4 files changed, 66 insertions, 27 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index cc5d57d1d0b6..ba89f40abe6a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7388,26 +7388,12 @@ static int __perf_cgroup_move(void *info)
         return 0;
 }
 
-static void perf_cgroup_move(struct task_struct *task)
+static void
+perf_cgroup_attach_task(struct cgroup *cgrp, struct task_struct *task)
 {
         task_function_call(task, __perf_cgroup_move, task);
 }
 
-static void perf_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
-                struct cgroup *old_cgrp, struct task_struct *task,
-                bool threadgroup)
-{
-        perf_cgroup_move(task);
-        if (threadgroup) {
-                struct task_struct *c;
-                rcu_read_lock();
-                list_for_each_entry_rcu(c, &task->thread_group, thread_group) {
-                        perf_cgroup_move(c);
-                }
-                rcu_read_unlock();
-        }
-}
-
 static void perf_cgroup_exit(struct cgroup_subsys *ss, struct cgroup *cgrp,
                 struct cgroup *old_cgrp, struct task_struct *task)
 {
@@ -7419,7 +7405,7 @@ static void perf_cgroup_exit(struct cgroup_subsys *ss, struct cgroup *cgrp,
         if (!(task->flags & PF_EXITING))
                 return;
 
-        perf_cgroup_move(task);
+        perf_cgroup_attach_task(cgrp, task);
 }
 
 struct cgroup_subsys perf_subsys = {
@@ -7428,6 +7414,6 @@ struct cgroup_subsys perf_subsys = {
         .create         = perf_cgroup_create,
         .destroy        = perf_cgroup_destroy,
         .exit           = perf_cgroup_exit,
-        .attach         = perf_cgroup_attach,
+        .attach_task    = perf_cgroup_attach_task,
 };
 #endif /* CONFIG_CGROUP_PERF */
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 77a7671dd147..89419ff92e99 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1648,7 +1648,6 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
         if (IS_ERR(t))
                 return PTR_ERR(t);
         kthread_bind(t, cpu);
-        set_task_state(t, TASK_INTERRUPTIBLE);
         per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
         WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
         per_cpu(rcu_cpu_kthread_task, cpu) = t;
@@ -1756,7 +1755,6 @@ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
                 if (IS_ERR(t))
                         return PTR_ERR(t);
                 raw_spin_lock_irqsave(&rnp->lock, flags);
-                set_task_state(t, TASK_INTERRUPTIBLE);
                 rnp->node_kthread_task = t;
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 sp.sched_priority = 99;
@@ -1765,6 +1763,8 @@ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
         return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index);
 }
 
+static void rcu_wake_one_boost_kthread(struct rcu_node *rnp);
+
 /*
  * Spawn all kthreads -- called as soon as the scheduler is running.
  */
@@ -1772,18 +1772,30 @@ static int __init rcu_spawn_kthreads(void)
 {
         int cpu;
         struct rcu_node *rnp;
+        struct task_struct *t;
 
         rcu_kthreads_spawnable = 1;
         for_each_possible_cpu(cpu) {
                 per_cpu(rcu_cpu_has_work, cpu) = 0;
-                if (cpu_online(cpu))
+                if (cpu_online(cpu)) {
                         (void)rcu_spawn_one_cpu_kthread(cpu);
+                        t = per_cpu(rcu_cpu_kthread_task, cpu);
+                        if (t)
+                                wake_up_process(t);
+                }
         }
         rnp = rcu_get_root(rcu_state);
         (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
+        if (rnp->node_kthread_task)
+                wake_up_process(rnp->node_kthread_task);
         if (NUM_RCU_NODES > 1) {
-                rcu_for_each_leaf_node(rcu_state, rnp)
+                rcu_for_each_leaf_node(rcu_state, rnp) {
                         (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
+                        t = rnp->node_kthread_task;
+                        if (t)
+                                wake_up_process(t);
+                        rcu_wake_one_boost_kthread(rnp);
+                }
         }
         return 0;
 }
@@ -2188,14 +2200,14 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
         raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
 }
 
-static void __cpuinit rcu_online_cpu(int cpu)
+static void __cpuinit rcu_prepare_cpu(int cpu)
 {
         rcu_init_percpu_data(cpu, &rcu_sched_state, 0);
         rcu_init_percpu_data(cpu, &rcu_bh_state, 0);
         rcu_preempt_init_percpu_data(cpu);
 }
 
-static void __cpuinit rcu_online_kthreads(int cpu)
+static void __cpuinit rcu_prepare_kthreads(int cpu)
 {
         struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
         struct rcu_node *rnp = rdp->mynode;
@@ -2209,6 +2221,31 @@ static void __cpuinit rcu_online_kthreads(int cpu)
 }
 
 /*
+ * kthread_create() creates threads in TASK_UNINTERRUPTIBLE state,
+ * but the RCU threads are woken on demand, and if demand is low this
+ * could be a while triggering the hung task watchdog.
+ *
+ * In order to avoid this, poke all tasks once the CPU is fully
+ * up and running.
+ */
+static void __cpuinit rcu_online_kthreads(int cpu)
+{
+        struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
+        struct rcu_node *rnp = rdp->mynode;
+        struct task_struct *t;
+
+        t = per_cpu(rcu_cpu_kthread_task, cpu);
+        if (t)
+                wake_up_process(t);
+
+        t = rnp->node_kthread_task;
+        if (t)
+                wake_up_process(t);
+
+        rcu_wake_one_boost_kthread(rnp);
+}
+
+/*
  * Handle CPU online/offline notification events.
  */
 static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
@@ -2221,10 +2258,11 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
         switch (action) {
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
-                rcu_online_cpu(cpu);
-                rcu_online_kthreads(cpu);
+                rcu_prepare_cpu(cpu);
+                rcu_prepare_kthreads(cpu);
                 break;
         case CPU_ONLINE:
+                rcu_online_kthreads(cpu);
         case CPU_DOWN_FAILED:
                 rcu_node_kthread_setaffinity(rnp, -1);
                 rcu_cpu_kthread_setrt(cpu, 1);
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index a767b7dac365..c8bff3099a89 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1295,7 +1295,6 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
         if (IS_ERR(t))
                 return PTR_ERR(t);
         raw_spin_lock_irqsave(&rnp->lock, flags);
-        set_task_state(t, TASK_INTERRUPTIBLE);
         rnp->boost_kthread_task = t;
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
         sp.sched_priority = RCU_KTHREAD_PRIO;
@@ -1303,6 +1302,12 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
         return 0;
 }
 
+static void __cpuinit rcu_wake_one_boost_kthread(struct rcu_node *rnp)
+{
+        if (rnp->boost_kthread_task)
+                wake_up_process(rnp->boost_kthread_task);
+}
+
 #else /* #ifdef CONFIG_RCU_BOOST */
 
 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
@@ -1326,6 +1331,10 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
         return 0;
 }
 
+static void __cpuinit rcu_wake_one_boost_kthread(struct rcu_node *rnp)
+{
+}
+
 #endif /* #else #ifdef CONFIG_RCU_BOOST */
 
 #ifndef CONFIG_SMP
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4fc92445a29c..f175d98bd355 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -938,6 +938,12 @@ static struct ctl_table kern_table[] = {
         },
 #endif
 #ifdef CONFIG_PERF_EVENTS
+        /*
+         * User-space scripts rely on the existence of this file
+         * as a feature check for perf_events being enabled.
+         *
+         * So it's an ABI, do not remove!
+         */
         {
                 .procname       = "perf_event_paranoid",
                 .data           = &sysctl_perf_event_paranoid,