Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull RCU updates from Paul E. McKenney:

 - Streamline RCU's use of per-CPU variables, shifting from "cpu"
   arguments to functions to "this_"-style per-CPU variable accessors.

 - Signal-handling RCU updates.

 - Real-time updates.

 - Torture-test updates.

 - Miscellaneous fixes.

 - Documentation updates.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

15 files changed, 268 insertions, 137 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 90a3d017b90c..5d220234b3ca 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -86,6 +86,16 @@ static struct {
 #define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
 #define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)
 
+static void apply_puts_pending(int max)
+{
+	int delta;
+
+	if (atomic_read(&cpu_hotplug.puts_pending) >= max) {
+		delta = atomic_xchg(&cpu_hotplug.puts_pending, 0);
+		cpu_hotplug.refcount -= delta;
+	}
+}
+
 void get_online_cpus(void)
 {
 	might_sleep();
@@ -93,6 +103,7 @@ void get_online_cpus(void)
 		return;
 	cpuhp_lock_acquire_read();
 	mutex_lock(&cpu_hotplug.lock);
+	apply_puts_pending(65536);
 	cpu_hotplug.refcount++;
 	mutex_unlock(&cpu_hotplug.lock);
 }
@@ -105,6 +116,7 @@ bool try_get_online_cpus(void)
 	if (!mutex_trylock(&cpu_hotplug.lock))
 		return false;
 	cpuhp_lock_acquire_tryread();
+	apply_puts_pending(65536);
 	cpu_hotplug.refcount++;
 	mutex_unlock(&cpu_hotplug.lock);
 	return true;
@@ -161,12 +173,7 @@ void cpu_hotplug_begin(void)
 	cpuhp_lock_acquire();
 	for (;;) {
 		mutex_lock(&cpu_hotplug.lock);
-		if (atomic_read(&cpu_hotplug.puts_pending)) {
-			int delta;
-
-			delta = atomic_xchg(&cpu_hotplug.puts_pending, 0);
-			cpu_hotplug.refcount -= delta;
-		}
+		apply_puts_pending(1);
 		if (likely(!cpu_hotplug.refcount))
 			break;
 		__set_current_state(TASK_UNINTERRUPTIBLE);
diff --git a/kernel/fork.c b/kernel/fork.c
index 9b7d746d6d62..9ca84189cfc2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1022,11 +1022,14 @@ void __cleanup_sighand(struct sighand_struct *sighand)
 {
 	if (atomic_dec_and_test(&sighand->count)) {
 		signalfd_cleanup(sighand);
+		/*
+		 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
+		 * without an RCU grace period, see __lock_task_sighand().
+		 */
 		kmem_cache_free(sighand_cachep, sighand);
 	}
 }
 
-
 /*
  * Initialize POSIX timer handling for a thread group.
  */
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index 807ccfbf69b3..e6fae503d1bc 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -1,6 +1,6 @@
 obj-y += update.o srcu.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_TREE_RCU) += tree.o
-obj-$(CONFIG_TREE_PREEMPT_RCU) += tree.o
+obj-$(CONFIG_PREEMPT_RCU) += tree.o
 obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.o
 obj-$(CONFIG_TINY_RCU) += tiny.o
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index ff1a6de62f17..07bb02eda844 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -135,4 +135,6 @@ int rcu_jiffies_till_stall_check(void);
  */
 #define TPS(x)  tracepoint_string(x)
 
+void rcu_early_boot_tests(void);
+
 #endif /* __LINUX_RCU_H */
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 240fa9094f83..4d559baf06e0 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -812,6 +812,7 @@ rcu_torture_cbflood(void *arg)
 		cur_ops->cb_barrier();
 		stutter_wait("rcu_torture_cbflood");
 	} while (!torture_must_stop());
+	vfree(rhp);
 	torture_kthread_stopping("rcu_torture_cbflood");
 	return 0;
 }
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index c0623fc47125..0db5649f8817 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -247,7 +247,7 @@ void rcu_bh_qs(void)
  * be called from hardirq context.  It is normally called from the
  * scheduling-clock interrupt.
  */
-void rcu_check_callbacks(int cpu, int user)
+void rcu_check_callbacks(int user)
 {
 	RCU_TRACE(check_cpu_stalls());
 	if (user || rcu_is_cpu_rrupt_from_idle())
@@ -380,7 +380,9 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
 }
 EXPORT_SYMBOL_GPL(call_rcu_bh);
 
-void rcu_init(void)
+void __init rcu_init(void)
 {
 	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+
+	rcu_early_boot_tests();
 }
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9815447d22e0..7680fc275036 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -105,7 +105,7 @@ struct rcu_state sname##_state = { \
 	.name = RCU_STATE_NAME(sname), \
 	.abbr = sabbr, \
 }; \
-DEFINE_PER_CPU(struct rcu_data, sname##_data)
+DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data)
 
 RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
 RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
@@ -152,19 +152,6 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active);
  */
 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(unsigned int, rcu_cpu_kthread_loops);
-DEFINE_PER_CPU(char, rcu_cpu_has_work);
-
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
 static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
 static void invoke_rcu_core(void);
 static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
@@ -286,11 +273,11 @@ static void rcu_momentary_dyntick_idle(void)
  * and requires special handling for preemptible RCU.
  * The caller must have disabled preemption.
  */
-void rcu_note_context_switch(int cpu)
+void rcu_note_context_switch(void)
 {
 	trace_rcu_utilization(TPS("Start context switch"));
 	rcu_sched_qs();
-	rcu_preempt_note_context_switch(cpu);
+	rcu_preempt_note_context_switch();
 	if (unlikely(raw_cpu_read(rcu_sched_qs_mask)))
 		rcu_momentary_dyntick_idle();
 	trace_rcu_utilization(TPS("End context switch"));
@@ -325,7 +312,7 @@ static void force_qs_rnp(struct rcu_state *rsp,
 				  unsigned long *maxj),
 			 bool *isidle, unsigned long *maxj);
 static void force_quiescent_state(struct rcu_state *rsp);
-static int rcu_pending(int cpu);
+static int rcu_pending(void);
 
 /*
  * Return the number of RCU-sched batches processed thus far for debug & stats.
@@ -510,11 +497,11 @@ cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
  * we really have entered idle, and must do the appropriate accounting.
  * The caller must have disabled interrupts.
  */
-static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
-				bool user)
+static void rcu_eqs_enter_common(long long oldval, bool user)
 {
 	struct rcu_state *rsp;
 	struct rcu_data *rdp;
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
 
 	trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting);
 	if (!user && !is_idle_task(current)) {
@@ -531,7 +518,7 @@ static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
 		rdp = this_cpu_ptr(rsp->rda);
 		do_nocb_deferred_wakeup(rdp);
 	}
-	rcu_prepare_for_idle(smp_processor_id());
+	rcu_prepare_for_idle();
 	/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
 	smp_mb__before_atomic();  /* See above. */
 	atomic_inc(&rdtp->dynticks);
@@ -565,7 +552,7 @@ static void rcu_eqs_enter(bool user)
 	WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
 	if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) {
 		rdtp->dynticks_nesting = 0;
-		rcu_eqs_enter_common(rdtp, oldval, user);
+		rcu_eqs_enter_common(oldval, user);
 	} else {
 		rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
 	}
@@ -589,7 +576,7 @@ void rcu_idle_enter(void)
 
 	local_irq_save(flags);
 	rcu_eqs_enter(false);
-	rcu_sysidle_enter(this_cpu_ptr(&rcu_dynticks), 0);
+	rcu_sysidle_enter(0);
 	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_enter);
@@ -639,8 +626,8 @@ void rcu_irq_exit(void)
 	if (rdtp->dynticks_nesting)
 		trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting);
 	else
-		rcu_eqs_enter_common(rdtp, oldval, true);
-	rcu_sysidle_enter(rdtp, 1);
+		rcu_eqs_enter_common(oldval, true);
+	rcu_sysidle_enter(1);
 	local_irq_restore(flags);
 }
 
@@ -651,16 +638,17 @@ void rcu_irq_exit(void)
  * we really have exited idle, and must do the appropriate accounting.
  * The caller must have disabled interrupts.
  */
-static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval,
-			       int user)
+static void rcu_eqs_exit_common(long long oldval, int user)
 {
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+
 	rcu_dynticks_task_exit();
 	smp_mb__before_atomic();  /* 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();  /* See above. */
 	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
-	rcu_cleanup_after_idle(smp_processor_id());
+	rcu_cleanup_after_idle();
 	trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting);
 	if (!user && !is_idle_task(current)) {
 		struct task_struct *idle __maybe_unused =
@@ -691,7 +679,7 @@ static void rcu_eqs_exit(bool user)
 		rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
 	} else {
 		rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
-		rcu_eqs_exit_common(rdtp, oldval, user);
+		rcu_eqs_exit_common(oldval, user);
 	}
 }
 
@@ -712,7 +700,7 @@ void rcu_idle_exit(void)
 
 	local_irq_save(flags);
 	rcu_eqs_exit(false);
-	rcu_sysidle_exit(this_cpu_ptr(&rcu_dynticks), 0);
+	rcu_sysidle_exit(0);
 	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_exit);
@@ -763,8 +751,8 @@ void rcu_irq_enter(void)
 	if (oldval)
 		trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting);
 	else
-		rcu_eqs_exit_common(rdtp, oldval, true);
-	rcu_sysidle_exit(rdtp, 1);
+		rcu_eqs_exit_common(oldval, true);
+	rcu_sysidle_exit(1);
 	local_irq_restore(flags);
 }
 
@@ -2387,7 +2375,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
  * 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)
+void rcu_check_callbacks(int user)
 {
 	trace_rcu_utilization(TPS("Start scheduler-tick"));
 	increment_cpu_stall_ticks();
@@ -2419,8 +2407,8 @@ void rcu_check_callbacks(int cpu, int user)
 
 		rcu_bh_qs();
 	}
-	rcu_preempt_check_callbacks(cpu);
-	if (rcu_pending(cpu))
+	rcu_preempt_check_callbacks();
+	if (rcu_pending())
 		invoke_rcu_core();
 	if (user)
 		rcu_note_voluntary_context_switch(current);
@@ -2963,6 +2951,9 @@ static int synchronize_sched_expedited_cpu_stop(void *data)
  */
 void synchronize_sched_expedited(void)
 {
+	cpumask_var_t cm;
+	bool cma = false;
+	int cpu;
 	long firstsnap, s, snap;
 	int trycount = 0;
 	struct rcu_state *rsp = &rcu_sched_state;
@@ -2997,11 +2988,26 @@ void synchronize_sched_expedited(void)
 	}
 	WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
 
+	/* Offline CPUs, idle CPUs, and any CPU we run on are quiescent. */
+	cma = zalloc_cpumask_var(&cm, GFP_KERNEL);
+	if (cma) {
+		cpumask_copy(cm, cpu_online_mask);
+		cpumask_clear_cpu(raw_smp_processor_id(), cm);
+		for_each_cpu(cpu, cm) {
+			struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+
+			if (!(atomic_add_return(0, &rdtp->dynticks) & 0x1))
+				cpumask_clear_cpu(cpu, cm);
+		}
+		if (cpumask_weight(cm) == 0)
+			goto all_cpus_idle;
+	}
+
 	/*
 	 * Each pass through the following loop attempts to force a
 	 * context switch on each CPU.
 	 */
-	while (try_stop_cpus(cpu_online_mask,
+	while (try_stop_cpus(cma ? cm : cpu_online_mask,
 			     synchronize_sched_expedited_cpu_stop,
 			     NULL) == -EAGAIN) {
 		put_online_cpus();
@@ -3013,6 +3019,7 @@ void synchronize_sched_expedited(void)
 			/* ensure test happens before caller kfree */
 			smp_mb__before_atomic(); /* ^^^ */
 			atomic_long_inc(&rsp->expedited_workdone1);
+			free_cpumask_var(cm);
 			return;
 		}
 
@@ -3022,6 +3029,7 @@ void synchronize_sched_expedited(void)
 		} else {
 			wait_rcu_gp(call_rcu_sched);
 			atomic_long_inc(&rsp->expedited_normal);
+			free_cpumask_var(cm);
 			return;
 		}
 
@@ -3031,6 +3039,7 @@ void synchronize_sched_expedited(void)
 			/* ensure test happens before caller kfree */
 			smp_mb__before_atomic(); /* ^^^ */
 			atomic_long_inc(&rsp->expedited_workdone2);
+			free_cpumask_var(cm);
 			return;
 		}
 
@@ -3045,6 +3054,7 @@ void synchronize_sched_expedited(void)
 			/* CPU hotplug operation in flight, use normal GP. */
 			wait_rcu_gp(call_rcu_sched);
 			atomic_long_inc(&rsp->expedited_normal);
+			free_cpumask_var(cm);
 			return;
 		}
 		snap = atomic_long_read(&rsp->expedited_start);
@@ -3052,6 +3062,9 @@ void synchronize_sched_expedited(void)
 	}
 	atomic_long_inc(&rsp->expedited_stoppedcpus);
 
+all_cpus_idle:
+	free_cpumask_var(cm);
+
 	/*
 	 * Everyone up to our most recent fetch is covered by our grace
 	 * period.  Update the counter, but only if our work is still
@@ -3143,12 +3156,12 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
  * by the current CPU, returning 1 if so.  This function is part of the
  * RCU implementation; it is -not- an exported member of the RCU API.
  */
-static int rcu_pending(int cpu)
+static int rcu_pending(void)
 {
 	struct rcu_state *rsp;
 
 	for_each_rcu_flavor(rsp)
-		if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu)))
+		if (__rcu_pending(rsp, this_cpu_ptr(rsp->rda)))
 			return 1;
 	return 0;
 }
@@ -3158,7 +3171,7 @@ static int rcu_pending(int cpu)
  * non-NULL, store an indication of whether all callbacks are lazy.
  * (If there are no callbacks, all of them are deemed to be lazy.)
  */
-static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
+static int __maybe_unused rcu_cpu_has_callbacks(bool *all_lazy)
 {
 	bool al = true;
 	bool hc = false;
@@ -3166,7 +3179,7 @@ static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
 	struct rcu_state *rsp;
 
 	for_each_rcu_flavor(rsp) {
-		rdp = per_cpu_ptr(rsp->rda, cpu);
+		rdp = this_cpu_ptr(rsp->rda);
 		if (!rdp->nxtlist)
 			continue;
 		hc = true;
@@ -3485,8 +3498,10 @@ static int rcu_cpu_notify(struct notifier_block *self,
 	case CPU_DEAD_FROZEN:
 	case CPU_UP_CANCELED:
 	case CPU_UP_CANCELED_FROZEN:
-		for_each_rcu_flavor(rsp)
+		for_each_rcu_flavor(rsp) {
 			rcu_cleanup_dead_cpu(cpu, rsp);
+			do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu));
+		}
 		break;
 	default:
 		break;
@@ -3766,6 +3781,8 @@ void __init rcu_init(void)
 	pm_notifier(rcu_pm_notify, 0);
 	for_each_online_cpu(cpu)
 		rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
+
+	rcu_early_boot_tests();
 }
 
 #include "tree_plugin.h"
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index bbdc45d8d74f..8e7b1843896e 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -139,7 +139,7 @@ struct rcu_node {
 	unsigned long expmask;	/* Groups that have ->blkd_tasks */
 				/*  elements that need to drain to allow the */
 				/*  current expedited grace period to */
-				/*  complete (only for TREE_PREEMPT_RCU). */
+				/*  complete (only for PREEMPT_RCU). */
 	unsigned long qsmaskinit;
 				/* Per-GP initial value for qsmask & expmask. */
 	unsigned long grpmask;	/* Mask to apply to parent qsmask. */
@@ -530,10 +530,10 @@ DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
 extern struct rcu_state rcu_bh_state;
 DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
 
-#ifdef CONFIG_TREE_PREEMPT_RCU
+#ifdef CONFIG_PREEMPT_RCU
 extern struct rcu_state rcu_preempt_state;
 DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
-#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
 
 #ifdef CONFIG_RCU_BOOST
 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
@@ -547,7 +547,7 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work);
 /* Forward declarations for rcutree_plugin.h */
 static void rcu_bootup_announce(void);
 long rcu_batches_completed(void);
-static void rcu_preempt_note_context_switch(int cpu);
+static void rcu_preempt_note_context_switch(void);
 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 #ifdef CONFIG_HOTPLUG_CPU
 static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
@@ -561,12 +561,12 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
 				     struct rcu_node *rnp,
 				     struct rcu_data *rdp);
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
-static void rcu_preempt_check_callbacks(int cpu);
+static void rcu_preempt_check_callbacks(void);
 void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
-#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU)
 static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
 			       bool wake);
-#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
+#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU) */
 static void __init __rcu_init_preempt(void);
 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
@@ -579,8 +579,8 @@ static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 #endif /* #ifdef CONFIG_RCU_BOOST */
 static void __init rcu_spawn_boost_kthreads(void);
 static void rcu_prepare_kthreads(int cpu);
-static void rcu_cleanup_after_idle(int cpu);
-static void rcu_prepare_for_idle(int cpu);
+static void rcu_cleanup_after_idle(void);
+static void rcu_prepare_for_idle(void);
 static void rcu_idle_count_callbacks_posted(void);
 static void print_cpu_stall_info_begin(void);
 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
@@ -606,8 +606,8 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 static void __maybe_unused rcu_kick_nohz_cpu(int cpu);
 static bool init_nocb_callback_list(struct rcu_data *rdp);
-static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq);
-static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq);
+static void rcu_sysidle_enter(int irq);
+static void rcu_sysidle_exit(int irq);
 static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
 				  unsigned long *maxj);
 static bool is_sysidle_rcu_state(struct rcu_state *rsp);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c1d7f27bd38f..3ec85cb5d544 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -30,14 +30,24 @@
 #include <linux/smpboot.h>
 #include "../time/tick-internal.h"
 
-#define RCU_KTHREAD_PRIO 1
-
 #ifdef CONFIG_RCU_BOOST
+
 #include "../locking/rtmutex_common.h"
-#define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO
-#else
-#define RCU_BOOST_PRIO RCU_KTHREAD_PRIO
-#endif
+
+/* rcuc/rcub kthread realtime priority */
+static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
+module_param(kthread_prio, int, 0644);
+
+/*
+ * 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(unsigned int, rcu_cpu_kthread_loops);
+DEFINE_PER_CPU(char, rcu_cpu_has_work);
+
+#endif /* #ifdef CONFIG_RCU_BOOST */
 
 #ifdef CONFIG_RCU_NOCB_CPU
 static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
@@ -72,9 +82,6 @@ static void __init rcu_bootup_announce_oddness(void)
 #ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE
 	pr_info("\tRCU torture testing starts during boot.\n");
 #endif
-#if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE)
-	pr_info("\tDump stacks of tasks blocking RCU-preempt GP.\n");
-#endif
 #if defined(CONFIG_RCU_CPU_STALL_INFO)
 	pr_info("\tAdditional per-CPU info printed with stalls.\n");
 #endif
@@ -85,9 +92,12 @@ static void __init rcu_bootup_announce_oddness(void)
 		pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
 	if (nr_cpu_ids != NR_CPUS)
 		pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
+#ifdef CONFIG_RCU_BOOST
+	pr_info("\tRCU kthread priority: %d.\n", kthread_prio);
+#endif
 }
 
-#ifdef CONFIG_TREE_PREEMPT_RCU
+#ifdef CONFIG_PREEMPT_RCU
 
 RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu);
 static struct rcu_state *rcu_state_p = &rcu_preempt_state;
@@ -156,7 +166,7 @@ static void rcu_preempt_qs(void)
  *
  * Caller must disable preemption.
  */
-static void rcu_preempt_note_context_switch(int cpu)
+static void rcu_preempt_note_context_switch(void)
 {
 	struct task_struct *t = current;
 	unsigned long flags;
@@ -167,7 +177,7 @@ static void rcu_preempt_note_context_switch(int cpu)
 	    !t->rcu_read_unlock_special.b.blocked) {
 
 		/* Possibly blocking in an RCU read-side critical section. */
-		rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu);
+		rdp = this_cpu_ptr(rcu_preempt_state.rda);
 		rnp = rdp->mynode;
 		raw_spin_lock_irqsave(&rnp->lock, flags);
 		smp_mb__after_unlock_lock();
@@ -415,8 +425,6 @@ void rcu_read_unlock_special(struct task_struct *t)
 	}
 }
 
-#ifdef CONFIG_RCU_CPU_STALL_VERBOSE
-
 /*
  * Dump detailed information for all tasks blocking the current RCU
  * grace period on the specified rcu_node structure.
@@ -451,14 +459,6 @@ static void rcu_print_detail_task_stall(struct rcu_state *rsp)
 		rcu_print_detail_task_stall_rnp(rnp);
 }
 
-#else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */
-
-static void rcu_print_detail_task_stall(struct rcu_state *rsp)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */
-
 #ifdef CONFIG_RCU_CPU_STALL_INFO
 
 static void rcu_print_task_stall_begin(struct rcu_node *rnp)
@@ -621,7 +621,7 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
  *
  * Caller must disable hard irqs.
  */
-static void rcu_preempt_check_callbacks(int cpu)
+static void rcu_preempt_check_callbacks(void)
 {
 	struct task_struct *t = current;
 
@@ -630,8 +630,8 @@ static void rcu_preempt_check_callbacks(int cpu)
 		return;
 	}
 	if (t->rcu_read_lock_nesting > 0 &&
-	    per_cpu(rcu_preempt_data, cpu).qs_pending &&
-	    !per_cpu(rcu_preempt_data, cpu).passed_quiesce)
+	    __this_cpu_read(rcu_preempt_data.qs_pending) &&
+	    !__this_cpu_read(rcu_preempt_data.passed_quiesce))
 		t->rcu_read_unlock_special.b.need_qs = true;
 }
 
@@ -919,7 +919,7 @@ void exit_rcu(void)
 	__rcu_read_unlock();
 }
 
-#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+#else /* #ifdef CONFIG_PREEMPT_RCU */
 
 static struct rcu_state *rcu_state_p = &rcu_sched_state;
 
@@ -945,7 +945,7 @@ EXPORT_SYMBOL_GPL(rcu_batches_completed);
  * Because preemptible RCU does not exist, we never have to check for
  * CPUs being in quiescent states.
  */
-static void rcu_preempt_note_context_switch(int cpu)
+static void rcu_preempt_note_context_switch(void)
 {
 }
 
@@ -1017,7 +1017,7 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
  * Because preemptible RCU does not exist, it never has any callbacks
  * to check.
  */
-static void rcu_preempt_check_callbacks(int cpu)
+static void rcu_preempt_check_callbacks(void)
 {
 }
 
@@ -1070,7 +1070,7 @@ void exit_rcu(void)
 {
 }
 
-#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
+#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
 
 #ifdef CONFIG_RCU_BOOST
 
@@ -1326,7 +1326,7 @@ static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 	smp_mb__after_unlock_lock();
 	rnp->boost_kthread_task = t;
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
-	sp.sched_priority = RCU_BOOST_PRIO;
+	sp.sched_priority = kthread_prio;
 	sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
 	wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
 	return 0;
@@ -1343,7 +1343,7 @@ static void rcu_cpu_kthread_setup(unsigned int cpu)
 {
 	struct sched_param sp;
 
-	sp.sched_priority = RCU_KTHREAD_PRIO;
+	sp.sched_priority = kthread_prio;
 	sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
 }
 
@@ -1512,10 +1512,10 @@ static void rcu_prepare_kthreads(int cpu)
  * any flavor of RCU.
  */
 #ifndef CONFIG_RCU_NOCB_CPU_ALL
-int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
+int rcu_needs_cpu(unsigned long *delta_jiffies)
 {
 	*delta_jiffies = ULONG_MAX;
-	return rcu_cpu_has_callbacks(cpu, NULL);
+	return rcu_cpu_has_callbacks(NULL);
 }
 #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
 
@@ -1523,7 +1523,7 @@ int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
  * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up
  * after it.
  */
-static void rcu_cleanup_after_idle(int cpu)
+static void rcu_cleanup_after_idle(void)
 {
 }
 
@@ -1531,7 +1531,7 @@ static void rcu_cleanup_after_idle(int cpu)
  * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n,
  * is nothing.
  */
-static void rcu_prepare_for_idle(int cpu)
+static void rcu_prepare_for_idle(void)
 {
 }
 
@@ -1624,15 +1624,15 @@ static bool __maybe_unused rcu_try_advance_all_cbs(void)
  * The caller must have disabled interrupts.
  */
 #ifndef CONFIG_RCU_NOCB_CPU_ALL
-int rcu_needs_cpu(int cpu, unsigned long *dj)
+int rcu_needs_cpu(unsigned long *dj)
 {
-	struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
 
 	/* Snapshot to detect later posting of non-lazy callback. */
 	rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted;
 
 	/* If no callbacks, RCU doesn't need the CPU. */
-	if (!rcu_cpu_has_callbacks(cpu, &rdtp->all_lazy)) {
+	if (!rcu_cpu_has_callbacks(&rdtp->all_lazy)) {
 		*dj = ULONG_MAX;
 		return 0;
 	}
@@ -1666,12 +1666,12 @@ int rcu_needs_cpu(int cpu, unsigned long *dj)
  *
  * The caller must have disabled interrupts.
  */
-static void rcu_prepare_for_idle(int cpu)
+static void rcu_prepare_for_idle(void)
 {
 #ifndef CONFIG_RCU_NOCB_CPU_ALL
 	bool needwake;
 	struct rcu_data *rdp;
-	struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
 	struct rcu_node *rnp;
 	struct rcu_state *rsp;
 	int tne;
@@ -1679,7 +1679,7 @@ static void rcu_prepare_for_idle(int cpu)
 	/* Handle nohz enablement switches conservatively. */
 	tne = ACCESS_ONCE(tick_nohz_active);
 	if (tne != rdtp->tick_nohz_enabled_snap) {
-		if (rcu_cpu_has_callbacks(cpu, NULL))
+		if (rcu_cpu_has_callbacks(NULL))
 			invoke_rcu_core(); /* force nohz to see update. */
 		rdtp->tick_nohz_enabled_snap = tne;
 		return;
@@ -1688,7 +1688,7 @@ static void rcu_prepare_for_idle(int cpu)
 		return;
 
 	/* If this is a no-CBs CPU, no callbacks, just return. */
-	if (rcu_is_nocb_cpu(cpu))
+	if (rcu_is_nocb_cpu(smp_processor_id()))
 		return;
 
 	/*
@@ -1712,7 +1712,7 @@ static void rcu_prepare_for_idle(int cpu)
 		return;
 	rdtp->last_accelerate = jiffies;
 	for_each_rcu_flavor(rsp) {
-		rdp = per_cpu_ptr(rsp->rda, cpu);
+		rdp = this_cpu_ptr(rsp->rda);
 		if (!*rdp->nxttail[RCU_DONE_TAIL])
 			continue;
 		rnp = rdp->mynode;
@@ -1731,10 +1731,10 @@ static void rcu_prepare_for_idle(int cpu)
  * any grace periods that elapsed while the CPU was idle, and if any
  * callbacks are now ready to invoke, initiate invocation.
  */
-static void rcu_cleanup_after_idle(int cpu)
+static void rcu_cleanup_after_idle(void)
 {
 #ifndef CONFIG_RCU_NOCB_CPU_ALL
-	if (rcu_is_nocb_cpu(cpu))
+	if (rcu_is_nocb_cpu(smp_processor_id()))
 		return;
 	if (rcu_try_advance_all_cbs())
 		invoke_rcu_core();
@@ -2573,9 +2573,13 @@ static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu)
 			rdp->nocb_leader = rdp_spawn;
 			if (rdp_last && rdp != rdp_spawn)
 				rdp_last->nocb_next_follower = rdp;
-			rdp_last = rdp;
-			rdp = rdp->nocb_next_follower;
-			rdp_last->nocb_next_follower = NULL;
+			if (rdp == rdp_spawn) {
+				rdp = rdp->nocb_next_follower;
+			} else {
+				rdp_last = rdp;
+				rdp = rdp->nocb_next_follower;
+				rdp_last->nocb_next_follower = NULL;
+			}
 		} while (rdp);
 		rdp_spawn->nocb_next_follower = rdp_old_leader;
 	}
@@ -2761,9 +2765,10 @@ static int full_sysidle_state;		/* Current system-idle state. */
  * to detect full-system idle states, not RCU quiescent states and grace
  * periods.  The caller must have disabled interrupts.
  */
-static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq)
+static void rcu_sysidle_enter(int irq)
 {
 	unsigned long j;
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
 
 	/* If there are no nohz_full= CPUs, no need to track this. */
 	if (!tick_nohz_full_enabled())
@@ -2832,8 +2837,10 @@ void rcu_sysidle_force_exit(void)
  * usermode execution does -not- count as idle here!  The caller must
  * have disabled interrupts.
  */
-static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq)
+static void rcu_sysidle_exit(int irq)
 {
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+
 	/* If there are no nohz_full= CPUs, no need to track this. */
 	if (!tick_nohz_full_enabled())
 		return;
@@ -3127,11 +3134,11 @@ static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp)
 
 #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
 
-static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq)
+static void rcu_sysidle_enter(int irq)
 {
 }
 
-static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq)
+static void rcu_sysidle_exit(int irq)
 {
 }
 
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 3ef8ba58694e..e0d31a345ee6 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -306,7 +306,7 @@ struct debug_obj_descr rcuhead_debug_descr = {
 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
 void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
 			       unsigned long secs,
 			       unsigned long c_old, unsigned long c)
@@ -531,7 +531,8 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 	struct rcu_head *next;
 	LIST_HEAD(rcu_tasks_holdouts);
 
-	/* FIXME: Add housekeeping affinity. */
+	/* Run on housekeeping CPUs by default.  Sysadm can move if desired. */
+	housekeeping_affine(current);
 
 	/*
 	 * Each pass through the following loop makes one check for
@@ -690,3 +691,87 @@ static void rcu_spawn_tasks_kthread(void)
 }
 
 #endif /* #ifdef CONFIG_TASKS_RCU */
+
+#ifdef CONFIG_PROVE_RCU
+
+/*
+ * Early boot self test parameters, one for each flavor
+ */
+static bool rcu_self_test;
+static bool rcu_self_test_bh;
+static bool rcu_self_test_sched;
+
+module_param(rcu_self_test, bool, 0444);
+module_param(rcu_self_test_bh, bool, 0444);
+module_param(rcu_self_test_sched, bool, 0444);
+
+static int rcu_self_test_counter;
+
+static void test_callback(struct rcu_head *r)
+{
+	rcu_self_test_counter++;
+	pr_info("RCU test callback executed %d\n", rcu_self_test_counter);
+}
+
+static void early_boot_test_call_rcu(void)
+{
+	static struct rcu_head head;
+
+	call_rcu(&head, test_callback);
+}
+
+static void early_boot_test_call_rcu_bh(void)
+{
+	static struct rcu_head head;
+
+	call_rcu_bh(&head, test_callback);
+}
+
+static void early_boot_test_call_rcu_sched(void)
+{
+	static struct rcu_head head;
+
+	call_rcu_sched(&head, test_callback);
+}
+
+void rcu_early_boot_tests(void)
+{
+	pr_info("Running RCU self tests\n");
+
+	if (rcu_self_test)
+		early_boot_test_call_rcu();
+	if (rcu_self_test_bh)
+		early_boot_test_call_rcu_bh();
+	if (rcu_self_test_sched)
+		early_boot_test_call_rcu_sched();
+}
+
+static int rcu_verify_early_boot_tests(void)
+{
+	int ret = 0;
+	int early_boot_test_counter = 0;
+
+	if (rcu_self_test) {
+		early_boot_test_counter++;
+		rcu_barrier();
+	}
+	if (rcu_self_test_bh) {
+		early_boot_test_counter++;
+		rcu_barrier_bh();
+	}
+	if (rcu_self_test_sched) {
+		early_boot_test_counter++;
+		rcu_barrier_sched();
+	}
+
+	if (rcu_self_test_counter != early_boot_test_counter) {
+		WARN_ON(1);
+		ret = -1;
+	}
+
+	return ret;
+}
+late_initcall(rcu_verify_early_boot_tests);
+#else
+void rcu_early_boot_tests(void) {}
+#endif /* CONFIG_PROVE_RCU */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 240157c13ddc..05e5c1ebc73b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2802,7 +2802,7 @@ need_resched:
 	preempt_disable();
 	cpu = smp_processor_id();
 	rq = cpu_rq(cpu);
-	rcu_note_context_switch(cpu);
+	rcu_note_context_switch();
 	prev = rq->curr;
 
 	schedule_debug(prev);
diff --git a/kernel/signal.c b/kernel/signal.c
index 8f0876f9f6dd..19e35135fc60 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1275,7 +1275,17 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
 			local_irq_restore(*flags);
 			break;
 		}
-
+		/*
+		 * This sighand can be already freed and even reused, but
+		 * we rely on SLAB_DESTROY_BY_RCU and sighand_ctor() which
+		 * initializes ->siglock: this slab can't go away, it has
+		 * the same object type, ->siglock can't be reinitialized.
+		 *
+		 * We need to ensure that tsk->sighand is still the same
+		 * after we take the lock, we can race with de_thread() or
+		 * __exit_signal(). In the latter case the next iteration
+		 * must see ->sighand == NULL.
+		 */
 		spin_lock(&sighand->siglock);
 		if (likely(sighand == tsk->sighand)) {
 			rcu_read_unlock();
@@ -1331,23 +1341,21 @@ int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
 	int error = -ESRCH;
 	struct task_struct *p;
 
-	rcu_read_lock();
-retry:
-	p = pid_task(pid, PIDTYPE_PID);
-	if (p) {
-		error = group_send_sig_info(sig, info, p);
-		if (unlikely(error == -ESRCH))
-			/*
-			 * The task was unhashed in between, try again.
-			 * If it is dead, pid_task() will return NULL,
-			 * if we race with de_thread() it will find the
-			 * new leader.
-			 */
-			goto retry;
-	}
-	rcu_read_unlock();
+	for (;;) {
+		rcu_read_lock();
+		p = pid_task(pid, PIDTYPE_PID);
+		if (p)
+			error = group_send_sig_info(sig, info, p);
+		rcu_read_unlock();
+		if (likely(!p || error != -ESRCH))
+			return error;
 
-	return error;
+		/*
+		 * The task was unhashed in between, try again.  If it
+		 * is dead, pid_task() will return NULL, if we race with
+		 * de_thread() it will find the new leader.
+		 */
+	}
 }
 
 int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 0699add19164..501baa9ac1be 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -656,7 +656,7 @@ static void run_ksoftirqd(unsigned int cpu)
 		 * in the task stack here.
 		 */
 		__do_softirq();
-		rcu_note_context_switch(cpu);
+		rcu_note_context_switch();
 		local_irq_enable();
 		cond_resched();
 		return;
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 7b5741fc4110..1f4356037a7d 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -585,7 +585,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
 		last_jiffies = jiffies;
 	} while (read_seqretry(&jiffies_lock, seq));
 
-	if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
+	if (rcu_needs_cpu(&rcu_delta_jiffies) ||
 	    arch_needs_cpu() || irq_work_needs_cpu()) {
 		next_jiffies = last_jiffies + 1;
 		delta_jiffies = 1;
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 3260ffdb368f..2d3f5c504939 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1377,12 +1377,11 @@ unsigned long get_next_timer_interrupt(unsigned long now)
 void update_process_times(int user_tick)
 {
 	struct task_struct *p = current;
-	int cpu = smp_processor_id();
 
 	/* Note: this timer irq context must be accounted for as well. */
 	account_process_tick(p, user_tick);
 	run_local_timers();
-	rcu_check_callbacks(cpu, user_tick);
+	rcu_check_callbacks(user_tick);
 #ifdef CONFIG_IRQ_WORK
 	if (in_irq())
 		irq_work_tick();