wacom + runtime PM = AA deadlock

On Tue, Sep 14, 2010 at 08:07:39AM +0200, Oliver Neukum wrote:
> Am Dienstag, 14. September 2010, 02:52:10 schrieb Dmitry Torokhov:
> > On Mon, Sep 13, 2010 at 09:20:23PM +0200, Oliver Neukum wrote:
> > > Am Montag, 13. September 2010, 19:10:47 schrieb Dmitry Torokhov:
> > >
> > > > I think this introduces significant change in behavior though - before
> > > > we did not do usb_autopm_put_interface() on successful open, basically
> > > > disabling autopm facilities, right?
> > >
> > > Right. Which makes no sense at all. You'd better remove anything related
> > > to runtime PM and not set supports_autosuspend for that.
> > >
> >
> > That not what I meant, I do not want to remove autopm, it's just it was
> > effectively disabled and if we fix it we might start getting some
> > regression reports ;)
>
> True. So currently we have
>
> - a deadlock
> - disabled runtime power management
>
> We need to fix the deadlock. We can fix it retaining a disabled
> runtime power management. Or we can fix it fixing the runtime
> power management at the same time. However this opens
> the door to regressions. So for now I really suggest removing
> it from the driver and reintroduce it properly for the next merge
> window.
>

Lost track of this issue for a while. So I think we still need to fix
the deadlock for .36 and I think that the following will do that. Then
we'll adjust the driver to actually enable runtime PM for .37.

Thanks.
Acked-by: Oliver Neukum <oneukum@suse.de>

1 files changed, 12 insertions, 11 deletions

diff --git a/usr/src/dkms_source_tree/wacom_sys.c b/usr/src/dkms_source_tree/wacom_sys.c
index 1e3af29..02de653 100644
--- a/usr/src/dkms_source_tree/wacom_sys.c
+++ b/usr/src/dkms_source_tree/wacom_sys.c
@@ -103,27 +103,26 @@ static void wacom_sys_irq(struct urb *urb)
 static int wacom_open(struct input_dev *dev)
 {
         struct wacom *wacom = input_get_drvdata(dev);
+        int retval = 0;
 
-        mutex_lock(&wacom->lock);
-
-        wacom->irq->dev = wacom->usbdev;
-
-        if (usb_autopm_get_interface(wacom->intf) < 0) {
-                mutex_unlock(&wacom->lock);
+        if (usb_autopm_get_interface(wacom->intf) < 0)
                 return -EIO;
-        }
+
+        mutex_lock(&wacom->lock);
 
         if (usb_submit_urb(wacom->irq, GFP_KERNEL)) {
-                usb_autopm_put_interface(wacom->intf);
-                mutex_unlock(&wacom->lock);
-                return -EIO;
+                retval = -EIO;
+                goto out;
         }
 
         wacom->open = true;
         wacom->intf->needs_remote_wakeup = 1;
 
+out:
         mutex_unlock(&wacom->lock);
-        return 0;
+        if (retval)
+                usb_autopm_put_interface(wacom->intf);
+        return retval;
 }
 
 static void wacom_close(struct input_dev *dev)
@@ -135,6 +134,8 @@ static void wacom_close(struct input_dev *dev)
         wacom->open = false;
         wacom->intf->needs_remote_wakeup = 0;
         mutex_unlock(&wacom->lock);
+
+        usb_autopm_put_interface(wacom->intf);
 }
 
 static int wacom_parse_hid(struct usb_interface *intf, struct hid_descriptor *hid_desc,