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

Pull RCU changes from Paul E. McKenney:

 - Adding transitivity uniformly to rcu_node structure ->lock
   acquisitions.  (This is implemented by the first two commits
   on top of v4.4-rc2 due to the pervasive nature of this change.)

 - Documentation updates, including RCU requirements.

 - Expedited grace-period changes.

 - Miscellaneous fixes.

 - Linked-list fixes, courtesy of KTSAN.

 - Torture-test updates.

 - Late-breaking fix to sysrq-generated crash.

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

9 files changed, 342 insertions, 217 deletions

diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index e83b26464061..152da4a48867 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -20,7 +20,7 @@
 #include <linux/capability.h>
 #include <linux/compiler.h>
 
-#include <linux/rcupdate.h>	/* rcu_expedited */
+#include <linux/rcupdate.h>	/* rcu_expedited and rcu_normal */
 
 #define KERNEL_ATTR_RO(_name) \
 static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
@@ -144,11 +144,12 @@ static ssize_t fscaps_show(struct kobject *kobj,
 }
 KERNEL_ATTR_RO(fscaps);
 
+#ifndef CONFIG_TINY_RCU
 int rcu_expedited;
 static ssize_t rcu_expedited_show(struct kobject *kobj,
 				  struct kobj_attribute *attr, char *buf)
 {
-	return sprintf(buf, "%d\n", rcu_expedited);
+	return sprintf(buf, "%d\n", READ_ONCE(rcu_expedited));
 }
 static ssize_t rcu_expedited_store(struct kobject *kobj,
 				   struct kobj_attribute *attr,
@@ -161,6 +162,24 @@ static ssize_t rcu_expedited_store(struct kobject *kobj,
 }
 KERNEL_ATTR_RW(rcu_expedited);
 
+int rcu_normal;
+static ssize_t rcu_normal_show(struct kobject *kobj,
+			       struct kobj_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", READ_ONCE(rcu_normal));
+}
+static ssize_t rcu_normal_store(struct kobject *kobj,
+				struct kobj_attribute *attr,
+				const char *buf, size_t count)
+{
+	if (kstrtoint(buf, 0, &rcu_normal))
+		return -EINVAL;
+
+	return count;
+}
+KERNEL_ATTR_RW(rcu_normal);
+#endif /* #ifndef CONFIG_TINY_RCU */
+
 /*
  * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
  */
@@ -202,7 +221,10 @@ static struct attribute * kernel_attrs[] = {
 	&kexec_crash_size_attr.attr,
 	&vmcoreinfo_attr.attr,
 #endif
+#ifndef CONFIG_TINY_RCU
 	&rcu_expedited_attr.attr,
+	&rcu_normal_attr.attr,
+#endif
 	NULL
 };
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index d89328e260df..d2988d047d66 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -162,6 +162,27 @@ static int rcu_torture_writer_state;
 #define RTWS_SYNC		7
 #define RTWS_STUTTER		8
 #define RTWS_STOPPING		9
+static const char * const rcu_torture_writer_state_names[] = {
+	"RTWS_FIXED_DELAY",
+	"RTWS_DELAY",
+	"RTWS_REPLACE",
+	"RTWS_DEF_FREE",
+	"RTWS_EXP_SYNC",
+	"RTWS_COND_GET",
+	"RTWS_COND_SYNC",
+	"RTWS_SYNC",
+	"RTWS_STUTTER",
+	"RTWS_STOPPING",
+};
+
+static const char *rcu_torture_writer_state_getname(void)
+{
+	unsigned int i = READ_ONCE(rcu_torture_writer_state);
+
+	if (i >= ARRAY_SIZE(rcu_torture_writer_state_names))
+		return "???";
+	return rcu_torture_writer_state_names[i];
+}
 
 #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
 #define RCUTORTURE_RUNNABLE_INIT 1
@@ -1307,7 +1328,8 @@ rcu_torture_stats_print(void)
 
 		rcutorture_get_gp_data(cur_ops->ttype,
 				       &flags, &gpnum, &completed);
-		pr_alert("??? Writer stall state %d g%lu c%lu f%#x\n",
+		pr_alert("??? Writer stall state %s(%d) g%lu c%lu f%#x\n",
+			 rcu_torture_writer_state_getname(),
 			 rcu_torture_writer_state,
 			 gpnum, completed, flags);
 		show_rcu_gp_kthreads();
diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index a63a1ea5a41b..9b9cdd549caa 100644
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -489,7 +489,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
  */
 void synchronize_srcu(struct srcu_struct *sp)
 {
-	__synchronize_srcu(sp, rcu_gp_is_expedited()
+	__synchronize_srcu(sp, (rcu_gp_is_expedited() && !rcu_gp_is_normal())
 			   ? SYNCHRONIZE_SRCU_EXP_TRYCOUNT
 			   : SYNCHRONIZE_SRCU_TRYCOUNT);
 }
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index f07343b54fe5..e41dd4131f7a 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -68,10 +68,6 @@ MODULE_ALIAS("rcutree");
 
 /* Data structures. */
 
-static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
-static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
-static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS];
-
 /*
  * In order to export the rcu_state name to the tracing tools, it
  * needs to be added in the __tracepoint_string section.
@@ -246,24 +242,17 @@ static int rcu_gp_in_progress(struct rcu_state *rsp)
  */
 void rcu_sched_qs(void)
 {
-	unsigned long flags;
-
-	if (__this_cpu_read(rcu_sched_data.cpu_no_qs.s)) {
-		trace_rcu_grace_period(TPS("rcu_sched"),
-				       __this_cpu_read(rcu_sched_data.gpnum),
-				       TPS("cpuqs"));
-		__this_cpu_write(rcu_sched_data.cpu_no_qs.b.norm, false);
-		if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))
-			return;
-		local_irq_save(flags);
-		if (__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp)) {
-			__this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, false);
-			rcu_report_exp_rdp(&rcu_sched_state,
-					   this_cpu_ptr(&rcu_sched_data),
-					   true);
-		}
-		local_irq_restore(flags);
-	}
+	if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.s))
+		return;
+	trace_rcu_grace_period(TPS("rcu_sched"),
+			       __this_cpu_read(rcu_sched_data.gpnum),
+			       TPS("cpuqs"));
+	__this_cpu_write(rcu_sched_data.cpu_no_qs.b.norm, false);
+	if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))
+		return;
+	__this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, false);
+	rcu_report_exp_rdp(&rcu_sched_state,
+			   this_cpu_ptr(&rcu_sched_data), true);
 }
 
 void rcu_bh_qs(void)
@@ -300,17 +289,16 @@ EXPORT_PER_CPU_SYMBOL_GPL(rcu_qs_ctr);
  * We inform the RCU core by emulating a zero-duration dyntick-idle
  * period, which we in turn do by incrementing the ->dynticks counter
  * by two.
+ *
+ * The caller must have disabled interrupts.
  */
 static void rcu_momentary_dyntick_idle(void)
 {
-	unsigned long flags;
 	struct rcu_data *rdp;
 	struct rcu_dynticks *rdtp;
 	int resched_mask;
 	struct rcu_state *rsp;
 
-	local_irq_save(flags);
-
 	/*
 	 * Yes, we can lose flag-setting operations.  This is OK, because
 	 * the flag will be set again after some delay.
@@ -340,13 +328,12 @@ static void rcu_momentary_dyntick_idle(void)
 		smp_mb__after_atomic(); /* Later stuff after QS. */
 		break;
 	}
-	local_irq_restore(flags);
 }
 
 /*
  * Note a context switch.  This is a quiescent state for RCU-sched,
  * and requires special handling for preemptible RCU.
- * The caller must have disabled preemption.
+ * The caller must have disabled interrupts.
  */
 void rcu_note_context_switch(void)
 {
@@ -376,9 +363,14 @@ EXPORT_SYMBOL_GPL(rcu_note_context_switch);
  */
 void rcu_all_qs(void)
 {
+	unsigned long flags;
+
 	barrier(); /* Avoid RCU read-side critical sections leaking down. */
-	if (unlikely(raw_cpu_read(rcu_sched_qs_mask)))
+	if (unlikely(raw_cpu_read(rcu_sched_qs_mask))) {
+		local_irq_save(flags);
 		rcu_momentary_dyntick_idle();
+		local_irq_restore(flags);
+	}
 	this_cpu_inc(rcu_qs_ctr);
 	barrier(); /* Avoid RCU read-side critical sections leaking up. */
 }
@@ -605,25 +597,25 @@ static int rcu_future_needs_gp(struct rcu_state *rsp)
  * The caller must have disabled interrupts to prevent races with
  * normal callback registry.
  */
-static int
+static bool
 cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
 {
 	int i;
 
 	if (rcu_gp_in_progress(rsp))
-		return 0;  /* No, a grace period is already in progress. */
+		return false;  /* No, a grace period is already in progress. */
 	if (rcu_future_needs_gp(rsp))
-		return 1;  /* Yes, a no-CBs CPU needs one. */
+		return true;  /* Yes, a no-CBs CPU needs one. */
 	if (!rdp->nxttail[RCU_NEXT_TAIL])
-		return 0;  /* No, this is a no-CBs (or offline) CPU. */
+		return false;  /* No, this is a no-CBs (or offline) CPU. */
 	if (*rdp->nxttail[RCU_NEXT_READY_TAIL])
-		return 1;  /* Yes, this CPU has newly registered callbacks. */
+		return true;  /* Yes, CPU has newly registered callbacks. */
 	for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
 		if (rdp->nxttail[i - 1] != rdp->nxttail[i] &&
 		    ULONG_CMP_LT(READ_ONCE(rsp->completed),
 				 rdp->nxtcompleted[i]))
-			return 1;  /* Yes, CBs for future grace period. */
-	return 0; /* No grace period needed. */
+			return true;  /* Yes, CBs for future grace period. */
+	return false; /* No grace period needed. */
 }
 
 /*
@@ -740,7 +732,7 @@ void rcu_user_enter(void)
  *
  * 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.
+ * sections can occur.  The caller must have disabled interrupts.
  *
  * This code assumes that the idle loop never does anything that might
  * result in unbalanced calls to irq_enter() and irq_exit().  If your
@@ -753,11 +745,10 @@ void rcu_user_enter(void)
  */
 void rcu_irq_exit(void)
 {
-	unsigned long flags;
 	long long oldval;
 	struct rcu_dynticks *rdtp;
 
-	local_irq_save(flags);
+	RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_irq_exit() invoked with irqs enabled!!!");
 	rdtp = this_cpu_ptr(&rcu_dynticks);
 	oldval = rdtp->dynticks_nesting;
 	rdtp->dynticks_nesting--;
@@ -768,6 +759,17 @@ void rcu_irq_exit(void)
 	else
 		rcu_eqs_enter_common(oldval, true);
 	rcu_sysidle_enter(1);
+}
+
+/*
+ * Wrapper for rcu_irq_exit() where interrupts are enabled.
+ */
+void rcu_irq_exit_irqson(void)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	rcu_irq_exit();
 	local_irq_restore(flags);
 }
 
@@ -865,7 +867,7 @@ void rcu_user_exit(void)
  *
  * 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.
+ * sections can occur.  The caller must have disabled interrupts.
  *
  * Note that the Linux kernel is fully capable of entering an interrupt
  * handler that it never exits, for example when doing upcalls to
@@ -881,11 +883,10 @@ void rcu_user_exit(void)
  */
 void rcu_irq_enter(void)
 {
-	unsigned long flags;
 	struct rcu_dynticks *rdtp;
 	long long oldval;
 
-	local_irq_save(flags);
+	RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_irq_enter() invoked with irqs enabled!!!");
 	rdtp = this_cpu_ptr(&rcu_dynticks);
 	oldval = rdtp->dynticks_nesting;
 	rdtp->dynticks_nesting++;
@@ -896,6 +897,17 @@ void rcu_irq_enter(void)
 	else
 		rcu_eqs_exit_common(oldval, true);
 	rcu_sysidle_exit(1);
+}
+
+/*
+ * Wrapper for rcu_irq_enter() where interrupts are enabled.
+ */
+void rcu_irq_enter_irqson(void)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	rcu_irq_enter();
 	local_irq_restore(flags);
 }
 
@@ -1187,6 +1199,16 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
 }
 
 /*
+ * Convert a ->gp_state value to a character string.
+ */
+static const char *gp_state_getname(short gs)
+{
+	if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names))
+		return "???";
+	return gp_state_names[gs];
+}
+
+/*
  * Complain about starvation of grace-period kthread.
  */
 static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
@@ -1196,12 +1218,16 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
 
 	j = jiffies;
 	gpa = READ_ONCE(rsp->gp_activity);
-	if (j - gpa > 2 * HZ)
-		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n",
+	if (j - gpa > 2 * HZ) {
+		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx\n",
 		       rsp->name, j - gpa,
 		       rsp->gpnum, rsp->completed,
-		       rsp->gp_flags, rsp->gp_state,
-		       rsp->gp_kthread ? rsp->gp_kthread->state : 0);
+		       rsp->gp_flags,
+		       gp_state_getname(rsp->gp_state), rsp->gp_state,
+		       rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
+		if (rsp->gp_kthread)
+			sched_show_task(rsp->gp_kthread);
+	}
 }
 
 /*
@@ -1214,7 +1240,7 @@ static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
 	struct rcu_node *rnp;
 
 	rcu_for_each_leaf_node(rsp, rnp) {
-		raw_spin_lock_irqsave(&rnp->lock, flags);
+		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		if (rnp->qsmask != 0) {
 			for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
 				if (rnp->qsmask & (1UL << cpu))
@@ -1237,7 +1263,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
 
 	/* Only let one CPU complain about others per time interval. */
 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	delta = jiffies - READ_ONCE(rsp->jiffies_stall);
 	if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
@@ -1256,7 +1282,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
 	       rsp->name);
 	print_cpu_stall_info_begin();
 	rcu_for_each_leaf_node(rsp, rnp) {
-		raw_spin_lock_irqsave(&rnp->lock, flags);
+		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		ndetected += rcu_print_task_stall(rnp);
 		if (rnp->qsmask != 0) {
 			for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
@@ -1327,7 +1353,7 @@ static void print_cpu_stall(struct rcu_state *rsp)
 
 	rcu_dump_cpu_stacks(rsp);
 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	if (ULONG_CMP_GE(jiffies, READ_ONCE(rsp->jiffies_stall)))
 		WRITE_ONCE(rsp->jiffies_stall,
 			   jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
@@ -1534,10 +1560,8 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
 	 * hold it, acquire the root rcu_node structure's lock in order to
 	 * start one (if needed).
 	 */
-	if (rnp != rnp_root) {
-		raw_spin_lock(&rnp_root->lock);
-		smp_mb__after_unlock_lock();
-	}
+	if (rnp != rnp_root)
+		raw_spin_lock_rcu_node(rnp_root);
 
 	/*
 	 * Get a new grace-period number.  If there really is no grace
@@ -1786,11 +1810,10 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
 	if ((rdp->gpnum == READ_ONCE(rnp->gpnum) &&
 	     rdp->completed == READ_ONCE(rnp->completed) &&
 	     !unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */
-	    !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
+	    !raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */
 		local_irq_restore(flags);
 		return;
 	}
-	smp_mb__after_unlock_lock();
 	needwake = __note_gp_changes(rsp, rnp, rdp);
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
 	if (needwake)
@@ -1805,21 +1828,20 @@ static void rcu_gp_slow(struct rcu_state *rsp, int delay)
 }
 
 /*
- * Initialize a new grace period.  Return 0 if no grace period required.
+ * Initialize a new grace period.  Return false if no grace period required.
  */
-static int rcu_gp_init(struct rcu_state *rsp)
+static bool rcu_gp_init(struct rcu_state *rsp)
 {
 	unsigned long oldmask;
 	struct rcu_data *rdp;
 	struct rcu_node *rnp = rcu_get_root(rsp);
 
 	WRITE_ONCE(rsp->gp_activity, jiffies);
-	raw_spin_lock_irq(&rnp->lock);
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_irq_rcu_node(rnp);
 	if (!READ_ONCE(rsp->gp_flags)) {
 		/* Spurious wakeup, tell caller to go back to sleep.  */
 		raw_spin_unlock_irq(&rnp->lock);
-		return 0;
+		return false;
 	}
 	WRITE_ONCE(rsp->gp_flags, 0); /* Clear all flags: New grace period. */
 
@@ -1829,7 +1851,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
 		 * Not supposed to be able to happen.
 		 */
 		raw_spin_unlock_irq(&rnp->lock);
-		return 0;
+		return false;
 	}
 
 	/* Advance to a new grace period and initialize state. */
@@ -1847,8 +1869,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
 	 */
 	rcu_for_each_leaf_node(rsp, rnp) {
 		rcu_gp_slow(rsp, gp_preinit_delay);
-		raw_spin_lock_irq(&rnp->lock);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_irq_rcu_node(rnp);
 		if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
 		    !rnp->wait_blkd_tasks) {
 			/* Nothing to do on this leaf rcu_node structure. */
@@ -1904,8 +1925,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
 	 */
 	rcu_for_each_node_breadth_first(rsp, rnp) {
 		rcu_gp_slow(rsp, gp_init_delay);
-		raw_spin_lock_irq(&rnp->lock);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_irq_rcu_node(rnp);
 		rdp = this_cpu_ptr(rsp->rda);
 		rcu_preempt_check_blocked_tasks(rnp);
 		rnp->qsmask = rnp->qsmaskinit;
@@ -1923,7 +1943,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
 		WRITE_ONCE(rsp->gp_activity, jiffies);
 	}
 
-	return 1;
+	return true;
 }
 
 /*
@@ -1973,8 +1993,7 @@ static void rcu_gp_fqs(struct rcu_state *rsp, bool first_time)
 	}
 	/* Clear flag to prevent immediate re-entry. */
 	if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
-		raw_spin_lock_irq(&rnp->lock);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_irq_rcu_node(rnp);
 		WRITE_ONCE(rsp->gp_flags,
 			   READ_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS);
 		raw_spin_unlock_irq(&rnp->lock);
@@ -1993,8 +2012,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
 	struct rcu_node *rnp = rcu_get_root(rsp);
 
 	WRITE_ONCE(rsp->gp_activity, jiffies);
-	raw_spin_lock_irq(&rnp->lock);
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_irq_rcu_node(rnp);
 	gp_duration = jiffies - rsp->gp_start;
 	if (gp_duration > rsp->gp_max)
 		rsp->gp_max = gp_duration;
@@ -2019,8 +2037,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
 	 * grace period is recorded in any of the rcu_node structures.
 	 */
 	rcu_for_each_node_breadth_first(rsp, rnp) {
-		raw_spin_lock_irq(&rnp->lock);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_irq_rcu_node(rnp);
 		WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
 		WARN_ON_ONCE(rnp->qsmask);
 		WRITE_ONCE(rnp->completed, rsp->gpnum);
@@ -2035,8 +2052,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
 		rcu_gp_slow(rsp, gp_cleanup_delay);
 	}
 	rnp = rcu_get_root(rsp);
-	raw_spin_lock_irq(&rnp->lock);
-	smp_mb__after_unlock_lock(); /* Order GP before ->completed update. */
+	raw_spin_lock_irq_rcu_node(rnp); /* Order GP before ->completed update. */
 	rcu_nocb_gp_set(rnp, nocb);
 
 	/* Declare grace period done. */
@@ -2284,8 +2300,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
 		rnp_c = rnp;
 		rnp = rnp->parent;
-		raw_spin_lock_irqsave(&rnp->lock, flags);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		oldmask = rnp_c->qsmask;
 	}
 
@@ -2332,8 +2347,7 @@ static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
 	gps = rnp->gpnum;
 	mask = rnp->grpmask;
 	raw_spin_unlock(&rnp->lock);	/* irqs remain disabled. */
-	raw_spin_lock(&rnp_p->lock);	/* irqs already disabled. */
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_rcu_node(rnp_p);	/* irqs already disabled. */
 	rcu_report_qs_rnp(mask, rsp, rnp_p, gps, flags);
 }
 
@@ -2355,8 +2369,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
 	struct rcu_node *rnp;
 
 	rnp = rdp->mynode;
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	if ((rdp->cpu_no_qs.b.norm &&
 	     rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) ||
 	    rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum ||
@@ -2582,8 +2595,7 @@ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
 		rnp = rnp->parent;
 		if (!rnp)
 			break;
-		raw_spin_lock(&rnp->lock); /* irqs already disabled. */
-		smp_mb__after_unlock_lock(); /* GP memory ordering. */
+		raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
 		rnp->qsmaskinit &= ~mask;
 		rnp->qsmask &= ~mask;
 		if (rnp->qsmaskinit) {
@@ -2611,8 +2623,7 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
 
 	/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
 	mask = rdp->grpmask;
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	smp_mb__after_unlock_lock();	/* Enforce GP memory-order guarantee. */
+	raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
 	rnp->qsmaskinitnext &= ~mask;
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
 }
@@ -2809,8 +2820,7 @@ static void force_qs_rnp(struct rcu_state *rsp,
 	rcu_for_each_leaf_node(rsp, rnp) {
 		cond_resched_rcu_qs();
 		mask = 0;
-		raw_spin_lock_irqsave(&rnp->lock, flags);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		if (rnp->qsmask == 0) {
 			if (rcu_state_p == &rcu_sched_state ||
 			    rsp != rcu_state_p ||
@@ -2881,8 +2891,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
 	/* rnp_old == rcu_get_root(rsp), rnp == NULL. */
 
 	/* Reached the root of the rcu_node tree, acquire lock. */
-	raw_spin_lock_irqsave(&rnp_old->lock, flags);
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_irqsave_rcu_node(rnp_old, flags);
 	raw_spin_unlock(&rnp_old->fqslock);
 	if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
 		rsp->n_force_qs_lh++;
@@ -2914,7 +2923,7 @@ __rcu_process_callbacks(struct rcu_state *rsp)
 	/* Does this CPU require a not-yet-started grace period? */
 	local_irq_save(flags);
 	if (cpu_needs_another_gp(rsp, rdp)) {
-		raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */
+		raw_spin_lock_rcu_node(rcu_get_root(rsp)); /* irqs disabled. */
 		needwake = rcu_start_gp(rsp);
 		raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
 		if (needwake)
@@ -3005,8 +3014,7 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
 		if (!rcu_gp_in_progress(rsp)) {
 			struct rcu_node *rnp_root = rcu_get_root(rsp);
 
-			raw_spin_lock(&rnp_root->lock);
-			smp_mb__after_unlock_lock();
+			raw_spin_lock_rcu_node(rnp_root);
 			needwake = rcu_start_gp(rsp);
 			raw_spin_unlock(&rnp_root->lock);
 			if (needwake)
@@ -3365,7 +3373,6 @@ static unsigned long rcu_seq_snap(unsigned long *sp)
 {
 	unsigned long s;
 
-	smp_mb(); /* Caller's modifications seen first by other CPUs. */
 	s = (READ_ONCE(*sp) + 3) & ~0x1;
 	smp_mb(); /* Above access must not bleed into critical section. */
 	return s;
@@ -3392,6 +3399,7 @@ static void rcu_exp_gp_seq_end(struct rcu_state *rsp)
 }
 static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
 {
+	smp_mb(); /* Caller's modifications seen first by other CPUs. */
 	return rcu_seq_snap(&rsp->expedited_sequence);
 }
 static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
@@ -3426,8 +3434,7 @@ static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp)
 	 * CPUs for the current rcu_node structure up the rcu_node tree.
 	 */
 	rcu_for_each_leaf_node(rsp, rnp) {
-		raw_spin_lock_irqsave(&rnp->lock, flags);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		if (rnp->expmaskinit == rnp->expmaskinitnext) {
 			raw_spin_unlock_irqrestore(&rnp->lock, flags);
 			continue;  /* No new CPUs, nothing to do. */
@@ -3447,8 +3454,7 @@ static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp)
 		rnp_up = rnp->parent;
 		done = false;
 		while (rnp_up) {
-			raw_spin_lock_irqsave(&rnp_up->lock, flags);
-			smp_mb__after_unlock_lock();
+			raw_spin_lock_irqsave_rcu_node(rnp_up, flags);
 			if (rnp_up->expmaskinit)
 				done = true;
 			rnp_up->expmaskinit |= mask;
@@ -3472,8 +3478,7 @@ static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp)
 
 	sync_exp_reset_tree_hotplug(rsp);
 	rcu_for_each_node_breadth_first(rsp, rnp) {
-		raw_spin_lock_irqsave(&rnp->lock, flags);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		WARN_ON_ONCE(rnp->expmask);
 		rnp->expmask = rnp->expmaskinit;
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
@@ -3531,8 +3536,7 @@ static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
 		mask = rnp->grpmask;
 		raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
 		rnp = rnp->parent;
-		raw_spin_lock(&rnp->lock); /* irqs already disabled */
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_rcu_node(rnp); /* irqs already disabled */
 		WARN_ON_ONCE(!(rnp->expmask & mask));
 		rnp->expmask &= ~mask;
 	}
@@ -3549,8 +3553,7 @@ static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
 {
 	unsigned long flags;
 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	__rcu_report_exp_rnp(rsp, rnp, wake, flags);
 }
 
@@ -3564,8 +3567,7 @@ static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
 {
 	unsigned long flags;
 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	if (!(rnp->expmask & mask)) {
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
 		return;
@@ -3609,7 +3611,7 @@ static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp,
  */
 static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
 {
-	struct rcu_data *rdp;
+	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id());
 	struct rcu_node *rnp0;
 	struct rcu_node *rnp1 = NULL;
 
@@ -3623,7 +3625,7 @@ static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
 	if (!mutex_is_locked(&rnp0->exp_funnel_mutex)) {
 		if (mutex_trylock(&rnp0->exp_funnel_mutex)) {
 			if (sync_exp_work_done(rsp, rnp0, NULL,
-					       &rsp->expedited_workdone0, s))
+					       &rdp->expedited_workdone0, s))
 				return NULL;
 			return rnp0;
 		}
@@ -3637,14 +3639,13 @@ static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
 	 * can be inexact, as it is just promoting locality and is not
 	 * strictly needed for correctness.
 	 */
-	rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id());
-	if (sync_exp_work_done(rsp, NULL, NULL, &rsp->expedited_workdone1, s))
+	if (sync_exp_work_done(rsp, NULL, NULL, &rdp->expedited_workdone1, s))
 		return NULL;
 	mutex_lock(&rdp->exp_funnel_mutex);
 	rnp0 = rdp->mynode;
 	for (; rnp0 != NULL; rnp0 = rnp0->parent) {
 		if (sync_exp_work_done(rsp, rnp1, rdp,
-				       &rsp->expedited_workdone2, s))
+				       &rdp->expedited_workdone2, s))
 			return NULL;
 		mutex_lock(&rnp0->exp_funnel_mutex);
 		if (rnp1)
@@ -3654,7 +3655,7 @@ static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
 		rnp1 = rnp0;
 	}
 	if (sync_exp_work_done(rsp, rnp1, rdp,
-			       &rsp->expedited_workdone3, s))
+			       &rdp->expedited_workdone3, s))
 		return NULL;
 	return rnp1;
 }
@@ -3708,8 +3709,7 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
 
 	sync_exp_reset_tree(rsp);
 	rcu_for_each_leaf_node(rsp, rnp) {
-		raw_spin_lock_irqsave(&rnp->lock, flags);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 
 		/* Each pass checks a CPU for identity, offline, and idle. */
 		mask_ofl_test = 0;
@@ -3741,24 +3741,22 @@ retry_ipi:
 			ret = smp_call_function_single(cpu, func, rsp, 0);
 			if (!ret) {
 				mask_ofl_ipi &= ~mask;
-			} else {
-				/* Failed, raced with offline. */
-				raw_spin_lock_irqsave(&rnp->lock, flags);
-				if (cpu_online(cpu) &&
-				    (rnp->expmask & mask)) {
-					raw_spin_unlock_irqrestore(&rnp->lock,
-								   flags);
-					schedule_timeout_uninterruptible(1);
-					if (cpu_online(cpu) &&
-					    (rnp->expmask & mask))
-						goto retry_ipi;
-					raw_spin_lock_irqsave(&rnp->lock,
-							      flags);
-				}
-				if (!(rnp->expmask & mask))
-					mask_ofl_ipi &= ~mask;
+				continue;
+			}
+			/* Failed, raced with offline. */
+			raw_spin_lock_irqsave_rcu_node(rnp, flags);
+			if (cpu_online(cpu) &&
+			    (rnp->expmask & mask)) {
 				raw_spin_unlock_irqrestore(&rnp->lock, flags);
+				schedule_timeout_uninterruptible(1);
+				if (cpu_online(cpu) &&
+				    (rnp->expmask & mask))
+					goto retry_ipi;
+				raw_spin_lock_irqsave_rcu_node(rnp, flags);
 			}
+			if (!(rnp->expmask & mask))
+				mask_ofl_ipi &= ~mask;
+			raw_spin_unlock_irqrestore(&rnp->lock, flags);
 		}
 		/* Report quiescent states for those that went offline. */
 		mask_ofl_test |= mask_ofl_ipi;
@@ -3773,6 +3771,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
 	unsigned long jiffies_stall;
 	unsigned long jiffies_start;
 	unsigned long mask;
+	int ndetected;
 	struct rcu_node *rnp;
 	struct rcu_node *rnp_root = rcu_get_root(rsp);
 	int ret;
@@ -3785,7 +3784,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
 				rsp->expedited_wq,
 				sync_rcu_preempt_exp_done(rnp_root),
 				jiffies_stall);
-		if (ret > 0)
+		if (ret > 0 || sync_rcu_preempt_exp_done(rnp_root))
 			return;
 		if (ret < 0) {
 			/* Hit a signal, disable CPU stall warnings. */
@@ -3795,14 +3794,16 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
 		}
 		pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {",
 		       rsp->name);
+		ndetected = 0;
 		rcu_for_each_leaf_node(rsp, rnp) {
-			(void)rcu_print_task_exp_stall(rnp);
+			ndetected = rcu_print_task_exp_stall(rnp);
 			mask = 1;
 			for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) {
 				struct rcu_data *rdp;
 
 				if (!(rnp->expmask & mask))
 					continue;
+				ndetected++;
 				rdp = per_cpu_ptr(rsp->rda, cpu);
 				pr_cont(" %d-%c%c%c", cpu,
 					"O."[cpu_online(cpu)],
@@ -3811,8 +3812,23 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
 			}
 			mask <<= 1;
 		}
-		pr_cont(" } %lu jiffies s: %lu\n",
-			jiffies - jiffies_start, rsp->expedited_sequence);
+		pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",
+			jiffies - jiffies_start, rsp->expedited_sequence,
+			rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]);
+		if (!ndetected) {
+			pr_err("blocking rcu_node structures:");
+			rcu_for_each_node_breadth_first(rsp, rnp) {
+				if (rnp == rnp_root)
+					continue; /* printed unconditionally */
+				if (sync_rcu_preempt_exp_done(rnp))
+					continue;
+				pr_cont(" l=%u:%d-%d:%#lx/%c",
+					rnp->level, rnp->grplo, rnp->grphi,
+					rnp->expmask,
+					".T"[!!rnp->exp_tasks]);
+			}
+			pr_cont("\n");
+		}
 		rcu_for_each_leaf_node(rsp, rnp) {
 			mask = 1;
 			for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) {
@@ -3847,6 +3863,16 @@ void synchronize_sched_expedited(void)
 	struct rcu_node *rnp;
 	struct rcu_state *rsp = &rcu_sched_state;
 
+	/* If only one CPU, this is automatically a grace period. */
+	if (rcu_blocking_is_gp())
+		return;
+
+	/* If expedited grace periods are prohibited, fall back to normal. */
+	if (rcu_gp_is_normal()) {
+		wait_rcu_gp(call_rcu_sched);
+		return;
+	}
+
 	/* Take a snapshot of the sequence number.  */
 	s = rcu_exp_gp_seq_snap(rsp);
 
@@ -4135,7 +4161,7 @@ static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
 		rnp = rnp->parent;
 		if (rnp == NULL)
 			return;
-		raw_spin_lock(&rnp->lock); /* Interrupts already disabled. */
+		raw_spin_lock_rcu_node(rnp); /* Interrupts already disabled. */
 		rnp->qsmaskinit |= mask;
 		raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
 	}
@@ -4152,7 +4178,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
 	struct rcu_node *rnp = rcu_get_root(rsp);
 
 	/* Set up local state, ensuring consistent view of global state. */
-	raw_spin_lock_irqsave(&rnp->lock, flags);
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
 	rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
 	WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
@@ -4179,7 +4205,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
 	struct rcu_node *rnp = rcu_get_root(rsp);
 
 	/* Set up local state, ensuring consistent view of global state. */
-	raw_spin_lock_irqsave(&rnp->lock, flags);
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	rdp->qlen_last_fqs_check = 0;
 	rdp->n_force_qs_snap = rsp->n_force_qs;
 	rdp->blimit = blimit;
@@ -4198,8 +4224,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
 	 */
 	rnp = rdp->mynode;
 	mask = rdp->grpmask;
-	raw_spin_lock(&rnp->lock);		/* irqs already disabled. */
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_rcu_node(rnp);		/* irqs already disabled. */
 	rnp->qsmaskinitnext |= mask;
 	rnp->expmaskinitnext |= mask;
 	if (!rdp->beenonline)
@@ -4327,14 +4352,14 @@ static int __init rcu_spawn_gp_kthread(void)
 		t = kthread_create(rcu_gp_kthread, rsp, "%s", rsp->name);
 		BUG_ON(IS_ERR(t));
 		rnp = rcu_get_root(rsp);
-		raw_spin_lock_irqsave(&rnp->lock, flags);
+		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		rsp->gp_kthread = t;
 		if (kthread_prio) {
 			sp.sched_priority = kthread_prio;
 			sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
 		}
-		wake_up_process(t);
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+		wake_up_process(t);
 	}
 	rcu_spawn_nocb_kthreads();
 	rcu_spawn_boost_kthreads();
@@ -4385,12 +4410,14 @@ static void __init rcu_init_levelspread(int *levelspread, const int *levelcnt)
 /*
  * Helper function for rcu_init() that initializes one rcu_state structure.
  */
-static void __init rcu_init_one(struct rcu_state *rsp,
-		struct rcu_data __percpu *rda)
+static void __init rcu_init_one(struct rcu_state *rsp)
 {
 	static const char * const buf[] = RCU_NODE_NAME_INIT;
 	static const char * const fqs[] = RCU_FQS_NAME_INIT;
 	static const char * const exp[] = RCU_EXP_NAME_INIT;
+	static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
+	static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
+	static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS];
 	static u8 fl_mask = 0x1;
 
 	int levelcnt[RCU_NUM_LVLS];		/* # nodes in each level. */
@@ -4576,8 +4603,8 @@ void __init rcu_init(void)
 
 	rcu_bootup_announce();
 	rcu_init_geometry();
-	rcu_init_one(&rcu_bh_state, &rcu_bh_data);
-	rcu_init_one(&rcu_sched_state, &rcu_sched_data);
+	rcu_init_one(&rcu_bh_state);
+	rcu_init_one(&rcu_sched_state);
 	if (dump_tree)
 		rcu_dump_rcu_node_tree(&rcu_sched_state);
 	__rcu_init_preempt();
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 9fb4e238d4dc..83360b4f4352 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -178,6 +178,8 @@ struct rcu_node {
 				/*  beginning of each expedited GP. */
 	unsigned long expmaskinitnext;
 				/* Online CPUs for next expedited GP. */
+				/*  Any CPU that has ever been online will */
+				/*  have its bit set. */
 	unsigned long grpmask;	/* Mask to apply to parent qsmask. */
 				/*  Only one bit will be set in this mask. */
 	int	grplo;		/* lowest-numbered CPU or group here. */
@@ -384,6 +386,10 @@ struct rcu_data {
 	struct rcu_head oom_head;
 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 	struct mutex exp_funnel_mutex;
+	atomic_long_t expedited_workdone0;	/* # done by others #0. */
+	atomic_long_t expedited_workdone1;	/* # done by others #1. */
+	atomic_long_t expedited_workdone2;	/* # done by others #2. */
+	atomic_long_t expedited_workdone3;	/* # done by others #3. */
 
 	/* 7) Callback offloading. */
 #ifdef CONFIG_RCU_NOCB_CPU
@@ -498,10 +504,6 @@ struct rcu_state {
 	/* End of fields guarded by barrier_mutex. */
 
 	unsigned long expedited_sequence;	/* Take a ticket. */
-	atomic_long_t expedited_workdone0;	/* # done by others #0. */
-	atomic_long_t expedited_workdone1;	/* # done by others #1. */
-	atomic_long_t expedited_workdone2;	/* # done by others #2. */
-	atomic_long_t expedited_workdone3;	/* # done by others #3. */
 	atomic_long_t expedited_normal;		/* # fallbacks to normal. */
 	atomic_t expedited_need_qs;		/* # CPUs left to check in. */
 	wait_queue_head_t expedited_wq;		/* Wait for check-ins. */
@@ -545,6 +547,18 @@ struct rcu_state {
 #define RCU_GP_CLEANUP   5	/* Grace-period cleanup started. */
 #define RCU_GP_CLEANED   6	/* Grace-period cleanup complete. */
 
+#ifndef RCU_TREE_NONCORE
+static const char * const gp_state_names[] = {
+	"RCU_GP_IDLE",
+	"RCU_GP_WAIT_GPS",
+	"RCU_GP_DONE_GPS",
+	"RCU_GP_WAIT_FQS",
+	"RCU_GP_DOING_FQS",
+	"RCU_GP_CLEANUP",
+	"RCU_GP_CLEANED",
+};
+#endif /* #ifndef RCU_TREE_NONCORE */
+
 extern struct list_head rcu_struct_flavors;
 
 /* Sequence through rcu_state structures for each RCU flavor. */
@@ -664,3 +678,42 @@ static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
 #else /* #ifdef CONFIG_PPC */
 #define smp_mb__after_unlock_lock()	do { } while (0)
 #endif /* #else #ifdef CONFIG_PPC */
+
+/*
+ * Wrappers for the rcu_node::lock acquire.
+ *
+ * Because the rcu_nodes form a tree, the tree traversal locking will observe
+ * different lock values, this in turn means that an UNLOCK of one level
+ * followed by a LOCK of another level does not imply a full memory barrier;
+ * and most importantly transitivity is lost.
+ *
+ * In order to restore full ordering between tree levels, augment the regular
+ * lock acquire functions with smp_mb__after_unlock_lock().
+ */
+static inline void raw_spin_lock_rcu_node(struct rcu_node *rnp)
+{
+	raw_spin_lock(&rnp->lock);
+	smp_mb__after_unlock_lock();
+}
+
+static inline void raw_spin_lock_irq_rcu_node(struct rcu_node *rnp)
+{
+	raw_spin_lock_irq(&rnp->lock);
+	smp_mb__after_unlock_lock();
+}
+
+#define raw_spin_lock_irqsave_rcu_node(rnp, flags)	\
+do {							\
+	typecheck(unsigned long, flags);		\
+	raw_spin_lock_irqsave(&(rnp)->lock, flags);	\
+	smp_mb__after_unlock_lock();			\
+} while (0)
+
+static inline bool raw_spin_trylock_rcu_node(struct rcu_node *rnp)
+{
+	bool locked = raw_spin_trylock(&rnp->lock);
+
+	if (locked)
+		smp_mb__after_unlock_lock();
+	return locked;
+}
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 630c19772630..9467a8b7e756 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -63,8 +63,7 @@ static bool __read_mostly rcu_nocb_poll;    /* Offload kthread are to poll. */
 
 /*
  * Check the RCU kernel configuration parameters and print informative
- * messages about anything out of the ordinary.  If you like #ifdef, you
- * will love this function.
+ * messages about anything out of the ordinary.
  */
 static void __init rcu_bootup_announce_oddness(void)
 {
@@ -147,8 +146,8 @@ static void __init rcu_bootup_announce(void)
  * the corresponding expedited grace period will also be the end of the
  * normal grace period.
  */
-static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp,
-				   unsigned long flags) __releases(rnp->lock)
+static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
+	__releases(rnp->lock) /* But leaves rrupts disabled. */
 {
 	int blkd_state = (rnp->gp_tasks ? RCU_GP_TASKS : 0) +
 			 (rnp->exp_tasks ? RCU_EXP_TASKS : 0) +
@@ -236,7 +235,7 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp,
 		rnp->gp_tasks = &t->rcu_node_entry;
 	if (!rnp->exp_tasks && (blkd_state & RCU_EXP_BLKD))
 		rnp->exp_tasks = &t->rcu_node_entry;
-	raw_spin_unlock(&rnp->lock);
+	raw_spin_unlock(&rnp->lock); /* rrupts remain disabled. */
 
 	/*
 	 * Report the quiescent state for the expedited GP.  This expedited
@@ -251,7 +250,6 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp,
 	} else {
 		WARN_ON_ONCE(t->rcu_read_unlock_special.b.exp_need_qs);
 	}
-	local_irq_restore(flags);
 }
 
 /*
@@ -286,12 +284,11 @@ static void rcu_preempt_qs(void)
  * predating the current grace period drain, in other words, until
  * rnp->gp_tasks becomes NULL.
  *
- * Caller must disable preemption.
+ * Caller must disable interrupts.
  */
 static void rcu_preempt_note_context_switch(void)
 {
 	struct task_struct *t = current;
-	unsigned long flags;
 	struct rcu_data *rdp;
 	struct rcu_node *rnp;
 
@@ -301,8 +298,7 @@ static void rcu_preempt_note_context_switch(void)
 		/* Possibly blocking in an RCU read-side critical section. */
 		rdp = this_cpu_ptr(rcu_state_p->rda);
 		rnp = rdp->mynode;
-		raw_spin_lock_irqsave(&rnp->lock, flags);
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_rcu_node(rnp);
 		t->rcu_read_unlock_special.b.blocked = true;
 		t->rcu_blocked_node = rnp;
 
@@ -318,7 +314,7 @@ static void rcu_preempt_note_context_switch(void)
 				       (rnp->qsmask & rdp->grpmask)
 				       ? rnp->gpnum
 				       : rnp->gpnum + 1);
-		rcu_preempt_ctxt_queue(rnp, rdp, flags);
+		rcu_preempt_ctxt_queue(rnp, rdp);
 	} else if (t->rcu_read_lock_nesting < 0 &&
 		   t->rcu_read_unlock_special.s) {
 
@@ -450,20 +446,13 @@ void rcu_read_unlock_special(struct task_struct *t)
 
 		/*
 		 * Remove this task from the list it blocked on.  The task
-		 * now remains queued on the rcu_node corresponding to
-		 * the CPU it first blocked on, so the first attempt to
-		 * acquire the task's rcu_node's ->lock will succeed.
-		 * Keep the loop and add a WARN_ON() out of sheer paranoia.
+		 * now remains queued on the rcu_node corresponding to the
+		 * CPU it first blocked on, so there is no longer any need
+		 * to loop.  Retain a WARN_ON_ONCE() out of sheer paranoia.
 		 */
-		for (;;) {
-			rnp = t->rcu_blocked_node;
-			raw_spin_lock(&rnp->lock);  /* irqs already disabled. */
-			smp_mb__after_unlock_lock();
-			if (rnp == t->rcu_blocked_node)
-				break;
-			WARN_ON_ONCE(1);
-			raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
-		}
+		rnp = t->rcu_blocked_node;
+		raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
+		WARN_ON_ONCE(rnp != t->rcu_blocked_node);
 		empty_norm = !rcu_preempt_blocked_readers_cgp(rnp);
 		empty_exp = sync_rcu_preempt_exp_done(rnp);
 		smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
@@ -527,7 +516,7 @@ static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
 	unsigned long flags;
 	struct task_struct *t;
 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	if (!rcu_preempt_blocked_readers_cgp(rnp)) {
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
 		return;
@@ -748,6 +737,12 @@ void synchronize_rcu_expedited(void)
 	struct rcu_state *rsp = rcu_state_p;
 	unsigned long s;
 
+	/* If expedited grace periods are prohibited, fall back to normal. */
+	if (rcu_gp_is_normal()) {
+		wait_rcu_gp(call_rcu);
+		return;
+	}
+
 	s = rcu_exp_gp_seq_snap(rsp);
 
 	rnp_unlock = exp_funnel_lock(rsp, s);
@@ -788,7 +783,7 @@ EXPORT_SYMBOL_GPL(rcu_barrier);
  */
 static void __init __rcu_init_preempt(void)
 {
-	rcu_init_one(rcu_state_p, rcu_data_p);
+	rcu_init_one(rcu_state_p);
 }
 
 /*
@@ -989,8 +984,7 @@ static int rcu_boost(struct rcu_node *rnp)
 	    READ_ONCE(rnp->boost_tasks) == NULL)
 		return 0;  /* Nothing left to boost. */
 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 
 	/*
 	 * Recheck under the lock: all tasks in need of boosting
@@ -1176,8 +1170,7 @@ static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 			   "rcub/%d", rnp_index);
 	if (IS_ERR(t))
 		return PTR_ERR(t);
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	rnp->boost_kthread_task = t;
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
 	sp.sched_priority = kthread_prio;
@@ -1524,7 +1517,8 @@ static void rcu_prepare_for_idle(void)
 	struct rcu_state *rsp;
 	int tne;
 
-	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL))
+	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) ||
+	    rcu_is_nocb_cpu(smp_processor_id()))
 		return;
 
 	/* Handle nohz enablement switches conservatively. */
@@ -1538,10 +1532,6 @@ static void rcu_prepare_for_idle(void)
 	if (!tne)
 		return;
 
-	/* If this is a no-CBs CPU, no callbacks, just return. */
-	if (rcu_is_nocb_cpu(smp_processor_id()))
-		return;
-
 	/*
 	 * If a non-lazy callback arrived at a CPU having only lazy
 	 * callbacks, invoke RCU core for the side-effect of recalculating
@@ -1567,8 +1557,7 @@ static void rcu_prepare_for_idle(void)
 		if (!*rdp->nxttail[RCU_DONE_TAIL])
 			continue;
 		rnp = rdp->mynode;
-		raw_spin_lock(&rnp->lock); /* irqs already disabled. */
-		smp_mb__after_unlock_lock();
+		raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
 		needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
 		raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
 		if (needwake)
@@ -2068,8 +2057,7 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
 	bool needwake;
 	struct rcu_node *rnp = rdp->mynode;
 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	smp_mb__after_unlock_lock();
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	needwake = rcu_start_future_gp(rnp, rdp, &c);
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
 	if (needwake)
diff --git a/kernel/rcu/tree_trace.c b/kernel/rcu/tree_trace.c
index ef7093cc9b5c..1088e64f01ad 100644
--- a/kernel/rcu/tree_trace.c
+++ b/kernel/rcu/tree_trace.c
@@ -1,5 +1,5 @@
 /*
- * Read-Copy Update tracing for classic implementation
+ * Read-Copy Update tracing for hierarchical implementation.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -16,6 +16,7 @@
  * http://www.gnu.org/licenses/gpl-2.0.html.
  *
  * Copyright IBM Corporation, 2008
+ * Author: Paul E. McKenney
  *
  * Papers:  http://www.rdrop.com/users/paulmck/RCU
  *
@@ -33,9 +34,7 @@
 #include <linux/sched.h>
 #include <linux/atomic.h>
 #include <linux/bitops.h>
-#include <linux/module.h>
 #include <linux/completion.h>
-#include <linux/moduleparam.h>
 #include <linux/percpu.h>
 #include <linux/notifier.h>
 #include <linux/cpu.h>
@@ -183,14 +182,20 @@ static const struct file_operations rcudata_fops = {
 
 static int show_rcuexp(struct seq_file *m, void *v)
 {
+	int cpu;
 	struct rcu_state *rsp = (struct rcu_state *)m->private;
-
+	struct rcu_data *rdp;
+	unsigned long s0 = 0, s1 = 0, s2 = 0, s3 = 0;
+
+	for_each_possible_cpu(cpu) {
+		rdp = per_cpu_ptr(rsp->rda, cpu);
+		s0 += atomic_long_read(&rdp->expedited_workdone0);
+		s1 += atomic_long_read(&rdp->expedited_workdone1);
+		s2 += atomic_long_read(&rdp->expedited_workdone2);
+		s3 += atomic_long_read(&rdp->expedited_workdone3);
+	}
 	seq_printf(m, "s=%lu wd0=%lu wd1=%lu wd2=%lu wd3=%lu n=%lu enq=%d sc=%lu\n",
-		   rsp->expedited_sequence,
-		   atomic_long_read(&rsp->expedited_workdone0),
-		   atomic_long_read(&rsp->expedited_workdone1),
-		   atomic_long_read(&rsp->expedited_workdone2),
-		   atomic_long_read(&rsp->expedited_workdone3),
+		   rsp->expedited_sequence, s0, s1, s2, s3,
 		   atomic_long_read(&rsp->expedited_normal),
 		   atomic_read(&rsp->expedited_need_qs),
 		   rsp->expedited_sequence / 2);
@@ -319,7 +324,7 @@ static void show_one_rcugp(struct seq_file *m, struct rcu_state *rsp)
 	unsigned long gpmax;
 	struct rcu_node *rnp = &rsp->node[0];
 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
+	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	completed = READ_ONCE(rsp->completed);
 	gpnum = READ_ONCE(rsp->gpnum);
 	if (completed == gpnum)
@@ -487,16 +492,4 @@ free_out:
 	debugfs_remove_recursive(rcudir);
 	return 1;
 }
-
-static void __exit rcutree_trace_cleanup(void)
-{
-	debugfs_remove_recursive(rcudir);
-}
-
-
-module_init(rcutree_trace_init);
-module_exit(rcutree_trace_cleanup);
-
-MODULE_AUTHOR("Paul E. McKenney");
-MODULE_DESCRIPTION("Read-Copy Update tracing for hierarchical implementation");
-MODULE_LICENSE("GPL");
+device_initcall(rcutree_trace_init);
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 5f748c5a40f0..76b94e19430b 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -60,7 +60,12 @@ MODULE_ALIAS("rcupdate");
 #endif
 #define MODULE_PARAM_PREFIX "rcupdate."
 
+#ifndef CONFIG_TINY_RCU
 module_param(rcu_expedited, int, 0);
+module_param(rcu_normal, int, 0);
+static int rcu_normal_after_boot;
+module_param(rcu_normal_after_boot, int, 0);
+#endif /* #ifndef CONFIG_TINY_RCU */
 
 #if defined(CONFIG_DEBUG_LOCK_ALLOC) && defined(CONFIG_PREEMPT_COUNT)
 /**
@@ -113,6 +118,17 @@ EXPORT_SYMBOL(rcu_read_lock_sched_held);
 
 #ifndef CONFIG_TINY_RCU
 
+/*
+ * Should expedited grace-period primitives always fall back to their
+ * non-expedited counterparts?  Intended for use within RCU.  Note
+ * that if the user specifies both rcu_expedited and rcu_normal, then
+ * rcu_normal wins.
+ */
+bool rcu_gp_is_normal(void)
+{
+	return READ_ONCE(rcu_normal);
+}
+
 static atomic_t rcu_expedited_nesting =
 	ATOMIC_INIT(IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT) ? 1 : 0);
 
@@ -157,8 +173,6 @@ void rcu_unexpedite_gp(void)
 }
 EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
 
-#endif /* #ifndef CONFIG_TINY_RCU */
-
 /*
  * Inform RCU of the end of the in-kernel boot sequence.
  */
@@ -166,8 +180,12 @@ void rcu_end_inkernel_boot(void)
 {
 	if (IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT))
 		rcu_unexpedite_gp();
+	if (rcu_normal_after_boot)
+		WRITE_ONCE(rcu_normal, 1);
 }
 
+#endif /* #ifndef CONFIG_TINY_RCU */
+
 #ifdef CONFIG_PREEMPT_RCU
 
 /*
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 732e993b564b..1ef0d7aeab47 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3109,7 +3109,6 @@ static void __sched notrace __schedule(bool preempt)
 
 	cpu = smp_processor_id();
 	rq = cpu_rq(cpu);
-	rcu_note_context_switch();
 	prev = rq->curr;
 
 	/*
@@ -3128,13 +3127,16 @@ static void __sched notrace __schedule(bool preempt)
 	if (sched_feat(HRTICK))
 		hrtick_clear(rq);
 
+	local_irq_disable();
+	rcu_note_context_switch();
+
 	/*
 	 * Make sure that signal_pending_state()->signal_pending() below
 	 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
 	 * done by the caller to avoid the race with signal_wake_up().
 	 */
 	smp_mb__before_spinlock();
-	raw_spin_lock_irq(&rq->lock);
+	raw_spin_lock(&rq->lock);
 	lockdep_pin_lock(&rq->lock);
 
 	rq->clock_skip_update <<= 1; /* promote REQ to ACT */