linux-kernel - [PATCH v3 14/15] smp: Create a new function to bringup nonboot cpus online

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Date:   Sun, 23 Feb 2020 19:29:41 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        Qais Yousef <qais.yousef@....com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Nicholas Piggin <npiggin@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        Eiichi Tsukata <devel@...ukata.com>,
        Zhenzhong Duan <zhenzhong.duan@...cle.com>,
        Nadav Amit <namit@...are.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 14/15] smp: Create a new function to bringup nonboot cpus online

This is the last direct user of cpu_up() before we can hide it now as
internal implementation detail of the cpu subsystem.

Signed-off-by: Qais Yousef <qais.yousef@....com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Josh Poimboeuf <jpoimboe@...hat.com>
CC: "Peter Zijlstra (Intel)" <peterz@...radead.org>
CC: Jiri Kosina <jkosina@...e.cz>
CC: Nicholas Piggin <npiggin@...il.com>
CC: Daniel Lezcano <daniel.lezcano@...aro.org>
CC: Ingo Molnar <mingo@...nel.org>
CC: Eiichi Tsukata <devel@...ukata.com>
CC: Zhenzhong Duan <zhenzhong.duan@...cle.com>
CC: Nadav Amit <namit@...are.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
CC: linux-kernel@...r.kernel.org
---
 include/linux/cpu.h |  1 +
 kernel/cpu.c        | 12 ++++++++++++
 kernel/smp.c        |  9 +--------
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index aebe8186cb07..3d3caecef395 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -94,6 +94,7 @@ void notify_cpu_starting(unsigned int cpu);
 extern void cpu_maps_update_begin(void);
 extern void cpu_maps_update_done(void);
 extern int bringup_hibernate_cpu(unsigned int sleep_cpu);
+extern void smp_bringup_nonboot_cpus(unsigned int setup_max_cpus);
 
 #else	/* CONFIG_SMP */
 #define cpuhp_tasks_frozen	0
diff --git a/kernel/cpu.c b/kernel/cpu.c
index bf39c5bfb6d9..7c6aa427a3a3 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1299,6 +1299,18 @@ int bringup_hibernate_cpu(unsigned int sleep_cpu)
 	return 0;
 }
 
+void smp_bringup_nonboot_cpus(unsigned int setup_max_cpus)
+{
+	unsigned int cpu;
+
+	for_each_present_cpu(cpu) {
+		if (num_online_cpus() >= setup_max_cpus)
+			break;
+		if (!cpu_online(cpu))
+			cpu_up(cpu);
+	}
+}
+
 #ifdef CONFIG_PM_SLEEP_SMP
 static cpumask_var_t frozen_cpus;
 
diff --git a/kernel/smp.c b/kernel/smp.c
index d0ada39eb4d4..9e793cfd6128 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -589,20 +589,13 @@ void __init setup_nr_cpu_ids(void)
 void __init smp_init(void)
 {
 	int num_nodes, num_cpus;
-	unsigned int cpu;
 
 	idle_threads_init();
 	cpuhp_threads_init();
 
 	pr_info("Bringing up secondary CPUs ...\n");
 
-	/* FIXME: This should be done in userspace --RR */
-	for_each_present_cpu(cpu) {
-		if (num_online_cpus() >= setup_max_cpus)
-			break;
-		if (!cpu_online(cpu))
-			cpu_up(cpu);
-	}
+	smp_bringup_nonboot_cpus(setup_max_cpus);
 
 	num_nodes = num_online_nodes();
 	num_cpus  = num_online_cpus();
-- 
2.17.1