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

Pull v5.10 RCU changes from Paul E. McKenney: - Debugging for smp_call_function(). - Strict grace periods for KASAN. The point of this series is to find RCU-usage bugs, so the corresponding new RCU_STRICT_GRACE_PERIOD Kconfig option depends on both DEBUG_KERNEL and RCU_EXPERT, and is further disabled by dfefault. Finally, the help text includes a goodly list of scary caveats. - New smp_call_function() torture test. - Torture-test updates. - Documentation updates. - Miscellaneous fixes. Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-10-09 08:21:56 +02:00
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -135,10 +135,12 @@ config RCU_FANOUT

 config RCU_FANOUT_LEAF
 	int "Tree-based hierarchical RCU leaf-level fanout value"
-	range 2 64 if 64BIT
-	range 2 32 if !64BIT
+	range 2 64 if 64BIT && !RCU_STRICT_GRACE_PERIOD
+	range 2 32 if !64BIT && !RCU_STRICT_GRACE_PERIOD
+	range 2 3 if RCU_STRICT_GRACE_PERIOD
 	depends on TREE_RCU && RCU_EXPERT
-	default 16
+	default 16 if !RCU_STRICT_GRACE_PERIOD
+	default 2 if RCU_STRICT_GRACE_PERIOD
 	help
 	  This option controls the leaf-level fanout of hierarchical
 	  implementations of RCU, and allows trading off cache misses
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -23,7 +23,7 @@ config TORTURE_TEST
 	tristate
 	default n

-config RCU_PERF_TEST
+config RCU_SCALE_TEST
 	tristate "performance tests for RCU"
 	depends on DEBUG_KERNEL
 	select TORTURE_TEST
@@ -114,4 +114,19 @@ config RCU_EQS_DEBUG
 	  Say N here if you need ultimate kernel/user switch latencies
 	  Say Y if you are unsure

+config RCU_STRICT_GRACE_PERIOD
+	bool "Provide debug RCU implementation with short grace periods"
+	depends on DEBUG_KERNEL && RCU_EXPERT
+	default n
+	select PREEMPT_COUNT if PREEMPT=n
+	help
+	  Select this option to build an RCU variant that is strict about
+	  grace periods, making them as short as it can.  This limits
+	  scalability, destroys real-time response, degrades battery
+	  lifetime and kills performance.  Don't try this on large
+	  machines, as in systems with more than about 10 or 20 CPUs.
+	  But in conjunction with tools like KASAN, it can be helpful
+	  when looking for certain types of RCU usage bugs, for example,
+	  too-short RCU read-side critical sections.
+
 endmenu # "RCU Debugging"
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -11,7 +11,7 @@ obj-y += update.o sync.o
 obj-$(CONFIG_TREE_SRCU) += srcutree.o
 obj-$(CONFIG_TINY_SRCU) += srcutiny.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
-obj-$(CONFIG_RCU_PERF_TEST) += rcuperf.o
+obj-$(CONFIG_RCU_SCALE_TEST) += rcuscale.o
 obj-$(CONFIG_RCU_REF_SCALE_TEST) += refscale.o
 obj-$(CONFIG_TREE_RCU) += tree.o
 obj-$(CONFIG_TINY_RCU) += tiny.o
--- a/kernel/rcu/rcu_segcblist.c
+++ b/kernel/rcu/rcu_segcblist.c
@@ -475,8 +475,16 @@ bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq)
 	 * Also advance to the oldest segment of callbacks whose
 	 * ->gp_seq[] completion is at or after that passed in via "seq",
 	 * skipping any empty segments.
+	 *
+	 * Note that segment "i" (and any lower-numbered segments
+	 * containing older callbacks) will be unaffected, and their
+	 * grace-period numbers remain unchanged.  For example, if i ==
+	 * WAIT_TAIL, then neither WAIT_TAIL nor DONE_TAIL will be touched.
+	 * Instead, the CBs in NEXT_TAIL will be merged with those in
+	 * NEXT_READY_TAIL and the grace-period number of NEXT_READY_TAIL
+	 * would be updated.  NEXT_TAIL would then be empty.
 	 */
-	if (++i >= RCU_NEXT_TAIL)
+	if (rcu_segcblist_restempty(rsclp, i) || ++i >= RCU_NEXT_TAIL)
 		return false;

 	/*
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0+
 /*
- * Read-Copy Update module-based performance-test facility
+ * Read-Copy Update module-based scalability-test facility
 *
 * Copyright (C) IBM Corporation, 2015
 *
@@ -44,13 +44,13 @@
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");

-#define PERF_FLAG "-perf:"
-#define PERFOUT_STRING(s) \
-	pr_alert("%s" PERF_FLAG " %s\n", perf_type, s)
-#define VERBOSE_PERFOUT_STRING(s) \
-	do { if (verbose) pr_alert("%s" PERF_FLAG " %s\n", perf_type, s); } while (0)
-#define VERBOSE_PERFOUT_ERRSTRING(s) \
-	do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)
+#define SCALE_FLAG "-scale:"
+#define SCALEOUT_STRING(s) \
+	pr_alert("%s" SCALE_FLAG " %s\n", scale_type, s)
+#define VERBOSE_SCALEOUT_STRING(s) \
+	do { if (verbose) pr_alert("%s" SCALE_FLAG " %s\n", scale_type, s); } while (0)
+#define VERBOSE_SCALEOUT_ERRSTRING(s) \
+	do { if (verbose) pr_alert("%s" SCALE_FLAG "!!! %s\n", scale_type, s); } while (0)

 /*
 * The intended use cases for the nreaders and nwriters module parameters
@@ -61,25 +61,25 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");
 *	nr_cpus for a mixed reader/writer test.
 *
 * 2.	Specify the nr_cpus kernel boot parameter, but set
- *	rcuperf.nreaders to zero.  This will set nwriters to the
+ *	rcuscale.nreaders to zero.  This will set nwriters to the
 *	value specified by nr_cpus for an update-only test.
 *
 * 3.	Specify the nr_cpus kernel boot parameter, but set
- *	rcuperf.nwriters to zero.  This will set nreaders to the
+ *	rcuscale.nwriters to zero.  This will set nreaders to the
 *	value specified by nr_cpus for a read-only test.
 *
 * Various other use cases may of course be specified.
 *
 * Note that this test's readers are intended only as a test load for
- * the writers.  The reader performance statistics will be overly
+ * the writers.  The reader scalability statistics will be overly
 * pessimistic due to the per-critical-section interrupt disabling,
 * test-end checks, and the pair of calls through pointers.
 */

 #ifdef MODULE
-# define RCUPERF_SHUTDOWN 0
+# define RCUSCALE_SHUTDOWN 0
 #else
-# define RCUPERF_SHUTDOWN 1
+# define RCUSCALE_SHUTDOWN 1
 #endif

 torture_param(bool, gp_async, false, "Use asynchronous GP wait primitives");
@@ -88,16 +88,16 @@ torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
 torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
 torture_param(int, nreaders, -1, "Number of RCU reader threads");
 torture_param(int, nwriters, -1, "Number of RCU updater threads");
-torture_param(bool, shutdown, RCUPERF_SHUTDOWN,
-	      "Shutdown at end of performance tests.");
+torture_param(bool, shutdown, RCUSCALE_SHUTDOWN,
+	      "Shutdown at end of scalability tests.");
 torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
 torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
-torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() perf test?");
+torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() scale test?");
 torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");

-static char *perf_type = "rcu";
-module_param(perf_type, charp, 0444);
-MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, srcu, ...)");
+static char *scale_type = "rcu";
+module_param(scale_type, charp, 0444);
+MODULE_PARM_DESC(scale_type, "Type of RCU to scalability-test (rcu, srcu, ...)");

 static int nrealreaders;
 static int nrealwriters;
@@ -107,12 +107,12 @@ static struct task_struct *shutdown_task;

 static u64 **writer_durations;
 static int *writer_n_durations;
-static atomic_t n_rcu_perf_reader_started;
-static atomic_t n_rcu_perf_writer_started;
-static atomic_t n_rcu_perf_writer_finished;
+static atomic_t n_rcu_scale_reader_started;
+static atomic_t n_rcu_scale_writer_started;
+static atomic_t n_rcu_scale_writer_finished;
 static wait_queue_head_t shutdown_wq;
-static u64 t_rcu_perf_writer_started;
-static u64 t_rcu_perf_writer_finished;
+static u64 t_rcu_scale_writer_started;
+static u64 t_rcu_scale_writer_finished;
 static unsigned long b_rcu_gp_test_started;
 static unsigned long b_rcu_gp_test_finished;
 static DEFINE_PER_CPU(atomic_t, n_async_inflight);
@@ -124,7 +124,7 @@ static DEFINE_PER_CPU(atomic_t, n_async_inflight);
 * Operations vector for selecting different types of tests.
 */

-struct rcu_perf_ops {
+struct rcu_scale_ops {
 	int ptype;
 	void (*init)(void);
 	void (*cleanup)(void);
@@ -140,19 +140,19 @@ struct rcu_perf_ops {
 	const char *name;
 };

-static struct rcu_perf_ops *cur_ops;
+static struct rcu_scale_ops *cur_ops;

 /*
- * Definitions for rcu perf testing.
+ * Definitions for rcu scalability testing.
 */

-static int rcu_perf_read_lock(void) __acquires(RCU)
+static int rcu_scale_read_lock(void) __acquires(RCU)
 {
 	rcu_read_lock();
 	return 0;
 }

-static void rcu_perf_read_unlock(int idx) __releases(RCU)
+static void rcu_scale_read_unlock(int idx) __releases(RCU)
 {
 	rcu_read_unlock();
 }
@@ -162,15 +162,15 @@ static unsigned long __maybe_unused rcu_no_completed(void)
 	return 0;
 }

-static void rcu_sync_perf_init(void)
+static void rcu_sync_scale_init(void)
 {
 }

-static struct rcu_perf_ops rcu_ops = {
+static struct rcu_scale_ops rcu_ops = {
 	.ptype		= RCU_FLAVOR,
-	.init		= rcu_sync_perf_init,
-	.readlock	= rcu_perf_read_lock,
-	.readunlock	= rcu_perf_read_unlock,
+	.init		= rcu_sync_scale_init,
+	.readlock	= rcu_scale_read_lock,
+	.readunlock	= rcu_scale_read_unlock,
 	.get_gp_seq	= rcu_get_gp_seq,
 	.gp_diff	= rcu_seq_diff,
 	.exp_completed	= rcu_exp_batches_completed,
@@ -182,23 +182,23 @@ static struct rcu_perf_ops rcu_ops = {
 };

 /*
- * Definitions for srcu perf testing.
+ * Definitions for srcu scalability testing.
 */

-DEFINE_STATIC_SRCU(srcu_ctl_perf);
-static struct srcu_struct *srcu_ctlp = &srcu_ctl_perf;
+DEFINE_STATIC_SRCU(srcu_ctl_scale);
+static struct srcu_struct *srcu_ctlp = &srcu_ctl_scale;

-static int srcu_perf_read_lock(void) __acquires(srcu_ctlp)
+static int srcu_scale_read_lock(void) __acquires(srcu_ctlp)
 {
 	return srcu_read_lock(srcu_ctlp);
 }

-static void srcu_perf_read_unlock(int idx) __releases(srcu_ctlp)
+static void srcu_scale_read_unlock(int idx) __releases(srcu_ctlp)
 {
 	srcu_read_unlock(srcu_ctlp, idx);
 }

-static unsigned long srcu_perf_completed(void)
+static unsigned long srcu_scale_completed(void)
 {
 	return srcu_batches_completed(srcu_ctlp);
 }
@@ -213,78 +213,78 @@ static void srcu_rcu_barrier(void)
 	srcu_barrier(srcu_ctlp);
 }

-static void srcu_perf_synchronize(void)
+static void srcu_scale_synchronize(void)
 {
 	synchronize_srcu(srcu_ctlp);
 }

-static void srcu_perf_synchronize_expedited(void)
+static void srcu_scale_synchronize_expedited(void)
 {
 	synchronize_srcu_expedited(srcu_ctlp);
 }

-static struct rcu_perf_ops srcu_ops = {
+static struct rcu_scale_ops srcu_ops = {
 	.ptype		= SRCU_FLAVOR,
-	.init		= rcu_sync_perf_init,
-	.readlock	= srcu_perf_read_lock,
-	.readunlock	= srcu_perf_read_unlock,
-	.get_gp_seq	= srcu_perf_completed,
+	.init		= rcu_sync_scale_init,
+	.readlock	= srcu_scale_read_lock,
+	.readunlock	= srcu_scale_read_unlock,
+	.get_gp_seq	= srcu_scale_completed,
 	.gp_diff	= rcu_seq_diff,
-	.exp_completed	= srcu_perf_completed,
+	.exp_completed	= srcu_scale_completed,
 	.async		= srcu_call_rcu,
 	.gp_barrier	= srcu_rcu_barrier,
-	.sync		= srcu_perf_synchronize,
-	.exp_sync	= srcu_perf_synchronize_expedited,
+	.sync		= srcu_scale_synchronize,
+	.exp_sync	= srcu_scale_synchronize_expedited,
 	.name		= "srcu"
 };

 static struct srcu_struct srcud;

-static void srcu_sync_perf_init(void)
+static void srcu_sync_scale_init(void)
 {
 	srcu_ctlp = &srcud;
 	init_srcu_struct(srcu_ctlp);
 }

-static void srcu_sync_perf_cleanup(void)
+static void srcu_sync_scale_cleanup(void)
 {
 	cleanup_srcu_struct(srcu_ctlp);
 }

-static struct rcu_perf_ops srcud_ops = {
+static struct rcu_scale_ops srcud_ops = {
 	.ptype		= SRCU_FLAVOR,
-	.init		= srcu_sync_perf_init,
-	.cleanup	= srcu_sync_perf_cleanup,
-	.readlock	= srcu_perf_read_lock,
-	.readunlock	= srcu_perf_read_unlock,
-	.get_gp_seq	= srcu_perf_completed,
+	.init		= srcu_sync_scale_init,
+	.cleanup	= srcu_sync_scale_cleanup,
+	.readlock	= srcu_scale_read_lock,
+	.readunlock	= srcu_scale_read_unlock,
+	.get_gp_seq	= srcu_scale_completed,
 	.gp_diff	= rcu_seq_diff,
-	.exp_completed	= srcu_perf_completed,
+	.exp_completed	= srcu_scale_completed,
 	.async		= srcu_call_rcu,
 	.gp_barrier	= srcu_rcu_barrier,
-	.sync		= srcu_perf_synchronize,
-	.exp_sync	= srcu_perf_synchronize_expedited,
+	.sync		= srcu_scale_synchronize,
+	.exp_sync	= srcu_scale_synchronize_expedited,
 	.name		= "srcud"
 };

 /*
- * Definitions for RCU-tasks perf testing.
+ * Definitions for RCU-tasks scalability testing.
 */

-static int tasks_perf_read_lock(void)
+static int tasks_scale_read_lock(void)
 {
 	return 0;
 }

-static void tasks_perf_read_unlock(int idx)
+static void tasks_scale_read_unlock(int idx)
 {
 }

-static struct rcu_perf_ops tasks_ops = {
+static struct rcu_scale_ops tasks_ops = {
 	.ptype		= RCU_TASKS_FLAVOR,
-	.init		= rcu_sync_perf_init,
-	.readlock	= tasks_perf_read_lock,
-	.readunlock	= tasks_perf_read_unlock,
+	.init		= rcu_sync_scale_init,
+	.readlock	= tasks_scale_read_lock,
+	.readunlock	= tasks_scale_read_unlock,
 	.get_gp_seq	= rcu_no_completed,
 	.gp_diff	= rcu_seq_diff,
 	.async		= call_rcu_tasks,
@@ -294,7 +294,7 @@ static struct rcu_perf_ops tasks_ops = {
 	.name		= "tasks"
 };

-static unsigned long rcuperf_seq_diff(unsigned long new, unsigned long old)
+static unsigned long rcuscale_seq_diff(unsigned long new, unsigned long old)
 {
 	if (!cur_ops->gp_diff)
 		return new - old;
@@ -302,60 +302,60 @@ static unsigned long rcuperf_seq_diff(unsigned long new, unsigned long old)
 }

 /*
- * If performance tests complete, wait for shutdown to commence.
+ * If scalability tests complete, wait for shutdown to commence.
 */
-static void rcu_perf_wait_shutdown(void)
+static void rcu_scale_wait_shutdown(void)
 {
 	cond_resched_tasks_rcu_qs();
-	if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters)
+	if (atomic_read(&n_rcu_scale_writer_finished) < nrealwriters)
 		return;
 	while (!torture_must_stop())
 		schedule_timeout_uninterruptible(1);
 }

 /*
- * RCU perf reader kthread.  Repeatedly does empty RCU read-side critical
- * section, minimizing update-side interference.  However, the point of
- * this test is not to evaluate reader performance, but instead to serve
- * as a test load for update-side performance testing.
+ * RCU scalability reader kthread.  Repeatedly does empty RCU read-side
+ * critical section, minimizing update-side interference.  However, the
+ * point of this test is not to evaluate reader scalability, but instead
+ * to serve as a test load for update-side scalability testing.
 */
 static int
-rcu_perf_reader(void *arg)
+rcu_scale_reader(void *arg)
 {
 	unsigned long flags;
 	int idx;
 	long me = (long)arg;

-	VERBOSE_PERFOUT_STRING("rcu_perf_reader task started");
+	VERBOSE_SCALEOUT_STRING("rcu_scale_reader task started");
 	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 	set_user_nice(current, MAX_NICE);
-	atomic_inc(&n_rcu_perf_reader_started);
+	atomic_inc(&n_rcu_scale_reader_started);

 	do {
 		local_irq_save(flags);
 		idx = cur_ops->readlock();
 		cur_ops->readunlock(idx);
 		local_irq_restore(flags);
-		rcu_perf_wait_shutdown();
+		rcu_scale_wait_shutdown();
 	} while (!torture_must_stop());
-	torture_kthread_stopping("rcu_perf_reader");
+	torture_kthread_stopping("rcu_scale_reader");
 	return 0;
 }

 /*
- * Callback function for asynchronous grace periods from rcu_perf_writer().
+ * Callback function for asynchronous grace periods from rcu_scale_writer().
 */
-static void rcu_perf_async_cb(struct rcu_head *rhp)
+static void rcu_scale_async_cb(struct rcu_head *rhp)
 {
 	atomic_dec(this_cpu_ptr(&n_async_inflight));
 	kfree(rhp);
 }

 /*
- * RCU perf writer kthread.  Repeatedly does a grace period.
+ * RCU scale writer kthread.  Repeatedly does a grace period.
 */
 static int
-rcu_perf_writer(void *arg)
+rcu_scale_writer(void *arg)
 {
 	int i = 0;
 	int i_max;
@@ -366,7 +366,7 @@ rcu_perf_writer(void *arg)
 	u64 *wdp;
 	u64 *wdpp = writer_durations[me];

-	VERBOSE_PERFOUT_STRING("rcu_perf_writer task started");
+	VERBOSE_SCALEOUT_STRING("rcu_scale_writer task started");
 	WARN_ON(!wdpp);
 	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 	sched_set_fifo_low(current);
@@ -383,8 +383,8 @@ rcu_perf_writer(void *arg)
 		schedule_timeout_uninterruptible(1);

 	t = ktime_get_mono_fast_ns();
-	if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) {
-		t_rcu_perf_writer_started = t;
+	if (atomic_inc_return(&n_rcu_scale_writer_started) >= nrealwriters) {
+		t_rcu_scale_writer_started = t;
 		if (gp_exp) {
 			b_rcu_gp_test_started =
 				cur_ops->exp_completed() / 2;
@@ -404,7 +404,7 @@ retry:
 				rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
 			if (rhp && atomic_read(this_cpu_ptr(&n_async_inflight)) < gp_async_max) {
 				atomic_inc(this_cpu_ptr(&n_async_inflight));
-				cur_ops->async(rhp, rcu_perf_async_cb);
+				cur_ops->async(rhp, rcu_scale_async_cb);
 				rhp = NULL;
 			} else if (!kthread_should_stop()) {
 				cur_ops->gp_barrier();
@@ -421,19 +421,19 @@ retry:
 		*wdp = t - *wdp;
 		i_max = i;
 		if (!started &&
-		    atomic_read(&n_rcu_perf_writer_started) >= nrealwriters)
+		    atomic_read(&n_rcu_scale_writer_started) >= nrealwriters)
 			started = true;
 		if (!done && i >= MIN_MEAS) {
 			done = true;
 			sched_set_normal(current, 0);
-			pr_alert("%s%s rcu_perf_writer %ld has %d measurements\n",
-				 perf_type, PERF_FLAG, me, MIN_MEAS);
-			if (atomic_inc_return(&n_rcu_perf_writer_finished) >=
+			pr_alert("%s%s rcu_scale_writer %ld has %d measurements\n",
+				 scale_type, SCALE_FLAG, me, MIN_MEAS);
+			if (atomic_inc_return(&n_rcu_scale_writer_finished) >=
 			    nrealwriters) {
 				schedule_timeout_interruptible(10);
 				rcu_ftrace_dump(DUMP_ALL);
-				PERFOUT_STRING("Test complete");
-				t_rcu_perf_writer_finished = t;
+				SCALEOUT_STRING("Test complete");
+				t_rcu_scale_writer_finished = t;
 				if (gp_exp) {
 					b_rcu_gp_test_finished =
 						cur_ops->exp_completed() / 2;
@@ -448,30 +448,30 @@ retry:
 			}
 		}
 		if (done && !alldone &&
-		    atomic_read(&n_rcu_perf_writer_finished) >= nrealwriters)
+		    atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters)
 			alldone = true;
 		if (started && !alldone && i < MAX_MEAS - 1)
 			i++;
-		rcu_perf_wait_shutdown();
+		rcu_scale_wait_shutdown();
 	} while (!torture_must_stop());
 	if (gp_async) {
 		cur_ops->gp_barrier();
 	}
 	writer_n_durations[me] = i_max;
-	torture_kthread_stopping("rcu_perf_writer");
+	torture_kthread_stopping("rcu_scale_writer");
 	return 0;
 }

 static void
-rcu_perf_print_module_parms(struct rcu_perf_ops *cur_ops, const char *tag)
+rcu_scale_print_module_parms(struct rcu_scale_ops *cur_ops, const char *tag)
 {
-	pr_alert("%s" PERF_FLAG
+	pr_alert("%s" SCALE_FLAG
 		 "--- %s: nreaders=%d nwriters=%d verbose=%d shutdown=%d\n",
-		 perf_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
+		 scale_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
 }

 static void
-rcu_perf_cleanup(void)
+rcu_scale_cleanup(void)
 {
 	int i;
 	int j;
@@ -484,11 +484,11 @@ rcu_perf_cleanup(void)
 	 * during the mid-boot phase, so have to wait till the end.
 	 */
 	if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp)
-		VERBOSE_PERFOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!");
+		VERBOSE_SCALEOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!");
 	if (rcu_gp_is_normal() && gp_exp)
-		VERBOSE_PERFOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!");
+		VERBOSE_SCALEOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!");
 	if (gp_exp && gp_async)
-		VERBOSE_PERFOUT_ERRSTRING("No expedited async GPs, so went with async!");
+		VERBOSE_SCALEOUT_ERRSTRING("No expedited async GPs, so went with async!");

 	if (torture_cleanup_begin())
 		return;
@@ -499,30 +499,30 @@ rcu_perf_cleanup(void)

 	if (reader_tasks) {
 		for (i = 0; i < nrealreaders; i++)
-			torture_stop_kthread(rcu_perf_reader,
+			torture_stop_kthread(rcu_scale_reader,
 					     reader_tasks[i]);
 		kfree(reader_tasks);
 	}

 	if (writer_tasks) {
 		for (i = 0; i < nrealwriters; i++) {
-			torture_stop_kthread(rcu_perf_writer,
+			torture_stop_kthread(rcu_scale_writer,
 					     writer_tasks[i]);
 			if (!writer_n_durations)
 				continue;
 			j = writer_n_durations[i];
 			pr_alert("%s%s writer %d gps: %d\n",
-				 perf_type, PERF_FLAG, i, j);
+				 scale_type, SCALE_FLAG, i, j);
 			ngps += j;
 		}
 		pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n",
-			 perf_type, PERF_FLAG,
-			 t_rcu_perf_writer_started, t_rcu_perf_writer_finished,
-			 t_rcu_perf_writer_finished -
-			 t_rcu_perf_writer_started,
+			 scale_type, SCALE_FLAG,
+			 t_rcu_scale_writer_started, t_rcu_scale_writer_finished,
+			 t_rcu_scale_writer_finished -
+			 t_rcu_scale_writer_started,
 			 ngps,
-			 rcuperf_seq_diff(b_rcu_gp_test_finished,
-					  b_rcu_gp_test_started));
+			 rcuscale_seq_diff(b_rcu_gp_test_finished,
+					   b_rcu_gp_test_started));
 		for (i = 0; i < nrealwriters; i++) {
 			if (!writer_durations)
 				break;
@@ -534,7 +534,7 @@ rcu_perf_cleanup(void)
 			for (j = 0; j <= writer_n_durations[i]; j++) {
 				wdp = &wdpp[j];
 				pr_alert("%s%s %4d writer-duration: %5d %llu\n",
-					perf_type, PERF_FLAG,
+					scale_type, SCALE_FLAG,
 					i, j, *wdp);
 				if (j % 100 == 0)
 					schedule_timeout_uninterruptible(1);
@@ -573,22 +573,22 @@ static int compute_real(int n)
 }

 /*
- * RCU perf shutdown kthread.  Just waits to be awakened, then shuts
+ * RCU scalability shutdown kthread.  Just waits to be awakened, then shuts
 * down system.
 */
 static int
-rcu_perf_shutdown(void *arg)
+rcu_scale_shutdown(void *arg)
 {
 	wait_event(shutdown_wq,
-		   atomic_read(&n_rcu_perf_writer_finished) >= nrealwriters);
+		   atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters);
 	smp_mb(); /* Wake before output. */
-	rcu_perf_cleanup();
+	rcu_scale_cleanup();
 	kernel_power_off();
 	return -EINVAL;
 }

 /*
- * kfree_rcu() performance tests: Start a kfree_rcu() loop on all CPUs for number
+ * kfree_rcu() scalability tests: Start a kfree_rcu() loop on all CPUs for number
 * of iterations and measure total time and number of GP for all iterations to complete.
 */

@@ -598,8 +598,8 @@ torture_param(int, kfree_loops, 10, "Number of loops doing kfree_alloc_num alloc

 static struct task_struct **kfree_reader_tasks;
 static int kfree_nrealthreads;
-static atomic_t n_kfree_perf_thread_started;
-static atomic_t n_kfree_perf_thread_ended;
+static atomic_t n_kfree_scale_thread_started;
+static atomic_t n_kfree_scale_thread_ended;

 struct kfree_obj {
 	char kfree_obj[8];
@@ -607,7 +607,7 @@ struct kfree_obj {
 };

 static int
-kfree_perf_thread(void *arg)
+kfree_scale_thread(void *arg)
 {
 	int i, loop = 0;
 	long me = (long)arg;
@@ -615,13 +615,13 @@ kfree_perf_thread(void *arg)
 	u64 start_time, end_time;
 	long long mem_begin, mem_during = 0;

-	VERBOSE_PERFOUT_STRING("kfree_perf_thread task started");
+	VERBOSE_SCALEOUT_STRING("kfree_scale_thread task started");
 	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 	set_user_nice(current, MAX_NICE);

 	start_time = ktime_get_mono_fast_ns();

-	if (atomic_inc_return(&n_kfree_perf_thread_started) >= kfree_nrealthreads) {
+	if (atomic_inc_return(&n_kfree_scale_thread_started) >= kfree_nrealthreads) {
 		if (gp_exp)
 			b_rcu_gp_test_started = cur_ops->exp_completed() / 2;
 		else
@@ -646,7 +646,7 @@ kfree_perf_thread(void *arg)
 		cond_resched();
 	} while (!torture_must_stop() && ++loop < kfree_loops);

-	if (atomic_inc_return(&n_kfree_perf_thread_ended) >= kfree_nrealthreads) {
+	if (atomic_inc_return(&n_kfree_scale_thread_ended) >= kfree_nrealthreads) {
 		end_time = ktime_get_mono_fast_ns();

 		if (gp_exp)
@@ -656,7 +656,7 @@ kfree_perf_thread(void *arg)

 		pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld, memory footprint: %lldMB\n",
 		       (unsigned long long)(end_time - start_time), kfree_loops,
-		       rcuperf_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started),
+		       rcuscale_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started),
 		       (mem_begin - mem_during) >> (20 - PAGE_SHIFT));

 		if (shutdown) {
@@ -665,12 +665,12 @@ kfree_perf_thread(void *arg)
 		}
 	}

-	torture_kthread_stopping("kfree_perf_thread");
+	torture_kthread_stopping("kfree_scale_thread");
 	return 0;
 }

 static void
-kfree_perf_cleanup(void)
+kfree_scale_cleanup(void)
 {
 	int i;

@@ -679,7 +679,7 @@ kfree_perf_cleanup(void)

 	if (kfree_reader_tasks) {
 		for (i = 0; i < kfree_nrealthreads; i++)
-			torture_stop_kthread(kfree_perf_thread,
+			torture_stop_kthread(kfree_scale_thread,
 					     kfree_reader_tasks[i]);
 		kfree(kfree_reader_tasks);
 	}
@@ -691,20 +691,20 @@ kfree_perf_cleanup(void)
 * shutdown kthread.  Just waits to be awakened, then shuts down system.
 */
 static int
-kfree_perf_shutdown(void *arg)
+kfree_scale_shutdown(void *arg)
 {
 	wait_event(shutdown_wq,
-		   atomic_read(&n_kfree_perf_thread_ended) >= kfree_nrealthreads);
+		   atomic_read(&n_kfree_scale_thread_ended) >= kfree_nrealthreads);

 	smp_mb(); /* Wake before output. */

-	kfree_perf_cleanup();
+	kfree_scale_cleanup();
 	kernel_power_off();
 	return -EINVAL;
 }

 static int __init
-kfree_perf_init(void)
+kfree_scale_init(void)
 {
 	long i;
 	int firsterr = 0;
@@ -713,7 +713,7 @@ kfree_perf_init(void)
 	/* Start up the kthreads. */
 	if (shutdown) {
 		init_waitqueue_head(&shutdown_wq);
-		firsterr = torture_create_kthread(kfree_perf_shutdown, NULL,
+		firsterr = torture_create_kthread(kfree_scale_shutdown, NULL,
 						  shutdown_task);
 		if (firsterr)
 			goto unwind;
@@ -730,13 +730,13 @@ kfree_perf_init(void)
 	}

 	for (i = 0; i < kfree_nrealthreads; i++) {
-		firsterr = torture_create_kthread(kfree_perf_thread, (void *)i,
+		firsterr = torture_create_kthread(kfree_scale_thread, (void *)i,
 						  kfree_reader_tasks[i]);
 		if (firsterr)
 			goto unwind;
 	}

-	while (atomic_read(&n_kfree_perf_thread_started) < kfree_nrealthreads)
+	while (atomic_read(&n_kfree_scale_thread_started) < kfree_nrealthreads)
 		schedule_timeout_uninterruptible(1);

 	torture_init_end();
@@ -744,35 +744,35 @@ kfree_perf_init(void)

 unwind:
 	torture_init_end();
-	kfree_perf_cleanup();
+	kfree_scale_cleanup();
 	return firsterr;
 }

 static int __init
-rcu_perf_init(void)
+rcu_scale_init(void)
 {
 	long i;
 	int firsterr = 0;
-	static struct rcu_perf_ops *perf_ops[] = {
+	static struct rcu_scale_ops *scale_ops[] = {
 		&rcu_ops, &srcu_ops, &srcud_ops, &tasks_ops,
 	};

-	if (!torture_init_begin(perf_type, verbose))
+	if (!torture_init_begin(scale_type, verbose))
 		return -EBUSY;

-	/* Process args and tell the world that the perf'er is on the job. */
-	for (i = 0; i < ARRAY_SIZE(perf_ops); i++) {
-		cur_ops = perf_ops[i];
-		if (strcmp(perf_type, cur_ops->name) == 0)
+	/* Process args and announce that the scalability'er is on the job. */
+	for (i = 0; i < ARRAY_SIZE(scale_ops); i++) {
+		cur_ops = scale_ops[i];
+		if (strcmp(scale_type, cur_ops->name) == 0)
 			break;
 	}
-	if (i == ARRAY_SIZE(perf_ops)) {
-		pr_alert("rcu-perf: invalid perf type: \"%s\"\n", perf_type);
-		pr_alert("rcu-perf types:");
-		for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
-			pr_cont(" %s", perf_ops[i]->name);
+	if (i == ARRAY_SIZE(scale_ops)) {
+		pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type);
+		pr_alert("rcu-scale types:");
+		for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
+			pr_cont(" %s", scale_ops[i]->name);
 		pr_cont("\n");
-		WARN_ON(!IS_MODULE(CONFIG_RCU_PERF_TEST));
+		WARN_ON(!IS_MODULE(CONFIG_RCU_SCALE_TEST));
 		firsterr = -EINVAL;
 		cur_ops = NULL;
 		goto unwind;
@@ -781,20 +781,20 @@ rcu_perf_init(void)
 		cur_ops->init();

 	if (kfree_rcu_test)
-		return kfree_perf_init();
+		return kfree_scale_init();

 	nrealwriters = compute_real(nwriters);
 	nrealreaders = compute_real(nreaders);
-	atomic_set(&n_rcu_perf_reader_started, 0);
-	atomic_set(&n_rcu_perf_writer_started, 0);
-	atomic_set(&n_rcu_perf_writer_finished, 0);
-	rcu_perf_print_module_parms(cur_ops, "Start of test");
+	atomic_set(&n_rcu_scale_reader_started, 0);
+	atomic_set(&n_rcu_scale_writer_started, 0);
+	atomic_set(&n_rcu_scale_writer_finished, 0);
+	rcu_scale_print_module_parms(cur_ops, "Start of test");

 	/* Start up the kthreads. */

 	if (shutdown) {
 		init_waitqueue_head(&shutdown_wq);
-		firsterr = torture_create_kthread(rcu_perf_shutdown, NULL,
+		firsterr = torture_create_kthread(rcu_scale_shutdown, NULL,
 						  shutdown_task);
 		if (firsterr)
 			goto unwind;
@@ -803,17 +803,17 @@ rcu_perf_init(void)
 	reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
 			       GFP_KERNEL);
 	if (reader_tasks == NULL) {
-		VERBOSE_PERFOUT_ERRSTRING("out of memory");
+		VERBOSE_SCALEOUT_ERRSTRING("out of memory");
 		firsterr = -ENOMEM;
 		goto unwind;
 	}
 	for (i = 0; i < nrealreaders; i++) {
-		firsterr = torture_create_kthread(rcu_perf_reader, (void *)i,
+		firsterr = torture_create_kthread(rcu_scale_reader, (void *)i,
 						  reader_tasks[i]);
 		if (firsterr)
 			goto unwind;
 	}
-	while (atomic_read(&n_rcu_perf_reader_started) < nrealreaders)
+	while (atomic_read(&n_rcu_scale_reader_started) < nrealreaders)
 		schedule_timeout_uninterruptible(1);
 	writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]),
 			       GFP_KERNEL);
@@ -823,7 +823,7 @@ rcu_perf_init(void)
 		kcalloc(nrealwriters, sizeof(*writer_n_durations),
 			GFP_KERNEL);
 	if (!writer_tasks || !writer_durations || !writer_n_durations) {
-		VERBOSE_PERFOUT_ERRSTRING("out of memory");
+		VERBOSE_SCALEOUT_ERRSTRING("out of memory");
 		firsterr = -ENOMEM;
 		goto unwind;
 	}
@@ -835,7 +835,7 @@ rcu_perf_init(void)
 			firsterr = -ENOMEM;
 			goto unwind;
 		}
-		firsterr = torture_create_kthread(rcu_perf_writer, (void *)i,
+		firsterr = torture_create_kthread(rcu_scale_writer, (void *)i,
 						  writer_tasks[i]);
 		if (firsterr)
 			goto unwind;
@@ -845,9 +845,9 @@ rcu_perf_init(void)

 unwind:
 	torture_init_end();
-	rcu_perf_cleanup();
+	rcu_scale_cleanup();
 	return firsterr;
 }

-module_init(rcu_perf_init);
-module_exit(rcu_perf_cleanup);
+module_init(rcu_scale_init);
+module_exit(rcu_scale_cleanup);
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -52,19 +52,6 @@
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");

-#ifndef data_race
-#define data_race(expr)							\
-	({								\
-		expr;							\
-	})
-#endif
-#ifndef ASSERT_EXCLUSIVE_WRITER
-#define ASSERT_EXCLUSIVE_WRITER(var) do { } while (0)
-#endif
-#ifndef ASSERT_EXCLUSIVE_ACCESS
-#define ASSERT_EXCLUSIVE_ACCESS(var) do { } while (0)
-#endif
-
 /* Bits for ->extendables field, extendables param, and related definitions. */
 #define RCUTORTURE_RDR_SHIFT	 8	/* Put SRCU index in upper bits. */
 #define RCUTORTURE_RDR_MASK	 ((1 << RCUTORTURE_RDR_SHIFT) - 1)
@@ -100,6 +87,7 @@ torture_param(bool, gp_normal, false,
 	     "Use normal (non-expedited) GP wait primitives");
 torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives");
 torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers");
+torture_param(int, leakpointer, 0, "Leak pointer dereferences from readers");
 torture_param(int, n_barrier_cbs, 0,
 	     "# of callbacks/kthreads for barrier testing");
 torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
@@ -185,6 +173,7 @@ static long n_barrier_successes; /* did rcu_barrier test succeed? */
 static unsigned long n_read_exits;
 static struct list_head rcu_torture_removed;
 static unsigned long shutdown_jiffies;
+static unsigned long start_gp_seq;

 static int rcu_torture_writer_state;
 #define RTWS_FIXED_DELAY	0
@@ -1413,6 +1402,9 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
 	preempt_enable();
 	rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
 	WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK);
+	// This next splat is expected behavior if leakpointer, especially
+	// for CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels.
+	WARN_ON_ONCE(leakpointer && READ_ONCE(p->rtort_pipe_count) > 1);

 	/* If error or close call, record the sequence of reader protections. */
 	if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) {
@@ -1808,6 +1800,7 @@ struct rcu_fwd {
 	unsigned long rcu_launder_gp_seq_start;
 };

+static DEFINE_MUTEX(rcu_fwd_mutex);
 static struct rcu_fwd *rcu_fwds;
 static bool rcu_fwd_emergency_stop;

@@ -2074,8 +2067,14 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
 static int rcutorture_oom_notify(struct notifier_block *self,
 				 unsigned long notused, void *nfreed)
 {
-	struct rcu_fwd *rfp = rcu_fwds;
+	struct rcu_fwd *rfp;

+	mutex_lock(&rcu_fwd_mutex);
+	rfp = rcu_fwds;
+	if (!rfp) {
+		mutex_unlock(&rcu_fwd_mutex);
+		return NOTIFY_OK;
+	}
 	WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
 	     __func__);
 	rcu_torture_fwd_cb_hist(rfp);
@@ -2093,6 +2092,7 @@ static int rcutorture_oom_notify(struct notifier_block *self,
 	smp_mb(); /* Frees before return to avoid redoing OOM. */
 	(*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */
 	pr_info("%s returning after OOM processing.\n", __func__);
+	mutex_unlock(&rcu_fwd_mutex);
 	return NOTIFY_OK;
 }

@@ -2114,13 +2114,11 @@ static int rcu_torture_fwd_prog(void *args)
 	do {
 		schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
 		WRITE_ONCE(rcu_fwd_emergency_stop, false);
-		register_oom_notifier(&rcutorture_oom_nb);
 		if (!IS_ENABLED(CONFIG_TINY_RCU) ||
 		    rcu_inkernel_boot_has_ended())
 			rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
 		if (rcu_inkernel_boot_has_ended())
 			rcu_torture_fwd_prog_cr(rfp);
-		unregister_oom_notifier(&rcutorture_oom_nb);

 		/* Avoid slow periods, better to test when busy. */
 		stutter_wait("rcu_torture_fwd_prog");
@@ -2160,9 +2158,26 @@ static int __init rcu_torture_fwd_prog_init(void)
 		return -ENOMEM;
 	spin_lock_init(&rfp->rcu_fwd_lock);
 	rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
+	mutex_lock(&rcu_fwd_mutex);
+	rcu_fwds = rfp;
+	mutex_unlock(&rcu_fwd_mutex);
+	register_oom_notifier(&rcutorture_oom_nb);
 	return torture_create_kthread(rcu_torture_fwd_prog, rfp, fwd_prog_task);
 }

+static void rcu_torture_fwd_prog_cleanup(void)
+{
+	struct rcu_fwd *rfp;
+
+	torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
+	rfp = rcu_fwds;
+	mutex_lock(&rcu_fwd_mutex);
+	rcu_fwds = NULL;
+	mutex_unlock(&rcu_fwd_mutex);
+	unregister_oom_notifier(&rcutorture_oom_nb);
+	kfree(rfp);
+}
+
 /* Callback function for RCU barrier testing. */
 static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
 {
@@ -2460,7 +2475,7 @@ rcu_torture_cleanup(void)
 	show_rcu_gp_kthreads();
 	rcu_torture_read_exit_cleanup();
 	rcu_torture_barrier_cleanup();
-	torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
+	rcu_torture_fwd_prog_cleanup();
 	torture_stop_kthread(rcu_torture_stall, stall_task);
 	torture_stop_kthread(rcu_torture_writer, writer_task);

@@ -2482,8 +2497,9 @@ rcu_torture_cleanup(void)

 	rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
 	srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
-	pr_alert("%s:  End-test grace-period state: g%lu f%#x\n",
-		 cur_ops->name, gp_seq, flags);
+	pr_alert("%s:  End-test grace-period state: g%ld f%#x total-gps=%ld\n",
+		 cur_ops->name, (long)gp_seq, flags,
+		 rcutorture_seq_diff(gp_seq, start_gp_seq));
 	torture_stop_kthread(rcu_torture_stats, stats_task);
 	torture_stop_kthread(rcu_torture_fqs, fqs_task);
 	if (rcu_torture_can_boost())
@@ -2607,6 +2623,8 @@ rcu_torture_init(void)
 	long i;
 	int cpu;
 	int firsterr = 0;
+	int flags = 0;
+	unsigned long gp_seq = 0;
 	static struct rcu_torture_ops *torture_ops[] = {
 		&rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
 		&busted_srcud_ops, &tasks_ops, &tasks_rude_ops,
@@ -2649,6 +2667,11 @@ rcu_torture_init(void)
 			nrealreaders = 1;
 	}
 	rcu_torture_print_module_parms(cur_ops, "Start of test");
+	rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
+	srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
+	start_gp_seq = gp_seq;
+	pr_alert("%s:  Start-test grace-period state: g%ld f%#x\n",
+		 cur_ops->name, (long)gp_seq, flags);

 	/* Set up the freelist. */

--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -546,9 +546,11 @@ static int main_func(void *arg)
 	// Print the average of all experiments
 	SCALEOUT("END OF TEST. Calculating average duration per loop (nanoseconds)...\n");

-	buf[0] = 0;
-	strcat(buf, "\n");
-	strcat(buf, "Runs\tTime(ns)\n");
+	if (!errexit) {
+		buf[0] = 0;
+		strcat(buf, "\n");
+		strcat(buf, "Runs\tTime(ns)\n");
+	}

 	for (exp = 0; exp < nruns; exp++) {
 		u64 avg;
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -29,19 +29,6 @@
 #include "rcu.h"
 #include "rcu_segcblist.h"

-#ifndef data_race
-#define data_race(expr)							\
-	({								\
-		expr;							\
-	})
-#endif
-#ifndef ASSERT_EXCLUSIVE_WRITER
-#define ASSERT_EXCLUSIVE_WRITER(var) do { } while (0)
-#endif
-#ifndef ASSERT_EXCLUSIVE_ACCESS
-#define ASSERT_EXCLUSIVE_ACCESS(var) do { } while (0)
-#endif
-
 /* Holdoff in nanoseconds for auto-expediting. */
 #define DEFAULT_SRCU_EXP_HOLDOFF (25 * 1000)
 static ulong exp_holdoff = DEFAULT_SRCU_EXP_HOLDOFF;
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -70,19 +70,6 @@
 #endif
 #define MODULE_PARAM_PREFIX "rcutree."

-#ifndef data_race
-#define data_race(expr)							\
-	({								\
-		expr;							\
-	})
-#endif
-#ifndef ASSERT_EXCLUSIVE_WRITER
-#define ASSERT_EXCLUSIVE_WRITER(var) do { } while (0)
-#endif
-#ifndef ASSERT_EXCLUSIVE_ACCESS
-#define ASSERT_EXCLUSIVE_ACCESS(var) do { } while (0)
-#endif
-
 /* Data structures. */

 /*
@@ -178,6 +165,12 @@ module_param(gp_init_delay, int, 0444);
 static int gp_cleanup_delay;
 module_param(gp_cleanup_delay, int, 0444);

+// Add delay to rcu_read_unlock() for strict grace periods.
+static int rcu_unlock_delay;
+#ifdef CONFIG_RCU_STRICT_GRACE_PERIOD
+module_param(rcu_unlock_delay, int, 0444);
+#endif
+
 /*
 * This rcu parameter is runtime-read-only. It reflects
 * a minimum allowed number of objects which can be cached
@@ -468,24 +461,25 @@ static int rcu_is_cpu_rrupt_from_idle(void)
 	return __this_cpu_read(rcu_data.dynticks_nesting) == 0;
 }

-#define DEFAULT_RCU_BLIMIT 10     /* Maximum callbacks per rcu_do_batch ... */
-#define DEFAULT_MAX_RCU_BLIMIT 10000 /* ... even during callback flood. */
+#define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10)
+				// Maximum callbacks per rcu_do_batch ...
+#define DEFAULT_MAX_RCU_BLIMIT 10000 // ... even during callback flood.
 static long blimit = DEFAULT_RCU_BLIMIT;
-#define DEFAULT_RCU_QHIMARK 10000 /* If this many pending, ignore blimit. */
+#define DEFAULT_RCU_QHIMARK 10000 // If this many pending, ignore blimit.
 static long qhimark = DEFAULT_RCU_QHIMARK;
-#define DEFAULT_RCU_QLOMARK 100   /* Once only this many pending, use blimit. */
+#define DEFAULT_RCU_QLOMARK 100   // Once only this many pending, use blimit.
 static long qlowmark = DEFAULT_RCU_QLOMARK;
 #define DEFAULT_RCU_QOVLD_MULT 2
 #define DEFAULT_RCU_QOVLD (DEFAULT_RCU_QOVLD_MULT * DEFAULT_RCU_QHIMARK)
-static long qovld = DEFAULT_RCU_QOVLD; /* If this many pending, hammer QS. */
-static long qovld_calc = -1;	  /* No pre-initialization lock acquisitions! */
+static long qovld = DEFAULT_RCU_QOVLD; // If this many pending, hammer QS.
+static long qovld_calc = -1;	  // No pre-initialization lock acquisitions!

 module_param(blimit, long, 0444);
 module_param(qhimark, long, 0444);
 module_param(qlowmark, long, 0444);
 module_param(qovld, long, 0444);

-static ulong jiffies_till_first_fqs = ULONG_MAX;
+static ulong jiffies_till_first_fqs = IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 0 : ULONG_MAX;
 static ulong jiffies_till_next_fqs = ULONG_MAX;
 static bool rcu_kick_kthreads;
 static int rcu_divisor = 7;
@@ -1092,11 +1086,6 @@ static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
 	}
 }

-noinstr bool __rcu_is_watching(void)
-{
-	return !rcu_dynticks_curr_cpu_in_eqs();
-}
-
 /**
 * rcu_is_watching - see if RCU thinks that the current CPU is not idle
 *
@@ -1229,13 +1218,28 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 		return 1;
 	}

-	/* If waiting too long on an offline CPU, complain. */
-	if (!(rdp->grpmask & rcu_rnp_online_cpus(rnp)) &&
-	    time_after(jiffies, rcu_state.gp_start + HZ)) {
+	/*
+	 * Complain if a CPU that is considered to be offline from RCU's
+	 * perspective has not yet reported a quiescent state.  After all,
+	 * the offline CPU should have reported a quiescent state during
+	 * the CPU-offline process, or, failing that, by rcu_gp_init()
+	 * if it ran concurrently with either the CPU going offline or the
+	 * last task on a leaf rcu_node structure exiting its RCU read-side
+	 * critical section while all CPUs corresponding to that structure
+	 * are offline.  This added warning detects bugs in any of these
+	 * code paths.
+	 *
+	 * The rcu_node structure's ->lock is held here, which excludes
+	 * the relevant portions the CPU-hotplug code, the grace-period
+	 * initialization code, and the rcu_read_unlock() code paths.
+	 *
+	 * For more detail, please refer to the "Hotplug CPU" section
+	 * of RCU's Requirements documentation.
+	 */
+	if (WARN_ON_ONCE(!(rdp->grpmask & rcu_rnp_online_cpus(rnp)))) {
 		bool onl;
 		struct rcu_node *rnp1;

-		WARN_ON(1);  /* Offline CPUs are supposed to report QS! */
 		pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n",
 			__func__, rnp->grplo, rnp->grphi, rnp->level,
 			(long)rnp->gp_seq, (long)rnp->completedqs);
@@ -1498,9 +1502,10 @@ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp)

 	/* Trace depending on how much we were able to accelerate. */
 	if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL))
-		trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccWaitCB"));
+		trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccWaitCB"));
 	else
-		trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccReadyCB"));
+		trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccReadyCB"));
+
 	return ret;
 }

@@ -1575,6 +1580,19 @@ static void __maybe_unused rcu_advance_cbs_nowake(struct rcu_node *rnp,
 	raw_spin_unlock_rcu_node(rnp);
 }

+/*
+ * In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, attempt to generate a
+ * quiescent state.  This is intended to be invoked when the CPU notices
+ * a new grace period.
+ */
+static void rcu_strict_gp_check_qs(void)
+{
+	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) {
+		rcu_read_lock();
+		rcu_read_unlock();
+	}
+}
+
 /*
 * Update CPU-local rcu_data state to record the beginnings and ends of
 * grace periods.  The caller must hold the ->lock of the leaf rcu_node
@@ -1645,6 +1663,7 @@ static void note_gp_changes(struct rcu_data *rdp)
 	}
 	needwake = __note_gp_changes(rnp, rdp);
 	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+	rcu_strict_gp_check_qs();
 	if (needwake)
 		rcu_gp_kthread_wake();
 }
@@ -1682,6 +1701,15 @@ static void rcu_gp_torture_wait(void)
 	}
 }

+/*
+ * Handler for on_each_cpu() to invoke the target CPU's RCU core
+ * processing.
+ */
+static void rcu_strict_gp_boundary(void *unused)
+{
+	invoke_rcu_core();
+}
+
 /*
 * Initialize a new grace period.  Return false if no grace period required.
 */
@@ -1720,10 +1748,13 @@ static bool rcu_gp_init(void)
 	raw_spin_unlock_irq_rcu_node(rnp);

 	/*
-	 * Apply per-leaf buffered online and offline operations to the
-	 * rcu_node tree.  Note that this new grace period need not wait
-	 * for subsequent online CPUs, and that quiescent-state forcing
-	 * will handle subsequent offline CPUs.
+	 * Apply per-leaf buffered online and offline operations to
+	 * the rcu_node tree. Note that this new grace period need not
+	 * wait for subsequent online CPUs, and that RCU hooks in the CPU
+	 * offlining path, when combined with checks in this function,
+	 * will handle CPUs that are currently going offline or that will
+	 * go offline later.  Please also refer to "Hotplug CPU" section
+	 * of RCU's Requirements documentation.
 	 */
 	rcu_state.gp_state = RCU_GP_ONOFF;
 	rcu_for_each_leaf_node(rnp) {
@@ -1810,6 +1841,10 @@ static bool rcu_gp_init(void)
 		WRITE_ONCE(rcu_state.gp_activity, jiffies);
 	}

+	// If strict, make all CPUs aware of new grace period.
+	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
+		on_each_cpu(rcu_strict_gp_boundary, NULL, 0);
+
 	return true;
 }

@@ -1898,7 +1933,7 @@ static void rcu_gp_fqs_loop(void)
 			break;
 		/* If time for quiescent-state forcing, do it. */
 		if (!time_after(rcu_state.jiffies_force_qs, jiffies) ||
-		    (gf & RCU_GP_FLAG_FQS)) {
+		    (gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) {
 			trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
 					       TPS("fqsstart"));
 			rcu_gp_fqs(first_gp_fqs);
@@ -2026,6 +2061,10 @@ static void rcu_gp_cleanup(void)
 			   rcu_state.gp_flags & RCU_GP_FLAG_INIT);
 	}
 	raw_spin_unlock_irq_rcu_node(rnp);
+
+	// If strict, make all CPUs aware of the end of the old grace period.
+	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
+		on_each_cpu(rcu_strict_gp_boundary, NULL, 0);
 }

 /*
@@ -2204,7 +2243,7 @@ rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
 * structure.  This must be called from the specified CPU.
 */
 static void
-rcu_report_qs_rdp(int cpu, struct rcu_data *rdp)
+rcu_report_qs_rdp(struct rcu_data *rdp)
 {
 	unsigned long flags;
 	unsigned long mask;
@@ -2213,6 +2252,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_data *rdp)
 			       rcu_segcblist_is_offloaded(&rdp->cblist);
 	struct rcu_node *rnp;

+	WARN_ON_ONCE(rdp->cpu != smp_processor_id());
 	rnp = rdp->mynode;
 	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq ||
@@ -2229,8 +2269,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_data *rdp)
 		return;
 	}
 	mask = rdp->grpmask;
-	if (rdp->cpu == smp_processor_id())
-		rdp->core_needs_qs = false;
+	rdp->core_needs_qs = false;
 	if ((rnp->qsmask & mask) == 0) {
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	} else {
@@ -2279,7 +2318,7 @@ rcu_check_quiescent_state(struct rcu_data *rdp)
 	 * Tell RCU we are done (but rcu_report_qs_rdp() will be the
 	 * judge of that).
 	 */
-	rcu_report_qs_rdp(rdp->cpu, rdp);
+	rcu_report_qs_rdp(rdp);
 }

 /*
@@ -2376,6 +2415,7 @@ int rcutree_dead_cpu(unsigned int cpu)
 */
 static void rcu_do_batch(struct rcu_data *rdp)
 {
+	int div;
 	unsigned long flags;
 	const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
 			       rcu_segcblist_is_offloaded(&rdp->cblist);
@@ -2404,9 +2444,15 @@ static void rcu_do_batch(struct rcu_data *rdp)
 	rcu_nocb_lock(rdp);
 	WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
 	pending = rcu_segcblist_n_cbs(&rdp->cblist);
-	bl = max(rdp->blimit, pending >> rcu_divisor);
-	if (unlikely(bl > 100))
-		tlimit = local_clock() + rcu_resched_ns;
+	div = READ_ONCE(rcu_divisor);
+	div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div;
+	bl = max(rdp->blimit, pending >> div);
+	if (unlikely(bl > 100)) {
+		long rrn = READ_ONCE(rcu_resched_ns);
+
+		rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn;
+		tlimit = local_clock() + rrn;
+	}
 	trace_rcu_batch_start(rcu_state.name,
 			      rcu_segcblist_n_cbs(&rdp->cblist), bl);
 	rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl);
@@ -2547,8 +2593,7 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp))
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		rcu_state.cbovldnext |= !!rnp->cbovldmask;
 		if (rnp->qsmask == 0) {
-			if (!IS_ENABLED(CONFIG_PREEMPT_RCU) ||
-			    rcu_preempt_blocked_readers_cgp(rnp)) {
+			if (rcu_preempt_blocked_readers_cgp(rnp)) {
 				/*
 				 * No point in scanning bits because they
 				 * are all zero.  But we might need to
@@ -2616,6 +2661,14 @@ void rcu_force_quiescent_state(void)
 }
 EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);

+// Workqueue handler for an RCU reader for kernels enforcing struct RCU
+// grace periods.
+static void strict_work_handler(struct work_struct *work)
+{
+	rcu_read_lock();
+	rcu_read_unlock();
+}
+
 /* Perform RCU core processing work for the current CPU.  */
 static __latent_entropy void rcu_core(void)
 {
@@ -2660,6 +2713,10 @@ static __latent_entropy void rcu_core(void)
 	/* Do any needed deferred wakeups of rcuo kthreads. */
 	do_nocb_deferred_wakeup(rdp);
 	trace_rcu_utilization(TPS("End RCU core"));
+
+	// If strict GPs, schedule an RCU reader in a clean environment.
+	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
+		queue_work_on(rdp->cpu, rcu_gp_wq, &rdp->strict_work);
 }

 static void rcu_core_si(struct softirq_action *h)
@@ -3445,7 +3502,7 @@ kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
 	unsigned long count = 0;

 	/* Snapshot count of all CPUs */
-	for_each_online_cpu(cpu) {
+	for_each_possible_cpu(cpu) {
 		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);

 		count += READ_ONCE(krcp->count);
@@ -3460,7 +3517,7 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 	int cpu, freed = 0;
 	unsigned long flags;

-	for_each_online_cpu(cpu) {
+	for_each_possible_cpu(cpu) {
 		int count;
 		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);

@@ -3493,7 +3550,7 @@ void __init kfree_rcu_scheduler_running(void)
 	int cpu;
 	unsigned long flags;

-	for_each_online_cpu(cpu) {
+	for_each_possible_cpu(cpu) {
 		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);

 		raw_spin_lock_irqsave(&krcp->lock, flags);
@@ -3857,6 +3914,7 @@ rcu_boot_init_percpu_data(int cpu)

 	/* Set up local state, ensuring consistent view of global state. */
 	rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
+	INIT_WORK(&rdp->strict_work, strict_work_handler);
 	WARN_ON_ONCE(rdp->dynticks_nesting != 1);
 	WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp)));
 	rdp->rcu_ofl_gp_seq = rcu_state.gp_seq;
@@ -3975,8 +4033,6 @@ int rcutree_offline_cpu(unsigned int cpu)
 	return 0;
 }

-static DEFINE_PER_CPU(int, rcu_cpu_started);
-
 /*
 * Mark the specified CPU as being online so that subsequent grace periods
 * (both expedited and normal) will wait on it.  Note that this means that
@@ -3996,12 +4052,11 @@ void rcu_cpu_starting(unsigned int cpu)
 	struct rcu_node *rnp;
 	bool newcpu;

-	if (per_cpu(rcu_cpu_started, cpu))
-		return;
-
-	per_cpu(rcu_cpu_started, cpu) = 1;
-
 	rdp = per_cpu_ptr(&rcu_data, cpu);
+	if (rdp->cpu_started)
+		return;
+	rdp->cpu_started = true;
+
 	rnp = rdp->mynode;
 	mask = rdp->grpmask;
 	raw_spin_lock_irqsave_rcu_node(rnp, flags);
@@ -4061,7 +4116,7 @@ void rcu_report_dead(unsigned int cpu)
 	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	raw_spin_unlock(&rcu_state.ofl_lock);

-	per_cpu(rcu_cpu_started, cpu) = 0;
+	rdp->cpu_started = false;
 }

 /*
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -156,6 +156,7 @@ struct rcu_data {
 	bool		beenonline;	/* CPU online at least once. */
 	bool		gpwrap;		/* Possible ->gp_seq wrap. */
 	bool		exp_deferred_qs; /* This CPU awaiting a deferred QS? */
+	bool		cpu_started;	/* RCU watching this onlining CPU. */
 	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */
 	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */
 	unsigned long	ticks_this_gp;	/* The number of scheduling-clock */
@@ -164,6 +165,7 @@ struct rcu_data {
 					/* period it is aware of. */
 	struct irq_work defer_qs_iw;	/* Obtain later scheduler attention. */
 	bool defer_qs_iw_pending;	/* Scheduler attention pending? */
+	struct work_struct strict_work;	/* Schedule readers for strict GPs. */

 	/* 2) batch handling */
 	struct rcu_segcblist cblist;	/* Segmented callback list, with */
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -732,11 +732,9 @@ static void rcu_exp_need_qs(void)
 /* Invoked on each online non-idle CPU for expedited quiescent state. */
 static void rcu_exp_handler(void *unused)
 {
-	struct rcu_data *rdp;
-	struct rcu_node *rnp;
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+	struct rcu_node *rnp = rdp->mynode;

-	rdp = this_cpu_ptr(&rcu_data);
-	rnp = rdp->mynode;
 	if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
 	    __this_cpu_read(rcu_data.cpu_no_qs.b.exp))
 		return;
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -36,6 +36,8 @@ static void __init rcu_bootup_announce_oddness(void)
 		pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n");
 	if (IS_ENABLED(CONFIG_PROVE_RCU))
 		pr_info("\tRCU lockdep checking is enabled.\n");
+	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
+		pr_info("\tRCU strict (and thus non-scalable) grace periods enabled.\n");
 	if (RCU_NUM_LVLS >= 4)
 		pr_info("\tFour(or more)-level hierarchy is enabled.\n");
 	if (RCU_FANOUT_LEAF != 16)
@@ -374,6 +376,8 @@ void __rcu_read_lock(void)
 	rcu_preempt_read_enter();
 	if (IS_ENABLED(CONFIG_PROVE_LOCKING))
 		WARN_ON_ONCE(rcu_preempt_depth() > RCU_NEST_PMAX);
+	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) && rcu_state.gp_kthread)
+		WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true);
 	barrier();  /* critical section after entry code. */
 }
 EXPORT_SYMBOL_GPL(__rcu_read_lock);
@@ -455,8 +459,14 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 		return;
 	}
 	t->rcu_read_unlock_special.s = 0;
-	if (special.b.need_qs)
-		rcu_qs();
+	if (special.b.need_qs) {
+		if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) {
+			rcu_report_qs_rdp(rdp);
+			udelay(rcu_unlock_delay);
+		} else {
+			rcu_qs();
+		}
+	}

 	/*
 	 * Respond to a request by an expedited grace period for a
@@ -768,6 +778,24 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)

 #else /* #ifdef CONFIG_PREEMPT_RCU */

+/*
+ * If strict grace periods are enabled, and if the calling
+ * __rcu_read_unlock() marks the beginning of a quiescent state, immediately
+ * report that quiescent state and, if requested, spin for a bit.
+ */
+void rcu_read_unlock_strict(void)
+{
+	struct rcu_data *rdp;
+
+	if (!IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ||
+	   irqs_disabled() || preempt_count() || !rcu_state.gp_kthread)
+		return;
+	rdp = this_cpu_ptr(&rcu_data);
+	rcu_report_qs_rdp(rdp);
+	udelay(rcu_unlock_delay);
+}
+EXPORT_SYMBOL_GPL(rcu_read_unlock_strict);
+
 /*
 * Tell them what RCU they are running.
 */
@@ -1926,6 +1954,7 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
 	 * nearest grace period (if any) to wait for next.  The CB kthreads
 	 * and the global grace-period kthread are awakened if needed.
 	 */
+	WARN_ON_ONCE(my_rdp->nocb_gp_rdp != my_rdp);
 	for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_cb_rdp) {
 		trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check"));
 		rcu_nocb_lock_irqsave(rdp, flags);
@@ -2411,13 +2440,12 @@ static void show_rcu_nocb_state(struct rcu_data *rdp)
 		return;

 	waslocked = raw_spin_is_locked(&rdp->nocb_gp_lock);
-	wastimer = timer_pending(&rdp->nocb_timer);
+	wastimer = timer_pending(&rdp->nocb_bypass_timer);
 	wassleep = swait_active(&rdp->nocb_gp_wq);
-	if (!rdp->nocb_defer_wakeup && !rdp->nocb_gp_sleep &&
-	    !waslocked && !wastimer && !wassleep)
+	if (!rdp->nocb_gp_sleep && !waslocked && !wastimer && !wassleep)
 		return;  /* Nothing untowards. */

-	pr_info("   !!! %c%c%c%c %c\n",
+	pr_info("   nocb GP activity on CB-only CPU!!! %c%c%c%c %c\n",
 		"lL"[waslocked],
 		"dD"[!!rdp->nocb_defer_wakeup],
 		"tT"[wastimer],
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -158,7 +158,7 @@ static void rcu_stall_kick_kthreads(void)
 {
 	unsigned long j;

-	if (!rcu_kick_kthreads)
+	if (!READ_ONCE(rcu_kick_kthreads))
 		return;
 	j = READ_ONCE(rcu_state.jiffies_kick_kthreads);
 	if (time_after(jiffies, j) && rcu_state.gp_kthread &&
@@ -580,7 +580,7 @@ static void check_cpu_stall(struct rcu_data *rdp)
 	unsigned long js;
 	struct rcu_node *rnp;

-	if ((rcu_stall_is_suppressed() && !rcu_kick_kthreads) ||
+	if ((rcu_stall_is_suppressed() && !READ_ONCE(rcu_kick_kthreads)) ||
 	    !rcu_gp_in_progress())
 		return;
 	rcu_stall_kick_kthreads();
@@ -623,7 +623,7 @@ static void check_cpu_stall(struct rcu_data *rdp)

 		/* We haven't checked in, so go dump stack. */
 		print_cpu_stall(gps);
-		if (rcu_cpu_stall_ftrace_dump)
+		if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
 			rcu_ftrace_dump(DUMP_ALL);

 	} else if (rcu_gp_in_progress() &&
@@ -632,7 +632,7 @@ static void check_cpu_stall(struct rcu_data *rdp)

 		/* They had a few time units to dump stack, so complain. */
 		print_other_cpu_stall(gs2, gps);
-		if (rcu_cpu_stall_ftrace_dump)
+		if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
 			rcu_ftrace_dump(DUMP_ALL);
 	}
 }
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -53,19 +53,6 @@
 #endif
 #define MODULE_PARAM_PREFIX "rcupdate."

-#ifndef data_race
-#define data_race(expr)							\
-	({								\
-		expr;							\
-	})
-#endif
-#ifndef ASSERT_EXCLUSIVE_WRITER
-#define ASSERT_EXCLUSIVE_WRITER(var) do { } while (0)
-#endif
-#ifndef ASSERT_EXCLUSIVE_ACCESS
-#define ASSERT_EXCLUSIVE_ACCESS(var) do { } while (0)
-#endif
-
 #ifndef CONFIG_TINY_RCU
 module_param(rcu_expedited, int, 0);
 module_param(rcu_normal, int, 0);