On Wed, 22 Aug 2012, Michael Grzeschik wrote:
> On Thu, Jul 19, 2012 at 12:20:11AM +0200, Michael Grzeschik wrote:
> > The lockdep hunter mentions a non consistent usage of spin_lock and
> > spin_lock_irqsafe in the composite_disconnect and usb_function_activate
> > function:
> >
> > [ 15.700897] =================================
> > [ 15.705255] [ INFO: inconsistent lock state ]
> > [ 15.709617] 3.5.0-rc5+ #413 Not tainted
> > [ 15.713453] ---------------------------------
> > [ 15.717812] inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
> > [ 15.723822] uvc-gadget/116 [HC1[1]:SC0[0]:HE0:SE1] takes:
> > [ 15.729222] (&(&cdev->lock)->rlock){?.+...}, at: [<7f0049e8>]
> > composite_disconnect+0x2c/0x74 [g_webcam]
> > [ 15.738797] {HARDIRQ-ON-W} state was registered at:
> > [ 15.743677] [<8006de3c>] mark_lock+0x148/0x688
> > [ 15.748325] [<8006ecb0>] __lock_acquire+0x934/0x1b74
> > [ 15.753481] [<8007047c>] lock_acquire+0x98/0x138
> > [ 15.758288] [<804c776c>] _raw_spin_lock+0x4c/0x84
> > [ 15.763188] [<7f006ae4>] usb_function_activate+0x28/0x94 [g_webcam]
> > [ 15.769652] [<7f00820c>] usb_ep_autoconfig_reset+0x78/0x98 [g_webcam]
> > [ 15.776287] [<7f0082a4>] uvc_v4l2_open+0x78/0x94 [g_webcam]
> > --- a/drivers/usb/gadget/composite.c
> > +++ b/drivers/usb/gadget/composite.c
> > @@ -300,9 +300,10 @@ int usb_function_deactivate(struct usb_function
> > *function)
> > int usb_function_activate(struct usb_function *function)
> > {
> > struct usb_composite_dev *cdev = function->config->cdev;
> > + unsigned long flags;
> > int status = 0;
> >
> > - spin_lock(&cdev->lock);
> > + spin_lock_irqsave(&cdev->lock, flags);
> >
> > if (WARN_ON(cdev->deactivations == 0))
> > status = -EINVAL;
> > @@ -312,7 +313,7 @@ int usb_function_activate(struct usb_function *function)
> > status = usb_gadget_connect(cdev->gadget);
> > }
> >
> > - spin_unlock(&cdev->lock);
> > + spin_unlock_irqrestore(&cdev->lock, flags);
> > return status;
> > }
Wouldn't it be better to fix the uvc-gadget driver to avoid calling
these functions in interrupt context? Or have I misunderstood the flow
of control?
Alan Stern
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