Re: [PATCHv5 05/17] tty: don't allow ldisc dcd_change() after ldischalt

[Alexander Gordeev]

Ð Wed, 24 Nov 2010 22:36:00 +0000
Alan Cox <alan@xxxxxxxxxxxxxxx> ÐÐÑÐÑ:

> > Yes, indeed, it's a bug. Please consider the following example:
> > 
> >      CPU1                                      CPU2
> > =========================================================
> > uart_handle_dcd_change() {		tty_set_ldisc() {
> >   ld = tty_ldisc_ref(...)			  ...
> 
> [We have a reference]
> >   ...					  tty_ldisc_halt(...)
> 					  [Should block]
> 
> > I think tty code is exactly the right place to fix this bug; this is
> > what my patch is for.
> 
> More special case magic on top of the current crap isn't the right fix
> here, tty_ldisc_halt needs to wait for the references to hit zero.

Didn't know that current design is crap. :)
Ok, I think I'll add a new waitqueue and a new bit (TTY_LDISC_NOREF)
that halt will wait for. Is it good?

-- 
  Alexander

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