sparse context warning problem ...

[David Brownell <david-b@pacbell.net>]

I just noticed this with some obviously correct code... and verified
that it's a regression in current GIT version of "sparse" since it
now rejects code which previously passed just fine.

The issue is a not-uncommon idiom, where a function must be called
with a lock held, and briefly drops it.  The way this has previously
been addressed, originally suggested by Linus and used in various
places in the kernel (but, I observe, not in the "sparse" internal
validation test cases) is:

  static void
  finish_urb(struct ohci_hcd *ohci, struct urb *urb, int status)
  __releases(ohci->lock)
  __acquires(ohci->lock)
  {
	...
  }

But current versions of "sparse" complain (wrongly):

  drivers/usb/host/ohci-q.c:66:2: warning: context imbalance in 'finish_urb': __context__ statement expected different context
  drivers/usb/host/ohci-q.c:66:2:    context '<noident>': wanted >= 0, got -1

Presumably this is this a known bug ... is a fix on the way?
(Meanwhile, I can just ignore this bogus output.)

- Dave