cpu-hotplug: replace lock_cpu_hotplug() with get_online_cpus()

Replace all lock_cpu_hotplug/unlock_cpu_hotplug from the kernel and use
get_online_cpus and put_online_cpus instead as it highlights the
refcount semantics in these operations.

The new API guarantees protection against the cpu-hotplug operation, but
it doesn't guarantee serialized access to any of the local data
structures. Hence the changes needs to be reviewed.

In case of pseries_add_processor/pseries_remove_processor, use
cpu_maps_update_begin()/cpu_maps_update_done() as we're modifying the
cpu_present_map there.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 8 deletions

diff --git a/arch/x86/kernel/microcode.c b/arch/x86/kernel/microcode.c
index 09c315214a5e..40cfd5488719 100644
--- a/arch/x86/kernel/microcode.c
+++ b/arch/x86/kernel/microcode.c
@@ -436,7 +436,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_
                 return -EINVAL;
         }
 
-        lock_cpu_hotplug();
+        get_online_cpus();
         mutex_lock(&microcode_mutex);
 
         user_buffer = (void __user *) buf;
@@ -447,7 +447,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_
                 ret = (ssize_t)len;
 
         mutex_unlock(&microcode_mutex);
-        unlock_cpu_hotplug();
+        put_online_cpus();
 
         return ret;
 }
@@ -658,14 +658,14 @@ static ssize_t reload_store(struct sys_device *dev, const char *buf, size_t sz)
 
                 old = current->cpus_allowed;
 
-                lock_cpu_hotplug();
+                get_online_cpus();
                 set_cpus_allowed(current, cpumask_of_cpu(cpu));
 
                 mutex_lock(&microcode_mutex);
                 if (uci->valid)
                         err = cpu_request_microcode(cpu);
                 mutex_unlock(&microcode_mutex);
-                unlock_cpu_hotplug();
+                put_online_cpus();
                 set_cpus_allowed(current, old);
         }
         if (err)
@@ -817,9 +817,9 @@ static int __init microcode_init (void)
                 return PTR_ERR(microcode_pdev);
         }
 
-        lock_cpu_hotplug();
+        get_online_cpus();
         error = sysdev_driver_register(&cpu_sysdev_class, &mc_sysdev_driver);
-        unlock_cpu_hotplug();
+        put_online_cpus();
         if (error) {
                 microcode_dev_exit();
                 platform_device_unregister(microcode_pdev);
@@ -839,9 +839,9 @@ static void __exit microcode_exit (void)
 
         unregister_hotcpu_notifier(&mc_cpu_notifier);
 
-        lock_cpu_hotplug();
+        get_online_cpus();
         sysdev_driver_unregister(&cpu_sysdev_class, &mc_sysdev_driver);
-        unlock_cpu_hotplug();
+        put_online_cpus();
 
         platform_device_unregister(microcode_pdev);
 }