Hi, On 12/01/2016 03:35 PM, Baolin Wang wrote: > On 1 December 2016 at 14:35, Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote: >> Hi, >> >> On 12/01/2016 02:04 PM, Baolin Wang wrote: >>> Hi Baolu, >>> >>> On 1 December 2016 at 13:45, Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote: >>>> Hi, >>>> >>>> On 11/30/2016 05:02 PM, Baolin Wang wrote: >>>>> If the hardware never responds to the stop endpoint command, the >>>>> URBs will never be completed, and we might hang the USB subsystem. >>>>> The original watchdog timer is used to watch if one stop endpoint >>>>> command is timeout, if timeout, then the watchdog timer will set >>>>> XHCI_STATE_DYING, try to halt the xHCI host, and give back all >>>>> pending URBs. >>>>> >>>>> But now we already have one command timer to control command timeout, >>>>> thus we can also use the command timer to watch the stop endpoint >>>>> command, instead of one duplicate watchdog timer which need to be >>>>> removed. >>>>> >>>>> Meanwhile we don't need the 'stop_cmds_pending' flag to identy if >>>>> this is the last stop endpoint command of one endpoint. Since we >>>>> can make sure we only set one stop endpoint command for one endpoint >>>>> by 'EP_HALT_PENDING' flag in xhci_urb_dequeue() function. Thus remove >>>>> this flag. >>>> I am afraid you can't do this. "stop_cmds_pending" was added >>>> to fix the problem described in the comments that you want to >>>> remove. But I didn't find any fix of this problem in your patch. >>> Now we can not pending another stop endpoint command for the same one >>> endpoint, since will check 'EP_HALT_PENDING' flag in >>> xhci_urb_dequeue() function to avoid this. But after some >>> investigation, I think I missed the stop endpoint command in >>> xhci_stop_device() which did not check the 'EP_HALT_PENDING' flag, >>> maybe need to add 'EP_HALT_PENDING' flag checking in >>> xhci_stop_device() function. DId I miss something else? Thanks. >> Consider below three threads running on different CPUs at the same time. >> >> Thread A: xhci_handle_cmd_stop_ep() --- in interrupt handler >> Thread B: xhci_stop_endpoint_command_timeout() --- timer expired >> Thread C: xhci_urb_dequeue --- called by usb core >> >> They are serialized by xhci->lock. Let's consider below sequence: >> >> Thread A: >> - delete xhci->cmd_timer), but will fail due to Thread B. >> - clear EP_HALT_PENDING bit >> >> Thread B: >> - halt the host controller >> >> Thread C: >> - set EP_HALT_PENDING bit >> - enqueue another stop endpoint command >> - add the timer back > Ah, thanks for you comments. > If thread B halted the host, then the thread C xhci_urb_dequeue() will > check host state failed, then just return and can not set another stop > endpoint command. Not so simple. Thread B will release xhci->lock before xhci_halt(). > But from your example, I think your meaning is we > should not halt the host by thread B, since we have handled the stop > endpoint command event. > > So I think we need to check the xhci command of this stop endpoint > command in xhci_stop_endpoint_command_timeout(), if the xhci command > of this stop endpoint command is not in the command list (which means > the stop endpoint command event has been handled), then just return > and do not halt the controller. Right? > I'd like suggest you to put this change into a separated patch. It's actually a different topic from the main purpose of this patch. Best regards, Lu Baolu -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
