| Message ID | 20100406114238.GN5594@kryten (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On (Tue) Apr 06 2010 [21:42:38], Anton Blanchard wrote: > > Hi, > > > > Looking at the commit e74d098c66543d0731de62eb747ccd5b636a6f4c, > > > i see that for every tty_kref_get() there is a corresponding > > > tty_kref_put() except maybe for the one in the following patch snippet > > > > > > spin_lock_irqsave(&hp->lock, flags); > > > /* Check and then increment for fast path open. */ > > > if (hp->count++ > 0) { > > > + tty_kref_get(tty); > > > spin_unlock_irqrestore(&hp->lock, flags); > > > hvc_kick(); > > > return 0; > > > > > > I don't know this code very well but we might be missing a > > > corresponding tty_kref_put() some place ? > > > > See hvc_hangup: > > > > temp_open_count = hp->count; > > ... > > while(temp_open_count) { > > --temp_open_count; > > tty_kref_put(tty); > > kref_put(&hp->kref, destroy_hvc_struct); > > } > > I don't claim to understand the tty layer, but it seems like hvc_open and > hvc_close should be balanced in their kref reference counting. > > Right now we get a kref every call to hvc_open: > > if (hp->count++ > 0) { > tty_kref_get(tty); <----- here > spin_unlock_irqrestore(&hp->lock, flags); > hvc_kick(); > return 0; > } /* else count == 0 */ > > tty->driver_data = hp; > > hp->tty = tty_kref_get(tty); <------ or here if hp->count was 0 > > But hvc_close has: > > tty_kref_get(tty); > > if (--hp->count == 0) { > ... > /* Put the ref obtained in hvc_open() */ > tty_kref_put(tty); > ... > } > > tty_kref_put(tty); > > Since the outside kref get/put balance we only do a single kref_put when > count reaches 0. OK, makes sense and since it works for you, Acked-by: Amit Shah <amit.shah@redhat.com> > The patch below changes things to call tty_kref_put once for every > hvc_close call, and with that my machine boots fine. > > Signed-off-by: Anton Blanchard <anton@samba.org>
Anton Blanchard wrote: > The patch below changes things to call tty_kref_put once for every > hvc_close call, and with that my machine boots fine. > > Signed-off-by: Anton Blanchard <anton@samba.org> > --- > Works for me. Thanks Anton. Regards -Sachin > diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c > index d3890e8..35cca4c 100644 > --- a/drivers/char/hvc_console.c > +++ b/drivers/char/hvc_console.c > @@ -368,16 +368,12 @@ static void hvc_close(struct tty_struct *tty, struct file * filp) > hp = tty->driver_data; > > spin_lock_irqsave(&hp->lock, flags); > - tty_kref_get(tty); > > if (--hp->count == 0) { > /* We are done with the tty pointer now. */ > hp->tty = NULL; > spin_unlock_irqrestore(&hp->lock, flags); > > - /* Put the ref obtained in hvc_open() */ > - tty_kref_put(tty); > - > if (hp->ops->notifier_del) > hp->ops->notifier_del(hp, hp->data); > > >
> I don't claim to understand the tty layer, but it seems like hvc_open and > hvc_close should be balanced in their kref reference counting. They should yes.
On Tue, 6 Apr 2010 09:12:38 pm Anton Blanchard wrote: > The patch below changes things to call tty_kref_put once for every > hvc_close call, and with that my machine boots fine. Thanks, applied. Cheers, Rusty.
diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c index d3890e8..35cca4c 100644 --- a/drivers/char/hvc_console.c +++ b/drivers/char/hvc_console.c @@ -368,16 +368,12 @@ static void hvc_close(struct tty_struct *tty, struct file * filp) hp = tty->driver_data; spin_lock_irqsave(&hp->lock, flags); - tty_kref_get(tty); if (--hp->count == 0) { /* We are done with the tty pointer now. */ hp->tty = NULL; spin_unlock_irqrestore(&hp->lock, flags); - /* Put the ref obtained in hvc_open() */ - tty_kref_put(tty); - if (hp->ops->notifier_del) hp->ops->notifier_del(hp, hp->data);