Merge LKMM and RCU commits

49 files changed, 736 insertions, 431 deletions

diff --git a/Documentation/RCU/rcuref.txt b/Documentation/RCU/rcuref.txt
index 613033ff2b9b..5e6429d66c24 100644
--- a/Documentation/RCU/rcuref.txt
+++ b/Documentation/RCU/rcuref.txt
@@ -12,6 +12,7 @@ please read on.
 Reference counting on elements of lists which are protected by traditional
 reader/writer spinlocks or semaphores are straightforward:
 
+CODE LISTING A:
 1.				2.
 add()				search_and_reference()
 {				{
@@ -28,7 +29,8 @@ add()				search_and_reference()
 release_referenced()			delete()
 {					{
     ...					    write_lock(&list_lock);
-    atomic_dec(&el->rc, relfunc)	    ...
+    if(atomic_dec_and_test(&el->rc))	    ...
+	kfree(el);
     ...					    remove_element
 }					    write_unlock(&list_lock);
  					    ...
@@ -44,6 +46,7 @@ search_and_reference() could potentially hold reference to an element which
 has already been deleted from the list/array.  Use atomic_inc_not_zero()
 in this scenario as follows:
 
+CODE LISTING B:
 1.					2.
 add()					search_and_reference()
 {					{
@@ -79,6 +82,7 @@ search_and_reference() code path.  In such cases, the
 atomic_dec_and_test() may be moved from delete() to el_free()
 as follows:
 
+CODE LISTING C:
 1.					2.
 add()					search_and_reference()
 {					{
@@ -114,6 +118,17 @@ element can therefore safely be freed.  This in turn guarantees that if
 any reader finds the element, that reader may safely acquire a reference
 without checking the value of the reference counter.
 
+A clear advantage of the RCU-based pattern in listing C over the one
+in listing B is that any call to search_and_reference() that locates
+a given object will succeed in obtaining a reference to that object,
+even given a concurrent invocation of delete() for that same object.
+Similarly, a clear advantage of both listings B and C over listing A is
+that a call to delete() is not delayed even if there are an arbitrarily
+large number of calls to search_and_reference() searching for the same
+object that delete() was invoked on.  Instead, all that is delayed is
+the eventual invocation of kfree(), which is usually not a problem on
+modern computer systems, even the small ones.
+
 In cases where delete() can sleep, synchronize_rcu() can be called from
 delete(), so that el_free() can be subsumed into delete as follows:
 
@@ -130,3 +145,7 @@ delete()
     	kfree(el);
     ...
 }
+
+As additional examples in the kernel, the pattern in listing C is used by
+reference counting of struct pid, while the pattern in listing B is used by
+struct posix_acl.
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index 1ab70c37921f..13e88fc00f01 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -153,7 +153,7 @@ rcupdate.rcu_task_stall_timeout
 	This boot/sysfs parameter controls the RCU-tasks stall warning
 	interval.  A value of zero or less suppresses RCU-tasks stall
 	warnings.  A positive value sets the stall-warning interval
-	in jiffies.  An RCU-tasks stall warning starts with the line:
+	in seconds.  An RCU-tasks stall warning starts with the line:
 
 		INFO: rcu_tasks detected stalls on tasks:
 
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index 981651a8b65d..7e1a8721637a 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -212,7 +212,7 @@ synchronize_rcu()
 
 rcu_assign_pointer()
 
-	typeof(p) rcu_assign_pointer(p, typeof(p) v);
+	void rcu_assign_pointer(p, typeof(p) v);
 
 	Yes, rcu_assign_pointer() -is- implemented as a macro, though it
 	would be cool to be able to declare a function in this manner.
@@ -220,9 +220,9 @@ rcu_assign_pointer()
 
 	The updater uses this function to assign a new value to an
 	RCU-protected pointer, in order to safely communicate the change
-	in value from the updater to the reader.  This function returns
-	the new value, and also executes any memory-barrier instructions
-	required for a given CPU architecture.
+	in value from the updater to the reader.  This macro does not
+	evaluate to an rvalue, but it does execute any memory-barrier
+	instructions required for a given CPU architecture.
 
 	Perhaps just as important, it serves to document (1) which
 	pointers are protected by RCU and (2) the point at which a
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 138f6664b2e2..b96fd15c7316 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3752,6 +3752,12 @@
 			the propagation of recent CPU-hotplug changes up
 			the rcu_node combining tree.
 
+	rcutree.use_softirq=	[KNL]
+			If set to zero, move all RCU_SOFTIRQ processing to
+			per-CPU rcuc kthreads.  Defaults to a non-zero
+			value, meaning that RCU_SOFTIRQ is used by default.
+			Specify rcutree.use_softirq=0 to use rcuc kthreads.
+
 	rcutree.rcu_fanout_exact= [KNL]
 			Disable autobalancing of the rcu_node combining
 			tree.  This is used by rcutorture, and might
diff --git a/Documentation/core-api/circular-buffers.rst b/Documentation/core-api/circular-buffers.rst
index 53e51caa3347..50966f66e398 100644
--- a/Documentation/core-api/circular-buffers.rst
+++ b/Documentation/core-api/circular-buffers.rst
@@ -3,7 +3,7 @@ Circular Buffers
 ================
 
 :Author: David Howells <dhowells@redhat.com>
-:Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+:Author: Paul E. McKenney <paulmck@linux.ibm.com>
 
 
 Linux provides a number of features that can be used to implement circular
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index f70ebcdfe592..e4e07c8ab89e 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -3,7 +3,7 @@
 			 ============================
 
 By: David Howells <dhowells@redhat.com>
-    Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+    Paul E. McKenney <paulmck@linux.ibm.com>
     Will Deacon <will.deacon@arm.com>
     Peter Zijlstra <peterz@infradead.org>
 
diff --git a/Documentation/translations/ko_KR/memory-barriers.txt b/Documentation/translations/ko_KR/memory-barriers.txt
index db0b9d8619f1..5f3c74dcad43 100644
--- a/Documentation/translations/ko_KR/memory-barriers.txt
+++ b/Documentation/translations/ko_KR/memory-barriers.txt
@@ -24,7 +24,7 @@ Documentation/memory-barriers.txt
 			 =========================
 
 저자: David Howells <dhowells@redhat.com>
-      Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+      Paul E. McKenney <paulmck@linux.ibm.com>
       Will Deacon <will.deacon@arm.com>
       Peter Zijlstra <peterz@infradead.org>
 
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 6e2377e6c1d6..e8eef38b2213 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -632,11 +632,18 @@ do {									\
 			  "IRQs not disabled as expected\n");		\
 	} while (0)
 
+#define lockdep_assert_in_irq() do {					\
+		WARN_ONCE(debug_locks && !current->lockdep_recursion &&	\
+			  !current->hardirq_context,			\
+			  "Not in hardirq as expected\n");		\
+	} while (0)
+
 #else
 # define might_lock(lock) do { } while (0)
 # define might_lock_read(lock) do { } while (0)
 # define lockdep_assert_irqs_enabled() do { } while (0)
 # define lockdep_assert_irqs_disabled() do { } while (0)
+# define lockdep_assert_in_irq() do { } while (0)
 #endif
 
 #ifdef CONFIG_LOCKDEP
diff --git a/include/linux/module.h b/include/linux/module.h
index 188998d3dca9..1455812dd325 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -21,6 +21,7 @@
 #include <linux/rbtree_latch.h>
 #include <linux/error-injection.h>
 #include <linux/tracepoint-defs.h>
+#include <linux/srcu.h>
 
 #include <linux/percpu.h>
 #include <asm/module.h>
@@ -450,6 +451,10 @@ struct module {
 	unsigned int num_tracepoints;
 	tracepoint_ptr_t *tracepoints_ptrs;
 #endif
+#ifdef CONFIG_TREE_SRCU
+	unsigned int num_srcu_structs;
+	struct srcu_struct **srcu_struct_ptrs;
+#endif
 #ifdef CONFIG_BPF_EVENTS
 	unsigned int num_bpf_raw_events;
 	struct bpf_raw_event_map *bpf_raw_events;
diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index 03cb4b6f842e..2809b44cbbee 100644
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -17,14 +17,18 @@ struct percpu_rw_semaphore {
 	int			readers_block;
 };
 
-#define DEFINE_STATIC_PERCPU_RWSEM(name)				\
+#define __DEFINE_PERCPU_RWSEM(name, is_static)				\
 static DEFINE_PER_CPU(unsigned int, __percpu_rwsem_rc_##name);		\
-static struct percpu_rw_semaphore name = {				\
-	.rss = __RCU_SYNC_INITIALIZER(name.rss, RCU_SCHED_SYNC),	\
+is_static struct percpu_rw_semaphore name = {				\
+	.rss = __RCU_SYNC_INITIALIZER(name.rss),			\
 	.read_count = &__percpu_rwsem_rc_##name,			\
 	.rw_sem = __RWSEM_INITIALIZER(name.rw_sem),			\
 	.writer = __RCUWAIT_INITIALIZER(name.writer),			\
 }
+#define DEFINE_PERCPU_RWSEM(name)		\
+	__DEFINE_PERCPU_RWSEM(name, /* not static */)
+#define DEFINE_STATIC_PERCPU_RWSEM(name)	\
+	__DEFINE_PERCPU_RWSEM(name, static)
 
 extern int __percpu_down_read(struct percpu_rw_semaphore *, int);
 extern void __percpu_up_read(struct percpu_rw_semaphore *);
diff --git a/include/linux/rcu_sync.h b/include/linux/rcu_sync.h
index 6fc53a1345b3..9b83865d24f9 100644
--- a/include/linux/rcu_sync.h
+++ b/include/linux/rcu_sync.h
@@ -13,62 +13,44 @@
 #include <linux/wait.h>
 #include <linux/rcupdate.h>
 
-enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
-
 /* Structure to mediate between updaters and fastpath-using readers.  */
 struct rcu_sync {
 	int			gp_state;
 	int			gp_count;
 	wait_queue_head_t	gp_wait;
 
-	int			cb_state;
 	struct rcu_head		cb_head;
-
-	enum rcu_sync_type	gp_type;
 };
 
-extern void rcu_sync_lockdep_assert(struct rcu_sync *);
-
 /**
  * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
  * @rsp: Pointer to rcu_sync structure to use for synchronization
  *
- * Returns true if readers are permitted to use their fastpaths.
- * Must be invoked within an RCU read-side critical section whose
- * flavor matches that of the rcu_sync struture.
+ * Returns true if readers are permitted to use their fastpaths.  Must be
+ * invoked within some flavor of RCU read-side critical section.
  */
 static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
 {
-#ifdef CONFIG_PROVE_RCU
-	rcu_sync_lockdep_assert(rsp);
-#endif
-	return !rsp->gp_state; /* GP_IDLE */
+	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
+			 !rcu_read_lock_bh_held() &&
+			 !rcu_read_lock_sched_held(),
+			 "suspicious rcu_sync_is_idle() usage");
+	return !READ_ONCE(rsp->gp_state); /* GP_IDLE */
 }
 
-extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
+extern void rcu_sync_init(struct rcu_sync *);
 extern void rcu_sync_enter_start(struct rcu_sync *);
 extern void rcu_sync_enter(struct rcu_sync *);
 extern void rcu_sync_exit(struct rcu_sync *);
 extern void rcu_sync_dtor(struct rcu_sync *);
 
-#define __RCU_SYNC_INITIALIZER(name, type) {				\
+#define __RCU_SYNC_INITIALIZER(name) {					\
 		.gp_state = 0,						\
 		.gp_count = 0,						\
 		.gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait),	\
-		.cb_state = 0,						\
-		.gp_type = type,					\
 	}
 
-#define	__DEFINE_RCU_SYNC(name, type)	\
-	struct rcu_sync_struct name = __RCU_SYNC_INITIALIZER(name, type)
-
-#define DEFINE_RCU_SYNC(name)		\
-	__DEFINE_RCU_SYNC(name, RCU_SYNC)
-
-#define DEFINE_RCU_SCHED_SYNC(name)	\
-	__DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC)
-
-#define DEFINE_RCU_BH_SYNC(name)	\
-	__DEFINE_RCU_SYNC(name, RCU_BH_SYNC)
+#define	DEFINE_RCU_SYNC(name)	\
+	struct rcu_sync name = __RCU_SYNC_INITIALIZER(name)
 
 #endif /* _LINUX_RCU_SYNC_H_ */
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 922bb6848813..0c9b92799abc 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -367,16 +367,15 @@ static inline void rcu_preempt_sleep_check(void) { }
  * other macros that it invokes.
  */
 #define rcu_assign_pointer(p, v)					      \
-({									      \
+do {									      \
 	uintptr_t _r_a_p__v = (uintptr_t)(v);				      \
-	rcu_check_sparse(p, __rcu);				      \
+	rcu_check_sparse(p, __rcu);					      \
 									      \
 	if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL)	      \
 		WRITE_ONCE((p), (typeof(p))(_r_a_p__v));		      \
 	else								      \
 		smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \
-	_r_a_p__v;							      \
-})
+} while (0)
 
 /**
  * rcu_swap_protected() - swap an RCU and a regular pointer
@@ -588,7 +587,7 @@ static inline void rcu_preempt_sleep_check(void) { }
  * read-side critical sections may be preempted and they may also block, but
  * only when acquiring spinlocks that are subject to priority inheritance.
  */
-static inline void rcu_read_lock(void)
+static __always_inline void rcu_read_lock(void)
 {
 	__rcu_read_lock();
 	__acquire(RCU);
@@ -805,7 +804,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
 /**
  * kfree_rcu() - kfree an object after a grace period.
  * @ptr:	pointer to kfree
- * @rcu_head:	the name of the struct rcu_head within the type of @ptr.
+ * @rhf:	the name of the struct rcu_head within the type of @ptr.
  *
  * Many rcu callbacks functions just call kfree() on the base structure.
  * These functions are trivial, but their size adds up, and furthermore
@@ -828,9 +827,13 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
  * The BUILD_BUG_ON check must not involve any function calls, hence the
  * checks are done in macros here.
  */
-#define kfree_rcu(ptr, rcu_head)					\
-	__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
-
+#define kfree_rcu(ptr, rhf)						\
+do {									\
+	typeof (ptr) ___p = (ptr);					\
+									\
+	if (___p)							\
+		__kfree_rcu(&((___p)->rhf), offsetof(typeof(*(ptr)), rhf)); \
+} while (0)
 
 /*
  * Place this after a lock-acquisition primitive to guarantee that
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 11837410690f..942a44c1b8eb 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -565,7 +565,7 @@ union rcu_special {
 		u8			blocked;
 		u8			need_qs;
 		u8			exp_hint; /* Hint for performance. */
-		u8			pad; /* No garbage from compiler! */
+		u8			deferred_qs;
 	} b; /* Bits. */
 	u32 s; /* Set of bits. */
 };
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 7f7c8c050f63..9cfcc8a756ae 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -120,9 +120,17 @@ struct srcu_struct {
  *
  * See include/linux/percpu-defs.h for the rules on per-CPU variables.
  */
-#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)
+#ifdef MODULE
+# define __DEFINE_SRCU(name, is_static)					\
+	is_static struct 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)
+#endif
 #define DEFINE_SRCU(name)		__DEFINE_SRCU(name, /* not static */)
 #define DEFINE_STATIC_SRCU(name)	__DEFINE_SRCU(name, static)
 
diff --git a/include/linux/torture.h b/include/linux/torture.h
index 23d80db426d7..a620118385bb 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -66,7 +66,7 @@ int torture_shutdown_init(int ssecs, void (*cleanup)(void));
 
 /* Task stuttering, which forces load/no-load transitions. */
 bool stutter_wait(const char *title);
-int torture_stutter_init(int s);
+int torture_stutter_init(int s, int sgap);
 
 /* Initialization and cleanup. */
 bool torture_init_begin(char *ttype, int v);
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 217cec4e22c6..b112e93388dc 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -101,7 +101,7 @@ static DEFINE_SPINLOCK(cgroup_idr_lock);
  */
 static DEFINE_SPINLOCK(cgroup_file_kn_lock);
 
-struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
+DEFINE_PERCPU_RWSEM(cgroup_threadgroup_rwsem);
 
 #define cgroup_assert_mutex_or_rcu_locked()				\
 	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
@@ -5616,7 +5616,6 @@ int __init cgroup_init(void)
 	int ssid;
 
 	BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
-	BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem));
 	BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
 	BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
 
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 78f61bfc6b79..97c367f0a9aa 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -46,7 +46,7 @@ static DEFINE_SPINLOCK(uprobes_treelock);	/* serialize rbtree access */
 static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
 #define uprobes_mmap_hash(v)	(&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
 
-static struct percpu_rw_semaphore dup_mmap_sem;
+DEFINE_STATIC_PERCPU_RWSEM(dup_mmap_sem);
 
 /* Have a copy of original instruction */
 #define UPROBE_COPY_INSN	0
@@ -2302,7 +2302,5 @@ void __init uprobes_init(void)
 	for (i = 0; i < UPROBES_HASH_SZ; i++)
 		mutex_init(&uprobes_mmap_mutex[i]);
 
-	BUG_ON(percpu_init_rwsem(&dup_mmap_sem));
-
 	BUG_ON(register_die_notifier(&uprobe_exception_nb));
 }
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 80a463d31a8d..c513031cd7e3 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -975,7 +975,7 @@ static int __init lock_torture_init(void)
 			goto unwind;
 	}
 	if (stutter > 0) {
-		firsterr = torture_stutter_init(stutter);
+		firsterr = torture_stutter_init(stutter, stutter);
 		if (firsterr)
 			goto unwind;
 	}
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index f17dad99eec8..48cab93a47fd 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -17,7 +17,7 @@ int __percpu_init_rwsem(struct percpu_rw_semaphore *sem,
 		return -ENOMEM;
 
 	/* ->rw_sem represents the whole percpu_rw_semaphore for lockdep */
-	rcu_sync_init(&sem->rss, RCU_SCHED_SYNC);
+	rcu_sync_init(&sem->rss);
 	__init_rwsem(&sem->rw_sem, name, rwsem_key);
 	rcuwait_init(&sem->writer);
 	sem->readers_block = 0;
diff --git a/kernel/module.c b/kernel/module.c
index 6e6712b3aaf5..c79a53b629b6 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3095,6 +3095,11 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 					     sizeof(*mod->tracepoints_ptrs),
 					     &mod->num_tracepoints);
 #endif
+#ifdef CONFIG_TREE_SRCU
+	mod->srcu_struct_ptrs = section_objs(info, "___srcu_struct_ptrs",
+					     sizeof(*mod->srcu_struct_ptrs),
+					     &mod->num_srcu_structs);
+#endif
 #ifdef CONFIG_BPF_EVENTS
 	mod->bpf_raw_events = section_objs(info, "__bpf_raw_tp_map",
 					   sizeof(*mod->bpf_raw_events),
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 390aab20115e..5290b01de534 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -446,6 +446,7 @@ void rcu_request_urgent_qs_task(struct task_struct *t);
 enum rcutorture_type {
 	RCU_FLAVOR,
 	RCU_TASKS_FLAVOR,
+	RCU_TRIVIAL_FLAVOR,
 	SRCU_FLAVOR,
 	INVALID_RCU_FLAVOR
 };
@@ -479,6 +480,10 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 #endif
 #endif
 
+#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
+long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask);
+#endif
+
 #ifdef CONFIG_TINY_SRCU
 
 static inline void srcutorture_get_gp_data(enum rcutorture_type test_type,
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index efaa5b3f4d3f..fce4e7e6f502 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -299,6 +299,7 @@ struct rcu_torture_ops {
 	int irq_capable;
 	int can_boost;
 	int extendables;
+	int slow_gps;
 	const char *name;
 };
 
@@ -667,9 +668,51 @@ static struct rcu_torture_ops tasks_ops = {
 	.fqs		= NULL,
 	.stats		= NULL,
 	.irq_capable	= 1,
+	.slow_gps	= 1,
 	.name		= "tasks"
 };
 
+/*
+ * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
+ * This implementation does not necessarily work well with CPU hotplug.
+ */
+
+static void synchronize_rcu_trivial(void)
+{
+	int cpu;
+
+	for_each_online_cpu(cpu) {
+		rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
+		WARN_ON_ONCE(raw_smp_processor_id() != cpu);
+	}
+}
+
+static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
+{
+	preempt_disable();
+	return 0;
+}
+
+static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
+{
+	preempt_enable();
+}
+
+static struct rcu_torture_ops trivial_ops = {
+	.ttype		= RCU_TRIVIAL_FLAVOR,
+	.init		= rcu_sync_torture_init,
+	.readlock	= rcu_tort