Merge remote-tracking branch 'gpio/for-next'

[karo-tx-linux.git] / kernel / cpu.c

diff --git a/kernel/cpu.c b/kernel/cpu.c
index b2b227b821232d811d371fc24c672ad0fb715cf2..63aa50d7ce1efa16f9c29faa97f734f8c5db5d34 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -113,7 +113,7 @@ EXPORT_SYMBOL_GPL(put_online_cpus);
  * get_online_cpus() not an api which is called all that often.
  *
  */
-static void cpu_hotplug_begin(void)
+void cpu_hotplug_begin(void)
 {
        cpu_hotplug.active_writer = current;
 
@@ -127,7 +127,7 @@ static void cpu_hotplug_begin(void)
        }
 }
 
-static void cpu_hotplug_done(void)
+void cpu_hotplug_done(void)
 {
        cpu_hotplug.active_writer = NULL;
        mutex_unlock(&cpu_hotplug.lock);
@@ -154,10 +154,7 @@ void cpu_hotplug_enable(void)
        cpu_maps_update_done();
 }
 
-#else /* #if CONFIG_HOTPLUG_CPU */
-static void cpu_hotplug_begin(void) {}
-static void cpu_hotplug_done(void) {}
-#endif /* #else #if CONFIG_HOTPLUG_CPU */
+#endif /* CONFIG_HOTPLUG_CPU */
 
 /* Need to know about CPUs going up/down? */
 int __ref register_cpu_notifier(struct notifier_block *nb)
@@ -311,6 +308,23 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
        }
        smpboot_park_threads(cpu);
 
+       /*
+        * By now we've cleared cpu_active_mask, wait for all preempt-disabled
+        * and RCU users of this state to go away such that all new such users
+        * will observe it.
+        *
+        * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
+        * not imply sync_sched(), so explicitly call both.
+        */
+#ifdef CONFIG_PREEMPT
+       synchronize_sched();
+#endif
+       synchronize_rcu();
+
+       /*
+        * So now all preempt/rcu users must observe !cpu_active().
+        */
+
        err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
        if (err) {
                /* CPU didn't die: tell everyone.  Can't complain. */