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, 2 insertions, 2 deletions

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 319821ef78af..51b5ee53571a 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -203,13 +203,13 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
         int ret;
 
         /* No CPUs can come up or down during this. */
-        lock_cpu_hotplug();
+        get_online_cpus();
         p = __stop_machine_run(fn, data, cpu);
         if (!IS_ERR(p))
                 ret = kthread_stop(p);
         else
                 ret = PTR_ERR(p);
-        unlock_cpu_hotplug();
+        put_online_cpus();
 
         return ret;
 }