linux-kernel - [PATCH 01/30] sched: Restructure sched_class order sanity checks in sched

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Date: Tue, 18 Jun 2024 11:17:16 -1000
From: Tejun Heo <tj@...nel.org>
To: torvalds@...ux-foundation.org,
	mingo@...hat.com,
	peterz@...radead.org,
	juri.lelli@...hat.com,
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Cc: linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	kernel-team@...a.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 01/30] sched: Restructure sched_class order sanity checks in sched_init()

Currently, sched_init() checks that the sched_class'es are in the expected
order by testing each adjacency which is a bit brittle and makes it
cumbersome to add optional sched_class'es. Instead, let's verify whether
they're in the expected order using sched_class_above() which is what
matters.

Signed-off-by: Tejun Heo <tj@...nel.org>
Suggested-by: Peter Zijlstra <peterz@...radead.org>
Reviewed-by: David Vernet <dvernet@...a.com>
---
 kernel/sched/core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0935f9d4bb7b..b4d4551bc7f2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8164,12 +8164,12 @@ void __init sched_init(void)
 	int i;
 
 	/* Make sure the linker didn't screw up */
-	BUG_ON(&idle_sched_class != &fair_sched_class + 1 ||
-	       &fair_sched_class != &rt_sched_class + 1 ||
-	       &rt_sched_class   != &dl_sched_class + 1);
 #ifdef CONFIG_SMP
-	BUG_ON(&dl_sched_class != &stop_sched_class + 1);
+	BUG_ON(!sched_class_above(&stop_sched_class, &dl_sched_class));
 #endif
+	BUG_ON(!sched_class_above(&dl_sched_class, &rt_sched_class));
+	BUG_ON(!sched_class_above(&rt_sched_class, &fair_sched_class));
+	BUG_ON(!sched_class_above(&fair_sched_class, &idle_sched_class));
 
 	wait_bit_init();
 
-- 
2.45.2