linux-kernel - [RESEND PATCH 1/2] sched/isolation: Use raw_smp_processor_id() in housekeeping_any

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Date:   Mon, 28 Feb 2022 15:15:50 +0100
From:   Nicolas Saenz Julienne <nsaenzju@...hat.com>
To:     mingo@...hat.com, peterz@...radead.org, frederic@...nel.org,
        rostedt@...dmis.org
Cc:     tglx@...utronix.de, mtosatti@...hat.com, bristot@...hat.com,
        linux-kernel@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>
Subject: [RESEND PATCH 1/2] sched/isolation: Use raw_smp_processor_id() in housekeeping_any_cpu()

housekeeping_any_cpu() will return a housekeeping CPU. That's it. It'll
try to optimize for NUMA locality and to use the local CPU when
possible, but it's not a requisite.

So let's use raw_smp_processor_id() instead of its vanilla counterpart
in order to allow users to query for housekeeping CPUs without having to
disable preemption.

Signed-off-by: Nicolas Saenz Julienne <nsaenzju@...hat.com>
---

NOTE: Resent as I forgot to CC the linux mailing list.

 include/linux/sched/isolation.h | 2 +-
 kernel/sched/isolation.c        | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index 8c15abd67aed..0c09ff1e4599 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -31,7 +31,7 @@ extern void __init housekeeping_init(void);
 
 static inline int housekeeping_any_cpu(enum hk_type type)
 {
-	return smp_processor_id();
+	return raw_smp_processor_id();
 }
 
 static inline const struct cpumask *housekeeping_cpumask(enum hk_type type)
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index b4d10815c45a..3b8e1d47bbc0 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -43,14 +43,15 @@ int housekeeping_any_cpu(enum hk_type type)
 
 	if (static_branch_unlikely(&housekeeping_overridden)) {
 		if (housekeeping.flags & BIT(type)) {
-			cpu = sched_numa_find_closest(housekeeping.cpumasks[type], smp_processor_id());
+			cpu = sched_numa_find_closest(housekeeping.cpumasks[type],
+						      raw_smp_processor_id());
 			if (cpu < nr_cpu_ids)
 				return cpu;
 
 			return cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask);
 		}
 	}
-	return smp_processor_id();
+	return raw_smp_processor_id();
 }
 EXPORT_SYMBOL_GPL(housekeeping_any_cpu);
 
-- 
2.35.1