On Wed, 10 Apr 2019, Raul E Rangel wrote:
> This change will send a CHANGE event to udev with the DEAD environment
> variable set when the HC dies. I chose this instead of any of the other
> udev events because it's representing a state change in the host
> controller. The only other event that might have fit was OFFLINE, but
> that seems to be used for hot-removal.
>
> By notifying user space the appropriate policies can be applied.
> e.g.,
> * Collect error logs.
> * Notify the user that USB is no longer functional.
> * Perform a graceful reboot.
>
> Signed-off-by: Raul E Rangel <rrangel@xxxxxxxxxxxx>
One or two problems... See below.
> ---
>
> drivers/usb/core/hcd.c | 25 +++++++++++++++++++++++++
> include/linux/usb/hcd.h | 1 +
> 2 files changed, 26 insertions(+)
>
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 975d7c1288e3..b38ad9ce068b 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -2343,6 +2343,22 @@ int hcd_bus_resume(struct usb_device *rhdev, pm_message_t msg)
> return status;
> }
>
> +
> +/**
> + * hcd_died_work - Workqueue routine for root-hub has died.
> + * @hcd: primary host controller for this root hub.
> + *
> + * Do not call with the shared_hcd.
> + * */
> +static void hcd_died_work(struct work_struct *work)
> +{
> + struct usb_hcd *hcd = container_of(work, struct usb_hcd, died_work);
> +
> + /* Notify user space that the host controller has died */
> + kobject_uevent_env(&hcd->self.root_hub->dev.kobj, KOBJ_CHANGE,
> + (char *[]){ "DEAD=1", NULL });
How do you know that the root hub hasn't already been deallocated?
> +}
> +
> /* Workqueue routine for root-hub remote wakeup */
> static void hcd_resume_work(struct work_struct *work)
> {
> @@ -2488,6 +2504,13 @@ void usb_hc_died (struct usb_hcd *hcd)
> usb_kick_hub_wq(hcd->self.root_hub);
> }
> }
> +
> + /* Handle the case where this function gets called with a shared HCD */
> + if (usb_hcd_is_primary_hcd(hcd))
> + schedule_work(&hcd->died_work);
> + else
> + schedule_work(&hcd->primary_hcd->died_work);
> +
> spin_unlock_irqrestore (&hcd_root_hub_lock, flags);
> /* Make sure that the other roothub is also deallocated. */
> }
> @@ -2555,6 +2578,8 @@ struct usb_hcd *__usb_create_hcd(const struct hc_driver *driver,
> INIT_WORK(&hcd->wakeup_work, hcd_resume_work);
> #endif
>
> + INIT_WORK(&hcd->died_work, hcd_died_work);
> +
> hcd->driver = driver;
> hcd->speed = driver->flags & HCD_MASK;
> hcd->product_desc = (driver->product_desc) ? driver->product_desc :
You forgot to ensure that this work entry won't still be pending when
the hcd structure is deallocated.
Alan Stern
> diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
> index 695931b03684..ae51d5bd1dfc 100644
> --- a/include/linux/usb/hcd.h
> +++ b/include/linux/usb/hcd.h
> @@ -98,6 +98,7 @@ struct usb_hcd {
> #ifdef CONFIG_PM
> struct work_struct wakeup_work; /* for remote wakeup */
> #endif
> + struct work_struct died_work; /* for dying */
>
> /*
> * hardware info/state
>
