This is a note to let you know that I've just added the patch titled
USB: dummy-hcd: Fix deadlock caused by disconnect detection
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From ab219221a5064abfff9f78c323c4a257b16cdb81 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Date: Fri, 6 Oct 2017 10:27:44 -0400
Subject: USB: dummy-hcd: Fix deadlock caused by disconnect detection
The dummy-hcd driver calls the gadget driver's disconnect callback
under the wrong conditions. It should invoke the callback when Vbus
power is turned off, but instead it does so when the D+ pullup is
turned off.
This can cause a deadlock in the composite core when a gadget driver
is unregistered:
[ 88.361471] ============================================
[ 88.362014] WARNING: possible recursive locking detected
[ 88.362580] 4.14.0-rc2+ #9 Not tainted
[ 88.363010] --------------------------------------------
[ 88.363561] v4l_id/526 is trying to acquire lock:
[ 88.364062] (&(&cdev->lock)->rlock){....}, at: [<ffffffffa0547e03>] composite_disconnect+0x43/0x100 [libcomposite]
[ 88.365051]
[ 88.365051] but task is already holding lock:
[ 88.365826] (&(&cdev->lock)->rlock){....}, at: [<ffffffffa0547b09>] usb_function_deactivate+0x29/0x80 [libcomposite]
[ 88.366858]
[ 88.366858] other info that might help us debug this:
[ 88.368301] Possible unsafe locking scenario:
[ 88.368301]
[ 88.369304] CPU0
[ 88.369701] ----
[ 88.370101] lock(&(&cdev->lock)->rlock);
[ 88.370623] lock(&(&cdev->lock)->rlock);
[ 88.371145]
[ 88.371145] *** DEADLOCK ***
[ 88.371145]
[ 88.372211] May be due to missing lock nesting notation
[ 88.372211]
[ 88.373191] 2 locks held by v4l_id/526:
[ 88.373715] #0: (&(&cdev->lock)->rlock){....}, at: [<ffffffffa0547b09>] usb_function_deactivate+0x29/0x80 [libcomposite]
[ 88.374814] #1: (&(&dum_hcd->dum->lock)->rlock){....}, at: [<ffffffffa05bd48d>] dummy_pullup+0x7d/0xf0 [dummy_hcd]
[ 88.376289]
[ 88.376289] stack backtrace:
[ 88.377726] CPU: 0 PID: 526 Comm: v4l_id Not tainted 4.14.0-rc2+ #9
[ 88.378557] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 88.379504] Call Trace:
[ 88.380019] dump_stack+0x86/0xc7
[ 88.380605] __lock_acquire+0x841/0x1120
[ 88.381252] lock_acquire+0xd5/0x1c0
[ 88.381865] ? composite_disconnect+0x43/0x100 [libcomposite]
[ 88.382668] _raw_spin_lock_irqsave+0x40/0x54
[ 88.383357] ? composite_disconnect+0x43/0x100 [libcomposite]
[ 88.384290] composite_disconnect+0x43/0x100 [libcomposite]
[ 88.385490] set_link_state+0x2d4/0x3c0 [dummy_hcd]
[ 88.386436] dummy_pullup+0xa7/0xf0 [dummy_hcd]
[ 88.387195] usb_gadget_disconnect+0xd8/0x160 [udc_core]
[ 88.387990] usb_gadget_deactivate+0xd3/0x160 [udc_core]
[ 88.388793] usb_function_deactivate+0x64/0x80 [libcomposite]
[ 88.389628] uvc_function_disconnect+0x1e/0x40 [usb_f_uvc]
This patch changes the code to test the port-power status bit rather
than the port-connect status bit when deciding whether to isue the
callback.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Reported-by: David Tulloh <david@xxxxxxxxxxxx>
CC: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
---
drivers/usb/gadget/udc/dummy_hcd.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
index b17618a55f1b..f04e91ef9e7c 100644
--- a/drivers/usb/gadget/udc/dummy_hcd.c
+++ b/drivers/usb/gadget/udc/dummy_hcd.c
@@ -419,6 +419,7 @@ static void set_link_state_by_speed(struct dummy_hcd *dum_hcd)
static void set_link_state(struct dummy_hcd *dum_hcd)
{
struct dummy *dum = dum_hcd->dum;
+ unsigned int power_bit;
dum_hcd->active = 0;
if (dum->pullup)
@@ -429,17 +430,19 @@ static void set_link_state(struct dummy_hcd *dum_hcd)
return;
set_link_state_by_speed(dum_hcd);
+ power_bit = (dummy_hcd_to_hcd(dum_hcd)->speed == HCD_USB3 ?
+ USB_SS_PORT_STAT_POWER : USB_PORT_STAT_POWER);
if ((dum_hcd->port_status & USB_PORT_STAT_ENABLE) == 0 ||
dum_hcd->active)
dum_hcd->resuming = 0;
/* Currently !connected or in reset */
- if ((dum_hcd->port_status & USB_PORT_STAT_CONNECTION) == 0 ||
+ if ((dum_hcd->port_status & power_bit) == 0 ||
(dum_hcd->port_status & USB_PORT_STAT_RESET) != 0) {
- unsigned disconnect = USB_PORT_STAT_CONNECTION &
+ unsigned int disconnect = power_bit &
dum_hcd->old_status & (~dum_hcd->port_status);
- unsigned reset = USB_PORT_STAT_RESET &
+ unsigned int reset = USB_PORT_STAT_RESET &
(~dum_hcd->old_status) & dum_hcd->port_status;
/* Report reset and disconnect events to the driver */
--
2.14.2