Patch "usb: uas: unconditionally bring back host after reset" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

usb: uas: unconditionally bring back host after reset

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-uas-unconditionally-bring-back-host-after-reset.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Oliver Neukum <[email protected]>
Date: Thu, 11 Jan 2018 13:10:16 +0100
Subject: usb: uas: unconditionally bring back host after reset

From: Oliver Neukum <[email protected]>

commit cbeef22fd611c4f47c494b821b2b105b8af970bb upstream.

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.

---
 drivers/usb/storage/uas.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

@@ -1076,20 +1076,19 @@ static int uas_post_reset(struct usb_int
 		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)

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/usb-uas-unconditionally-bring-back-host-after-reset.patch queue-4.9/cdc-acm-apply-quirk-for-card-reader.patch queue-4.9/usb-cdc-acm-do-not-log-urb-submission-errors-on-disconnect.patch