[patch 60/71] USB: EHCI: fix two new bugs related to Clear-TT-Buffer

From: Greg KH
Date: Fri Sep 04 2009 - 20:24:48 EST

2.6.30-stable review patch. If anyone has any objections, please let us know.

From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

commit 7a0f0d951273eee889c2441846842348ebc00a2a upstream.

This patch (as1273) fixes two(!) bugs introduced by the new
Clear-TT-Buffer implementation in ehci-hcd.

It is now possible for an idle QH to have some URBs on its
queue -- this will happen if a Clear-TT-Buffer is pending for
the QH's endpoint. Consequently we should not issue a warning
when someone tries to unlink an URB from an idle QH; instead
we should process the request immediately.

The refcounts for QHs could get messed up, because
submit_async() would increment the refcount when calling
qh_link_async() and qh_link_async() would then refuse to link
the QH into the schedule if a Clear-TT-Buffer was pending.
Instead we should increment the refcount only when the QH
actually is added to the schedule. The current code tries to
be clever by leaving the refcount alone if an unlink is
immediately followed by a relink; the patch changes this to an
unconditional decrement and increment (although they occur in
the opposite order).

Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
CC: David Brownell <david-b@xxxxxxxxxxx>
Tested-by: Manuel Lauss <manuel.lauss@xxxxxxxxx>
Tested-by: Matthijs Kooijman <matthijs@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

drivers/usb/host/ehci-hcd.c | 3 ++-
drivers/usb/host/ehci-q.c | 6 +++---
2 files changed, 5 insertions(+), 4 deletions(-)

--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -903,7 +903,8 @@ static int ehci_urb_dequeue(struct usb_h
/* already started */
- WARN_ON(1);
+ /* QH might be waiting for a Clear-TT-Buffer */
+ qh_completions(ehci, qh);
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -938,6 +938,7 @@ static void qh_link_async (struct ehci_h
head->qh_next.qh = qh;
head->hw_next = dma;

+ qh_get(qh);
qh->xacterrs = QH_XACTERR_MAX;
qh->qh_state = QH_STATE_LINKED;
/* qtd completions reported later by interrupt */
@@ -1078,7 +1079,7 @@ submit_async (
* the HC and TT handle it when the TT has a buffer ready.
if (likely (qh->qh_state == QH_STATE_IDLE))
- qh_link_async (ehci, qh_get (qh));
+ qh_link_async(ehci, qh);
spin_unlock_irqrestore (&ehci->lock, flags);
if (unlikely (qh == NULL))
@@ -1113,8 +1114,6 @@ static void end_unlink_async (struct ehc
&& HC_IS_RUNNING (ehci_to_hcd(ehci)->state))
qh_link_async (ehci, qh);
else {
- qh_put (qh); // refcount from async list
/* it's not free to turn the async schedule on/off; leave it
* active but idle for a while once it empties.
@@ -1122,6 +1121,7 @@ static void end_unlink_async (struct ehc
&& ehci->async->qh_next.qh == NULL)
timer_action (ehci, TIMER_ASYNC_OFF);
+ qh_put(qh); /* refcount from async list */

if (next) {
ehci->reclaim = NULL;

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