[PATCH 2/4] hotplug, x86: Add hotplug lock to missing places

[Toshi Kani <toshi.kani@hp.com>]

lock_device_hotplug() serializes CPU & Memory online/offline and hotplug
operations.  However, this lock is not held in the debug interfaces below
that initiate CPU online/offline operations.

 - _debug_hotplug_cpu(), cpu0 hotplug test interface enabled by
   CONFIG_DEBUG_HOTPLUG_CPU0.
 - cpu_probe_store() and cpu_release_store(), cpu hotplug test interface
   enabled by CONFIG_ARCH_CPU_PROBE_RELEASE.

This patch changes the above interfaces to hold lock_device_hotplug().

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 arch/x86/kernel/topology.c |    2 ++
 drivers/base/cpu.c         |   16 ++++++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index 5823bbd..a3f35eb 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -65,6 +65,7 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
 	if (!cpu_is_hotpluggable(cpu))
 		return -EINVAL;
 
+	lock_device_hotplug();
 	cpu_hotplug_driver_lock();
 
 	switch (action) {
@@ -91,6 +92,7 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
 	}
 
 	cpu_hotplug_driver_unlock();
+	unlock_device_hotplug();
 
 	return ret;
 }
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 4c358bc..4cc6928 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -88,7 +88,13 @@ static ssize_t cpu_probe_store(struct device *dev,
 			       const char *buf,
 			       size_t count)
 {
-	return arch_cpu_probe(buf, count);
+	ssize_t ret;
+
+	lock_device_hotplug();
+	ret = arch_cpu_probe(buf, count);
+	unlock_device_hotplug();
+
+	return ret;
 }
 
 static ssize_t cpu_release_store(struct device *dev,
@@ -96,7 +102,13 @@ static ssize_t cpu_release_store(struct device *dev,
 				 const char *buf,
 				 size_t count)
 {
-	return arch_cpu_release(buf, count);
+	ssize_t ret;
+
+	lock_device_hotplug();
+	ret = arch_cpu_release(buf, count);
+	unlock_device_hotplug();
+
+	return ret;
 }
 
 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);