Re: [PATCH AUTOSEL 6.4 24/25] usb: cdc-acm: move ldisc dcd notification outside of acm's read lock

[Sasha Levin]

On Mon, Sep 11, 2023 at 11:19:13AM +0200, Johan Hovold wrote:
> On Fri, Sep 08, 2023 at 08:37:12PM -0400, Sasha Levin wrote:
> > From: Dan Drown <dan-netdev@xxxxxxxxx>
> >
> > [ Upstream commit f72ae60881ff685004d7de7152517607fcd9968f ]
> >
> > dcd_change notification call moved outside of the acm->read_lock
> > to protect any future tty ldisc that calls wait_serial_change()
> >
> > Signed-off-by: Dan Drown <dan-netdev@xxxxxxxxx>
> > Acked-by: Oliver Neukum <oneukum@xxxxxxxx>
> > Link: https://lore.kernel.org/r/ZN1zV/zjPgpGlHXo@xxxxxxxxxxxxxx
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> > ---
> >  drivers/usb/class/cdc-acm.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
> > index 11da5fb284d0a..ca51230f44409 100644
> > --- a/drivers/usb/class/cdc-acm.c
> > +++ b/drivers/usb/class/cdc-acm.c
> > @@ -318,6 +318,16 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf)
> >  		}
> >
> >  		difference = acm->ctrlin ^ newctrl;
> > +
> > +		if ((difference & USB_CDC_SERIAL_STATE_DCD) && acm->port.tty) {
> > +			struct tty_ldisc *ld = tty_ldisc_ref(acm->port.tty);
> > +			if (ld) {
> > +				if (ld->ops->dcd_change)
> > +					ld->ops->dcd_change(acm->port.tty, newctrl & USB_CDC_SERIAL_STATE_DCD);
> > +				tty_ldisc_deref(ld);
> > +			}
> > +		}
> > +
> >  		spin_lock_irqsave(&acm->read_lock, flags);
> >  		acm->ctrlin = newctrl;
> >  		acm->oldcount = acm->iocount;
>
> This is a fix for a commit in 6.6-rc1 (3b563b901eef ("usb: cdc-acm: add
> PPS support")) so a backport of it makes no sense.
>
> Please drop.

Done, thanks!

--
Thanks,
Sasha