sched/headers: Introduce kernel/sched/build_policy.c and build multiple .c files there

Similarly to kernel/sched/build_utility.c, collect all 'scheduling policy' related
source code files into kernel/sched/build_policy.c:

    kernel/sched/idle.c

    kernel/sched/rt.c

    kernel/sched/cpudeadline.c
    kernel/sched/pelt.c

    kernel/sched/cputime.c
    kernel/sched/deadline.c

With the exception of fair.c, which we continue to build as a separate file
for build efficiency and parallelism reasons.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>

kernel/sched/Makefile

@@ -30,5 +30,5 @@ endif
 #
 obj-y += core.o
 obj-y += fair.o
+obj-y += build_policy.o
 obj-y += build_utility.o
-obj-y += idle.o rt.o deadline.o cputime.o cpudeadline.o pelt.o

kernel/sched/build_policy.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * These are the scheduling policy related scheduler files, built
+ * in a single compilation unit for build efficiency reasons.
+ *
+ * ( Incidentally, the size of the compilation unit is roughly
+ *   comparable to core.c and fair.c, the other two big
+ *   compilation units. This helps balance build time, while
+ *   coalescing source files to amortize header inclusion
+ *   cost. )
+ *
+ * core.c and fair.c are built separately.
+ */
+
+#include "sched.h"
+#include "pelt.h"
+
+#include "idle.c"
+
+#include "rt.c"
+
+#ifdef CONFIG_SMP
+# include "cpudeadline.c"
+# include "pelt.c"
+#endif
+
+#include "cputime.c"
+#include "deadline.c"
+

kernel/sched/cpudeadline.c

@@ -6,7 +6,6 @@
  *
  *  Author: Juri Lelli <j.lelli@sssup.it>
  */
-#include "sched.h"
 
 static inline int parent(int i)
 {

kernel/sched/cputime.c

@@ -2,7 +2,6 @@
 /*
  * Simple CPU accounting cgroup controller
  */
-#include "sched.h"
 
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 

kernel/sched/deadline.c

@@ -15,8 +15,6 @@
  *                    Michael Trimarchi <michael@amarulasolutions.com>,
  *                    Fabio Checconi <fchecconi@gmail.com>
  */
-#include "sched.h"
-#include "pelt.h"
 
 struct dl_bandwidth def_dl_bandwidth;
 

kernel/sched/idle.c

@@ -6,9 +6,6 @@
  * (NOTE: these are not related to SCHED_IDLE batch scheduled
  *        tasks which are handled in sched/fair.c )
  */
-#include "sched.h"
-
-#include <trace/events/power.h>
 
 /* Linker adds these: start and end of __cpuidle functions */
 extern char __cpuidle_text_start[], __cpuidle_text_end[];

kernel/sched/pelt.c

@@ -24,10 +24,6 @@
  *  Author: Vincent Guittot <vincent.guittot@linaro.org>
  */
 
-#include <linux/sched.h>
-#include "sched.h"
-#include "pelt.h"
-
 /*
  * Approximate:
  *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)

kernel/sched/rt.c

@@ -3,9 +3,6 @@
  * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
  * policies)
  */
-#include "sched.h"
-
-#include "pelt.h"
 
 int sched_rr_timeslice = RR_TIMESLICE;
 int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;

kernel/sched/sched.h

@@ -13,6 +13,7 @@
 #include <linux/prctl.h>
 #include <linux/ptrace_api.h>
 #include <linux/gfp_api.h>
+#include <linux/posix-timers.h>
 #include <linux/sched/clock.h>
 #include <linux/workqueue_api.h>
 #include <linux/tick.h>
@@ -113,8 +114,11 @@
 #include <linux/cpumask_api.h>
 #include <linux/ctype.h>
 #include <linux/file.h>
+#include <linux/hrtimer_api.h>
+#include <linux/interrupt.h>
 #include <linux/jiffies.h>
 #include <linux/kref_api.h>
+#include <linux/ktime_api.h>
 #include <linux/lockdep_api.h>
 #include <linux/module.h>
 #include <linux/mutex_api.h>
@@ -126,12 +130,16 @@
 #include <linux/sched/loadavg.h>
 #include <linux/sched/mm.h>
 #include <linux/sched/rseq_api.h>
+#include <linux/sched/signal.h>
 #include <linux/seq_file.h>
 #include <linux/seqlock.h>
+#include <linux/softirq.h>
+#include <linux/spinlock_api.h>
 #include <linux/syscalls_api.h>
 #include <linux/syscalls.h>
 #include <linux/topology.h>
 #include <linux/types.h>
+#include <linux/u64_stats_sync_api.h>
 #include <linux/uaccess.h>
 #include <linux/wait_api.h>
 #include <linux/workqueue_api.h>