sched/headers: Move task statistics APIs from <linux/sched.h> to <linux/sched/stat.h>

There are a number of task statistics related variables and methods exported
via sched.h - collect them into <linux/sched/stat.h> and include it from
their usage sites.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/s390/appldata/appldata_base.c

@@ -12,6 +12,7 @@
 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
 
 #include <linux/module.h>
+#include <linux/sched/stat.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/errno.h>

include/linux/sched.h

@@ -46,16 +46,6 @@ struct nameidata;
 struct signal_struct;
 struct sighand_struct;
 
-extern unsigned long total_forks;
-extern int nr_threads;
-DECLARE_PER_CPU(unsigned long, process_counts);
-extern int nr_processes(void);
-extern unsigned long nr_running(void);
-extern bool single_task_running(void);
-extern unsigned long nr_iowait(void);
-extern unsigned long nr_iowait_cpu(int cpu);
-extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load);
-
 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
 extern void cpu_load_update_nohz_start(void);
 extern void cpu_load_update_nohz_stop(void);

include/linux/sched/stat.h

@@ -3,4 +3,22 @@
 
 #include <linux/sched.h>
 
+/*
+ * Various counters maintained by the scheduler and fork(),
+ * exposed via /proc, sys.c or used by drivers via these APIs.
+ *
+ * ( Note that all these values are aquired without locking,
+ *   so they can only be relied on in narrow circumstances. )
+ */
+
+extern unsigned long total_forks;
+extern int nr_threads;
+DECLARE_PER_CPU(unsigned long, process_counts);
+extern int nr_processes(void);
+extern unsigned long nr_running(void);
+extern bool single_task_running(void);
+extern unsigned long nr_iowait(void);
+extern unsigned long nr_iowait_cpu(int cpu);
+extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load);
+
 #endif /* _LINUX_SCHED_STAT_H */