Re: [RFT PATCH 1/1] xhci: free xhci virtual devices with leaf nodes first

[Guenter Roeck <linux@roeck-us.net>]

On Wed, Nov 23, 2016 at 02:24:27PM +0200, Mathias Nyman wrote:
> the tt_info provided by a HS hub might be in use to by a child device
> Make sure we free the devices in the correct order.
> 
> This is needed in special cases such as when xhci controller is
> reset when resuming from hibernate, and all virt_devices are freed.
> 
> Also free the virt_devices starting from max slot_id as children
> more commonly have higher slot_id than parent.
> 
> CC: <stable@vger.kernel.org>
> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
> 
> ---
> 
> Guenter Roeck, does this work for you?
> 
Yes, it does.

Tested-by: Guenter Roeck <groeck@chromium.org>

Thanks,
Guenter

> A rework of how tt_info is stored and used might be needed,
> but that will take some time and won't go to stable as easily.
> ---
>  drivers/usb/host/xhci-mem.c | 38 ++++++++++++++++++++++++++++++++++++--
>  1 file changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> index 6afe323..b3a5cd8 100644
> --- a/drivers/usb/host/xhci-mem.c
> +++ b/drivers/usb/host/xhci-mem.c
> @@ -979,6 +979,40 @@ void xhci_free_virt_device(struct xhci_hcd *xhci, int slot_id)
>  	xhci->devs[slot_id] = NULL;
>  }
>  
> +/*
> + * Free a virt_device structure.
> + * If the virt_device added a tt_info (a hub) and has children pointing to
> + * that tt_info, then free the child first. Recursive.
> + * We can't rely on udev at this point to find child-parent relationships.
> + */
> +void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id)
> +{
> +	struct xhci_virt_device *vdev;
> +	struct list_head *tt_list_head;
> +	struct xhci_tt_bw_info *tt_info, *next;
> +	int i;
> +
> +	vdev = xhci->devs[slot_id];
> +	if (!vdev)
> +		return;
> +
> +	tt_list_head = &(xhci->rh_bw[vdev->real_port - 1].tts);
> +	list_for_each_entry_safe(tt_info, next, tt_list_head, tt_list) {
> +		/* is this a hub device that added a tt_info to the tts list */
> +		if (tt_info->slot_id == slot_id) {
> +			/* are any devices using this tt_info? */
> +			for (i = 1; i < HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
> +				vdev = xhci->devs[i];
> +				if (vdev && (vdev->tt_info == tt_info))
> +					xhci_free_virt_devices_depth_first(
> +						xhci, i);
> +			}
> +		}
> +	}
> +	/* we are now at a leaf device */
> +	xhci_free_virt_device(xhci, slot_id);
> +}
> +
>  int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
>  		struct usb_device *udev, gfp_t flags)
>  {
> @@ -1829,8 +1863,8 @@ void xhci_mem_cleanup(struct xhci_hcd *xhci)
>  		}
>  	}
>  
> -	for (i = 1; i < MAX_HC_SLOTS; ++i)
> -		xhci_free_virt_device(xhci, i);
> +	for (i = HCS_MAX_SLOTS(xhci->hcs_params1); i > 0; i--)
> +		xhci_free_virt_devices_depth_first(xhci, i);
>  
>  	dma_pool_destroy(xhci->segment_pool);
>  	xhci->segment_pool = NULL;
> -- 
> 1.9.1
>