1 files changed, 348 insertions, 225 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index d5bc43976c5a..ba06207b1dd3 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -36,7 +36,7 @@
 #include <linux/interrupt.h>
 #include <linux/sched.h>
 #include <linux/nmi.h>
-#include <asm/atomic.h>
+#include <linux/atomic.h>
 #include <linux/bitops.h>
 #include <linux/module.h>
 #include <linux/completion.h>
@@ -47,6 +47,9 @@
 #include <linux/mutex.h>
 #include <linux/time.h>
 #include <linux/kernel_stat.h>
+#include <linux/wait.h>
+#include <linux/kthread.h>
+#include <linux/prefetch.h>
 
 #include "rcutree.h"
 
@@ -67,9 +70,6 @@ static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
         .gpnum = -300, \
         .completed = -300, \
         .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \
-        .orphan_cbs_list = NULL, \
-        .orphan_cbs_tail = &structname.orphan_cbs_list, \
-        .orphan_qlen = 0, \
         .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \
         .n_force_qs = 0, \
         .n_force_qs_ngp = 0, \
@@ -82,10 +82,67 @@ DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
 struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
 DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
 
+static struct rcu_state *rcu_state;
+
+/*
+ * The rcu_scheduler_active variable transitions from zero to one just
+ * before the first task is spawned.  So when this variable is zero, RCU
+ * can assume that there is but one task, allowing RCU to (for example)
+ * optimized synchronize_sched() to a simple barrier().  When this variable
+ * is one, RCU must actually do all the hard work required to detect real
+ * grace periods.  This variable is also used to suppress boot-time false
+ * positives from lockdep-RCU error checking.
+ */
 int rcu_scheduler_active __read_mostly;
 EXPORT_SYMBOL_GPL(rcu_scheduler_active);
 
 /*
+ * The rcu_scheduler_fully_active variable transitions from zero to one
+ * during the early_initcall() processing, which is after the scheduler
+ * is capable of creating new tasks.  So RCU processing (for example,
+ * creating tasks for RCU priority boosting) must be delayed until after
+ * rcu_scheduler_fully_active transitions from zero to one.  We also
+ * currently delay invocation of any RCU callbacks until after this point.
+ *
+ * It might later prove better for people registering RCU callbacks during
+ * early boot to take responsibility for these callbacks, but one step at
+ * a time.
+ */
+static int rcu_scheduler_fully_active __read_mostly;
+
+#ifdef CONFIG_RCU_BOOST
+
+/*
+ * Control variables for per-CPU and per-rcu_node kthreads.  These
+ * handle all flavors of RCU.
+ */
+static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
+DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
+DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu);
+DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
+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 invoke_rcu_core(void);
+static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
+
+#define RCU_KTHREAD_PRIO 1      /* RT priority for per-CPU kthreads. */
+
+/*
+ * Track the rcutorture test sequence number and the update version
+ * number within a given test.  The rcutorture_testseq is incremented
+ * on every rcutorture module load and unload, so has an odd value
+ * when a test is running.  The rcutorture_vernum is set to zero
+ * when rcutorture starts and is incremented on each rcutorture update.
+ * These variables enable correlating rcutorture output with the
+ * RCU tracing information.
+ */
+unsigned long rcutorture_testseq;
+unsigned long rcutorture_vernum;
+
+/*
  * Return true if an RCU grace period is in progress.  The ACCESS_ONCE()s
  * permit this function to be invoked without holding the root rcu_node
  * structure's ->lock, but of course results can be subject to change.
@@ -127,11 +184,12 @@ void rcu_note_context_switch(int cpu)
         rcu_sched_qs(cpu);
         rcu_preempt_note_context_switch(cpu);
 }
+EXPORT_SYMBOL_GPL(rcu_note_context_switch);
 
 #ifdef CONFIG_NO_HZ
 DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
         .dynticks_nesting = 1,
-        .dynticks = 1,
+        .dynticks = ATOMIC_INIT(1),
 };
 #endif /* #ifdef CONFIG_NO_HZ */
 
@@ -143,6 +201,9 @@ module_param(blimit, int, 0);
 module_param(qhimark, int, 0);
 module_param(qlowmark, int, 0);
 
+int rcu_cpu_stall_suppress __read_mostly;
+module_param(rcu_cpu_stall_suppress, int, 0644);
+
 static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
 static int rcu_pending(int cpu);
 
@@ -174,6 +235,31 @@ void rcu_bh_force_quiescent_state(void)
 EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
 
 /*
+ * Record the number of times rcutorture tests have been initiated and
+ * terminated.  This information allows the debugfs tracing stats to be
+ * correlated to the rcutorture messages, even when the rcutorture module
+ * is being repeatedly loaded and unloaded.  In other words, we cannot
+ * store this state in rcutorture itself.
+ */
+void rcutorture_record_test_transition(void)
+{
+        rcutorture_testseq++;
+        rcutorture_vernum = 0;
+}
+EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
+
+/*
+ * Record the number of writer passes through the current rcutorture test.
+ * This is also used to correlate debugfs tracing stats with the rcutorture
+ * messages.
+ */
+void rcutorture_record_progress(unsigned long vernum)
+{
+        rcutorture_vernum++;
+}
+EXPORT_SYMBOL_GPL(rcutorture_record_progress);
+
+/*
  * Force a quiescent state for RCU-sched.
  */
 void rcu_sched_force_quiescent_state(void)
@@ -232,8 +318,8 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
                 return 1;
         }
 
-        /* If preemptable RCU, no point in sending reschedule IPI. */
-        if (rdp->preemptable)
+        /* If preemptible RCU, no point in sending reschedule IPI. */
+        if (rdp->preemptible)
                 return 0;
 
         /* The CPU is online, so send it a reschedule IPI. */
@@ -262,13 +348,25 @@ void rcu_enter_nohz(void)
         unsigned long flags;
         struct rcu_dynticks *rdtp;
 
-        smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
         local_irq_save(flags);
         rdtp = &__get_cpu_var(rcu_dynticks);
-        rdtp->dynticks++;
-        rdtp->dynticks_nesting--;
-        WARN_ON_ONCE(rdtp->dynticks & 0x1);
+        if (--rdtp->dynticks_nesting) {
+                local_irq_restore(flags);
+                return;
+        }
+        /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
+        smp_mb__before_atomic_inc();  /* See above. */
+        atomic_inc(&rdtp->dynticks);
+        smp_mb__after_atomic_inc();  /* Force ordering with next sojourn. */
+        WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
         local_irq_restore(flags);
+
+        /* If the interrupt queued a callback, get out of dyntick mode. */
+        if (in_irq() &&
+            (__get_cpu_var(rcu_sched_data).nxtlist ||
+             __get_cpu_var(rcu_bh_data).nxtlist ||
+             rcu_preempt_needs_cpu(smp_processor_id())))
+                set_need_resched();
 }
 
 /*
@@ -284,11 +382,16 @@ void rcu_exit_nohz(void)
 
         local_irq_save(flags);
         rdtp = &__get_cpu_var(rcu_dynticks);
-        rdtp->dynticks++;
-        rdtp->dynticks_nesting++;
-        WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
+        if (rdtp->dynticks_nesting++) {
+                local_irq_restore(flags);
+                return;
+        }
+        smp_mb__before_atomic_inc();  /* Force ordering w/previous sojourn. */
+        atomic_inc(&rdtp->dynticks);
+        /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
+        smp_mb__after_atomic_inc();  /* See above. */
+        WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
         local_irq_restore(flags);
-        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
 }
 
 /**
@@ -302,11 +405,15 @@ void rcu_nmi_enter(void)
 {
         struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
 
-        if (rdtp->dynticks & 0x1)
+        if (rdtp->dynticks_nmi_nesting == 0 &&
+            (atomic_read(&rdtp->dynticks) & 0x1))
                 return;
-        rdtp->dynticks_nmi++;
-        WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1));
-        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
+        rdtp->dynticks_nmi_nesting++;
+        smp_mb__before_atomic_inc();  /* Force delay from prior write. */
+        atomic_inc(&rdtp->dynticks);
+        /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
+        smp_mb__after_atomic_inc();  /* See above. */
+        WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
 }
 
 /**
@@ -320,11 +427,14 @@ void rcu_nmi_exit(void)
 {
         struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
 
-        if (rdtp->dynticks & 0x1)
+        if (rdtp->dynticks_nmi_nesting == 0 ||
+            --rdtp->dynticks_nmi_nesting != 0)
                 return;
-        smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
-        rdtp->dynticks_nmi++;
-        WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1);
+        /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
+        smp_mb__before_atomic_inc();  /* See above. */
+        atomic_inc(&rdtp->dynticks);
+        smp_mb__after_atomic_inc();  /* Force delay to next write. */
+        WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
 }
 
 /**
@@ -335,13 +445,7 @@ void rcu_nmi_exit(void)
  */
 void rcu_irq_enter(void)
 {
-        struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
-
-        if (rdtp->dynticks_nesting++)
-                return;
-        rdtp->dynticks++;
-        WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
-        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
+        rcu_exit_nohz();
 }
 
 /**
@@ -353,18 +457,7 @@ void rcu_irq_enter(void)
  */
 void rcu_irq_exit(void)
 {
-        struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
-
-        if (--rdtp->dynticks_nesting)
-                return;
-        smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
-        rdtp->dynticks++;
-        WARN_ON_ONCE(rdtp->dynticks & 0x1);
-
-        /* If the interrupt queued a callback, get out of dyntick mode. */
-        if (__get_cpu_var(rcu_sched_data).nxtlist ||
-            __get_cpu_var(rcu_bh_data).nxtlist)
-                set_need_resched();
+        rcu_enter_nohz();
 }
 
 #ifdef CONFIG_SMP
@@ -376,19 +469,8 @@ void rcu_irq_exit(void)
  */
 static int dyntick_save_progress_counter(struct rcu_data *rdp)
 {
-        int ret;
-        int snap;
-        int snap_nmi;
-
-        snap = rdp->dynticks->dynticks;
-        snap_nmi = rdp->dynticks->dynticks_nmi;
-        smp_mb();       /* Order sampling of snap with end of grace period. */
-        rdp->dynticks_snap = snap;
-        rdp->dynticks_nmi_snap = snap_nmi;
-        ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0);
-        if (ret)
-                rdp->dynticks_fqs++;
-        return ret;
+        rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
+        return 0;
 }
 
 /*
@@ -399,16 +481,11 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp)
  */
 static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 {
-        long curr;
-        long curr_nmi;
-        long snap;
-        long snap_nmi;
+        unsigned long curr;
+        unsigned long snap;
 
-        curr = rdp->dynticks->dynticks;
-        snap = rdp->dynticks_snap;
-        curr_nmi = rdp->dynticks->dynticks_nmi;
-        snap_nmi = rdp->dynticks_nmi_snap;
-        smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
+        curr = (unsigned long)atomic_add_return(0, &rdp->dynticks->dynticks);
+        snap = (unsigned long)rdp->dynticks_snap;
 
         /*
          * If the CPU passed through or entered a dynticks idle phase with
@@ -418,8 +495,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
          * read-side critical section that started before the beginning
          * of the current RCU grace period.
          */
-        if ((curr != snap || (curr & 0x1) == 0) &&
-            (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) {
+        if ((curr & 0x1) == 0 || ULONG_CMP_GE(curr, snap + 2)) {
                 rdp->dynticks_fqs++;
                 return 1;
         }
@@ -448,9 +524,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 
 #endif /* #else #ifdef CONFIG_NO_HZ */
 
-#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
-
-int rcu_cpu_stall_panicking __read_mostly;
+int rcu_cpu_stall_suppress __read_mostly;
 
 static void record_gp_stall_check_time(struct rcu_state *rsp)
 {
@@ -482,8 +556,11 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
         rcu_print_task_stall(rnp);
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
 
-        /* OK, time to rat on our buddy... */
-
+        /*
+         * OK, time to rat on our buddy...
+         * See Documentation/RCU/stallwarn.txt for info on how to debug
+         * RCU CPU stall warnings.
+         */
         printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {",
                rsp->name);
         rcu_for_each_leaf_node(rsp, rnp) {
@@ -512,6 +589,11 @@ static void print_cpu_stall(struct rcu_state *rsp)
         unsigned long flags;
         struct rcu_node *rnp = rcu_get_root(rsp);
 
+        /*
+         * OK, time to rat on ourselves...
+         * See Documentation/RCU/stallwarn.txt for info on how to debug
+         * RCU CPU stall warnings.
+         */
         printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n",
                rsp->name, smp_processor_id(), jiffies - rsp->gp_start);
         trigger_all_cpu_backtrace();
@@ -527,31 +609,50 @@ static void print_cpu_stall(struct rcu_state *rsp)
 
 static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
 {
-        long delta;
+        unsigned long j;
+        unsigned long js;
         struct rcu_node *rnp;
 
-        if (rcu_cpu_stall_panicking)
+        if (rcu_cpu_stall_suppress)
                 return;
-        delta = jiffies - rsp->jiffies_stall;
+        j = ACCESS_ONCE(jiffies);
+        js = ACCESS_ONCE(rsp->jiffies_stall);
         rnp = rdp->mynode;
-        if ((rnp->qsmask & rdp->grpmask) && delta >= 0) {
+        if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
 
                 /* We haven't checked in, so go dump stack. */
                 print_cpu_stall(rsp);
 
-        } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) {
+        } else if (rcu_gp_in_progress(rsp) &&
+                   ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
 
-                /* They had two time units to dump stack, so complain. */
+                /* They had a few time units to dump stack, so complain. */
                 print_other_cpu_stall(rsp);
         }
 }
 
 static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
 {
-        rcu_cpu_stall_panicking = 1;
+        rcu_cpu_stall_suppress = 1;
         return NOTIFY_DONE;
 }
 
+/**
+ * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
+ *
+ * Set the stall-warning timeout way off into the future, thus preventing
+ * any RCU CPU stall-warning messages from appearing in the current set of
+ * RCU grace periods.
+ *
+ * The caller must disable hard irqs.
+ */
+void rcu_cpu_stall_reset(void)
+{
+        rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2;
+        rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2;
+        rcu_preempt_stall_reset();
+}
+
 static struct notifier_block rcu_panic_block = {
         .notifier_call = rcu_panic,
 };
@@ -561,22 +662,6 @@ static void __init check_cpu_stall_init(void)
         atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
 }
 
-#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
-
-static void record_gp_stall_check_time(struct rcu_state *rsp)
-{
-}
-
-static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
-{
-}
-
-static void __init check_cpu_stall_init(void)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
-
 /*
  * Update CPU-local rcu_data state to record the newly noticed grace period.
  * This is used both when we started the grace period and when we notice
@@ -587,9 +672,17 @@ static void __init check_cpu_stall_init(void)
 static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
 {
         if (rdp->gpnum != rnp->gpnum) {
-                rdp->qs_pending = 1;
-                rdp->passed_quiesc = 0;
+                /*
+                 * If the current grace period is waiting for this CPU,
+                 * set up to detect a quiescent state, otherwise don't
+                 * go looking for one.
+                 */
                 rdp->gpnum = rnp->gpnum;
+                if (rnp->qsmask & rdp->grpmask) {
+                        rdp->qs_pending = 1;
+                        rdp->passed_quiesc = 0;
+                } else
+                        rdp->qs_pending = 0;
         }
 }
 
@@ -648,6 +741,24 @@ __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_dat
 
                 /* Remember that we saw this grace-period completion. */
                 rdp->completed = rnp->completed;
+
+                /*
+                 * If we were in an extended quiescent state, we may have
+                 * missed some grace periods that others CPUs handled on
+                 * our behalf. Catch up with this state to avoid noting
+                 * spurious new grace periods.  If another grace period
+                 * has started, then rnp->gpnum will have advanced, so
+                 * we will detect this later on.
+                 */
+                if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
+                        rdp->gpnum = rdp->completed;
+
+                /*
+                 * If RCU does not need a quiescent state from this CPU,
+                 * then make sure that this CPU doesn't go looking for one.
+                 */
+                if ((rnp->qsmask & rdp->grpmask) == 0)
+                        rdp->qs_pending = 0;
         }
 }
 
@@ -712,7 +823,7 @@ static void
 rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
         __releases(rcu_get_root(rsp)->lock)
 {
-        struct rcu_data *rdp = rsp->rda[smp_processor_id()];
+        struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
         struct rcu_node *rnp = rcu_get_root(rsp);
 
         if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) {
@@ -753,6 +864,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
                 rnp->completed = rsp->completed;
                 rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
                 rcu_start_gp_per_cpu(rsp, rnp, rdp);
+                rcu_preempt_boost_start_gp(rnp);
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 return;
         }
@@ -788,6 +900,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
                 rnp->completed = rsp->completed;
                 if (rnp == rdp->mynode)
                         rcu_start_gp_per_cpu(rsp, rnp, rdp);
+                rcu_preempt_boost_start_gp(rnp);
                 raw_spin_unlock(&rnp->lock);    /* irqs remain disabled. */
         }
 
@@ -808,7 +921,18 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
 static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
         __releases(rcu_get_root(rsp)->lock)
 {
+        unsigned long gp_duration;
+
         WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
+
+        /*
+         * Ensure that all grace-period and pre-grace-period activity
+         * is seen before the assignment to rsp->completed.
+         */
+        smp_mb(); /* See above block comment. */
+        gp_duration = jiffies - rsp->gp_start;
+        if (gp_duration > rsp->gp_max)
+                rsp->gp_max = gp_duration;
         rsp->completed = rsp->gpnum;
         rsp->signaled = RCU_GP_IDLE;
         rcu_start_gp(rsp, flags);  /* releases root node's rnp->lock. */
@@ -838,7 +962,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
                         return;
                 }
                 rnp->qsmask &= ~mask;
-                if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) {
+                if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
 
                         /* Other bits still set at this level, so done. */
                         raw_spin_unlock_irqrestore(&rnp->lock, flags);
@@ -951,65 +1075,49 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
 #ifdef CONFIG_HOTPLUG_CPU
 
 /*
- * Move a dying CPU's RCU callbacks to the ->orphan_cbs_list for the
- * specified flavor of RCU.  The callbacks will be adopted by the next
- * _rcu_barrier() invocation or by the CPU_DEAD notifier, whichever
- * comes first.  Because this is invoked from the CPU_DYING notifier,
- * irqs are already disabled.
+ * Move a dying CPU's RCU callbacks to online CPU's callback list.
+ * Synchronization is not required because this function executes
+ * in stop_machine() context.
  */
-static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp)
+static void rcu_send_cbs_to_online(struct rcu_state *rsp)
 {
         int i;
-        struct rcu_data *rdp = rsp->rda[smp_processor_id()];
+        /* current DYING CPU is cleared in the cpu_online_mask */
+        int receive_cpu = cpumask_any(cpu_online_mask);
+        struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
+        struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu);
 
         if (rdp->nxtlist == NULL)
                 return;  /* irqs disabled, so comparison is stable. */
-        raw_spin_lock(&rsp->onofflock);  /* irqs already disabled. */
-        *rsp->orphan_cbs_tail = rdp->nxtlist;
-        rsp->orphan_cbs_tail = rdp->nxttail[RCU_NEXT_TAIL];
+
+        *receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
+        receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+        receive_rdp->qlen += rdp->qlen;
+        receive_rdp->n_cbs_adopted += rdp->qlen;
+        rdp->n_cbs_orphaned += rdp->qlen;
+
         rdp->nxtlist = NULL;
         for (i = 0; i < RCU_NEXT_SIZE; i++)
                 rdp->nxttail[i] = &rdp->nxtlist;
-        rsp->orphan_qlen += rdp->qlen;
         rdp->qlen = 0;
-        raw_spin_unlock(&rsp->onofflock);  /* irqs remain disabled. */
-}
-
-/*
- * Adopt previously orphaned RCU callbacks.
- */
-static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
-{
-        unsigned long flags;
-        struct rcu_data *rdp;
-
-        raw_spin_lock_irqsave(&rsp->onofflock, flags);
-        rdp = rsp->rda[smp_processor_id()];
-        if (rsp->orphan_cbs_list == NULL) {
-                raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
-                return;
-        }
-        *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_list;
-        rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_tail;
-        rdp->qlen += rsp->orphan_qlen;
-        rsp->orphan_cbs_list = NULL;
-        rsp->orphan_cbs_tail = &rsp->orphan_cbs_list;
-        rsp->orphan_qlen = 0;
-        raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
 }
 
 /*
  * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy
  * and move all callbacks from the outgoing CPU to the current one.
+ * There can only be one CPU hotplug operation at a time, so no other
+ * CPU can be attempting to update rcu_cpu_kthread_task.
  */
 static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
 {
         unsigned long flags;
         unsigned long mask;
         int need_report = 0;
-        struct rcu_data *rdp = rsp->rda[cpu];
+        struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
         struct rcu_node *rnp;
 
+        rcu_stop_cpu_kthread(cpu);
+
         /* Exclude any attempts to start a new grace period. */
         raw_spin_lock_irqsave(&rsp->onofflock, flags);
 
@@ -1046,8 +1154,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
         if (need_report & RCU_OFL_TASKS_EXP_GP)
                 rcu_report_exp_rnp(rsp, rnp);
-
-        rcu_adopt_orphan_cbs(rsp);
+        rcu_node_kthread_setaffinity(rnp, -1);
 }
 
 /*
@@ -1065,11 +1172,7 @@ static void rcu_offline_cpu(int cpu)
 
 #else /* #ifdef CONFIG_HOTPLUG_CPU */
 
-static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp)
-{
-}
-
-static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
+static void rcu_send_cbs_to_online(struct rcu_state *rsp)
 {
 }
 
@@ -1113,7 +1216,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
                 next = list->next;
                 prefetch(next);
                 debug_rcu_head_unqueue(list);
-                list->func(list);
+                __rcu_reclaim(list);
                 list = next;
                 if (++count >= rdp->blimit)
                         break;
@@ -1123,6 +1226,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
 
         /* Update count, and requeue any remaining callbacks. */
         rdp->qlen -= count;
+        rdp->n_cbs_invoked += count;
         if (list != NULL) {
                 *tail = rdp->nxtlist;
                 rdp->nxtlist = list;
@@ -1148,7 +1252,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
 
         /* Re-raise the RCU softirq if there are callbacks remaining. */
         if (cpu_has_callbacks_ready_to_invoke(rdp))
-                raise_softirq(RCU_SOFTIRQ);
+                invoke_rcu_core();
 }
 
 /*
@@ -1194,7 +1298,7 @@ void rcu_check_callbacks(int cpu, int user)
         }
         rcu_preempt_check_callbacks(cpu);
         if (rcu_pending(cpu))
-                raise_softirq(RCU_SOFTIRQ);
+                invoke_rcu_core();
 }
 
 #ifdef CONFIG_SMP
@@ -1202,6 +1306,8 @@ void rcu_check_callbacks(int cpu, int user)
 /*
  * Scan the leaf rcu_node structures, processing dyntick state for any that
  * have not yet encountered a quiescent state, using the function specified.
+ * Also initiate boosting for any threads blocked on the root rcu_node.
+ *
  * The caller must have suppressed start of new grace periods.
  */
 static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
@@ -1220,13 +1326,14 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
                         return;
                 }
                 if (rnp->qsmask == 0) {
-                        raw_spin_unlock_irqrestore(&rnp->lock, flags);
+                        rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
                         continue;
                 }
                 cpu = rnp->grplo;
                 bit = 1;
                 for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
-                        if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))
+                        if ((rnp->qsmask & bit) != 0 &&
+                            f(per_cpu_ptr(rsp->rda, cpu)))
                                 mask |= bit;
                 }
                 if (mask != 0) {
@@ -1237,6 +1344,11 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
                 }
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
         }
+        rnp = rcu_get_root(rsp);
+        if (rnp->qsmask == 0) {
+                raw_spin_lock_irqsave(&rnp->lock, flags);
+                rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
+        }
 }
 
 /*
@@ -1351,7 +1463,8 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
         }
 
         /* If there are callbacks ready, invoke them. */
-        rcu_do_batch(rsp, rdp);
+        if (cpu_has_callbacks_ready_to_invoke(rdp))
+                invoke_rcu_callbacks(rsp, rdp);
 }
 
 /*
@@ -1359,29 +1472,37 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
  */
 static void rcu_process_callbacks(struct softirq_action *unused)
 {
-        /*
-         * Memory references from any prior RCU read-side critical sections
-         * executed by the interrupted code must be seen before any RCU
-         * grace-period manipulations below.
-         */
-        smp_mb(); /* See above block comment. */
-
         __rcu_process_callbacks(&rcu_sched_state,
                                 &__get_cpu_var(rcu_sched_data));
         __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
         rcu_preempt_process_callbacks();
 
-        /*
-         * Memory references from any later RCU read-side critical sections
-         * executed by the interrupted code must be seen after any RCU
-         * grace-period manipulations above.
-         */
-        smp_mb(); /* See above block comment. */
-
         /* If we are last CPU on way to dyntick-idle mode, accelerate it. */
         rcu_needs_cpu_flush();
 }
 
+/*
+ * Wake up the current CPU's kthread.  This replaces raise_softirq()
+ * in earlier versions of RCU.  Note that because we are running on
+ * the current CPU with interrupts disabled, the rcu_cpu_kthread_task
+ * cannot disappear out from under us.
+ */
+static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+        if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
+                return;
+        if (likely(!rsp->boost)) {
+                rcu_do_batch(rsp, rdp);
+                return;
+        }
+        invoke_rcu_callbacks_kthread();
+}
+
+static void invoke_rcu_core(void)
+{
+        raise_softirq(RCU_SOFTIRQ);
+}
+
 static void
 __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
            struct rcu_state *rsp)
@@ -1402,21 +1523,17 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
          * a quiescent state betweentimes.
          */
         local_irq_save(flags);
-        rdp = rsp->rda[smp_processor_id()];
-        rcu_process_gp_end(rsp, rdp);
-        check_for_new_grace_period(rsp, rdp);
+        rdp = this_cpu_ptr(rsp->rda);
 
         /* Add the callback to our list. */
         *rdp->nxttail[RCU_NEXT_TAIL] = head;
         rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
+        rdp->qlen++;
 
-        /* Start a new grace period if one not already started. */
-        if (!rcu_gp_in_progress(rsp)) {
-                unsigned long nestflag;
-                struct rcu_node *rnp_root = rcu_get_root(rsp);
-
-                raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
-                rcu_start_gp(rsp, nestflag);  /* releases rnp_root->lock. */
+        /* If interrupts were disabled, don't dive into RCU core. */
+        if (irqs_disabled_flags(flags)) {
+                local_irq_restore(flags);
+                return;
         }
 
         /*
@@ -1426,13 +1543,28 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
          * invoking force_quiescent_state() if the newly enqueued callback
          * is the only one waiting for a grace period to complete.
          */
-        if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
-                rdp->blimit = LONG_MAX;
-                if (rsp->n_force_qs == rdp->n_force_qs_snap &&
-                    *rdp->nxttail[RCU_DONE_TAIL] != head)
-                        force_quiescent_state(rsp, 0);
-                rdp->n_force_qs_snap = rsp->n_force_qs;
-                rdp->qlen_last_fqs_check = rdp->qlen;
+        if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
+
+                /* Are we ignoring a completed grace period? */
+                rcu_process_gp_end(rsp, rdp);
+                check_for_new_grace_period(rsp, rdp);
+
+                /* Start a new grace period if one not already started. */
+                if (!rcu_gp_in_progress(rsp)) {
+                        unsigned long nestflag;
+                        struct rcu_node *rnp_root = rcu_get_root(rsp);
+
+                        raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
+                        rcu_start_gp(rsp, nestflag);  /* rlses rnp_root->lock */
+                } else {
+                        /* Give the grace period a kick. */
+                        rdp->blimit = LONG_MAX;
+                        if (rsp->n_force_qs == rdp->n_force_qs_snap &&
+                            *rdp->nxttail[RCU_DONE_TAIL] != head)
+                                force_quiescent_state(rsp, 0);
+                        rdp->n_force_qs_snap = rsp->n_force_qs;
+                        rdp->qlen_last_fqs_check = rdp->qlen;
+                }
         } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
                 force_quiescent_state(rsp, 1);
         local_irq_restore(flags);
@@ -1547,7 +1679,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
                  * or RCU-bh, force a local reschedule.
                  */
                 rdp->n_rp_qs_pending++;
-                if (!rdp->preemptable &&
+                if (!rdp->preemptible &&
                     ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
                                  jiffies))
                         set_need_resched();
@@ -1662,13 +1794,12 @@ static void _rcu_barrier(struct rcu_state *rsp,
          * decrement rcu_barrier_cpu_count -- otherwise the first CPU
          * might complete its grace period before all of the other CPUs
          * did their increment, causing this function to return too
-         * early.
+         * early.  Note that on_each_cpu() disables irqs, which prevents
+         * any CPUs from coming online or going offline until each online
+         * CPU has queued its RCU-barrier callback.
          */
         atomic_set(&rcu_barrier_cpu_count, 1);
-        preempt_disable(); /* stop CPU_DYING from filling orphan_cbs_list */
-        rcu_adopt_orphan_cbs(rsp);
         on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1);
-        preempt_enable(); /* CPU_DYING can again fill orphan_cbs_list */
         if (atomic_dec_and_test(&rcu_barrier_cpu_count))
                 complete(&rcu_barrier_completion);
         wait_for_completion(&rcu_barrier_completion);
@@ -1701,7 +1832,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
 {
         unsigned long flags;
         int i;
-        struct rcu_data *rdp = rsp->rda[cpu];
+        struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
         struct rcu_node *rnp = rcu_get_root(rsp);
 
         /* Set up local state, ensuring consistent view of global state. */
@@ -1725,11 +1856,11 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
  * that this CPU cannot possibly have any RCU callbacks in flight yet.
  */
 static void __cpuinit
-rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
+rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
 {
         unsigned long flags;
         unsigned long mask;
-        struct rcu_data *rdp = rsp->rda[cpu];
+        struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
         struct rcu_node *rnp = rcu_get_root(rsp);
 
         /* Set up local state, ensuring consistent view of global state. */
@@ -1737,7 +1868,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
         rdp->passed_quiesc = 0;  /* We could be racing with new GP, */
         rdp->qs_pending = 1;     /*  so set up to respond to current GP. */
         rdp->beenonline = 1;     /* We have now been online. */
-        rdp->preemptable = preemptable;
+        rdp->preemptible = preemptible;
         rdp->qlen_last_fqs_check = 0;
         rdp->n_force_qs_snap = rsp->n_force_qs;
         rdp->blimit = blimit;
@@ -1771,7 +1902,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
         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);
@@ -1785,27 +1916,34 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
                                     unsigned long action, void *hcpu)
 {
         long cpu = (long)hcpu;
+        struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
+        struct rcu_node *rnp = rdp->mynode;
 
         switch (action) {
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
-                rcu_online_cpu(cpu);
+                rcu_prepare_cpu(cpu);
+                rcu_prepare_kthreads(cpu);
+                break;
+        case CPU_ONLINE:
+        case CPU_DOWN_FAILED:
+                rcu_node_kthread_setaffinity(rnp, -1);
+                rcu_cpu_kthread_setrt(cpu, 1);
+                break;
+        case CPU_DOWN_PREPARE:
+                rcu_node_kthread_setaffinity(rnp, cpu);
+                rcu_cpu_kthread_setrt(cpu, 0);
                 break;
         case CPU_DYING:
         case CPU_DYING_FROZEN:
                 /*
-                 * preempt_disable() in _rcu_barrier() prevents stop_machine(),
-                 * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);"
-                 * returns, all online cpus have queued rcu_barrier_func().
-                 * The dying CPU clears its cpu_online_mask bit and
-                 * moves all of its RCU callbacks to ->orphan_cbs_list
-                 * in the context of stop_machine(), so subsequent calls
-                 * to _rcu_barrier() will adopt these callbacks and only
-                 * then queue rcu_barrier_func() on all remaining CPUs.
+                 * The whole machine is "stopped" except this CPU, so we can
+                 * touch any data without introducing corruption. We send the
+                 * dying CPU's callbacks to an arbitrarily chosen online CPU.
                  */
-                rcu_send_cbs_to_orphanage(&rcu_bh_state);
-                rcu_send_cbs_to_orphanage(&rcu_sched_state);
-                rcu_preempt_send_cbs_to_orphanage();
+                rcu_send_cbs_to_online(&rcu_bh_state);
+                rcu_send_cbs_to_online(&rcu_sched_state);
+                rcu_preempt_send_cbs_to_online();
                 break;
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
@@ -1843,8 +1981,9 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp)
 {
         int i;
 
-        for (i = NUM_RCU_LVLS - 1; i >= 0; i--)
+        for (i = NUM_RCU_LVLS - 1; i > 0; i--)
                 rsp->levelspread[i] = CONFIG_RCU_FANOUT;
+        rsp->levelspread[0] = RCU_FANOUT_LEAF;
 }
 #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
 static void __init rcu_init_levelspread(struct rcu_state *rsp)
@@ -1865,7 +2004,8 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp)
 /*
  * Helper function for rcu_init() that initializes one rcu_state structure.
  */
-static void __init rcu_init_one(struct rcu_state *rsp)
+static void __init rcu_init_one(struct rcu_state *rsp,
+                struct rcu_data __percpu *rda)
 {
         static char *buf[] = { "rcu_node_level_0",
                                "rcu_node_level_1",
@@ -1911,46 +2051,29 @@ static void __init rcu_init_one(struct rcu_state *rsp)
                                               j / rsp->levelspread[i - 1];
                         }
                         rnp->level = i;
-                        INIT_LIST_HEAD(&rnp->blocked_tasks[0]);
-                        INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
-                        INIT_LIST_HEAD(&rnp->blocked_tasks[2]);
-                        INIT_LIST_HEAD(&rnp->blocked_tasks[3]);
+                        INIT_LIST_HEAD(&rnp->blkd_tasks);
                 }
         }
 
+        rsp->rda = rda;
         rnp = rsp->level[NUM_RCU_LVLS - 1];
         for_each_possible_cpu(i) {
                 while (i > rnp->grphi)
                         rnp++;
-                rsp->rda[i]->mynode = rnp;
+                per_cpu_ptr(rsp->rda, i)->mynode = rnp;
                 rcu_boot_init_percpu_data(i, rsp);
         }
 }
 
-/*
- * Helper macro for __rcu_init() and __rcu_init_preempt().  To be used
- * nowhere else!  Assigns leaf node pointers into each CPU's rcu_data
- * structure.
- */
-#define RCU_INIT_FLAVOR(rsp, rcu_data) \
-do { \
-        int i; \
-        \
-        for_each_possible_cpu(i) { \
-                (rsp)->rda[i] = &per_cpu(rcu_data, i); \
-        } \
-        rcu_init_one(rsp); \
-} while (0)
-
 void __init rcu_init(void)
 {
         int cpu;
 
         rcu_bootup_announce();
-        RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data);
-        RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data);
+        rcu_init_one(&rcu_sched_state, &rcu_sched_data);
+        rcu_init_one(&rcu_bh_state, &rcu_bh_data);
         __rcu_init_preempt();
-        open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+         open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
 
         /*
          * We don't need protection against CPU-hotplug here because