From: Robert Baldyga
> usb_gadget_disconnect() shouldn't be called under spinlock to avoid
> spinlock recursion. Function usb_gadget_disconnect() calls pullup(),
> which is callback from UDC driver, usually calling composite_disconnect().
> This function wants to lock spinlock used in usb_function_deactivate()
> causing spinlock recursion.
...
> +++ b/drivers/usb/gadget/composite.c
> @@ -260,8 +260,11 @@ int usb_function_deactivate(struct usb_function
> *function)
>
> spin_lock_irqsave(&cdev->lock, flags);
>
> - if (cdev->deactivations == 0)
> + if (cdev->deactivations == 0) {
> + spin_unlock_irqrestore(&cdev->lock, flags);
> status = usb_gadget_disconnect(cdev->gadget);
> + spin_lock_irqsave(&cdev->lock, flags);
> + }
> if (status == 0)
> cdev->deactivations++;
That sort of change rings big alarm bells.
You've effectively isolated the usb_gadget_disconnect() call
from the check that cdev->deactivations == 0.
And then you increment cdev->deactivations below.
Looks like it will be racy to me.
David
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