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Commit 79a6cdeb authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Linus Torvalds
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cpuhotplug: do not need cpu_hotplug_begin() when CONFIG_HOTPLUG_CPU=n 



Since when CONFIG_HOTPLUG_CPU=n, get_online_cpus() do nothing, so we don't
need cpu_hotplug_begin() either.

This patch moves cpu_hotplug_begin()/cpu_hotplug_done() into the code
block of CONFIG_HOTPLUG_CPU=y.

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>

Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c9d221f8

kernel/cpu.c

+22 −18
Original line number Diff line number Diff line
@@ -20,6 +20,20 @@ 
/* Serializes the updates to cpu_online_mask, cpu_present_mask */

static DEFINE_MUTEX(cpu_add_remove_lock);



/*

 * The following two API's must be used when attempting

 * to serialize the updates to cpu_online_mask, cpu_present_mask.

 */

void cpu_maps_update_begin(void)

{

	mutex_lock(&cpu_add_remove_lock);

}



void cpu_maps_update_done(void)

{

	mutex_unlock(&cpu_add_remove_lock);

}



static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);



/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
@@ -27,6 +41,8 @@ static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain); 
 */

static int cpu_hotplug_disabled;



#ifdef CONFIG_HOTPLUG_CPU



static struct {

	struct task_struct *active_writer;

	struct mutex lock; /* Synchronizes accesses to refcount, */
@@ -41,8 +57,6 @@ static struct { 
	.refcount = 0,

};



#ifdef CONFIG_HOTPLUG_CPU



void get_online_cpus(void)

{

	might_sleep();
@@ -67,22 +81,6 @@ void put_online_cpus(void) 
}

EXPORT_SYMBOL_GPL(put_online_cpus);



#endif	/* CONFIG_HOTPLUG_CPU */



/*

 * The following two API's must be used when attempting

 * to serialize the updates to cpu_online_mask, cpu_present_mask.

 */

void cpu_maps_update_begin(void)

{

	mutex_lock(&cpu_add_remove_lock);

}



void cpu_maps_update_done(void)

{

	mutex_unlock(&cpu_add_remove_lock);

}



/*

 * This ensures that the hotplug operation can begin only when the

 * refcount goes to zero.
@@ -124,6 +122,12 @@ static void cpu_hotplug_done(void) 
	cpu_hotplug.active_writer = NULL;

	mutex_unlock(&cpu_hotplug.lock);

}



#else /* #if CONFIG_HOTPLUG_CPU */

static void cpu_hotplug_begin(void) {}

static void cpu_hotplug_done(void) {}

#endif	/* #esle #if CONFIG_HOTPLUG_CPU */



/* Need to know about CPUs going up/down? */

int __ref register_cpu_notifier(struct notifier_block *nb)

{