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, 8 insertions, 8 deletions

diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index 412e6b42986f..c4ad54e0f288 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -153,7 +153,7 @@ static int pseries_add_processor(struct device_node *np)
         for (i = 0; i < nthreads; i++)
                 cpu_set(i, tmp);
 
-        lock_cpu_hotplug();
+        cpu_maps_update_begin();
 
         BUG_ON(!cpus_subset(cpu_present_map, cpu_possible_map));
 
@@ -190,7 +190,7 @@ static int pseries_add_processor(struct device_node *np)
         }
         err = 0;
 out_unlock:
-        unlock_cpu_hotplug();
+        cpu_maps_update_done();
         return err;
 }
 
@@ -211,7 +211,7 @@ static void pseries_remove_processor(struct device_node *np)
 
         nthreads = len / sizeof(u32);
 
-        lock_cpu_hotplug();
+        cpu_maps_update_begin();
         for (i = 0; i < nthreads; i++) {
                 for_each_present_cpu(cpu) {
                         if (get_hard_smp_processor_id(cpu) != intserv[i])
@@ -225,7 +225,7 @@ static void pseries_remove_processor(struct device_node *np)
                         printk(KERN_WARNING "Could not find cpu to remove "
                                "with physical id 0x%x\n", intserv[i]);
         }
-        unlock_cpu_hotplug();
+        cpu_maps_update_done();
 }
 
 static int pseries_smp_notifier(struct notifier_block *nb,
diff --git a/arch/powerpc/platforms/pseries/rtasd.c b/arch/powerpc/platforms/pseries/rtasd.c
index 73401c820110..e3078ce41518 100644
--- a/arch/powerpc/platforms/pseries/rtasd.c
+++ b/arch/powerpc/platforms/pseries/rtasd.c
@@ -382,7 +382,7 @@ static void do_event_scan_all_cpus(long delay)
 {
         int cpu;
 
-        lock_cpu_hotplug();
+        get_online_cpus();
         cpu = first_cpu(cpu_online_map);
         for (;;) {
                 set_cpus_allowed(current, cpumask_of_cpu(cpu));
@@ -390,15 +390,15 @@ static void do_event_scan_all_cpus(long delay)
                 set_cpus_allowed(current, CPU_MASK_ALL);
 
                 /* Drop hotplug lock, and sleep for the specified delay */
-                unlock_cpu_hotplug();
+                put_online_cpus();
                 msleep_interruptible(delay);
-                lock_cpu_hotplug();
+                get_online_cpus();
 
                 cpu = next_cpu(cpu, cpu_online_map);
                 if (cpu == NR_CPUS)
                         break;
         }
-        unlock_cpu_hotplug();
+        put_online_cpus();
 }
 
 static int rtasd(void *unused)