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    Subject[PATCH 3.4 80/91] bluetooth: hci_ldisc: fix deadlock condition
    Date
    From: Felipe Balbi <balbi@ti.com>

    3.4.105-rc1 review patch. If anyone has any objections, please let me know.

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


    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>
    [tim.niemeyer@corscience.de: rebased on 3.4.103]
    Signed-off-by: Tim Niemeyer <tim.niemeyer@corscience.de>
    Signed-off-by: Zefan Li <lizefan@huawei.com>
    ---
    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;

    --
    1.9.1


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