1 files changed, 298 insertions, 187 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 6b11b07cfe7f..f3077c0ab181 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -25,7 +25,7 @@
  * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
  *
  * For detailed explanation of Read-Copy Update mechanism see -
- *      Documentation/RCU
+ *      Documentation/RCU
  */
 #include <linux/types.h>
 #include <linux/kernel.h>
@@ -49,13 +49,6 @@
 
 #include "rcutree.h"
 
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-static struct lock_class_key rcu_lock_key;
-struct lockdep_map rcu_lock_map =
-        STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
-EXPORT_SYMBOL_GPL(rcu_lock_map);
-#endif
-
 /* Data structures. */
 
 #define RCU_STATE_INITIALIZER(name) { \
@@ -66,10 +59,13 @@ EXPORT_SYMBOL_GPL(rcu_lock_map);
                 NUM_RCU_LVL_2, \
                 NUM_RCU_LVL_3, /* == MAX_RCU_LVLS */ \
         }, \
-        .signaled = RCU_SIGNAL_INIT, \
+        .signaled = RCU_GP_IDLE, \
         .gpnum = -300, \
         .completed = -300, \
         .onofflock = __SPIN_LOCK_UNLOCKED(&name.onofflock), \
+        .orphan_cbs_list = NULL, \
+        .orphan_cbs_tail = &name.orphan_cbs_list, \
+        .orphan_qlen = 0, \
         .fqslock = __SPIN_LOCK_UNLOCKED(&name.fqslock), \
         .n_force_qs = 0, \
         .n_force_qs_ngp = 0, \
@@ -81,24 +77,16 @@ 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);
 
-extern long rcu_batches_completed_sched(void);
-static struct rcu_node *rcu_get_root(struct rcu_state *rsp);
-static void cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp,
-                          struct rcu_node *rnp, unsigned long flags);
-static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags);
-#ifdef CONFIG_HOTPLUG_CPU
-static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp);
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-static void __rcu_process_callbacks(struct rcu_state *rsp,
-                                    struct rcu_data *rdp);
-static void __call_rcu(struct rcu_head *head,
-                       void (*func)(struct rcu_head *rcu),
-                       struct rcu_state *rsp);
-static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp);
-static void __cpuinit rcu_init_percpu_data(int cpu, struct rcu_state *rsp,
-                                           int preemptable);
 
-#include "rcutree_plugin.h"
+/*
+ * 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.
+ */
+static int rcu_gp_in_progress(struct rcu_state *rsp)
+{
+        return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum);
+}
 
 /*
  * Note a quiescent state.  Because we do not need to know
@@ -107,27 +95,23 @@ static void __cpuinit rcu_init_percpu_data(int cpu, struct rcu_state *rsp,
  */
 void rcu_sched_qs(int cpu)
 {
-        unsigned long flags;
         struct rcu_data *rdp;
 
-        local_irq_save(flags);
         rdp = &per_cpu(rcu_sched_data, cpu);
-        rdp->passed_quiesc = 1;
         rdp->passed_quiesc_completed = rdp->completed;
-        rcu_preempt_qs(cpu);
-        local_irq_restore(flags);
+        barrier();
+        rdp->passed_quiesc = 1;
+        rcu_preempt_note_context_switch(cpu);
 }
 
 void rcu_bh_qs(int cpu)
 {
-        unsigned long flags;
         struct rcu_data *rdp;
 
-        local_irq_save(flags);
         rdp = &per_cpu(rcu_bh_data, cpu);
-        rdp->passed_quiesc = 1;
         rdp->passed_quiesc_completed = rdp->completed;
-        local_irq_restore(flags);
+        barrier();
+        rdp->passed_quiesc = 1;
 }
 
 #ifdef CONFIG_NO_HZ
@@ -141,6 +125,10 @@ static int blimit = 10;		/* Maximum callbacks per softirq. */
 static int qhimark = 10000;     /* If this many pending, ignore blimit. */
 static int qlowmark = 100;      /* Once only this many pending, use blimit. */
 
+module_param(blimit, int, 0);
+module_param(qhimark, int, 0);
+module_param(qlowmark, int, 0);
+
 static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
 static int rcu_pending(int cpu);
 
@@ -177,9 +165,7 @@ cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
 static int
 cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
 {
-        /* ACCESS_ONCE() because we are accessing outside of lock. */
-        return *rdp->nxttail[RCU_DONE_TAIL] &&
-               ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum);
+        return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp);
 }
 
 /*
@@ -373,7 +359,7 @@ static long dyntick_recall_completed(struct rcu_state *rsp)
 /*
  * Snapshot the specified CPU's dynticks counter so that we can later
  * credit them with an implicit quiescent state.  Return 1 if this CPU
- * is already in a quiescent state courtesy of dynticks idle mode.
+ * is in dynticks idle mode, which is an extended quiescent state.
  */
 static int dyntick_save_progress_counter(struct rcu_data *rdp)
 {
@@ -479,30 +465,34 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
         long delta;
         unsigned long flags;
         struct rcu_node *rnp = rcu_get_root(rsp);
-        struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1];
-        struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES];
 
         /* Only let one CPU complain about others per time interval. */
 
         spin_lock_irqsave(&rnp->lock, flags);
         delta = jiffies - rsp->jiffies_stall;
-        if (delta < RCU_STALL_RAT_DELAY || rsp->gpnum == rsp->completed) {
+        if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
                 spin_unlock_irqrestore(&rnp->lock, flags);
                 return;
         }
         rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
+
+        /*
+         * Now rat on any tasks that got kicked up to the root rcu_node
+         * due to CPU offlining.
+         */
+        rcu_print_task_stall(rnp);
         spin_unlock_irqrestore(&rnp->lock, flags);
 
         /* OK, time to rat on our buddy... */
 
         printk(KERN_ERR "INFO: RCU detected CPU stalls:");
-        for (; rnp_cur < rnp_end; rnp_cur++) {
+        rcu_for_each_leaf_node(rsp, rnp) {
                 rcu_print_task_stall(rnp);
-                if (rnp_cur->qsmask == 0)
+                if (rnp->qsmask == 0)
                         continue;
-                for (cpu = 0; cpu <= rnp_cur->grphi - rnp_cur->grplo; cpu++)
-                        if (rnp_cur->qsmask & (1UL << cpu))
-                                printk(" %d", rnp_cur->grplo + cpu);
+                for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
+                        if (rnp->qsmask & (1UL << cpu))
+                                printk(" %d", rnp->grplo + cpu);
         }
         printk(" (detected by %d, t=%ld jiffies)\n",
                smp_processor_id(), (long)(jiffies - rsp->gp_start));
@@ -541,8 +531,7 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
                 /* We haven't checked in, so go dump stack. */
                 print_cpu_stall(rsp);
 
-        } else if (rsp->gpnum != rsp->completed &&
-                   delta >= RCU_STALL_RAT_DELAY) {
+        } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) {
 
                 /* They had two time units to dump stack, so complain. */
                 print_other_cpu_stall(rsp);
@@ -605,8 +594,6 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
 {
         struct rcu_data *rdp = rsp->rda[smp_processor_id()];
         struct rcu_node *rnp = rcu_get_root(rsp);
-        struct rcu_node *rnp_cur;
-        struct rcu_node *rnp_end;
 
         if (!cpu_needs_another_gp(rsp, rdp)) {
                 spin_unlock_irqrestore(&rnp->lock, flags);
@@ -615,6 +602,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
 
         /* Advance to a new grace period and initialize state. */
         rsp->gpnum++;
+        WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT);
         rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
         rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
         record_gp_stall_check_time(rsp);
@@ -622,16 +610,24 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
         note_new_gpnum(rsp, rdp);
 
         /*
-         * Because we are first, we know that all our callbacks will
-         * be covered by this upcoming grace period, even the ones
-         * that were registered arbitrarily recently.
+         * Because this CPU just now started the new grace period, we know
+         * that all of its callbacks will be covered by this upcoming grace
+         * period, even the ones that were registered arbitrarily recently.
+         * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
+         *
+         * Other CPUs cannot be sure exactly when the grace period started.
+         * Therefore, their recently registered callbacks must pass through
+         * an additional RCU_NEXT_READY stage, so that they will be handled
+         * by the next RCU grace period.
          */
         rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
         rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
 
         /* Special-case the common single-level case. */
         if (NUM_RCU_NODES == 1) {
+                rcu_preempt_check_blocked_tasks(rnp);
                 rnp->qsmask = rnp->qsmaskinit;
+                rnp->gpnum = rsp->gpnum;
                 rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
                 spin_unlock_irqrestore(&rnp->lock, flags);
                 return;
@@ -644,45 +640,34 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
         spin_lock(&rsp->onofflock);  /* irqs already disabled. */
 
         /*
-         * Set the quiescent-state-needed bits in all the non-leaf RCU
-         * nodes for all currently online CPUs.  This operation relies
-         * on the layout of the hierarchy within the rsp->node[] array.
-         * Note that other CPUs will access only the leaves of the
-         * hierarchy, which still indicate that no grace period is in
-         * progress.  In addition, we have excluded CPU-hotplug operations.
-         *
-         * We therefore do not need to hold any locks.  Any required
-         * memory barriers will be supplied by the locks guarding the
-         * leaf rcu_nodes in the hierarchy.
-         */
-
-        rnp_end = rsp->level[NUM_RCU_LVLS - 1];
-        for (rnp_cur = &rsp->node[0]; rnp_cur < rnp_end; rnp_cur++)
-                rnp_cur->qsmask = rnp_cur->qsmaskinit;
-
-        /*
-         * Now set up the leaf nodes.  Here we must be careful.  First,
-         * we need to hold the lock in order to exclude other CPUs, which
-         * might be contending for the leaf nodes' locks.  Second, as
-         * soon as we initialize a given leaf node, its CPUs might run
-         * up the rest of the hierarchy.  We must therefore acquire locks
-         * for each node that we touch during this stage.  (But we still
-         * are excluding CPU-hotplug operations.)
+         * Set the quiescent-state-needed bits in all the rcu_node
+         * structures for all currently online CPUs in breadth-first
+         * order, starting from the root rcu_node structure.  This
+         * operation relies on the layout of the hierarchy within the
+         * rsp->node[] array.  Note that other CPUs will access only
+         * the leaves of the hierarchy, which still indicate that no
+         * grace period is in progress, at least until the corresponding
+         * leaf node has been initialized.  In addition, we have excluded
+         * CPU-hotplug operations.
          *
          * Note that the grace period cannot complete until we finish
          * the initialization process, as there will be at least one
          * qsmask bit set in the root node until that time, namely the
-         * one corresponding to this CPU.
+         * one corresponding to this CPU, due to the fact that we have
+         * irqs disabled.
          */
-        rnp_end = &rsp->node[NUM_RCU_NODES];
-        rnp_cur = rsp->level[NUM_RCU_LVLS - 1];
-        for (; rnp_cur < rnp_end; rnp_cur++) {
-                spin_lock(&rnp_cur->lock);      /* irqs already disabled. */
-                rnp_cur->qsmask = rnp_cur->qsmaskinit;
-                spin_unlock(&rnp_cur->lock);    /* irqs already disabled. */
+        rcu_for_each_node_breadth_first(rsp, rnp) {
+                spin_lock(&rnp->lock);          /* irqs already disabled. */
+                rcu_preempt_check_blocked_tasks(rnp);
+                rnp->qsmask = rnp->qsmaskinit;
+                rnp->gpnum = rsp->gpnum;
+                spin_unlock(&rnp->lock);        /* irqs remain disabled. */
         }
 
+        rnp = rcu_get_root(rsp);
+        spin_lock(&rnp->lock);                  /* irqs already disabled. */
         rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
+        spin_unlock(&rnp->lock);                /* irqs remain disabled. */
         spin_unlock_irqrestore(&rsp->onofflock, flags);
 }
 
@@ -720,9 +705,11 @@ rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
  * hold rnp->lock, as required by rcu_start_gp(), which will release it.
  */
 static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags)
-        __releases(rnp->lock)
+        __releases(rcu_get_root(rsp)->lock)
 {
+        WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
         rsp->completed = rsp->gpnum;
+        rsp->signaled = RCU_GP_IDLE;
         rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]);
         rcu_start_gp(rsp, flags);  /* releases root node's rnp->lock. */
 }
@@ -739,6 +726,8 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
               unsigned long flags)
         __releases(rnp->lock)
 {
+        struct rcu_node *rnp_c;
+
         /* Walk up the rcu_node hierarchy. */
         for (;;) {
                 if (!(rnp->qsmask & mask)) {
@@ -762,8 +751,10 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
                         break;
                 }
                 spin_unlock_irqrestore(&rnp->lock, flags);
+                rnp_c = rnp;
                 rnp = rnp->parent;
                 spin_lock_irqsave(&rnp->lock, flags);
+                WARN_ON_ONCE(rnp_c->qsmask);
         }
 
         /*
@@ -776,10 +767,10 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
 
 /*
  * Record a quiescent state for the specified CPU, which must either be
- * the current CPU or an offline CPU.  The lastcomp argument is used to
- * make sure we are still in the grace period of interest.  We don't want
- * to end the current grace period based on quiescent states detected in
- * an earlier grace period!
+ * the current CPU.  The lastcomp argument is used to make sure we are
+ * still in the grace period of interest.  We don't want to end the current
+ * grace period based on quiescent states detected in an earlier grace
+ * period!
  */
 static void
 cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
@@ -814,7 +805,6 @@ cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
                  * This GP can't end until cpu checks in, so all of our
                  * callbacks can be processed during the next GP.
                  */
-                rdp = rsp->rda[smp_processor_id()];
                 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
 
                 cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */
@@ -855,24 +845,70 @@ 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.
+ */
+static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp)
+{
+        int i;
+        struct rcu_data *rdp = rsp->rda[smp_processor_id()];
+
+        if (rdp->nxtlist == NULL)
+                return;  /* irqs disabled, so comparison is stable. */
+        spin_lock(&rsp->onofflock);  /* irqs already disabled. */
+        *rsp->orphan_cbs_tail = rdp->nxtlist;
+        rsp->orphan_cbs_tail = rdp->nxttail[RCU_NEXT_TAIL];
+        rdp->nxtlist = NULL;
+        for (i = 0; i < RCU_NEXT_SIZE; i++)
+                rdp->nxttail[i] = &rdp->nxtlist;
+        rsp->orphan_qlen += rdp->qlen;
+        rdp->qlen = 0;
+        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;
+
+        spin_lock_irqsave(&rsp->onofflock, flags);
+        rdp = rsp->rda[smp_processor_id()];
+        if (rsp->orphan_cbs_list == NULL) {
+                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;
+        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.
  */
 static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
 {
-        int i;
         unsigned long flags;
         long lastcomp;
         unsigned long mask;
         struct rcu_data *rdp = rsp->rda[cpu];
-        struct rcu_data *rdp_me;
         struct rcu_node *rnp;
 
         /* Exclude any attempts to start a new grace period. */
         spin_lock_irqsave(&rsp->onofflock, flags);
 
         /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
-        rnp = rdp->mynode;
+        rnp = rdp->mynode;      /* this is the outgoing CPU's rnp. */
         mask = rdp->grpmask;    /* rnp->grplo is constant. */
         do {
                 spin_lock(&rnp->lock);          /* irqs already disabled. */
@@ -881,42 +917,29 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
                         spin_unlock(&rnp->lock); /* irqs remain disabled. */
                         break;
                 }
-                rcu_preempt_offline_tasks(rsp, rnp);
+
+                /*
+                 * If there was a task blocking the current grace period,
+                 * and if all CPUs have checked in, we need to propagate
+                 * the quiescent state up the rcu_node hierarchy.  But that
+                 * is inconvenient at the moment due to deadlock issues if
+                 * this should end the current grace period.  So set the
+                 * offlined CPU's bit in ->qsmask in order to force the
+                 * next force_quiescent_state() invocation to clean up this
+                 * mess in a deadlock-free manner.
+                 */
+                if (rcu_preempt_offline_tasks(rsp, rnp, rdp) && !rnp->qsmask)
+                        rnp->qsmask |= mask;
+
                 mask = rnp->grpmask;
                 spin_unlock(&rnp->lock);        /* irqs remain disabled. */
                 rnp = rnp->parent;
         } while (rnp != NULL);
         lastcomp = rsp->completed;
 
-        spin_unlock(&rsp->onofflock);           /* irqs remain disabled. */
-
-        /* Being offline is a quiescent state, so go record it. */
-        cpu_quiet(cpu, rsp, rdp, lastcomp);
+        spin_unlock_irqrestore(&rsp->onofflock, flags);
 
-        /*
-         * Move callbacks from the outgoing CPU to the running CPU.
-         * Note that the outgoing CPU is now quiscent, so it is now
-         * (uncharacteristically) safe to access its rcu_data structure.
-         * Note also that we must carefully retain the order of the
-         * outgoing CPU's callbacks in order for rcu_barrier() to work
-         * correctly.  Finally, note that we start all the callbacks
-         * afresh, even those that have passed through a grace period
-         * and are therefore ready to invoke.  The theory is that hotplug
-         * events are rare, and that if they are frequent enough to
-         * indefinitely delay callbacks, you have far worse things to
-         * be worrying about.
-         */
-        rdp_me = rsp->rda[smp_processor_id()];
-        if (rdp->nxtlist != NULL) {
-                *rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
-                rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
-                rdp->nxtlist = NULL;
-                for (i = 0; i < RCU_NEXT_SIZE; i++)
-                        rdp->nxttail[i] = &rdp->nxtlist;
-                rdp_me->qlen += rdp->qlen;
-                rdp->qlen = 0;
-        }
-        local_irq_restore(flags);
+        rcu_adopt_orphan_cbs(rsp);
 }
 
 /*
@@ -934,6 +957,14 @@ 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_offline_cpu(int cpu)
 {
 }
@@ -944,7 +975,7 @@ static void rcu_offline_cpu(int cpu)
  * Invoke any RCU callbacks that have made it to the end of their grace
  * period.  Thottle as specified by rdp->blimit.
  */
-static void rcu_do_batch(struct rcu_data *rdp)
+static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
 {
         unsigned long flags;
         struct rcu_head *next, *list, **tail;
@@ -997,6 +1028,13 @@ static void rcu_do_batch(struct rcu_data *rdp)
         if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
                 rdp->blimit = blimit;
 
+        /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
+        if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
+                rdp->qlen_last_fqs_check = 0;
+                rdp->n_force_qs_snap = rsp->n_force_qs;
+        } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
+                rdp->qlen_last_fqs_check = rdp->qlen;
+
         local_irq_restore(flags);
 
         /* Re-raise the RCU softirq if there are callbacks remaining. */
@@ -1066,33 +1104,32 @@ static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp,
         int cpu;
         unsigned long flags;
         unsigned long mask;
-        struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1];
-        struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES];
+        struct rcu_node *rnp;
 
-        for (; rnp_cur < rnp_end; rnp_cur++) {
+        rcu_for_each_leaf_node(rsp, rnp) {
                 mask = 0;
-                spin_lock_irqsave(&rnp_cur->lock, flags);
+                spin_lock_irqsave(&rnp->lock, flags);
                 if (rsp->completed != lastcomp) {
-                        spin_unlock_irqrestore(&rnp_cur->lock, flags);
+                        spin_unlock_irqrestore(&rnp->lock, flags);
                         return 1;
                 }
-                if (rnp_cur->qsmask == 0) {
-                        spin_unlock_irqrestore(&rnp_cur->lock, flags);
+                if (rnp->qsmask == 0) {
+                        spin_unlock_irqrestore(&rnp->lock, flags);
                         continue;
                 }
-                cpu = rnp_cur->grplo;
+                cpu = rnp->grplo;
                 bit = 1;
-                for (; cpu <= rnp_cur->grphi; cpu++, bit <<= 1) {
-                        if ((rnp_cur->qsmask & bit) != 0 && f(rsp->rda[cpu]))
+                for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
+                        if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))
                                 mask |= bit;
                 }
                 if (mask != 0 && rsp->completed == lastcomp) {
 
-                        /* cpu_quiet_msk() releases rnp_cur->lock. */
-                        cpu_quiet_msk(mask, rsp, rnp_cur, flags);
+                        /* cpu_quiet_msk() releases rnp->lock. */
+                        cpu_quiet_msk(mask, rsp, rnp, flags);
                         continue;
                 }
-                spin_unlock_irqrestore(&rnp_cur->lock, flags);
+                spin_unlock_irqrestore(&rnp->lock, flags);
         }
         return 0;
 }
@@ -1108,7 +1145,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
         struct rcu_node *rnp = rcu_get_root(rsp);
         u8 signaled;
 
-        if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum))
+        if (!rcu_gp_in_progress(rsp))
                 return;  /* No grace period in progress, nothing to force. */
         if (!spin_trylock_irqsave(&rsp->fqslock, flags)) {
                 rsp->n_force_qs_lh++; /* Inexact, can lose counts.  Tough! */
@@ -1129,9 +1166,10 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
         }
         spin_unlock(&rnp->lock);
         switch (signaled) {
+        case RCU_GP_IDLE:
         case RCU_GP_INIT:
 
-                break; /* grace period still initializing, ignore. */
+                break; /* grace period idle or initializing, ignore. */
 
         case RCU_SAVE_DYNTICK:
 
@@ -1145,7 +1183,8 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
 
                 /* Update state, record completion counter. */
                 spin_lock(&rnp->lock);
-                if (lastcomp == rsp->completed) {
+                if (lastcomp == rsp->completed &&
+                    rsp->signaled == RCU_SAVE_DYNTICK) {
                         rsp->signaled = RCU_FORCE_QS;
                         dyntick_record_completed(rsp, lastcomp);
                 }
@@ -1211,7 +1250,7 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
         }
 
         /* If there are callbacks ready, invoke them. */
-        rcu_do_batch(rdp);
+        rcu_do_batch(rsp, rdp);
 }
 
 /*
@@ -1267,7 +1306,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
         rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
 
         /* Start a new grace period if one not already started. */
-        if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum)) {
+        if (!rcu_gp_in_progress(rsp)) {
                 unsigned long nestflag;
                 struct rcu_node *rnp_root = rcu_get_root(rsp);
 
@@ -1275,10 +1314,20 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
                 rcu_start_gp(rsp, nestflag);  /* releases rnp_root->lock. */
         }
 
-        /* Force the grace period if too many callbacks or too long waiting. */
-        if (unlikely(++rdp->qlen > qhimark)) {
+        /*
+         * Force the grace period if too many callbacks or too long waiting.
+         * Enforce hysteresis, and don't invoke force_quiescent_state()
+         * if some other CPU has recently done so.  Also, don't bother
+         * 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;
-                force_quiescent_state(rsp, 0);
+                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 ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)
                 force_quiescent_state(rsp, 1);
         local_irq_restore(flags);
@@ -1347,7 +1396,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
         }
 
         /* Has an RCU GP gone long enough to send resched IPIs &c? */
-        if (ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum) &&
+        if (rcu_gp_in_progress(rsp) &&
             ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) {
                 rdp->n_rp_need_fqs++;
                 return 1;
@@ -1384,6 +1433,82 @@ int rcu_needs_cpu(int cpu)
                rcu_preempt_needs_cpu(cpu);
 }
 
+static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
+static atomic_t rcu_barrier_cpu_count;
+static DEFINE_MUTEX(rcu_barrier_mutex);
+static struct completion rcu_barrier_completion;
+
+static void rcu_barrier_callback(struct rcu_head *notused)
+{
+        if (atomic_dec_and_test(&rcu_barrier_cpu_count))
+                complete(&rcu_barrier_completion);
+}
+
+/*
+ * Called with preemption disabled, and from cross-cpu IRQ context.
+ */
+static void rcu_barrier_func(void *type)
+{
+        int cpu = smp_processor_id();
+        struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
+        void (*call_rcu_func)(struct rcu_head *head,
+                              void (*func)(struct rcu_head *head));
+
+        atomic_inc(&rcu_barrier_cpu_count);
+        call_rcu_func = type;
+        call_rcu_func(head, rcu_barrier_callback);
+}
+
+/*
+ * Orchestrate the specified type of RCU barrier, waiting for all
+ * RCU callbacks of the specified type to complete.
+ */
+static void _rcu_barrier(struct rcu_state *rsp,
+                         void (*call_rcu_func)(struct rcu_head *head,
+                                               void (*func)(struct rcu_head *head)))
+{
+        BUG_ON(in_interrupt());
+        /* Take mutex to serialize concurrent rcu_barrier() requests. */
+        mutex_lock(&rcu_barrier_mutex);
+        init_completion(&rcu_barrier_completion);
+        /*
+         * Initialize rcu_barrier_cpu_count to 1, then invoke
+         * rcu_barrier_func() on each CPU, so that each CPU also has
+         * incremented rcu_barrier_cpu_count.  Only then is it safe to
+         * 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.
+         */
+        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);
+        mutex_unlock(&rcu_barrier_mutex);
+}
+
+/**
+ * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
+ */
+void rcu_barrier_bh(void)
+{
+        _rcu_barrier(&rcu_bh_state, call_rcu_bh);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+
+/**
+ * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
+ */
+void rcu_barrier_sched(void)
+{
+        _rcu_barrier(&rcu_sched_state, call_rcu_sched);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+
 /*
  * Do boot-time initialization of a CPU's per-CPU RCU data.
  */
@@ -1434,6 +1559,8 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
         rdp->beenonline = 1;     /* We have now been online. */
         rdp->preemptable = preemptable;
         rdp->passed_quiesc_completed = lastcomp - 1;
+        rdp->qlen_last_fqs_check = 0;
+        rdp->n_force_qs_snap = rsp->n_force_qs;
         rdp->blimit = blimit;
         spin_unlock(&rnp->lock);                /* irqs remain disabled. */
 
@@ -1457,20 +1584,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
                 rnp = rnp->parent;
         } while (rnp != NULL && !(rnp->qsmaskinit & mask));
 
-        spin_unlock(&rsp->onofflock);           /* irqs remain disabled. */
-
-        /*
-         * A new grace period might start here.  If so, we will be part of
-         * it, and its gpnum will be greater than ours, so we will
-         * participate.  It is also possible for the gpnum to have been
-         * incremented before this function was called, and the bitmasks
-         * to not be filled out until now, in which case we will also
-         * participate due to our gpnum being behind.
-         */
-
-        /* Since it is coming online, the CPU is in a quiescent state. */
-        cpu_quiet(cpu, rsp, rdp, lastcomp);
-        local_irq_restore(flags);
+        spin_unlock_irqrestore(&rsp->onofflock, flags);
 }
 
 static void __cpuinit rcu_online_cpu(int cpu)
@@ -1493,6 +1607,22 @@ int __cpuinit rcu_cpu_notify(struct notifier_block *self,
         case CPU_UP_PREPARE_FROZEN:
                 rcu_online_cpu(cpu);
                 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.
+                 */
+                rcu_send_cbs_to_orphanage(&rcu_bh_state);
+                rcu_send_cbs_to_orphanage(&rcu_sched_state);
+                rcu_preempt_send_cbs_to_orphanage();
+                break;
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
         case CPU_UP_CANCELED:
@@ -1555,7 +1685,8 @@ static void __init rcu_init_one(struct rcu_state *rsp)
                 cpustride *= rsp->levelspread[i];
                 rnp = rsp->level[i];
                 for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
-                        spin_lock_init(&rnp->lock);
+                        if (rnp != rcu_get_root(rsp))
+                                spin_lock_init(&rnp->lock);
                         rnp->gpnum = 0;
                         rnp->qsmask = 0;
                         rnp->qsmaskinit = 0;
@@ -1578,6 +1709,7 @@ static void __init rcu_init_one(struct rcu_state *rsp)
                         INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
                 }
         }
+        spin_lock_init(&rcu_get_root(rsp)->lock);
 }
 
 /*
@@ -1587,6 +1719,10 @@ static void __init rcu_init_one(struct rcu_state *rsp)
  */
 #define RCU_INIT_FLAVOR(rsp, rcu_data) \
 do { \
+        int i; \
+        int j; \
+        struct rcu_node *rnp; \
+        \
         rcu_init_one(rsp); \
         rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \
         j = 0; \
@@ -1599,31 +1735,8 @@ do { \
         } \
 } while (0)
 
-#ifdef CONFIG_TREE_PREEMPT_RCU
-
-void __init __rcu_init_preempt(void)
-{
-        int i;                  /* All used by RCU_INIT_FLAVOR(). */
-        int j;
-        struct rcu_node *rnp;
-
-        RCU_INIT_FLAVOR(&rcu_preempt_state, rcu_preempt_data);
-}
-
-#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
-
-void __init __rcu_init_preempt(void)
-{
-}
-
-#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
-
 void __init __rcu_init(void)
 {
-        int i;                  /* All used by RCU_INIT_FLAVOR(). */
-        int j;
-        struct rcu_node *rnp;
-
         rcu_bootup_announce();
 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
         printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");
@@ -1634,6 +1747,4 @@ void __init __rcu_init(void)
         open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
 }
 
-module_param(blimit, int, 0);
-module_param(qhimark, int, 0);
-module_param(qlowmark, int, 0);
+#include "rcutree_plugin.h"