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a00918d052
Regression in commit 638139eb95d2 ("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.
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 6fecd4f2a58c ("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.
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.
Fixes: 638139eb95d2 ("usb: hub: allow to process more usb hub events in parallel")
Link: https://lkml.kernel.org/g/CAP-bSRb=A0iEYobdGCLpwynS7pkxpt_9ZnwyZTPVAoy0Y=Zo3Q@mail.gmail.com
Signed-off-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Cc: <stable@vger.kernel.org> # 3.18+
[changed git commit description style for checkpatch -Mathias]
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.