linux-kernel - Re: [PATCH v2 1/6] TTY: serial, remove BTM from wait_until

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Date:	Wed, 10 Aug 2011 20:10:32 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Jiri Slaby <jslaby@...e.cz>, gregkh@...e.de,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alan Cox <alan@...ux.intel.com>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 1/6] TTY: serial, remove BTM from wait_until_sent

On 08/10/2011 08:07 PM, Andreas Bombe wrote:
> On Wed, Aug 10, 2011 at 04:43:19PM +0200, Jiri Slaby wrote:
>> On 08/10/2011 03:09 AM, Andreas Bombe wrote:
>>> I did my simple test on ttyS0 again: "stty -F /dev/ttyS0 crtscts" then
>>> "echo >/dev/ttyS0". I attached the gzipped sysrq-t list in case you need
>>> the complete output. This is just the process while it is trying to
>>> close the device (bash's internal echo):
>>
>> Hmm, perhaps obvious question. What is the port connected with? And with
>> what cable? Is it null modem cable? Or at least with DTR-CTS connected?
> 
> Nothing is connected. After all, the whole point of this exercise is to
> give the driver data to send which it can't get out so I can see whether
> it blocks all tty operations system wide while trying to do the flush on
> close.

But according to the trace, it waits only in its queue...

Well, could you turn on lockdep and dump sysrq-d when your echo is
closing the port?

thanks,
-- 
js
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