinfo->scan_work, uas_scan_work); result = uas_configure_endpoints(devinfo); if (result) @@ -998,7 +1011,9 @@ static int uas_probe(struct usb_interface *intf, const struct usb_device_id *id) if (result) goto free_streams; - scsi_scan_host(shost); + /* Submit the delayed_work for SCSI-device scanning */ + schedule_work(&devinfo->scan_work); + return result; free_streams: @@ -1166,6 +1181,12 @@ static void uas_disconnect(struct usb_interface *intf) usb_kill_anchored_urbs(&devinfo->data_urbs); uas_zap_pending(devinfo, DID_NO_CONNECT); + /* + * Prevent SCSI scanning (if it hasn't started yet) + * or wait for the SCSI-scanning routine to stop. + */ + cancel_work_sync(&devinfo->scan_work); + scsi_remove_host(shost); uas_free_streams(devinfo); scsi_host_put(shost);
When a uas disk is plugged into an external hub, uas_probe() will be called by the hub thread to do the probe. It will first create a SCSI host and then do the scan for this host. During the scan, it will probe the LUN using SCSI INQUERY command which will be packed in the URB and submitted to uas disk. There might be a chance that this external hub with uas disk attached is unplugged during the scan. In this case, uas driver will fail to submit the URB (due to the NOTATTACHED state of uas device) and try to put this SCSI command back to request queue waiting for next chance to run. In normal case, this cycle will terminate when hub thread gets disconnection event and calls into uas_disconnect() accordingly. But in this case, uas_disconnect() will not be called because hub thread of external hub gets stuck waiting for the completion of this SCSI command. A deadlock happened. In this fix, uas will call scsi_scan_host() asynchronously to avoid the blocking of hub thread. Signed-off-by: EJ Hsu <ejh@nvidia.com> --- drivers/usb/storage/uas.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-)