On 10/01/2015 12:56 PM, Jean-Christian de Rivaz wrote: > 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
The crash reported here appears to be related to how mkiss handles its netdev; maybe prematurely freeing the tx/rx buffers? I'd relook at how slip handles netdev teardown. I don't see a problem with the ACM tty/tty core side of this. At the time the hangup occurs, there is actually still an ACM tty device. The line discipline is reinited as a security precaution to prevent a previous session's data from being visible in the new session. The tty core does not know at the time the vhangup() occurs that the ACM driver plans to unregister the tty device. Don't do any of the things you suggest above. Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
