From b58af4066d240b18b43f202e07b9ec7461d90b17 Mon Sep 17 00:00:00 2001
From: Johan Hovold <jhovold@gmail.com>
Date: Wed, 4 Aug 2010 15:45:57 +0200
Subject: [PATCH] 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: 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>
---
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