[PATCH 3.2 002/125] bluetooth: hci_ldisc: fix deadlock condition

Ben Hutchings
2014-07-08T19:42:20Z

From: Felipe Balbi <balbi@ti.com>

commit da64c27d3c93ee9f89956b9de86c4127eb244494 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/bluetooth/hci_ldisc.c | 24 +++++++++++++++++++-----
drivers/bluetooth/hci_uart.h | 1 +
2 files changed, 20 insertions(+), 5 deletions(-)

--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -120,10 +120,6 @@ static inline struct sk_buff *hci_uart_d

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;
@@ -131,6 +127,22 @@ int hci_uart_tx_wakeup(struct hci_uart *

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);

@@ -155,7 +167,6 @@ restart:
goto restart;

clear_bit(HCI_UART_SENDING, &hu->tx_state);
- return 0;
}

/* ------- Interface to HCI layer ------ */
@@ -274,6 +285,8 @@ static int hci_uart_tty_open(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. */
@@ -308,6 +321,8 @@ static void hci_uart_tty_close(struct tt
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);
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -64,6 +64,8 @@ struct hci_uart {
unsigned long flags;
unsigned long hdev_flags;

+ struct work_struct write_work;
+
struct hci_uart_proto *proto;
void *priv;