USB: serial: keyspan_pda: fix write deadlock

The write() callback can be called in interrupt context (e.g. when used
as a console) so interrupts must be disabled while holding the port lock
to prevent a possible deadlock.

Fixes: e81ee637e4ae ("usb-serial: possible irq lock inversion (PPP vs. usb/serial)")
Fixes: 507ca9bc0476 ("[PATCH] USB: add ability for usb-serial drivers to determine if their write urb is currently being used.")
Cc: stable <stable@vger.kernel.org>     # 2.6.19
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c
index 2d5ad579475a8417c09ce1218ba73b6f77c0b2ee..17b60e5a9f1fe453c5e908b3663bd308df06d4d3 100644 (file)
--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -443,6 +443,7 @@ static int keyspan_pda_write(struct tty_struct *tty,
        int request_unthrottle = 0;
        int rc = 0;
        struct keyspan_pda_private *priv;
+       unsigned long flags;
 
        priv = usb_get_serial_port_data(port);
        /* guess how much room is left in the device's ring buffer, and if we
@@ -462,13 +463,13 @@ static int keyspan_pda_write(struct tty_struct *tty,
           the TX urb is in-flight (wait until it completes)
           the device is full (wait until it says there is room)
        */
-       spin_lock_bh(&port->lock);
+       spin_lock_irqsave(&port->lock, flags);
        if (!test_bit(0, &port->write_urbs_free) || priv->tx_throttled) {
-               spin_unlock_bh(&port->lock);
+               spin_unlock_irqrestore(&port->lock, flags);
                return 0;
        }
        clear_bit(0, &port->write_urbs_free);
-       spin_unlock_bh(&port->lock);
+       spin_unlock_irqrestore(&port->lock, flags);
 
        /* At this point the URB is in our control, nobody else can submit it
           again (the only sudden transition was the one from EINPROGRESS to