• Dean Jenkins's avatar
    Bluetooth: hci_ldisc: Add protocol check to hci_uart_tx_wakeup() · 2d6f1da1
    Dean Jenkins authored
    Before attempting to schedule a work-item onto hu->write_work in
    hci_uart_tx_wakeup(), check that the Data Link protocol layer is
    still bound to the HCI UART driver.
    
    Failure to perform this protocol check causes a race condition between
    the work queue hu->write_work running hci_uart_write_work() and the
    Data Link protocol layer being unbound (closed) in hci_uart_tty_close().
    
    Note hci_uart_tty_close() does have a "cancel_work_sync(&hu->write_work)"
    but it is ineffective because it cannot prevent work-items being added
    to hu->write_work after cancel_work_sync() has run.
    
    Therefore, add a check for HCI_UART_PROTO_READY into hci_uart_tx_wakeup()
    which prevents scheduling of the work queue when HCI_UART_PROTO_READY
    is in the clear state. However, note a small race condition remains
    because the hci_uart_tx_wakeup() thread can run in parallel with the
    hci_uart_tty_close() thread so it is possible that a schedule of
    hu->write_work can occur when HCI_UART_PROTO_READY is cleared. A complete
    solution needs locking of the threads which is implemented in a future
    commit.
    Signed-off-by: default avatarDean Jenkins <Dean_Jenkins@mentor.com>
    Signed-off-by: default avatarMarcel Holtmann <marcel@holtmann.org>
    2d6f1da1
hci_ldisc.c 18.8 KB