linux-kernel - [PATCH 3.16 012/134] usb: hub: Fix error loop seen after hub communication errors

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Message-ID: <lsq.1503062000.935134009@decadent.org.uk>
Date:   Fri, 18 Aug 2017 14:13:20 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Alan Stern" <stern@...land.harvard.edu>,
        "Guenter Roeck" <linux@...ck-us.net>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.16 012/134] usb: hub: Fix error loop seen after hub
 communication errors

3.16.47-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Guenter Roeck <linux@...ck-us.net>

commit 245b2eecee2aac6fdc77dcafaa73c33f9644c3c7 upstream.

While stress testing a usb controller using a bind/unbind looop, the
following error loop was observed.

usb 7-1.2: new low-speed USB device number 3 using xhci-hcd
usb 7-1.2: hub failed to enable device, error -108
usb 7-1-port2: cannot disable (err = -22)
usb 7-1-port2: couldn't allocate usb_device
usb 7-1-port2: cannot disable (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: activate --> -22
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: activate --> -22
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: activate --> -22
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: activate --> -22
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: activate --> -22
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: activate --> -22
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: activate --> -22
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: activate --> -22
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
hub 7-1:1.0: hub_ext_port_status failed (err = -22)
** 57 printk messages dropped ** hub 7-1:1.0: activate --> -22
** 82 printk messages dropped ** hub 7-1:1.0: hub_ext_port_status failed (err = -22)

This continues forever. After adding tracebacks into the code,
the call sequence leading to this is found to be as follows.

[<ffffffc0007fc8e0>] hub_activate+0x368/0x7b8
[<ffffffc0007fceb4>] hub_resume+0x2c/0x3c
[<ffffffc00080b3b8>] usb_resume_interface.isra.6+0x128/0x158
[<ffffffc00080b5d0>] usb_suspend_both+0x1e8/0x288
[<ffffffc00080c9c4>] usb_runtime_suspend+0x3c/0x98
[<ffffffc0007820a0>] __rpm_callback+0x48/0x7c
[<ffffffc00078217c>] rpm_callback+0xa8/0xd4
[<ffffffc000786234>] rpm_suspend+0x84/0x758
[<ffffffc000786ca4>] rpm_idle+0x2c8/0x498
[<ffffffc000786ed4>] __pm_runtime_idle+0x60/0xac
[<ffffffc00080eba8>] usb_autopm_put_interface+0x6c/0x7c
[<ffffffc000803798>] hub_event+0x10ac/0x12ac
[<ffffffc000249bb8>] process_one_work+0x390/0x6b8
[<ffffffc00024abcc>] worker_thread+0x480/0x610
[<ffffffc000251a80>] kthread+0x164/0x178
[<ffffffc0002045d0>] ret_from_fork+0x10/0x40

kick_hub_wq() is called from hub_activate() even after failures to
communicate with the hub. This results in an endless sequence of
hub event -> hub activate -> wq trigger -> hub event -> ...

Provide two solutions for the problem.

- Only trigger the hub event queue if communication with the hub
  is successful.
- After a suspend failure, only resume already suspended interfaces
  if the communication with the device is still possible.

Each of the changes fixes the observed problem. Use both to improve
robustness.

Acked-by: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/core/driver.c | 18 ++++++++++++++++++
 drivers/usb/core/hub.c    |  5 ++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1331,6 +1331,24 @@ static int usb_suspend_both(struct usb_d
 		 */
 		if (udev->parent && !PMSG_IS_AUTO(msg))
 			status = 0;
+
+		/*
+		 * If the device is inaccessible, don't try to resume
+		 * suspended interfaces and just return the error.
+		 */
+		if (status && status != -EBUSY) {
+			int err;
+			u16 devstat;
+
+			err = usb_get_status(udev, USB_RECIP_DEVICE, 0,
+					     &devstat);
+			if (err) {
+				dev_err(&udev->dev,
+					"Failed to suspend device, error %d\n",
+					status);
+				goto done;
+			}
+		}
 	}
 
 	/* If the suspend failed, resume interfaces that did get suspended */
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1044,6 +1044,9 @@ static void hub_activate(struct usb_hub
 
 		portstatus = portchange = 0;
 		status = hub_port_status(hub, port1, &portstatus, &portchange);
+		if (status)
+			goto abort;
+
 		if (udev || (portstatus & USB_PORT_STAT_CONNECTION))
 			dev_dbg(&port_dev->dev, "status %04x change %04x\n",
 					portstatus, portchange);
@@ -1176,7 +1179,7 @@ static void hub_activate(struct usb_hub
 
 	/* Scan all ports that need attention */
 	kick_khubd(hub);
-
+ abort:
 	/* Allow autosuspend if it was suppressed */
 	if (type <= HUB_INIT3)
 		usb_autopm_put_interface_async(to_usb_interface(hub->intfdev));