linux-kernel - [PATCH 8/8] kernel/cpu.c: Define bsp

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Date:	Wed,  5 Oct 2011 09:39:19 -0700
From:	"Fenghua Yu" <fenghua.yu@...el.com>
To:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H Peter Anvin" <hpa@...or.com>,
	"Zwane Mwaikambo" <zwane@....linux.org.uk>,
	"Tony Luck" <tony.luck@...el.com>,
	"Asit K Mallick" <asit.k.mallick@...el.com>,
	"Suresh B Siddha" <suresh.b.siddha@...el.com>,
	"Len Brown" <lenb@...nel.org>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"Fenghua Yu" <fenghua.yu@...el.com>
Subject: [PATCH 8/8] kernel/cpu.c: Define bsp_hotpluggable variable

From: Fenghua Yu <fenghua.yu@...el.com>

This gloable variable controls BSP (aka CPU0) hotplug. If set, BSP is
hotpluggable. By default, it's 0. On X86, kernel option bsp_hotpluggable sets
the variable as 1.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 include/linux/cpu.h |    2 ++
 kernel/cpu.c        |    5 +++++
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index b1a635a..1b0b1ad 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -172,6 +172,8 @@ extern void put_online_cpus(void);
 #define unregister_hotcpu_notifier(nb)	unregister_cpu_notifier(nb)
 int cpu_down(unsigned int cpu);
 
+extern int bsp_hotpluggable;
+
 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 extern void cpu_hotplug_driver_lock(void);
 extern void cpu_hotplug_driver_unlock(void);
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 12b7458..65d1a13 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -43,6 +43,11 @@ static int cpu_hotplug_disabled;
 
 #ifdef CONFIG_HOTPLUG_CPU
 
+/*
+ * If set, BSP (aka CPU0) can be onlined/offlined. By default, it's not set.
+ */
+int bsp_hotpluggable;
+
 static struct {
 	struct task_struct *active_writer;
 	struct mutex lock; /* Synchronizes accesses to refcount, */
-- 
1.6.0.3

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