Messages in this thread | | | Date | Mon, 12 Mar 2012 11:26:01 +0100 | From | Richard Weinberger <> | Subject | Re: TTY: tty_port questions |
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On 11.03.2012 12:01, Richard Weinberger wrote: > Am 11.03.2012 00:21, schrieb Richard Weinberger: >> Am 10.03.2012 23:51, schrieb Jiri Slaby: >>> On 03/10/2012 11:26 PM, Richard Weinberger wrote: >>>> Hi! >>> >>>> While moving UML's console driver to tty_port some strange things >>>> happened. So, I have a few questions. :-) >>> >>>> The original driver did not implement tty_operations->hangup(). If >>>> I implement it and call tty_port_hangup(), as Alan suggested, the >>>> login fails on all TTYs except tty0. It fails because the opened >>>> TTY returns EIO upon read()/write() after /bin/login called >>>> vhangup(). >>> >>>> The call chain is: vhangup() -> tty_vhangup_self() -> tty_vhangup() >>>> -> __tty_hangup() >>> >>>> Within __tty_hangup() something happens that I don't fully >>>> understand: >>> >>>> if (cons_filp) { if (tty->ops->close) for (n = 0; n< closecount; >>>> n++) tty->ops->close(tty, cons_filp); } else if (tty->ops->hangup) >>>> (tty->ops->hangup)(tty); >>> >>>> Login on tty0 works because cons_filp is not NULL and >>>> tty->ops->close() is called. On the other hand login fails on every >>>> other TTY because cons_filp remains NULL and the TTY hangs up. >>> >>>> Is there something missing in my hangup function? >>> >>>> If I omit tty_operations->hangup() and leave it, like the old >>>> driver, NULL non-tty0 TTYs cannot be opened. (getty terminates >>>> immediately because it cannot open any TTY.) open() retuns -EIO >>>> because the TTY_CLOSING is set in tty->flags. >>> >>>> How can this be? >>> >>> Hmm, it looks like some process is sitting on a TTY which was hung. >>> And the system offers this hung TTY to others on further opens. Could >>> you check that there is no process with open TTY after the vhangup? >>> >> >> "lsof | grep tty" does not show anything else than tty0. :-\ >> > > BTW: When I start the kernel with /bin/sh as init, opening and writing to any TTY works fine. > It looks like Fedora 16's userspace does something that makes the TTYs unhappy. > > Thanks, > //richard
Another question, what is the purpose of tty_port->console? It seems to have no user.
Is tty_port really the right thing for a console driver like in the UML case?
Thanks, //richard
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