Re: Slow mobile broadband detection

2011/6/14  <perazim portugalmail pt>:
> I had a similar problem several weeks ago and it turned out all I had to do
> was
> upgrade the kernel. Below is the reply from the list to resolve my problem.

$ uname -a
Linux tk 2.6.38-8-generic #42-Ubuntu SMP Mon Apr 11 03:31:24 UTC 2011
x86_64 x86_64 x86_64 GNU/Linux

Hi Perazim, probably the issue doesn't depend on a kernel bug - at
least not the one Dan provided the fix for, as 2.6.38 should have the
patch applied  now.

> Perazim
> On Thu, 2011-05-12 at 21:29 +0100, perazim portugalmail pt wrote:
>> Dan,
>> Attached are the messages log and the modem-manager log for the Alcatel
>> X220.
>> Let me know if you need any other info or to test anything.
> These logs indicate a kernel bug, with a 30 second hang when closing a
> serial port.  I submitted a patch to the kernel to fix this issue which
> was accepted for the 2.6.37 kernel:
> commit 02303f73373aa1da19dbec510ec5a4e2576f9610
> Author: Dan Williams <dcbw redhat com>
> Date:   Fri Nov 19 16:04:00 2010 -0600
>    usb-wwan: implement TIOCGSERIAL and TIOCSSERIAL to avoid blocking
> close(2)
>    Some devices (ex ZTE 2726) simply don't respond at all when data is sent
>    to some of their USB interfaces.  The data gets stuck in the TTYs queue
>    and sits there until close(2), which them blocks because closing_wait
>    defaults to 30 seconds (even though the fd is O_NONBLOCK).  This is
>    rarely desired.  Implement the standard mechanism to adjust closing_wait
>    and let applications handle it how they want to.
>    Signed-off-by: Dan Williams <dcbw redhat com>
> and the ModemManager snapshot you have should have the support necessary
> here.  What kernel version are you running?
> Dan
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