Merge tag 'rcu.6.4.april5.2023.3' of git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux

Pull RCU updates from Joel Fernandes:

- Updates and additions to MAINTAINERS files, with Boqun being added to
the RCU entry and Zqiang being added as an RCU reviewer.

I have also transitioned from reviewer to maintainer; however, Paul
will be taking over sending RCU pull-requests for the next merge
window.

- Resolution of hotplug warning in nohz code, achieved by fixing
cpu_is_hotpluggable() through interaction with the nohz subsystem.

Tick dependency modifications by Zqiang, focusing on fixing usage of
the TICK_DEP_BIT_RCU_EXP bitmask.

- Avoid needless calls to the rcu-lazy shrinker for CONFIG_RCU_LAZY=n
kernels, fixed by Zqiang.

- Improvements to rcu-tasks stall reporting by Neeraj.

- Initial renaming of k[v]free_rcu() to k[v]free_rcu_mightsleep() for
increased robustness, affecting several components like mac802154,
drbd, vmw_vmci, tracing, and more.

A report by Eric Dumazet showed that the API could be unknowingly
used in an atomic context, so we'd rather make sure they know what
they're asking for by being explicit:

https://lore.kernel.org/all/[e-mail]/

- Documentation updates, including corrections to spelling,
clarifications in comments, and improvements to the srcu_size_state
comments.

- Better srcu_struct cache locality for readers, by adjusting the size
of srcu_struct in support of SRCU usage by Christoph Hellwig.

- Teach lockdep to detect deadlocks between srcu_read_lock() vs
synchronize_srcu() contributed by Boqun.

Previously lockdep could not detect such deadlocks, now it can.

- Integration of rcutorture and rcu-related tools, targeted for v6.4
from Boqun's tree, featuring new SRCU deadlock scenarios, test_nmis
module parameter, and more

- Miscellaneous changes, various code cleanups and comment improvements

* tag 'rcu.6.4.april5.2023.3' of git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux: (71 commits)
checkpatch: Error out if deprecated RCU API used
mac802154: Rename kfree_rcu() to kvfree_rcu_mightsleep()
rcuscale: Rename kfree_rcu() to kfree_rcu_mightsleep()
ext4/super: Rename kfree_rcu() to kfree_rcu_mightsleep()
net/mlx5: Rename kfree_rcu() to kfree_rcu_mightsleep()
net/sysctl: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
lib/test_vmalloc.c: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
tracing: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
misc: vmw_vmci: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
drbd: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
rcu: Protect rcu_print_task_exp_stall() ->exp_tasks access
rcu: Avoid stack overflow due to __rcu_irq_enter_check_tick() being kprobe-ed
rcu-tasks: Report stalls during synchronize_srcu() in rcu_tasks_postscan()
rcu: Permit start_poll_synchronize_rcu_expedited() to be invoked early
rcu: Remove never-set needwake assignment from rcu_report_qs_rdp()
rcu: Register rcu-lazy shrinker only for CONFIG_RCU_LAZY=y kernels
rcu: Fix missing TICK_DEP_MASK_RCU_EXP dependency check
rcu: Fix set/clear TICK_DEP_BIT_RCU_EXP bitmask race
rcu/trace: use strscpy() to instead of strncpy()
tick/nohz: Fix cpu_is_hotpluggable() by checking with nohz subsystem
...

Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.rst

···
 
 Again, only one request in a given batch need actually carry out a
 grace-period operation, which means there must be an efficient way to
-identify which of many concurrent reqeusts will initiate the grace
+identify which of many concurrent requests will initiate the grace
 period, and that there be an efficient way for the remaining requests to
 wait for that grace period to complete. However, that is the topic of
 the next section.
···
 In earlier implementations, the task requesting the expedited grace
 period also drove it to completion. This straightforward approach had
 the disadvantage of needing to account for POSIX signals sent to user
-tasks, so more recent implemementations use the Linux kernel's
+tasks, so more recent implementations use the Linux kernel's
 workqueues (see Documentation/core-api/workqueue.rst).
 
 The requesting task still does counter snapshotting and funnel-lock
···
 initialized, which does not happen until some time after the scheduler
 spawns the first task. Given that there are parts of the kernel that
 really do want to execute grace periods during this mid-boot “dead
-zone”, expedited grace periods must do something else during thie time.
+zone”, expedited grace periods must do something else during this time.
 
 What they do is to fall back to the old practice of requiring that the
 requesting task drive the expedited grace period, as was the case before

Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst

···
 +-----------------------------------------------------------------------+
 
 The approach must be extended to handle one final case, that of waking a
-task blocked in ``synchronize_rcu()``. This task might be affinitied to
+task blocked in ``synchronize_rcu()``. This task might be affined to
 a CPU that is not yet aware that the grace period has ended, and thus
 might not yet be subject to the grace period's memory ordering.
 Therefore, there is an ``smp_mb()`` after the return from

Documentation/RCU/RTFP.txt

···
 In 2012, Josh Triplett received his Ph.D. with his dissertation
 covering RCU-protected resizable hash tables and the relationship
 between memory barriers and read-side traversal order:  If the updater
-is making changes in the opposite direction from the read-side traveral
+is making changes in the opposite direction from the read-side traversal
 order, the updater need only execute a memory-barrier instruction,
 but if in the same direction, the updater needs to wait for a grace
 period between the individual updates [JoshTriplettPhD].  Also in 2012,
···
 [Viewed September 5, 2005]"
 ,annotation={
 	First posting showing how RCU can be safely adapted for
-	preemptable RCU read side critical sections.
+	preemptible RCU read side critical sections.
 }
 }
 
···
 \url{https://lore.kernel.org/r/[e-mail]}
 [Viewed October 25, 2007]"
 ,annotation={
-	Final patch for preemptable RCU to -rt.  (Later patches were
+	Final patch for preemptible RCU to -rt.  (Later patches were
 	to mainline, eventually incorporated.)
 }
 }
···
 \url{https://lore.kernel.org/r/[e-mail]}
 [Viewed August 15, 2009]"
 ,annotation={
-	First posting of simple and fast preemptable RCU.
+	First posting of simple and fast preemptible RCU.
 }
 }
 
···
 	RCU-protected hash tables, barriers vs. read-side traversal order.
 	.
 	If the updater is making changes in the opposite direction from
-	the read-side traveral order, the updater need only execute a
+	the read-side traversal order, the updater need only execute a
 	memory-barrier instruction, but if in the same direction, the
 	updater needs to wait for a grace period between the individual
 	updates.

Documentation/RCU/UP.rst

···
 
 Quick Quiz #3:
 	Why can't synchronize_rcu() return immediately on UP systems running
-	preemptable RCU?
+	preemptible RCU?
 
 .. _answer_quick_quiz_up:
 
···
 
 Answer to Quick Quiz #3:
 	Why can't synchronize_rcu() return immediately on UP systems
-	running preemptable RCU?
+	running preemptible RCU?
 
 	Because some other task might have been preempted in the middle
 	of an RCU read-side critical section.  If synchronize_rcu()

Documentation/RCU/checklist.rst

···
 	can serve as rcu_read_lock_sched(), but is less readable and
 	prevents lockdep from detecting locking issues.
 
-	Please not that you *cannot* rely on code known to be built
+	Please note that you *cannot* rely on code known to be built
 	only in non-preemptible kernels.  Such code can and will break,
 	especially in kernels built with CONFIG_PREEMPT_COUNT=y.
 

Documentation/RCU/lockdep.rst

···
 	rcu_access_pointer(p):
 		Return the value of the pointer and omit all barriers,
 		but retain the compiler constraints that prevent duplicating
-		or coalescsing.  This is useful when testing the
+		or coalescing.  This is useful when testing the
 		value of the pointer itself, for example, against NULL.
 
 The rcu_dereference_check() check expression can be any boolean

Documentation/RCU/torture.rst

···
 rcutorture's module parameters.  For example, to test a change to RCU's
 CPU stall-warning code, use "--bootargs 'rcutorture.stall_cpu=30'".
 This will of course result in the scripting reporting a failure, namely
-the resuling RCU CPU stall warning.  As noted above, reducing memory may
+the resulting RCU CPU stall warning.  As noted above, reducing memory may
 require disabling rcutorture's callback-flooding tests::
 
 	kvm.sh --cpus 448 --configs '56*TREE04' --memory 128M \
···
 		tools/testing/selftests/rcutorture/res/2022.11.03-11.26.28-remote \
 		--duration 24h
 
-In this case, most of the kvm-again.sh parmeters may be supplied following
+In this case, most of the kvm-again.sh parameters may be supplied following
 the pathname of the old run-results directory.

Documentation/RCU/whatisRCU.rst

···
 If the occasional sleep is permitted, the single-argument form may
 be used, omitting the rcu_head structure from struct foo.
 
-	kfree_rcu(old_fp);
+	kfree_rcu_mightsleep(old_fp);
 
-This variant of kfree_rcu() almost never blocks, but might do so by
-invoking synchronize_rcu() in response to memory-allocation failure.
+This variant almost never blocks, but might do so by invoking
+synchronize_rcu() in response to memory-allocation failure.
 
 Again, see checklist.rst for additional rules governing the use of RCU.
 

MAINTAINERS

···
 M:	"Paul E. McKenney" <[e-mail]>
 M:	Frederic Weisbecker <[e-mail]> (kernel/rcu/tree_nocb.h)
 M:	Neeraj Upadhyay <[e-mail]> (kernel/rcu/tasks.h)
+M:	Joel Fernandes <[e-mail]>
 M:	Josh Triplett <[e-mail]>
+M:	Boqun Feng <[e-mail]>
 R:	Steven Rostedt <[e-mail]>
 R:	Mathieu Desnoyers <[e-mail]>
 R:	Lai Jiangshan <[e-mail]>
-R:	Joel Fernandes <[e-mail]>
+R:	Zqiang <[e-mail]>
 L:	[e-mail]
 S:	Supported
 W:	http://www.rdrop.com/users/paulmck/RCU/

arch/arm64/kvm/Kconfig

···
 	select KVM_MMIO
 	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
 	select KVM_XFER_TO_GUEST_WORK
-	select SRCU
 	select KVM_VFIO
 	select HAVE_KVM_EVENTFD
 	select HAVE_KVM_IRQFD

arch/mips/kvm/Kconfig

···
 	select HAVE_KVM_VCPU_ASYNC_IOCTL
 	select KVM_MMIO
 	select MMU_NOTIFIER
-	select SRCU
 	select INTERVAL_TREE
 	select KVM_GENERIC_HARDWARE_ENABLING
 	help

arch/powerpc/kvm/Kconfig

···
 	select PREEMPT_NOTIFIERS
 	select HAVE_KVM_EVENTFD
 	select HAVE_KVM_VCPU_ASYNC_IOCTL
-	select SRCU
 	select KVM_VFIO
 	select IRQ_BYPASS_MANAGER
 	select HAVE_KVM_IRQ_BYPASS

arch/riscv/kvm/Kconfig

···
 	select KVM_XFER_TO_GUEST_WORK
 	select HAVE_KVM_VCPU_ASYNC_IOCTL
 	select HAVE_KVM_EVENTFD
-	select SRCU
 	help
 	  Support hosting virtualized guest machines.
 

arch/s390/kvm/Kconfig

···
 	select HAVE_KVM_IRQ_ROUTING
 	select HAVE_KVM_INVALID_WAKEUPS
 	select HAVE_KVM_NO_POLL
-	select SRCU
 	select KVM_VFIO
 	select INTERVAL_TREE
 	select MMU_NOTIFIER

arch/x86/Kconfig

···
 	select RTC_LIB
 	select RTC_MC146818_LIB
 	select SPARSE_IRQ
-	select SRCU
 	select SYSCTL_EXCEPTION_TRACE
 	select THREAD_INFO_IN_TASK
 	select TRACE_IRQFLAGS_SUPPORT
···
 	depends on X86_64 && CPU_SUP_INTEL && X86_X2APIC
 	depends on CRYPTO=y
 	depends on CRYPTO_SHA256=y
-	select SRCU
 	select MMU_NOTIFIER
 	select NUMA_KEEP_MEMINFO if NUMA
 	select XARRAY_MULTI

arch/x86/kvm/Kconfig

···
 	select KVM_XFER_TO_GUEST_WORK
 	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
 	select KVM_VFIO
-	select SRCU
 	select INTERVAL_TREE
 	select HAVE_KVM_PM_NOTIFIER if PM
 	select KVM_GENERIC_HARDWARE_ENABLING

drivers/base/cpu.c

···
 bool cpu_is_hotpluggable(unsigned int cpu)
 {
 	struct device *dev = get_cpu_device(cpu);
-	return dev && container_of(dev, struct cpu, dev)->hotpluggable;
+	return dev && container_of(dev, struct cpu, dev)->hotpluggable
+		&& tick_nohz_cpu_hotpluggable(cpu);
 }
 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 

drivers/block/drbd/drbd_nl.c

···
 			drbd_send_sync_param(peer_device);
 	}
 
-	kvfree_rcu(old_disk_conf);
+	kvfree_rcu_mightsleep(old_disk_conf);
 	kfree(old_plan);
 	mod_timer(&device->request_timer, jiffies + HZ);
 	goto success;
···
 
 	mutex_unlock(&connection->resource->conf_update);
 	mutex_unlock(&connection->data.mutex);
-	kvfree_rcu(old_net_conf);
+	kvfree_rcu_mightsleep(old_net_conf);
 
 	if (connection->cstate >= C_WF_REPORT_PARAMS) {
 		struct drbd_peer_device *peer_device;
···
 		new_disk_conf->disk_size = (sector_t)rs.resize_size;
 		rcu_assign_pointer(device->ldev->disk_conf, new_disk_conf);
 		mutex_unlock(&device->resource->conf_update);
-		kvfree_rcu(old_disk_conf);
+		kvfree_rcu_mightsleep(old_disk_conf);
 		new_disk_conf = NULL;
 	}
 

drivers/block/drbd/drbd_receiver.c

···
 		drbd_info(connection, "peer data-integrity-alg: %s\n",
 			  integrity_alg[0] ? integrity_alg : "(none)");
 
-	kvfree_rcu(old_net_conf);
+	kvfree_rcu_mightsleep(old_net_conf);
 	return 0;
 
 disconnect_rcu_unlock:
···
 
 			rcu_assign_pointer(device->ldev->disk_conf, new_disk_conf);
 			mutex_unlock(&connection->resource->conf_update);
-			kvfree_rcu(old_disk_conf);
+			kvfree_rcu_mightsleep(old_disk_conf);
 
 			drbd_info(device, "Peer sets u_size to %lu sectors (old: %lu)\n",
 				 (unsigned long)p_usize, (unsigned long)my_usize);

drivers/block/drbd/drbd_state.c

···
 		conn_free_crypto(connection);
 		mutex_unlock(&connection->resource->conf_update);
 
-		kvfree_rcu(old_conf);
+		kvfree_rcu_mightsleep(old_conf);
 	}
 
 	if (ns_max.susp_fen) {

drivers/misc/vmw_vmci/vmci_context.c

···
 	spin_unlock(&context->lock);
 
 	if (notifier)
-		kvfree_rcu(notifier);
+		kvfree_rcu_mightsleep(notifier);
 
 	vmci_ctx_put(context);
 

drivers/misc/vmw_vmci/vmci_event.c

···
 	if (!s)
 		return VMCI_ERROR_NOT_FOUND;
 
-	kvfree_rcu(s);
+	kvfree_rcu_mightsleep(s);
 
 	return VMCI_SUCCESS;
 }

drivers/net/ethernet/mellanox/mlx5/core/en/tc/int_port.c

···
 		mlx5_del_flow_rules(int_port->rx_rule);
 	mapping_remove(ctx, int_port->mapping);
 	mlx5e_int_port_metadata_free(priv, int_port->match_metadata);
-	kfree_rcu(int_port);
+	kfree_rcu_mightsleep(int_port);
 	priv->num_ports--;
 }
 

drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c

···
 
 	mlx5e_macsec_cleanup_sa(macsec, tx_sa, true);
 	mlx5_destroy_encryption_key(macsec->mdev, tx_sa->enc_key_id);
-	kfree_rcu(tx_sa);
+	kfree_rcu_mightsleep(tx_sa);
 	macsec_device->tx_sa[assoc_num] = NULL;
 
 out:
···
 	xa_erase(&macsec->sc_xarray, rx_sc->sc_xarray_element->fs_id);
 	metadata_dst_free(rx_sc->md_dst);
 	kfree(rx_sc->sc_xarray_element);
-	kfree_rcu(rx_sc);
+	kfree_rcu_mightsleep(rx_sc);
 }
 
 static int mlx5e_macsec_del_rxsc(struct macsec_context *ctx)

fs/ext4/super.c

···
 			qname = rcu_replace_pointer(sbi->s_qf_names[i], qname,
 						lockdep_is_held(&sb->s_umount));
 			if (qname)
-				kfree_rcu(qname);
+				kfree_rcu_mightsleep(qname);
 		}
 	}
 

include/linux/lockdep.h

···
 	unsigned int read:2;        /* see lock_acquire() comment */
 	unsigned int check:1;       /* see lock_acquire() comment */
 	unsigned int hardirqs_off:1;
-	unsigned int references:12;					/* 32 bits */
+	unsigned int sync:1;
+	unsigned int references:11;					/* 32 bits */
 	unsigned int pin_count;
 };
 
···
 			 struct lockdep_map *nest_lock, unsigned long ip);
 
 extern void lock_release(struct lockdep_map *lock, unsigned long ip);
+
+extern void lock_sync(struct lockdep_map *lock, unsigned int subclass,
+		      int read, int check, struct lockdep_map *nest_lock,
+		      unsigned long ip);
 
 /* lock_is_held_type() returns */
 #define LOCK_STATE_UNKNOWN	-1
···
 #define lock_map_acquire_read(l)		lock_acquire_shared_recursive(l, 0, 0, NULL, _THIS_IP_)
 #define lock_map_acquire_tryread(l)		lock_acquire_shared_recursive(l, 0, 1, NULL, _THIS_IP_)
 #define lock_map_release(l)			lock_release(l, _THIS_IP_)
+#define lock_map_sync(l)			lock_sync(l, 0, 0, 1, NULL, _THIS_IP_)
 
 #ifdef CONFIG_PROVE_LOCKING
 # define might_lock(lock)						\

include/linux/notifier.h

···
 
 struct srcu_notifier_head {
 	struct mutex mutex;
+#ifdef CONFIG_TREE_SRCU
+	struct srcu_usage srcuu;
+#endif
 	struct srcu_struct srcu;
 	struct notifier_block __rcu *head;
 };
···
 	{							\
 		.mutex = __MUTEX_INITIALIZER(name.mutex),	\
 		.head = NULL,					\
-		.srcu = __SRCU_STRUCT_INIT(name.srcu, pcpu),	\
+		.srcu = __SRCU_STRUCT_INIT(name.srcu, name.srcuu, pcpu), \
 	}
 
 #define ATOMIC_NOTIFIER_HEAD(name)				\

include/linux/srcu.h

···
 	return lock_is_held(&ssp->dep_map);
 }
 
+/*
+ * Annotations provide deadlock detection for SRCU.
+ *
+ * Similar to other lockdep annotations, except there is an additional
+ * srcu_lock_sync(), which is basically an empty *write*-side critical section,
+ * see lock_sync() for more information.
+ */
+
+/* Annotates a srcu_read_lock() */
+static inline void srcu_lock_acquire(struct lockdep_map *map)
+{
+	lock_map_acquire_read(map);
+}
+
+/* Annotates a srcu_read_lock() */
+static inline void srcu_lock_release(struct lockdep_map *map)
+{
+	lock_map_release(map);
+}
+
+/* Annotates a synchronize_srcu() */
+static inline void srcu_lock_sync(struct lockdep_map *map)
+{
+	lock_map_sync(map);
+}
+
 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
 {
 	return 1;
 }
+
+#define srcu_lock_acquire(m) do { } while (0)
+#define srcu_lock_release(m) do { } while (0)
+#define srcu_lock_sync(m) do { } while (0)
 
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
···
 
 	srcu_check_nmi_safety(ssp, false);
 	retval = __srcu_read_lock(ssp);
-	rcu_lock_acquire(&(ssp)->dep_map);
+	srcu_lock_acquire(&(ssp)->dep_map);
 	return retval;
 }
 
···
 {
 	WARN_ON_ONCE(idx & ~0x1);
 	srcu_check_nmi_safety(ssp, false);
-	rcu_lock_release(&(ssp)->dep_map);
+	srcu_lock_release(&(ssp)->dep_map);
 	__srcu_read_unlock(ssp, idx);
 }
 

include/linux/srcutiny.h

···
 
 void srcu_drive_gp(struct work_struct *wp);
 
-#define __SRCU_STRUCT_INIT(name, __ignored)				\
+#define __SRCU_STRUCT_INIT(name, __ignored, ___ignored)			\
 {									\
 	.srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq),	\
 	.srcu_cb_tail = &name.srcu_cb_head,				\
···
  * Tree SRCU, which needs some per-CPU data.
  */
 #define DEFINE_SRCU(name) \
-	struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)
+	struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)
 #define DEFINE_STATIC_SRCU(name) \
-	static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)
+	static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)
 
 void synchronize_srcu(struct srcu_struct *ssp);
 

include/linux/srcutree.h

···
 };
 
 /*
- * Per-SRCU-domain structure, similar in function to rcu_state.
+ * Per-SRCU-domain structure, update-side data linked from srcu_struct.
  */
-struct srcu_struct {
+struct srcu_usage {
 	struct srcu_node *node;			/* Combining tree. */
 	struct srcu_node *level[RCU_NUM_LVLS + 1];
 						/* First node at each level. */
···
 	struct mutex srcu_cb_mutex;		/* Serialize CB preparation. */
 	spinlock_t __private lock;		/* Protect counters and size state. */
 	struct mutex srcu_gp_mutex;		/* Serialize GP work. */
-	unsigned int srcu_idx;			/* Current rdr array element. */
 	unsigned long srcu_gp_seq;		/* Grace-period seq #. */
 	unsigned long srcu_gp_seq_needed;	/* Latest gp_seq needed. */
 	unsigned long srcu_gp_seq_needed_exp;	/* Furthest future exp GP. */
···
 	unsigned long srcu_size_jiffies;	/* Current contention-measurement interval. */
 	unsigned long srcu_n_lock_retries;	/* Contention events in current interval. */
 	unsigned long srcu_n_exp_nodelay;	/* # expedited no-delays in current GP phase. */
-	struct srcu_data __percpu *sda;		/* Per-CPU srcu_data array. */
 	bool sda_is_static;			/* May ->sda be passed to free_percpu()? */
 	unsigned long srcu_barrier_seq;		/* srcu_barrier seq #. */
 	struct mutex srcu_barrier_mutex;	/* Serialize barrier ops. */
···
 	unsigned long reschedule_jiffies;
 	unsigned long reschedule_count;
 	struct delayed_work work;
-	struct lockdep_map dep_map;
+	struct srcu_struct *srcu_ssp;
 };
 
-/* Values for size state variable (->srcu_size_state). */
-#define SRCU_SIZE_SMALL		0
-#define SRCU_SIZE_ALLOC		1
-#define SRCU_SIZE_WAIT_BARRIER	2
-#define SRCU_SIZE_WAIT_CALL	3
-#define SRCU_SIZE_WAIT_CBS1	4
-#define SRCU_SIZE_WAIT_CBS2	5
-#define SRCU_SIZE_WAIT_CBS3	6
-#define SRCU_SIZE_WAIT_CBS4	7
-#define SRCU_SIZE_BIG		8
+/*
+ * Per-SRCU-domain structure, similar in function to rcu_state.
+ */
+struct srcu_struct {
+	unsigned int srcu_idx;			/* Current rdr array element. */
+	struct srcu_data __percpu *sda;		/* Per-CPU srcu_data array. */
+	struct lockdep_map dep_map;
+	struct srcu_usage *srcu_sup;		/* Update-side data. */
+};
+
+// Values for size state variable (->srcu_size_state).  Once the state
+// has been set to SRCU_SIZE_ALLOC, the grace-period code advances through
+// this state machine one step per grace period until the SRCU_SIZE_BIG state
+// is reached.  Otherwise, the state machine remains in the SRCU_SIZE_SMALL
+// state indefinitely.
+#define SRCU_SIZE_SMALL		0	// No srcu_node combining tree, ->node == NULL
+#define SRCU_SIZE_ALLOC		1	// An srcu_node tree is being allocated, initialized,
+					//  and then referenced by ->node.  It will not be used.
+#define SRCU_SIZE_WAIT_BARRIER	2	// The srcu_node tree starts being used by everything
+					//  except call_srcu(), especially by srcu_barrier().
+					//  By the end of this state, all CPUs and threads
+					//  are aware of this tree's existence.
+#define SRCU_SIZE_WAIT_CALL	3	// The srcu_node tree starts being used by call_srcu().
+					//  By the end of this state, all of the call_srcu()
+					//  invocations that were running on a non-boot CPU
+					//  and using the boot CPU's callback queue will have
+					//  completed.
+#define SRCU_SIZE_WAIT_CBS1	4	// Don't trust the ->srcu_have_cbs[] grace-period
+#define SRCU_SIZE_WAIT_CBS2	5	//  sequence elements or the ->srcu_data_have_cbs[]
+#define SRCU_SIZE_WAIT_CBS3	6	//  CPU-bitmask elements until all four elements of
+#define SRCU_SIZE_WAIT_CBS4	7	//  each array have been initialized.
+#define SRCU_SIZE_BIG		8	// The srcu_node combining tree is fully initialized
+					//  and all aspects of it are being put to use.
 
 /* Values for state variable (bottom bits of ->srcu_gp_seq). */
 #define SRCU_STATE_IDLE		0
 #define SRCU_STATE_SCAN1	1
 #define SRCU_STATE_SCAN2	2
 
-#define __SRCU_STRUCT_INIT(name, pcpu_name)				\
-{									\
-	.sda = &pcpu_name,						\
-	.lock = __SPIN_LOCK_UNLOCKED(name.lock),			\
-	.srcu_gp_seq_needed = -1UL,					\
-	.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),		\
-	__SRCU_DEP_MAP_INIT(name)					\
+#define __SRCU_USAGE_INIT(name)									\
+{												\
+	.lock = __SPIN_LOCK_UNLOCKED(name.lock),						\
+	.srcu_gp_seq_needed = -1UL,								\
+	.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),					\
+}
+
+#define __SRCU_STRUCT_INIT_COMMON(name, usage_name)						\
+	.srcu_sup = &usage_name,								\
+	__SRCU_DEP_MAP_INIT(name)
+
+#define __SRCU_STRUCT_INIT_MODULE(name, usage_name)						\
+{												\
+	__SRCU_STRUCT_INIT_COMMON(name, usage_name)						\
+}
+
+#define __SRCU_STRUCT_INIT(name, usage_name, pcpu_name)						\
+{												\
+	.sda = &pcpu_name,									\
+	__SRCU_STRUCT_INIT_COMMON(name, usage_name)						\
 }
 
 /*
···
  * See include/linux/percpu-defs.h for the rules on per-CPU variables.
  */
 #ifdef MODULE
-# define __DEFINE_SRCU(name, is_static)					\
-	is_static struct srcu_struct name;				\
-	extern struct srcu_struct * const __srcu_struct_##name;		\
-	struct srcu_struct * const __srcu_struct_##name			\
+# define __DEFINE_SRCU(name, is_static)								\
+	static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage);	\
+	is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name, name##_srcu_usage);	\
+	extern struct srcu_struct * const __srcu_struct_##name;					\
+	struct srcu_struct * const __srcu_struct_##name						\
 		__section("___srcu_struct_ptrs") = &name
 #else
-# define __DEFINE_SRCU(name, is_static)					\
-	static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);	\
-	is_static struct srcu_struct name =				\
-		__SRCU_STRUCT_INIT(name, name##_srcu_data)
+# define __DEFINE_SRCU(name, is_static)								\
+	static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);				\
+	static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage);	\
+	is_static struct srcu_struct name =							\
+		__SRCU_STRUCT_INIT(name, name##_srcu_usage, name##_srcu_data)
 #endif
 #define DEFINE_SRCU(name)		__DEFINE_SRCU(name, /* not static */)
 #define DEFINE_STATIC_SRCU(name)	__DEFINE_SRCU(name, static)

include/linux/tick.h

···
 				     enum tick_dep_bits bit);
 extern void tick_nohz_dep_clear_signal(struct signal_struct *signal,
 				       enum tick_dep_bits bit);
+extern bool tick_nohz_cpu_hotpluggable(unsigned int cpu);
 
 /*
  * The below are tick_nohz_[set,clear]_dep() wrappers that optimize off-cases
···
 
 static inline void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) { }
 static inline void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) { }
+static inline bool tick_nohz_cpu_hotpluggable(unsigned int cpu) { return true; }
 
 static inline void tick_dep_set(enum tick_dep_bits bit) { }
 static inline void tick_dep_clear(enum tick_dep_bits bit) { }

include/trace/events/rcu.h

···
 	),
 
 	TP_fast_assign(
-		strncpy(__entry->rcutorturename, rcutorturename,
-			RCUTORTURENAME_LEN);
-		__entry->rcutorturename[RCUTORTURENAME_LEN - 1] = 0;
+		strscpy(__entry->rcutorturename, rcutorturename, RCUTORTURENAME_LEN);
 		__entry->rhp = rhp;
 		__entry->secs = secs;
 		__entry->c_old = c_old;

include/trace/events/timer.h

···
 		tick_dep_name(PERF_EVENTS)		\
 		tick_dep_name(SCHED)			\
 		tick_dep_name(CLOCK_UNSTABLE)		\
-		tick_dep_name_end(RCU)
+		tick_dep_name(RCU)			\
+		tick_dep_name_end(RCU_EXP)
 
 #undef tick_dep_name
 #undef tick_dep_mask_name

kernel/locking/lockdep.c

···
 	struct lock_class *source = hlock_class(src);
 	struct lock_class *target = hlock_class(tgt);
 	struct lock_class *parent = prt->class;
+	int src_read = src->read;
+	int tgt_read = tgt->read;
 
 	/*
 	 * A direct locking problem where unsafe_class lock is taken
···
 	printk(" Possible unsafe locking scenario:\n\n");
 	printk("       CPU0                    CPU1\n");
 	printk("       ----                    ----\n");
-	printk("  lock(");
+	if (tgt_read != 0)
+		printk("  rlock(");
+	else
+		printk("  lock(");
 	__print_lock_name(target);
 	printk(KERN_CONT ");\n");
 	printk("                               lock(");
···
 	printk("                               lock(");
 	__print_lock_name(target);
 	printk(KERN_CONT ");\n");
-	printk("  lock(");
+	if (src_read != 0)
+		printk("  rlock(");
+	else if (src->sync)
+		printk("  sync(");
+	else
+		printk("  lock(");
 	__print_lock_name(source);
 	printk(KERN_CONT ");\n");
 	printk("\n *** DEADLOCK ***\n\n");
···
 					return 0;
 		}
 	}
-	if (!hlock->hardirqs_off) {
+
+	/*
+	 * For lock_sync(), don't mark the ENABLED usage, since lock_sync()
+	 * creates no critical section and no extra dependency can be introduced
+	 * by interrupts
+	 */
+	if (!hlock->hardirqs_off && !hlock->sync) {
 		if (hlock->read) {
 			if (!mark_lock(curr, hlock,
 					LOCK_ENABLED_HARDIRQ_READ))
···
 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 			  int trylock, int read, int check, int hardirqs_off,
 			  struct lockdep_map *nest_lock, unsigned long ip,
-			  int references, int pin_count)
+			  int references, int pin_count, int sync)
 {
 	struct task_struct *curr = current;
 	struct lock_class *class = NULL;
···
 
 	class_idx = class - lock_classes;
 
-	if (depth) { /* we're holding locks */
+	if (depth && !sync) {
+		/* we're holding locks and the new held lock is not a sync */
 		hlock = curr->held_locks + depth - 1;
 		if (hlock->class_idx == class_idx && nest_lock) {
 			if (!references)
···
 	hlock->trylock = trylock;
 	hlock->read = read;
 	hlock->check = check;
+	hlock->sync = !!sync;
 	hlock->hardirqs_off = !!hardirqs_off;
 	hlock->references = references;
 #ifdef CONFIG_LOCK_STAT
···
 
 	if (!validate_chain(curr, hlock, chain_head, chain_key))
 		return 0;
+
+	/* For lock_sync(), we are done here since no actual critical section */
+	if (hlock->sync)
+		return 1;
 
 	curr->curr_chain_key = chain_key;
 	curr->lockdep_depth++;
···
 				    hlock->read, hlock->check,
 				    hlock->hardirqs_off,
 				    hlock->nest_lock, hlock->acquire_ip,
-				    hlock->references, hlock->pin_count)) {
+				    hlock->references, hlock->pin_count, 0)) {
 		case 0:
 			return 1;
 		case 1:
···
 
 	lockdep_recursion_inc();
 	__lock_acquire(lock, subclass, trylock, read, check,
-		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
+		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 0);
 	lockdep_recursion_finish();
 	raw_local_irq_restore(flags);
 }
···
 	raw_local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(lock_release);
+
+/*
+ * lock_sync() - A special annotation for synchronize_{s,}rcu()-like API.
+ *
+ * No actual critical section is created by the APIs annotated with this: these
+ * APIs are used to wait for one or multiple critical sections (on other CPUs
+ * or threads), and it means that calling these APIs inside these critical
+ * sections is potential deadlock.
+ */
+void lock_sync(struct lockdep_map *lock, unsigned subclass, int read,
+	       int check, struct lockdep_map *nest_lock, unsigned long ip)
+{
+	unsigned long flags;
+
+	if (unlikely(!lockdep_enabled()))
+		return;
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+
+	lockdep_recursion_inc();
+	__lock_acquire(lock, subclass, 0, read, check,
+		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 1);
+	check_chain_key(current);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_sync);
 
 noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
 {

kernel/locking/test-ww_mutex.c

···
 	if (ret)
 		return ret;
 
-	ret = stress(4095, hweight32(STRESS_ALL)*ncpus, STRESS_ALL);
+	ret = stress(2047, hweight32(STRESS_ALL)*ncpus, STRESS_ALL);
 	if (ret)
 		return ret;
 

kernel/rcu/Kconfig

···
 
 	  Say N if you are unsure.
 
-config SRCU
-	def_bool y
-
 config TINY_SRCU
 	bool
 	default y if TINY_RCU

kernel/rcu/rcu.h

···
 
 /*
  * Grace-period counter management.
+ *
+ * The two least significant bits contain the control flags.
+ * The most significant bits contain the grace-period sequence counter.
+ *
+ * When both control flags are zero, no grace period is in progress.
+ * When either bit is non-zero, a grace period has started and is in
+ * progress. When the grace period completes, the control flags are reset
+ * to 0 and the grace-period sequence counter is incremented.
+ *
+ * However some specific RCU usages make use of custom values.
+ *
+ * SRCU special control values:
+ *
+ *	SRCU_SNP_INIT_SEQ	:	Invalid/init value set when SRCU node
+ *					is initialized.
+ *
+ *	SRCU_STATE_IDLE		:	No SRCU gp is in progress
+ *
+ *	SRCU_STATE_SCAN1	:	State set by rcu_seq_start(). Indicates
+ *					we are scanning the readers on the slot
+ *					defined as inactive (there might well
+ *					be pending readers that will use that
+ *					index, but their number is bounded).
+ *
+ *	SRCU_STATE_SCAN2	:	State set manually via rcu_seq_set_state()
+ *					Indicates we are flipping the readers
+ *					index and then scanning the readers on the
+ *					slot newly designated as inactive (again,
+ *					the number of pending readers that will use
+ *					this inactive index is bounded).
+ *
+ * RCU polled GP special control value:
+ *
+ *	RCU_GET_STATE_COMPLETED :	State value indicating an already-completed
+ *					polled GP has completed.  This value covers
+ *					both the state and the counter of the
+ *					grace-period sequence number.
  */
 
 #define RCU_SEQ_CTR_SHIFT	2
···
  * specified state structure (for SRCU) or the only rcu_state structure
  * (for RCU).
  */
-#define srcu_for_each_node_breadth_first(sp, rnp) \
+#define _rcu_for_each_node_breadth_first(sp, rnp) \
 	for ((rnp) = &(sp)->node[0]; \
 	     (rnp) < &(sp)->node[rcu_num_nodes]; (rnp)++)
 #define rcu_for_each_node_breadth_first(rnp) \
-	srcu_for_each_node_breadth_first(&rcu_state, rnp)
+	_rcu_for_each_node_breadth_first(&rcu_state, rnp)
+#define srcu_for_each_node_breadth_first(ssp, rnp) \
+	_rcu_for_each_node_breadth_first(ssp->srcu_sup, rnp)
 
 /*
  * Scan the leaves of the rcu_node hierarchy for the rcu_state structure.

kernel/rcu/rcuscale.c

···
 static int
 rcu_scale_shutdown(void *arg)
 {
-	wait_event(shutdown_wq,
-		   atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters);
+	wait_event_idle(shutdown_wq, atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters);
 	smp_mb(); /* Wake before output. */
 	rcu_scale_cleanup();
 	kernel_power_off();
···
 			// is tested.
 			if ((kfree_rcu_test_single && !kfree_rcu_test_double) ||
 					(kfree_rcu_test_both && torture_random(&tr) & 0x800))
-				kfree_rcu(alloc_ptr);
+				kfree_rcu_mightsleep(alloc_ptr);
 			else
 				kfree_rcu(alloc_ptr, rh);
 		}
···
 static int
 kfree_scale_shutdown(void *arg)
 {
-	wait_event(shutdown_wq,
-		   atomic_read(&n_kfree_scale_thread_ended) >= kfree_nrealthreads);
+	wait_event_idle(shutdown_wq,
+			atomic_read(&n_kfree_scale_thread_ended) >= kfree_nrealthreads);
 
 	smp_mb(); /* Wake before output. */
 

kernel/rcu/rcutorture.c

···
 torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
 torture_param(int, test_boost_duration, 4, "Duration of each boost test, seconds.");
 torture_param(int, test_boost_interval, 7, "Interval between boost tests, seconds.");
+torture_param(int, test_nmis, 0, "End-test NMI tests, 0 to disable.");
 torture_param(bool, test_no_idle_hz, true, "Test support for tickless idle CPUs");
+torture_param(int, test_srcu_lockdep, 0, "Test specified SRCU deadlock scenario.");
 torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
 
 static char *torture_type = "rcu";
···
 static atomic_t n_rcu_torture_error;
 static long n_rcu_torture_barrier_error;
 static long n_rcu_torture_boost_ktrerror;
-static long n_rcu_torture_boost_rterror;
 static long n_rcu_torture_boost_failure;
 static long n_rcu_torture_boosts;
 static atomic_long_t n_rcu_torture_timers;
···
 		atomic_read(&n_rcu_torture_alloc),
 		atomic_read(&n_rcu_torture_alloc_fail),
 		atomic_read(&n_rcu_torture_free));
-	pr_cont("rtmbe: %d rtmbkf: %d/%d rtbe: %ld rtbke: %ld rtbre: %ld ",
+	pr_cont("rtmbe: %d rtmbkf: %d/%d rtbe: %ld rtbke: %ld ",
 		atomic_read(&n_rcu_torture_mberror),
 		atomic_read(&n_rcu_torture_mbchk_fail), atomic_read(&n_rcu_torture_mbchk_tries),
 		n_rcu_torture_barrier_error,
-		n_rcu_torture_boost_ktrerror,
-		n_rcu_torture_boost_rterror);
+		n_rcu_torture_boost_ktrerror);
 	pr_cont("rtbf: %ld rtb: %ld nt: %ld ",
 		n_rcu_torture_boost_failure,
 		n_rcu_torture_boosts,
···
 	if (atomic_read(&n_rcu_torture_mberror) ||
 	    atomic_read(&n_rcu_torture_mbchk_fail) ||
 	    n_rcu_torture_barrier_error || n_rcu_torture_boost_ktrerror ||
-	    n_rcu_torture_boost_rterror || n_rcu_torture_boost_failure ||
-	    i > 1) {
+	    n_rcu_torture_boost_failure || i > 1) {
 		pr_cont("%s", "!!! ");
 		atomic_inc(&n_rcu_torture_error);
 		WARN_ON_ONCE(atomic_read(&n_rcu_torture_mberror));
 		WARN_ON_ONCE(atomic_read(&n_rcu_torture_mbchk_fail));
 		WARN_ON_ONCE(n_rcu_torture_barrier_error);  // rcu_barrier()
 		WARN_ON_ONCE(n_rcu_torture_boost_ktrerror); // no boost kthread
-		WARN_ON_ONCE(n_rcu_torture_boost_rterror); // can't set RT prio
 		WARN_ON_ONCE(n_rcu_torture_boost_failure); // boost failed (TIMER_SOFTIRQ RT prio?)
 		WARN_ON_ONCE(i > 1); // Too-short grace period
 	}
···
 		 "n_barrier_cbs=%d "
 		 "onoff_interval=%d onoff_holdoff=%d "
 		 "read_exit_delay=%d read_exit_burst=%d "
-		 "nocbs_nthreads=%d nocbs_toggle=%d\n",
+		 "nocbs_nthreads=%d nocbs_toggle=%d "
+		 "test_nmis=%d\n",
 		 torture_type, tag, nrealreaders, nfakewriters,
 		 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 		 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
···
 		 n_barrier_cbs,
 		 onoff_interval, onoff_holdoff,
 		 read_exit_delay, read_exit_burst,
-		 nocbs_nthreads, nocbs_toggle);
+		 nocbs_nthreads, nocbs_toggle,
+		 test_nmis);
 }
 
 static int rcutorture_booster_cleanup(unsigned int cpu)
···
 	torture_stop_kthread(rcutorture_read_exit, read_exit_task);
 }
 
+static void rcutorture_test_nmis(int n)
+{
+#if IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)
+	int cpu;
+	int dumpcpu;
+	int i;
+
+	for (i = 0; i < n; i++) {
+		preempt_disable();
+		cpu = smp_processor_id();
+		dumpcpu = cpu + 1;
+		if (dumpcpu >= nr_cpu_ids)
+			dumpcpu = 0;
+		pr_alert("%s: CPU %d invoking dump_cpu_task(%d)\n", __func__, cpu, dumpcpu);
+		dump_cpu_task(dumpcpu);
+		preempt_enable();
+		schedule_timeout_uninterruptible(15 * HZ);
+	}
+#else // #if IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)
+	WARN_ONCE(n, "Non-zero rcutorture.test_nmis=%d permitted only when rcutorture is built in.\n", test_nmis);
+#endif // #else // #if IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)
+}
+
 static enum cpuhp_state rcutor_hp;
 
 static void
···
 		rcu_gp_slow_unregister(NULL);
 		return;
 	}
+
+	rcutorture_test_nmis(test_nmis);
 
 	if (cur_ops->gp_kthread_dbg)
 		cur_ops->gp_kthread_dbg();
···
 		cur_ops->sync();
 }
 
+static DEFINE_MUTEX(mut0);
+static DEFINE_MUTEX(mut1);
+static DEFINE_MUTEX(mut2);
+static DEFINE_MUTEX(mut3);
+static DEFINE_MUTEX(mut4);
+static DEFINE_MUTEX(mut5);
+static DEFINE_MUTEX(mut6);
+static DEFINE_MUTEX(mut7);
+static DEFINE_MUTEX(mut8);
+static DEFINE_MUTEX(mut9);
+
+static DECLARE_RWSEM(rwsem0);
+static DECLARE_RWSEM(rwsem1);
+static DECLARE_RWSEM(rwsem2);
+static DECLARE_RWSEM(rwsem3);
+static DECLARE_RWSEM(rwsem4);
+static DECLARE_RWSEM(rwsem5);
+static DECLARE_RWSEM(rwsem6);
+static DECLARE_RWSEM(rwsem7);
+static DECLARE_RWSEM(rwsem8);
+static DECLARE_RWSEM(rwsem9);
+
+DEFINE_STATIC_SRCU(srcu0);
+DEFINE_STATIC_SRCU(srcu1);
+DEFINE_STATIC_SRCU(srcu2);
+DEFINE_STATIC_SRCU(srcu3);
+DEFINE_STATIC_SRCU(srcu4);
+DEFINE_STATIC_SRCU(srcu5);
+DEFINE_STATIC_SRCU(srcu6);
+DEFINE_STATIC_SRCU(srcu7);
+DEFINE_STATIC_SRCU(srcu8);
+DEFINE_STATIC_SRCU(srcu9);
+
+static int srcu_lockdep_next(const char *f, const char *fl, const char *fs, const char *fu, int i,
+			     int cyclelen, int deadlock)
+{
+	int j = i + 1;
+
+	if (j >= cyclelen)
+		j = deadlock ? 0 : -1;
+	if (j >= 0)
+		pr_info("%s: %s(%d), %s(%d), %s(%d)\n", f, fl, i, fs, j, fu, i);
+	else
+		pr_info("%s: %s(%d), %s(%d)\n", f, fl, i, fu, i);
+	return j;
+}
+
+// Test lockdep on SRCU-based deadlock scenarios.
+static void rcu_torture_init_srcu_lockdep(void)
+{
+	int cyclelen;
+	int deadlock;
+	bool err = false;
+	int i;
+	int j;
+	int idx;
+	struct mutex *muts[] = { &mut0, &mut1, &mut2, &mut3, &mut4,
+				 &mut5, &mut6, &mut7, &mut8, &mut9 };
+	struct rw_semaphore *rwsems[] = { &rwsem0, &rwsem1, &rwsem2, &rwsem3, &rwsem4,
+					  &rwsem5, &rwsem6, &rwsem7, &rwsem8, &rwsem9 };
+	struct srcu_struct *srcus[] = { &srcu0, &srcu1, &srcu2, &srcu3, &srcu4,
+					&srcu5, &srcu6, &srcu7, &srcu8, &srcu9 };
+	int testtype;
+
+	if (!test_srcu_lockdep)
+		return;
+
+	deadlock = test_srcu_lockdep / 1000;
+	testtype = (test_srcu_lockdep / 10) % 100;
+	cyclelen = test_srcu_lockdep % 10;
+	WARN_ON_ONCE(ARRAY_SIZE(muts) != ARRAY_SIZE(srcus));
+	if (WARN_ONCE(deadlock != !!deadlock,
+		      "%s: test_srcu_lockdep=%d and deadlock digit %d must be zero or one.\n",
+		      __func__, test_srcu_lockdep, deadlock))
+		err = true;
+	if (WARN_ONCE(cyclelen <= 0,
+		      "%s: test_srcu_lockdep=%d and cycle-length digit %d must be greater than zero.\n",
+		      __func__, test_srcu_lockdep, cyclelen))
+		err = true;
+	if (err)
+		goto err_out;
+
+	if (testtype == 0) {
+		pr_info("%s: test_srcu_lockdep = %05d: SRCU %d-way %sdeadlock.\n",
+			__func__, test_srcu_lockdep, cyclelen, deadlock ? "" : "non-");
+		if (deadlock && cyclelen == 1)
+			pr_info("%s: Expect hang.\n", __func__);
+		for (i = 0; i < cyclelen; i++) {
+			j = srcu_lockdep_next(__func__, "srcu_read_lock", "synchronize_srcu",
+					      "srcu_read_unlock", i, cyclelen, deadlock);
+			idx = srcu_read_lock(srcus[i]);
+			if (j >= 0)
+				synchronize_srcu(srcus[j]);
+			srcu_read_unlock(srcus[i], idx);
+		}
+		return;
+	}
+
+	if (testtype == 1) {
+		pr_info("%s: test_srcu_lockdep = %05d: SRCU/mutex %d-way %sdeadlock.\n",
+			__func__, test_srcu_lockdep, cyclelen, deadlock ? "" : "non-");
+		for (i = 0; i < cyclelen; i++) {
+			pr_info("%s: srcu_read_lock(%d), mutex_lock(%d), mutex_unlock(%d), srcu_read_unlock(%d)\n",
+				__func__, i, i, i, i);
+			idx = srcu_read_lock(srcus[i]);
+			mutex_lock(muts[i]);
+			mutex_unlock(muts[i]);
+			srcu_read_unlock(srcus[i], idx);
+
+			j = srcu_lockdep_next(__func__, "mutex_lock", "synchronize_srcu",
+					      "mutex_unlock", i, cyclelen, deadlock);
+			mutex_lock(muts[i]);
+			if (j >= 0)
+				synchronize_srcu(srcus[j]);
+			mutex_unlock(muts[i]);
+		}
+		return;
+	}
+
+	if (testtype == 2) {
+		pr_info("%s: test_srcu_lockdep = %05d: SRCU/rwsem %d-way %sdeadlock.\n",
+			__func__, test_srcu_lockdep, cyclelen, deadlock ? "" : "non-");
+		for (i = 0; i < cyclelen; i++) {
+			pr_info("%s: srcu_read_lock(%d), down_read(%d), up_read(%d), srcu_read_unlock(%d)\n",
+				__func__, i, i, i, i);
+			idx = srcu_read_lock(srcus[i]);
+			down_read(rwsems[i]);
+			up_read(rwsems[i]);
+			srcu_read_unlock(srcus[i], idx);
+
+			j = srcu_lockdep_next(__func__, "down_write", "synchronize_srcu",
+					      "up_write", i, cyclelen, deadlock);
+			down_write(rwsems[i]);
+			if (j >= 0)
+				synchronize_srcu(srcus[j]);
+			up_write(rwsems[i]);
+		}
+		return;
+	}
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+	if (testtype == 3) {
+		pr_info("%s: test_srcu_lockdep = %05d: SRCU and Tasks Trace RCU %d-way %sdeadlock.\n",
+			__func__, test_srcu_lockdep, cyclelen, deadlock ? "" : "non-");
+		if (deadlock && cyclelen == 1)
+			pr_info("%s: Expect hang.\n", __func__);
+		for (i = 0; i < cyclelen; i++) {
+			char *fl = i == 0 ? "rcu_read_lock_trace" : "srcu_read_lock";
+			char *fs = i == cyclelen - 1 ? "synchronize_rcu_tasks_trace"
+						     : "synchronize_srcu";
+			char *fu = i == 0 ? "rcu_read_unlock_trace" : "srcu_read_unlock";
+
+			j = srcu_lockdep_next(__func__, fl, fs, fu, i, cyclelen, deadlock);
+			if (i == 0)
+				rcu_read_lock_trace();
+			else
+				idx = srcu_read_lock(srcus[i]);
+			if (j >= 0) {
+				if (i == cyclelen - 1)
+					synchronize_rcu_tasks_trace();
+				else
+					synchronize_srcu(srcus[j]);
+			}
+			if (i == 0)
+				rcu_read_unlock_trace();
+			else
+				srcu_read_unlock(srcus[i], idx);
+		}
+		return;
+	}
+#endif // #ifdef CONFIG_TASKS_TRACE_RCU
+
+err_out:
+	pr_info("%s: test_srcu_lockdep = %05d does nothing.\n", __func__, test_srcu_lockdep);
+	pr_info("%s: test_srcu_lockdep = DNNL.\n", __func__);
+	pr_info("%s: D: Deadlock if nonzero.\n", __func__);
+	pr_info("%s: NN: Test number, 0=SRCU, 1=SRCU/mutex, 2=SRCU/rwsem, 3=SRCU/Tasks Trace RCU.\n", __func__);
+	pr_info("%s: L: Cycle length.\n", __func__);
+	if (!IS_ENABLED(CONFIG_TASKS_TRACE_RCU))
+		pr_info("%s: NN=3 disallowed because kernel is built with CONFIG_TASKS_TRACE_RCU=n\n", __func__);
+}
+
 static int __init
 rcu_torture_init(void)
 {
···
 		pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
 		fqs_duration = 0;
 	}
+	if (nocbs_nthreads != 0 && (cur_ops != &rcu_ops ||
+				    !IS_ENABLED(CONFIG_RCU_NOCB_CPU))) {
+		pr_alert("rcu-torture types: %s and CONFIG_RCU_NOCB_CPU=%d, nocb toggle disabled.\n",
+			 cur_ops->name, IS_ENABLED(CONFIG_RCU_NOCB_CPU));
+		nocbs_nthreads = 0;
+	}
 	if (cur_ops->init)
 		cur_ops->init();
+
+	rcu_torture_init_srcu_lockdep();
 
 	if (nreaders >= 0) {
 		nrealreaders = nreaders;
···
 	atomic_set(&n_rcu_torture_error, 0);
 	n_rcu_torture_barrier_error = 0;
 	n_rcu_torture_boost_ktrerror = 0;
-	n_rcu_torture_boost_rterror = 0;
 	n_rcu_torture_boost_failure = 0;
 	n_rcu_torture_boosts = 0;
 	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)

kernel/rcu/refscale.c

···
 static int
 ref_scale_shutdown(void *arg)
 {
-	wait_event(shutdown_wq, shutdown_start);
+	wait_event_idle(shutdown_wq, shutdown_start);
 
 	smp_mb(); // Wake before output.
 	ref_scale_cleanup();

kernel/rcu/srcutiny.c

···
 {
 	struct rcu_synchronize rs;
 
+	srcu_lock_sync(&ssp->dep_map);
+
 	RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
 			lock_is_held(&rcu_bh_lock_map) ||
 			lock_is_held(&rcu_lock_map) ||

kernel/rcu/srcutree.c

···
 
 #define spin_trylock_irqsave_rcu_node(p, flags)					\
 ({										\
-	bool ___locked = spin_trylock_irqsave(&ACCESS_PRIVATE(p, lock), flags);	\
+	bool ___locked = spin_trylock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \
 										\
 	if (___locked)								\
 		smp_mb__after_unlock_lock();					\
···
 		spin_lock_init(&ACCESS_PRIVATE(sdp, lock));
 		rcu_segcblist_init(&sdp->srcu_cblist);
 		sdp->srcu_cblist_invoking = false;
-		sdp->srcu_gp_seq_needed = ssp->srcu_gp_seq;
-		sdp->srcu_gp_seq_needed_exp = ssp->srcu_gp_seq;
+		sdp->srcu_gp_seq_needed = ssp->srcu_sup->srcu_gp_seq;
+		sdp->srcu_gp_seq_needed_exp = ssp->srcu_sup->srcu_gp_seq;
 		sdp->mynode = NULL;
 		sdp->cpu = cpu;
 		INIT_WORK(&sdp->work, srcu_invoke_callbacks);
···
 
 	/* Initialize geometry if it has not already been initialized. */
 	rcu_init_geometry();
-	ssp->node = kcalloc(rcu_num_nodes, sizeof(*ssp->node), gfp_flags);
-	if (!ssp->node)
+	ssp->srcu_sup->node = kcalloc(rcu_num_nodes, sizeof(*ssp->srcu_sup->node), gfp_flags);
+	if (!ssp->srcu_sup->node)
 		return false;
 
 	/* Work out the overall tree geometry. */
-	ssp->level[0] = &ssp->node[0];
+	ssp->srcu_sup->level[0] = &ssp->srcu_sup->node[0];
 	for (i = 1; i < rcu_num_lvls; i++)
-		ssp->level[i] = ssp->level[i - 1] + num_rcu_lvl[i - 1];
+		ssp->srcu_sup->level[i] = ssp->srcu_sup->level[i - 1] + num_rcu_lvl[i - 1];
 	rcu_init_levelspread(levelspread, num_rcu_lvl);
 
 	/* Each pass through this loop initializes one srcu_node structure. */
···
 		snp->srcu_gp_seq_needed_exp = SRCU_SNP_INIT_SEQ;
 		snp->grplo = -1;
 		snp->grphi = -1;
-		if (snp == &ssp->node[0]) {
+		if (snp == &ssp->srcu_sup->node[0]) {
 			/* Root node, special case. */
 			snp->srcu_parent = NULL;
 			continue;
 		}
 
 		/* Non-root node. */
-		if (snp == ssp->level[level + 1])
+		if (snp == ssp->srcu_sup->level[level + 1])
 			level++;
-		snp->srcu_parent = ssp->level[level - 1] +
-				   (snp - ssp->level[level]) /
+		snp->srcu_parent = ssp->srcu_sup->level[level - 1] +
+				   (snp - ssp->srcu_sup->level[level]) /
 				   levelspread[level - 1];
 	}
 
···
 	 * leaves of the srcu_node tree.
 	 */
 	level = rcu_num_lvls - 1;
-	snp_first = ssp->level[level];
+	snp_first = ssp->srcu_sup->level[level];
 	for_each_possible_cpu(cpu) {
 		sdp = per_cpu_ptr(ssp->sda, cpu);
 		sdp->mynode = &snp_first[cpu / levelspread[level]];
···
 		}
 		sdp->grpmask = 1 << (cpu - sdp->mynode->grplo);
 	}
-	smp_store_release(&ssp->srcu_size_state, SRCU_SIZE_WAIT_BARRIER);
+	smp_store_release(&ssp->srcu_sup->srcu_size_state, SRCU_SIZE_WAIT_BARRIER);
 	return true;
 }
 
···
  */
 static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
 {
-	ssp->srcu_size_state = SRCU_SIZE_SMALL;
-	ssp->node = NULL;
-	mutex_init(&ssp->srcu_cb_mutex);
-	mutex_init(&ssp->srcu_gp_mutex);
+	if (!is_static)
+		ssp->srcu_sup = kzalloc(sizeof(*ssp->srcu_sup), GFP_KERNEL);
+	if (!ssp->srcu_sup)
+		return -ENOMEM;
+	if (!is_static)
+		spin_lock_init(&ACCESS_PRIVATE(ssp->srcu_sup, lock));
+	ssp->srcu_sup->srcu_size_state = SRCU_SIZE_SMALL;
+	ssp->srcu_sup->node = NULL;
+	mutex_init(&ssp->srcu_sup->srcu_cb_mutex);
+	mutex_init(&ssp->srcu_sup->srcu_gp_mutex);
 	ssp->srcu_idx = 0;
-	ssp->srcu_gp_seq = 0;
-	ssp->srcu_barrier_seq = 0;
-	mutex_init(&ssp->srcu_barrier_mutex);
-	atomic_set(&ssp->srcu_barrier_cpu_cnt, 0);
-	INIT_DELAYED_WORK(&ssp->work, process_srcu);
-	ssp->sda_is_static = is_static;
+	ssp->srcu_sup->srcu_gp_seq = 0;
+	ssp->srcu_sup->srcu_barrier_seq = 0;
+	mutex_init(&ssp->srcu_sup->srcu_barrier_mutex);
+	atomic_set(&ssp->srcu_sup->srcu_barrier_cpu_cnt, 0);
+	INIT_DELAYED_WORK(&ssp->srcu_sup->work, process_srcu);
+	ssp->srcu_sup->sda_is_static = is_static;
 	if (!is_static)
 		ssp->sda = alloc_percpu(struct srcu_data);
-	if (!ssp->sda)
+	if (!ssp->sda) {
+		if (!is_static)
+			kfree(ssp->srcu_sup);
 		return -ENOMEM;
+	}
 	init_srcu_struct_data(ssp);
-	ssp->srcu_gp_seq_needed_exp = 0;
-	ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();
-	if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) {
+	ssp->srcu_sup->srcu_gp_seq_needed_exp = 0;
+	ssp->srcu_sup->srcu_last_gp_end = ktime_get_mono_fast_ns();
+	if (READ_ONCE(ssp->srcu_sup->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) {
 		if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC)) {
-			if (!ssp->sda_is_static) {
+			if (!ssp->srcu_sup->sda_is_static) {
 				free_percpu(ssp->sda);
 				ssp->sda = NULL;
+				kfree(ssp->srcu_sup);
 				return -ENOMEM;
 			}
 		} else {
-			WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_BIG);
+			WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_BIG);
 		}
 	}
-	smp_store_release(&ssp->srcu_gp_seq_needed, 0); /* Init done. */
+	ssp->srcu_sup->srcu_ssp = ssp;
+	smp_store_release(&ssp->srcu_sup->srcu_gp_seq_needed, 0); /* Init done. */
 	return 0;
 }
 
···
 	/* Don't re-initialize a lock while it is held. */
 	debug_check_no_locks_freed((void *)ssp, sizeof(*ssp));
 	lockdep_init_map(&ssp->dep_map, name, key, 0);
-	spin_lock_init(&ACCESS_PRIVATE(ssp, lock));
 	return init_srcu_struct_fields(ssp, false);
 }
 EXPORT_SYMBOL_GPL(__init_srcu_struct);
···
  */
 int init_srcu_struct(struct srcu_struct *ssp)
 {
-	spin_lock_init(&ACCESS_PRIVATE(ssp, lock));
 	return init_srcu_struct_fields(ssp, false);
 }
 EXPORT_SYMBOL_GPL(init_srcu_struct);
···
  */
 static void __srcu_transition_to_big(struct srcu_struct *ssp)
 {
-	lockdep_assert_held(&ACCESS_PRIVATE(ssp, lock));
-	smp_store_release(&ssp->srcu_size_state, SRCU_SIZE_ALLOC);
+	lockdep_assert_held(&ACCESS_PRIVATE(ssp->srcu_sup, lock));
+	smp_store_release(&ssp->srcu_sup->srcu_size_state, SRCU_SIZE_ALLOC);
 }
 
 /*
···
 	unsigned long flags;
 
 	/* Double-checked locking on ->srcu_size-state. */
-	if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL)
+	if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) != SRCU_SIZE_SMALL)
 		return;
-	spin_lock_irqsave_rcu_node(ssp, flags);
-	if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL) {
-		spin_unlock_irqrestore_rcu_node(ssp, flags);
+	spin_lock_irqsave_rcu_node(ssp->srcu_sup, flags);
+	if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) != SRCU_SIZE_SMALL) {
+		spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
 		return;
 	}
 	__srcu_transition_to_big(ssp);
-	spin_unlock_irqrestore_rcu_node(ssp, flags);
+	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
 }
 
 /*
···
 {
 	unsigned long j;
 
-	if (!SRCU_SIZING_IS_CONTEND() || ssp->srcu_size_state)
+	if (!SRCU_SIZING_IS_CONTEND() || ssp->srcu_sup->srcu_size_state)
 		return;
 	j = jiffies;
-	if (ssp->srcu_size_jiffies != j) {
-		ssp->srcu_size_jiffies = j;
-		ssp->srcu_n_lock_retries = 0;
+	if (ssp->srcu_sup->srcu_size_jiffies != j) {
+		ssp->srcu_sup->srcu_size_jiffies = j;
+		ssp->srcu_sup->srcu_n_lock_retries = 0;
 	}
-	if (++ssp->srcu_n_lock_retries <= small_contention_lim)
+	if (++ssp->srcu_sup->srcu_n_lock_retries <= small_contention_lim)
 		return;
 	__srcu_transition_to_big(ssp);
 }
···
 
 	if (spin_trylock_irqsave_rcu_node(sdp, *flags))
 		return;
-	spin_lock_irqsave_rcu_node(ssp, *flags);
+	spin_lock_irqsave_rcu_node(ssp->srcu_sup, *flags);
 	spin_lock_irqsave_check_contention(ssp);
-	spin_unlock_irqrestore_rcu_node(ssp, *flags);
+	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, *flags);
 	spin_lock_irqsave_rcu_node(sdp, *flags);
 }
 
···
  */
 static void spin_lock_irqsave_ssp_contention(struct srcu_struct *ssp, unsigned long *flags)
 {
-	if (spin_trylock_irqsave_rcu_node(ssp, *flags))
+	if (spin_trylock_irqsave_rcu_node(ssp->srcu_sup, *flags))
 		return;
-	spin_lock_irqsave_rcu_node(ssp, *flags);
+	spin_lock_irqsave_rcu_node(ssp->srcu_sup, *flags);
 	spin_lock_irqsave_check_contention(ssp);
 }
 
···
 	unsigned long flags;
 
 	/* The smp_load_acquire() pairs with the smp_store_release(). */
-	if (!rcu_seq_state(smp_load_acquire(&ssp->srcu_gp_seq_needed))) /*^^^*/
+	if (!rcu_seq_state(smp_load_acquire(&ssp->srcu_sup->srcu_gp_seq_needed))) /*^^^*/
 		return; /* Already initialized. */
-	spin_lock_irqsave_rcu_node(ssp, flags);
-	if (!rcu_seq_state(ssp->srcu_gp_seq_needed)) {
-		spin_unlock_irqrestore_rcu_node(ssp, flags);
+	spin_lock_irqsave_rcu_node(ssp->srcu_sup, flags);
+	if (!rcu_seq_state(ssp->srcu_sup->srcu_gp_seq_needed)) {
+		spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
 		return;
 	}
 	init_srcu_struct_fields(ssp, true);
-	spin_unlock_irqrestore_rcu_node(ssp, flags);
+	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
 }
 
 /*
···
 	unsigned long gpstart;
 	unsigned long j;
 	unsigned long jbase = SRCU_INTERVAL;
+	struct srcu_usage *sup = ssp->srcu_sup;
 
-	if (ULONG_CMP_LT(READ_ONCE(ssp->srcu_gp_seq), READ_ONCE(ssp->srcu_gp_seq_needed_exp)))
+	if (ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_needed_exp)))
 		jbase = 0;
-	if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq))) {
+	if (rcu_seq_state(READ_ONCE(sup->srcu_gp_seq))) {
 		j = jiffies - 1;
-		gpstart = READ_ONCE(ssp->srcu_gp_start);
+		gpstart = READ_ONCE(sup->srcu_gp_start);
 		if (time_after(j, gpstart))
 			jbase += j - gpstart;
 		if (!jbase) {
-			WRITE_ONCE(ssp->srcu_n_exp_nodelay, READ_ONCE(ssp->srcu_n_exp_nodelay) + 1);
-			if (READ_ONCE(ssp->srcu_n_exp_nodelay) > srcu_max_nodelay_phase)
+			WRITE_ONCE(sup->srcu_n_exp_nodelay, READ_ONCE(sup->srcu_n_exp_nodelay) + 1);
+			if (READ_ONCE(sup->srcu_n_exp_nodelay) > srcu_max_nodelay_phase)
 				jbase = 1;
 		}
 	}
···
 void cleanup_srcu_struct(struct srcu_struct *ssp)
 {
 	int cpu;
+	struct srcu_usage *sup = ssp->srcu_sup;
 
 	if (WARN_ON(!srcu_get_delay(ssp)))
 		return; /* Just leak it! */
 	if (WARN_ON(srcu_readers_active(ssp)))
 		return; /* Just leak it! */
-	flush_delayed_work(&ssp->work);
+	flush_delayed_work(&sup->work);
 	for_each_possible_cpu(cpu) {
 		struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu);
 
···
 		if (WARN_ON(rcu_segcblist_n_cbs(&sdp->srcu_cblist)))
 			return; /* Forgot srcu_barrier(), so just leak it! */
 	}
-	if (WARN_ON(rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) != SRCU_STATE_IDLE) ||
-	    WARN_ON(rcu_seq_current(&ssp->srcu_gp_seq) != ssp->srcu_gp_seq_needed) ||
+	if (WARN_ON(rcu_seq_state(READ_ONCE(sup->srcu_gp_seq)) != SRCU_STATE_IDLE) ||
+	    WARN_ON(rcu_seq_current(&sup->srcu_gp_seq) != sup->srcu_gp_seq_needed) ||
 	    WARN_ON(srcu_readers_active(ssp))) {
 		pr_info("%s: Active srcu_struct %p read state: %d gp state: %lu/%lu\n",
-			__func__, ssp, rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)),
-			rcu_seq_current(&ssp->srcu_gp_seq), ssp->srcu_gp_seq_needed);
+			__func__, ssp, rcu_seq_state(READ_ONCE(sup->srcu_gp_seq)),
+			rcu_seq_current(&sup->srcu_gp_seq), sup->srcu_gp_seq_needed);
 		return; /* Caller forgot to stop doing call_srcu()? */
 	}
-	if (!ssp->sda_is_static) {
+	kfree(sup->node);
+	sup->node = NULL;
+	sup->srcu_size_state = SRCU_SIZE_SMALL;
+	if (!sup->sda_is_static) {
 		free_percpu(ssp->sda);
 		ssp->sda = NULL;
+		kfree(sup);
+		ssp->srcu_sup = NULL;
 	}
-	kfree(ssp->node);
-	ssp->node = NULL;
-	ssp->srcu_size_state = SRCU_SIZE_SMALL;
 }
 EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
···
 	struct srcu_data *sdp;
 	int state;
 
-	if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
+	if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
 		sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id());
 	else
 		sdp = this_cpu_ptr(ssp->sda);
-	lockdep_assert_held(&ACCESS_PRIVATE(ssp, lock));
-	WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed));
+	lockdep_assert_held(&ACCESS_PRIVATE(ssp->srcu_sup, lock));
+	WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_sup->srcu_gp_seq, ssp->srcu_sup->srcu_gp_seq_needed));
 	spin_lock_rcu_node(sdp);  /* Interrupts already disabled. */
 	rcu_segcblist_advance(&sdp->srcu_cblist,
-			      rcu_seq_current(&ssp->srcu_gp_seq));
+			      rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
 	(void)rcu_segcblist_accelerate(&sdp->srcu_cblist,
-				       rcu_seq_snap(&ssp->srcu_gp_seq));
+				       rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq));
 	spin_unlock_rcu_node(sdp);  /* Interrupts remain disabled. */
-	WRITE_ONCE(ssp->srcu_gp_start, jiffies);
-	WRITE_ONCE(ssp->srcu_n_exp_nodelay, 0);
+	WRITE_ONCE(ssp->srcu_sup->srcu_gp_start, jiffies);
+	WRITE_ONCE(ssp->srcu_sup->srcu_n_exp_nodelay, 0);
 	smp_mb(); /* Order prior store to ->srcu_gp_seq_needed vs. GP start. */
-	rcu_seq_start(&ssp->srcu_gp_seq);
-	state = rcu_seq_state(ssp->srcu_gp_seq);
+	rcu_seq_start(&ssp->srcu_sup->srcu_gp_seq);
+	state = rcu_seq_state(ssp->srcu_sup->srcu_gp_seq);
 	WARN_ON_ONCE(state != SRCU_STATE_SCAN1);
 }
 
···
 	unsigned long sgsne;
 	struct srcu_node *snp;
 	int ss_state;
+	struct srcu_usage *sup = ssp->srcu_sup;
 
 	/* Prevent more than one additional grace period. */
-	mutex_lock(&ssp->srcu_cb_mutex);
+	mutex_lock(&sup->srcu_cb_mutex);
 
 	/* End the current grace period. */
-	spin_lock_irq_rcu_node(ssp);
-	idx = rcu_seq_state(ssp->srcu_gp_seq);
+	spin_lock_irq_rcu_node(sup);
+	idx = rcu_seq_state(sup->srcu_gp_seq);
 	WARN_ON_ONCE(idx != SRCU_STATE_SCAN2);
-	if (ULONG_CMP_LT(READ_ONCE(ssp->srcu_gp_seq), READ_ONCE(ssp->srcu_gp_seq_needed_exp)))
+	if (ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_needed_exp)))
 		cbdelay = 0;
 
-	WRITE_ONCE(ssp->srcu_last_gp_end, ktime_get_mono_fast_ns());
-	rcu_seq_end(&ssp->srcu_gp_seq);
-	gpseq = rcu_seq_current(&ssp->srcu_gp_seq);
-	if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, gpseq))
-		WRITE_ONCE(ssp->srcu_gp_seq_needed_exp, gpseq);
-	spin_unlock_irq_rcu_node(ssp);
-	mutex_unlock(&ssp->srcu_gp_mutex);
+	WRITE_ONCE(sup->srcu_last_gp_end, ktime_get_mono_fast_ns());
+	rcu_seq_end(&sup->srcu_gp_seq);
+	gpseq = rcu_seq_current(&sup->srcu_gp_seq);
+	if (ULONG_CMP_LT(sup->srcu_gp_seq_needed_exp, gpseq))
+		WRITE_ONCE(sup->srcu_gp_seq_needed_exp, gpseq);
+	spin_unlock_irq_rcu_node(sup);
+	mutex_unlock(&sup->srcu_gp_mutex);
 	/* A new grace period can start at this point.  But only one. */
 
 	/* Initiate callback invocation as needed. */
-	ss_state = smp_load_acquire(&ssp->srcu_size_state);
+	ss_state = smp_load_acquire(&sup->srcu_size_state);
 	if (ss_state < SRCU_SIZE_WAIT_BARRIER) {
 		srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, get_boot_cpu_id()),
 					cbdelay);
···
 		srcu_for_each_node_breadth_first(ssp, snp) {
 			spin_lock_irq_rcu_node(snp);
 			cbs = false;
-			last_lvl = snp >= ssp->level[rcu_num_lvls - 1];
+			last_lvl = snp >= sup->level[rcu_num_lvls - 1];
 			if (last_lvl)
 				cbs = ss_state < SRCU_SIZE_BIG || snp->srcu_have_cbs[idx] == gpseq;
 			snp->srcu_have_cbs[idx] = gpseq;
···
 		}
 
 	/* Callback initiation done, allow grace periods after next. */
-	mutex_unlock(&ssp->srcu_cb_mutex);
+	mutex_unlock(&sup->srcu_cb_mutex);
 
 	/* Start a new grace period if needed. */
-	spin_lock_irq_rcu_node(ssp);
-	gpseq = rcu_seq_current(&ssp->srcu_gp_seq);
+	spin_lock_irq_rcu_node(sup);
+	gpseq = rcu_seq_current(&sup->srcu_gp_seq);
 	if (!rcu_seq_state(gpseq) &&
-	    ULONG_CMP_LT(gpseq, ssp->srcu_gp_seq_needed)) {
+	    ULONG_CMP_LT(gpseq, sup->srcu_gp_seq_needed)) {
 		srcu_gp_start(ssp);
-		spin_unlock_irq_rcu_node(ssp);
+		spin_unlock_irq_rcu_node(sup);
 		srcu_reschedule(ssp, 0);
 	} else {
-		spin_unlock_irq_rcu_node(ssp);
+		spin_unlock_irq_rcu_node(sup);
 	}
 
 	/* Transition to big if needed. */
···
 		if (ss_state == SRCU_SIZE_ALLOC)
 			init_srcu_struct_nodes(ssp, GFP_KERNEL);
 		else
-			smp_store_release(&ssp->srcu_size_state, ss_state + 1);
+			smp_store_release(&sup->srcu_size_state, ss_state + 1);
 	}
 }
 
···
 	if (snp)
 		for (; snp != NULL; snp = snp->srcu_parent) {
 			sgsne = READ_ONCE(snp->srcu_gp_seq_needed_exp);
-			if (WARN_ON_ONCE(rcu_seq_done(&ssp->srcu_gp_seq, s)) ||
+			if (WARN_ON_ONCE(rcu_seq_done(&ssp->srcu_sup->srcu_gp_seq, s)) ||
 			    (!srcu_invl_snp_seq(sgsne) && ULONG_CMP_GE(sgsne, s)))
 				return;
 			spin_lock_irqsave_rcu_node(snp, flags);
···
 			spin_unlock_irqrestore_rcu_node(snp, flags);
 		}
 	spin_lock_irqsave_ssp_contention(ssp, &flags);
-	if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, s))
-		WRITE_ONCE(ssp->srcu_gp_seq_needed_exp, s);
-	spin_unlock_irqrestore_rcu_node(ssp, flags);
+	if (ULONG_CMP_LT(ssp->srcu_sup->srcu_gp_seq_needed_exp, s))
+		WRITE_ONCE(ssp->srcu_sup->srcu_gp_seq_needed_exp, s);
+	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
 }
 
 /*
···
 	struct srcu_node *snp;
 	struct srcu_node *snp_leaf;
 	unsigned long snp_seq;
+	struct srcu_usage *sup = ssp->srcu_sup;
 
 	/* Ensure that snp node tree is fully initialized before traversing it */
-	if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
+	if (smp_load_acquire(&sup->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
 		snp_leaf = NULL;
 	else
 		snp_leaf = sdp->mynode;
···
 	if (snp_leaf)
 		/* Each pass through the loop does one level of the srcu_node tree. */
 		for (snp = snp_leaf; snp != NULL; snp = snp->srcu_parent) {
-			if (WARN_ON_ONCE(rcu_seq_done(&ssp->srcu_gp_seq, s)) && snp != snp_leaf)
+			if (WARN_ON_ONCE(rcu_seq_done(&sup->srcu_gp_seq, s)) && snp != snp_leaf)
 				return; /* GP already done and CBs recorded. */
 			spin_lock_irqsave_rcu_node(snp, flags);
 			snp_seq = snp->srcu_have_cbs[idx];
···
 
 	/* Top of tree, must ensure the grace period will be started. */
 	spin_lock_irqsave_ssp_contention(ssp, &flags);
-	if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed, s)) {
+	if (ULONG_CMP_LT(sup->srcu_gp_seq_needed, s)) {
 		/*
 		 * Record need for grace period s.  Pair with load
 		 * acquire setting up for initialization.
 		 */
-		smp_store_release(&ssp->srcu_gp_seq_needed, s); /*^^^*/
+		smp_store_release(&sup->srcu_gp_seq_needed, s); /*^^^*/
 	}
-	if (!do_norm && ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, s))
-		WRITE_ONCE(ssp->srcu_gp_seq_needed_exp, s);
+	if (!do_norm && ULONG_CMP_LT(sup->srcu_gp_seq_needed_exp, s))
+		WRITE_ONCE(sup->srcu_gp_seq_needed_exp, s);
 
 	/* If grace period not already in progress, start it. */
-	if (!WARN_ON_ONCE(rcu_seq_done(&ssp->srcu_gp_seq, s)) &&
-	    rcu_seq_state(ssp->srcu_gp_seq) == SRCU_STATE_IDLE) {
-		WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed));
+	if (!WARN_ON_ONCE(rcu_seq_done(&sup->srcu_gp_seq, s)) &&
+	    rcu_seq_state(sup->srcu_gp_seq) == SRCU_STATE_IDLE) {
+		WARN_ON_ONCE(ULONG_CMP_GE(sup->srcu_gp_seq, sup->srcu_gp_seq_needed));
 		srcu_gp_start(ssp);
 
 		// And how can that list_add() in the "else" clause
···
 		// can only be executed during early boot when there is only
 		// the one boot CPU running with interrupts still disabled.
 		if (likely(srcu_init_done))
-			queue_delayed_work(rcu_gp_wq, &ssp->work,
+			queue_delayed_work(rcu_gp_wq, &sup->work,
 					   !!srcu_get_delay(ssp));
-		else if (list_empty(&ssp->work.work.entry))
-			list_add(&ssp->work.work.entry, &srcu_boot_list);
+		else if (list_empty(&sup->work.work.entry))
+			list_add(&sup->work.work.entry, &srcu_boot_list);
 	}
-	spin_unlock_irqrestore_rcu_node(ssp, flags);
+	spin_unlock_irqrestore_rcu_node(sup, flags);
 }
 
 /*
···
 static void srcu_flip(struct srcu_struct *ssp)
 {
 	/*
-	 * Ensure that if this updater saw a given reader's increment
-	 * from __srcu_read_lock(), that reader was using an old value
-	 * of ->srcu_idx.  Also ensure that if a given reader sees the
-	 * new value of ->srcu_idx, this updater's earlier scans cannot
-	 * have seen that reader's increments (which is OK, because this
-	 * grace period need not wait on that reader).
+	 * Because the flip of ->srcu_idx is executed only if the
+	 * preceding call to srcu_readers_active_idx_check() found that
+	 * the ->srcu_unlock_count[] and ->srcu_lock_count[] sums matched
+	 * and because that summing uses atomic_long_read(), there is
+	 * ordering due to a control dependency between that summing and
+	 * the WRITE_ONCE() in this call to srcu_flip().  This ordering
+	 * ensures that if this updater saw a given reader's increment from
+	 * __srcu_read_lock(), that reader was using a value of ->srcu_idx
+	 * from before the previous call to srcu_flip(), which should be
+	 * quite rare.  This ordering thus helps forward progress because
+	 * the grace period could otherwise be delayed by additional
+	 * calls to __srcu_read_lock() using that old (soon to be new)
+	 * value of ->srcu_idx.
+	 *
+	 * This sum-equality check and ordering also ensures that if
+	 * a given call to __srcu_read_lock() uses the new value of
+	 * ->srcu_idx, this updater's earlier scans cannot have seen
+	 * that reader's increments, which is all to the good, because
+	 * this grace period need not wait on that reader.  After all,
+	 * if those earlier scans had seen that reader, there would have
+	 * been a sum mismatch and this code would not be reached.
+	 *
+	 * This means that the following smp_mb() is redundant, but
+	 * it stays until either (1) Compilers learn about this sort of
+	 * control dependency or (2) Some production workload running on
+	 * a production system is unduly delayed by this slowpath smp_mb().
 	 */
 	smp_mb(); /* E */  /* Pairs with B and C. */
 
-	WRITE_ONCE(ssp->srcu_idx, ssp->srcu_idx + 1);
+	WRITE_ONCE(ssp->srcu_idx, ssp->srcu_idx + 1); // Flip the counter.
 
 	/*
 	 * Ensure that if the updater misses an __srcu_read_unlock()
···
 
 	/* First, see if enough time has passed since the last GP. */
 	t = ktime_get_mono_fast_ns();
-	tlast = READ_ONCE(ssp->srcu_last_gp_end);
+	tlast = READ_ONCE(ssp->srcu_sup->srcu_last_gp_end);
 	if (exp_holdoff == 0 ||
 	    time_in_range_open(t, tlast, tlast + exp_holdoff))
 		return false; /* Too soon after last GP. */
 
 	/* Next, check for probable idleness. */
-	curseq = rcu_seq_current(&ssp->srcu_gp_seq);
+	curseq = rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq);
 	smp_mb(); /* Order ->srcu_gp_seq with ->srcu_gp_seq_needed. */
-	if (ULONG_CMP_LT(curseq, READ_ONCE(ssp->srcu_gp_seq_needed)))
+	if (ULONG_CMP_LT(curseq, READ_ONCE(ssp->srcu_sup->srcu_gp_seq_needed)))
 		return false; /* Grace period in progress, so not idle. */
 	smp_mb(); /* Order ->srcu_gp_seq with prior access. */
-	if (curseq != rcu_seq_current(&ssp->srcu_gp_seq))
+	if (curseq != rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq))
 		return false; /* GP # changed, so not idle. */
 	return true; /* With reasonable probability, idle! */
 }
···
 	 * sequence number cannot wrap around in the meantime.
 	 */
 	idx = __srcu_read_lock_nmisafe(ssp);
-	ss_state = smp_load_acquire(&ssp->srcu_size_state);
+	ss_state = smp_load_acquire(&ssp->srcu_sup->srcu_size_state);
 	if (ss_state < SRCU_SIZE_WAIT_CALL)
 		sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id());
 	else
···
 	if (rhp)
 		rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp);
 	rcu_segcblist_advance(&sdp->srcu_cblist,
-			      rcu_seq_current(&ssp->srcu_gp_seq));
-	s = rcu_seq_snap(&ssp->srcu_gp_seq);
+			      rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
+	s = rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq);
 	(void)rcu_segcblist_accelerate(&sdp->srcu_cblist, s);
 	if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) {
 		sdp->srcu_gp_seq_needed = s;
···
 static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm)
 {
 	struct rcu_synchronize rcu;
+
+	srcu_lock_sync(&ssp->dep_map);
 
 	RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
 			 lock_is_held(&rcu_bh_lock_map) ||
···
 	// Any prior manipulation of SRCU-protected data must happen
 	// before the load from ->srcu_gp_seq.
 	smp_mb();
-	return rcu_seq_snap(&ssp->srcu_gp_seq);
+	return rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq);
 }
 EXPORT_SYMBOL_GPL(get_state_synchronize_srcu);
 
···
  */
 bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie)
 {
-	if (!rcu_seq_done(&ssp->srcu_gp_seq, cookie))
+	if (!rcu_seq_done(&ssp->srcu_sup->srcu_gp_seq, cookie))
 		return false;
 	// Ensure that the end of the SRCU grace period happens before
 	// any subsequent code that the caller might execute.
···
 
 	sdp = container_of(rhp, struct srcu_data, srcu_barrier_head);
 	ssp = sdp->ssp;
-	if (atomic_dec_and_test(&ssp->srcu_barrier_cpu_cnt))
-		complete(&ssp->srcu_barrier_completion);
+	if (atomic_dec_and_test(&ssp->srcu_sup->srcu_barrier_cpu_cnt))
+		complete(&ssp->srcu_sup->srcu_barrier_completion);
 }
 
 /*
···
 static void srcu_barrier_one_cpu(struct srcu_struct *ssp, struct srcu_data *sdp)
 {
 	spin_lock_irq_rcu_node(sdp);
-	atomic_inc(&ssp->srcu_barrier_cpu_cnt);
+	atomic_inc(&ssp->srcu_sup->srcu_barrier_cpu_cnt);
 	sdp->srcu_barrier_head.func = srcu_barrier_cb;
 	debug_rcu_head_queue(&sdp->srcu_barrier_head);
 	if (!rcu_segcblist_entrain(&sdp->srcu_cblist,
 				   &sdp->srcu_barrier_head)) {
 		debug_rcu_head_unqueue(&sdp->srcu_barrier_head);
-		atomic_dec(&ssp->srcu_barrier_cpu_cnt);
+		atomic_dec(&ssp->srcu_sup->srcu_barrier_cpu_cnt);
 	}
 	spin_unlock_irq_rcu_node(sdp);
 }
···
 {
 	int cpu;
 	int idx;
-	unsigned long s = rcu_seq_snap(&ssp->srcu_barrier_seq);
+	unsigned long s = rcu_seq_snap(&ssp->srcu_sup->srcu_barrier_seq);
 
 	check_init_srcu_struct(ssp);
-	mutex_lock(&ssp->srcu_barrier_mutex);
-	if (rcu_seq_done(&ssp->srcu_barrier_seq, s)) {
+	mutex_lock(&ssp->srcu_sup->srcu_barrier_mutex);
+	if (rcu_seq_done(&ssp->srcu_sup->srcu_barrier_seq, s)) {
 		smp_mb(); /* Force ordering following return. */
-		mutex_unlock(&ssp->srcu_barrier_mutex);
+		mutex_unlock(&ssp->srcu_sup->srcu_barrier_mutex);
 		return; /* Someone else did our work for us. */
 	}
-	rcu_seq_start(&ssp->srcu_barrier_seq);
-	init_completion(&ssp->srcu_barrier_completion);
+	rcu_seq_start(&ssp->srcu_sup->srcu_barrier_seq);
+	init_completion(&ssp->srcu_sup->srcu_barrier_completion);
 
 	/* Initial count prevents reaching zero until all CBs are posted. */
-	atomic_set(&ssp->srcu_barrier_cpu_cnt, 1);
+	atomic_set(&ssp->srcu_sup->srcu_barrier_cpu_cnt, 1);
 
 	idx = __srcu_read_lock_nmisafe(ssp);
-	if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
+	if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
 		srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda,	get_boot_cpu_id()));
 	else
 		for_each_possible_cpu(cpu)
···
 	__srcu_read_unlock_nmisafe(ssp, idx);
 
 	/* Remove the initial count, at which point reaching zero can happen. */
-	if (atomic_dec_and_test(&ssp->srcu_barrier_cpu_cnt))
-		complete(&ssp->srcu_barrier_completion);
-	wait_for_completion(&ssp->srcu_barrier_completion);
+	if (atomic_dec_and_test(&ssp->srcu_sup->srcu_barrier_cpu_cnt))
+		complete(&ssp->srcu_sup->srcu_barrier_completion);
+	wait_for_completion(&ssp->srcu_sup->srcu_barrier_completion);
 
-	rcu_seq_end(&ssp->srcu_barrier_seq);
-	mutex_unlock(&ssp->srcu_barrier_mutex);
+	rcu_seq_end(&ssp->srcu_sup->srcu_barrier_seq);
+	mutex_unlock(&ssp->srcu_sup->srcu_barrier_mutex);
 }
 EXPORT_SYMBOL_GPL(srcu_barrier);
 
···
 {
 	int idx;
 
-	mutex_lock(&ssp->srcu_gp_mutex);
+	mutex_lock(&ssp->srcu_sup->srcu_gp_mutex);
 
 	/*
 	 * Because readers might be delayed for an extended period after
···
 	 * The load-acquire ensures that we see the accesses performed
 	 * by the prior grace period.
 	 */
-	idx = rcu_seq_state(smp_load_acquire(&ssp->srcu_gp_seq)); /* ^^^ */
+	idx = rcu_seq_state(smp_load_acquire(&ssp->srcu_sup->srcu_gp_seq)); /* ^^^ */
 	if (idx == SRCU_STATE_IDLE) {
-		spin_lock_irq_rcu_node(ssp);
-		if (ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)) {
-			WARN_ON_ONCE(rcu_seq_state(ssp->srcu_gp_seq));
-			spin_unlock_irq_rcu_node(ssp);
-			mutex_unlock(&ssp->srcu_gp_mutex);
+		spin_lock_irq_rcu_node(ssp->srcu_sup);
+		if (ULONG_CMP_GE(ssp->srcu_sup->srcu_gp_seq, ssp->srcu_sup->srcu_gp_seq_needed)) {
+			WARN_ON_ONCE(rcu_seq_state(ssp->srcu_sup->srcu_gp_seq));
+			spin_unlock_irq_rcu_node(ssp->srcu_sup);
+			mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
 			return;
 		}
-		idx = rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq));
+		idx = rcu_seq_state(READ_ONCE(ssp->srcu_sup->srcu_gp_seq));
 		if (idx == SRCU_STATE_IDLE)
 			srcu_gp_start(ssp);
-		spin_unlock_irq_rcu_node(ssp);
+		spin_unlock_irq_rcu_node(ssp->srcu_sup);
 		if (idx != SRCU_STATE_IDLE) {
-			mutex_unlock(&ssp->srcu_gp_mutex);
+			mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
 			return; /* Someone else started the grace period. */
 		}
 	}
 
-	if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN1) {
+	if (rcu_seq_state(READ_ONCE(ssp->srcu_sup->srcu_gp_seq)) == SRCU_STATE_SCAN1) {
 		idx = 1 ^ (ssp->srcu_idx & 1);
 		if (!try_check_zero(ssp, idx, 1)) {
-			mutex_unlock(&ssp->srcu_gp_mutex);
+			mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
 			return; /* readers present, retry later. */
 		}
 		srcu_flip(ssp);
-		spin_lock_irq_rcu_node(ssp);
-		rcu_seq_set_state(&ssp->srcu_gp_seq, SRCU_STATE_SCAN2);
-		ssp->srcu_n_exp_nodelay = 0;
-		spin_unlock_irq_rcu_node(ssp);
+		spin_lock_irq_rcu_node(ssp->srcu_sup);
+		rcu_seq_set_state(&ssp->srcu_sup->srcu_gp_seq, SRCU_STATE_SCAN2);
+		ssp->srcu_sup->srcu_n_exp_nodelay = 0;
+		spin_unlock_irq_rcu_node(ssp->srcu_sup);
 	}
 
-	if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN2) {
+	if (rcu_seq_state(READ_ONCE(ssp->srcu_sup->srcu_gp_seq)) == SRCU_STATE_SCAN2) {
 
 		/*
 		 * SRCU read-side critical sections are normally short,
···
 		 */
 		idx = 1 ^ (ssp->srcu_idx & 1);
 		if (!try_check_zero(ssp, idx, 2)) {
-			mutex_unlock(&ssp->srcu_gp_mutex);
+			mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
 			return; /* readers present, retry later. */
 		}
-		ssp->srcu_n_exp_nodelay = 0;
+		ssp->srcu_sup->srcu_n_exp_nodelay = 0;
 		srcu_gp_end(ssp);  /* Releases ->srcu_gp_mutex. */
 	}
 }
···
 	rcu_cblist_init(&ready_cbs);
 	spin_lock_irq_rcu_node(sdp);
 	rcu_segcblist_advance(&sdp->srcu_cblist,
-			      rcu_seq_current(&ssp->srcu_gp_seq));
+			      rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
 	if (sdp->srcu_cblist_invoking ||
 	    !rcu_segcblist_ready_cbs(&sdp->srcu_cblist)) {
 		spin_unlock_irq_rcu_node(sdp);
···
 	spin_lock_irq_rcu_node(sdp);
 	rcu_segcblist_add_len(&sdp->srcu_cblist, -len);
 	(void)rcu_segcblist_accelerate(&sdp->srcu_cblist,
-				       rcu_seq_snap(&ssp->srcu_gp_seq));
+				       rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq));
 	sdp->srcu_cblist_invoking = false;
 	more = rcu_segcblist_ready_cbs(&sdp->srcu_cblist);
 	spin_unlock_irq_rcu_node(sdp);
···
 {
 	bool pushgp = true;
 
-	spin_lock_irq_rcu_node(ssp);
-	if (ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)) {
-		if (!WARN_ON_ONCE(rcu_seq_state(ssp->srcu_gp_seq))) {
+	spin_lock_irq_rcu_node(ssp->srcu_sup);
+	if (ULONG_CMP_GE(ssp->srcu_sup->srcu_gp_seq, ssp->srcu_sup->srcu_gp_seq_needed)) {
+		if (!WARN_ON_ONCE(rcu_seq_state(ssp->srcu_sup->srcu_gp_seq))) {
 			/* All requests fulfilled, time to go idle. */
 			pushgp = false;
 		}
-	} else if (!rcu_seq_state(ssp->srcu_gp_seq)) {
+	} else if (!rcu_seq_state(ssp->srcu_sup->srcu_gp_seq)) {
 		/* Outstanding request and no GP.  Start one. */
 		srcu_gp_start(ssp);
 	}
-	spin_unlock_irq_rcu_node(ssp);
+	spin_unlock_irq_rcu_node(ssp->srcu_sup);
 
 	if (pushgp)
-		queue_delayed_work(rcu_gp_wq, &ssp->work, delay);
+		queue_delayed_work(rcu_gp_wq, &ssp->srcu_sup->work, delay);
 }
 
 /*
···
 	unsigned long curdelay;
 	unsigned long j;
 	struct srcu_struct *ssp;
+	struct srcu_usage *sup;
 
-	ssp = container_of(work, struct srcu_struct, work.work);
+	sup = container_of(work, struct srcu_usage, work.work);
+	ssp = sup->srcu_ssp;
 
 	srcu_advance_state(ssp);
 	curdelay = srcu_get_delay(ssp);
 	if (curdelay) {
-		WRITE_ONCE(ssp->reschedule_count, 0);
+		WRITE_ONCE(sup->reschedule_count, 0);
 	} else {
 		j = jiffies;
-		if (READ_ONCE(ssp->reschedule_jiffies) == j) {
-			WRITE_ONCE(ssp->reschedule_count, READ_ONCE(ssp->reschedule_count) + 1);
-			if (READ_ONCE(ssp->reschedule_count) > srcu_max_nodelay)
+		if (READ_ONCE(sup->reschedule_jiffies) == j) {
+			WRITE_ONCE(sup->reschedule_count, READ_ONCE(sup->reschedule_count) + 1);
+			if (READ_ONCE(sup->reschedule_count) > srcu_max_nodelay)
 				curdelay = 1;
 		} else {
-			WRITE_ONCE(ssp->reschedule_count, 1);
-			WRITE_ONCE(ssp->reschedule_jiffies, j);
+			WRITE_ONCE(sup->reschedule_count, 1);
+			WRITE_ONCE(sup->reschedule_jiffies, j);
 		}
 	}
 	srcu_reschedule(ssp, curdelay);
···
 	if (test_type != SRCU_FLAVOR)
 		return;
 	*flags = 0;
-	*gp_seq = rcu_seq_current(&ssp->srcu_gp_seq);
+	*gp_seq = rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq);
 }
 EXPORT_SYMBOL_GPL(srcutorture_get_gp_data);
 
···
 	int cpu;
 	int idx;
 	unsigned long s0 = 0, s1 = 0;
-	int ss_state = READ_ONCE(ssp->srcu_size_state);
+	int ss_state = READ_ONCE(ssp->srcu_sup->srcu_size_state);
 	int ss_state_idx = ss_state;
 
 	idx = ssp->srcu_idx & 0x1;
 	if (ss_state < 0 || ss_state >= ARRAY_SIZE(srcu_size_state_name))
 		ss_state_idx = ARRAY_SIZE(srcu_size_state_name) - 1;
 	pr_alert("%s%s Tree SRCU g%ld state %d (%s)",
-		 tt, tf, rcu_seq_current(&ssp->srcu_gp_seq), ss_state,
+		 tt, tf, rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq), ss_state,
 		 srcu_size_state_name[ss_state_idx]);
 	if (!ssp->sda) {
 		// Called after cleanup_srcu_struct(), perhaps.
···
 
 void __init srcu_init(void)
 {
-	struct srcu_struct *ssp;
+	struct srcu_usage *sup;
 
 	/* Decide on srcu_struct-size strategy. */
 	if (SRCU_SIZING_IS(SRCU_SIZING_AUTO)) {
···
 	 */
 	srcu_init_done = true;
 	while (!list_empty(&srcu_boot_list)) {
-		ssp = list_first_entry(&srcu_boot_list, struct srcu_struct,
+		sup = list_first_entry(&srcu_boot_list, struct srcu_usage,
 				      work.work.entry);
-		list_del_init(&ssp->work.work.entry);
-		if (SRCU_SIZING_IS(SRCU_SIZING_INIT) && ssp->srcu_size_state == SRCU_SIZE_SMALL)
-			ssp->srcu_size_state = SRCU_SIZE_ALLOC;
-		queue_work(rcu_gp_wq, &ssp->work.work);
+		list_del_init(&sup->work.work.entry);
+		if (SRCU_SIZING_IS(SRCU_SIZING_INIT) &&
+		    sup->srcu_size_state == SRCU_SIZE_SMALL)
+			sup->srcu_size_state = SRCU_SIZE_ALLOC;
+		queue_work(rcu_gp_wq, &sup->work.work);
 	}
 }
 
···
 static int srcu_module_coming(struct module *mod)
 {
 	int i;
+	struct srcu_struct *ssp;
 	struct srcu_struct **sspp = mod->srcu_struct_ptrs;
-	int ret;
 
 	for (i = 0; i < mod->num_srcu_structs; i++) {
-		ret = init_srcu_struct(*(sspp++));
-		if (WARN_ON_ONCE(ret))
-			return ret;
+		ssp = *(sspp++);
+		ssp->sda = alloc_percpu(struct srcu_data);
+		if (WARN_ON_ONCE(!ssp->sda))
+			return -ENOMEM;
 	}
 	return 0;
 }
···
 static void srcu_module_going(struct module *mod)
 {
 	int i;
+	struct srcu_struct *ssp;
 	struct srcu_struct **sspp = mod->srcu_struct_ptrs;
 
-	for (i = 0; i < mod->num_srcu_structs; i++)
-		cleanup_srcu_struct(*(sspp++));
+	for (i = 0; i < mod->num_srcu_structs; i++) {
+		ssp = *(sspp++);
+		if (!rcu_seq_state(smp_load_acquire(&ssp->srcu_sup->srcu_gp_seq_needed)) &&
+		    !WARN_ON_ONCE(!ssp->srcu_sup->sda_is_static))
+			cleanup_srcu_struct(ssp);
+		if (!WARN_ON(srcu_readers_active(ssp)))
+			free_percpu(ssp->sda);
+	}
 }
 
 /* Handle one module, either coming or going. */

kernel/rcu/tasks.h

···
 	.kname = #rt_name,								\
 }
 
+#ifdef CONFIG_TASKS_RCU
 /* Track exiting tasks in order to allow them to be waited for. */
 DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
+#endif
+
+#ifdef CONFIG_TASKS_RCU
+/* Report delay in synchronize_srcu() completion in rcu_tasks_postscan(). */
+static void tasks_rcu_exit_srcu_stall(struct timer_list *unused);
+static DEFINE_TIMER(tasks_rcu_exit_srcu_stall_timer, tasks_rcu_exit_srcu_stall);
+#endif
 
 /* Avoid IPIing CPUs early in the grace period. */
 #define RCU_TASK_IPI_DELAY (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) ? HZ / 2 : 0)
···
 /* Processing between scanning taskslist and draining the holdout list. */
 static void rcu_tasks_postscan(struct list_head *hop)
 {
+	int rtsi = READ_ONCE(rcu_task_stall_info);
+
+	if (!IS_ENABLED(CONFIG_TINY_RCU)) {
+		tasks_rcu_exit_srcu_stall_timer.expires = jiffies + rtsi;
+		add_timer(&tasks_rcu_exit_srcu_stall_timer);
+	}
+
 	/*
 	 * Exiting tasks may escape the tasklist scan. Those are vulnerable
 	 * until their final schedule() with TASK_DEAD state. To cope with
···
 	 * call to synchronize_rcu().
 	 */
 	synchronize_srcu(&tasks_rcu_exit_srcu);
+
+	if (!IS_ENABLED(CONFIG_TINY_RCU))
+		del_timer_sync(&tasks_rcu_exit_srcu_stall_timer);
 }
 
 /* See if tasks are still holding out, complain if so. */
···
 
 void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func);
 DEFINE_RCU_TASKS(rcu_tasks, rcu_tasks_wait_gp, call_rcu_tasks, "RCU Tasks");
+
+static void tasks_rcu_exit_srcu_stall(struct timer_list *unused)
+{
+#ifndef CONFIG_TINY_RCU
+	int rtsi;
+
+	rtsi = READ_ONCE(rcu_task_stall_info);
+	pr_info("%s: %s grace period number %lu (since boot) gp_state: %s is %lu jiffies old.\n",
+		__func__, rcu_tasks.kname, rcu_tasks.tasks_gp_seq,
+		tasks_gp_state_getname(&rcu_tasks), jiffies - rcu_tasks.gp_jiffies);
+	pr_info("Please check any exiting tasks stuck between calls to exit_tasks_rcu_start() and exit_tasks_rcu_finish()\n");
+	tasks_rcu_exit_srcu_stall_timer.expires = jiffies + rtsi;
+	add_timer(&tasks_rcu_exit_srcu_stall_timer);
+#endif // #ifndef CONFIG_TINY_RCU
+}
 
 /**
  * call_rcu_tasks() - Queue an RCU for invocation task-based grace period

kernel/rcu/tree.c

···
 	}
 	raw_spin_unlock_rcu_node(rdp->mynode);
 }
+NOKPROBE_SYMBOL(__rcu_irq_enter_check_tick);
 #endif /* CONFIG_NO_HZ_FULL */
 
 /*
···
 {
 	unsigned long flags;
 	unsigned long mask;
-	bool needwake = false;
 	bool needacc = false;
 	struct rcu_node *rnp;
 
···
 		 * NOCB kthreads have their own way to deal with that...
 		 */
 		if (!rcu_rdp_is_offloaded(rdp)) {
-			needwake = rcu_accelerate_cbs(rnp, rdp);
+			/*
+			 * The current GP has not yet ended, so it
+			 * should not be possible for rcu_accelerate_cbs()
+			 * to return true.  So complain, but don't awaken.
+			 */
+			WARN_ON_ONCE(rcu_accelerate_cbs(rnp, rdp));
 		} else if (!rcu_segcblist_completely_offloaded(&rdp->cblist)) {
 			/*
 			 * ...but NOCB kthreads may miss or delay callbacks acceleration
···
 		rcu_disable_urgency_upon_qs(rdp);
 		rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
 		/* ^^^ Released rnp->lock */
-		if (needwake)
-			rcu_gp_kthread_wake();
 
 		if (needacc) {
 			rcu_nocb_lock_irqsave(rdp, flags);
···
 				break;
 			}
 		} else {
+			// In rcuoc context, so no worries about depriving
+			// other softirq vectors of CPU cycles.
 			local_bh_enable();
 			lockdep_assert_irqs_enabled();
 			cond_resched_tasks_rcu_qs();
···
 	else
 		qovld_calc = qovld;
 
-	// Kick-start any polled grace periods that started early.
-	if (!(per_cpu_ptr(&rcu_data, cpu)->mynode->exp_seq_poll_rq & 0x1))
-		(void)start_poll_synchronize_rcu_expedited();
+	// Kick-start in case any polled grace periods started early.
+	(void)start_poll_synchronize_rcu_expedited();
 
 	rcu_test_sync_prims();
 }

kernel/rcu/tree_exp.h

···
 	struct rcu_data *rdp;
 	struct rcu_node *rnp;
 	struct rcu_node *rnp_root = rcu_get_root();
+	unsigned long flags;
 
 	trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("startwait"));
 	jiffies_stall = rcu_exp_jiffies_till_stall_check();
···
 		if (synchronize_rcu_expedited_wait_once(1))
 			return;
 		rcu_for_each_leaf_node(rnp) {
+			raw_spin_lock_irqsave_rcu_node(rnp, flags);
 			mask = READ_ONCE(rnp->expmask);
 			for_each_leaf_node_cpu_mask(rnp, cpu, mask) {
 				rdp = per_cpu_ptr(&rcu_data, cpu);
 				if (rdp->rcu_forced_tick_exp)
 					continue;
 				rdp->rcu_forced_tick_exp = true;
-				preempt_disable();
 				if (cpu_online(cpu))
 					tick_dep_set_cpu(cpu, TICK_DEP_BIT_RCU_EXP);
-				preempt_enable();
 			}
+			raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 		}
 		j = READ_ONCE(jiffies_till_first_fqs);
 		if (synchronize_rcu_expedited_wait_once(j + HZ))
···
 	int ndetected = 0;
 	struct task_struct *t;
 
-	if (!READ_ONCE(rnp->exp_tasks))
-		return 0;
 	raw_spin_lock_irqsave_rcu_node(rnp, flags);
+	if (!rnp->exp_tasks) {
+		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+		return 0;
+	}
 	t = list_entry(rnp->exp_tasks->prev,
 		       struct task_struct, rcu_node_entry);
 	list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
···
 	if (rcu_init_invoked())
 		raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags);
 	if (!poll_state_synchronize_rcu(s)) {
-		rnp->exp_seq_poll_rq = s;
-		if (rcu_init_invoked())
+		if (rcu_init_invoked()) {
+			rnp->exp_seq_poll_rq = s;
 			queue_work(rcu_gp_wq, &rnp->exp_poll_wq);
+		}
 	}
 	if (rcu_init_invoked())
 		raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags);

kernel/rcu/tree_nocb.h

···
 }
 EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
 
+#ifdef CONFIG_RCU_LAZY
 static unsigned long
 lazy_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
 {
···
 	.batch = 0,
 	.seeks = DEFAULT_SEEKS,
 };
+#endif // #ifdef CONFIG_RCU_LAZY
 
 void __init rcu_init_nohz(void)
 {
···
 	if (!rcu_state.nocb_is_setup)
 		return;
 
+#ifdef CONFIG_RCU_LAZY
 	if (register_shrinker(&lazy_rcu_shrinker, "rcu-lazy"))
 		pr_err("Failed to register lazy_rcu shrinker!\n");
+#endif // #ifdef CONFIG_RCU_LAZY
 
 	if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
 		pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");

kernel/time/tick-sched.c

···
 		return true;
 	}
 
+	if (val & TICK_DEP_MASK_RCU_EXP) {
+		trace_tick_stop(0, TICK_DEP_MASK_RCU_EXP);
+		return true;
+	}
+
 	return false;
 }
 
···
 	tick_nohz_full_running = true;
 }
 
-static int tick_nohz_cpu_down(unsigned int cpu)
+bool tick_nohz_cpu_hotpluggable(unsigned int cpu)
 {
 	/*
 	 * The tick_do_timer_cpu CPU handles housekeeping duty (unbound
···
 	 * CPUs. It must remain online when nohz full is enabled.
 	 */
 	if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
-		return -EBUSY;
-	return 0;
+		return false;
+	return true;
+}
+
+static int tick_nohz_cpu_down(unsigned int cpu)
+{
+	return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY;
 }
 
 void __init tick_nohz_init(void)

kernel/trace/trace_osnoise.c

···
 	if (!found)
 		return;
 
-	kvfree_rcu(inst);
+	kvfree_rcu_mightsleep(inst);
 }
 
 /*

kernel/trace/trace_probe.c

···
 		return -ENOENT;
 
 	list_del_rcu(&link->list);
-	kvfree_rcu(link);
+	kvfree_rcu_mightsleep(link);
 
 	if (list_empty(&tp->event->files))
 		trace_probe_clear_flag(tp, TP_FLAG_TRACE);

lib/test_vmalloc.c

···
 			return -1;
 
 		p->array[0] = 'a';
-		kvfree_rcu(p);
+		kvfree_rcu_mightsleep(p);
 	}
 
 	return 0;

mm/Kconfig

···
 
 config MMU_NOTIFIER
 	bool
-	select SRCU
 	select INTERVAL_TREE
 
 config KSM

net/core/sysctl_net_core.c

···
 			if (orig_sock_table) {
 				static_branch_dec(&rps_needed);
 				static_branch_dec(&rfs_needed);
-				kvfree_rcu(orig_sock_table);
+				kvfree_rcu_mightsleep(orig_sock_table);
 			}
 		}
 	}
···
 				     lockdep_is_held(&flow_limit_update_mutex));
 			if (cur && !cpumask_test_cpu(i, mask)) {
 				RCU_INIT_POINTER(sd->flow_limit, NULL);
-				kfree_rcu(cur);
+				kfree_rcu_mightsleep(cur);
 			} else if (!cur && cpumask_test_cpu(i, mask)) {
 				cur = kzalloc_node(len, GFP_KERNEL,
 						   cpu_to_node(i));

net/mac802154/scan.c

···
 	request = rcu_replace_pointer(local->scan_req, NULL, 1);
 	if (!request)
 		return 0;
-	kfree_rcu(request);
+	kvfree_rcu_mightsleep(request);
 
 	/* Advertize first, while we know the devices cannot be removed */
 	if (aborted)
···
 	request = rcu_replace_pointer(local->beacon_req, NULL, 1);
 	if (!request)
 		return 0;
-	kfree_rcu(request);
+	kvfree_rcu_mightsleep(request);
 
 	nl802154_beaconing_done(wpan_dev);
 

scripts/checkpatch.pl

···
 			}
 		}
 
+# check for soon-to-be-deprecated single-argument k[v]free_rcu() API
+		if ($line =~ /\bk[v]?free_rcu\s*\([^(]+\)/) {
+			if ($line =~ /\bk[v]?free_rcu\s*\([^,]+\)/) {
+				ERROR("DEPRECATED_API",
+				      "Single-argument k[v]free_rcu() API is deprecated, please pass rcu_head object or call k[v]free_rcu_mightsleep()." . $herecurr);
+			}
+		}
+
+
 # check for unnecessary "Out of Memory" messages
 		if ($line =~ /^\+.*\b$logFunctions\s*\(/ &&
 		    $prevline =~ /^[ \+]\s*if\s*\(\s*(\!\s*|NULL\s*==\s*)?($Lval)(\s*==\s*NULL\s*)?\s*\)/ &&

tools/rcu/extract-stall.sh

···
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0+
-#
-# Extract any RCU CPU stall warnings present in specified file.
-# Filter out clocksource lines.  Note that preceding-lines excludes the
-# initial line of the stall warning but trailing-lines includes it.
-#
-# Usage: extract-stall.sh dmesg-file [ preceding-lines [ trailing-lines ] ]
+
+usage() {
+	echo Extract any RCU CPU stall warnings present in specified file.
+	echo Filter out clocksource lines.  Note that preceding-lines excludes the
+	echo initial line of the stall warning but trailing-lines includes it.
+	echo
+	echo Usage: $(basename $0) dmesg-file [ preceding-lines [ trailing-lines ] ]
+	echo
+	echo Error: $1
+}
+
+# Terminate the script, if the argument is missing
+
+if test -f "$1" && test -r "$1"
+then
+	:
+else
+	usage "Console log file \"$1\" missing or unreadable."
+	exit 1
+fi
 
 echo $1
 preceding_lines="${2-3}"

tools/testing/selftests/rcutorture/bin/kvm-again.sh

···
 	qemu_cmd_dir="`dirname "$i"`"
 	kernel_dir="`echo $qemu_cmd_dir | sed -e 's/\.[0-9]\+$//'`"
 	jitter_dir="`dirname "$kernel_dir"`"
-	kvm-transform.sh "$kernel_dir/bzImage" "$qemu_cmd_dir/console.log" "$jitter_dir" $dur "$bootargs" < $T/qemu-cmd > $i
+	kvm-transform.sh "$kernel_dir/bzImage" "$qemu_cmd_dir/console.log" "$jitter_dir" "$dur" "$bootargs" < $T/qemu-cmd > $i
 	if test -n "$arg_remote"
 	then
 		echo "# TORTURE_KCONFIG_GDB_ARG=''" >> $i

tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh

···
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Run SRCU-lockdep tests and report any that fail to meet expectations.
+#
+# Copyright (C) 2021 Meta Platforms, Inc.
+#
+# Authors: Paul E. McKenney <[e-mail]>
+
+usage () {
+	echo "Usage: $scriptname optional arguments:"
+	echo "       --datestamp string"
+	exit 1
+}
+
+ds=`date +%Y.%m.%d-%H.%M.%S`-srcu_lockdep
+scriptname="$0"
+
+T="`mktemp -d ${TMPDIR-/tmp}/srcu_lockdep.sh.XXXXXX`"
+trap 'rm -rf $T' 0
+
+RCUTORTURE="`pwd`/tools/testing/selftests/rcutorture"; export RCUTORTURE
+PATH=${RCUTORTURE}/bin:$PATH; export PATH
+. functions.sh
+
+while test $# -gt 0
+do
+	case "$1" in
+	--datestamp)
+		checkarg --datestamp "(relative pathname)" "$#" "$2" '^[a-zA-Z0-9._/-]*$' '^--'
+		ds=$2
+		shift
+		;;
+	*)
+		echo Unknown argument $1
+		usage
+		;;
+	esac
+	shift
+done
+
+err=
+nerrs=0
+for d in 0 1
+do
+	for t in 0 1 2
+	do
+		for c in 1 2 3
+		do
+			err=
+			val=$((d*1000+t*10+c))
+			tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 5s --configs "SRCU-P" --bootargs "rcutorture.test_srcu_lockdep=$val" --trust-make --datestamp "$ds/$val" > "$T/kvm.sh.out" 2>&1
+			ret=$?
+			mv "$T/kvm.sh.out" "$RCUTORTURE/res/$ds/$val"
+			if test "$d" -ne 0 && test "$ret" -eq 0
+			then
+				err=1
+				echo -n Unexpected success for > "$RCUTORTURE/res/$ds/$val/kvm.sh.err"
+			fi
+			if test "$d" -eq 0 && test "$ret" -ne 0
+			then
+				err=1
+				echo -n Unexpected failure for > "$RCUTORTURE/res/$ds/$val/kvm.sh.err"
+			fi
+			if test -n "$err"
+			then
+				grep "rcu_torture_init_srcu_lockdep: test_srcu_lockdep = " "$RCUTORTURE/res/$ds/$val/SRCU-P/console.log" | sed -e 's/^.*rcu_torture_init_srcu_lockdep://' >> "$RCUTORTURE/res/$ds/$val/kvm.sh.err"
+				cat "$RCUTORTURE/res/$ds/$val/kvm.sh.err"
+				nerrs=$((nerrs+1))
+			fi
+		done
+	done
+done
+if test "$nerrs" -ne 0
+then
+	exit 1
+fi
+exit 0

tools/testing/selftests/rcutorture/bin/torture.sh

···
 
 if test "$do_clocksourcewd" = "yes"
 then
-	torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000"
+	torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 tsc=watchdog"
 	torture_set "clocksourcewd-1" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 45s --configs TREE03 --kconfig "CONFIG_TEST_CLOCKSOURCE_WATCHDOG=y" --trust-make
 
-	torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 clocksource.max_cswd_read_retries=1"
+	torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 clocksource.max_cswd_read_retries=1 tsc=watchdog"
 	torture_set "clocksourcewd-2" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 45s --configs TREE03 --kconfig "CONFIG_TEST_CLOCKSOURCE_WATCHDOG=y" --trust-make
 
 	# In case our work is already done...
 	if test "$do_rcutorture" != "yes"
 	then
-		torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000"
+		torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 tsc=watchdog"
 		torture_set "clocksourcewd-3" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 45s --configs TREE03 --trust-make
 	fi
 fi

tools/testing/selftests/rcutorture/configs/rcu/TREE01

···
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
+CONFIG_BOOTPARAM_HOTPLUG_CPU0=y

tools/testing/selftests/rcutorture/configs/rcu/TREE04

···
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
 CONFIG_RCU_EQS_DEBUG=y
+CONFIG_RCU_LAZY=y

tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt

···
 
 	These are controlled by CONFIG_PREEMPT and/or CONFIG_SMP.
 
-CONFIG_SRCU
-
-	Selected by CONFIG_RCU_TORTURE_TEST, so cannot disable.
-
 
 boot parameters ignored: TBD