10 files changed, 297 insertions, 154 deletions

diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
index aaf65f6c6cd7..49587abfc2f7 100644
--- a/Documentation/RCU/trace.txt
+++ b/Documentation/RCU/trace.txt
@@ -105,14 +105,10 @@ o	"dt" is the current value of the dyntick counter that is incremented
         or one greater than the interrupt-nesting depth otherwise.
         The number after the second "/" is the NMI nesting depth.
 
-        This field is displayed only for CONFIG_NO_HZ kernels.
-
 o       "df" is the number of times that some other CPU has forced a
         quiescent state on behalf of this CPU due to this CPU being in
         dynticks-idle state.
 
-        This field is displayed only for CONFIG_NO_HZ kernels.
-
 o       "of" is the number of times that some other CPU has forced a
         quiescent state on behalf of this CPU due to this CPU being
         offline.  In a perfect world, this might never happen, but it
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index f743883f769e..bb7f30971858 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -139,20 +139,7 @@ static inline void account_system_vtime(struct task_struct *tsk)
 extern void account_system_vtime(struct task_struct *tsk);
 #endif
 
-#if defined(CONFIG_NO_HZ)
 #if defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
-extern void rcu_enter_nohz(void);
-extern void rcu_exit_nohz(void);
-
-static inline void rcu_irq_enter(void)
-{
-        rcu_exit_nohz();
-}
-
-static inline void rcu_irq_exit(void)
-{
-        rcu_enter_nohz();
-}
 
 static inline void rcu_nmi_enter(void)
 {
@@ -163,17 +150,9 @@ static inline void rcu_nmi_exit(void)
 }
 
 #else
-extern void rcu_irq_enter(void);
-extern void rcu_irq_exit(void);
 extern void rcu_nmi_enter(void);
 extern void rcu_nmi_exit(void);
 #endif
-#else
-# define rcu_irq_enter() do { } while (0)
-# define rcu_irq_exit() do { } while (0)
-# define rcu_nmi_enter() do { } while (0)
-# define rcu_nmi_exit() do { } while (0)
-#endif /* #if defined(CONFIG_NO_HZ) */
 
 /*
  * It is safe to do non-atomic ops on ->hardirq_context,
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 2cf4226ade7e..cd1ad4b04c6d 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -177,23 +177,10 @@ extern void rcu_sched_qs(int cpu);
 extern void rcu_bh_qs(int cpu);
 extern void rcu_check_callbacks(int cpu, int user);
 struct notifier_block;
-
-#ifdef CONFIG_NO_HZ
-
-extern void rcu_enter_nohz(void);
-extern void rcu_exit_nohz(void);
-
-#else /* #ifdef CONFIG_NO_HZ */
-
-static inline void rcu_enter_nohz(void)
-{
-}
-
-static inline void rcu_exit_nohz(void)
-{
-}
-
-#endif /* #else #ifdef CONFIG_NO_HZ */
+extern void rcu_idle_enter(void);
+extern void rcu_idle_exit(void);
+extern void rcu_irq_enter(void);
+extern void rcu_irq_exit(void);
 
 /*
  * Infrastructure to implement the synchronize_() primitives in
diff --git a/include/linux/tick.h b/include/linux/tick.h
index b232ccc0ee29..ca40838fdfb7 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -127,8 +127,15 @@ extern ktime_t tick_nohz_get_sleep_length(void);
 extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
 extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
 # else
-static inline void tick_nohz_stop_sched_tick(int inidle) { }
-static inline void tick_nohz_restart_sched_tick(void) { }
+static inline void tick_nohz_stop_sched_tick(int inidle)
+{
+        if (inidle)
+                rcu_idle_enter();
+}
+static inline void tick_nohz_restart_sched_tick(void)
+{
+        rcu_idle_exit();
+}
 static inline ktime_t tick_nohz_get_sleep_length(void)
 {
         ktime_t len = { .tv64 = NSEC_PER_SEC/HZ };
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 669fbd62ec25..e5771804c507 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -246,19 +246,21 @@ TRACE_EVENT(rcu_fqs,
  */
 TRACE_EVENT(rcu_dyntick,
 
-        TP_PROTO(char *polarity),
+        TP_PROTO(char *polarity, int nesting),
 
-        TP_ARGS(polarity),
+        TP_ARGS(polarity, nesting),
 
         TP_STRUCT__entry(
                 __field(char *, polarity)
+                __field(int, nesting)
         ),
 
         TP_fast_assign(
                 __entry->polarity = polarity;
+                __entry->nesting = nesting;
         ),
 
-        TP_printk("%s", __entry->polarity)
+        TP_printk("%s %d", __entry->polarity, __entry->nesting)
 );
 
 /*
@@ -443,7 +445,7 @@ TRACE_EVENT(rcu_batch_end,
 #define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0)
 #define trace_rcu_quiescent_state_report(rcuname, gpnum, mask, qsmask, level, grplo, grphi, gp_tasks) do { } while (0)
 #define trace_rcu_fqs(rcuname, gpnum, cpu, qsevent) do { } while (0)
-#define trace_rcu_dyntick(polarity) do { } while (0)
+#define trace_rcu_dyntick(polarity, nesting) do { } while (0)
 #define trace_rcu_callback(rcuname, rhp, qlen) do { } while (0)
 #define trace_rcu_kfree_callback(rcuname, rhp, offset, qlen) do { } while (0)
 #define trace_rcu_batch_start(rcuname, qlen, blimit) do { } while (0)
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 636af6d9c6e5..3ab77bdc90c4 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -53,31 +53,122 @@ static void __call_rcu(struct rcu_head *head,
 
 #include "rcutiny_plugin.h"
 
-#ifdef CONFIG_NO_HZ
+static long long rcu_dynticks_nesting = LLONG_MAX / 2;
 
-static long rcu_dynticks_nesting = 1;
+/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
+static void rcu_idle_enter_common(void)
+{
+        if (rcu_dynticks_nesting) {
+                RCU_TRACE(trace_rcu_dyntick("--=", rcu_dynticks_nesting));
+                return;
+        }
+        RCU_TRACE(trace_rcu_dyntick("Start", rcu_dynticks_nesting));
+        if (!idle_cpu(smp_processor_id())) {
+                WARN_ON_ONCE(1);        /* must be idle task! */
+                RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
+                                            rcu_dynticks_nesting));
+                ftrace_dump(DUMP_ALL);
+        }
+        rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+}
 
 /*
- * Enter dynticks-idle mode, which is an extended quiescent state
- * if we have fully entered that mode (i.e., if the new value of
- * dynticks_nesting is zero).
+ * Enter idle, which is an extended quiescent state if we have fully
+ * entered that mode (i.e., if the new value of dynticks_nesting is zero).
  */
-void rcu_enter_nohz(void)
+void rcu_idle_enter(void)
 {
-        if (--rcu_dynticks_nesting == 0)
-                rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+        unsigned long flags;
+
+        local_irq_save(flags);
+        rcu_dynticks_nesting = 0;
+        rcu_idle_enter_common();
+        local_irq_restore(flags);
 }
 
 /*
- * Exit dynticks-idle mode, so that we are no longer in an extended
- * quiescent state.
+ * Exit an interrupt handler towards idle.
+ */
+void rcu_irq_exit(void)
+{
+        unsigned long flags;
+
+        local_irq_save(flags);
+        rcu_dynticks_nesting--;
+        WARN_ON_ONCE(rcu_dynticks_nesting < 0);
+        rcu_idle_enter_common();
+        local_irq_restore(flags);
+}
+
+/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
+static void rcu_idle_exit_common(long long oldval)
+{
+        if (oldval) {
+                RCU_TRACE(trace_rcu_dyntick("++=", rcu_dynticks_nesting));
+                return;
+        }
+        RCU_TRACE(trace_rcu_dyntick("End", oldval));
+        if (!idle_cpu(smp_processor_id())) {
+                WARN_ON_ONCE(1);        /* must be idle task! */
+                RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
+                          oldval));
+                ftrace_dump(DUMP_ALL);
+        }
+}
+
+/*
+ * Exit idle, so that we are no longer in an extended quiescent state.
  */
-void rcu_exit_nohz(void)
+void rcu_idle_exit(void)
 {
+        unsigned long flags;
+        long long oldval;
+
+        local_irq_save(flags);
+        oldval = rcu_dynticks_nesting;
+        WARN_ON_ONCE(oldval != 0);
+        rcu_dynticks_nesting = LLONG_MAX / 2;
+        rcu_idle_exit_common(oldval);
+        local_irq_restore(flags);
+}
+
+/*
+ * Enter an interrupt handler, moving away from idle.
+ */
+void rcu_irq_enter(void)
+{
+        unsigned long flags;
+        long long oldval;
+
+        local_irq_save(flags);
+        oldval = rcu_dynticks_nesting;
         rcu_dynticks_nesting++;
+        WARN_ON_ONCE(rcu_dynticks_nesting == 0);
+        rcu_idle_exit_common(oldval);
+        local_irq_restore(flags);
+}
+
+#ifdef CONFIG_PROVE_RCU
+
+/*
+ * Test whether RCU thinks that the current CPU is idle.
+ */
+int rcu_is_cpu_idle(void)
+{
+        return !rcu_dynticks_nesting;
 }
 
-#endif /* #ifdef CONFIG_NO_HZ */
+#endif /* #ifdef CONFIG_PROVE_RCU */
+
+/*
+ * Test whether the current CPU was interrupted from idle.  Nested
+ * interrupts don't count, we must be running at the first interrupt
+ * level.
+ */
+int rcu_is_cpu_rrupt_from_idle(void)
+{
+        return rcu_dynticks_nesting <= 0;
+}
 
 /*
  * Helper function for rcu_sched_qs() and rcu_bh_qs().
@@ -126,14 +217,13 @@ void rcu_bh_qs(int cpu)
 
 /*
  * Check to see if the scheduling-clock interrupt came from an extended
- * quiescent state, and, if so, tell RCU about it.
+ * quiescent state, and, if so, tell RCU about it.  This function must
+ * be called from hardirq context.  It is normally called from the
+ * scheduling-clock interrupt.
  */
 void rcu_check_callbacks(int cpu, int user)
 {
-        if (user ||
-            (idle_cpu(cpu) &&
-             !in_softirq() &&
-             hardirq_count() <= (1 << HARDIRQ_SHIFT)))
+        if (user || rcu_is_cpu_rrupt_from_idle())
                 rcu_sched_qs(cpu);
         else if (!in_softirq())
                 rcu_bh_qs(cpu);
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 5d0b55a3a8c0..1c40326724f6 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -195,12 +195,10 @@ void rcu_note_context_switch(int cpu)
 }
 EXPORT_SYMBOL_GPL(rcu_note_context_switch);
 
-#ifdef CONFIG_NO_HZ
 DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
-        .dynticks_nesting = 1,
+        .dynticks_nesting = LLONG_MAX / 2,
         .dynticks = ATOMIC_INIT(1),
 };
-#endif /* #ifdef CONFIG_NO_HZ */
 
 static int blimit = 10;         /* Maximum callbacks per rcu_do_batch. */
 static int qhimark = 10000;     /* If this many pending, ignore blimit. */
@@ -328,11 +326,11 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
                 return 1;
         }
 
-        /* If preemptible RCU, no point in sending reschedule IPI. */
-        if (rdp->preemptible)
-                return 0;
-
-        /* The CPU is online, so send it a reschedule IPI. */
+        /*
+         * The CPU is online, so send it a reschedule IPI.  This forces
+         * it through the scheduler, and (inefficiently) also handles cases
+         * where idle loops fail to inform RCU about the CPU being idle.
+         */
         if (rdp->cpu != smp_processor_id())
                 smp_send_reschedule(rdp->cpu);
         else
@@ -343,51 +341,97 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
 
 #endif /* #ifdef CONFIG_SMP */
 
-#ifdef CONFIG_NO_HZ
+/*
+ * rcu_idle_enter_common - inform RCU that current CPU is moving towards idle
+ *
+ * If the new value of the ->dynticks_nesting counter now is zero,
+ * we really have entered idle, and must do the appropriate accounting.
+ * The caller must have disabled interrupts.
+ */
+static void rcu_idle_enter_common(struct rcu_dynticks *rdtp)
+{
+        if (rdtp->dynticks_nesting) {
+                trace_rcu_dyntick("--=", rdtp->dynticks_nesting);
+                return;
+        }
+        trace_rcu_dyntick("Start", rdtp->dynticks_nesting);
+        if (!idle_cpu(smp_processor_id())) {
+                WARN_ON_ONCE(1);        /* must be idle task! */
+                trace_rcu_dyntick("Error on entry: not idle task",
+                                   rdtp->dynticks_nesting);
+                ftrace_dump(DUMP_ALL);
+        }
+        /* 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);
+}
 
 /**
- * rcu_enter_nohz - inform RCU that current CPU is entering nohz
+ * rcu_idle_enter - inform RCU that current CPU is entering idle
  *
- * Enter nohz mode, in other words, -leave- the mode in which RCU
+ * Enter idle mode, in other words, -leave- the mode in which RCU
  * read-side critical sections can occur.  (Though RCU read-side
- * critical sections can occur in irq handlers in nohz mode, a possibility
- * handled by rcu_irq_enter() and rcu_irq_exit()).
+ * critical sections can occur in irq handlers in idle, a possibility
+ * handled by irq_enter() and irq_exit().)
+ *
+ * We crowbar the ->dynticks_nesting field to zero to allow for
+ * the possibility of usermode upcalls having messed up our count
+ * of interrupt nesting level during the prior busy period.
  */
-void rcu_enter_nohz(void)
+void rcu_idle_enter(void)
 {
         unsigned long flags;
         struct rcu_dynticks *rdtp;
 
         local_irq_save(flags);
         rdtp = &__get_cpu_var(rcu_dynticks);
-        if (--rdtp->dynticks_nesting) {
-                local_irq_restore(flags);
-                return;
-        }
-        trace_rcu_dyntick("Start");
-        /* 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);
+        rdtp->dynticks_nesting = 0;
+        rcu_idle_enter_common(rdtp);
         local_irq_restore(flags);
 }
 
-/*
- * rcu_exit_nohz - inform RCU that current CPU is leaving nohz
+/**
+ * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
+ *
+ * Exit from an interrupt handler, which might possibly result in entering
+ * idle mode, in other words, leaving the mode in which read-side critical
+ * sections can occur.
  *
- * Exit nohz mode, in other words, -enter- the mode in which RCU
- * read-side critical sections normally occur.
+ * This code assumes that the idle loop never does anything that might
+ * result in unbalanced calls to irq_enter() and irq_exit().  If your
+ * architecture violates this assumption, RCU will give you what you
+ * deserve, good and hard.  But very infrequently and irreproducibly.
+ *
+ * Use things like work queues to work around this limitation.
+ *
+ * You have been warned.
  */
-void rcu_exit_nohz(void)
+void rcu_irq_exit(void)
 {
         unsigned long flags;
         struct rcu_dynticks *rdtp;
 
         local_irq_save(flags);
         rdtp = &__get_cpu_var(rcu_dynticks);
-        if (rdtp->dynticks_nesting++) {
-                local_irq_restore(flags);
+        rdtp->dynticks_nesting--;
+        WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
+        rcu_idle_enter_common(rdtp);
+        local_irq_restore(flags);
+}
+
+/*
+ * rcu_idle_exit_common - inform RCU that current CPU is moving away from idle
+ *
+ * If the new value of the ->dynticks_nesting counter was previously zero,
+ * we really have exited idle, and must do the appropriate accounting.
+ * The caller must have disabled interrupts.
+ */
+static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
+{
+        if (oldval) {
+                trace_rcu_dyntick("++=", rdtp->dynticks_nesting);
                 return;
         }
         smp_mb__before_atomic_inc();  /* Force ordering w/previous sojourn. */
@@ -395,7 +439,71 @@ void rcu_exit_nohz(void)
         /* 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));
-        trace_rcu_dyntick("End");
+        trace_rcu_dyntick("End", oldval);
+        if (!idle_cpu(smp_processor_id())) {
+                WARN_ON_ONCE(1);        /* must be idle task! */
+                trace_rcu_dyntick("Error on exit: not idle task", oldval);
+                ftrace_dump(DUMP_ALL);
+        }
+}
+
+/**
+ * rcu_idle_exit - inform RCU that current CPU is leaving idle
+ *
+ * Exit idle mode, in other words, -enter- the mode in which RCU
+ * read-side critical sections can occur.
+ *
+ * We crowbar the ->dynticks_nesting field to LLONG_MAX/2 to allow for
+ * the possibility of usermode upcalls messing up our count
+ * of interrupt nesting level during the busy period that is just
+ * now starting.
+ */
+void rcu_idle_exit(void)
+{
+        unsigned long flags;
+        struct rcu_dynticks *rdtp;
+        long long oldval;
+
+        local_irq_save(flags);
+        rdtp = &__get_cpu_var(rcu_dynticks);
+        oldval = rdtp->dynticks_nesting;
+        WARN_ON_ONCE(oldval != 0);
+        rdtp->dynticks_nesting = LLONG_MAX / 2;
+        rcu_idle_exit_common(rdtp, oldval);
+        local_irq_restore(flags);
+}
+
+/**
+ * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
+ *
+ * Enter an interrupt handler, which might possibly result in exiting
+ * idle mode, in other words, entering the mode in which read-side critical
+ * sections can occur.
+ *
+ * Note that the Linux kernel is fully capable of entering an interrupt
+ * handler that it never exits, for example when doing upcalls to
+ * user mode!  This code assumes that the idle loop never does upcalls to
+ * user mode.  If your architecture does do upcalls from the idle loop (or
+ * does anything else that results in unbalanced calls to the irq_enter()
+ * and irq_exit() functions), RCU will give you what you deserve, good
+ * and hard.  But very infrequently and irreproducibly.
+ *
+ * Use things like work queues to work around this limitation.
+ *
+ * You have been warned.
+ */
+void rcu_irq_enter(void)
+{
+        unsigned long flags;
+        struct rcu_dynticks *rdtp;
+        long long oldval;
+
+        local_irq_save(flags);
+        rdtp = &__get_cpu_var(rcu_dynticks);
+        oldval = rdtp->dynticks_nesting;
+        rdtp->dynticks_nesting++;
+        WARN_ON_ONCE(rdtp->dynticks_nesting == 0);
+        rcu_idle_exit_common(rdtp, oldval);
         local_irq_restore(flags);
 }
 
@@ -442,27 +550,32 @@ void rcu_nmi_exit(void)
         WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
 }
 
+#ifdef CONFIG_PROVE_RCU
+
 /**
- * rcu_irq_enter - inform RCU of entry to hard irq context
+ * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle
  *
- * If the CPU was idle with dynamic ticks active, this updates the
- * rdtp->dynticks to let the RCU handling know that the CPU is active.
+ * If the current CPU is in its idle loop and is neither in an interrupt
+ * or NMI handler, return true.  The caller must have at least disabled
+ * preemption.
  */
-void rcu_irq_enter(void)
+int rcu_is_cpu_idle(void)
 {
-        rcu_exit_nohz();
+        return (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0;
 }
 
+#endif /* #ifdef CONFIG_PROVE_RCU */
+
 /**
- * rcu_irq_exit - inform RCU of exit from hard irq context
+ * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
  *
- * If the CPU was idle with dynamic ticks active, update the rdp->dynticks
- * to put let the RCU handling be aware that the CPU is going back to idle
- * with no ticks.
+ * If the current CPU is idle or running at a first-level (not nested)
+ * interrupt from idle, return true.  The caller must have at least
+ * disabled preemption.
  */
-void rcu_irq_exit(void)
+int rcu_is_cpu_rrupt_from_idle(void)
 {
-        rcu_enter_nohz();
+        return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1;
 }
 
 #ifdef CONFIG_SMP
@@ -512,24 +625,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 
 #endif /* #ifdef CONFIG_SMP */
 
-#else /* #ifdef CONFIG_NO_HZ */
-
-#ifdef CONFIG_SMP
-
-static int dyntick_save_progress_counter(struct rcu_data *rdp)
-{
-        return 0;
-}
-
-static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
-{
-        return rcu_implicit_offline_qs(rdp);
-}
-
-#endif /* #ifdef CONFIG_SMP */
-
-#endif /* #else #ifdef CONFIG_NO_HZ */
-
 int rcu_cpu_stall_suppress __read_mostly;
 
 static void record_gp_stall_check_time(struct rcu_state *rsp)
@@ -1334,16 +1429,14 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
  * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
  * Also schedule RCU core processing.
  *
- * This function must be called with hardirqs disabled.  It is normally
+ * This function must be called from hardirq context.  It is normally
  * invoked from the scheduling-clock interrupt.  If rcu_pending returns
  * false, there is no point in invoking rcu_check_callbacks().
  */
 void rcu_check_callbacks(int cpu, int user)
 {
         trace_rcu_utilization("Start scheduler-tick");
-        if (user ||
-            (idle_cpu(cpu) && rcu_scheduler_active &&
-             !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+        if (user || rcu_is_cpu_rrupt_from_idle()) {
 
                 /*
                  * Get here if this CPU took its interrupt from user
@@ -1913,9 +2006,9 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
         for (i = 0; i < RCU_NEXT_SIZE; i++)
                 rdp->nxttail[i] = &rdp->nxtlist;
         rdp->qlen = 0;
-#ifdef CONFIG_NO_HZ
         rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
-#endif /* #ifdef CONFIG_NO_HZ */
+        WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != LLONG_MAX / 2);
+        WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
         rdp->cpu = cpu;
         rdp->rsp = rsp;
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
@@ -1942,6 +2035,8 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
         rdp->qlen_last_fqs_check = 0;
         rdp->n_force_qs_snap = rsp->n_force_qs;
         rdp->blimit = blimit;
+        WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != LLONG_MAX / 2);
+        WARN_ON_ONCE((atomic_read(&rdp->dynticks->dynticks) & 0x1) != 1);
         raw_spin_unlock(&rnp->lock);            /* irqs remain disabled. */
 
         /*
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 517f2f89a293..0963fa1541ac 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -84,9 +84,10 @@
  * Dynticks per-CPU state.
  */
 struct rcu_dynticks {
-        int dynticks_nesting;   /* Track irq/process nesting level. */
-        int dynticks_nmi_nesting; /* Track NMI nesting level. */
-        atomic_t dynticks;      /* Even value for dynticks-idle, else odd. */
+        long long dynticks_nesting; /* Track irq/process nesting level. */
+                                    /* Process level is worth LLONG_MAX/2. */
+        int dynticks_nmi_nesting;   /* Track NMI nesting level. */
+        atomic_t dynticks;          /* Even value for idle, else odd. */
 };
 
 /* RCU's kthread states for tracing. */
@@ -274,16 +275,12 @@ struct rcu_data {
                                         /* did other CPU force QS recently? */
         long            blimit;         /* Upper limit on a processed batch */
 
-#ifdef CONFIG_NO_HZ
         /* 3) dynticks interface. */
         struct rcu_dynticks *dynticks;  /* Shared per-CPU dynticks state. */
         int dynticks_snap;              /* Per-GP tracking for dynticks. */
-#endif /* #ifdef CONFIG_NO_HZ */
 
         /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
-#ifdef CONFIG_NO_HZ
         unsigned long dynticks_fqs;     /* Kicked due to dynticks idle. */
-#endif /* #ifdef CONFIG_NO_HZ */
         unsigned long offline_fqs;      /* Kicked due to being offline. */
         unsigned long resched_ipi;      /* Sent a resched IPI. */
 
@@ -307,11 +304,7 @@ struct rcu_data {
 #define RCU_GP_INIT             1       /* Grace period being initialized. */
 #define RCU_SAVE_DYNTICK        2       /* Need to scan dyntick state. */
 #define RCU_FORCE_QS            3       /* Need to force quiescent state. */
-#ifdef CONFIG_NO_HZ
 #define RCU_SIGNAL_INIT         RCU_SAVE_DYNTICK
-#else /* #ifdef CONFIG_NO_HZ */
-#define RCU_SIGNAL_INIT         RCU_FORCE_QS
-#endif /* #else #ifdef CONFIG_NO_HZ */
 
 #define RCU_JIFFIES_TILL_FORCE_QS        3      /* for rsp->jiffies_force_qs */
 
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index 59c7bee4ce0f..654cfe67f0d1 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -67,13 +67,11 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
                    rdp->completed, rdp->gpnum,
                    rdp->passed_quiesce, rdp->passed_quiesce_gpnum,
                    rdp->qs_pending);
-#ifdef CONFIG_NO_HZ
-        seq_printf(m, " dt=%d/%d/%d df=%lu",
+        seq_printf(m, " dt=%d/%llx/%d df=%lu",
                    atomic_read(&rdp->dynticks->dynticks),
                    rdp->dynticks->dynticks_nesting,
                    rdp->dynticks->dynticks_nmi_nesting,
                    rdp->dynticks_fqs);
-#endif /* #ifdef CONFIG_NO_HZ */
         seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi);
         seq_printf(m, " ql=%ld qs=%c%c%c%c",
                    rdp->qlen,
@@ -141,13 +139,11 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
                    rdp->completed, rdp->gpnum,
                    rdp->passed_quiesce, rdp->passed_quiesce_gpnum,
                    rdp->qs_pending);
-#ifdef CONFIG_NO_HZ
-        seq_printf(m, ",%d,%d,%d,%lu",
+        seq_printf(m, ",%d,%llx,%d,%lu",
                    atomic_read(&rdp->dynticks->dynticks),
                    rdp->dynticks->dynticks_nesting,
                    rdp->dynticks->dynticks_nmi_nesting,
                    rdp->dynticks_fqs);
-#endif /* #ifdef CONFIG_NO_HZ */
         seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi);
         seq_printf(m, ",%ld,\"%c%c%c%c\"", rdp->qlen,
                    ".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
@@ -171,9 +167,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
 static int show_rcudata_csv(struct seq_file *m, void *unused)
 {
         seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pgp\",\"pq\",");
-#ifdef CONFIG_NO_HZ
         seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\",");
-#endif /* #ifdef CONFIG_NO_HZ */
         seq_puts(m, "\"of\",\"ri\",\"ql\",\"qs\"");
 #ifdef CONFIG_RCU_BOOST
         seq_puts(m, "\"kt\",\"ktl\"");
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 40420644d0ba..5d9d23665f12 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -434,7 +434,6 @@ void tick_nohz_stop_sched_tick(int inidle)
                         ts->idle_tick = hrtimer_get_expires(&ts->sched_timer);
                         ts->tick_stopped = 1;
                         ts->idle_jiffies = last_jiffies;
-                        rcu_enter_nohz();
                 }
 
                 ts->idle_sleeps++;
@@ -473,6 +472,8 @@ out:
         ts->last_jiffies = last_jiffies;
         ts->sleep_length = ktime_sub(dev->next_event, now);
 end:
+        if (inidle)
+                rcu_idle_enter();
         local_irq_restore(flags);
 }
 
@@ -529,6 +530,7 @@ void tick_nohz_restart_sched_tick(void)
         ktime_t now;
 
         local_irq_disable();
+        rcu_idle_exit();
         if (ts->idle_active || (ts->inidle && ts->tick_stopped))
                 now = ktime_get();
 
@@ -543,8 +545,6 @@ void tick_nohz_restart_sched_tick(void)
 
         ts->inidle = 0;
 
-        rcu_exit_nohz();
-
         /* Update jiffies first */
         select_nohz_load_balancer(0);
         tick_do_update_jiffies64(now);