3 files changed, 41 insertions, 184 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index f280e542e3e9..f08ee3bc5741 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -139,7 +139,7 @@ DEFINE_PER_CPU(char, rcu_cpu_has_work);
 
 #endif /* #ifdef CONFIG_RCU_BOOST */
 
-static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
 static void invoke_rcu_core(void);
 static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
 
@@ -1469,7 +1469,7 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
 
         /* Adjust any no-longer-needed kthreads. */
         rcu_stop_cpu_kthread(cpu);
-        rcu_node_kthread_setaffinity(rnp, -1);
+        rcu_boost_kthread_setaffinity(rnp, -1);
 
         /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */
 
@@ -2594,11 +2594,11 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
                 break;
         case CPU_ONLINE:
         case CPU_DOWN_FAILED:
-                rcu_node_kthread_setaffinity(rnp, -1);
+                rcu_boost_kthread_setaffinity(rnp, -1);
                 rcu_cpu_kthread_setrt(cpu, 1);
                 break;
         case CPU_DOWN_PREPARE:
-                rcu_node_kthread_setaffinity(rnp, cpu);
+                rcu_boost_kthread_setaffinity(rnp, cpu);
                 rcu_cpu_kthread_setrt(cpu, 0);
                 break;
         case CPU_DYING:
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 4d29169f2124..f08176172546 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -491,13 +491,8 @@ static void invoke_rcu_callbacks_kthread(void);
 static bool rcu_is_callbacks_kthread(void);
 #ifdef CONFIG_RCU_BOOST
 static void rcu_preempt_do_callbacks(void);
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
-                                          cpumask_var_t cm);
 static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
-                                                 struct rcu_node *rnp,
-                                                 int rnp_index);
-static void invoke_rcu_node_kthread(struct rcu_node *rnp);
-static void rcu_yield(void (*f)(unsigned long), unsigned long arg);
+                                                 struct rcu_node *rnp);
 #endif /* #ifdef CONFIG_RCU_BOOST */
 static void rcu_cpu_kthread_setrt(int cpu, int to_rt);
 static void __cpuinit rcu_prepare_kthreads(int cpu);
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 7f3244c0df01..0f8b5ec64a7d 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1069,6 +1069,16 @@ static void rcu_initiate_boost_trace(struct rcu_node *rnp)
 
 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 
+static void rcu_wake_cond(struct task_struct *t, int status)
+{
+        /*
+         * If the thread is yielding, only wake it when this
+         * is invoked from idle
+         */
+        if (status != RCU_KTHREAD_YIELDING || is_idle_task(current))
+                wake_up_process(t);
+}
+
 /*
  * Carry out RCU priority boosting on the task indicated by ->exp_tasks
  * or ->boost_tasks, advancing the pointer to the next task in the
@@ -1141,17 +1151,6 @@ static int rcu_boost(struct rcu_node *rnp)
 }
 
 /*
- * Timer handler to initiate waking up of boost kthreads that
- * have yielded the CPU due to excessive numbers of tasks to
- * boost.  We wake up the per-rcu_node kthread, which in turn
- * will wake up the booster kthread.
- */
-static void rcu_boost_kthread_timer(unsigned long arg)
-{
-        invoke_rcu_node_kthread((struct rcu_node *)arg);
-}
-
-/*
  * Priority-boosting kthread.  One per leaf rcu_node and one for the
  * root rcu_node.
  */
@@ -1174,8 +1173,9 @@ static int rcu_boost_kthread(void *arg)
                 else
                         spincnt = 0;
                 if (spincnt > 10) {
+                        rnp->boost_kthread_status = RCU_KTHREAD_YIELDING;
                         trace_rcu_utilization("End boost kthread@rcu_yield");
-                        rcu_yield(rcu_boost_kthread_timer, (unsigned long)rnp);
+                        schedule_timeout_interruptible(2);
                         trace_rcu_utilization("Start boost kthread@rcu_yield");
                         spincnt = 0;
                 }
@@ -1213,8 +1213,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
                         rnp->boost_tasks = rnp->gp_tasks;
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 t = rnp->boost_kthread_task;
-                if (t != NULL)
-                        wake_up_process(t);
+                if (t)
+                        rcu_wake_cond(t, rnp->boost_kthread_status);
         } else {
                 rcu_initiate_boost_trace(rnp);
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
@@ -1231,8 +1231,10 @@ static void invoke_rcu_callbacks_kthread(void)
         local_irq_save(flags);
         __this_cpu_write(rcu_cpu_has_work, 1);
         if (__this_cpu_read(rcu_cpu_kthread_task) != NULL &&
-            current != __this_cpu_read(rcu_cpu_kthread_task))
-                wake_up_process(__this_cpu_read(rcu_cpu_kthread_task));
+            current != __this_cpu_read(rcu_cpu_kthread_task)) {
+                rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task),
+                              __this_cpu_read(rcu_cpu_kthread_status));
+        }
         local_irq_restore(flags);
 }
 
@@ -1245,21 +1247,6 @@ static bool rcu_is_callbacks_kthread(void)
         return __get_cpu_var(rcu_cpu_kthread_task) == current;
 }
 
-/*
- * Set the affinity of the boost kthread.  The CPU-hotplug locks are
- * held, so no one should be messing with the existence of the boost
- * kthread.
- */
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
-                                          cpumask_var_t cm)
-{
-        struct task_struct *t;
-
-        t = rnp->boost_kthread_task;
-        if (t != NULL)
-                set_cpus_allowed_ptr(rnp->boost_kthread_task, cm);
-}
-
 #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000)
 
 /*
@@ -1276,15 +1263,19 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
  * Returns zero if all is well, a negated errno otherwise.
  */
 static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
-                                                 struct rcu_node *rnp,
-                                                 int rnp_index)
+                                                 struct rcu_node *rnp)
 {
+        int rnp_index = rnp - &rsp->node[0];
         unsigned long flags;
         struct sched_param sp;
         struct task_struct *t;
 
         if (&rcu_preempt_state != rsp)
                 return 0;
+
+        if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0)
+                return 0;
+
         rsp->boost = 1;
         if (rnp->boost_kthread_task != NULL)
                 return 0;
@@ -1328,20 +1319,6 @@ static void rcu_kthread_do_work(void)
 }
 
 /*
- * Wake up the specified per-rcu_node-structure kthread.
- * Because the per-rcu_node kthreads are immortal, we don't need
- * to do anything to keep them alive.
- */
-static void invoke_rcu_node_kthread(struct rcu_node *rnp)
-{
-        struct task_struct *t;
-
-        t = rnp->node_kthread_task;
-        if (t != NULL)
-                wake_up_process(t);
-}
-
-/*
  * Set the specified CPU's kthread to run RT or not, as specified by
  * the to_rt argument.  The CPU-hotplug locks are held, so the task
  * is not going away.
@@ -1366,45 +1343,6 @@ static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
 }
 
 /*
- * Timer handler to initiate the waking up of per-CPU kthreads that
- * have yielded the CPU due to excess numbers of RCU callbacks.
- * We wake up the per-rcu_node kthread, which in turn will wake up
- * the booster kthread.
- */
-static void rcu_cpu_kthread_timer(unsigned long arg)
-{
-        struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
-        struct rcu_node *rnp = rdp->mynode;
-
-        atomic_or(rdp->grpmask, &rnp->wakemask);
-        invoke_rcu_node_kthread(rnp);
-}
-
-/*
- * Drop to non-real-time priority and yield, but only after posting a
- * timer that will cause us to regain our real-time priority if we
- * remain preempted.  Either way, we restore our real-time priority
- * before returning.
- */
-static void rcu_yield(void (*f)(unsigned long), unsigned long arg)
-{
-        struct sched_param sp;
-        struct timer_list yield_timer;
-        int prio = current->rt_priority;
-
-        setup_timer_on_stack(&yield_timer, f, arg);
-        mod_timer(&yield_timer, jiffies + 2);
-        sp.sched_priority = 0;
-        sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp);
-        set_user_nice(current, 19);
-        schedule();
-        set_user_nice(current, 0);
-        sp.sched_priority = prio;
-        sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
-        del_timer(&yield_timer);
-}
-
-/*
  * Handle cases where the rcu_cpu_kthread() ends up on the wrong CPU.
  * This can happen while the corresponding CPU is either coming online
  * or going offline.  We cannot wait until the CPU is fully online
@@ -1476,7 +1414,7 @@ static int rcu_cpu_kthread(void *arg)
                 if (spincnt > 10) {
                         *statusp = RCU_KTHREAD_YIELDING;
                         trace_rcu_utilization("End CPU kthread@rcu_yield");
-                        rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu);
+                        schedule_timeout_interruptible(2);
                         trace_rcu_utilization("Start CPU kthread@rcu_yield");
                         spincnt = 0;
                 }
@@ -1533,48 +1471,6 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
 }
 
 /*
- * Per-rcu_node kthread, which is in charge of waking up the per-CPU
- * kthreads when needed.  We ignore requests to wake up kthreads
- * for offline CPUs, which is OK because force_quiescent_state()
- * takes care of this case.
- */
-static int rcu_node_kthread(void *arg)
-{
-        int cpu;
-        unsigned long flags;
-        unsigned long mask;
-        struct rcu_node *rnp = (struct rcu_node *)arg;
-        struct sched_param sp;
-        struct task_struct *t;
-
-        for (;;) {
-                rnp->node_kthread_status = RCU_KTHREAD_WAITING;
-                rcu_wait(atomic_read(&rnp->wakemask) != 0);
-                rnp->node_kthread_status = RCU_KTHREAD_RUNNING;
-                raw_spin_lock_irqsave(&rnp->lock, flags);
-                mask = atomic_xchg(&rnp->wakemask, 0);
-                rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
-                for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) {
-                        if ((mask & 0x1) == 0)
-                                continue;
-                        preempt_disable();
-                        t = per_cpu(rcu_cpu_kthread_task, cpu);
-                        if (!cpu_online(cpu) || t == NULL) {
-                                preempt_enable();
-                                continue;
-                        }
-                        per_cpu(rcu_cpu_has_work, cpu) = 1;
-                        sp.sched_priority = RCU_KTHREAD_PRIO;
-                        sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
-                        preempt_enable();
-                }
-        }
-        /* NOTREACHED */
-        rnp->node_kthread_status = RCU_KTHREAD_STOPPED;
-        return 0;
-}
-
-/*
  * Set the per-rcu_node kthread's affinity to cover all CPUs that are
  * served by the rcu_node in question.  The CPU hotplug lock is still
  * held, so the value of rnp->qsmaskinit will be stable.
@@ -1583,17 +1479,17 @@ static int rcu_node_kthread(void *arg)
  * no outgoing CPU.  If there are no CPUs left in the affinity set,
  * this function allows the kthread to execute on any CPU.
  */
-static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
 {
+        struct task_struct *t = rnp->boost_kthread_task;
+        unsigned long mask = rnp->qsmaskinit;
         cpumask_var_t cm;
         int cpu;
-        unsigned long mask = rnp->qsmaskinit;
 
-        if (rnp->node_kthread_task == NULL)
+        if (!t)
                 return;
-        if (!alloc_cpumask_var(&cm, GFP_KERNEL))
+        if (!zalloc_cpumask_var(&cm, GFP_KERNEL))
                 return;
-        cpumask_clear(cm);
         for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
                 if ((mask & 0x1) && cpu != outgoingcpu)
                         cpumask_set_cpu(cpu, cm);
@@ -1603,50 +1499,17 @@ static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
                         cpumask_clear_cpu(cpu, cm);
                 WARN_ON_ONCE(cpumask_weight(cm) == 0);
         }
-        set_cpus_allowed_ptr(rnp->node_kthread_task, cm);
-        rcu_boost_kthread_setaffinity(rnp, cm);
+        set_cpus_allowed_ptr(t, cm);
         free_cpumask_var(cm);
 }
 
 /*
- * Spawn a per-rcu_node kthread, setting priority and affinity.
- * Called during boot before online/offline can happen, or, if
- * during runtime, with the main CPU-hotplug locks held.  So only
- * one of these can be executing at a time.
- */
-static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
-                                                struct rcu_node *rnp)
-{
-        unsigned long flags;
-        int rnp_index = rnp - &rsp->node[0];
-        struct sched_param sp;
-        struct task_struct *t;
-
-        if (!rcu_scheduler_fully_active ||
-            rnp->qsmaskinit == 0)
-                return 0;
-        if (rnp->node_kthread_task == NULL) {
-                t = kthread_create(rcu_node_kthread, (void *)rnp,
-                                   "rcun/%d", rnp_index);
-                if (IS_ERR(t))
-                        return PTR_ERR(t);
-                raw_spin_lock_irqsave(&rnp->lock, flags);
-                rnp->node_kthread_task = t;
-                raw_spin_unlock_irqrestore(&rnp->lock, flags);
-                sp.sched_priority = 99;
-                sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
-                wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
-        }
-        return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index);
-}
-
-/*
  * Spawn all kthreads -- called as soon as the scheduler is running.
  */
 static int __init rcu_spawn_kthreads(void)
 {
-        int cpu;
         struct rcu_node *rnp;
+        int cpu;
 
         rcu_scheduler_fully_active = 1;
         for_each_possible_cpu(cpu) {
@@ -1655,10 +1518,10 @@ static int __init rcu_spawn_kthreads(void)
                         (void)rcu_spawn_one_cpu_kthread(cpu);
         }
         rnp = rcu_get_root(rcu_state);
-        (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
+        (void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
         if (NUM_RCU_NODES > 1) {
                 rcu_for_each_leaf_node(rcu_state, rnp)
-                        (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
+                        (void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
         }
         return 0;
 }
@@ -1672,8 +1535,7 @@ static void __cpuinit rcu_prepare_kthreads(int cpu)
         /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
         if (rcu_scheduler_fully_active) {
                 (void)rcu_spawn_one_cpu_kthread(cpu);
-                if (rnp->node_kthread_task == NULL)
-                        (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
+                (void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
         }
 }
 
@@ -1706,7 +1568,7 @@ static void rcu_stop_cpu_kthread(int cpu)
 
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 
-static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
 {
 }