Re: [PATCH v3] usb: hub: Fix error loop seen after hub communication errors

[Doug Anderson]

Hi,

On Thu, Mar 16, 2017 at 12:24 PM, Guenter Roeck  wrote:
> @@ -1198,7 +1201,7 @@ static void hub_activate(struct usb_hub *hub, enum 
> hub_activation_type type)
>
> /* Scan all ports that need attention */
> kick_hub_wq(hub);
> -
> +abort:

One tiny nit that could be done when applying this patch is to add a
space before "abort".  Other goto labels in this function are preceded
by a space and it's sane to try to match the existing coding
convention in the function rather than trying to mix and match.

Other than that this patch seems sane to me, but I am by no means an
expert on this code.  ;)


-Doug
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Re: [PATCH v3] usb: hub: Fix error loop seen after hub communication errors

[Alan Stern]

On Thu, 16 Mar 2017, Guenter Roeck wrote:

> 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.
> 
> [] hub_activate+0x368/0x7b8
> [] hub_resume+0x2c/0x3c
> [] usb_resume_interface.isra.6+0x128/0x158
> [] usb_suspend_both+0x1e8/0x288
> [] usb_runtime_suspend+0x3c/0x98
> [] __rpm_callback+0x48/0x7c
> [] rpm_callback+0xa8/0xd4
> [] rpm_suspend+0x84/0x758
> [] rpm_idle+0x2c8/0x498
> [] __pm_runtime_idle+0x60/0xac
> [] usb_autopm_put_interface+0x6c/0x7c
> [] hub_event+0x10ac/0x12ac
> [] process_one_work+0x390/0x6b8
> [] worker_thread+0x480/0x610
> [] kthread+0x164/0x178
> [] 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
>   was 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.
> 
> Signed-off-by: Guenter Roeck 
> ---
> v3: In hub.c, abort immediately if hub_port_status() returns an error.
> Since hub_port_status() already logs the error, don't log it again.
> In device,c, log the error return value from usb_suspend_device()
> if usb_get_status() failed as well.
> Don't check if the hub is still accessible if the error returned
> from hub_port_status() is -EBUSY.
> v2: Instead of not triggering the hub wq after an error to submit an urb,
> implement a more complex error detection and handling. Do it in two
> places. Marked as RFC to determine if one (or both) of those solutions
> are viable.
> 
>  drivers/usb/core/driver.c | 18 ++
>  drivers/usb/core/hub.c|  5 -
>  2 files changed, 22 insertions(+), 1 deletion(-)

Acked-by: Alan Stern 




> diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> index cdee5130638b..7ebdf2a4e8fe 100644
> --- a/drivers/usb/core/driver.c
> +++ b/drivers/usb/core/driver.c
> @@ -1331,6 +1331,24 @@ static int usb_suspend_both(struct usb_device *udev, 
> pm_message_t msg)
>*/
>   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,
> +  );
> + if (err) {
> + dev_err(>dev,
> + "Failed to suspend device, error %d\n",
> + status);
> + goto done;
> + }
> + }
>   }
>  
>   /* If the