[PATCH 3.10 311/319] can: dev: fix deadlock reported after bus-off

Willy Tarreau
2017-02-05T19:48:40Z

From: Sergei Miroshnichenko <sergeimir@emcraft.com>

commit 9abefcb1aaa58b9d5aa40a8bb12c87d02415e4c8 upstream.

A timer was used to restart after the bus-off state, leading to a
relatively large can_restart() executed in an interrupt context,
which in turn sets up pinctrl. When this happens during system boot,
there is a high probability of grabbing the pinctrl_list_mutex,
which is locked already by the probe() of other device, making the
kernel suspect a deadlock condition [1].

To resolve this issue, the restart_timer is replaced by a delayed
work.

[1] https://github.com/victronenergy/venus/issues/24

Signed-off-by: Sergei Miroshnichenko <sergeimir@emcraft.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
drivers/net/can/dev.c | 27 +++++++++++++++++----------
include/linux/can/dev.h | 3 ++-
2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 464e5f6..284d751 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -22,6 +22,7 @@
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
+#include <linux/workqueue.h>
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/skb.h>
@@ -394,9 +395,8 @@ EXPORT_SYMBOL_GPL(can_free_echo_skb);
/*
* CAN device restart for bus-off recovery
*/
-static void can_restart(unsigned long data)
+static void can_restart(struct net_device *dev)
{
- struct net_device *dev = (struct net_device *)data;
struct can_priv *priv = netdev_priv(dev);
struct net_device_stats *stats = &dev->stats;
struct sk_buff *skb;
@@ -436,6 +436,14 @@ restart:
netdev_err(dev, "Error %d during restart", err);
}

+static void can_restart_work(struct work_struct *work)
+{
+ struct delayed_work *dwork = to_delayed_work(work);
+ struct can_priv *priv = container_of(dwork, struct can_priv, restart_work);
+
+ can_restart(priv->dev);
+}
+
int can_restart_now(struct net_device *dev)
{
struct can_priv *priv = netdev_priv(dev);
@@ -449,8 +457,8 @@ int can_restart_now(struct net_device *dev)
if (priv->state != CAN_STATE_BUS_OFF)
return -EBUSY;

- /* Runs as soon as possible in the timer context */
- mod_timer(&priv->restart_timer, jiffies);
+ cancel_delayed_work_sync(&priv->restart_work);
+ can_restart(dev);

return 0;
}
@@ -472,8 +480,8 @@ void can_bus_off(struct net_device *dev)
priv->can_stats.bus_off++;

if (priv->restart_ms)
- mod_timer(&priv->restart_timer,
- jiffies + (priv->restart_ms * HZ) / 1000);
+ schedule_delayed_work(&priv->restart_work,
+ msecs_to_jiffies(priv->restart_ms));
}
EXPORT_SYMBOL_GPL(can_bus_off);

@@ -556,6 +564,7 @@ struct net_device *alloc_candev(int sizeof_priv, unsigned int echo_skb_max)
return NULL;

priv = netdev_priv(dev);
+ priv->dev = dev;

if (echo_skb_max) {
priv->echo_skb_max = echo_skb_max;
@@ -565,7 +574,7 @@ struct net_device *alloc_candev(int sizeof_priv, unsigned int echo_skb_max)

priv->state = CAN_STATE_STOPPED;

- init_timer(&priv->restart_timer);
+ INIT_DELAYED_WORK(&priv->restart_work, can_restart_work);

return dev;
}
@@ -599,8 +608,6 @@ int open_candev(struct net_device *dev)
if (!netif_carrier_ok(dev))
netif_carrier_on(dev);

- setup_timer(&priv->restart_timer, can_restart, (unsigned long)dev);
-
return 0;
}
EXPORT_SYMBOL_GPL(open_candev);
@@ -615,7 +622,7 @@ void close_candev(struct net_device *dev)
{
struct can_priv *priv = netdev_priv(dev);

- del_timer_sync(&priv->restart_timer);
+ cancel_delayed_work_sync(&priv->restart_work);
can_flush_echo_skb(dev);
}
EXPORT_SYMBOL_GPL(close_candev);
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index fb0ab65..fb9fbe2 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -31,6 +31,7 @@ enum can_mode {
* CAN common private data
*/
struct can_priv {
+ struct net_device *dev;
struct can_device_stats can_stats;

struct can_bittiming bittiming;
@@ -42,7 +43,7 @@ struct can_priv {
u32 ctrlmode_supported;

int restart_ms;
- struct timer_list restart_timer;
+ struct delayed_work restart_work;

int (*do_set_bittiming)(struct net_device *dev);
int (*do_set_mode)(struct net_device *dev, enum can_mode mode);
--
2.8.0.rc2.1.gbe9624a