[PATCH] bluetooth: hci_ldisc: fix deadlock condition

[PATCH] bluetooth: hci_ldisc: fix deadlock condition

[Tim Niemeyer]

This Patch was applied to 3.10 and 3.2. It's probably missed on 3.4.

---------------------

From: Felipe Balbi <balbi@ti.com>

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.

Acked-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Reported-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Tested-by: Andreas Bießmann <andreas@biessmann.de>
[tim.niemeyer@corscience.de: rebased on 3.4.103]
Signed-off-by: Tim Niemeyer <tim.niemeyer@corscience.de>
---
 drivers/bluetooth/hci_ldisc.c |   25 ++++++++++++++++++++-----
 drivers/bluetooth/hci_uart.h  |    2 ++
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 98a8c05..d4550f9 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 +125,22 @@ 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, write_work);
+	struct tty_struct *tty = hu->tty;
+	struct hci_dev *hdev = hu->hdev;
+	struct sk_buff *skb;
+
+	/* REVISIT: should we cope with bad skbs or ->write() returning
+	 * and error value ?
+	 */
+
 restart:
 	clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
 
@@ -153,7 +165,6 @@ restart:
 		goto restart;
 
 	clear_bit(HCI_UART_SENDING, &hu->tx_state);
-	return 0;
 }
 
 /* ------- Interface to HCI layer ------ */
@@ -264,6 +275,8 @@ static int hci_uart_tty_open(struct tty_struct *tty)
 	hu->tty = tty;
 	tty->receive_room = 65536;
 
+	INIT_WORK(&hu->write_work, hci_uart_write_work);
+
 	spin_lock_init(&hu->rx_lock);
 
 	/* Flush any pending characters in the driver and line discipline. */
@@ -298,6 +311,8 @@ static void hci_uart_tty_close(struct tty_struct *tty)
 		if (hdev)
 			hci_uart_close(hdev);
 
+		cancel_work_sync(&hu->write_work);
+
 		if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) {
 			if (hdev) {
 				hci_unregister_dev(hdev);
diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
index 6cf6ab22..af93d83 100644
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -66,6 +66,8 @@ struct hci_uart {
 	unsigned long		flags;
 	unsigned long		hdev_flags;
 
+	struct work_struct	write_work;
+
 	struct hci_uart_proto	*proto;
 	void			*priv;
 
-- 
1.7.10.4

Re: [PATCH] bluetooth: hci_ldisc: fix deadlock condition

[Greg KH]

On Fri, Aug 22, 2014 at 03:45:07PM +0200, Tim Niemeyer wrote:
> This Patch was applied to 3.10 and 3.2. It's probably missed on 3.4.

Does it apply there?

What is the git id of the commit?

thanks,

greg k-h

Re: [PATCH] bluetooth: hci_ldisc: fix deadlock condition

[Tim Niemeyer]

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Hi

Am Freitag, den 22.08.2014, 10:51 -0500 schrieb Greg KH:
> On Fri, Aug 22, 2014 at 03:45:07PM +0200, Tim Niemeyer wrote:
> > This Patch was applied to 3.10 and 3.2. It's probably missed on 3.4.
> 
> Does it apply there?
The original patch applies not cleanly on 3.4. The init_work is not
available there.

I backported it and it's the same result as the backport from Andreas.
He tested the patch on 3.4.87. The attached patch of my last mail
applies.

> What is the git id of the commit?
Sorry, missed it:

commit da64c27d3c93ee9f89956b9de86c4127eb244494 upstream
commit a22d29e6e5757b1daed7d0b409a815eb33f66e4e stable-3.10
commit 87520218746b8d973670e37237666f174590898c stable-3.2

Tim

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