linux-kernel - Re: WARNING at tty_buffer.c:428 process_one

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Date:	Tue, 05 Mar 2013 15:47:04 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	David Miller <davem@...emloft.net>
Cc:	jslaby@...e.cz, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: WARNING at tty_buffer.c:428 process_one_work()

On Tue, 2013-03-05 at 15:03 -0500, David Miller wrote:
> From: Jiri Slaby <jslaby@...e.cz>
> Date: Tue, 05 Mar 2013 20:44:49 +0100
> 
> > Hi, I must admit I don't understand. I now checked both of them and they
> > call uart_handle_sysrq_char unconditionally, or?
> 
> Nope, in the sunsab.c receive function, we used to handle the SYSRQ
> stuff before break checking when TTY is NULL, now we don't.

Hi David,

SysRq is signalled first by a BRK condition, then followed by the input
character indicating which SysRq function to perform.

sunsab.c: receive_char() is behaving as you would expect.

First, a BRK status is indicated so uart_handle_break() records a
timestamp. If the next input is received within 5 sec. of that
timestamp, the character received is interpreted as a SysRq function --
handled by uart_handle_sysrq_char().

Are you observing that SysRq processing is not occurring with this
driver when only a console exists, or are you hypothesizing that this is
possible?

Regards,
Peter Hurley

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