bluetooth: hci_ldisc: fix deadlock condition

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>

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 8f3d6db..08bbc48 100644 (file)
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -120,10 +120,6 @@ 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;
@@ -131,6 +127,22 @@ 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);
 
@@ -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_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 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 99fb352..ff40400 100644 (file)
--- 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;