linux/drivers/usb
Andiry Xu c2d7b49f42 USB: xHCI: prevent infinite loop when processing MSE event
When a xHC host is unable to handle isochronous transfer in the
interval, it reports a Missed Service Error event and skips some tds.

Currently xhci driver handles MSE event in the following ways:

1. When encounter a MSE event, set ep->skip flag, update event ring
   dequeue pointer and return.

2. When encounter the next event on this ep, the driver will run the
   do-while loop, fetch td from ep's td_list to find the td
   corresponding to this event.  All tds missed are marked as short
   transfer(-EXDEV).

The do-while loop will end in two ways:

1. If the td pointed by the event trb is found;

2. If the ep ring's td_list is empty.

However, if a buggy HW reports some unpredicted event (for example, an
overrun event following a MSE event while the ep ring is actually not
empty), the driver will never find the td, and it will loop until the
td_list is empty.

Unfortunately, the spinlock is dropped when give back a urb in the
do-while loop.  During the spinlock released period, the class driver
may still submit urbs and add tds to the td_list.  This may cause
disaster, since the td_list will never be empty and the loop never ends,
and the system hangs.

To fix this, count the number of TDs on the ep ring before skipping TDs,
and quit the loop when skipped that number of tds.  This guarantees the
do-while loop will end after certain number of cycles, and driver will
not be trapped in an infinite loop.

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-09-19 17:15:47 -07:00
..
atm drivers: usb: atm: ueagle-atm: Add missing const qualifier 2011-07-08 14:51:30 -07:00
c67x00
class USB: assign instead of equal in usbtmc.c 2011-08-08 12:34:45 -07:00
core USB: Avoid NULL pointer deref in usb_hcd_alloc_bandwidth. 2011-08-15 09:22:40 -07:00
early
gadget Merge branch 'fixes' into for-greg 2011-08-15 19:02:25 +03:00
host USB: xHCI: prevent infinite loop when processing MSE event 2011-09-19 17:15:47 -07:00
image atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
misc atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
mon USB: mon: Allow to use usbmon without debugfs 2011-07-08 14:55:09 -07:00
musb usb: musb: gadget: fix error path 2011-08-12 12:06:34 +03:00
otg Merge branch 'usb-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb-2.6 2011-07-25 23:08:32 -07:00
renesas_usbhs usb: gadget: renesas_usbhs: fix DMA build by including dma-mapping.h 2011-08-12 11:52:48 +03:00
serial USB: ftdi_sio: add Calao reference board support 2011-08-25 09:44:50 -07:00
storage USB: usb-storage: unusual_devs entry for ARM V2M motherboard. 2011-08-08 12:34:46 -07:00
wusbcore atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
Kconfig usb: renesas_usbhs: compile/config are rescued 2011-07-08 14:57:12 -07:00
Makefile
README
usb-skeleton.c

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 ("khubd").

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.