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Date:      Sun, 20 Apr 2014 18:35:13 -0600
From:      Ian Lepore <ian@FreeBSD.org>
To:        Tim Kientzle <kientzle@FreeBSD.org>
Cc:        FreeBSD ARM <freebsd-arm@FreeBSD.org>
Subject:   Re: Curious BeagleBone console hang...
Message-ID:  <1398040513.1124.369.camel@revolution.hippie.lan>
In-Reply-To: <723E6F77-A274-4115-8D37-C12353494EA1@freebsd.org>
References:  <723E6F77-A274-4115-8D37-C12353494EA1@freebsd.org>

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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.

-- Ian





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