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

From: Andy Lutomirski
Date: Wed Apr 08 2015 - 17:41:20 EST


On Wed, Apr 8, 2015 at 2:29 PM, Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> 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.

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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