hci_ldsic nested locking problem

Message ID 20140320182528.GE3959@saruman.home
State New
Headers show

Commit Message

Felipe Balbi March 20, 2014, 6:25 p.m.
On Thu, Mar 20, 2014 at 02:21:17PM -0400, Peter Hurley wrote:
> On 03/20/2014 02:11 PM, Felipe Balbi wrote:
> >On Thu, Mar 20, 2014 at 01:31:40PM -0400, Peter Hurley wrote:
> >>[ +cc Huang Shijie ]
> >>
> >>On 03/20/2014 01:16 PM, Felipe Balbi wrote:
> >>>On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote:
> >>>>On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote:
> >>>>>Hi,
> >>>>>
> >>>>>when 8250 driver calls uart_write_wakeup(), the tty port lock is already
> >>>>>taken. hci_ldisc.c's implementation of ->write_wakeup() calls
> >>>>>tty->ops->write() to actually send the characters, but that call will
> >>>>>try to acquire the same port lock again.
> >>>>>
> >>>>>Looking at other line disciplines that looks like a bug in hci_ldisc.c.
> >>>>>Am I correct to assume that ->write_wakeup() is supposed to *just*
> >>>>>wakeup the bottom half so we handle ->write() in another context ?
> >>>>>
> >>>>>Is it legal to call tty->ops->write() from within ->write_wakeup() ?
> >>>>
> >>>>It isn't because you might send all the bytes and go
> >>>>
> >>>>	write
> >>>>		write_wakeup
> >>>>			write
> >>>>				write wakeup
> >>>>					...
> >>>>
> >>>>and recurse
> >>>
> >>>cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do
> >>>you want this to be sorted out ?
> >>
> >>hci_uart_tx_wakeup() should perform the I/O as work.
> >>FWIW, this was reported by Huang Shijie back on Dec 6.
> >>
> >>I'd fix it but I have no way to test it.
> >
> >here's a build-tested only patch which is waiting for testing from other
> >colleagues who've got a platform to reproduce the problem:
> 
> Where's the cancel_work_sync() on teardown?

here, as a patch too this time:

From 3ee6b74833f154df64a6164476b854846206a3f2 Mon Sep 17 00:00:00 2001
From: Felipe Balbi <balbi@ti.com>
Date: Thu, 20 Mar 2014 13:20:10 -0500
Subject: [PATCH] bluetooth: hci_ldisc: fix deadlock condition

LDISCs shouldn't call tty->ops->write() from within
->write_wakeup().

->write_wakeup() is called with port lock taken and
IRQs disabled, tty->ops->write() will try to acquire
the same port lock and we will deadlock.

Signed-off-by: Felipe Balbi <balbi@ti.com>
---
 drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
 drivers/bluetooth/hci_uart.h  |  1 +
 2 files changed, 16 insertions(+), 5 deletions(-)

Comments

Felipe Balbi March 20, 2014, 7:01 p.m. | #1
On Thu, Mar 20, 2014 at 01:25:28PM -0500, Felipe Balbi wrote:
> On Thu, Mar 20, 2014 at 02:21:17PM -0400, Peter Hurley wrote:
> > On 03/20/2014 02:11 PM, Felipe Balbi wrote:
> > >On Thu, Mar 20, 2014 at 01:31:40PM -0400, Peter Hurley wrote:
> > >>[ +cc Huang Shijie ]
> > >>
> > >>On 03/20/2014 01:16 PM, Felipe Balbi wrote:
> > >>>On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote:
> > >>>>On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote:
> > >>>>>Hi,
> > >>>>>
> > >>>>>when 8250 driver calls uart_write_wakeup(), the tty port lock is already
> > >>>>>taken. hci_ldisc.c's implementation of ->write_wakeup() calls
> > >>>>>tty->ops->write() to actually send the characters, but that call will
> > >>>>>try to acquire the same port lock again.
> > >>>>>
> > >>>>>Looking at other line disciplines that looks like a bug in hci_ldisc.c.
> > >>>>>Am I correct to assume that ->write_wakeup() is supposed to *just*
> > >>>>>wakeup the bottom half so we handle ->write() in another context ?
> > >>>>>
> > >>>>>Is it legal to call tty->ops->write() from within ->write_wakeup() ?
> > >>>>
> > >>>>It isn't because you might send all the bytes and go
> > >>>>
> > >>>>	write
> > >>>>		write_wakeup
> > >>>>			write
> > >>>>				write wakeup
> > >>>>					...
> > >>>>
> > >>>>and recurse
> > >>>
> > >>>cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do
> > >>>you want this to be sorted out ?
> > >>
> > >>hci_uart_tx_wakeup() should perform the I/O as work.
> > >>FWIW, this was reported by Huang Shijie back on Dec 6.
> > >>
> > >>I'd fix it but I have no way to test it.
> > >
> > >here's a build-tested only patch which is waiting for testing from other
> > >colleagues who've got a platform to reproduce the problem:
> > 
> > Where's the cancel_work_sync() on teardown?
> 
> here, as a patch too this time:
> 
> From 3ee6b74833f154df64a6164476b854846206a3f2 Mon Sep 17 00:00:00 2001
> From: Felipe Balbi <balbi@ti.com>
> Date: Thu, 20 Mar 2014 13:20:10 -0500
> Subject: [PATCH] bluetooth: hci_ldisc: fix deadlock condition
> 
> LDISCs shouldn't call tty->ops->write() from within
> ->write_wakeup().
> 
> ->write_wakeup() is called with port lock taken and
> IRQs disabled, tty->ops->write() will try to acquire
> the same port lock and we will deadlock.
> 
> Signed-off-by: Felipe Balbi <balbi@ti.com>
> ---
>  drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
>  drivers/bluetooth/hci_uart.h  |  1 +
>  2 files changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> index 6e06f6f..ecdd765 100644
> --- a/drivers/bluetooth/hci_ldisc.c
> +++ b/drivers/bluetooth/hci_ldisc.c
> @@ -118,10 +118,6 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu)
>  
>  int hci_uart_tx_wakeup(struct hci_uart *hu)
>  {
> -	struct tty_struct *tty = hu->tty;
> -	struct hci_dev *hdev = hu->hdev;
> -	struct sk_buff *skb;
> -
>  	if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) {
>  		set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
>  		return 0;
> @@ -129,6 +125,18 @@ int hci_uart_tx_wakeup(struct hci_uart *hu)
>  
>  	BT_DBG("");
>  
> +	schedule_work(&hu->write_work);
> +
> +	return 0;
> +}
> +
> +static void hci_uart_write_work(struct work_struct *work)
> +{
> +	struct hci_uart *hu = container_of(work, struct hci_uart, init_ready);
> +	struct tty_struct *tty = hu->tty;
> +	struct hci_dev *hdev = hu->hdev;
> +	struct sk_buff *skb;
> +
>  restart:
>  	clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
>  
> @@ -153,7 +161,6 @@ restart:
>  		goto restart;
>  
>  	clear_bit(HCI_UART_SENDING, &hu->tx_state);
> -	return 0;
>  }
>  
>  static void hci_uart_init_work(struct work_struct *work)
> @@ -281,6 +288,7 @@ static int hci_uart_tty_open(struct tty_struct *tty)
>  	tty->receive_room = 65536;
>  
>  	INIT_WORK(&hu->init_ready, hci_uart_init_work);
> +	INIT_WORK(&hu->write_work, hci_uart_write_work);
>  
>  	spin_lock_init(&hu->rx_lock);
>  
> @@ -318,6 +326,8 @@ static void hci_uart_tty_close(struct tty_struct *tty)
>  	if (hdev)
>  		hci_uart_close(hdev);
>  
> +	cancel_work_sync(&hy->write_work);

forgot to commit, darn it
Peter Hurley March 20, 2014, 7:16 p.m. | #2
On 03/20/2014 02:25 PM, Felipe Balbi wrote:
> On Thu, Mar 20, 2014 at 02:21:17PM -0400, Peter Hurley wrote:
>> On 03/20/2014 02:11 PM, Felipe Balbi wrote:
>>> On Thu, Mar 20, 2014 at 01:31:40PM -0400, Peter Hurley wrote:
>>>> [ +cc Huang Shijie ]
>>>>
>>>> On 03/20/2014 01:16 PM, Felipe Balbi wrote:
>>>>> On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote:
>>>>>> On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> when 8250 driver calls uart_write_wakeup(), the tty port lock is already
>>>>>>> taken. hci_ldisc.c's implementation of ->write_wakeup() calls
>>>>>>> tty->ops->write() to actually send the characters, but that call will
>>>>>>> try to acquire the same port lock again.
>>>>>>>
>>>>>>> Looking at other line disciplines that looks like a bug in hci_ldisc.c.
>>>>>>> Am I correct to assume that ->write_wakeup() is supposed to *just*
>>>>>>> wakeup the bottom half so we handle ->write() in another context ?
>>>>>>>
>>>>>>> Is it legal to call tty->ops->write() from within ->write_wakeup() ?
>>>>>>
>>>>>> It isn't because you might send all the bytes and go
>>>>>>
>>>>>> 	write
>>>>>> 		write_wakeup
>>>>>> 			write
>>>>>> 				write wakeup
>>>>>> 					...
>>>>>>
>>>>>> and recurse
>>>>>
>>>>> cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do
>>>>> you want this to be sorted out ?
>>>>
>>>> hci_uart_tx_wakeup() should perform the I/O as work.
>>>> FWIW, this was reported by Huang Shijie back on Dec 6.
>>>>
>>>> I'd fix it but I have no way to test it.
>>>
>>> here's a build-tested only patch which is waiting for testing from other
>>> colleagues who've got a platform to reproduce the problem:
>>
>> Where's the cancel_work_sync() on teardown?
>
> here, as a patch too this time:

Thanks. Minor edits below but, strictly speaking, not necessary.

Reviewed-by: Peter Hurley <peter@hurleysoftware.com>


>  From 3ee6b74833f154df64a6164476b854846206a3f2 Mon Sep 17 00:00:00 2001
> From: Felipe Balbi <balbi@ti.com>
> Date: Thu, 20 Mar 2014 13:20:10 -0500
> Subject: [PATCH] bluetooth: hci_ldisc: fix deadlock condition
>
> LDISCs shouldn't call tty->ops->write() from within
> ->write_wakeup().
>
> ->write_wakeup() is called with port lock taken and
> IRQs disabled, tty->ops->write() will try to acquire
> the same port lock and we will deadlock.
>

I know you found it independently but ?

Reported-by: Huang Shijie <b32955@freescale.com>

> Signed-off-by: Felipe Balbi <balbi@ti.com>
> ---
>   drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
>   drivers/bluetooth/hci_uart.h  |  1 +
>   2 files changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> index 6e06f6f..ecdd765 100644
> --- a/drivers/bluetooth/hci_ldisc.c
> +++ b/drivers/bluetooth/hci_ldisc.c
> @@ -118,10 +118,6 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu)
>
>   int hci_uart_tx_wakeup(struct hci_uart *hu)
>   {
> -	struct tty_struct *tty = hu->tty;
> -	struct hci_dev *hdev = hu->hdev;
> -	struct sk_buff *skb;
> -
>   	if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) {
>   		set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
>   		return 0;
> @@ -129,6 +125,18 @@ int hci_uart_tx_wakeup(struct hci_uart *hu)
>
>   	BT_DBG("");
>
> +	schedule_work(&hu->write_work);
> +
> +	return 0;
> +}
> +
> +static void hci_uart_write_work(struct work_struct *work)
> +{
> +	struct hci_uart *hu = container_of(work, struct hci_uart, init_ready);
> +	struct tty_struct *tty = hu->tty;
> +	struct hci_dev *hdev = hu->hdev;
> +	struct sk_buff *skb;
> +

+	/* FIXME: if bad skb length or tty->ops->write() returns < 0 ??? */

>   restart:
>   	clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
>
> @@ -153,7 +161,6 @@ restart:
>   		goto restart;
>
>   	clear_bit(HCI_UART_SENDING, &hu->tx_state);
> -	return 0;
>   }
>
>   static void hci_uart_init_work(struct work_struct *work)
> @@ -281,6 +288,7 @@ static int hci_uart_tty_open(struct tty_struct *tty)
>   	tty->receive_room = 65536;
>
>   	INIT_WORK(&hu->init_ready, hci_uart_init_work);
> +	INIT_WORK(&hu->write_work, hci_uart_write_work);
>
>   	spin_lock_init(&hu->rx_lock);
>
> @@ -318,6 +326,8 @@ static void hci_uart_tty_close(struct tty_struct *tty)
>   	if (hdev)
>   		hci_uart_close(hdev);
>
> +	cancel_work_sync(&hy->write_work);
> +
>   	if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) {
>   		if (hdev) {
>   			if (test_bit(HCI_UART_REGISTERED, &hu->flags))
> diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
> index fffa61f..12df101 100644
> --- a/drivers/bluetooth/hci_uart.h
> +++ b/drivers/bluetooth/hci_uart.h
> @@ -68,6 +68,7 @@ struct hci_uart {
>   	unsigned long		hdev_flags;
>
>   	struct work_struct	init_ready;
> +	struct work_struct	write_work;
>
>   	struct hci_uart_proto	*proto;
>   	void			*priv;
>

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Felipe Balbi March 20, 2014, 7:25 p.m. | #3
Hi,

On Thu, Mar 20, 2014 at 03:16:35PM -0400, Peter Hurley wrote:
> On 03/20/2014 02:25 PM, Felipe Balbi wrote:
> >On Thu, Mar 20, 2014 at 02:21:17PM -0400, Peter Hurley wrote:
> >>On 03/20/2014 02:11 PM, Felipe Balbi wrote:
> >>>On Thu, Mar 20, 2014 at 01:31:40PM -0400, Peter Hurley wrote:
> >>>>[ +cc Huang Shijie ]
> >>>>
> >>>>On 03/20/2014 01:16 PM, Felipe Balbi wrote:
> >>>>>On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote:
> >>>>>>On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote:
> >>>>>>>Hi,
> >>>>>>>
> >>>>>>>when 8250 driver calls uart_write_wakeup(), the tty port lock is already
> >>>>>>>taken. hci_ldisc.c's implementation of ->write_wakeup() calls
> >>>>>>>tty->ops->write() to actually send the characters, but that call will
> >>>>>>>try to acquire the same port lock again.
> >>>>>>>
> >>>>>>>Looking at other line disciplines that looks like a bug in hci_ldisc.c.
> >>>>>>>Am I correct to assume that ->write_wakeup() is supposed to *just*
> >>>>>>>wakeup the bottom half so we handle ->write() in another context ?
> >>>>>>>
> >>>>>>>Is it legal to call tty->ops->write() from within ->write_wakeup() ?
> >>>>>>
> >>>>>>It isn't because you might send all the bytes and go
> >>>>>>
> >>>>>>	write
> >>>>>>		write_wakeup
> >>>>>>			write
> >>>>>>				write wakeup
> >>>>>>					...
> >>>>>>
> >>>>>>and recurse
> >>>>>
> >>>>>cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do
> >>>>>you want this to be sorted out ?
> >>>>
> >>>>hci_uart_tx_wakeup() should perform the I/O as work.
> >>>>FWIW, this was reported by Huang Shijie back on Dec 6.
> >>>>
> >>>>I'd fix it but I have no way to test it.
> >>>
> >>>here's a build-tested only patch which is waiting for testing from other
> >>>colleagues who've got a platform to reproduce the problem:
> >>
> >>Where's the cancel_work_sync() on teardown?
> >
> >here, as a patch too this time:
> 
> Thanks. Minor edits below but, strictly speaking, not necessary.
> 
> Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
> 
> 
> > From 3ee6b74833f154df64a6164476b854846206a3f2 Mon Sep 17 00:00:00 2001
> >From: Felipe Balbi <balbi@ti.com>
> >Date: Thu, 20 Mar 2014 13:20:10 -0500
> >Subject: [PATCH] bluetooth: hci_ldisc: fix deadlock condition
> >
> >LDISCs shouldn't call tty->ops->write() from within
> >->write_wakeup().
> >
> >->write_wakeup() is called with port lock taken and
> >IRQs disabled, tty->ops->write() will try to acquire
> >the same port lock and we will deadlock.
> >
> 
> I know you found it independently but ?
> 
> Reported-by: Huang Shijie <b32955@freescale.com>

I will never add any *-by tags without seeing it in the mailing list.
Now I can add it to the patch and send it as a real patch (git
send-email it).

> >Signed-off-by: Felipe Balbi <balbi@ti.com>
> >---
> >  drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
> >  drivers/bluetooth/hci_uart.h  |  1 +
> >  2 files changed, 16 insertions(+), 5 deletions(-)
> >
> >diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> >index 6e06f6f..ecdd765 100644
> >--- a/drivers/bluetooth/hci_ldisc.c
> >+++ b/drivers/bluetooth/hci_ldisc.c
> >@@ -118,10 +118,6 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu)
> >
> >  int hci_uart_tx_wakeup(struct hci_uart *hu)
> >  {
> >-	struct tty_struct *tty = hu->tty;
> >-	struct hci_dev *hdev = hu->hdev;
> >-	struct sk_buff *skb;
> >-
> >  	if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) {
> >  		set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
> >  		return 0;
> >@@ -129,6 +125,18 @@ int hci_uart_tx_wakeup(struct hci_uart *hu)
> >
> >  	BT_DBG("");
> >
> >+	schedule_work(&hu->write_work);
> >+
> >+	return 0;
> >+}
> >+
> >+static void hci_uart_write_work(struct work_struct *work)
> >+{
> >+	struct hci_uart *hu = container_of(work, struct hci_uart, init_ready);
> >+	struct tty_struct *tty = hu->tty;
> >+	struct hci_dev *hdev = hu->hdev;
> >+	struct sk_buff *skb;
> >+
> 
> +	/* FIXME: if bad skb length or tty->ops->write() returns < 0 ??? */
> 
> >  restart:
> >  	clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
> >
> >@@ -153,7 +161,6 @@ restart:
> >  		goto restart;
> >
> >  	clear_bit(HCI_UART_SENDING, &hu->tx_state);
> >-	return 0;
> >  }
> >
> >  static void hci_uart_init_work(struct work_struct *work)
> >@@ -281,6 +288,7 @@ static int hci_uart_tty_open(struct tty_struct *tty)
> >  	tty->receive_room = 65536;
> >
> >  	INIT_WORK(&hu->init_ready, hci_uart_init_work);
> >+	INIT_WORK(&hu->write_work, hci_uart_write_work);
> >
> >  	spin_lock_init(&hu->rx_lock);
> >
> >@@ -318,6 +326,8 @@ static void hci_uart_tty_close(struct tty_struct *tty)
> >  	if (hdev)
> >  		hci_uart_close(hdev);
> >
> >+	cancel_work_sync(&hy->write_work);
> >+
> >  	if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) {
> >  		if (hdev) {
> >  			if (test_bit(HCI_UART_REGISTERED, &hu->flags))
> >diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
> >index fffa61f..12df101 100644
> >--- a/drivers/bluetooth/hci_uart.h
> >+++ b/drivers/bluetooth/hci_uart.h
> >@@ -68,6 +68,7 @@ struct hci_uart {
> >  	unsigned long		hdev_flags;
> >
> >  	struct work_struct	init_ready;
> >+	struct work_struct	write_work;
> >
> >  	struct hci_uart_proto	*proto;
> >  	void			*priv;
> >
>

Patch hide | download patch | download mbox

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 6e06f6f..ecdd765 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -118,10 +118,6 @@  static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu)
 
 int hci_uart_tx_wakeup(struct hci_uart *hu)
 {
-	struct tty_struct *tty = hu->tty;
-	struct hci_dev *hdev = hu->hdev;
-	struct sk_buff *skb;
-
 	if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) {
 		set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
 		return 0;
@@ -129,6 +125,18 @@  int hci_uart_tx_wakeup(struct hci_uart *hu)
 
 	BT_DBG("");
 
+	schedule_work(&hu->write_work);
+
+	return 0;
+}
+
+static void hci_uart_write_work(struct work_struct *work)
+{
+	struct hci_uart *hu = container_of(work, struct hci_uart, init_ready);
+	struct tty_struct *tty = hu->tty;
+	struct hci_dev *hdev = hu->hdev;
+	struct sk_buff *skb;
+
 restart:
 	clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
 
@@ -153,7 +161,6 @@  restart:
 		goto restart;
 
 	clear_bit(HCI_UART_SENDING, &hu->tx_state);
-	return 0;
 }
 
 static void hci_uart_init_work(struct work_struct *work)
@@ -281,6 +288,7 @@  static int hci_uart_tty_open(struct tty_struct *tty)
 	tty->receive_room = 65536;
 
 	INIT_WORK(&hu->init_ready, hci_uart_init_work);
+	INIT_WORK(&hu->write_work, hci_uart_write_work);
 
 	spin_lock_init(&hu->rx_lock);
 
@@ -318,6 +326,8 @@  static void hci_uart_tty_close(struct tty_struct *tty)
 	if (hdev)
 		hci_uart_close(hdev);
 
+	cancel_work_sync(&hy->write_work);
+
 	if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) {
 		if (hdev) {
 			if (test_bit(HCI_UART_REGISTERED, &hu->flags))
diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
index fffa61f..12df101 100644
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -68,6 +68,7 @@  struct hci_uart {
 	unsigned long		hdev_flags;
 
 	struct work_struct	init_ready;
+	struct work_struct	write_work;
 
 	struct hci_uart_proto	*proto;
 	void			*priv;