cpuset: Make cpuset hotplug synchronous

[linux.git] / kernel / cgroup / cpuset.c

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index cab5fd1ee7671a88c03e6d4981099435006dd1b8..227bc25d951dd4b0157adfec069b26a2dd97a56a 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2277,15 +2277,8 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs)
        mutex_unlock(&cpuset_mutex);
 }
 
-static bool force_rebuild;
-
-void cpuset_force_rebuild(void)
-{
-       force_rebuild = true;
-}
-
 /**
- * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset
+ * cpuset_hotplug - handle CPU/memory hotunplug for a cpuset
  *
  * This function is called after either CPU or memory configuration has
  * changed and updates cpuset accordingly.  The top_cpuset is always
@@ -2300,7 +2293,7 @@ void cpuset_force_rebuild(void)
  * Note that CPU offlining during suspend is ignored.  We don't modify
  * cpusets across suspend/resume cycles at all.
  */
-static void cpuset_hotplug_workfn(struct work_struct *work)
+static void cpuset_hotplug(bool use_cpu_hp_lock)
 {
        static cpumask_t new_cpus;
        static nodemask_t new_mems;
@@ -2358,25 +2351,31 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
        }
 
        /* rebuild sched domains if cpus_allowed has changed */
-       if (cpus_updated || force_rebuild) {
-               force_rebuild = false;
-               rebuild_sched_domains();
+       if (cpus_updated) {
+               if (use_cpu_hp_lock)
+                       rebuild_sched_domains();
+               else {
+                       /* Acquiring cpu_hotplug_lock is not required.
+                        * When cpuset_hotplug() is called in hotplug path,
+                        * cpu_hotplug_lock is held by the hotplug context
+                        * which is waiting for cpuhp_thread_fun to indicate
+                        * completion of callback.
+                        */
+                       mutex_lock(&cpuset_mutex);
+                       rebuild_sched_domains_cpuslocked();
+                       mutex_unlock(&cpuset_mutex);
+               }
        }
 }
 
-void cpuset_update_active_cpus(void)
+static void cpuset_hotplug_workfn(struct work_struct *work)
 {
-       /*
-        * We're inside cpu hotplug critical region which usually nests
-        * inside cgroup synchronization.  Bounce actual hotplug processing
-        * to a work item to avoid reverse locking order.
-        */
-       schedule_work(&cpuset_hotplug_work);
+       cpuset_hotplug(true);
 }
 
-void cpuset_wait_for_hotplug(void)
+void cpuset_update_active_cpus(void)
 {
-       flush_work(&cpuset_hotplug_work);
+       cpuset_hotplug(false);
 }
 
 /*