ANDROID: schedstats/eas: guard properly to avoid breaking non-smp schedstats users

Add appropriate #ifdef guards to ensure the smp-only easstats structs
are not used when smp is not enabled. Arnd got a report from buildbot,
analysed it, and pointed out exactly what the issue was.

Reported-by: "Arnd Bergmann" <arnd@arndb.de>
Suggested-by: "Arnd Bergmann" <arnd@arndb.de>
Fixes: 4b85765a3d ("sched/fair: Add eas (& cas)
 specific rq, sd and task stats")
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
Change-Id: I60554dea20137f6774db3f59b4afd40a06554cfc
(cherry picked from commit fce0ecf04a)
[Fixed cherry-pick issue]
Signed-off-by: Quentin Perret <quentin.perret@arm.com>

kernel/sched/sched.h

@@ -768,9 +768,10 @@ struct rq {
 	/* try_to_wake_up() stats */
 	unsigned int ttwu_count;
 	unsigned int ttwu_local;
-
+#ifdef CONFIG_SMP
 	struct eas_stats eas_stats;
 #endif
+#endif
 
 #ifdef CONFIG_SMP
 	struct llist_head wake_list;

kernel/sched/stats.c

@@ -12,6 +12,7 @@
  */
 #define SCHEDSTAT_VERSION 15
 
+#ifdef CONFIG_SMP
 static inline void show_easstat(struct seq_file *seq, struct eas_stats *stats)
 {
 	/* eas-specific runqueue stats */
@@ -31,6 +32,7 @@ static inline void show_easstat(struct seq_file *seq, struct eas_stats *stats)
 	seq_printf(seq, "%llu %llu\n",
 	    stats->cas_attempts, stats->cas_count);
 }
+#endif
 
 static int show_schedstat(struct seq_file *seq, void *v)
 {
@@ -59,9 +61,9 @@ static int show_schedstat(struct seq_file *seq, void *v)
 
 		seq_printf(seq, "\n");
 
+#ifdef CONFIG_SMP
 		show_easstat(seq, &rq->eas_stats);
 
-#ifdef CONFIG_SMP
 		/* domain-specific stats */
 		rcu_read_lock();
 		for_each_domain(cpu, sd) {