sched: replace INIT_COMPLETION with reinit_completion

For the casual device driver writer, it is hard to remember when to use
init_completion (to init a completion structure) or INIT_COMPLETION (to
*reinit* a completion structure). Furthermore, while all other
completion functions exepct a pointer as a parameter, INIT_COMPLETION
does not. To make it easier to remember which function to use and to
make code more readable, introduce a new inline function with the proper
name and consistent argument type. Update the kernel-doc for
init_completion while we are here.

Signed-off-by: Wolfram Sang <[e-mail]>
Acked-by: Linus Walleij <[e-mail]> (personally at LCE13)
Cc: Ingo Molnar <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/completion.h

···
  *
  * See also:  complete(), wait_for_completion() (and friends _timeout,
  * _interruptible, _interruptible_timeout, and _killable), init_completion(),
- * and macros DECLARE_COMPLETION(), DECLARE_COMPLETION_ONSTACK(), and
- * INIT_COMPLETION().
+ * reinit_completion(), and macros DECLARE_COMPLETION(),
+ * DECLARE_COMPLETION_ONSTACK().
  */
 struct completion {
 	unsigned int done;
···
 
 /**
  * init_completion - Initialize a dynamically allocated completion
- * @x:  completion structure that is to be initialized
+ * @x:  pointer to completion structure that is to be initialized
  *
  * This inline function will initialize a dynamically created completion
  * structure.
···
 {
 	x->done = 0;
 	init_waitqueue_head(&x->wait);
+}
+
+/**
+ * reinit_completion - reinitialize a completion structure
+ * @x:  pointer to completion structure that is to be reinitialized
+ *
+ * This inline function should be used to reinitialize a completion structure so it can
+ * be reused. This is especially important after complete_all() is used.
+ */
+static inline void reinit_completion(struct completion *x)
+{
+	x->done = 0;
 }
 
 extern void wait_for_completion(struct completion *);