Re: [TTY] exclusive mode question

From: moreau francis
Date: Thu Jun 09 2005 - 07:19:03 EST



--- Frederik Deweerdt <dev.deweerdt@xxxxxxxxxxx> a écrit :

> Le 09/06/05 11:59 +0200, moreau francis écrivit:
> >
> > --- Frederik Deweerdt <dev.deweerdt@xxxxxxxxxxx> a écrit :
> >
> > > I've just greped and I found :
> > >
> > > if (!retval && test_bit(TTY_EXCLUSIVE, &tty->flags) &&
> > > !capable(CAP_SYS_ADMIN))
> > > retval = -EBUSY;
> > > in drivers/char/tty_io.c:tty_open
> > >
> > > Which sources are you looking at?
> > >
> >
> > same source code but if another process has previously open the tty, how
> does
> > this source code detect it ?
> >
> Sorry I misunderstood your question, there's no check on previous opens:
> from man tty_ioctl:
>
> TIOCEXCL void
> Put the tty into exclusive mode. No _further_ open(2)
> operations on the terminal are permitted.
> (They will fail with EBUSY, except for root.)
>

BTW, I don't see any use of this mode since it can't ensure that nothing is
using the tty...Do you know what kind of purpose it is for ?

Francis





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