Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[sfrench/cifs-2.6.git] / kernel / cpu.c

diff --git a/kernel/cpu.c b/kernel/cpu.c
index f1338452d9988ffff9b625f5043b106c322d229d..e82920b8bee14e62be2bb248d92413a85aff4aa9 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -315,6 +315,16 @@ void lockdep_assert_cpus_held(void)
        percpu_rwsem_assert_held(&cpu_hotplug_lock);
 }
 
+static void lockdep_acquire_cpus_lock(void)
+{
+       rwsem_acquire(&cpu_hotplug_lock.rw_sem.dep_map, 0, 0, _THIS_IP_);
+}
+
+static void lockdep_release_cpus_lock(void)
+{
+       rwsem_release(&cpu_hotplug_lock.rw_sem.dep_map, 1, _THIS_IP_);
+}
+
 /*
  * Wait for currently running CPU hotplug operations to complete (if any) and
  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
@@ -344,6 +354,17 @@ void cpu_hotplug_enable(void)
        cpu_maps_update_done();
 }
 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
+
+#else
+
+static void lockdep_acquire_cpus_lock(void)
+{
+}
+
+static void lockdep_release_cpus_lock(void)
+{
+}
+
 #endif /* CONFIG_HOTPLUG_CPU */
 
 #ifdef CONFIG_HOTPLUG_SMT
@@ -617,6 +638,12 @@ static void cpuhp_thread_fun(unsigned int cpu)
         */
        smp_mb();
 
+       /*
+        * The BP holds the hotplug lock, but we're now running on the AP,
+        * ensure that anybody asserting the lock is held, will actually find
+        * it so.
+        */
+       lockdep_acquire_cpus_lock();
        cpuhp_lock_acquire(bringup);
 
        if (st->single) {
@@ -662,6 +689,7 @@ static void cpuhp_thread_fun(unsigned int cpu)
        }
 
        cpuhp_lock_release(bringup);
+       lockdep_release_cpus_lock();
 
        if (!st->should_run)
                complete_ap_thread(st, bringup);