Force mkiss to reset the line discipline when serial device is removed

From	Jean-Christian de Rivaz <jc@eclis.ch>
Newsgroups	linux.kernel
Subject	Force mkiss to reset the line discipline when serial device is removed
Date	2015-10-01 19:30 +0200
Message-ID	<qePQ6-2MU-3@gated-at.bofh.it> (permalink)
References	<qePQ6-2MU-5@gated-at.bofh.it> <qePQ6-2MU-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi Greg and Jiri,

I try to fix a kernel panic bug related to the AX25 (and probably SLIP) 
line discipline when the corresponding serial device is removed [1]. I 
proposed some patches [2] [3] on the linux-hams mailing list but I think 
there raise more questions about how tty_ldisc_hangup() should work when 
a serial device is removed [4].

I actually see the following options:

a) Let the specific line discipline set the TTY_DRIVER_RESET_TERMIOS 
flag in tty->driver as in [2] but this is suspected bad practice [5].

b) Let the specific line discipline set the TTY_OTHER_CLOSED flag in tty 
and check it in tty_ldisc_hangup() as in [3].

c) Let the specific line discipline set the TTY_LDISC_HALTED flag in tty 
and check it in tty_ldisc_hangup().

d) Let the specific line discipline set a new flag for that purpose, for 
example TTY_LDISC_RESET, and check it in tty_ldisc_hangup().

e) Close the tty earlier so that tty_ldisc_reinit() is not even called. 
Need some advise on how this should be done.

f) That's all wrong, something other need to be changed.

I would appreciate some comments from tty subsystem experts about this 
issue.

[1] http://www.spinics.net/lists/linux-hams/msg03500.html
[2] http://www.spinics.net/lists/linux-hams/msg03511.html
[3] http://www.spinics.net/lists/linux-hams/msg03513.html
[4] http://www.spinics.net/lists/linux-hams/msg03509.html
[5] http://www.spinics.net/lists/linux-hams/msg03512.html

Best Regards,
Jean-Christian de Rivaz

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Force mkiss to reset the line discipline when serial device is removed Jean-Christian de Rivaz <jc@eclis.ch> - 2015-10-01 19:30 +0200
  Re: Force mkiss to reset the line discipline when serial device is  removed Peter Hurley <peter@hurleysoftware.com> - 2015-10-02 01:00 +0200
    Re: Force mkiss to reset the line discipline when serial device is  removed Jean-Christian de Rivaz <jc@eclis.ch> - 2015-10-02 10:40 +0200
      Re: Force mkiss to reset the line discipline when serial device is removed Thomas Osterried <thomas@osterried.de> - 2015-10-02 12:50 +0200
        Re: Force mkiss to reset the line discipline when serial device is  removed Jean-Christian de Rivaz <jc@eclis.ch> - 2015-10-02 15:50 +0200
          Re: Force mkiss to reset the line discipline when serial device is  removed Jean-Christian de Rivaz <jc@eclis.ch> - 2015-10-02 19:30 +0200
            [PATCH 1/1] Add poll method to mkiss let notify hangup to the user process. Jean-Christian de Rivaz <jc@eclis.ch> - 2015-10-02 23:50 +0200

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