linux-kernel - Re: console=ttyS1 breaks ttyS1 termios and prevents me from logging in

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Message-ID: <CALCETrX_ndZ6Df9D8fecK1QzWvJCJYNQFsTUhRVr5BzwRzkUrg@mail.gmail.com>
Date:	Wed, 8 Apr 2015 17:45:44 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-serial@...r.kernel.org, Jiri Slaby <jslaby@...e.cz>,
	"Theodore Ts'o" <tytso@....edu>
Subject: Re: console=ttyS1 breaks ttyS1 termios and prevents me from logging in

On Wed, Apr 8, 2015 at 4:32 PM, Peter Hurley <peter@...leysoftware.com> wrote:
> On 04/08/2015 05:40 PM, Andy Lutomirski wrote:
>> On Wed, Apr 8, 2015 at 2:29 PM, Peter Hurley <peter@...leysoftware.com> wrote:
>>> Hi Andy,
>>>
>>> On 04/08/2015 05:17 PM, Andy Lutomirski wrote:
>>>> Something strange seems to have happened to my serial console setup.
>>>> I boot with console=ttyS1,115200n8 and I have a getty running on
>>>> /dev/ttyS1.
>>>>
>>>> On older kernels, or if I remove the console= boot parameter, then my
>>>> getty works fine.  On 3.19.3 with the console= parameter, something's
>>>> wrong with termios and I can't log in.  Running:
>>>
>>> Thanks for the report.
>>> 1. Please attach your dmesg.
>>> 2. Is this behavior new to 3.19.3? (iow, what was the last version
>>>    that you noticed didn't do this)
>>
>> I didn't have the problem before I reinstalled this box, upgraded from
>> 3.15 to 3.19.3, and updated by Dell iDRAC7 firmware.  Booting into
>> 3.13-something does *not* fix the problem, so I'm not at all convinced
>> that the kernel version matters much.  I'll try reverting the iDRAC7
>> thing, but I don't see why that would make any difference at all to
>> Linux.
>
> I think this is related to DRAC; maybe upgrading the firmware reset
> the Serial communication settings in the system bios?
>

The DRAC pretends to be a 16550, so I don't understand how it could
prevent Linux from reprogramming the line discipline.  Also, if I
remove console=ttyS1,115200 from the kernel command line, it starts
working again.

> 1. What's your getty command line?

/sbin/getty -8 115200 ttyS1


> 2. Contents of /proc/tty/driver/serial when you think getty is running
>    and waiting for login (shows line signals).

With getty running:

serinfo:1.0 driver revision:
0: uart:16550A port:000003F8 irq:4 tx:0 rx:0
1: uart:16550A port:000002F8 irq:3 tx:19828 rx:2 RTS|CTS|DTR
2: uart:unknown port:000003E8 irq:4
3: uart:unknown port:000002E8 irq:3
4: uart:unknown port:00000000 irq:0

(getty itself works fine)

When I type a username, I get:

serinfo:1.0 driver revision:
0: uart:16550A port:000003F8 irq:4 tx:0 rx:0
1: uart:16550A port:000002F8 irq:3 tx:19848 rx:10 RTS|CTS|DTR
2: uart:unknown port:000003E8 irq:4
3: uart:unknown port:000002E8 irq:3
4: uart:unknown port:00000000 irq:0

at that point, login is running, and it's login that doesn't work.

>
> Something to test is if you set getty to local line, does it work then.
> I use agetty so my command line is:
>         /sbin/getty --noreset -8L 115200 ttyS0 vt102

I tried:

# /sbin/getty --noreset -8L 115200 ttyS1 vt102

it has exactly the same problem.

By adding a whole bunch of printks, I see that both ttyS0 and ttyS1
make it into uart_set_termios.  But now it's time to home...

--Andy

>
> Regards,
> Peter Hurley
>
>
>> dmesg attached.  I don't even know what to look for there, though.
>>
>>>
>>> Regards,
>>> Peter Hurley
>>>
>>>> # stty icanon </dev/ttyS1
>>>>
>>>> breaks line this (partial strace results included):
>>>>
>>>> ioctl(0, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or
>>>> TCGETS, {B115200 opost -isig -icanon -echo ...}) = 0
>>>> ioctl(0, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or
>>>> TCGETS, {B115200 opost -isig -icanon -echo ...}) = 0
>>>> ioctl(0, SNDCTL_TMR_STOP or SNDRV_TIMER_IOCTL_GINFO or TCSETSW,
>>>> {B115200 opost -isig icanon -echo ...}) = 0
>>>> ioctl(0, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or
>>>> TCGETS, {B115200 opost -isig -icanon -echo ...}) = 0
>>>> ioctl(0, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or
>>>> TCGETS, {B115200 opost -isig -icanon -echo ...}) = 0
>>>> write(2, "stty: ", 6stty: )                   = 6
>>>> write(2, "standard input: unable to perfor"..., 58standard input:
>>>> unable to perform all requested operations) = 58
>>>>
>>>> IOW, the setting didn't stick.  On the bad kernel, stty works just
>>>> fine on ttyS0.  If I switch to using console=ttyS0,115200, then stty
>>>> works on ttyS1 and fails on ttyS0.
>>>>
>>>> I have no idea what's going on here.  I have two apparently identical
>>>> boxes.  One of them has this problem and the other doesn't.
>>>
>>
>>
>>
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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