[PATCH v2 2/2] sched: add READ_ONCE and use existing helper function to access ->avg_irq

[Shrikanth Hegde <sshegde@linux.vnet.ibm.com>]

Use existing helper function cpu_util_irq instead of referencing it
directly.

It was noted that avg_irq could be updated by different CPU than the one
which is trying to access it. avg_irq is updated with WRITE_ONCE. Use
READ_ONCE to access it in order to avoid any compiler optimizations.

Signed-off-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
---
 kernel/sched/fair.c  | 4 +---
 kernel/sched/sched.h | 2 +-
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1aeca3f943a8..02631060ca7e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9221,10 +9221,8 @@ static inline bool others_have_blocked(struct rq *rq)
 	if (thermal_load_avg(rq))
 		return true;

-#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
-	if (READ_ONCE(rq->avg_irq.util_avg))
+	if (cpu_util_irq(rq))
 		return true;
-#endif

 	return false;
 }
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e58a54bda77d..edc20c5cc7ce 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3125,7 +3125,7 @@ static inline bool uclamp_rq_is_idle(struct rq *rq)
 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
 static inline unsigned long cpu_util_irq(struct rq *rq)
 {
-	return rq->avg_irq.util_avg;
+	return READ_ONCE(rq->avg_irq.util_avg);
 }

 static inline
--
2.39.3