[PATCH 3/4] sched/fair: Check for blocked task after time check

[Shrikanth Hegde]

nohz.has_blocked can be updated often as and when CPUs enter idle state.
But stats are updated only at regular intervals. Usually fixed to
LOAD_AVG_PERIOD=32. 

Read the value only after time check is successful to avoid cache
references to it.

Signed-off-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
---
 kernel/sched/fair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 55746274af06..5534822fd754 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12440,8 +12440,8 @@ static void nohz_balancer_kick(struct rq *rq)
 	 */
 	nohz_balance_exit_idle(rq);
 
-	if (READ_ONCE(nohz.has_blocked) &&
-	    time_after(now, READ_ONCE(nohz.next_blocked)))
+	if (time_after(now, READ_ONCE(nohz.next_blocked)) &&
+	    READ_ONCE(nohz.has_blocked))
 		flags = NOHZ_STATS_KICK;
 
 	if (time_before(now, nohz.next_balance))
-- 
2.43.0