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

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 24.11.2016 11:02, Felipe Balbi wrote:
>
> Hi,
>
> Mathias Nyman <mathias.nyman@linux.intel.com> writes:
>> 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?
>>
>> 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) {
>
> 		if (tt_info->slot_id != slot_id)
>                  	continue;
>
>> +			/* are any devices using this tt_info? */
>> +			for (i = 1; i < HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
>
> off-by-one here ? Why is i starting from 1?
>
>> +				vdev = xhci->devs[i];

slit_id 0 is reserved and xhci->devs[0] is not used, so ne need to check it.

All other places that check xhci->devs[0] are avtually buggy

-Mathias