USB: serial: fix stalled writes (b58af406) · Commits · 戴 / test

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:

David VomLehn <dvomlehn@cisco.com> Tested-by:

David VomLehn <dvomlehn@cisco.com> Signed-off-by:

Johan Hovold <jhovold@gmail.com> Cc: stable <stable@kernel.org> Signed-off-by:

Greg Kroah-Hartman <gregkh@suse.de>

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). */

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