linux-kernel - [patch 2/4] i386: introduce the mechanism of disabling cpu hotplug control

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Message-ID: <20061108172732.C10294@unix-os.sc.intel.com>
Date:	Wed, 8 Nov 2006 17:27:32 -0800
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	ak@...e.de, akpm@...l.org
Cc:	shaohua.li@...el.com, linux-kernel@...r.kernel.org,
	discuss@...-64.org, ashok.raj@...el.com, suresh.b.siddha@...el.com,
	greg@...ah.com
Subject: [patch 2/4] i386: introduce the mechanism of disabling cpu hotplug control

Add 'enable_cpu_hotplug' flag and when cleared, the hotplug control file
("online") will not be added under /sys/devices/system/cpu/cpuX/

Next patch doing PCI quirks will use this.

Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
---

diff --git a/arch/i386/kernel/topology.c b/arch/i386/kernel/topology.c
index 07d6da3..844c08f 100644
--- a/arch/i386/kernel/topology.c
+++ b/arch/i386/kernel/topology.c
@@ -40,14 +40,18 @@ int arch_register_cpu(int num)
 	 * restrictions and assumptions in kernel. This basically
 	 * doesnt add a control file, one cannot attempt to offline
 	 * BSP.
+	 *
+	 * Also certain PCI quirks require not to enable hotplug control
+	 * for all CPU's.
 	 */
-	if (!num)
+	if (!num || !enable_cpu_hotplug)
 		cpu_devices[num].cpu.no_control = 1;
 
 	return register_cpu(&cpu_devices[num].cpu, num);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
+int enable_cpu_hotplug = 1;
 
 void arch_unregister_cpu(int num) {
 	return unregister_cpu(&cpu_devices[num].cpu);
diff --git a/include/asm-i386/cpu.h b/include/asm-i386/cpu.h
index b1bc7b1..9d914e1 100644
--- a/include/asm-i386/cpu.h
+++ b/include/asm-i386/cpu.h
@@ -13,6 +13,9 @@ struct i386_cpu {
 extern int arch_register_cpu(int num);
 #ifdef CONFIG_HOTPLUG_CPU
 extern void arch_unregister_cpu(int);
+extern int enable_cpu_hotplug;
+#else
+#define enable_cpu_hotplug	0
 #endif
 
 DECLARE_PER_CPU(int, cpu_state);
-
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