Date: Sun, 20 Apr 2014 18:06:19 -0700 From: Tim Kientzle <kientzle@freebsd.org> To: Ian Lepore <ian@freebsd.org> Cc: FreeBSD ARM <freebsd-arm@freebsd.org> Subject: Re: Curious BeagleBone console hang... Message-ID: <F1C42638-06F1-4176-98AB-A104434760F5@freebsd.org> In-Reply-To: <1398040513.1124.369.camel@revolution.hippie.lan> References: <723E6F77-A274-4115-8D37-C12353494EA1@freebsd.org> <1398040513.1124.369.camel@revolution.hippie.lan>
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On Apr 20, 2014, at 5:35 PM, Ian Lepore <ian@FreeBSD.org> wrote:
> On Sun, 2014-04-20 at 16:37 -0700, Tim Kientzle wrote:
>> Here's an odd one:
>>
>> $ stty 72
>>
>> consistently hangs the serial console on a BeagleBone
>> running FreeBSD-CURRENT r264208. (I found this out
>> by accidentally omitting 'rows' when I typed the command.)
>>
>> Doesn't seem to affect an SSH session, only the serial console.
>>
>> After doing this, nothing seems to be running; the console
>> is just completely non responsive: even echo is dead.
>>
>> I can recover by logging in through SSH and killing the
>> console login.
>>
>> Trying to puzzle it out:
>>
>> $ truss stty 72
>> ...
>> ioctl(0,TIOCGETA,0xbffffcb0) = 0 (0x0)
>> ioctl(0,TIOCGETD,0xbffffc9c) = 0 (0x0)
>> ioctl(0,TIOCGWINSZ,0xbffffcdc) = 0 (0x0)
>> ioctl(1,TIOCGETA,0xbffffb60) = 0 (0x0)
>> ioctl(2,TIOCGETA,0xbffffb60) = 0 (0x0)
>> fstat(1,{ mode=crw------- ,inode=32,size=0,blksize=4096 }) = 0 (0x0)
>> fstat(2,{ mode=crw------- ,inode=32,size=0,blksize=4096 }) = 0 (0x0
>>
>>
>> Does this make sense to anyone?
>>
>> Tim
>
> You're setting the line speed to 72 baud, and due to recent kernel
> changes the console baud rate is allowed to be changed now, so you lose
> console comms as soon as the change takes effect.
Thank you!
I went through the stty man page several times
and consistently overlooked the description for
a bare number.
That makes perfect sense.
I guess getty must reset the line when the
login session exits, which would explain why
killing the login session recovers it.
Tim
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