Make sure calls to certain functions are matched by the relevant function at other end of the function, and also during ALL failure/early return paths.

Examples:

 * pci_alloc_consistent() and pci_free_consistent()
 * ioremap() must be balanced by an iounmap() (this causes a memory leak).
 * check for balanced *_lock_* and *_unlock_* along all paths in a function
  * (can cause dead-lock if not).
 * Make sure no-one is freeing skbs with kfree instead of kfree_skb
 * check that net_device interrupt functions use dev_kfree_skb_irq and not just dev_kfree_skb
 * Make sure reference counts are not leaked by accident. (forgetting to fput(), ...)