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Commit b58af406 authored by Johan Hovold's avatar Johan Hovold Committed by Greg Kroah-Hartman
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USB: serial: fix stalled writes 



As David VomLehn points out, it was possible to receive an interrupt
before clearing the free-urb flag which could lead to the urb being
incorrectly marked as busy.

For the same reason, move tx_bytes accounting so that it will never be
negative.

Note that the free-flags set and clear operations do not need any
additional locking as they are manipulated while USB_SERIAL_WRITE_BUSY
is set.

Reported-by: default avatarDavid VomLehn <dvomlehn@cisco.com>
Tested-by: default avatarDavid VomLehn <dvomlehn@cisco.com>
Signed-off-by: default avatarJohan Hovold <jhovold@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent b409214c

drivers/usb/serial/generic.c

+10 −5
Original line number Diff line number Diff line
@@ -208,18 +208,23 @@ retry: 
	urb->transfer_buffer_length = count;

	usb_serial_debug_data(debug, &port->dev, __func__, count,

						urb->transfer_buffer);

	spin_lock_irqsave(&port->lock, flags);

	port->tx_bytes += count;

	spin_unlock_irqrestore(&port->lock, flags);



	clear_bit(i, &port->write_urbs_free);

	result = usb_submit_urb(urb, GFP_ATOMIC);

	if (result) {

		dev_err(&port->dev, "%s - error submitting urb: %d\n",

						__func__, result);

		set_bit(i, &port->write_urbs_free);

		spin_lock_irqsave(&port->lock, flags);

		port->tx_bytes -= count;

		spin_unlock_irqrestore(&port->lock, flags);



		clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags);

		return result;

	}

	clear_bit(i, &port->write_urbs_free);



	spin_lock_irqsave(&port->lock, flags);

	port->tx_bytes += count;

	spin_unlock_irqrestore(&port->lock, flags);



	/* Try sending off another urb, unless in irq context (in which case

	 * there will be no free urb). */