linux-kernel - [RFC 53/60] cosched: Prevent balancing related functions from crossing hierarchy levels

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Date:   Fri,  7 Sep 2018 23:40:40 +0200
From:   Jan H. Schönherr <jschoenh@...zon.de>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Jan H. Schönherr <jschoenh@...zon.de>,
        linux-kernel@...r.kernel.org
Subject: [RFC 53/60] cosched: Prevent balancing related functions from crossing hierarchy levels

Modify update_blocked_averages() and update_cfs_rq_h_load() so that they
won't access the next higher hierarchy level, for which they don't hold a
lock.

This will have to be touched again, when load balancing is made
functional.

Signed-off-by: Jan H. Schönherr <jschoenh@...zon.de>
---
 kernel/sched/fair.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bc219c9c3097..210fcd534917 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7686,7 +7686,7 @@ static void update_blocked_averages(int cpu)
 
 		/* Propagate pending load changes to the parent, if any: */
 		se = cfs_rq->my_se;
-		if (se && !skip_blocked_update(se))
+		if (se && !is_sd_se(se) && !skip_blocked_update(se))
 			update_load_avg(cfs_rq_of(se), se, 0);
 
 		/*
@@ -7731,6 +7731,8 @@ static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
 
 	cfs_rq->h_load_next = NULL;
 	for_each_sched_entity(se) {
+		if (is_sd_se(se))
+			break;
 		cfs_rq = cfs_rq_of(se);
 		cfs_rq->h_load_next = se;
 		if (cfs_rq->last_h_load_update == now)
-- 
2.9.3.1.gcba166c.dirty