The patch titled
cpuhotplug: do not need cpu_hotplug_begin() when CONFIG_HOTPLUG_CPU=n
has been added to the -mm tree. Its filename is
cpuhotplug-do-not-need-cpu_hotplug_begin-when-config_hotplug_cpu=n.patch
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------------------------------------------------------
Subject: cpuhotplug: do not need cpu_hotplug_begin() when CONFIG_HOTPLUG_CPU=n
From: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
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: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Cc: Gautham R Shenoy <ego@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cpu.c | 40 ++++++++++++++++++++++------------------
1 file changed, 22 insertions(+), 18 deletions(-)
diff -puN kernel/cpu.c~cpuhotplug-do-not-need-cpu_hotplug_begin-when-config_hotplug_cpu=n kernel/cpu.c
--- a/kernel/cpu.c~cpuhotplug-do-not-need-cpu_hotplug_begin-when-config_hotplug_cpu=n
+++ a/kernel/cpu.c
@@ -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(c
*/
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)
{
_
Patches currently in -mm which might be from laijs@xxxxxxxxxxxxxx are
cpuhotplug-do-not-need-cpu_hotplug_begin-when-config_hotplug_cpu=n.patch
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