linux-kernel - Re: [PATCH tty-next 7/7] n_tty: trace input/read flow control

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Message-ID: <52949B73.3000206@hurleysoftware.com>
Date:	Tue, 26 Nov 2013 08:00:35 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Jiri Slaby <jslaby@...e.cz>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH tty-next 7/7] n_tty: trace input/read flow control

On 11/23/2013 09:38 PM, Peter Hurley wrote:
> On 11/23/2013 07:25 PM, One Thousand Gnomes wrote:
>> On Fri, 22 Nov 2013 10:59:25 -0500
>> Peter Hurley <peter@...leysoftware.com> wrote:
>>
>>> Instrument .receive_buf() and read() paths with trace_printk's
>>> to aid in debugging flow control changes.
>>
>> tty devices have a device, we have a dev_dbg() layer. The old tty trace
>> predates this but there isn't really any excuse for not using it now that
>> I can see ?
>
> I was using the ftrace facility because it has significantly less performance
> impact than printk (which was an important factor while debugging flow control
> problems).
>
> That said, I could further macro-ize n_tty_trace() with selectable facility
> (which would be useful when debugging problems that end in cpu death).

Greg,

I don't really mind if you don't want to take this patch; it is useful but
it does clutter up the code.

Regards,
Peter Hurley
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