On Wed, May 23, 2012 at 07:12:39AM +0200, Jan Safrata wrote:
> On 16:06 Tue 22 May , Johan Hovold wrote:
> > On Tue, May 22, 2012 at 02:04:37PM +0200, Jan Safrata wrote:
> > > Call Trace:
> > > [<f85e7c60>] usb_wwan_dtr_rts+0x60/0xa0 [usb_wwan]
> >
> > This is not right. You're fixing a race with disconnect in option's
> > probe, but this indicates that there's a race with usb_wwan_dtr_rts (as
> > well).
>
> > > @@ -1478,10 +1478,14 @@ static int option_send_setup(struct usb_serial_port *port)
> > > struct usb_wwan_intf_private *intfdata =
> > > (struct usb_wwan_intf_private *) serial->private;
> > > struct usb_wwan_port_private *portdata;
> > > - int ifNum = serial->interface->cur_altsetting->desc.bInterfaceNumber;
> > > + int ifNum;
> > > int val = 0;
> > > dbg("%s", __func__);
> > >
> > > + if (serial->disconnected)
> > > + return -ENODEV;
> > > +
> > > + ifNum = serial->interface->cur_altsetting->desc.bInterfaceNumber;
> > > if (is_blacklisted(ifNum, OPTION_BLACKLIST_SENDSETUP,
> > > (struct option_blacklist_info *) intfdata->private)) {
> > > dbg("No send_setup on blacklisted interface #%d\n", ifNum);
> >
> > This is not quite right. You need to use the disconnect mutex as well,
> > e.g.:
> >
> > mutex_lock(&serial->disc_mutex);
> > if (serial->disconnected) {
> > mutex_unlock(&serial->disc_mutex);
> > return -ENODEV;
> > }
> > ifNum = serial->interface->cur_altsetting->desc.bInterfaceNumber;
> > ...
> > ret = usb_control_msg(serial->dev, ...)
> > mutex_unlock(&serial->disc_mutex);
> >
> > return ret;
> >
> > Johan
>
> The mutex cannot be used in the option_send_setup() function, because it
> is already held in usb_wwan_dtr_rts() which calls the option_send_setup(),
> so simple check of serial->disconnected flag should be ok there.
Ah. I misread option_probe (only sets the send_setup pointer).
Hmmm. And you can't push the locking down into send_setup because it's
also called from open (which is also called with disc_mutex held)...
What about the other call sites in usb_wwan (in set_termios and tiocmset)?
Shouldn't these be protected by the disc_mutex as well? And wouldn't it
then be cleaner to check the disconnected flag where the lock is taken
(i.e., in usb_wwan)?
Johan
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