linux-kernel - [PATCH 6.6 112/638] sched/fair: Take the scheduling domain into account in select_idle

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Message-ID: <20240324230116.1348576-113-sashal@kernel.org>
Date: Sun, 24 Mar 2024 18:52:29 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Keisuke Nishimura <keisuke.nishimura@...ia.fr>,
	Julia Lawall <julia.lawall@...ia.fr>,
	Ingo Molnar <mingo@...nel.org>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.6 112/638] sched/fair: Take the scheduling domain into account in select_idle_core()

From: Keisuke Nishimura <keisuke.nishimura@...ia.fr>

[ Upstream commit 23d04d8c6b8ec339057264659b7834027f3e6a63 ]

When picking a CPU on task wakeup, select_idle_core() has to take
into account the scheduling domain where the function looks for the CPU.

This is because the "isolcpus" kernel command line option can remove CPUs
from the domain to isolate them from other SMT siblings.

This change replaces the set of CPUs allowed to run the task from
p->cpus_ptr by the intersection of p->cpus_ptr and sched_domain_span(sd)
which is stored in the 'cpus' argument provided by select_idle_cpu().

Fixes: 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
Signed-off-by: Keisuke Nishimura <keisuke.nishimura@...ia.fr>
Signed-off-by: Julia Lawall <julia.lawall@...ia.fr>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/20240110131707.437301-2-keisuke.nishimura@inria.fr
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 fed669ec72bce..69fe62126a28e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7184,7 +7184,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
 		if (!available_idle_cpu(cpu)) {
 			idle = false;
 			if (*idle_cpu == -1) {
-				if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
+				if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, cpus)) {
 					*idle_cpu = cpu;
 					break;
 				}
@@ -7192,7 +7192,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
 			}
 			break;
 		}
-		if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
+		if (*idle_cpu == -1 && cpumask_test_cpu(cpu, cpus))
 			*idle_cpu = cpu;
 	}
 
-- 
2.43.0