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/sched.c b/kernel/sched.c
index 86e55a9c2de6..672aa68bfeac 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7152,7 +7152,7 @@ static int load_balance_monitor(void *unused)
                 int i, cpu, balanced = 1;
 
                 /* Prevent cpus going down or coming up */
-                lock_cpu_hotplug();
+                get_online_cpus();
                 /* lockout changes to doms_cur[] array */
                 lock_doms_cur();
                 /*
@@ -7186,7 +7186,7 @@ static int load_balance_monitor(void *unused)
                 rcu_read_unlock();
 
                 unlock_doms_cur();
-                unlock_cpu_hotplug();
+                put_online_cpus();
 
                 if (!balanced)
                         timeout = sysctl_sched_min_bal_int_shares;