sched/wait: Add wait_event_state_exclusive()

Allows exclusive waits with a custom @state.

Signed-off-by: Sergey Senozhatsky <[e-mail]>
Acked-by: Peter Zijlstra (Intel) <[e-mail]>
Signed-off-by: Miklos Szeredi <[e-mail]>

include/linux/wait.h

···
 	__ret;									\
 })
 
+#define __wait_event_state_exclusive(wq, condition, state)			\
+	___wait_event(wq, condition, state, 1, 0, schedule())
+
+#define wait_event_state_exclusive(wq, condition, state)			\
+({										\
+	int __ret = 0;								\
+	might_sleep();								\
+	if (!(condition))							\
+		__ret = __wait_event_state_exclusive(wq, condition, state);	\
+	__ret;									\
+})
+
 #define __wait_event_killable_timeout(wq_head, condition, timeout)		\
 	___wait_event(wq_head, ___wait_cond_timeout(condition),			\
 		      TASK_KILLABLE, 0, timeout,				\