linux-kernel - [PATCH 03/11] smp: Remove get_cpu from smp_call_function

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Message-Id: <20260203112401.3889029-4-zhouchuyi@bytedance.com>
Date: Tue,  3 Feb 2026 19:23:53 +0800
From: "Chuyi Zhou" <zhouchuyi@...edance.com>
To: <tglx@...utronix.de>, <mingo@...hat.com>, <luto@...nel.org>, 
	<peterz@...radead.org>, <paulmck@...nel.org>, <muchun.song@...ux.dev>, 
	<bp@...en8.de>, <dave.hansen@...ux.intel.com>
Cc: <linux-kernel@...r.kernel.org>, "Chuyi Zhou" <zhouchuyi@...edance.com>
Subject: [PATCH 03/11] smp: Remove get_cpu from smp_call_function_any

Now smp_call_function_single() would enable preemption before
csd_lock_wait() to reduce the critical section. To allow callers of
smp_call_function_any() to also benefit from this optimization, remove
get_cpu()/put_cpu() from smp_call_function_any().

Signed-off-by: Chuyi Zhou <zhouchuyi@...edance.com>
---
 kernel/smp.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 0858553f3666..f572716c3c7d 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -772,13 +772,18 @@ int smp_call_function_any(const struct cpumask *mask,
 	unsigned int cpu;
 	int ret;
 
+	/*
+	 * Prevent migration to another CPU after selecting the current CPU
+	 * as the target.
+	 */
+	guard(migrate)();
+
 	/* Try for same CPU (cheapest) */
-	cpu = get_cpu();
+	cpu = smp_processor_id();
 	if (!cpumask_test_cpu(cpu, mask))
 		cpu = sched_numa_find_nth_cpu(mask, 0, cpu_to_node(cpu));
 
 	ret = smp_call_function_single(cpu, func, info, wait);
-	put_cpu();
 	return ret;
 }
 EXPORT_SYMBOL_GPL(smp_call_function_any);
-- 
2.20.1