1 files changed, 452 insertions, 100 deletions

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 65095664f5c5..7a893d51d02b 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -55,22 +55,24 @@ MODULE_DESCRIPTION("Read-Copy Update module-based torture test facility");
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");
 
-/* Bits for ->extendables field, extendables param, and related definitions. */
-#define RCUTORTURE_RDR_SHIFT_1	 8	/* Put SRCU index in upper bits. */
-#define RCUTORTURE_RDR_MASK_1	 (0xff << RCUTORTURE_RDR_SHIFT_1)
-#define RCUTORTURE_RDR_SHIFT_2	 16	/* Put SRCU index in upper bits. */
-#define RCUTORTURE_RDR_MASK_2	 (0xff << RCUTORTURE_RDR_SHIFT_2)
-#define RCUTORTURE_RDR_BH	 0x01	/* Extend readers by disabling bh. */
-#define RCUTORTURE_RDR_IRQ	 0x02	/*  ... disabling interrupts. */
-#define RCUTORTURE_RDR_PREEMPT	 0x04	/*  ... disabling preemption. */
-#define RCUTORTURE_RDR_RBH	 0x08	/*  ... rcu_read_lock_bh(). */
-#define RCUTORTURE_RDR_SCHED	 0x10	/*  ... rcu_read_lock_sched(). */
-#define RCUTORTURE_RDR_RCU_1	 0x20	/*  ... entering another RCU reader. */
-#define RCUTORTURE_RDR_RCU_2	 0x40	/*  ... entering another RCU reader. */
-#define RCUTORTURE_RDR_NBITS	 7	/* Number of bits defined above. */
-#define RCUTORTURE_MAX_EXTEND	 \
+// Bits for ->extendables field, extendables param, and related definitions.
+#define RCUTORTURE_RDR_SHIFT_1	8	// Put SRCU index in upper bits.
+#define RCUTORTURE_RDR_MASK_1	(0xff << RCUTORTURE_RDR_SHIFT_1)
+#define RCUTORTURE_RDR_SHIFT_2	16	// Put SRCU index in upper bits.
+#define RCUTORTURE_RDR_MASK_2	(0xff << RCUTORTURE_RDR_SHIFT_2)
+#define RCUTORTURE_RDR_BH	0x01	// Extend readers by disabling bh.
+#define RCUTORTURE_RDR_IRQ	0x02	//  ... disabling interrupts.
+#define RCUTORTURE_RDR_PREEMPT	0x04	//  ... disabling preemption.
+#define RCUTORTURE_RDR_RBH	0x08	//  ... rcu_read_lock_bh().
+#define RCUTORTURE_RDR_SCHED	0x10	//  ... rcu_read_lock_sched().
+#define RCUTORTURE_RDR_RCU_1	0x20	//  ... entering another RCU reader.
+#define RCUTORTURE_RDR_RCU_2	0x40	//  ... entering another RCU reader.
+#define RCUTORTURE_RDR_UPDOWN	0x80	//  ... up-read from task, down-read from timer.
+					//	Note: Manual start, automatic end.
+#define RCUTORTURE_RDR_NBITS	8	// Number of bits defined above.
+#define RCUTORTURE_MAX_EXTEND	\
 	(RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \
-	 RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)
+	 RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)  // Intentionally omit RCUTORTURE_RDR_UPDOWN.
 #define RCUTORTURE_RDR_ALLBITS	\
 	(RCUTORTURE_MAX_EXTEND | RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2 | \
 	 RCUTORTURE_RDR_MASK_1 | RCUTORTURE_RDR_MASK_2)
@@ -110,11 +112,16 @@ 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, n_up_down, 32, "# of concurrent up/down hrtimer-based RCU readers");
 torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
 torture_param(int, nreaders, -1, "Number of RCU reader threads");
 torture_param(int, object_debug, 0, "Enable debug-object double call_rcu() testing");
 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
 torture_param(int, onoff_interval, 0, "Time between CPU hotplugs (jiffies), 0=disable");
+torture_param(bool, gpwrap_lag, true, "Enable grace-period wrap lag testing");
+torture_param(int, gpwrap_lag_gps, 8, "Value to set for set_gpwrap_lag during an active testing period.");
+torture_param(int, gpwrap_lag_cycle_mins, 30, "Total cycle duration for gpwrap lag testing (in minutes)");
+torture_param(int, gpwrap_lag_active_mins, 5, "Duration for which gpwrap lag is active within each cycle (in minutes)");
 torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disable");
 torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)");
 torture_param(int, preempt_duration, 0, "Preemption duration (ms), zero to disable");
@@ -152,6 +159,7 @@ static int nrealfakewriters;
 static struct task_struct *writer_task;
 static struct task_struct **fakewriter_tasks;
 static struct task_struct **reader_tasks;
+static struct task_struct *updown_task;
 static struct task_struct **nocb_tasks;
 static struct task_struct *stats_task;
 static struct task_struct *fqs_task;
@@ -374,6 +382,8 @@ struct rcu_torture_ops {
 	void (*readunlock)(int idx);
 	int (*readlock_held)(void);   // lockdep.
 	int (*readlock_nesting)(void); // actual nesting, if available, -1 if not.
+	int (*down_read)(void);
+	void (*up_read)(int idx);
 	unsigned long (*get_gp_seq)(void);
 	unsigned long (*gp_diff)(unsigned long new, unsigned long old);
 	void (*deferred_free)(struct rcu_torture *p);
@@ -413,6 +423,8 @@ struct rcu_torture_ops {
 	bool (*reader_blocked)(void);
 	unsigned long long (*gather_gp_seqs)(void);
 	void (*format_gp_seqs)(unsigned long long seqs, char *cp, size_t len);
+	void (*set_gpwrap_lag)(unsigned long lag);
+	int (*get_gpwrap_count)(int cpu);
 	long cbflood_max;
 	int irq_capable;
 	int can_boost;
@@ -421,6 +433,7 @@ struct rcu_torture_ops {
 	int no_pi_lock;
 	int debug_objects;
 	int start_poll_irqsoff;
+	int have_up_down;
 	const char *name;
 };
 
@@ -458,7 +471,7 @@ rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 	    !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
 		started = cur_ops->get_gp_seq();
 		ts = rcu_trace_clock_local();
-		if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK))
+		if ((preempt_count() & HARDIRQ_MASK) || softirq_count())
 			longdelay_ms = 5; /* Avoid triggering BH limits. */
 		mdelay(longdelay_ms);
 		rtrsp->rt_delay_ms = longdelay_ms;
@@ -619,6 +632,8 @@ static struct rcu_torture_ops rcu_ops = {
 				  : NULL,
 	.gather_gp_seqs		= rcutorture_gather_gp_seqs,
 	.format_gp_seqs		= rcutorture_format_gp_seqs,
+	.set_gpwrap_lag		= rcu_set_gpwrap_lag,
+	.get_gpwrap_count	= rcu_get_gpwrap_count,
 	.irq_capable		= 1,
 	.can_boost		= IS_ENABLED(CONFIG_RCU_BOOST),
 	.extendables		= RCUTORTURE_MAX_EXTEND,
@@ -703,11 +718,6 @@ static int srcu_torture_read_lock(void)
 		WARN_ON_ONCE(idx & ~0x1);
 		ret += idx << 1;
 	}
-	if (reader_flavor & SRCU_READ_FLAVOR_LITE) {
-		idx = srcu_read_lock_lite(srcu_ctlp);
-		WARN_ON_ONCE(idx & ~0x1);
-		ret += idx << 2;
-	}
 	if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
 		scp = srcu_read_lock_fast(srcu_ctlp);
 		idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
@@ -741,8 +751,6 @@ static void srcu_torture_read_unlock(int idx)
 	WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
 	if (reader_flavor & SRCU_READ_FLAVOR_FAST)
 		srcu_read_unlock_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
-	if (reader_flavor & SRCU_READ_FLAVOR_LITE)
-		srcu_read_unlock_lite(srcu_ctlp, (idx & 0x4) >> 2);
 	if (reader_flavor & SRCU_READ_FLAVOR_NMI)
 		srcu_read_unlock_nmisafe(srcu_ctlp, (idx & 0x2) >> 1);
 	if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL))
@@ -754,6 +762,50 @@ static int torture_srcu_read_lock_held(void)
 	return srcu_read_lock_held(srcu_ctlp);
 }
 
+static bool srcu_torture_have_up_down(void)
+{
+	int rf = reader_flavor;
+
+	if (!rf)
+		rf = SRCU_READ_FLAVOR_NORMAL;
+	return !!(cur_ops->have_up_down & rf);
+}
+
+static int srcu_torture_down_read(void)
+{
+	int idx;
+	struct srcu_ctr __percpu *scp;
+
+	WARN_ON_ONCE(reader_flavor & ~SRCU_READ_FLAVOR_ALL);
+	WARN_ON_ONCE(reader_flavor & (reader_flavor - 1));
+
+	if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL)) {
+		idx = srcu_down_read(srcu_ctlp);
+		WARN_ON_ONCE(idx & ~0x1);
+		return idx;
+	}
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
+		scp = srcu_down_read_fast(srcu_ctlp);
+		idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
+		WARN_ON_ONCE(idx & ~0x1);
+		return idx << 3;
+	}
+	WARN_ON_ONCE(1);
+	return 0;
+}
+
+static void srcu_torture_up_read(int idx)
+{
+	WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST)
+		srcu_up_read_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
+	else if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) ||
+		 !(reader_flavor & SRCU_READ_FLAVOR_ALL))
+		srcu_up_read(srcu_ctlp, idx & 0x1);
+	else
+		WARN_ON_ONCE(1);
+}
+
 static unsigned long srcu_torture_completed(void)
 {
 	return srcu_batches_completed(srcu_ctlp);
@@ -811,6 +863,8 @@ static struct rcu_torture_ops srcu_ops = {
 	.readlock	= srcu_torture_read_lock,
 	.read_delay	= srcu_read_delay,
 	.readunlock	= srcu_torture_read_unlock,
+	.down_read	= srcu_torture_down_read,
+	.up_read	= srcu_torture_up_read,
 	.readlock_held	= torture_srcu_read_lock_held,
 	.get_gp_seq	= srcu_torture_completed,
 	.gp_diff	= rcu_seq_diff,
@@ -831,6 +885,8 @@ static struct rcu_torture_ops srcu_ops = {
 	.irq_capable	= 1,
 	.no_pi_lock	= IS_ENABLED(CONFIG_TINY_SRCU),
 	.debug_objects	= 1,
+	.have_up_down	= IS_ENABLED(CONFIG_TINY_SRCU)
+				? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST,
 	.name		= "srcu"
 };
 
@@ -856,6 +912,8 @@ static struct rcu_torture_ops srcud_ops = {
 	.read_delay	= srcu_read_delay,
 	.readunlock	= srcu_torture_read_unlock,
 	.readlock_held	= torture_srcu_read_lock_held,
+	.down_read	= srcu_torture_down_read,
+	.up_read	= srcu_torture_up_read,
 	.get_gp_seq	= srcu_torture_completed,
 	.gp_diff	= rcu_seq_diff,
 	.deferred_free	= srcu_torture_deferred_free,
@@ -875,6 +933,8 @@ static struct rcu_torture_ops srcud_ops = {
 	.irq_capable	= 1,
 	.no_pi_lock	= IS_ENABLED(CONFIG_TINY_SRCU),
 	.debug_objects	= 1,
+	.have_up_down	= IS_ENABLED(CONFIG_TINY_SRCU)
+				? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST,
 	.name		= "srcud"
 };
 
@@ -902,7 +962,8 @@ static struct rcu_torture_ops busted_srcud_ops = {
 
 /*
  * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
- * This implementation does not necessarily work well with CPU hotplug.
+ * This implementation does not work well with CPU hotplug nor
+ * with rcutorture's shuffling.
  */
 
 static void synchronize_rcu_trivial(void)
@@ -915,6 +976,16 @@ static void synchronize_rcu_trivial(void)
 	}
 }
 
+static void rcu_sync_torture_init_trivial(void)
+{
+	rcu_sync_torture_init();
+	// if (onoff_interval || shuffle_interval) {
+	if (WARN_ONCE(onoff_interval || shuffle_interval, "%s: Non-zero onoff_interval (%d) or shuffle_interval (%d) breaks trivial RCU, resetting to zero", __func__, onoff_interval, shuffle_interval)) {
+		onoff_interval = 0;
+		shuffle_interval = 0;
+	}
+}
+
 static int rcu_torture_read_lock_trivial(void)
 {
 	preempt_disable();
@@ -928,7 +999,7 @@ static void rcu_torture_read_unlock_trivial(int idx)
 
 static struct rcu_torture_ops trivial_ops = {
 	.ttype		= RCU_TRIVIAL_FLAVOR,
-	.init		= rcu_sync_torture_init,
+	.init		= rcu_sync_torture_init_trivial,
 	.readlock	= rcu_torture_read_lock_trivial,
 	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
 	.readunlock	= rcu_torture_read_unlock_trivial,
@@ -1714,6 +1785,7 @@ rcu_torture_writer(void *arg)
 						cur_ops->gp_kthread_dbg();
 					WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
 					rcu_ftrace_dump(DUMP_ALL);
+					break;
 				}
 		if (stutter_waited)
 			sched_set_normal(current, oldnice);
@@ -1907,14 +1979,14 @@ static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp,
 
 // Verify the specified RCUTORTURE_RDR* state.
 #define ROEC_ARGS "%s %s: Current %#x  To add %#x  To remove %#x  preempt_count() %#x\n", __func__, s, curstate, new, old, preempt_count()
-static void rcutorture_one_extend_check(char *s, int curstate, int new, int old, bool insoftirq)
+static void rcutorture_one_extend_check(char *s, int curstate, int new, int old)
 {
 	int mask;
 
-	if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST_CHK_RDR_STATE))
+	if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST_CHK_RDR_STATE) || in_nmi())
 		return;
 
-	WARN_ONCE(!(curstate & RCUTORTURE_RDR_IRQ) && irqs_disabled(), ROEC_ARGS);
+	WARN_ONCE(!(curstate & RCUTORTURE_RDR_IRQ) && irqs_disabled() && !in_hardirq(), ROEC_ARGS);
 	WARN_ONCE((curstate & RCUTORTURE_RDR_IRQ) && !irqs_disabled(), ROEC_ARGS);
 
 	// If CONFIG_PREEMPT_COUNT=n, further checks are unreliable.
@@ -1922,21 +1994,21 @@ static void rcutorture_one_extend_check(char *s, int curstate, int new, int old,
 		return;
 
 	WARN_ONCE((curstate & (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH)) &&
-		  !(preempt_count() & SOFTIRQ_MASK), ROEC_ARGS);
+		  !softirq_count(), ROEC_ARGS);
 	WARN_ONCE((curstate & (RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED)) &&
 		  !(preempt_count() & PREEMPT_MASK), ROEC_ARGS);
 	WARN_ONCE(cur_ops->readlock_nesting &&
 		  (curstate & (RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2)) &&
 		  cur_ops->readlock_nesting() == 0, ROEC_ARGS);
 
-	// Timer handlers have all sorts of stuff disabled, so ignore
+	// Interrupt handlers have all sorts of stuff disabled, so ignore
 	// unintended disabling.
-	if (insoftirq)
+	if (in_serving_softirq() || in_hardirq())
 		return;
 
 	WARN_ONCE(cur_ops->extendables &&
 		  !(curstate & (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH)) &&
-		  (preempt_count() & SOFTIRQ_MASK), ROEC_ARGS);
+		  softirq_count(), ROEC_ARGS);
 
 	/*
 	 * non-preemptible RCU in a preemptible kernel uses preempt_disable()
@@ -1957,6 +2029,9 @@ static void rcutorture_one_extend_check(char *s, int curstate, int new, int old,
 	if (!IS_ENABLED(CONFIG_PREEMPT_RCU))
 		mask |= RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;
 
+	if (IS_ENABLED(CONFIG_PREEMPT_RT) && softirq_count())
+		mask |= RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
+
 	WARN_ONCE(cur_ops->readlock_nesting && !(curstate & mask) &&
 		  cur_ops->readlock_nesting() > 0, ROEC_ARGS);
 }
@@ -1970,8 +2045,7 @@ static void rcutorture_one_extend_check(char *s, int curstate, int new, int old,
  * beginning or end of the critical section and if there was actually a
  * change, do a ->read_delay().
  */
-static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
-				  struct torture_random_state *trsp,
+static void rcutorture_one_extend(int *readstate, int newstate, struct torture_random_state *trsp,
 				  struct rt_read_seg *rtrsp)
 {
 	bool first;
@@ -1985,8 +2059,8 @@ static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
 
 	first = idxold1 == 0;
 	WARN_ON_ONCE(idxold2 < 0);
-	WARN_ON_ONCE(idxold2 & ~RCUTORTURE_RDR_ALLBITS);
-	rcutorture_one_extend_check("before change", idxold1, statesnew, statesold, insoftirq);
+	WARN_ON_ONCE(idxold2 & ~(RCUTORTURE_RDR_ALLBITS | RCUTORTURE_RDR_UPDOWN));
+	rcutorture_one_extend_check("before change", idxold1, statesnew, statesold);
 	rtrsp->rt_readstate = newstate;
 
 	/* First, put new protection in place to avoid critical-section gap. */
@@ -2006,8 +2080,7 @@ static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
 		idxnew2 = (cur_ops->readlock() << RCUTORTURE_RDR_SHIFT_2) & RCUTORTURE_RDR_MASK_2;
 
 	// Complain unless both the old and the new protection is in place.
-	rcutorture_one_extend_check("during change",
-				    idxold1 | statesnew, statesnew, statesold, insoftirq);
+	rcutorture_one_extend_check("during change", idxold1 | statesnew, statesnew, statesold);
 
 	// Sample CPU under both sets of protections to reduce confusion.
 	if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_CPU)) {
@@ -2061,6 +2134,11 @@ static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
 		if (lockit)
 			raw_spin_unlock_irqrestore(&current->pi_lock, flags);
 	}
+	if (statesold & RCUTORTURE_RDR_UPDOWN) {
+		cur_ops->up_read((idxold1 & RCUTORTURE_RDR_MASK_1) >> RCUTORTURE_RDR_SHIFT_1);
+		WARN_ON_ONCE(idxnew1 != -1);
+		idxold1 = 0;
+	}
 
 	/* Delay if neither beginning nor end and there was a change. */
 	if ((statesnew || statesold) && *readstate && newstate)
@@ -2077,7 +2155,7 @@ static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
 	WARN_ON_ONCE(*readstate < 0);
 	if (WARN_ON_ONCE(*readstate & ~RCUTORTURE_RDR_ALLBITS))
 		pr_info("Unexpected readstate value of %#x\n", *readstate);
-	rcutorture_one_extend_check("after change", *readstate, statesnew, statesold, insoftirq);
+	rcutorture_one_extend_check("after change", *readstate, statesnew, statesold);
 }
 
 /* Return the biggest extendables mask given current RCU and boot parameters. */
@@ -2144,8 +2222,7 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
  * critical section.
  */
 static struct rt_read_seg *
-rcutorture_loop_extend(int *readstate, bool insoftirq, struct torture_random_state *trsp,
-		       struct rt_read_seg *rtrsp)
+rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp, struct rt_read_seg *rtrsp)
 {
 	int i;
 	int j;
@@ -2159,58 +2236,77 @@ rcutorture_loop_extend(int *readstate, bool insoftirq, struct torture_random_sta
 	i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
 	for (j = 0; j < i; j++) {
 		mask = rcutorture_extend_mask(*readstate, trsp);
-		rcutorture_one_extend(readstate, mask, insoftirq, trsp, &rtrsp[j]);
+		WARN_ON_ONCE(mask & RCUTORTURE_RDR_UPDOWN);
+		rcutorture_one_extend(readstate, mask, trsp, &rtrsp[j]);
 	}
 	return &rtrsp[j];
 }
 
-/*
- * Do one read-side critical section, returning false if there was
- * no data to read.  Can be invoked both from process context and
- * from a timer handler.
- */
-static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
-{
-	bool checkpolling = !(torture_random(trsp) & 0xfff);
+struct rcu_torture_one_read_state {
+	bool checkpolling;
 	unsigned long cookie;
 	struct rcu_gp_oldstate cookie_full;
-	int i;
 	unsigned long started;
-	unsigned long completed;
-	int newstate;
 	struct rcu_torture *p;
-	int pipe_count;
-	bool preempted = false;
-	int readstate = 0;
-	struct rt_read_seg rtseg[RCUTORTURE_RDR_MAX_SEGS] = { { 0 } };
-	struct rt_read_seg *rtrsp = &rtseg[0];
-	struct rt_read_seg *rtrsp1;
+	int readstate;
+	struct rt_read_seg rtseg[RCUTORTURE_RDR_MAX_SEGS];
+	struct rt_read_seg *rtrsp;
 	unsigned long long ts;
+};
 
-	WARN_ON_ONCE(!rcu_is_watching());
-	newstate = rcutorture_extend_mask(readstate, trsp);
-	rcutorture_one_extend(&readstate, newstate, myid < 0, trsp, rtrsp++);
-	if (checkpolling) {
+static void init_rcu_torture_one_read_state(struct rcu_torture_one_read_state *rtorsp,
+					    struct torture_random_state *trsp)
+{
+	memset(rtorsp, 0, sizeof(*rtorsp));
+	rtorsp->checkpolling = !(torture_random(trsp) & 0xfff);
+	rtorsp->rtrsp = &rtorsp->rtseg[0];
+}
+
+/*
+ * Set up the first segment of a series of overlapping read-side
+ * critical sections.  The caller must have actually initiated the
+ * outermost read-side critical section.
+ */
+static bool rcu_torture_one_read_start(struct rcu_torture_one_read_state *rtorsp,
+				       struct torture_random_state *trsp, long myid)
+{
+	if (rtorsp->checkpolling) {
 		if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
-			cookie = cur_ops->get_gp_state();
+			rtorsp->cookie = cur_ops->get_gp_state();
 		if (cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full)
-			cur_ops->get_gp_state_full(&cookie_full);
+			cur_ops->get_gp_state_full(&rtorsp->cookie_full);
 	}
-	started = cur_ops->get_gp_seq();
-	ts = rcu_trace_clock_local();
-	p = rcu_dereference_check(rcu_torture_current,
-				  !cur_ops->readlock_held || cur_ops->readlock_held());
-	if (p == NULL) {
+	rtorsp->started = cur_ops->get_gp_seq();
+	rtorsp->ts = rcu_trace_clock_local();
+	rtorsp->p = rcu_dereference_check(rcu_torture_current,
+					  !cur_ops->readlock_held || cur_ops->readlock_held() ||
+					  (rtorsp->readstate & RCUTORTURE_RDR_UPDOWN));
+	if (rtorsp->p == NULL) {
 		/* Wait for rcu_torture_writer to get underway */
-		rcutorture_one_extend(&readstate, 0, myid < 0, trsp, rtrsp);
+		rcutorture_one_extend(&rtorsp->readstate, 0, trsp, rtorsp->rtrsp);
 		return false;
 	}
-	if (p->rtort_mbtest == 0)
+	if (rtorsp->p->rtort_mbtest == 0)
 		atomic_inc(&n_rcu_torture_mberror);
-	rcu_torture_reader_do_mbchk(myid, p, trsp);
-	rtrsp = rcutorture_loop_extend(&readstate, myid < 0, trsp, rtrsp);
+	rcu_torture_reader_do_mbchk(myid, rtorsp->p, trsp);
+	return true;
+}
+
+/*
+ * Complete the last segment of a series of overlapping read-side
+ * critical sections and check for errors.
+ */
+static void rcu_torture_one_read_end(struct rcu_torture_one_read_state *rtorsp,
+				     struct torture_random_state *trsp)
+{
+	int i;
+	unsigned long completed;
+	int pipe_count;
+	bool preempted = false;
+	struct rt_read_seg *rtrsp1;
+
 	preempt_disable();
-	pipe_count = READ_ONCE(p->rtort_pipe_count);
+	pipe_count = READ_ONCE(rtorsp->p->rtort_pipe_count);
 	if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 		// Should not happen in a correct RCU implementation,
 		// happens quite often for torture_type=busted.
@@ -2218,28 +2314,28 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
 	}
 	completed = cur_ops->get_gp_seq();
 	if (pipe_count > 1) {
-		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
-					  ts, started, completed);
+		do_trace_rcu_torture_read(cur_ops->name, &rtorsp->p->rtort_rcu,
+					  rtorsp->ts, rtorsp->started, completed);
 		rcu_ftrace_dump(DUMP_ALL);
 	}
 	__this_cpu_inc(rcu_torture_count[pipe_count]);
-	completed = rcutorture_seq_diff(completed, started);
+	completed = rcutorture_seq_diff(completed, rtorsp->started);
 	if (completed > RCU_TORTURE_PIPE_LEN) {
 		/* Should not happen, but... */
 		completed = RCU_TORTURE_PIPE_LEN;
 	}
 	__this_cpu_inc(rcu_torture_batch[completed]);
 	preempt_enable();
-	if (checkpolling) {
+	if (rtorsp->checkpolling) {
 		if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
-			WARN_ONCE(cur_ops->poll_gp_state(cookie),
+			WARN_ONCE(cur_ops->poll_gp_state(rtorsp->cookie),
 				  "%s: Cookie check 2 failed %s(%d) %lu->%lu\n",
 				  __func__,
 				  rcu_torture_writer_state_getname(),
 				  rcu_torture_writer_state,
-				  cookie, cur_ops->get_gp_state());
+				  rtorsp->cookie, cur_ops->get_gp_state());
 		if (cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full)
-			WARN_ONCE(cur_ops->poll_gp_state_full(&cookie_full),
+			WARN_ONCE(cur_ops->poll_gp_state_full(&rtorsp->cookie_full),
 				  "%s: Cookie check 6 failed %s(%d) online %*pbl\n",
 				  __func__,
 				  rcu_torture_writer_state_getname(),
@@ -2248,21 +2344,43 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
 	}
 	if (cur_ops->reader_blocked)
 		preempted = cur_ops->reader_blocked();
-	rcutorture_one_extend(&readstate, 0, myid < 0, trsp, rtrsp);
-	WARN_ON_ONCE(readstate);
+	rcutorture_one_extend(&rtorsp->readstate, 0, trsp, rtorsp->rtrsp);
+	WARN_ON_ONCE(rtorsp->readstate);
 	// 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);
+	WARN_ON_ONCE(leakpointer && READ_ONCE(rtorsp->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)) {
 		i = 0;
-		for (rtrsp1 = &rtseg[0]; rtrsp1 < rtrsp; rtrsp1++)
+		for (rtrsp1 = &rtorsp->rtseg[0]; rtrsp1 < rtorsp->rtrsp; rtrsp1++)
 			err_segs[i++] = *rtrsp1;
 		rt_read_nsegs = i;
 		rt_read_preempted = preempted;
 	}
+}
+
+/*
+ * Do one read-side critical section, returning false if there was
+ * no data to read.  Can be invoked both from process context and
+ * from a timer handler.
+ */
+static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
+{
+	int newstate;
+	struct rcu_torture_one_read_state rtors;
 
+	WARN_ON_ONCE(!rcu_is_watching());
+	init_rcu_torture_one_read_state(&rtors, trsp);
+	newstate = rcutorture_extend_mask(rtors.readstate, trsp);
+	WARN_ON_ONCE(newstate & RCUTORTURE_RDR_UPDOWN);
+	rcutorture_one_extend(&rtors.readstate, newstate, trsp, rtors.rtrsp++);
+	if (!rcu_torture_one_read_start(&rtors, trsp, myid)) {
+		rcutorture_one_extend(&rtors.readstate, 0, trsp, rtors.rtrsp);
+		return false;
+	}
+	rtors.rtrsp = rcutorture_loop_extend(&rtors.readstate, trsp, rtors.rtrsp);
+	rcu_torture_one_read_end(&rtors, trsp);
 	return true;
 }
 
@@ -2307,7 +2425,7 @@ rcu_torture_reader(void *arg)
 	set_user_nice(current, MAX_NICE);
 	if (irqreader && cur_ops->irq_capable)
 		timer_setup_on_stack(&t, rcu_torture_timer, 0);
-	tick_dep_set_task(current, TICK_DEP_BIT_RCU);
+	tick_dep_set_task(current, TICK_DEP_BIT_RCU);  // CPU bound, so need tick.
 	do {
 		if (irqreader && cur_ops->irq_capable) {
 			if (!timer_pending(&t))
@@ -2324,14 +2442,160 @@ rcu_torture_reader(void *arg)
 		stutter_wait("rcu_torture_reader");
 	} while (!torture_must_stop());
 	if (irqreader && cur_ops->irq_capable) {
-		del_timer_sync(&t);
-		destroy_timer_on_stack(&t);
+		timer_delete_sync(&t);
+		timer_destroy_on_stack(&t);
 	}
 	tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
 	torture_kthread_stopping("rcu_torture_reader");
 	return 0;
 }
 
+struct rcu_torture_one_read_state_updown {
+	struct hrtimer rtorsu_hrt;
+	bool rtorsu_inuse;
+	ktime_t rtorsu_kt;
+	int rtorsu_cpu;
+	unsigned long rtorsu_j;
+	unsigned long rtorsu_ndowns;
+	unsigned long rtorsu_nups;
+	unsigned long rtorsu_nmigrates;
+	struct torture_random_state rtorsu_trs;
+	struct rcu_torture_one_read_state rtorsu_rtors;
+};
+
+static struct rcu_torture_one_read_state_updown *updownreaders;
+static DEFINE_TORTURE_RANDOM(rcu_torture_updown_rand);
+static int rcu_torture_updown(void *arg);
+
+static enum hrtimer_restart rcu_torture_updown_hrt(struct hrtimer *hrtp)
+{
+	int cpu = raw_smp_processor_id();
+	struct rcu_torture_one_read_state_updown *rtorsup;
+
+	rtorsup = container_of(hrtp, struct rcu_torture_one_read_state_updown, rtorsu_hrt);
+	rcu_torture_one_read_end(&rtorsup->rtorsu_rtors, &rtorsup->rtorsu_trs);
+	WARN_ONCE(rtorsup->rtorsu_nups >= rtorsup->rtorsu_ndowns, "%s: Up without matching down #%zu.\n", __func__, rtorsup - updownreaders);
+	WRITE_ONCE(rtorsup->rtorsu_nups, rtorsup->rtorsu_nups + 1);
+	WRITE_ONCE(rtorsup->rtorsu_nmigrates,
+		   rtorsup->rtorsu_nmigrates + (cpu != rtorsup->rtorsu_cpu));
+	smp_store_release(&rtorsup->rtorsu_inuse, false);
+	return HRTIMER_NORESTART;
+}
+
+static int rcu_torture_updown_init(void)
+{
+	int i;
+	struct torture_random_state *rand = &rcu_torture_updown_rand;
+	int ret;
+
+	if (n_up_down < 0)
+		return 0;
+	if (!srcu_torture_have_up_down()) {
+		VERBOSE_TOROUT_STRING("rcu_torture_updown_init: Disabling up/down reader tests due to lack of primitives");
+		return 0;
+	}
+	updownreaders = kcalloc(n_up_down, sizeof(*updownreaders), GFP_KERNEL);
+	if (!updownreaders) {
+		VERBOSE_TOROUT_STRING("rcu_torture_updown_init: Out of memory, disabling up/down reader tests");
+		return -ENOMEM;
+	}
+	for (i = 0; i < n_up_down; i++) {
+		init_rcu_torture_one_read_state(&updownreaders[i].rtorsu_rtors, rand);
+		hrtimer_setup(&updownreaders[i].rtorsu_hrt, rcu_torture_updown_hrt, CLOCK_MONOTONIC,
+			      HRTIMER_MODE_REL | HRTIMER_MODE_HARD);
+		torture_random_init(&updownreaders[i].rtorsu_trs);
+		init_rcu_torture_one_read_state(&updownreaders[i].rtorsu_rtors,
+						&updownreaders[i].rtorsu_trs);
+	}
+	ret = torture_create_kthread(rcu_torture_updown, rand, updown_task);
+	if (ret) {
+		kfree(updownreaders);
+		updownreaders = NULL;
+	}
+	return ret;
+}
+
+static void rcu_torture_updown_cleanup(void)
+{
+	struct rcu_torture_one_read_state_updown *rtorsup;
+
+	for (rtorsup = updownreaders; rtorsup < &updownreaders[n_up_down]; rtorsup++) {
+		if (!smp_load_acquire(&rtorsup->rtorsu_inuse))
+			continue;
+		if (hrtimer_cancel(&rtorsup->rtorsu_hrt) || WARN_ON_ONCE(rtorsup->rtorsu_inuse)) {
+			rcu_torture_one_read_end(&rtorsup->rtorsu_rtors, &rtorsup->rtorsu_trs);
+			WARN_ONCE(rtorsup->rtorsu_nups >= rtorsup->rtorsu_ndowns, "%s: Up without matching down #%zu.\n", __func__, rtorsup - updownreaders);
+			WRITE_ONCE(rtorsup->rtorsu_nups, rtorsup->rtorsu_nups + 1);
+			smp_store_release(&rtorsup->rtorsu_inuse, false);
+		}
+
+	}
+	kfree(updownreaders);
+	updownreaders = NULL;
+}
+
+// Do one reader for rcu_torture_updown().
+static void rcu_torture_updown_one(struct rcu_torture_one_read_state_updown *rtorsup)
+{
+	int idx;
+	int rawidx;
+	ktime_t t;
+
+	init_rcu_torture_one_read_state(&rtorsup->rtorsu_rtors, &rtorsup->rtorsu_trs);
+	rawidx = cur_ops->down_read();
+	WRITE_ONCE(rtorsup->rtorsu_ndowns, rtorsup->rtorsu_ndowns + 1);
+	idx = (rawidx << RCUTORTURE_RDR_SHIFT_1) & RCUTORTURE_RDR_MASK_1;
+	rtorsup->rtorsu_rtors.readstate = idx | RCUTORTURE_RDR_UPDOWN;
+	rtorsup->rtorsu_rtors.rtrsp++;
+	rtorsup->rtorsu_cpu = raw_smp_processor_id();
+	if (!rcu_torture_one_read_start(&rtorsup->rtorsu_rtors, &rtorsup->rtorsu_trs, -1)) {
+		WARN_ONCE(rtorsup->rtorsu_nups >= rtorsup->rtorsu_ndowns, "%s: Up without matching down #%zu.\n", __func__, rtorsup - updownreaders);
+		WRITE_ONCE(rtorsup->rtorsu_nups, rtorsup->rtorsu_nups + 1);
+		schedule_timeout_idle(HZ);
+		return;
+	}
+	smp_store_release(&rtorsup->rtorsu_inuse, true);
+	t = torture_random(&rtorsup->rtorsu_trs) & 0xfffff; // One per million.
+	if (t < 10 * 1000)
+		t = 200 * 1000 * 1000;
+	hrtimer_start(&rtorsup->rtorsu_hrt, t, HRTIMER_MODE_REL | HRTIMER_MODE_HARD);
+	smp_mb(); // Sample jiffies after posting hrtimer.
+	rtorsup->rtorsu_j = jiffies;  // Not used by hrtimer handler.
+	rtorsup->rtorsu_kt = t;
+}
+
+/*
+ * RCU torture up/down reader kthread, starting RCU readers in kthread
+ * context and ending them in hrtimer handlers.  Otherwise similar to
+ * rcu_torture_reader().
+ */
+static int
+rcu_torture_updown(void *arg)
+{
+	unsigned long j;
+	struct rcu_torture_one_read_state_updown *rtorsup;
+
+	VERBOSE_TOROUT_STRING("rcu_torture_updown task started");
+	do {
+		for (rtorsup = updownreaders; rtorsup < &updownreaders[n_up_down]; rtorsup++) {
+			if (torture_must_stop())
+				break;
+			j = smp_load_acquire(&jiffies); // Time before ->rtorsu_inuse.
+			if (smp_load_acquire(&rtorsup->rtorsu_inuse)) {
+				WARN_ONCE(time_after(j, rtorsup->rtorsu_j + 1 + HZ * 10),
+					  "hrtimer queued at jiffies %lu for %lld ns took %lu jiffies\n", rtorsup->rtorsu_j, rtorsup->rtorsu_kt, j - rtorsup->rtorsu_j);
+				continue;
+			}
+			rcu_torture_updown_one(rtorsup);
+		}
+		torture_hrtimeout_ms(1, 1000, &rcu_torture_updown_rand);
+		stutter_wait("rcu_torture_updown");
+	} while (!torture_must_stop());
+	rcu_torture_updown_cleanup();
+	torture_kthread_stopping("rcu_torture_updown");
+	return 0;
+}
+
 /*
  * Randomly Toggle CPUs' callback-offload state.  This uses hrtimers to
  * increase race probabilities and fuzzes the interval between toggling.
@@ -2394,6 +2658,11 @@ rcu_torture_stats_print(void)
 	int i;
 	long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 	long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+	long n_gpwraps = 0;
+	unsigned long ndowns = 0;
+	unsigned long nunexpired = 0;
+	unsigned long nmigrates = 0;
+	unsigned long nups = 0;
 	struct rcu_torture *rtcp;
 	static unsigned long rtcv_snap = ULONG_MAX;
 	static bool splatted;
@@ -2404,11 +2673,21 @@ rcu_torture_stats_print(void)
 			pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]);
 			batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
 		}
+		if (cur_ops->get_gpwrap_count)
+			n_gpwraps += cur_ops->get_gpwrap_count(cpu);
+	}
+	if (updownreaders) {
+		for (i = 0; i < n_up_down; i++) {
+			ndowns += READ_ONCE(updownreaders[i].rtorsu_ndowns);
+			nups += READ_ONCE(updownreaders[i].rtorsu_nups);
+			nunexpired += READ_ONCE(updownreaders[i].rtorsu_inuse);
+			nmigrates += READ_ONCE(updownreaders[i].rtorsu_nmigrates);
+		}
 	}
 	for (i = RCU_TORTURE_PIPE_LEN; i >= 0; i--) {
 		if (pipesummary[i] != 0)
 			break;
-	}
+	} // The value of variable "i" is used later, so don't clobber it!
 
 	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
 	rtcp = rcu_access_pointer(rcu_torture_current);
@@ -2429,14 +2708,17 @@ rcu_torture_stats_print(void)
 		n_rcu_torture_boost_failure,
 		n_rcu_torture_boosts,
 		atomic_long_read(&n_rcu_torture_timers));
+	if (updownreaders)
+		pr_cont("ndowns: %lu nups: %lu nhrt: %lu nmigrates: %lu ", ndowns, nups, nunexpired,  nmigrates);
 	torture_onoff_stats();
 	pr_cont("barrier: %ld/%ld:%ld ",
 		data_race(n_barrier_successes),
 		data_race(n_barrier_attempts),
 		data_race(n_rcu_torture_barrier_error));
 	pr_cont("read-exits: %ld ", data_race(n_read_exits)); // Statistic.
-	pr_cont("nocb-toggles: %ld:%ld\n",
+	pr_cont("nocb-toggles: %ld:%ld ",
 		atomic_long_read(&n_nocb_offload), atomic_long_read(&n_nocb_deoffload));
+	pr_cont("gpwraps: %ld\n", n_gpwraps);
 
 	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
 	if (atomic_read(&n_rcu_torture_mberror) ||
@@ -2582,7 +2864,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 "reader_flavor=%x "
 		 "nocbs_nthreads=%d nocbs_toggle=%d "
 		 "test_nmis=%d "
-		 "preempt_duration=%d preempt_interval=%d\n",
+		 "preempt_duration=%d preempt_interval=%d n_up_down=%d\n",
 		 torture_type, tag, nrealreaders, nrealfakewriters,
 		 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 		 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
@@ -2596,7 +2878,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 reader_flavor,
 		 nocbs_nthreads, nocbs_toggle,
 		 test_nmis,
-		 preempt_duration, preempt_interval);
+		 preempt_duration, preempt_interval, n_up_down);
 }
 
 static int rcutorture_booster_cleanup(unsigned int cpu)
@@ -3036,7 +3318,7 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
 	cver = READ_ONCE(rcu_torture_current_version);
 	gps = cur_ops->get_gp_seq();
 	rfp->rcu_launder_gp_seq_start = gps;
-	tick_dep_set_task(current, TICK_DEP_BIT_RCU);
+	tick_dep_set_task(current, TICK_DEP_BIT_RCU);  // CPU bound, so need tick.
 	while (time_before(jiffies, stopat) &&
 	       !shutdown_time_arrived() &&
 	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
@@ -3607,6 +3889,57 @@ static int rcu_torture_preempt(void *unused)
 
 static enum cpuhp_state rcutor_hp;
 
+static struct hrtimer gpwrap_lag_timer;
+static bool gpwrap_lag_active;
+
+/* Timer handler for toggling RCU grace-period sequence overflow test lag value */
+static enum hrtimer_restart rcu_gpwrap_lag_timer(struct hrtimer *timer)
+{
+	ktime_t next_delay;
+
+	if (gpwrap_lag_active) {
+		pr_alert("rcu-torture: Disabling gpwrap lag (value=0)\n");
+		cur_ops->set_gpwrap_lag(0);
+		gpwrap_lag_active = false;
+		next_delay = ktime_set((gpwrap_lag_cycle_mins - gpwrap_lag_active_mins) * 60, 0);
+	} else {
+		pr_alert("rcu-torture: Enabling gpwrap lag (value=%d)\n", gpwrap_lag_gps);
+		cur_ops->set_gpwrap_lag(gpwrap_lag_gps);
+		gpwrap_lag_active = true;
+		next_delay = ktime_set(gpwrap_lag_active_mins * 60, 0);
+	}
+
+	if (torture_must_stop_irq())
+		return HRTIMER_NORESTART;
+
+	hrtimer_forward_now(timer, next_delay);
+	return HRTIMER_RESTART;
+}
+
+static int rcu_gpwrap_lag_init(void)
+{
+	if (!gpwrap_lag)
+		return 0;
+
+	if (gpwrap_lag_cycle_mins <= 0 || gpwrap_lag_active_mins <= 0) {
+		pr_alert("rcu-torture: lag timing parameters must be positive\n");
+		return -EINVAL;
+	}
+
+	hrtimer_setup(&gpwrap_lag_timer, rcu_gpwrap_lag_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	gpwrap_lag_active = false;
+	hrtimer_start(&gpwrap_lag_timer,
+		      ktime_set((gpwrap_lag_cycle_mins - gpwrap_lag_active_mins) * 60, 0), HRTIMER_MODE_REL);
+
+	return 0;
+}
+
+static void rcu_gpwrap_lag_cleanup(void)
+{
+	hrtimer_cancel(&gpwrap_lag_timer);
+	cur_ops->set_gpwrap_lag(0);
+	gpwrap_lag_active = false;
+}
 static void
 rcu_torture_cleanup(void)
 {
@@ -3648,6 +3981,10 @@ rcu_torture_cleanup(void)
 		nocb_tasks = NULL;
 	}
 
+	if (updown_task) {
+		torture_stop_kthread(rcu_torture_updown, updown_task);
+		updown_task = NULL;
+	}
 	if (reader_tasks) {
 		for (i = 0; i < nrealreaders; i++)
 			torture_stop_kthread(rcu_torture_reader,
@@ -3776,6 +4113,9 @@ rcu_torture_cleanup(void)
 	torture_cleanup_end();
 	if (cur_ops->gp_slow_unregister)
 		cur_ops->gp_slow_unregister(NULL);
+
+	if (gpwrap_lag && cur_ops->set_gpwrap_lag)
+		rcu_gpwrap_lag_cleanup();
 }
 
 static void rcu_torture_leak_cb(struct rcu_head *rhp)
@@ -4141,11 +4481,6 @@ rcu_torture_init(void)
 	/* Start up the kthreads. */
 
 	rcu_torture_write_types();
-	firsterr = torture_create_kthread(rcu_torture_writer, NULL,
-					  writer_task);
-	if (torture_init_error(firsterr))
-		goto unwind;
-
 	if (nrealfakewriters > 0) {
 		fakewriter_tasks = kcalloc(nrealfakewriters,
 					   sizeof(fakewriter_tasks[0]),
@@ -4178,6 +4513,15 @@ rcu_torture_init(void)
 		if (torture_init_error(firsterr))
 			goto unwind;
 	}
+
+	firsterr = torture_create_kthread(rcu_torture_writer, NULL,
+					  writer_task);
+	if (torture_init_error(firsterr))
+		goto unwind;
+
+	firsterr = rcu_torture_updown_init();
+	if (torture_init_error(firsterr))
+		goto unwind;
 	nrealnocbers = nocbs_nthreads;
 	if (WARN_ON(nrealnocbers < 0))
 		nrealnocbers = 1;
@@ -4272,9 +4616,17 @@ rcu_torture_init(void)
 	}
 	if (object_debug)
 		rcu_test_debug_objects();
-	torture_init_end();
+
 	if (cur_ops->gp_slow_register && !WARN_ON_ONCE(!cur_ops->gp_slow_unregister))
 		cur_ops->gp_slow_register(&rcu_fwd_cb_nodelay);
+
+	if (gpwrap_lag && cur_ops->set_gpwrap_lag) {
+		firsterr = rcu_gpwrap_lag_init();
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
+
+	torture_init_end();
 	return 0;
 
 unwind: