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>

2 files changed, 6 insertions, 6 deletions

diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index 482aec2a9631..96d0fd07c57d 100644
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -459,7 +459,7 @@ void __init lguest_arch_host_init(void)
 
         /* We don't need the complexity of CPUs coming and going while we're
          * doing this. */
-        lock_cpu_hotplug();
+        get_online_cpus();
         if (cpu_has_pge) { /* We have a broader idea of "global". */
                 /* Remember that this was originally set (for cleanup). */
                 cpu_had_pge = 1;
@@ -469,20 +469,20 @@ void __init lguest_arch_host_init(void)
                 /* Turn off the feature in the global feature set. */
                 clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
         }
-        unlock_cpu_hotplug();
+        put_online_cpus();
 };
 /*:*/
 
 void __exit lguest_arch_host_fini(void)
 {
         /* If we had PGE before we started, turn it back on now. */
-        lock_cpu_hotplug();
+        get_online_cpus();
         if (cpu_had_pge) {
                 set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
                 /* adjust_pge's argument "1" means set PGE. */
                 on_each_cpu(adjust_pge, (void *)1, 0, 1);
         }
-        unlock_cpu_hotplug();
+        put_online_cpus();
 }
 
 
diff --git a/drivers/s390/char/sclp_config.c b/drivers/s390/char/sclp_config.c
index 5322e5e54a98..9dc77f14fa52 100644
--- a/drivers/s390/char/sclp_config.c
+++ b/drivers/s390/char/sclp_config.c
@@ -29,12 +29,12 @@ static void sclp_cpu_capability_notify(struct work_struct *work)
         struct sys_device *sysdev;
 
         printk(KERN_WARNING TAG "cpu capability changed.\n");
-        lock_cpu_hotplug();
+        get_online_cpus();
         for_each_online_cpu(cpu) {
                 sysdev = get_cpu_sysdev(cpu);
                 kobject_uevent(&sysdev->kobj, KOBJ_CHANGE);
         }
-        unlock_cpu_hotplug();
+        put_online_cpus();
 }
 
 static void sclp_conf_receiver_fn(struct evbuf_header *evbuf)