sched/debug: Rename 'schedstat_val()' -> 'schedstat_val_or_zero()'

The schedstat_val() macro's behavior is kind of surprising: when
schedstat is runtime disabled, it returns zero.  Rename it to
schedstat_val_or_zero().

There's also a need for a similar macro which doesn't have the 'if
(schedstat_enable())' check, to avoid doing the check twice.  Create a
new 'schedstat_val()' macro for that.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/3bb1d2367d041fee333b0dde17171e709395b675.1466184592.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/debug.c

@@ -429,9 +429,9 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p)
 		p->prio);
 
 	SEQ_printf(m, "%9Ld.%06ld %9Ld.%06ld %9Ld.%06ld",
-		SPLIT_NS(schedstat_val(p->se.statistics.wait_sum)),
+		SPLIT_NS(schedstat_val_or_zero(p->se.statistics.wait_sum)),
 		SPLIT_NS(p->se.sum_exec_runtime),
-		SPLIT_NS(schedstat_val(p->se.statistics.sum_sleep_runtime)));
+		SPLIT_NS(schedstat_val_or_zero(p->se.statistics.sum_sleep_runtime)));
 
 #ifdef CONFIG_NUMA_BALANCING
 	SEQ_printf(m, " %d %d", task_node(p), task_numa_group_id(p));

kernel/sched/stats.h

@@ -33,7 +33,8 @@ rq_sched_info_dequeued(struct rq *rq, unsigned long long delta)
 #define schedstat_inc(var)		do { if (schedstat_enabled()) { var++; } } while (0)
 #define schedstat_add(var, amt)		do { if (schedstat_enabled()) { var += (amt); } } while (0)
 #define schedstat_set(var, val)		do { if (schedstat_enabled()) { var = (val); } } while (0)
-#define schedstat_val(var)		((schedstat_enabled()) ? (var) : 0)
+#define schedstat_val(var)		(var)
+#define schedstat_val_or_zero(var)	((schedstat_enabled()) ? (var) : 0)
 
 #else /* !CONFIG_SCHEDSTATS */
 static inline void
@@ -50,6 +51,7 @@ rq_sched_info_depart(struct rq *rq, unsigned long long delta)
 #define schedstat_add(var, amt)		do { } while (0)
 #define schedstat_set(var, val)		do { } while (0)
 #define schedstat_val(var)		0
+#define schedstat_val_or_zero(var)	0
 #endif /* CONFIG_SCHEDSTATS */
 
 #ifdef CONFIG_SCHED_INFO