types: move struct rcuwait into types.h

Move rcuwait struct definition into types.h so that rcuwait can be used
without including rcuwait.h which includes other headers. Without this
change mm_types.h can't use rcuwait due to a the following circular
dependency:

mm_types.h -> rcuwait.h -> signal.h -> mm_types.h

Link: https://lkml.kernel.org/r/[e-mail]
Suggested-by: Matthew Wilcox <[e-mail]>
Signed-off-by: Suren Baghdasaryan <[e-mail]>
Acked-by: Davidlohr Bueso <[e-mail]>
Acked-by: Liam R. Howlett <[e-mail]>
Acked-by: Lorenzo Stoakes <[e-mail]>
Tested-by: Shivank Garg <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Cc: Christian Brauner <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: David Howells <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Jann Horn <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Klara Modin <[e-mail]>
Cc: Lokesh Gidra <[e-mail]>
Cc: Mateusz Guzik <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Oleg Nesterov <[e-mail]>
Cc: Pasha Tatashin <[e-mail]>
Cc: "Paul E . McKenney" <[e-mail]>
Cc: Peter Xu <[e-mail]>
Cc: Peter Zijlstra (Intel) <[e-mail]>
Cc: Shakeel Butt <[e-mail]>
Cc: Sourav Panda <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Wei Yang <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Stephen Rothwell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/linux/rcuwait.h

···
 
 #include <linux/rcupdate.h>
 #include <linux/sched/signal.h>
-
-/*
- * rcuwait provides a way of blocking and waking up a single
- * task in an rcu-safe manner.
- *
- * The only time @task is non-nil is when a user is blocked (or
- * checking if it needs to) on a condition, and reset as soon as we
- * know that the condition has succeeded and are awoken.
- */
-struct rcuwait {
-	struct task_struct __rcu *task;
-};
+#include <linux/types.h>
 
 #define __RCUWAIT_INITIALIZER(name)		\
 	{ .task = NULL, }

include/linux/types.h

···
 typedef int (*cmp_r_func_t)(const void *a, const void *b, const void *priv);
 typedef int (*cmp_func_t)(const void *a, const void *b);
 
+/*
+ * rcuwait provides a way of blocking and waking up a single
+ * task in an rcu-safe manner.
+ *
+ * The only time @task is non-nil is when a user is blocked (or
+ * checking if it needs to) on a condition, and reset as soon as we
+ * know that the condition has succeeded and are awoken.
+ */
+struct rcuwait {
+	struct task_struct __rcu *task;
+};
+
 #endif /*  __ASSEMBLY__ */
 #endif /* _LINUX_TYPES_H */