On Wed, Apr 29, 2015 at 09:18:50AM +0100, Chris Bainbridge wrote: > Regression in commit 638139eb95d2d241781330a321e88c8dafe46078 > Author: Petr Mladek <pmladek@xxxxxxx> > Date: Fri Sep 19 17:32:24 2014 +0200 > > usb: hub: allow to process more usb hub events in parallel > > The regression resulted in intermittent failure to initialise a 10-port > hub (with three internal VL812 4-port hub controllers) on boot, with a > failure rate of around 8%, due to multiple race conditions when > accessing addr_dev and slot_id in struct xhci_hcd. That would explain why I haven't seen this before 3.18... > This regression also exposed a problem with xhci_setup_device, which > "should be protected by the usb_address0_mutex" but no longer is due to > commit 6fecd4f: > Author: Todd E Brandt <todd.e.brandt@xxxxxxxxxxxxxxx> > Date: Mon May 19 10:55:32 2014 -0700 > > USB: separate usb_address0 mutexes for each bus > > With separate buses (and locks) it is no longer the case that a single > lock will protect xhci_setup_device from accesses by two parallel > threads processing events on the two buses. ...even though this one went into 3.16 (and I must just have been lucky not to hit it with 3.18). > Fix this by adding a mutex to protect addr_dev and slot_id in struct > xhci_hcd, and by making the assignment of slot_id atomic. > > Fixes multiple boot errors: > > [ 0.583008] xhci_hcd 0000:00:14.0: Bad Slot ID 2 > [ 0.583009] xhci_hcd 0000:00:14.0: Could not allocate xHCI USB device data structures > [ 0.583012] usb usb1-port3: couldn't allocate usb_device > > And: > > [ 0.637409] xhci_hcd 0000:00:14.0: Error while assigning device slot ID > [ 0.637417] xhci_hcd 0000:00:14.0: Max number of devices this xHCI host supports is 32. > [ 0.637421] usb usb1-port1: couldn't allocate usb_device > > And: > > [ 0.753372] xhci_hcd 0000:00:14.0: ERROR: unexpected setup context command completion code 0x0. > [ 0.753373] usb 1-3: hub failed to enable device, error -22 > [ 0.753400] xhci_hcd 0000:00:14.0: Error while assigning device slot ID > [ 0.753402] xhci_hcd 0000:00:14.0: Max number of devices this xHCI host supports is 32. > [ 0.753403] usb usb1-port3: couldn't allocate usb_device > > And: > > [ 11.018386] usb 1-3: device descriptor read/all, error -110 > > And: > > [ 5.753838] xhci_hcd 0000:00:14.0: Timeout while waiting for setup device command > > Tested with 200 reboots, resulting in no USB hub init related errors. Great, thanks for looking into this! Mathias will review your suggested fix. Thanks, Johan -- 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
