linux-kernel - [PATCH 1/2] CPU hotplug: Export cpu_hotplug

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Date:	Mon, 12 Aug 2013 09:45:53 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	rjw@...k.pl
Cc:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	srivatsa.bhat@...ux.vnet.ibm.com, isimatu.yasuaki@...fujitsu.com,
	Toshi Kani <toshi.kani@...com>
Subject: [PATCH 1/2] CPU hotplug: Export cpu_hotplug_begin() interface

cpu_hotplug_begin() and cpu_hotplug_done() are the interfaces to
acquire the writer lock of the cpu_hotplug.lock.  The interfaces are
used along with cpu_maps_update_begin() / cpu_maps_update_done() to
serialize the updates to the system cpu maps, such as cpu_online_mask
and cpu_present_mask.

cpu_present_mask is updated by the ACPI processor handler.  Therefore,
this patch changes the interfaces to global, and exports them in cpu.h.

Signed-off-by: Toshi Kani <toshi.kani@...com>
---
 include/linux/cpu.h |    4 ++++
 kernel/cpu.c        |    9 +++------
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index ab0eade..956c0a1 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -172,6 +172,8 @@ extern struct bus_type cpu_subsys;
 #ifdef CONFIG_HOTPLUG_CPU
 /* Stop CPUs going up and down. */
 
+extern void cpu_hotplug_begin(void);
+extern void cpu_hotplug_done(void);
 extern void get_online_cpus(void);
 extern void put_online_cpus(void);
 extern void cpu_hotplug_disable(void);
@@ -197,6 +199,8 @@ static inline void cpu_hotplug_driver_unlock(void)
 
 #else		/* CONFIG_HOTPLUG_CPU */
 
+static inline void cpu_hotplug_begin(void) {}
+static inline void cpu_hotplug_done(void) {}
 #define get_online_cpus()	do { } while (0)
 #define put_online_cpus()	do { } while (0)
 #define cpu_hotplug_disable()	do { } while (0)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index b2b227b..d7f07a2 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -113,7 +113,7 @@ EXPORT_SYMBOL_GPL(put_online_cpus);
  * get_online_cpus() not an api which is called all that often.
  *
  */
-static void cpu_hotplug_begin(void)
+void cpu_hotplug_begin(void)
 {
 	cpu_hotplug.active_writer = current;
 
@@ -127,7 +127,7 @@ static void cpu_hotplug_begin(void)
 	}
 }
 
-static void cpu_hotplug_done(void)
+void cpu_hotplug_done(void)
 {
 	cpu_hotplug.active_writer = NULL;
 	mutex_unlock(&cpu_hotplug.lock);
@@ -154,10 +154,7 @@ void cpu_hotplug_enable(void)
 	cpu_maps_update_done();
 }
 
-#else /* #if CONFIG_HOTPLUG_CPU */
-static void cpu_hotplug_begin(void) {}
-static void cpu_hotplug_done(void) {}
-#endif	/* #else #if CONFIG_HOTPLUG_CPU */
+#endif	/* CONFIG_HOTPLUG_CPU */
 
 /* Need to know about CPUs going up/down? */
 int __ref register_cpu_notifier(struct notifier_block *nb)
--
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