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usb: core: hub: hub_port_init lock controller instead of bus 

The XHCI controller presents two USB buses to the system - one for USB2
and one for USB3. The hub init code (hub_port_init) is reentrant but
only locks one bus per thread, leading to a race condition failure when
two threads attempt to simultaneously initialise a USB2 and USB3 device:

[    8.034843] xhci_hcd 0000:00:14.0: Timeout while waiting for setup device command
[   13.183701] usb 3-3: device descriptor read/all, error -110

On a test system this failure occurred on 6% of all boots.

The call traces at the point of failure are:

Call Trace:
 [<ffffffff81b9bab7>] schedule+0x37/0x90
 [<ffffffff817da7cd>] usb_kill_urb+0x8d/0xd0
 [<ffffffff8111e5e0>] ? wake_up_atomic_t+0x30/0x30
 [<ffffffff817dafbe>] usb_start_wait_urb+0xbe/0x150
 [<ffffffff817db10c>] usb_control_msg+0xbc/0xf0
 [<ffffffff817d07de>] hub_port_init+0x51e/0xb70
 [<ffffffff817d4697>] hub_event+0x817/0x1570
 [<ffffffff810f3e6f>] process_one_work+0x1ff/0x620
 [<ffffffff810f3dcf>] ? process_one_work+0x15f/0x620
 [<ffffffff810f4684>] worker_thread+0x64/0x4b0
 [<ffffffff810f4620>] ? rescuer_thread+0x390/0x390
 [<ffffffff810fa7f5>] kthread+0x105/0x120
 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200
 [<ffffffff81ba183f>] ret_from_fork+0x3f/0x70
 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200

Call Trace:
 [<ffffffff817fd36d>] xhci_setup_device+0x53d/0xa40
 [<ffffffff817fd87e>] xhci_address_device+0xe/0x10
 [<ffffffff817d047f>] hub_port_init+0x1bf/0xb70
 [<ffffffff811247ed>] ? trace_hardirqs_on+0xd/0x10
 [<ffffffff817d4697>] hub_event+0x817/0x1570
 [<ffffffff810f3e6f>] process_one_work+0x1ff/0x620
 [<ffffffff810f3dcf>] ? process_one_work+0x15f/0x620
 [<ffffffff810f4684>] worker_thread+0x64/0x4b0
 [<ffffffff810f4620>] ? rescuer_thread+0x390/0x390
 [<ffffffff810fa7f5>] kthread+0x105/0x120
 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200
 [<ffffffff81ba183f>] ret_from_fork+0x3f/0x70
 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200

Which results from the two call chains:

hub_port_init
 usb_get_device_descriptor
  usb_get_descriptor
   usb_control_msg
    usb_internal_control_msg
     usb_start_wait_urb
      usb_submit_urb / wait_for_completion_timeout / usb_kill_urb

hub_port_init
 hub_set_address
  xhci_address_device
   xhci_setup_device

Mathias Nyman explains the current behaviour violates the XHCI spec:

 hub_port_reset() will end up moving the corresponding xhci device slot
 to default state.

 As hub_port_reset() is called several times in hub_port_init() it
 sounds reasonable that we could end up with two threads having their
 xhci device slots in default state at the same time, which according to
 xhci 4.5.3 specs still is a big no no:

 "Note: Software shall not transition more than one Device Slot to the
  Default State at a time"

 So both threads fail at their next task after this.
 One fails to read the descriptor, and the other fails addressing the
 device.

Fix this in hub_port_init by locking the USB controller (instead of an
individual bus) to prevent simultaneous initialisation of both buses.

Fixes: 638139eb95 ("usb: hub: allow to process more usb hub events in parallel")
Link: https://lkml.org/lkml/2016/2/8/312
Link: https://lkml.org/lkml/2016/2/4/748
Signed-off-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Chris Bainbridge 2016-04-25 13:48:38 +01:00 committed by Greg Kroah-Hartman
parent edc8c54bf4
commit feb26ac31a
4 changed files with 19 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/usb/core/hcd.c
View File

@ -994,7 +994,7 @@ static void usb_bus_init (struct usb_bus *bus)
bus->bandwidth_allocated = 0;
bus->bandwidth_int_reqs = 0;
bus->bandwidth_isoc_reqs = 0;
mutex_init(&bus->usb_address0_mutex);
mutex_init(&bus->devnum_next_mutex);
}
/*-------------------------------------------------------------------------*/
@ -2521,6 +2521,14 @@ struct usb_hcd *usb_create_shared_hcd(const struct hc_driver *driver,
return NULL;
}
if (primary_hcd == NULL) {
hcd->address0_mutex = kmalloc(sizeof(*hcd->address0_mutex),
GFP_KERNEL);
if (!hcd->address0_mutex) {
kfree(hcd);
dev_dbg(dev, "hcd address0 mutex alloc failed\n");
return NULL;
}
mutex_init(hcd->address0_mutex);
hcd->bandwidth_mutex = kmalloc(sizeof(*hcd->bandwidth_mutex),
GFP_KERNEL);
if (!hcd->bandwidth_mutex) {
@ -2532,6 +2540,7 @@ struct usb_hcd *usb_create_shared_hcd(const struct hc_driver *driver,
dev_set_drvdata(dev, hcd);
} else {
mutex_lock(&usb_port_peer_mutex);
hcd->address0_mutex = primary_hcd->address0_mutex;
hcd->bandwidth_mutex = primary_hcd->bandwidth_mutex;
hcd->primary_hcd = primary_hcd;
primary_hcd->primary_hcd = primary_hcd;
@ -2598,8 +2607,10 @@ static void hcd_release(struct kref *kref)
struct usb_hcd *hcd = container_of (kref, struct usb_hcd, kref);
mutex_lock(&usb_port_peer_mutex);
if (usb_hcd_is_primary_hcd(hcd))
if (usb_hcd_is_primary_hcd(hcd)) {
kfree(hcd->address0_mutex);
kfree(hcd->bandwidth_mutex);
}
if (hcd->shared_hcd) {
struct usb_hcd *peer = hcd->shared_hcd;

8
drivers/usb/core/hub.c
View File

@ -2082,7 +2082,7 @@ static void choose_devnum(struct usb_device *udev)
struct usb_bus *bus = udev->bus;
/* be safe when more hub events are proceed in parallel */
mutex_lock(&bus->usb_address0_mutex);
mutex_lock(&bus->devnum_next_mutex);
if (udev->wusb) {
devnum = udev->portnum + 1;
BUG_ON(test_bit(devnum, bus->devmap.devicemap));
@ -2100,7 +2100,7 @@ static void choose_devnum(struct usb_device *udev)
set_bit(devnum, bus->devmap.devicemap);
udev->devnum = devnum;
}
mutex_unlock(&bus->usb_address0_mutex);
mutex_unlock(&bus->devnum_next_mutex);
}
static void release_devnum(struct usb_device *udev)
@ -4366,7 +4366,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
if (oldspeed == USB_SPEED_LOW)
delay = HUB_LONG_RESET_TIME;
mutex_lock(&hdev->bus->usb_address0_mutex);
mutex_lock(hcd->address0_mutex);
/* Reset the device; full speed may morph to high speed */
/* FIXME a USB 2.0 device may morph into SuperSpeed on reset. */
@ -4652,7 +4652,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
hub_port_disable(hub, port1, 0);
update_devnum(udev, devnum); /* for disconnect processing */
}
mutex_unlock(&hdev->bus->usb_address0_mutex);
mutex_unlock(hcd->address0_mutex);
return retval;
}

3
include/linux/usb.h
View File

@ -374,13 +374,12 @@ struct usb_bus {
int devnum_next; /* Next open device number in
* round-robin allocation */
struct mutex devnum_next_mutex; /* devnum_next mutex */
struct usb_devmap devmap; /* device address allocation map */
struct usb_device *root_hub; /* Root hub */
struct usb_bus *hs_companion; /* Companion EHCI bus, if any */
struct mutex usb_address0_mutex; /* unaddressed device mutex */
int bandwidth_allocated; /* on this bus: how much of the time
* reserved for periodic (intr/iso)
* requests is used, on average?

1
include/linux/usb/hcd.h
View File

@ -181,6 +181,7 @@ struct usb_hcd {
* bandwidth_mutex should be dropped after a successful control message
* to the device, or resetting the bandwidth after a failed attempt.
*/
struct mutex *address0_mutex;
struct mutex *bandwidth_mutex;
struct usb_hcd *shared_hcd;
struct usb_hcd *primary_hcd;