Quoting Hans:

If we return 1 from our post_reset handler, then our disconnect handler will be called immediately afterwards. Since pre_reset blocks all scsi requests our disconnect handler will then hang in the scsi_remove_host call.

This is esp. bad because our disconnect handler hanging for ever also stops the USB subsys from enumerating any new USB devices, causes commands like lsusb to hang, etc.

In practice this happens when unplugging some uas devices because the hub code may see the device as needing a warm-reset and calls usb_reset_device before seeing the disconnect. In this case uas_configure_endpoints fails with -ENODEV. We do not want to print an error for this, so this commit also silences the shost_printk for -ENODEV.

ENDQUOTE

However, if we do that we better drop any unconditional execution and report to the SCSI subsystem that we have undergone a reset but we are not operational now.

Signed-off-by: Oliver Neukum oneukum@suse.com Reported-by: Hans de Goede hdegoede@redhat.com CC: stable@vger.kernel.org --- drivers/usb/storage/uas.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c index 5d04c40ee40a..3b1b9695177a 100644 --- a/drivers/usb/storage/uas.c +++ b/drivers/usb/storage/uas.c @@ -1076,20 +1076,19 @@ static int uas_post_reset(struct usb_interface *intf) return 0;

err = uas_configure_endpoints(devinfo); - if (err) { + if (err && err != ENODEV) shost_printk(KERN_ERR, shost, "%s: alloc streams error %d after reset", __func__, err); - return 1; - }

+ /* we must unblock the host in every case lest we deadlock */ spin_lock_irqsave(shost->host_lock, flags); scsi_report_bus_reset(shost, 0); spin_unlock_irqrestore(shost->host_lock, flags);

scsi_unblock_requests(shost);

- return 0; + return err ? 1 : 0; }

static int uas_suspend(struct usb_interface *intf, pm_message_t message)