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From: Andy Lutomirski <luto@amacapital.net>
Date: Wed, 8 Apr 2015 14:17:35 -0700
Message-ID: <CALCETrVHeApB0_GxMkc88Giq6vLMpOz+wdZLmwhK7Ytumh2y6g@mail.gmail.com>
Subject: console=ttyS1 breaks ttyS1 termios and prevents me from logging in
To: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-serial@vger.kernel.org, Jiri Slaby <jslaby@suse.cz>,
        "Theodore Ts'o" <tytso@mit.edu>
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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:

# 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.

Thanks,
Andy
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