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usbcore: make hcd_endpoint_disable wait for queue to drain

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The inconsistent lock state problem in usbcore (the one that shows up
when an HCD is unloaded) comes down to two inter-related problems:

	usb_rh_urb_dequeue() isn't set up to be called with interrupts
	disabled.

	hcd_endpoint_disable() doesn't wait for all URBs on the
	endpoint's queue to complete.

The two problems are related because the one type of URB that isn't
likely to be complete when hcd_endpoint_disable() returns is a root-hub
URB.  Right now usb_rh_urb_dequeue() waits for them to complete, and it
assumes interrupts are enabled so it can wait.  But
hcd_endpoint_disable() calls it with interrupts disabled.

Now, it should be legal to unlink root-hub URBs with interrupts
disabled.  The solution is to move the waiting into
hcd_endpoint_disable(), where it belongs.  This patch (as754) does that.

It turns out to be completely safe to replace the del_timer_sync() with
a simple del_timer().  It doesn't matter if the timer routine is
running; hcd_root_hub_lock will synchronize the two threads and the
status URB will complete with an unlink error, as it should.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern 2006-08-11 16:01:45 -04:00 committed by Greg Kroah-Hartman
parent de06a3b842
commit 455b25fb20
1 changed files with 35 additions and 30 deletions
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65
drivers/usb/core/hcd.c
View File

@ -633,31 +633,20 @@ static int rh_urb_enqueue (struct usb_hcd *hcd, struct urb *urb)
/*-------------------------------------------------------------------------*/
/* Asynchronous unlinks of root-hub control URBs are legal, but they
* don't do anything. Status URB unlinks must be made in process context
* with interrupts enabled.
/* Unlinks of root-hub control URBs are legal, but they don't do anything
* since these URBs always execute synchronously.
*/
static int usb_rh_urb_dequeue (struct usb_hcd *hcd, struct urb *urb)
{
unsigned long flags;
if (usb_pipeendpoint(urb->pipe) == 0) { /* Control URB */
if (in_interrupt())
return 0; /* nothing to do */
spin_lock_irq(&urb->lock); /* from usb_kill_urb */
++urb->reject;
spin_unlock_irq(&urb->lock);
wait_event(usb_kill_urb_queue,
atomic_read(&urb->use_count) == 0);
spin_lock_irq(&urb->lock);
--urb->reject;
spin_unlock_irq(&urb->lock);
; /* Do nothing */
} else { /* Status URB */
if (!hcd->uses_new_polling)
del_timer_sync (&hcd->rh_timer);
local_irq_disable ();
del_timer (&hcd->rh_timer);
local_irq_save (flags);
spin_lock (&hcd_root_hub_lock);
if (urb == hcd->status_urb) {
hcd->status_urb = NULL;
@ -667,7 +656,7 @@ static int usb_rh_urb_dequeue (struct usb_hcd *hcd, struct urb *urb)
spin_unlock (&hcd_root_hub_lock);
if (urb)
usb_hcd_giveback_urb (hcd, urb, NULL);
local_irq_enable ();
local_irq_restore (flags);
}
return 0;
@ -1355,7 +1344,8 @@ static int hcd_unlink_urb (struct urb *urb, int status)
/*-------------------------------------------------------------------------*/
/* disables the endpoint: cancels any pending urbs, then synchronizes with
* the hcd to make sure all endpoint state is gone from hardware. use for
* the hcd to make sure all endpoint state is gone from hardware, and then
* waits until the endpoint's queue is completely drained. use for
* set_configuration, set_interface, driver removal, physical disconnect.
*
* example: a qh stored in ep->hcpriv, holding state related to endpoint
@ -1374,22 +1364,13 @@ hcd_endpoint_disable (struct usb_device *udev, struct usb_host_endpoint *ep)
local_irq_disable ();
/* FIXME move most of this into message.c as part of its
* endpoint disable logic
*/
/* ep is already gone from udev->ep_{in,out}[]; no more submits */
rescan:
spin_lock (&hcd_data_lock);
list_for_each_entry (urb, &ep->urb_list, urb_list) {
int tmp;
/* another cpu may be in hcd, spinning on hcd_data_lock
* to giveback() this urb. the races here should be
* small, but a full fix needs a new "can't submit"
* urb state.
* FIXME urb->reject should allow that...
*/
/* the urb may already have been unlinked */
if (urb->status != -EINPROGRESS)
continue;
usb_get_urb (urb);
@ -1431,6 +1412,30 @@ hcd_endpoint_disable (struct usb_device *udev, struct usb_host_endpoint *ep)
might_sleep ();
if (hcd->driver->endpoint_disable)
hcd->driver->endpoint_disable (hcd, ep);
/* Wait until the endpoint queue is completely empty. Most HCDs
* will have done this already in their endpoint_disable method,
* but some might not. And there could be root-hub control URBs
* still pending since they aren't affected by the HCDs'
* endpoint_disable methods.
*/
while (!list_empty (&ep->urb_list)) {
spin_lock_irq (&hcd_data_lock);
/* The list may have changed while we acquired the spinlock */
urb = NULL;
if (!list_empty (&ep->urb_list)) {
urb = list_entry (ep->urb_list.prev, struct urb,
urb_list);
usb_get_urb (urb);
}
spin_unlock_irq (&hcd_data_lock);
if (urb) {
usb_kill_urb (urb);
usb_put_urb (urb);
}
}
}
/*-------------------------------------------------------------------------*/