Re: Bug: ZSH crashes upon receiving SIGINT

[John <da_audiophile@yahoo.com>]

----- Original Message -----
> 
> From the report below it's obviously something more specific than this
> that's happening.
> 
>>  How to trigger the bug:
>>  1) Mount an Arch partition and install 'zsh' within it
>>  2) Execute the chroot command from another Arch env: arch-chroot
>>  /mnt/mini /bin/zsh
>>  3) Hit ctrl+c in the chroot
> 
> I'm afraid the fact this description appears to be specific to that
> distro and it looks like a lot of setting up of the chroot partition is
> presupposed, so it's unlikely anyone on this list who can actually help
> debug this is going to be able to reproduce it in this form.
> Nonetheless, it does look like we have enough information at least to
> start making suggestions, so if you're able to do a bit of further
> prodding it's not hopeless...
> 

Firstly, thank you for your thoughtful reply.

Yes, I didn't think I would be fortunate enough to have one of you guys running Arch Linux.  If you have a spare partition free, you can just boot from the live CD (www.archlinux.org) and execute a few commands to have an Arch partition only for the purpose of seeing this bug/troubleshooting.  If this is acceptable to you, I am glad to distill down exactly what you would type to do this.  Please let me know.

>>  # arch-chroot /mnt/mini /bin/zsh
>> 
>>  #
>>  <<hit ctrl-c>>
>>  # umount: /mnt/mini/dev/pts: target is busy
>>  (In some cases useful info about processes that
>>  use the device is found by lsof(8) or fuser(1).)
>>  umount: /mnt/mini/dev: target is busy
>>  (In some cases useful info about processes that
>>  use the device is found by lsof(8) or fuser(1).)
>>  %
>>  zsh: error on TTY read: Input/output error
> 
> Is that ^C happening at the command line, i.e. when no other
> programme than the shell is running?  That's how I read the above, but
> it would be good to be explicit.

Yes, that is correct.  Upon running the first line (arch-chroot ...) the chroot binary is called and the next prompt is INSIDE the partition target (/mnt/mini in my example).  You can run commands inside the chroot just fine, but it breaks if you hit ctrl+c as I have denoted with the <<hit ctrl-c>> which probably wasn't very obvious without this explanation.

> In that case, what does the umount stuff mean?  That's certainly got
> nothing to do with the shell's internal response to a Ctrl-C.

The umount and subsequent lines are all thrown when you hit ctrl+c.

> The error at the end comes from a specific point in the shell line
> editor: if it finds it can't read from the TTY, and the error isn't one
> of the small number it thinks are recoverable, it will exit.  In this
> case the error appears to be EIO.  So this certainly ties in with the
> behaviour you're seeing.
> 
> The question is where this error is coming from and it looks pretty
> likely it's somehow associated with that "umount 
> /mnt/mini/dev/pts" as
> that looks like an attempt to remove the devices providing the ttys (I'm
> guessing as is this is system stuff I don't know about).  The unmount
> may have failed but may also have left the tty in a bad state.  I think
> we need to know what's going on here.

I agree with you.  Most of the arch-chroot script is over my head.  I have linked it here if the code within is meaningful and if you have the time to read through it.  It is only 309 lines: http://pastebin.com/yDyuqxqi

<snip>

I'm afraid the comments from Dave in the Arch Linux bug report (https://bugs.archlinux.org/task/44073) are all I have to go on as to root cause.  I am happy to try to troubleshoot if you do not want to try to make a simple Arch partition on your system and try yourself from the live CD.  Please let me know and thanks again.