Several issues of varying importance came up while I was working on this.
(1) The locking in devices.c needs to be fixed. The USB subsystem rwsem should be held over a much larger part of the code. That should be pretty easy to do. I don't think it's necessary to use usb_get_dev or to lock usbdev->serialize, but someone should verify this.
I'm thinking the plan of record for this one is that dev->serialize should be held when accessing dev->children[] ... though that'll take a while to phase in.
(2) The exact relationships among usbdev->state, usbdev->actconfig, and the actual state of the physical device aren't clear. Various error scenarios can leave ->state disagreeing with the device or ->state equal to USB_STATE_CONFIGURED even though ->actconfig is NULL. This needs more thought.
Are you sure about CONFIGURED without an actconfig? It certainly doesn't need to be that way; the current 2.6.6 code doesn't have that problem, it updates state to ADDRESSED when clearing actconfig if the original state is CONFIGURED.
(3) I decided that it wasn't really necessary to make a deep copy of
the altsetting and endpoint structures for the dynamic interfaces (those
structures are read-only), so this patch just copies some pointers. Unfortunately this opens up a hole: A user program can pin an interface
attribute file and use it to try reading an altsetting structure even
after the device has been disconnected and the structure deallocated. I
added a test to the attribute read method to prevent dereferencing a NULL
pointer, but there remained the possibility of a race between using the
pointer and setting it to NULL. So I added another semaphore to handle
_that_. All this makes those attribute methods a lot bigger than they
used to be.
Seems like you resolved this to your satisfaction in as246c, using the kref instead.
Other than testing, and (1) above which is deeper khubd surgery, it looks like those issues are now gone. Any other issues?
I skimmed as246c and didn't notice any particular issues as I skimmed. There were a few whitespace changes bulking it up, but those weren't going to make trouble!
- Dave
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