[3.13.y.z extended stable] Patch "USB: EHCI: unlink QHs even after the controller has stopped" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Thu Oct 9 20:51:38 UTC 2014

This is a note to let you know that I have just added a patch titled

    USB: EHCI: unlink QHs even after the controller has stopped

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:


This patch is scheduled to be released in version

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see



>From 19052234e8abcc8af1736036d02412346093392d Mon Sep 17 00:00:00 2001
From: Alan Stern <stern at rowland.harvard.edu>
Date: Wed, 17 Sep 2014 11:23:54 -0400
Subject: USB: EHCI: unlink QHs even after the controller has stopped

commit 7312b5ddd47fee2356baa78c5516ef8e04eed452 upstream.

Old code in ehci-hcd tries to expedite disabling endpoints after the
controller has stopped, by destroying the endpoint's associated QH
without first unlinking the QH.  This was necessary back when the
driver wasn't so careful about keeping track of the controller's

But now we are careful about it, and the driver knows that when the
controller isn't running, no unlinking delay is needed.  Furthermore,
skipping the unlink step will trigger a BUG() in qh_destroy() when the
preceding QH is released, because the link pointer will be non-NULL.

Removing the lines that skip the unlinking step and go directly to
QH_STATE_IDLE fixes the problem.

Signed-off-by: Alan Stern <stern at rowland.harvard.edu>
Reported-by: Joe Lawrence <joe.lawrence at stratus.com>
Tested-by: Joe Lawrence <joe.lawrence at stratus.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 drivers/usb/host/ehci-hcd.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 4dfd6fb..86e6d39 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -973,8 +973,6 @@ rescan:

 	qh->exception = 1;
-	if (ehci->rh_state < EHCI_RH_RUNNING)
-		qh->qh_state = QH_STATE_IDLE;
 	switch (qh->qh_state) {

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