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Message-ID: <1395299705.5432.12.camel@linux-fkkt.site>
Date: Thu, 20 Mar 2014 08:15:05 +0100
From: Oliver Neukum <oneukum@...e.de>
To: Grant Grundler <grundler@...gle.com>
Cc: netdev <netdev@...r.kernel.org>, Freddy Xin <freddy@...x.com.tw>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
Allan Chou <allan@...x.com.tw>,
Julius Werner <jwerner@...omium.org>
Subject: Re: usbnet: driver_info->stop required to stop USB interrupts?
On Wed, 2014-03-19 at 17:58 -0700, Grant Grundler wrote:
> Oliver,
> So even with this additional change to usbnet_probe, the device is
> reporting a link but can't transmit packets.
> I've tried with three different USB dongles (AX88178, AX88772B, SMSC75xx).
>
> In the last case, I ran "ifconfig eth0 192.168.1.100" and then tried
> to ping 192.168.1.1. "ifconfig eth0" then reports "RX packets 0 bytes
> 0" and "TX packets 0 bytes 10796". The TX packets != bytes seems odd
> and suggests (to me) that data getting discarded someplace in the
> stack. I confirmed by running tcpdump on the other end of the link
> (192.168.1.1 side) and got nothing from 192.168.1.100.
>
> I believe the "10796" TX bytes is due to the connection manager
> "trying really hard" to get an IP address (via DHCP).
>
> Your patch looks like it should work. But it's missing something and I
> don't have a clue what it is. Ideas?
I have an idea. Could you test this patch?
Regards
Oliver
>From 9a4c4a62c113c5a1abd8345418ccbf95706efdd2 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@...e.de>
Date: Tue, 11 Mar 2014 09:59:48 +0100
Subject: [PATCH] usbnet: include wait queue head in device structure
This fixes a race which happens by freeing an object on the stack.
Quoting Julius:
> The issue is
> that it calls usbnet_terminate_urbs() before that, which temporarily
> installs a waitqueue in dev->wait in order to be able to wait on the
> tasklet to run and finish up some queues. The waiting itself looks
> okay, but the access to 'dev->wait' is totally unprotected and can
> race arbitrarily. I think in this case usbnet_bh() managed to succeed
> it's dev->wait check just before usbnet_terminate_urbs() sets it back
> to NULL. The latter then finishes and the waitqueue_t structure on its
> stack gets overwritten by other functions halfway through the
> wake_up() call in usbnet_bh().
The fix is to just not allocate the data structure on the stack.
As dev->wait is abused as a flag it also takes a runtime PM change
to fix this bug.
Signed-off-by: Oliver Neukum <oneukum@...e.de>
---
drivers/net/usb/usbnet.c | 29 ++++++++++++++++-------------
include/linux/usb/usbnet.h | 2 +-
2 files changed, 17 insertions(+), 14 deletions(-)
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index dd10d58..a8da1af 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -752,14 +752,12 @@ EXPORT_SYMBOL_GPL(usbnet_unlink_rx_urbs);
// precondition: never called in_interrupt
static void usbnet_terminate_urbs(struct usbnet *dev)
{
- DECLARE_WAIT_QUEUE_HEAD_ONSTACK(unlink_wakeup);
DECLARE_WAITQUEUE(wait, current);
int temp;
/* ensure there are no more active urbs */
- add_wait_queue(&unlink_wakeup, &wait);
+ add_wait_queue(&dev->wait, &wait);
set_current_state(TASK_UNINTERRUPTIBLE);
- dev->wait = &unlink_wakeup;
temp = unlink_urbs(dev, &dev->txq) +
unlink_urbs(dev, &dev->rxq);
@@ -773,15 +771,14 @@ static void usbnet_terminate_urbs(struct usbnet *dev)
"waited for %d urb completions\n", temp);
}
set_current_state(TASK_RUNNING);
- dev->wait = NULL;
- remove_wait_queue(&unlink_wakeup, &wait);
+ remove_wait_queue(&dev->wait, &wait);
}
int usbnet_stop (struct net_device *net)
{
struct usbnet *dev = netdev_priv(net);
struct driver_info *info = dev->driver_info;
- int retval;
+ int retval, pm;
clear_bit(EVENT_DEV_OPEN, &dev->flags);
netif_stop_queue (net);
@@ -791,6 +788,8 @@ int usbnet_stop (struct net_device *net)
net->stats.rx_packets, net->stats.tx_packets,
net->stats.rx_errors, net->stats.tx_errors);
+ /* to not race resume */
+ pm = usb_autopm_get_interface(dev->intf);
/* allow minidriver to stop correctly (wireless devices to turn off
* radio etc) */
if (info->stop) {
@@ -817,6 +816,9 @@ int usbnet_stop (struct net_device *net)
dev->flags = 0;
del_timer_sync (&dev->delay);
tasklet_kill (&dev->bh);
+ if (!pm)
+ usb_autopm_put_interface(dev->intf);
+
if (info->manage_power &&
!test_and_clear_bit(EVENT_NO_RUNTIME_PM, &dev->flags))
info->manage_power(dev, 0);
@@ -1438,10 +1440,9 @@ static void usbnet_bh (unsigned long param)
clear_bit(EVENT_RX_KILL, &dev->flags);
// waiting for all pending urbs to complete?
- if (dev->wait) {
- if ((dev->txq.qlen + dev->rxq.qlen + dev->done.qlen) == 0) {
- wake_up (dev->wait);
- }
+ if (waitqueue_active(&dev->wait)) {
+ if (dev->txq.qlen + dev->rxq.qlen + dev->done.qlen == 0)
+ wake_up_all(&dev->wait);
// or are we maybe short a few urbs?
} else if (netif_running (dev->net) &&
@@ -1580,6 +1581,7 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
dev->driver_name = name;
dev->msg_enable = netif_msg_init (msg_level, NETIF_MSG_DRV
| NETIF_MSG_PROBE | NETIF_MSG_LINK);
+ init_waitqueue_head(&dev->wait);
skb_queue_head_init (&dev->rxq);
skb_queue_head_init (&dev->txq);
skb_queue_head_init (&dev->done);
@@ -1791,9 +1793,10 @@ int usbnet_resume (struct usb_interface *intf)
spin_unlock_irq(&dev->txq.lock);
if (test_bit(EVENT_DEV_OPEN, &dev->flags)) {
- /* handle remote wakeup ASAP */
- if (!dev->wait &&
- netif_device_present(dev->net) &&
+ /* handle remote wakeup ASAP
+ * we cannot race against stop
+ */
+ if (netif_device_present(dev->net) &&
!timer_pending(&dev->delay) &&
!test_bit(EVENT_RX_HALT, &dev->flags))
rx_alloc_submit(dev, GFP_NOIO);
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index e303eef..0662e98 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -30,7 +30,7 @@ struct usbnet {
struct driver_info *driver_info;
const char *driver_name;
void *driver_priv;
- wait_queue_head_t *wait;
+ wait_queue_head_t wait;
struct mutex phy_mutex;
unsigned char suspend_count;
unsigned char pkt_cnt, pkt_err;
--
1.8.4.5
--
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