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Date: Mon, 08 Jul 2013 11:23:04 +0400
From: Konstantin Khlebnikov <khlebnikov@...nvz.org>
To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Dmitry Tarnyagin <dmitry.tarnyagin@...kless.no>
Subject: [PATCH] drivers/net: caif: fix wrong rtnl_is_locked() usage
rtnl_is_locked() doesn't check who holds this lock, it just tells that it's
locked right now. if caif::ldisc_close really can be called under rtrnl_lock
then it should release net device in other context because there is no way
to grab rtnl_lock without deadlock.
This patch adds work which releases these devices. Also this patch fixes calling
dev_close/unregister_netdevice without rtnl_lock from caif_ser_exit().
Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc: Dmitry Tarnyagin <dmitry.tarnyagin@...kless.no>
---
drivers/net/caif/caif_serial.c | 61 ++++++++++++++++++++++++++--------------
1 file changed, 39 insertions(+), 22 deletions(-)
diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c
index 77be3cb..34dea95 100644
--- a/drivers/net/caif/caif_serial.c
+++ b/drivers/net/caif/caif_serial.c
@@ -35,8 +35,9 @@ MODULE_ALIAS_LDISC(N_CAIF);
#define OFF 0
#define CAIF_MAX_MTU 4096
-/*This list is protected by the rtnl lock. */
+static DEFINE_SPINLOCK(ser_lock);
static LIST_HEAD(ser_list);
+static LIST_HEAD(ser_release_list);
static bool ser_loop;
module_param(ser_loop, bool, S_IRUGO);
@@ -308,6 +309,28 @@ static void ldisc_tx_wakeup(struct tty_struct *tty)
}
+static void ser_release(struct work_struct *work)
+{
+ struct list_head list;
+ struct ser_device *ser, *tmp;
+
+ spin_lock(&ser_lock);
+ list_replace_init(&ser_release_list, &list);
+ spin_unlock(&ser_lock);
+
+ if (!list_empty(&list)) {
+ rtnl_lock();
+ list_for_each_entry_safe(ser, tmp, &list, node) {
+ dev_close(ser->dev);
+ unregister_netdevice(ser->dev);
+ debugfs_deinit(ser);
+ }
+ rtnl_unlock();
+ }
+}
+
+static DECLARE_WORK(ser_release_work, ser_release);
+
static int ldisc_open(struct tty_struct *tty)
{
struct ser_device *ser;
@@ -321,6 +344,9 @@ static int ldisc_open(struct tty_struct *tty)
if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
return -EPERM;
+ /* release devices to avoid name collision */
+ ser_release(NULL);
+
sprintf(name, "cf%s", tty->name);
dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
if (!dev)
@@ -341,7 +367,9 @@ static int ldisc_open(struct tty_struct *tty)
return -ENODEV;
}
+ spin_lock(&ser_lock);
list_add(&ser->node, &ser_list);
+ spin_unlock(&ser_lock);
rtnl_unlock();
netif_stop_queue(dev);
update_tty_status(ser);
@@ -351,19 +379,13 @@ static int ldisc_open(struct tty_struct *tty)
static void ldisc_close(struct tty_struct *tty)
{
struct ser_device *ser = tty->disc_data;
- /* Remove may be called inside or outside of rtnl_lock */
- int islocked = rtnl_is_locked();
- if (!islocked)
- rtnl_lock();
- /* device is freed automagically by net-sysfs */
- dev_close(ser->dev);
- unregister_netdevice(ser->dev);
- list_del(&ser->node);
- debugfs_deinit(ser);
tty_kref_put(ser->tty);
- if (!islocked)
- rtnl_unlock();
+
+ spin_lock(&ser_lock);
+ list_move(&ser->node, &ser_release_list);
+ spin_unlock(&ser_lock);
+ schedule_work(&ser_release_work);
}
/* The line discipline structure. */
@@ -438,16 +460,11 @@ static int __init caif_ser_init(void)
static void __exit caif_ser_exit(void)
{
- struct ser_device *ser = NULL;
- struct list_head *node;
- struct list_head *_tmp;
-
- list_for_each_safe(node, _tmp, &ser_list) {
- ser = list_entry(node, struct ser_device, node);
- dev_close(ser->dev);
- unregister_netdevice(ser->dev);
- list_del(node);
- }
+ spin_lock(&ser_lock);
+ list_splice(&ser_list, &ser_release_list);
+ spin_unlock(&ser_lock);
+ ser_release(NULL);
+ cancel_work_sync(&ser_release_work);
tty_unregister_ldisc(N_CAIF);
debugfs_remove_recursive(debugfsdir);
}
--
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