Merge branches 'doc.2018.08.30a', 'dynticks.2018.08.30b', 'srcu.2018.08.30b' and 'torture.2018.08.29a' into HEAD

doc.2018.08.30a: Documentation updates
dynticks.2018.08.30b: RCU flavor consolidation updates and cleanups
srcu.2018.08.30b: SRCU updates
torture.2018.08.29a: Torture-test updates

Documentation/RCU/Design/Requirements/Requirements.html

@@ -2398,30 +2398,9 @@ when invoked from a CPU-hotplug notifier.
 <p>
 RCU depends on the scheduler, and the scheduler uses RCU to
 protect some of its data structures.
-This means the scheduler is forbidden from acquiring
+The preemptible-RCU <tt>rcu_read_unlock()</tt>
-the runqueue locks and the priority-inheritance locks
+implementation must therefore be written carefully to avoid deadlocks
-in the middle of an outermost RCU read-side critical section unless either
+involving the scheduler's runqueue and priority-inheritance locks.
-(1)&nbsp;it releases them before exiting that same
-RCU read-side critical section, or
-(2)&nbsp;interrupts are disabled across
-that entire RCU read-side critical section.
-This same prohibition also applies (recursively!) to any lock that is acquired
-while holding any lock to which this prohibition applies.
-Adhering to this rule prevents preemptible RCU from invoking
-<tt>rcu_read_unlock_special()</tt> while either runqueue or
-priority-inheritance locks are held, thus avoiding deadlock.
-
-<p>
-Prior to v4.4, it was only necessary to disable preemption across
-RCU read-side critical sections that acquired scheduler locks.
-In v4.4, expedited grace periods started using IPIs, and these
-IPIs could force a <tt>rcu_read_unlock()</tt> to take the slowpath.
-Therefore, this expedited-grace-period change required disabling of
-interrupts, not just preemption.
-
-<p>
-For RCU's part, the preemptible-RCU <tt>rcu_read_unlock()</tt>
-implementation must be written carefully to avoid similar deadlocks.
 In particular, <tt>rcu_read_unlock()</tt> must tolerate an
 interrupt where the interrupt handler invokes both
 <tt>rcu_read_lock()</tt> and <tt>rcu_read_unlock()</tt>.
@@ -2430,7 +2409,7 @@ negative nesting levels to avoid destructive recursion via
 interrupt handler's use of RCU.
 
 <p>
-This pair of mutual scheduler-RCU requirements came as a
+This scheduler-RCU requirement came as a
 <a href="https://lwn.net/Articles/453002/">complete surprise</a>.
 
 <p>
@@ -2441,9 +2420,28 @@ when running context-switch-heavy workloads when built with
 <tt>CONFIG_NO_HZ_FULL=y</tt>
 <a href="http://www.rdrop.com/users/paulmck/scalability/paper/BareMetal.2015.01.15b.pdf">did come as a surprise [PDF]</a>.
 RCU has made good progress towards meeting this requirement, even
-for context-switch-have <tt>CONFIG_NO_HZ_FULL=y</tt> workloads,
+for context-switch-heavy <tt>CONFIG_NO_HZ_FULL=y</tt> workloads,
 but there is room for further improvement.
 
+<p>
+In the past, it was forbidden to disable interrupts across an
+<tt>rcu_read_unlock()</tt> unless that interrupt-disabled region
+of code also included the matching <tt>rcu_read_lock()</tt>.
+Violating this restriction could result in deadlocks involving the
+scheduler's runqueue and priority-inheritance spinlocks.
+This restriction was lifted when interrupt-disabled calls to
+<tt>rcu_read_unlock()</tt> started deferring the reporting of
+the resulting RCU-preempt quiescent state until the end of that
+interrupts-disabled region.
+This deferred reporting means that the scheduler's runqueue and
+priority-inheritance locks cannot be held while reporting an RCU-preempt
+quiescent state, which lifts the earlier restriction, at least from
+a deadlock perspective.
+Unfortunately, real-time systems using RCU priority boosting may
+need this restriction to remain in effect because deferred
+quiescent-state reporting also defers deboosting, which in turn
+degrades real-time latencies.
+
 <h3><a name="Tracing and RCU">Tracing and RCU</a></h3>
 
 <p>

Documentation/admin-guide/kernel-parameters.txt

@@ -3595,7 +3595,14 @@
 			Set required age in jiffies for a
 			given grace period before RCU starts
 			soliciting quiescent-state help from
-			rcu_note_context_switch().
+			rcu_note_context_switch().  If not specified, the
+			kernel will calculate a value based on the most
+			recent settings of rcutree.jiffies_till_first_fqs
+			and rcutree.jiffies_till_next_fqs.
+			This calculated value may be viewed in
+			rcutree.jiffies_to_sched_qs.  Any attempt to
+			set rcutree.jiffies_to_sched_qs will be
+			cheerfully overwritten.
 
 	rcutree.jiffies_till_first_fqs= [KNL]
 			Set delay from grace-period initialization to
@@ -3863,12 +3870,6 @@
 	rcupdate.rcu_self_test= [KNL]
 			Run the RCU early boot self tests
 
-	rcupdate.rcu_self_test_bh= [KNL]
-			Run the RCU bh early boot self tests
-
-	rcupdate.rcu_self_test_sched= [KNL]
-			Run the RCU sched early boot self tests
-
 	rdinit=		[KNL]
 			Format: <full_path>
 			Run specified binary instead of /init from the ramdisk,

include/linux/rculist.h

@@ -182,7 +182,7 @@ static inline void list_replace_rcu(struct list_head *old,
  * @list:	the RCU-protected list to splice
  * @prev:	points to the last element of the existing list
  * @next:	points to the first element of the existing list
- * @sync:	function to sync: synchronize_rcu(), synchronize_sched(), ...
+ * @sync:	synchronize_rcu, synchronize_rcu_expedited, ...
  *
  * The list pointed to by @prev and @next can be RCU-read traversed
  * concurrently with this function.
@@ -240,7 +240,7 @@ static inline void __list_splice_init_rcu(struct list_head *list,
  *                        designed for stacks.
  * @list:	the RCU-protected list to splice
  * @head:	the place in the existing list to splice the first list into
- * @sync:	function to sync: synchronize_rcu(), synchronize_sched(), ...
+ * @sync:	synchronize_rcu, synchronize_rcu_expedited, ...
  */
 static inline void list_splice_init_rcu(struct list_head *list,
 					struct list_head *head,
@@ -255,7 +255,7 @@ static inline void list_splice_init_rcu(struct list_head *list,
  *                             list, designed for queues.
  * @list:	the RCU-protected list to splice
  * @head:	the place in the existing list to splice the first list into
- * @sync:	function to sync: synchronize_rcu(), synchronize_sched(), ...
+ * @sync:	synchronize_rcu, synchronize_rcu_expedited, ...
  */
 static inline void list_splice_tail_init_rcu(struct list_head *list,
 					     struct list_head *head,
@@ -359,13 +359,12 @@ static inline void list_splice_tail_init_rcu(struct list_head *list,
  * @type:       the type of the struct this is embedded in.
  * @member:     the name of the list_head within the struct.
  *
- * This primitive may safely run concurrently with the _rcu list-mutation
+ * This primitive may safely run concurrently with the _rcu
- * primitives such as list_add_rcu(), but requires some implicit RCU
+ * list-mutation primitives such as list_add_rcu(), but requires some
- * read-side guarding.  One example is running within a special
+ * implicit RCU read-side guarding.  One example is running within a special
- * exception-time environment where preemption is disabled and where
+ * exception-time environment where preemption is disabled and where lockdep
- * lockdep cannot be invoked (in which case updaters must use RCU-sched,
+ * cannot be invoked.  Another example is when items are added to the list,
- * as in synchronize_sched(), call_rcu_sched(), and friends).  Another
+ * but never deleted.
- * example is when items are added to the list, but never deleted.
  */
 #define list_entry_lockless(ptr, type, member) \
 	container_of((typeof(ptr))READ_ONCE(ptr), type, member)
@@ -376,13 +375,12 @@ static inline void list_splice_tail_init_rcu(struct list_head *list,
  * @head:	the head for your list.
  * @member:	the name of the list_struct within the struct.
  *
- * This primitive may safely run concurrently with the _rcu list-mutation
+ * This primitive may safely run concurrently with the _rcu
- * primitives such as list_add_rcu(), but requires some implicit RCU
+ * list-mutation primitives such as list_add_rcu(), but requires some
- * read-side guarding.  One example is running within a special
+ * implicit RCU read-side guarding.  One example is running within a special
- * exception-time environment where preemption is disabled and where
+ * exception-time environment where preemption is disabled and where lockdep
- * lockdep cannot be invoked (in which case updaters must use RCU-sched,
+ * cannot be invoked.  Another example is when items are added to the list,
- * as in synchronize_sched(), call_rcu_sched(), and friends).  Another
+ * but never deleted.
- * example is when items are added to the list, but never deleted.
  */
 #define list_for_each_entry_lockless(pos, head, member) \
 	for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \

include/linux/rcupdate.h

@@ -48,23 +48,14 @@
 #define ulong2long(a)		(*(long *)(&(a)))
 
 /* Exported common interfaces */
-
-#ifdef CONFIG_PREEMPT_RCU
 void call_rcu(struct rcu_head *head, rcu_callback_t func);
-#else /* #ifdef CONFIG_PREEMPT_RCU */
-#define	call_rcu	call_rcu_sched
-#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
-
-void call_rcu_bh(struct rcu_head *head, rcu_callback_t func);
-void call_rcu_sched(struct rcu_head *head, rcu_callback_t func);
-void synchronize_sched(void);
 void rcu_barrier_tasks(void);
+void synchronize_rcu(void);
 
 #ifdef CONFIG_PREEMPT_RCU
 
 void __rcu_read_lock(void);
 void __rcu_read_unlock(void);
-void synchronize_rcu(void);
 
 /*
  * Defined as a macro as it is a very low level header included from
@@ -88,11 +79,6 @@ static inline void __rcu_read_unlock(void)
 		preempt_enable();
 }
 
-static inline void synchronize_rcu(void)
-{
-	synchronize_sched();
-}
-
 static inline int rcu_preempt_depth(void)
 {
 	return 0;
@@ -103,8 +89,6 @@ static inline int rcu_preempt_depth(void)
 /* Internal to kernel */
 void rcu_init(void);
 extern int rcu_scheduler_active __read_mostly;
-void rcu_sched_qs(void);
-void rcu_bh_qs(void);
 void rcu_check_callbacks(int user);
 void rcu_report_dead(unsigned int cpu);
 void rcutree_migrate_callbacks(int cpu);
@@ -135,11 +119,10 @@ static inline void rcu_init_nohz(void) { }
  * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers
  * @a: Code that RCU needs to pay attention to.
  *
- * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden
+ * RCU read-side critical sections are forbidden in the inner idle loop,
- * in the inner idle loop, that is, between the rcu_idle_enter() and
+ * that is, between the rcu_idle_enter() and the rcu_idle_exit() -- RCU
- * the rcu_idle_exit() -- RCU will happily ignore any such read-side
+ * will happily ignore any such read-side critical sections.  However,
- * critical sections.  However, things like powertop need tracepoints
+ * things like powertop need tracepoints in the inner idle loop.
- * in the inner idle loop.
  *
  * This macro provides the way out:  RCU_NONIDLE(do_something_with_RCU())
  * will tell RCU that it needs to pay attention, invoke its argument
@@ -167,20 +150,16 @@ static inline void rcu_init_nohz(void) { }
 		if (READ_ONCE((t)->rcu_tasks_holdout)) \
 			WRITE_ONCE((t)->rcu_tasks_holdout, false); \
 	} while (0)
-#define rcu_note_voluntary_context_switch(t) \
+#define rcu_note_voluntary_context_switch(t) rcu_tasks_qs(t)
-	do { \
-		rcu_all_qs(); \
-		rcu_tasks_qs(t); \
-	} while (0)
 void call_rcu_tasks(struct rcu_head *head, rcu_callback_t func);
 void synchronize_rcu_tasks(void);
 void exit_tasks_rcu_start(void);
 void exit_tasks_rcu_finish(void);
 #else /* #ifdef CONFIG_TASKS_RCU */
 #define rcu_tasks_qs(t)	do { } while (0)
-#define rcu_note_voluntary_context_switch(t)		rcu_all_qs()
+#define rcu_note_voluntary_context_switch(t) do { } while (0)
-#define call_rcu_tasks call_rcu_sched
+#define call_rcu_tasks call_rcu
-#define synchronize_rcu_tasks synchronize_sched
+#define synchronize_rcu_tasks synchronize_rcu
 static inline void exit_tasks_rcu_start(void) { }
 static inline void exit_tasks_rcu_finish(void) { }
 #endif /* #else #ifdef CONFIG_TASKS_RCU */
@@ -325,9 +304,8 @@ static inline void rcu_preempt_sleep_check(void) { }
  * Helper functions for rcu_dereference_check(), rcu_dereference_protected()
  * and rcu_assign_pointer().  Some of these could be folded into their
  * callers, but they are left separate in order to ease introduction of
- * multiple flavors of pointers to match the multiple flavors of RCU
+ * multiple pointers markings to match different RCU implementations
- * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in
+ * (e.g., __srcu), should this make sense in the future.
- * the future.
  */
 
 #ifdef __CHECKER__
@@ -686,14 +664,9 @@ static inline void rcu_read_unlock(void)
 /**
  * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section
  *
- * This is equivalent of rcu_read_lock(), but to be used when updates
+ * This is equivalent of rcu_read_lock(), but also disables softirqs.
- * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since
+ * Note that anything else that disables softirqs can also serve as
- * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a
+ * an RCU read-side critical section.
- * softirq handler to be a quiescent state, a process in RCU read-side
- * critical section must be protected by disabling softirqs. Read-side
- * critical sections in interrupt context can use just rcu_read_lock(),
- * though this should at least be commented to avoid confusing people
- * reading the code.
  *
  * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh()
  * must occur in the same context, for example, it is illegal to invoke
@@ -726,10 +699,9 @@ static inline void rcu_read_unlock_bh(void)
 /**
  * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section
  *
- * This is equivalent of rcu_read_lock(), but to be used when updates
+ * This is equivalent of rcu_read_lock(), but disables preemption.
- * are being done using call_rcu_sched() or synchronize_rcu_sched().
+ * Read-side critical sections can also be introduced by anything else
- * Read-side critical sections can also be introduced by anything that
+ * that disables preemption, including local_irq_disable() and friends.
- * disables preemption, including local_irq_disable() and friends.
  *
  * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched()
  * must occur in the same context, for example, it is illegal to invoke
@@ -885,4 +857,96 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
 #endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */
 
 
+/* Has the specified rcu_head structure been handed to call_rcu()? */
+
+/*
+ * rcu_head_init - Initialize rcu_head for rcu_head_after_call_rcu()
+ * @rhp: The rcu_head structure to initialize.
+ *
+ * If you intend to invoke rcu_head_after_call_rcu() to test whether a
+ * given rcu_head structure has already been passed to call_rcu(), then
+ * you must also invoke this rcu_head_init() function on it just after
+ * allocating that structure.  Calls to this function must not race with
+ * calls to call_rcu(), rcu_head_after_call_rcu(), or callback invocation.
+ */
+static inline void rcu_head_init(struct rcu_head *rhp)
+{
+	rhp->func = (rcu_callback_t)~0L;
+}
+
+/*
+ * rcu_head_after_call_rcu - Has this rcu_head been passed to call_rcu()?
+ * @rhp: The rcu_head structure to test.
+ * @func: The function passed to call_rcu() along with @rhp.
+ *
+ * Returns @true if the @rhp has been passed to call_rcu() with @func,
+ * and @false otherwise.  Emits a warning in any other case, including
+ * the case where @rhp has already been invoked after a grace period.
+ * Calls to this function must not race with callback invocation.  One way
+ * to avoid such races is to enclose the call to rcu_head_after_call_rcu()
+ * in an RCU read-side critical section that includes a read-side fetch
+ * of the pointer to the structure containing @rhp.
+ */
+static inline bool
+rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f)
+{
+	if (READ_ONCE(rhp->func) == f)
+		return true;
+	WARN_ON_ONCE(READ_ONCE(rhp->func) != (rcu_callback_t)~0L);
+	return false;
+}
+
+
+/* Transitional pre-consolidation compatibility definitions. */
+
+static inline void synchronize_rcu_bh(void)
+{
+	synchronize_rcu();
+}
+
+static inline void synchronize_rcu_bh_expedited(void)
+{
+	synchronize_rcu_expedited();
+}
+
+static inline void call_rcu_bh(struct rcu_head *head, rcu_callback_t func)
+{
+	call_rcu(head, func);
+}
+
+static inline void rcu_barrier_bh(void)
+{
+	rcu_barrier();
+}
+
+static inline void synchronize_sched(void)
+{
+	synchronize_rcu();
+}
+
+static inline void synchronize_sched_expedited(void)
+{
+	synchronize_rcu_expedited();
+}
+
+static inline void call_rcu_sched(struct rcu_head *head, rcu_callback_t func)
+{
+	call_rcu(head, func);
+}
+
+static inline void rcu_barrier_sched(void)
+{
+	rcu_barrier();
+}
+
+static inline unsigned long get_state_synchronize_sched(void)
+{
+	return get_state_synchronize_rcu();
+}
+
+static inline void cond_synchronize_sched(unsigned long oldstate)
+{
+	cond_synchronize_rcu(oldstate);
+}
+
 #endif /* __LINUX_RCUPDATE_H */

include/linux/rcupdate_wait.h

@@ -33,17 +33,17 @@ do {									\
 
 /**
  * synchronize_rcu_mult - Wait concurrently for multiple grace periods
- * @...: List of call_rcu() functions for the flavors to wait on.
+ * @...: List of call_rcu() functions for different grace periods to wait on
  *
- * This macro waits concurrently for multiple flavors of RCU grace periods.
+ * This macro waits concurrently for multiple types of RCU grace periods.
- * For example, synchronize_rcu_mult(call_rcu, call_rcu_bh) would wait
+ * For example, synchronize_rcu_mult(call_rcu, call_rcu_tasks) would wait
- * on concurrent RCU and RCU-bh grace periods.  Waiting on a give SRCU
+ * on concurrent RCU and RCU-tasks grace periods.  Waiting on a give SRCU
  * domain requires you to write a wrapper function for that SRCU domain's
  * call_srcu() function, supplying the corresponding srcu_struct.
  *
- * If Tiny RCU, tell _wait_rcu_gp() not to bother waiting for RCU
+ * If Tiny RCU, tell _wait_rcu_gp() does not bother waiting for RCU,
- * or RCU-bh, given that anywhere synchronize_rcu_mult() can be called
+ * given that anywhere synchronize_rcu_mult() can be called is automatically
- * is automatically a grace period.
+ * a grace period.
  */
 #define synchronize_rcu_mult(...) \
 	_wait_rcu_gp(IS_ENABLED(CONFIG_TINY_RCU), __VA_ARGS__)

include/linux/rcutiny.h

@@ -27,12 +27,6 @@
 
 #include <linux/ktime.h>
 
-struct rcu_dynticks;
-static inline int rcu_dynticks_snap(struct rcu_dynticks *rdtp)
-{
-	return 0;
-}
-
 /* Never flag non-existent other CPUs! */
 static inline bool rcu_eqs_special_set(int cpu) { return false; }
 
@@ -46,53 +40,28 @@ static inline void cond_synchronize_rcu(unsigned long oldstate)
 	might_sleep();
 }
 
-static inline unsigned long get_state_synchronize_sched(void)
+extern void rcu_barrier(void);
-{
-	return 0;
-}
-
-static inline void cond_synchronize_sched(unsigned long oldstate)
-{
-	might_sleep();
-}
-
-extern void rcu_barrier_bh(void);
-extern void rcu_barrier_sched(void);
 
 static inline void synchronize_rcu_expedited(void)
 {
-	synchronize_sched();	/* Only one CPU, so pretty fast anyway!!! */
+	synchronize_rcu();
 }
 
-static inline void rcu_barrier(void)
+static inline void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
-{
-	rcu_barrier_sched();  /* Only one CPU, so only one list of callbacks! */
-}
-
-static inline void synchronize_rcu_bh(void)
-{
-	synchronize_sched();
-}
-
-static inline void synchronize_rcu_bh_expedited(void)
-{
-	synchronize_sched();
-}
-
-static inline void synchronize_sched_expedited(void)
-{
-	synchronize_sched();
-}
-
-static inline void kfree_call_rcu(struct rcu_head *head,
-				  rcu_callback_t func)
 {
 	call_rcu(head, func);
 }
 
+void rcu_qs(void);
+
+static inline void rcu_softirq_qs(void)
+{
+	rcu_qs();
+}
+
 #define rcu_note_context_switch(preempt) \
 	do { \
-		rcu_sched_qs(); \
+		rcu_qs(); \
 		rcu_tasks_qs(current); \
 	} while (0)
 
@@ -108,6 +77,7 @@ static inline int rcu_needs_cpu(u64 basemono, u64 *nextevt)
  */
 static inline void rcu_virt_note_context_switch(int cpu) { }
 static inline void rcu_cpu_stall_reset(void) { }
+static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; }
 static inline void rcu_idle_enter(void) { }
 static inline void rcu_idle_exit(void) { }
 static inline void rcu_irq_enter(void) { }
@@ -115,6 +85,11 @@ static inline void rcu_irq_exit_irqson(void) { }
 static inline void rcu_irq_enter_irqson(void) { }
 static inline void rcu_irq_exit(void) { }
 static inline void exit_rcu(void) { }
+static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
+{
+	return false;
+}
+static inline void rcu_preempt_deferred_qs(struct task_struct *t) { }
 #ifdef CONFIG_SRCU
 void rcu_scheduler_starting(void);
 #else /* #ifndef CONFIG_SRCU */

include/linux/rcutree.h

@@ -30,6 +30,7 @@
 #ifndef __LINUX_RCUTREE_H
 #define __LINUX_RCUTREE_H
 
+void rcu_softirq_qs(void);
 void rcu_note_context_switch(bool preempt);
 int rcu_needs_cpu(u64 basem, u64 *nextevt);
 void rcu_cpu_stall_reset(void);
@@ -44,41 +45,13 @@ static inline void rcu_virt_note_context_switch(int cpu)
 	rcu_note_context_switch(false);
 }
 
-void synchronize_rcu_bh(void);
-void synchronize_sched_expedited(void);
 void synchronize_rcu_expedited(void);
-
 void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func);
 
-/**
- * synchronize_rcu_bh_expedited - Brute-force RCU-bh grace period
- *
- * Wait for an RCU-bh grace period to elapse, but use a "big hammer"
- * approach to force the grace period to end quickly.  This consumes
- * significant time on all CPUs and is unfriendly to real-time workloads,
- * so is thus not recommended for any sort of common-case code.  In fact,
- * if you are using synchronize_rcu_bh_expedited() in a loop, please
- * restructure your code to batch your updates, and then use a single
- * synchronize_rcu_bh() instead.
- *
- * Note that it is illegal to call this function while holding any lock
- * that is acquired by a CPU-hotplug notifier.  And yes, it is also illegal
- * to call this function from a CPU-hotplug notifier.  Failing to observe
- * these restriction will result in deadlock.
- */
-static inline void synchronize_rcu_bh_expedited(void)
-{
-	synchronize_sched_expedited();
-}
-
 void rcu_barrier(void);
-void rcu_barrier_bh(void);
-void rcu_barrier_sched(void);
 bool rcu_eqs_special_set(int cpu);
 unsigned long get_state_synchronize_rcu(void);
 void cond_synchronize_rcu(unsigned long oldstate);
-unsigned long get_state_synchronize_sched(void);
-void cond_synchronize_sched(unsigned long oldstate);
 
 void rcu_idle_enter(void);
 void rcu_idle_exit(void);
@@ -93,7 +66,9 @@ void rcu_scheduler_starting(void);
 extern int rcu_scheduler_active __read_mostly;
 void rcu_end_inkernel_boot(void);
 bool rcu_is_watching(void);
+#ifndef CONFIG_PREEMPT
 void rcu_all_qs(void);
+#endif
 
 /* RCUtree hotplug events */
 int rcutree_prepare_cpu(unsigned int cpu);

include/linux/sched.h

@@ -571,12 +571,8 @@ union rcu_special {
 	struct {
 		u8			blocked;
 		u8			need_qs;
-		u8			exp_need_qs;
-
-		/* Otherwise the compiler can store garbage here: */
-		u8			pad;
 	} b; /* Bits. */
-	u32 s; /* Set of bits. */
+	u16 s; /* Set of bits. */
 };
 
 enum perf_event_task_context {

include/linux/srcutree.h

@@ -105,12 +105,13 @@ struct srcu_struct {
 #define SRCU_STATE_SCAN2	2
 
 #define __SRCU_STRUCT_INIT(name, pcpu_name)				\
-	{								\
+{									\
-		.sda = &pcpu_name,					\
+	.sda = &pcpu_name,						\
-		.lock = __SPIN_LOCK_UNLOCKED(name.lock),		\
+	.lock = __SPIN_LOCK_UNLOCKED(name.lock),			\
-		.srcu_gp_seq_needed = 0 - 1,				\
+	.srcu_gp_seq_needed = -1UL,					\
-		__SRCU_DEP_MAP_INIT(name)				\
+	.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),		\
-	}
+	__SRCU_DEP_MAP_INIT(name)					\
+}
 
 /*
  * Define and initialize a srcu struct at build time.

include/linux/torture.h

@@ -77,7 +77,7 @@ void torture_shutdown_absorb(const char *title);
 int torture_shutdown_init(int ssecs, void (*cleanup)(void));
 
 /* Task stuttering, which forces load/no-load transitions. */
-void stutter_wait(const char *title);
+bool stutter_wait(const char *title);
 int torture_stutter_init(int s);
 
 /* Initialization and cleanup. */

include/trace/events/rcu.h

@@ -393,9 +393,8 @@ TRACE_EVENT(rcu_quiescent_state_report,
  * Tracepoint for quiescent states detected by force_quiescent_state().
  * These trace events include the type of RCU, the grace-period number
  * that was blocked by the CPU, the CPU itself, and the type of quiescent
- * state, which can be "dti" for dyntick-idle mode, "kick" when kicking
+ * state, which can be "dti" for dyntick-idle mode or "kick" when kicking
- * a CPU that has been in dyntick-idle mode for too long, or "rqc" if the
+ * a CPU that has been in dyntick-idle mode for too long.
- * CPU got a quiescent state via its rcu_qs_ctr.
  */
 TRACE_EVENT(rcu_fqs,
 
@@ -705,20 +704,20 @@ TRACE_EVENT(rcu_torture_read,
 );
 
 /*
- * Tracepoint for _rcu_barrier() execution.  The string "s" describes
+ * Tracepoint for rcu_barrier() execution.  The string "s" describes
- * the _rcu_barrier phase:
+ * the rcu_barrier phase:
- *	"Begin": _rcu_barrier() started.
+ *	"Begin": rcu_barrier() started.
- *	"EarlyExit": _rcu_barrier() piggybacked, thus early exit.
+ *	"EarlyExit": rcu_barrier() piggybacked, thus early exit.
- *	"Inc1": _rcu_barrier() piggyback check counter incremented.
+ *	"Inc1": rcu_barrier() piggyback check counter incremented.
- *	"OfflineNoCB": _rcu_barrier() found callback on never-online CPU
+ *	"OfflineNoCB": rcu_barrier() found callback on never-online CPU
- *	"OnlineNoCB": _rcu_barrier() found online no-CBs CPU.
+ *	"OnlineNoCB": rcu_barrier() found online no-CBs CPU.
- *	"OnlineQ": _rcu_barrier() found online CPU with callbacks.
+ *	"OnlineQ": rcu_barrier() found online CPU with callbacks.
- *	"OnlineNQ": _rcu_barrier() found online CPU, no callbacks.
+ *	"OnlineNQ": rcu_barrier() found online CPU, no callbacks.
  *	"IRQ": An rcu_barrier_callback() callback posted on remote CPU.
  *	"IRQNQ": An rcu_barrier_callback() callback found no callbacks.
  *	"CB": An rcu_barrier_callback() invoked a callback, not the last.
  *	"LastCB": An rcu_barrier_callback() invoked the last callback.
- *	"Inc2": _rcu_barrier() piggyback check counter incremented.
+ *	"Inc2": rcu_barrier() piggyback check counter incremented.
  * The "cpu" argument is the CPU or -1 if meaningless, the "cnt" argument
  * is the count of remaining callbacks, and "done" is the piggybacking count.
  */

kernel/rcu/Kconfig

@@ -196,7 +196,7 @@ config RCU_BOOST
 	  This option boosts the priority of preempted RCU readers that
 	  block the current preemptible RCU grace period for too long.
 	  This option also prevents heavy loads from blocking RCU
-	  callback invocation for all flavors of RCU.
+	  callback invocation.
 
 	  Say Y here if you are working with real-time apps or heavy loads
 	  Say N here if you are unsure.
@@ -225,12 +225,12 @@ config RCU_NOCB_CPU
 	  callback invocation to energy-efficient CPUs in battery-powered
 	  asymmetric multiprocessors.
 
-	  This option offloads callback invocation from the set of
+	  This option offloads callback invocation from the set of CPUs
-	  CPUs specified at boot time by the rcu_nocbs parameter.
+	  specified at boot time by the rcu_nocbs parameter.  For each
-	  For each such CPU, a kthread ("rcuox/N") will be created to
+	  such CPU, a kthread ("rcuox/N") will be created to invoke
-	  invoke callbacks, where the "N" is the CPU being offloaded,
+	  callbacks, where the "N" is the CPU being offloaded, and where
-	  and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
+	  the "p" for RCU-preempt (PREEMPT kernels) and "s" for RCU-sched
-	  "s" for RCU-sched.  Nothing prevents this kthread from running
+	  (!PREEMPT kernels).  Nothing prevents this kthread from running
 	  on the specified CPUs, but (1) the kthreads may be preempted
 	  between each callback, and (2) affinity or cgroups can be used
 	  to force the kthreads to run on whatever set of CPUs is desired.

kernel/rcu/rcu.h

@@ -176,8 +176,9 @@ static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old)
 
 /*
  * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
- * by call_rcu() and rcu callback execution, and are therefore not part of the
+ * by call_rcu() and rcu callback execution, and are therefore not part
- * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
+ * of the RCU API. These are in rcupdate.h because they are used by all
+ * RCU implementations.
  */
 
 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
@@ -223,6 +224,7 @@ void kfree(const void *);
  */
 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
 {
+	rcu_callback_t f;
 	unsigned long offset = (unsigned long)head->func;
 
 	rcu_lock_acquire(&rcu_callback_map);
@@ -233,7 +235,9 @@ static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
 		return true;
 	} else {
 		RCU_TRACE(trace_rcu_invoke_callback(rn, head);)
-		head->func(head);
+		f = head->func;
+		WRITE_ONCE(head->func, (rcu_callback_t)0L);
+		f(head);
 		rcu_lock_release(&rcu_callback_map);
 		return false;
 	}
@@ -328,40 +332,35 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
 	}
 }
 
-/* Returns first leaf rcu_node of the specified RCU flavor. */
+/* Returns a pointer to the first leaf rcu_node structure. */
-#define rcu_first_leaf_node(rsp) ((rsp)->level[rcu_num_lvls - 1])
+#define rcu_first_leaf_node() (rcu_state.level[rcu_num_lvls - 1])
 
 /* Is this rcu_node a leaf? */
 #define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1)
 
 /* Is this rcu_node the last leaf? */
-#define rcu_is_last_leaf_node(rsp, rnp) ((rnp) == &(rsp)->node[rcu_num_nodes - 1])
+#define rcu_is_last_leaf_node(rnp) ((rnp) == &rcu_state.node[rcu_num_nodes - 1])
 
 /*
- * Do a full breadth-first scan of the rcu_node structures for the
+ * Do a full breadth-first scan of the {s,}rcu_node structures for the
- * specified rcu_state structure.
+ * specified state structure (for SRCU) or the only rcu_state structure
+ * (for RCU).
  */
-#define rcu_for_each_node_breadth_first(rsp, rnp) \
+#define srcu_for_each_node_breadth_first(sp, rnp) \
-	for ((rnp) = &(rsp)->node[0]; \
+	for ((rnp) = &(sp)->node[0]; \
-	     (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
+	     (rnp) < &(sp)->node[rcu_num_nodes]; (rnp)++)
+#define rcu_for_each_node_breadth_first(rnp) \
+	srcu_for_each_node_breadth_first(&rcu_state, rnp)
 
 /*
- * Do a breadth-first scan of the non-leaf rcu_node structures for the
+ * Scan the leaves of the rcu_node hierarchy for the rcu_state structure.
- * specified rcu_state structure.  Note that if there is a singleton
+ * Note that if there is a singleton rcu_node tree with but one rcu_node
- * rcu_node tree with but one rcu_node structure, this loop is a no-op.
+ * structure, this loop -will- visit the rcu_node structure.  It is still
+ * a leaf node, even if it is also the root node.
  */
-#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
+#define rcu_for_each_leaf_node(rnp) \
-	for ((rnp) = &(rsp)->node[0]; !rcu_is_leaf_node(rsp, rnp); (rnp)++)
+	for ((rnp) = rcu_first_leaf_node(); \
-
+	     (rnp) < &rcu_state.node[rcu_num_nodes]; (rnp)++)
-/*
- * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
- * structure.  Note that if there is a singleton rcu_node tree with but
- * one rcu_node structure, this loop -will- visit the rcu_node structure.
- * It is still a leaf node, even if it is also the root node.
- */
-#define rcu_for_each_leaf_node(rsp, rnp) \
-	for ((rnp) = rcu_first_leaf_node(rsp); \
-	     (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
 
 /*
  * Iterate over all possible CPUs in a leaf RCU node.
@@ -435,6 +434,12 @@ do {									\
 
 #endif /* #if defined(SRCU) || !defined(TINY_RCU) */
 
+#ifdef CONFIG_SRCU
+void srcu_init(void);
+#else /* #ifdef CONFIG_SRCU */
+static inline void srcu_init(void) { }
+#endif /* #else #ifdef CONFIG_SRCU */
+
 #ifdef CONFIG_TINY_RCU
 /* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
 static inline bool rcu_gp_is_normal(void) { return true; }
@@ -515,29 +520,19 @@ void srcutorture_get_gp_data(enum rcutorture_type test_type,
 
 #ifdef CONFIG_TINY_RCU
 static inline unsigned long rcu_get_gp_seq(void) { return 0; }
-static inline unsigned long rcu_bh_get_gp_seq(void) { return 0; }
-static inline unsigned long rcu_sched_get_gp_seq(void) { return 0; }
 static inline unsigned long rcu_exp_batches_completed(void) { return 0; }
-static inline unsigned long rcu_exp_batches_completed_sched(void) { return 0; }
 static inline unsigned long
 srcu_batches_completed(struct srcu_struct *sp) { return 0; }
 static inline void rcu_force_quiescent_state(void) { }
-static inline void rcu_bh_force_quiescent_state(void) { }
-static inline void rcu_sched_force_quiescent_state(void) { }
 static inline void show_rcu_gp_kthreads(void) { }
 static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
 #else /* #ifdef CONFIG_TINY_RCU */
 unsigned long rcu_get_gp_seq(void);
-unsigned long rcu_bh_get_gp_seq(void);
-unsigned long rcu_sched_get_gp_seq(void);
 unsigned long rcu_exp_batches_completed(void);
-unsigned long rcu_exp_batches_completed_sched(void);
 unsigned long srcu_batches_completed(struct srcu_struct *sp);
 void show_rcu_gp_kthreads(void);
 int rcu_get_gp_kthreads_prio(void);
 void rcu_force_quiescent_state(void);
-void rcu_bh_force_quiescent_state(void);
-void rcu_sched_force_quiescent_state(void);
 extern struct workqueue_struct *rcu_gp_wq;
 extern struct workqueue_struct *rcu_par_gp_wq;
 #endif /* #else #ifdef CONFIG_TINY_RCU */

kernel/rcu/rcuperf.c

@@ -189,36 +189,6 @@ static struct rcu_perf_ops rcu_ops = {
 	.name		= "rcu"
 };
 
-/*
- * Definitions for rcu_bh perf testing.
- */
-
-static int rcu_bh_perf_read_lock(void) __acquires(RCU_BH)
-{
-	rcu_read_lock_bh();
-	return 0;
-}
-
-static void rcu_bh_perf_read_unlock(int idx) __releases(RCU_BH)
-{
-	rcu_read_unlock_bh();
-}
-
-static struct rcu_perf_ops rcu_bh_ops = {
-	.ptype		= RCU_BH_FLAVOR,
-	.init		= rcu_sync_perf_init,
-	.readlock	= rcu_bh_perf_read_lock,
-	.readunlock	= rcu_bh_perf_read_unlock,
-	.get_gp_seq	= rcu_bh_get_gp_seq,
-	.gp_diff	= rcu_seq_diff,
-	.exp_completed	= rcu_exp_batches_completed_sched,
-	.async		= call_rcu_bh,
-	.gp_barrier	= rcu_barrier_bh,
-	.sync		= synchronize_rcu_bh,
-	.exp_sync	= synchronize_rcu_bh_expedited,
-	.name		= "rcu_bh"
-};
-
 /*
  * Definitions for srcu perf testing.
  */
@@ -305,36 +275,6 @@ static struct rcu_perf_ops srcud_ops = {
 	.name		= "srcud"
 };
 
-/*
- * Definitions for sched perf testing.
- */
-
-static int sched_perf_read_lock(void)
-{
-	preempt_disable();
-	return 0;
-}
-
-static void sched_perf_read_unlock(int idx)
-{
-	preempt_enable();
-}
-
-static struct rcu_perf_ops sched_ops = {
-	.ptype		= RCU_SCHED_FLAVOR,
-	.init		= rcu_sync_perf_init,
-	.readlock	= sched_perf_read_lock,
-	.readunlock	= sched_perf_read_unlock,
-	.get_gp_seq	= rcu_sched_get_gp_seq,
-	.gp_diff	= rcu_seq_diff,
-	.exp_completed	= rcu_exp_batches_completed_sched,
-	.async		= call_rcu_sched,
-	.gp_barrier	= rcu_barrier_sched,
-	.sync		= synchronize_sched,
-	.exp_sync	= synchronize_sched_expedited,
-	.name		= "sched"
-};
-
 /*
  * Definitions for RCU-tasks perf testing.
  */
@@ -611,7 +551,7 @@ rcu_perf_cleanup(void)
 		kfree(writer_n_durations);
 	}
 
-	/* Do flavor-specific cleanup operations.  */
+	/* Do torture-type-specific cleanup operations.  */
 	if (cur_ops->cleanup != NULL)
 		cur_ops->cleanup();
 
@@ -661,8 +601,7 @@ rcu_perf_init(void)
 	long i;
 	int firsterr = 0;
 	static struct rcu_perf_ops *perf_ops[] = {
-		&rcu_ops, &rcu_bh_ops, &srcu_ops, &srcud_ops, &sched_ops,
+		&rcu_ops, &srcu_ops, &srcud_ops, &tasks_ops,
-		&tasks_ops,
 	};
 
 	if (!torture_init_begin(perf_type, verbose))
@@ -680,6 +619,7 @@ rcu_perf_init(void)
 		for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
 			pr_cont(" %s", perf_ops[i]->name);
 		pr_cont("\n");
+		WARN_ON(!IS_MODULE(CONFIG_RCU_PERF_TEST));
 		firsterr = -EINVAL;
 		goto unwind;
 	}

kernel/rcu/rcutorture.c

@@ -66,15 +66,19 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@jos
 /* Bits for ->extendables field, extendables param, and related definitions. */
 #define RCUTORTURE_RDR_SHIFT	 8	/* Put SRCU index in upper bits. */
 #define RCUTORTURE_RDR_MASK	 ((1 << RCUTORTURE_RDR_SHIFT) - 1)
-#define RCUTORTURE_RDR_BH	 0x1	/* Extend readers by disabling bh. */
+#define RCUTORTURE_RDR_BH	 0x01	/* Extend readers by disabling bh. */
-#define RCUTORTURE_RDR_IRQ	 0x2	/*  ... disabling interrupts. */
+#define RCUTORTURE_RDR_IRQ	 0x02	/*  ... disabling interrupts. */
-#define RCUTORTURE_RDR_PREEMPT	 0x4	/*  ... disabling preemption. */
+#define RCUTORTURE_RDR_PREEMPT	 0x04	/*  ... disabling preemption. */
-#define RCUTORTURE_RDR_RCU	 0x8	/*  ... entering another RCU reader. */
+#define RCUTORTURE_RDR_RBH	 0x08	/*  ... rcu_read_lock_bh(). */
-#define RCUTORTURE_RDR_NBITS	 4	/* Number of bits defined above. */
+#define RCUTORTURE_RDR_SCHED	 0x10	/*  ... rcu_read_lock_sched(). */
-#define RCUTORTURE_MAX_EXTEND	 (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | \
+#define RCUTORTURE_RDR_RCU	 0x20	/*  ... entering another RCU reader. */
-				  RCUTORTURE_RDR_PREEMPT)
+#define RCUTORTURE_RDR_NBITS	 6	/* Number of bits defined above. */
+#define RCUTORTURE_MAX_EXTEND	 \
+	(RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \
+	 RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)
 #define RCUTORTURE_RDR_MAX_LOOPS 0x7	/* Maximum reader extensions. */
 					/* Must be power of two minus one. */
+#define RCUTORTURE_RDR_MAX_SEGS (RCUTORTURE_RDR_MAX_LOOPS + 3)
 
 torture_param(int, cbflood_inter_holdoff, HZ,
 	      "Holdoff between floods (jiffies)");
@@ -89,6 +93,12 @@ torture_param(int, fqs_duration, 0,
 	      "Duration of fqs bursts (us), 0 to disable");
 torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
 torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)");
+torture_param(bool, fwd_progress, 1, "Test grace-period forward progress");
+torture_param(int, fwd_progress_div, 4, "Fraction of CPU stall to wait");
+torture_param(int, fwd_progress_holdoff, 60,
+	      "Time between forward-progress tests (s)");
+torture_param(bool, fwd_progress_need_resched, 1,
+	      "Hide cond_resched() behind need_resched()");
 torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives");
 torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
 torture_param(bool, gp_normal, false,
@@ -125,7 +135,7 @@ torture_param(int, verbose, 1,
 
 static char *torture_type = "rcu";
 module_param(torture_type, charp, 0444);
-MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, ...)");
+MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");
 
 static int nrealreaders;
 static int ncbflooders;
@@ -137,6 +147,7 @@ static struct task_struct **cbflood_task;
 static struct task_struct *fqs_task;
 static struct task_struct *boost_tasks[NR_CPUS];
 static struct task_struct *stall_task;
+static struct task_struct *fwd_prog_task;
 static struct task_struct **barrier_cbs_tasks;
 static struct task_struct *barrier_task;
 
@@ -197,6 +208,18 @@ static const char * const rcu_torture_writer_state_names[] = {
 	"RTWS_STOPPING",
 };
 
+/* Record reader segment types and duration for first failing read. */
+struct rt_read_seg {
+	int rt_readstate;
+	unsigned long rt_delay_jiffies;
+	unsigned long rt_delay_ms;
+	unsigned long rt_delay_us;
+	bool rt_preempted;
+};
+static int err_segs_recorded;
+static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
+static int rt_read_nsegs;
+
 static const char *rcu_torture_writer_state_getname(void)
 {
 	unsigned int i = READ_ONCE(rcu_torture_writer_state);
@@ -278,7 +301,8 @@ struct rcu_torture_ops {
 	void (*init)(void);
 	void (*cleanup)(void);
 	int (*readlock)(void);
-	void (*read_delay)(struct torture_random_state *rrsp);
+	void (*read_delay)(struct torture_random_state *rrsp,
+			   struct rt_read_seg *rtrsp);
 	void (*readunlock)(int idx);
 	unsigned long (*get_gp_seq)(void);
 	unsigned long (*gp_diff)(unsigned long new, unsigned long old);
@@ -291,6 +315,7 @@ struct rcu_torture_ops {
 	void (*cb_barrier)(void);
 	void (*fqs)(void);
 	void (*stats)(void);
+	int (*stall_dur)(void);
 	int irq_capable;
 	int can_boost;
 	int extendables;
@@ -310,12 +335,13 @@ static int rcu_torture_read_lock(void) __acquires(RCU)
 	return 0;
 }
 
-static void rcu_read_delay(struct torture_random_state *rrsp)
+static void
+rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 {
 	unsigned long started;
 	unsigned long completed;
 	const unsigned long shortdelay_us = 200;
-	const unsigned long longdelay_ms = 50;
+	unsigned long longdelay_ms = 300;
 	unsigned long long ts;
 
 	/* We want a short delay sometimes to make a reader delay the grace
@@ -325,16 +351,23 @@ static void rcu_read_delay(struct torture_random_state *rrsp)
 	if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
 		started = cur_ops->get_gp_seq();
 		ts = rcu_trace_clock_local();
+		if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK))
+			longdelay_ms = 5; /* Avoid triggering BH limits. */
 		mdelay(longdelay_ms);
+		rtrsp->rt_delay_ms = longdelay_ms;
 		completed = cur_ops->get_gp_seq();
 		do_trace_rcu_torture_read(cur_ops->name, NULL, ts,
 					  started, completed);
 	}
-	if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us)))
+	if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) {
 		udelay(shortdelay_us);
+		rtrsp->rt_delay_us = shortdelay_us;
+	}
 	if (!preempt_count() &&
-	    !(torture_random(rrsp) % (nrealreaders * 500)))
+	    !(torture_random(rrsp) % (nrealreaders * 500))) {
 		torture_preempt_schedule();  /* QS only if preemptible. */
+		rtrsp->rt_preempted = true;
+	}
 }
 
 static void rcu_torture_read_unlock(int idx) __releases(RCU)
@@ -429,52 +462,13 @@ static struct rcu_torture_ops rcu_ops = {
 	.cb_barrier	= rcu_barrier,
 	.fqs		= rcu_force_quiescent_state,
 	.stats		= NULL,
+	.stall_dur	= rcu_jiffies_till_stall_check,
 	.irq_capable	= 1,
 	.can_boost	= rcu_can_boost(),
+	.extendables	= RCUTORTURE_MAX_EXTEND,
 	.name		= "rcu"
 };
 
-/*
- * Definitions for rcu_bh torture testing.
- */
-
-static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
-{
-	rcu_read_lock_bh();
-	return 0;
-}
-
-static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
-{
-	rcu_read_unlock_bh();
-}
-
-static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
-{
-	call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
-}
-
-static struct rcu_torture_ops rcu_bh_ops = {
-	.ttype		= RCU_BH_FLAVOR,
-	.init		= rcu_sync_torture_init,
-	.readlock	= rcu_bh_torture_read_lock,
-	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
-	.readunlock	= rcu_bh_torture_read_unlock,
-	.get_gp_seq	= rcu_bh_get_gp_seq,
-	.gp_diff	= rcu_seq_diff,
-	.deferred_free	= rcu_bh_torture_deferred_free,
-	.sync		= synchronize_rcu_bh,
-	.exp_sync	= synchronize_rcu_bh_expedited,
-	.call		= call_rcu_bh,
-	.cb_barrier	= rcu_barrier_bh,
-	.fqs		= rcu_bh_force_quiescent_state,
-	.stats		= NULL,
-	.irq_capable	= 1,
-	.extendables	= (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ),
-	.ext_irq_conflict = RCUTORTURE_RDR_RCU,
-	.name		= "rcu_bh"
-};
-
 /*
  * Don't even think about trying any of these in real life!!!
  * The names includes "busted", and they really means it!
@@ -531,7 +525,8 @@ static int srcu_torture_read_lock(void) __acquires(srcu_ctlp)
 	return srcu_read_lock(srcu_ctlp);
 }
 
-static void srcu_read_delay(struct torture_random_state *rrsp)
+static void
+srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 {
 	long delay;
 	const long uspertick = 1000000 / HZ;
@@ -541,10 +536,12 @@ static void srcu_read_delay(struct torture_random_state *rrsp)
 
 	delay = torture_random(rrsp) %
 		(nrealreaders * 2 * longdelay * uspertick);
-	if (!delay && in_task())
+	if (!delay && in_task()) {
 		schedule_timeout_interruptible(longdelay);
-	else
+		rtrsp->rt_delay_jiffies = longdelay;
-		rcu_read_delay(rrsp);
+	} else {
+		rcu_read_delay(rrsp, rtrsp);
+	}
 }
 
 static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp)
@@ -662,48 +659,6 @@ static struct rcu_torture_ops busted_srcud_ops = {
 	.name		= "busted_srcud"
 };
 
-/*
- * Definitions for sched torture testing.
- */
-
-static int sched_torture_read_lock(void)
-{
-	preempt_disable();
-	return 0;
-}
-
-static void sched_torture_read_unlock(int idx)
-{
-	preempt_enable();
-}
-
-static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
-{
-	call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
-}
-
-static struct rcu_torture_ops sched_ops = {
-	.ttype		= RCU_SCHED_FLAVOR,
-	.init		= rcu_sync_torture_init,
-	.readlock	= sched_torture_read_lock,
-	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
-	.readunlock	= sched_torture_read_unlock,
-	.get_gp_seq	= rcu_sched_get_gp_seq,
-	.gp_diff	= rcu_seq_diff,
-	.deferred_free	= rcu_sched_torture_deferred_free,
-	.sync		= synchronize_sched,
-	.exp_sync	= synchronize_sched_expedited,
-	.get_state	= get_state_synchronize_sched,
-	.cond_sync	= cond_synchronize_sched,
-	.call		= call_rcu_sched,
-	.cb_barrier	= rcu_barrier_sched,
-	.fqs		= rcu_sched_force_quiescent_state,
-	.stats		= NULL,
-	.irq_capable	= 1,
-	.extendables	= RCUTORTURE_MAX_EXTEND,
-	.name		= "sched"
-};
-
 /*
  * Definitions for RCU-tasks torture testing.
  */
@@ -1116,7 +1071,8 @@ rcu_torture_writer(void *arg)
 				break;
 			}
 		}
-		rcu_torture_current_version++;
+		WRITE_ONCE(rcu_torture_current_version,
+			   rcu_torture_current_version + 1);
 		/* Cycle through nesting levels of rcu_expedite_gp() calls. */
 		if (can_expedite &&
 		    !(torture_random(&rand) & 0xff & (!!expediting - 1))) {
@@ -1132,7 +1088,10 @@ rcu_torture_writer(void *arg)
 				       !rcu_gp_is_normal();
 		}
 		rcu_torture_writer_state = RTWS_STUTTER;
-		stutter_wait("rcu_torture_writer");
+		if (stutter_wait("rcu_torture_writer"))
+			for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
+				if (list_empty(&rcu_tortures[i].rtort_free))
+					WARN_ON_ONCE(1);
 	} while (!torture_must_stop());
 	/* Reset expediting back to unexpedited. */
 	if (expediting > 0)
@@ -1199,7 +1158,8 @@ static void rcu_torture_timer_cb(struct rcu_head *rhp)
  * change, do a ->read_delay().
  */
 static void rcutorture_one_extend(int *readstate, int newstate,
-				  struct torture_random_state *trsp)
+				  struct torture_random_state *trsp,
+				  struct rt_read_seg *rtrsp)
 {
 	int idxnew = -1;
 	int idxold = *readstate;
@@ -1208,6 +1168,7 @@ static void rcutorture_one_extend(int *readstate, int newstate,
 
 	WARN_ON_ONCE(idxold < 0);
 	WARN_ON_ONCE((idxold >> RCUTORTURE_RDR_SHIFT) > 1);
+	rtrsp->rt_readstate = newstate;
 
 	/* First, put new protection in place to avoid critical-section gap. */
 	if (statesnew & RCUTORTURE_RDR_BH)
@@ -1216,6 +1177,10 @@ static void rcutorture_one_extend(int *readstate, int newstate,
 		local_irq_disable();
 	if (statesnew & RCUTORTURE_RDR_PREEMPT)
 		preempt_disable();
+	if (statesnew & RCUTORTURE_RDR_RBH)
+		rcu_read_lock_bh();
+	if (statesnew & RCUTORTURE_RDR_SCHED)
+		rcu_read_lock_sched();
 	if (statesnew & RCUTORTURE_RDR_RCU)
 		idxnew = cur_ops->readlock() << RCUTORTURE_RDR_SHIFT;
 
@@ -1226,12 +1191,16 @@ static void rcutorture_one_extend(int *readstate, int newstate,
 		local_bh_enable();
 	if (statesold & RCUTORTURE_RDR_PREEMPT)
 		preempt_enable();
+	if (statesold & RCUTORTURE_RDR_RBH)
+		rcu_read_unlock_bh();
+	if (statesold & RCUTORTURE_RDR_SCHED)
+		rcu_read_unlock_sched();
 	if (statesold & RCUTORTURE_RDR_RCU)
 		cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT);
 
 	/* Delay if neither beginning nor end and there was a change. */
 	if ((statesnew || statesold) && *readstate && newstate)
-		cur_ops->read_delay(trsp);
+		cur_ops->read_delay(trsp, rtrsp);
 
 	/* Update the reader state. */
 	if (idxnew == -1)
@@ -1260,18 +1229,19 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
 {
 	int mask = rcutorture_extend_mask_max();
 	unsigned long randmask1 = torture_random(trsp) >> 8;
-	unsigned long randmask2 = randmask1 >> 1;
+	unsigned long randmask2 = randmask1 >> 3;
 
 	WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT);
-	/* Half the time lots of bits, half the time only one bit. */
+	/* Most of the time lots of bits, half the time only one bit. */
-	if (randmask1 & 0x1)
+	if (!(randmask1 & 0x7))
 		mask = mask & randmask2;
 	else
 		mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS));
+	/* Can't enable bh w/irq disabled. */
 	if ((mask & RCUTORTURE_RDR_IRQ) &&
-	    !(mask & RCUTORTURE_RDR_BH) &&
+	    ((!(mask & RCUTORTURE_RDR_BH) && (oldmask & RCUTORTURE_RDR_BH)) ||
-	    (oldmask & RCUTORTURE_RDR_BH))
+	     (!(mask & RCUTORTURE_RDR_RBH) && (oldmask & RCUTORTURE_RDR_RBH))))
-		mask |= RCUTORTURE_RDR_BH; /* Can't enable bh w/irq disabled. */
+		mask |= RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
 	if ((mask & RCUTORTURE_RDR_IRQ) &&
 	    !(mask & cur_ops->ext_irq_conflict) &&
 	    (oldmask & cur_ops->ext_irq_conflict))
@@ -1283,20 +1253,25 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
  * Do a randomly selected number of extensions of an existing RCU read-side
  * critical section.
  */
-static void rcutorture_loop_extend(int *readstate,
+static struct rt_read_seg *
-				   struct torture_random_state *trsp)
+rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
+		       struct rt_read_seg *rtrsp)
 {
 	int i;
+	int j;
 	int mask = rcutorture_extend_mask_max();
 
 	WARN_ON_ONCE(!*readstate); /* -Existing- RCU read-side critsect! */
 	if (!((mask - 1) & mask))
-		return;  /* Current RCU flavor not extendable. */
+		return rtrsp;  /* Current RCU reader not extendable. */
-	i = (torture_random(trsp) >> 3) & RCUTORTURE_RDR_MAX_LOOPS;
+	/* Bias towards larger numbers of loops. */
-	while (i--) {
+	i = (torture_random(trsp) >> 3);
+	i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
+	for (j = 0; j < i; j++) {
 		mask = rcutorture_extend_mask(*readstate, trsp);
-		rcutorture_one_extend(readstate, mask, trsp);
+		rcutorture_one_extend(readstate, mask, trsp, &rtrsp[j]);
 	}
+	return &rtrsp[j];
 }
 
 /*
@@ -1306,16 +1281,20 @@ static void rcutorture_loop_extend(int *readstate,
  */
 static bool rcu_torture_one_read(struct torture_random_state *trsp)
 {
+	int i;
 	unsigned long started;
 	unsigned long completed;
 	int newstate;
 	struct rcu_torture *p;
 	int pipe_count;
 	int readstate = 0;
+	struct rt_read_seg rtseg[RCUTORTURE_RDR_MAX_SEGS] = { { 0 } };
+	struct rt_read_seg *rtrsp = &rtseg[0];
+	struct rt_read_seg *rtrsp1;
 	unsigned long long ts;
 
 	newstate = rcutorture_extend_mask(readstate, trsp);
-	rcutorture_one_extend(&readstate, newstate, trsp);
+	rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
 	started = cur_ops->get_gp_seq();
 	ts = rcu_trace_clock_local();
 	p = rcu_dereference_check(rcu_torture_current,
@@ -1325,12 +1304,12 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
 				  torturing_tasks());
 	if (p == NULL) {
 		/* Wait for rcu_torture_writer to get underway */
-		rcutorture_one_extend(&readstate, 0, trsp);
+		rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
 		return false;
 	}
 	if (p->rtort_mbtest == 0)
 		atomic_inc(&n_rcu_torture_mberror);
-	rcutorture_loop_extend(&readstate, trsp);
+	rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
 	preempt_disable();
 	pipe_count = p->rtort_pipe_count;
 	if (pipe_count > RCU_TORTURE_PIPE_LEN) {
@@ -1351,8 +1330,17 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
 	}
 	__this_cpu_inc(rcu_torture_batch[completed]);
 	preempt_enable();
-	rcutorture_one_extend(&readstate, 0, trsp);
+	rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
 	WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK);
+
+	/* If error or close call, record the sequence of reader protections. */
+	if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) {
+		i = 0;
+		for (rtrsp1 = &rtseg[0]; rtrsp1 < rtrsp; rtrsp1++)
+			err_segs[i++] = *rtrsp1;
+		rt_read_nsegs = i;
+	}
+
 	return true;
 }
 
@@ -1387,6 +1375,9 @@ static void rcu_torture_timer(struct timer_list *unused)
 static int
 rcu_torture_reader(void *arg)
 {
+	unsigned long lastsleep = jiffies;
+	long myid = (long)arg;
+	int mynumonline = myid;
 	DEFINE_TORTURE_RANDOM(rand);
 	struct timer_list t;
 
@@ -1402,6 +1393,12 @@ rcu_torture_reader(void *arg)
 		}
 		if (!rcu_torture_one_read(&rand))
 			schedule_timeout_interruptible(HZ);
+		if (time_after(jiffies, lastsleep)) {
+			schedule_timeout_interruptible(1);
+			lastsleep = jiffies + 10;
+		}
+		while (num_online_cpus() < mynumonline && !torture_must_stop())
+			schedule_timeout_interruptible(HZ / 5);
 		stutter_wait("rcu_torture_reader");
 	} while (!torture_must_stop());
 	if (irqreader && cur_ops->irq_capable) {
@@ -1655,6 +1652,121 @@ static int __init rcu_torture_stall_init(void)
 	return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
 }
 
+/* State structure for forward-progress self-propagating RCU callback. */
+struct fwd_cb_state {
+	struct rcu_head rh;
+	int stop;
+};
+
+/*
+ * Forward-progress self-propagating RCU callback function.  Because
+ * callbacks run from softirq, this function is an implicit RCU read-side
+ * critical section.
+ */
+static void rcu_torture_fwd_prog_cb(struct rcu_head *rhp)
+{
+	struct fwd_cb_state *fcsp = container_of(rhp, struct fwd_cb_state, rh);
+
+	if (READ_ONCE(fcsp->stop)) {
+		WRITE_ONCE(fcsp->stop, 2);
+		return;
+	}
+	cur_ops->call(&fcsp->rh, rcu_torture_fwd_prog_cb);
+}
+
+/* Carry out grace-period forward-progress testing. */
+static int rcu_torture_fwd_prog(void *args)
+{
+	unsigned long cver;
+	unsigned long dur;
+	struct fwd_cb_state fcs;
+	unsigned long gps;
+	int idx;
+	int sd;
+	int sd4;
+	bool selfpropcb = false;
+	unsigned long stopat;
+	int tested = 0;
+	int tested_tries = 0;
+	static DEFINE_TORTURE_RANDOM(trs);
+
+	VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
+	if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST))
+		set_user_nice(current, MAX_NICE);
+	if  (cur_ops->call && cur_ops->sync && cur_ops->cb_barrier) {
+		init_rcu_head_on_stack(&fcs.rh);
+		selfpropcb = true;
+	}
+	do {
+		schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
+		if  (selfpropcb) {
+			WRITE_ONCE(fcs.stop, 0);
+			cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
+		}
+		cver = READ_ONCE(rcu_torture_current_version);
+		gps = cur_ops->get_gp_seq();
+		sd = cur_ops->stall_dur() + 1;
+		sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div;
+		dur = sd4 + torture_random(&trs) % (sd - sd4);
+		stopat = jiffies + dur;
+		while (time_before(jiffies, stopat) && !torture_must_stop()) {
+			idx = cur_ops->readlock();
+			udelay(10);
+			cur_ops->readunlock(idx);
+			if (!fwd_progress_need_resched || need_resched())
+				cond_resched();
+		}
+		tested_tries++;
+		if (!time_before(jiffies, stopat) && !torture_must_stop()) {
+			tested++;
+			cver = READ_ONCE(rcu_torture_current_version) - cver;
+			gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
+			WARN_ON(!cver && gps < 2);
+			pr_alert("%s: Duration %ld cver %ld gps %ld\n", __func__, dur, cver, gps);
+		}
+		if (selfpropcb) {
+			WRITE_ONCE(fcs.stop, 1);
+			cur_ops->sync(); /* Wait for running CB to complete. */
+			cur_ops->cb_barrier(); /* Wait for queued callbacks. */
+		}
+		/* Avoid slow periods, better to test when busy. */
+		stutter_wait("rcu_torture_fwd_prog");
+	} while (!torture_must_stop());
+	if (selfpropcb) {
+		WARN_ON(READ_ONCE(fcs.stop) != 2);
+		destroy_rcu_head_on_stack(&fcs.rh);
+	}
+	/* Short runs might not contain a valid forward-progress attempt. */
+	WARN_ON(!tested && tested_tries >= 5);
+	pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries);
+	torture_kthread_stopping("rcu_torture_fwd_prog");
+	return 0;
+}
+
+/* If forward-progress checking is requested and feasible, spawn the thread. */
+static int __init rcu_torture_fwd_prog_init(void)
+{
+	if (!fwd_progress)
+		return 0; /* Not requested, so don't do it. */
+	if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0) {
+		VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
+		return 0;
+	}
+	if (stall_cpu > 0) {
+		VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
+		if (IS_MODULE(CONFIG_RCU_TORTURE_TESTS))
+			return -EINVAL; /* In module, can fail back to user. */
+		WARN_ON(1); /* Make sure rcutorture notices conflict. */
+		return 0;
+	}
+	if (fwd_progress_holdoff <= 0)
+		fwd_progress_holdoff = 1;
+	if (fwd_progress_div <= 0)
+		fwd_progress_div = 4;
+	return torture_create_kthread(rcu_torture_fwd_prog,
+				      NULL, fwd_prog_task);
+}
+
 /* Callback function for RCU barrier testing. */
 static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
 {
@@ -1817,6 +1929,7 @@ static enum cpuhp_state rcutor_hp;
 static void
 rcu_torture_cleanup(void)
 {
+	int firsttime;
 	int flags = 0;
 	unsigned long gp_seq = 0;
 	int i;
@@ -1828,6 +1941,7 @@ rcu_torture_cleanup(void)
 	}
 
 	rcu_torture_barrier_cleanup();
+	torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
 	torture_stop_kthread(rcu_torture_stall, stall_task);
 	torture_stop_kthread(rcu_torture_writer, writer_task);
 
@@ -1860,7 +1974,7 @@ rcu_torture_cleanup(void)
 		cpuhp_remove_state(rcutor_hp);
 
 	/*
-	 * Wait for all RCU callbacks to fire, then do flavor-specific
+	 * Wait for all RCU callbacks to fire, then do torture-type-specific
 	 * cleanup operations.
 	 */
 	if (cur_ops->cb_barrier != NULL)
@@ -1870,6 +1984,33 @@ rcu_torture_cleanup(void)
 
 	rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
 
+	if (err_segs_recorded) {
+		pr_alert("Failure/close-call rcutorture reader segments:\n");
+		if (rt_read_nsegs == 0)
+			pr_alert("\t: No segments recorded!!!\n");
+		firsttime = 1;
+		for (i = 0; i < rt_read_nsegs; i++) {
+			pr_alert("\t%d: %#x ", i, err_segs[i].rt_readstate);
+			if (err_segs[i].rt_delay_jiffies != 0) {
+				pr_cont("%s%ldjiffies", firsttime ? "" : "+",
+					err_segs[i].rt_delay_jiffies);
+				firsttime = 0;
+			}
+			if (err_segs[i].rt_delay_ms != 0) {
+				pr_cont("%s%ldms", firsttime ? "" : "+",
+					err_segs[i].rt_delay_ms);
+				firsttime = 0;
+			}
+			if (err_segs[i].rt_delay_us != 0) {
+				pr_cont("%s%ldus", firsttime ? "" : "+",
+					err_segs[i].rt_delay_us);
+				firsttime = 0;
+			}
+			pr_cont("%s\n",
+				err_segs[i].rt_preempted ? "preempted" : "");
+
+		}
+	}
 	if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
 		rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
 	else if (torture_onoff_failures())
@@ -1939,12 +2080,12 @@ static void rcu_test_debug_objects(void)
 static int __init
 rcu_torture_init(void)
 {
-	int i;
+	long i;
 	int cpu;
 	int firsterr = 0;
 	static struct rcu_torture_ops *torture_ops[] = {
-		&rcu_ops, &rcu_bh_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
+		&rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
-		&busted_srcud_ops, &sched_ops, &tasks_ops,
+		&busted_srcud_ops, &tasks_ops,
 	};
 
 	if (!torture_init_begin(torture_type, verbose))
@@ -1963,6 +2104,7 @@ rcu_torture_init(void)
 		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
 			pr_cont(" %s", torture_ops[i]->name);
 		pr_cont("\n");
+		WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
 		firsterr = -EINVAL;
 		goto unwind;
 	}
@@ -2013,6 +2155,8 @@ rcu_torture_init(void)
 			per_cpu(rcu_torture_batch, cpu)[i] = 0;
 		}
 	}
+	err_segs_recorded = 0;
+	rt_read_nsegs = 0;
 
 	/* Start up the kthreads. */
 
@@ -2044,7 +2188,7 @@ rcu_torture_init(void)
 		goto unwind;
 	}
 	for (i = 0; i < nrealreaders; i++) {
-		firsterr = torture_create_kthread(rcu_torture_reader, NULL,
+		firsterr = torture_create_kthread(rcu_torture_reader, (void *)i,
 						  reader_tasks[i]);
 		if (firsterr)
 			goto unwind;
@@ -2098,6 +2242,9 @@ rcu_torture_init(void)
 	if (firsterr)
 		goto unwind;
 	firsterr = rcu_torture_stall_init();
+	if (firsterr)
+		goto unwind;
+	firsterr = rcu_torture_fwd_prog_init();
 	if (firsterr)
 		goto unwind;
 	firsterr = rcu_torture_barrier_init();

kernel/rcu/srcutiny.c

@@ -34,6 +34,8 @@
 #include "rcu.h"
 
 int rcu_scheduler_active __read_mostly;
+static LIST_HEAD(srcu_boot_list);
+static bool srcu_init_done;
 
 static int init_srcu_struct_fields(struct srcu_struct *sp)
 {
@@ -46,6 +48,7 @@ static int init_srcu_struct_fields(struct srcu_struct *sp)
 	sp->srcu_gp_waiting = false;
 	sp->srcu_idx = 0;
 	INIT_WORK(&sp->srcu_work, srcu_drive_gp);
+	INIT_LIST_HEAD(&sp->srcu_work.entry);
 	return 0;
 }
 
@@ -179,8 +182,12 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp,
 	*sp->srcu_cb_tail = rhp;
 	sp->srcu_cb_tail = &rhp->next;
 	local_irq_restore(flags);
-	if (!READ_ONCE(sp->srcu_gp_running))
+	if (!READ_ONCE(sp->srcu_gp_running)) {
-		schedule_work(&sp->srcu_work);
+		if (likely(srcu_init_done))
+			schedule_work(&sp->srcu_work);
+		else if (list_empty(&sp->srcu_work.entry))
+			list_add(&sp->srcu_work.entry, &srcu_boot_list);
+	}
 }
 EXPORT_SYMBOL_GPL(call_srcu);
 
@@ -204,3 +211,21 @@ void __init rcu_scheduler_starting(void)
 {
 	rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
 }
+
+/*
+ * Queue work for srcu_struct structures with early boot callbacks.
+ * The work won't actually execute until the workqueue initialization
+ * phase that takes place after the scheduler starts.
+ */
+void __init srcu_init(void)
+{
+	struct srcu_struct *sp;
+
+	srcu_init_done = true;
+	while (!list_empty(&srcu_boot_list)) {
+		sp = list_first_entry(&srcu_boot_list,
+				      struct srcu_struct, srcu_work.entry);
+		list_del_init(&sp->srcu_work.entry);
+		schedule_work(&sp->srcu_work);
+	}
+}

kernel/rcu/srcutree.c

@@ -51,6 +51,10 @@ module_param(exp_holdoff, ulong, 0444);
 static ulong counter_wrap_check = (ULONG_MAX >> 2);
 module_param(counter_wrap_check, ulong, 0444);
 
+/* Early-boot callback-management, so early that no lock is required! */
+static LIST_HEAD(srcu_boot_list);
+static bool __read_mostly srcu_init_done;
+
 static void srcu_invoke_callbacks(struct work_struct *work);
 static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay);
 static void process_srcu(struct work_struct *work);
@@ -105,7 +109,7 @@ static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static)
 	rcu_init_levelspread(levelspread, num_rcu_lvl);
 
 	/* Each pass through this loop initializes one srcu_node structure. */
-	rcu_for_each_node_breadth_first(sp, snp) {
+	srcu_for_each_node_breadth_first(sp, snp) {
 		spin_lock_init(&ACCESS_PRIVATE(snp, lock));
 		WARN_ON_ONCE(ARRAY_SIZE(snp->srcu_have_cbs) !=
 			     ARRAY_SIZE(snp->srcu_data_have_cbs));
@@ -235,7 +239,6 @@ static void check_init_srcu_struct(struct srcu_struct *sp)
 {
 	unsigned long flags;
 
-	WARN_ON_ONCE(rcu_scheduler_active == RCU_SCHEDULER_INIT);
 	/* The smp_load_acquire() pairs with the smp_store_release(). */
 	if (!rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq_needed))) /*^^^*/
 		return; /* Already initialized. */
@@ -561,7 +564,7 @@ static void srcu_gp_end(struct srcu_struct *sp)
 
 	/* Initiate callback invocation as needed. */
 	idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs);
-	rcu_for_each_node_breadth_first(sp, snp) {
+	srcu_for_each_node_breadth_first(sp, snp) {
 		spin_lock_irq_rcu_node(snp);
 		cbs = false;
 		last_lvl = snp >= sp->level[rcu_num_lvls - 1];
@@ -701,7 +704,11 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp,
 	    rcu_seq_state(sp->srcu_gp_seq) == SRCU_STATE_IDLE) {
 		WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed));
 		srcu_gp_start(sp);
-		queue_delayed_work(rcu_gp_wq, &sp->work, srcu_get_delay(sp));
+		if (likely(srcu_init_done))
+			queue_delayed_work(rcu_gp_wq, &sp->work,
+					   srcu_get_delay(sp));
+		else if (list_empty(&sp->work.work.entry))
+			list_add(&sp->work.work.entry, &srcu_boot_list);
 	}
 	spin_unlock_irqrestore_rcu_node(sp, flags);
 }
@@ -980,7 +987,7 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
  * There are memory-ordering constraints implied by synchronize_srcu().
  * On systems with more than one CPU, when synchronize_srcu() returns,
  * each CPU is guaranteed to have executed a full memory barrier since
- * the end of its last corresponding SRCU-sched read-side critical section
+ * the end of its last corresponding SRCU read-side critical section
  * whose beginning preceded the call to synchronize_srcu().  In addition,
  * each CPU having an SRCU read-side critical section that extends beyond
  * the return from synchronize_srcu() is guaranteed to have executed a
@@ -1308,3 +1315,17 @@ static int __init srcu_bootup_announce(void)
 	return 0;
 }
 early_initcall(srcu_bootup_announce);
+
+void __init srcu_init(void)
+{
+	struct srcu_struct *sp;
+
+	srcu_init_done = true;
+	while (!list_empty(&srcu_boot_list)) {
+		sp = list_first_entry(&srcu_boot_list, struct srcu_struct,
+				      work.work.entry);
+		check_init_srcu_struct(sp);
+		list_del_init(&sp->work.work.entry);
+		queue_work(rcu_gp_wq, &sp->work.work);
+	}
+}

kernel/rcu/tiny.c

@@ -46,69 +46,27 @@ struct rcu_ctrlblk {
 };
 
 /* Definition for rcupdate control block. */
-static struct rcu_ctrlblk rcu_sched_ctrlblk = {
+static struct rcu_ctrlblk rcu_ctrlblk = {
-	.donetail	= &rcu_sched_ctrlblk.rcucblist,
+	.donetail	= &rcu_ctrlblk.rcucblist,
-	.curtail	= &rcu_sched_ctrlblk.rcucblist,
+	.curtail	= &rcu_ctrlblk.rcucblist,
 };
 
-static struct rcu_ctrlblk rcu_bh_ctrlblk = {
+void rcu_barrier(void)
-	.donetail	= &rcu_bh_ctrlblk.rcucblist,
-	.curtail	= &rcu_bh_ctrlblk.rcucblist,
-};
-
-void rcu_barrier_bh(void)
 {
-	wait_rcu_gp(call_rcu_bh);
+	wait_rcu_gp(call_rcu);
 }
-EXPORT_SYMBOL(rcu_barrier_bh);
+EXPORT_SYMBOL(rcu_barrier);
 
-void rcu_barrier_sched(void)
+/* Record an rcu quiescent state.  */
+void rcu_qs(void)
 {
-	wait_rcu_gp(call_rcu_sched);
+	unsigned long flags;
-}
-EXPORT_SYMBOL(rcu_barrier_sched);
 
-/*
+	local_irq_save(flags);
- * Helper function for rcu_sched_qs() and rcu_bh_qs().
+	if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail) {
- * Also irqs are disabled to avoid confusion due to interrupt handlers
+		rcu_ctrlblk.donetail = rcu_ctrlblk.curtail;
- * invoking call_rcu().
+		raise_softirq(RCU_SOFTIRQ);
- */
-static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
-{
-	if (rcp->donetail != rcp->curtail) {
-		rcp->donetail = rcp->curtail;
-		return 1;
 	}
-
-	return 0;
-}
-
-/*
- * Record an rcu quiescent state.  And an rcu_bh quiescent state while we
- * are at it, given that any rcu quiescent state is also an rcu_bh
- * quiescent state.  Use "+" instead of "||" to defeat short circuiting.
- */
-void rcu_sched_qs(void)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
-	    rcu_qsctr_help(&rcu_bh_ctrlblk))
-		raise_softirq(RCU_SOFTIRQ);
-	local_irq_restore(flags);
-}
-
-/*
- * Record an rcu_bh quiescent state.
- */
-void rcu_bh_qs(void)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
-		raise_softirq(RCU_SOFTIRQ);
 	local_irq_restore(flags);
 }
 
@@ -120,34 +78,33 @@ void rcu_bh_qs(void)
  */
 void rcu_check_callbacks(int user)
 {
-	if (user)
+	if (user) {
-		rcu_sched_qs();
+		rcu_qs();
-	if (user || !in_softirq())
+	} else if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail) {
-		rcu_bh_qs();
+		set_tsk_need_resched(current);
+		set_preempt_need_resched();
+	}
 }
 
-/*
+/* Invoke the RCU callbacks whose grace period has elapsed.  */
- * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
+static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused)
- * whose grace period has elapsed.
- */
-static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 {
 	struct rcu_head *next, *list;
 	unsigned long flags;
 
 	/* Move the ready-to-invoke callbacks to a local list. */
 	local_irq_save(flags);
-	if (rcp->donetail == &rcp->rcucblist) {
+	if (rcu_ctrlblk.donetail == &rcu_ctrlblk.rcucblist) {
 		/* No callbacks ready, so just leave. */
 		local_irq_restore(flags);
 		return;
 	}
-	list = rcp->rcucblist;
+	list = rcu_ctrlblk.rcucblist;
-	rcp->rcucblist = *rcp->donetail;
+	rcu_ctrlblk.rcucblist = *rcu_ctrlblk.donetail;
-	*rcp->donetail = NULL;
+	*rcu_ctrlblk.donetail = NULL;
-	if (rcp->curtail == rcp->donetail)
+	if (rcu_ctrlblk.curtail == rcu_ctrlblk.donetail)
-		rcp->curtail = &rcp->rcucblist;
+		rcu_ctrlblk.curtail = &rcu_ctrlblk.rcucblist;
-	rcp->donetail = &rcp->rcucblist;
+	rcu_ctrlblk.donetail = &rcu_ctrlblk.rcucblist;
 	local_irq_restore(flags);
 
 	/* Invoke the callbacks on the local list. */
@@ -162,37 +119,31 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 	}
 }
 
-static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused)
-{
-	__rcu_process_callbacks(&rcu_sched_ctrlblk);
-	__rcu_process_callbacks(&rcu_bh_ctrlblk);
-}
-
 /*
  * Wait for a grace period to elapse.  But it is illegal to invoke
- * synchronize_sched() from within an RCU read-side critical section.
+ * synchronize_rcu() from within an RCU read-side critical section.
- * Therefore, any legal call to synchronize_sched() is a quiescent
+ * Therefore, any legal call to synchronize_rcu() is a quiescent
- * state, and so on a UP system, synchronize_sched() need do nothing.
+ * state, and so on a UP system, synchronize_rcu() need do nothing.
- * Ditto for synchronize_rcu_bh().  (But Lai Jiangshan points out the
+ * (But Lai Jiangshan points out the benefits of doing might_sleep()
- * benefits of doing might_sleep() to reduce latency.)
+ * to reduce latency.)
  *
  * Cool, huh?  (Due to Josh Triplett.)
  */
-void synchronize_sched(void)
+void synchronize_rcu(void)
 {
 	RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
 			 lock_is_held(&rcu_lock_map) ||
 			 lock_is_held(&rcu_sched_lock_map),
-			 "Illegal synchronize_sched() in RCU read-side critical section");
+			 "Illegal synchronize_rcu() in RCU read-side critical section");
 }
-EXPORT_SYMBOL_GPL(synchronize_sched);
+EXPORT_SYMBOL_GPL(synchronize_rcu);
 
 /*
- * Helper function for call_rcu() and call_rcu_bh().
+ * Post an RCU callback to be invoked after the end of an RCU grace
+ * period.  But since we have but one CPU, that would be after any
+ * quiescent state.
  */
-static void __call_rcu(struct rcu_head *head,
+void call_rcu(struct rcu_head *head, rcu_callback_t func)
-		       rcu_callback_t func,
-		       struct rcu_ctrlblk *rcp)
 {
 	unsigned long flags;
 
@@ -201,39 +152,20 @@ static void __call_rcu(struct rcu_head *head,
 	head->next = NULL;
 
 	local_irq_save(flags);
-	*rcp->curtail = head;
+	*rcu_ctrlblk.curtail = head;
-	rcp->curtail = &head->next;
+	rcu_ctrlblk.curtail = &head->next;
 	local_irq_restore(flags);
 
 	if (unlikely(is_idle_task(current))) {
-		/* force scheduling for rcu_sched_qs() */
+		/* force scheduling for rcu_qs() */
 		resched_cpu(0);
 	}
 }
-
+EXPORT_SYMBOL_GPL(call_rcu);
-/*
- * Post an RCU callback to be invoked after the end of an RCU-sched grace
- * period.  But since we have but one CPU, that would be after any
- * quiescent state.
- */
-void call_rcu_sched(struct rcu_head *head, rcu_callback_t func)
-{
-	__call_rcu(head, func, &rcu_sched_ctrlblk);
-}
-EXPORT_SYMBOL_GPL(call_rcu_sched);
-
-/*
- * Post an RCU bottom-half callback to be invoked after any subsequent
- * quiescent state.
- */
-void call_rcu_bh(struct rcu_head *head, rcu_callback_t func)
-{
-	__call_rcu(head, func, &rcu_bh_ctrlblk);
-}
-EXPORT_SYMBOL_GPL(call_rcu_bh);
 
 void __init rcu_init(void)
 {
 	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
 	rcu_early_boot_tests();
+	srcu_init();
 }

kernel/rcu/tree.h

@@ -34,34 +34,9 @@
 
 #include "rcu_segcblist.h"
 
-/*
- * Dynticks per-CPU state.
- */
-struct rcu_dynticks {
-	long dynticks_nesting;      /* Track process nesting level. */
-	long dynticks_nmi_nesting;  /* Track irq/NMI nesting level. */
-	atomic_t dynticks;	    /* Even value for idle, else odd. */
-	bool rcu_need_heavy_qs;     /* GP old, need heavy quiescent state. */
-	unsigned long rcu_qs_ctr;   /* Light universal quiescent state ctr. */
-	bool rcu_urgent_qs;	    /* GP old need light quiescent state. */
-#ifdef CONFIG_RCU_FAST_NO_HZ
-	bool all_lazy;		    /* Are all CPU's CBs lazy? */
-	unsigned long nonlazy_posted;
-				    /* # times non-lazy CBs posted to CPU. */
-	unsigned long nonlazy_posted_snap;
-				    /* idle-period nonlazy_posted snapshot. */
-	unsigned long last_accelerate;
-				    /* Last jiffy CBs were accelerated. */
-	unsigned long last_advance_all;
-				    /* Last jiffy CBs were all advanced. */
-	int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
-#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
-};
-
 /* Communicate arguments to a workqueue handler. */
 struct rcu_exp_work {
 	smp_call_func_t rew_func;
-	struct rcu_state *rew_rsp;
 	unsigned long rew_s;
 	struct work_struct rew_work;
 };
@@ -170,7 +145,7 @@ struct rcu_node {
  * are indexed relative to this interval rather than the global CPU ID space.
  * This generates the bit for a CPU in node-local masks.
  */
-#define leaf_node_cpu_bit(rnp, cpu) (1UL << ((cpu) - (rnp)->grplo))
+#define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))
 
 /*
  * Union to allow "aggregate OR" operation on the need for a quiescent
@@ -189,12 +164,11 @@ struct rcu_data {
 	/* 1) quiescent-state and grace-period handling : */
 	unsigned long	gp_seq;		/* Track rsp->rcu_gp_seq counter. */
 	unsigned long	gp_seq_needed;	/* Track rsp->rcu_gp_seq_needed ctr. */
-	unsigned long	rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
-					/*  for rcu_all_qs() invocations. */
 	union rcu_noqs	cpu_no_qs;	/* No QSes yet for this CPU. */
 	bool		core_needs_qs;	/* Core waits for quiesc state. */
 	bool		beenonline;	/* CPU online at least once. */
 	bool		gpwrap;		/* Possible ->gp_seq wrap. */
+	bool		deferred_qs;	/* This CPU awaiting a deferred QS? */
 	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */
 	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */
 	unsigned long	ticks_this_gp;	/* The number of scheduling-clock */
@@ -213,23 +187,27 @@ struct rcu_data {
 	long		blimit;		/* Upper limit on a processed batch */
 
 	/* 3) dynticks interface. */
-	struct rcu_dynticks *dynticks;	/* Shared per-CPU dynticks state. */
 	int dynticks_snap;		/* Per-GP tracking for dynticks. */
-
+	long dynticks_nesting;		/* Track process nesting level. */
-	/* 4) reasons this CPU needed to be kicked by force_quiescent_state */
+	long dynticks_nmi_nesting;	/* Track irq/NMI nesting level. */
-	unsigned long dynticks_fqs;	/* Kicked due to dynticks idle. */
+	atomic_t dynticks;		/* Even value for idle, else odd. */
-	unsigned long cond_resched_completed;
+	bool rcu_need_heavy_qs;		/* GP old, so heavy quiescent state! */
-					/* Grace period that needs help */
+	bool rcu_urgent_qs;		/* GP old need light quiescent state. */
-					/*  from cond_resched(). */
-
-	/* 5) _rcu_barrier(), OOM callbacks, and expediting. */
-	struct rcu_head barrier_head;
 #ifdef CONFIG_RCU_FAST_NO_HZ
-	struct rcu_head oom_head;
+	bool all_lazy;			/* Are all CPU's CBs lazy? */
+	unsigned long nonlazy_posted;	/* # times non-lazy CB posted to CPU. */
+	unsigned long nonlazy_posted_snap;
+					/* Nonlazy_posted snapshot. */
+	unsigned long last_accelerate;	/* Last jiffy CBs were accelerated. */
+	unsigned long last_advance_all;	/* Last jiffy CBs were all advanced. */
+	int tick_nohz_enabled_snap;	/* Previously seen value from sysfs. */
 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
+
+	/* 4) rcu_barrier(), OOM callbacks, and expediting. */
+	struct rcu_head barrier_head;
 	int exp_dynticks_snap;		/* Double-check need for IPI. */
 
-	/* 6) Callback offloading. */
+	/* 5) Callback offloading. */
 #ifdef CONFIG_RCU_NOCB_CPU
 	struct rcu_head *nocb_head;	/* CBs waiting for kthread. */
 	struct rcu_head **nocb_tail;
@@ -256,7 +234,7 @@ struct rcu_data {
 					/* Leader CPU takes GP-end wakeups. */
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 
-	/* 7) Diagnostic data, including RCU CPU stall warnings. */
+	/* 6) Diagnostic data, including RCU CPU stall warnings. */
 	unsigned int softirq_snap;	/* Snapshot of softirq activity. */
 	/* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
 	struct irq_work rcu_iw;		/* Check for non-irq activity. */
@@ -266,9 +244,9 @@ struct rcu_data {
 	short rcu_ofl_gp_flags;		/* ->gp_flags at last offline. */
 	unsigned long rcu_onl_gp_seq;	/* ->gp_seq at last online. */
 	short rcu_onl_gp_flags;		/* ->gp_flags at last online. */
+	unsigned long last_fqs_resched;	/* Time of last rcu_resched(). */
 
 	int cpu;
-	struct rcu_state *rsp;
 };
 
 /* Values for nocb_defer_wakeup field in struct rcu_data. */
@@ -314,8 +292,6 @@ struct rcu_state {
 	struct rcu_node *level[RCU_NUM_LVLS + 1];
 						/* Hierarchy levels (+1 to */
 						/*  shut bogus gcc warning) */
-	struct rcu_data __percpu *rda;		/* pointer of percu rcu_data. */
-	call_rcu_func_t call;			/* call_rcu() flavor. */
 	int ncpus;				/* # CPUs seen so far. */
 
 	/* The following fields are guarded by the root rcu_node's lock. */
@@ -334,7 +310,7 @@ struct rcu_state {
 	atomic_t barrier_cpu_count;		/* # CPUs waiting on. */
 	struct completion barrier_completion;	/* Wake at barrier end. */
 	unsigned long barrier_sequence;		/* ++ at start and end of */
-						/*  _rcu_barrier(). */
+						/*  rcu_barrier(). */
 	/* End of fields guarded by barrier_mutex. */
 
 	struct mutex exp_mutex;			/* Serialize expedited GP. */
@@ -366,9 +342,8 @@ struct rcu_state {
 						/*  jiffies. */
 	const char *name;			/* Name of structure. */
 	char abbr;				/* Abbreviated name. */
-	struct list_head flavors;		/* List of RCU flavors. */
 
-	spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
+	raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
 						/* Synchronize offline with */
 						/*  GP pre-initialization. */
 };
@@ -388,7 +363,6 @@ struct rcu_state {
 #define RCU_GP_CLEANUP   7	/* Grace-period cleanup started. */
 #define RCU_GP_CLEANED   8	/* Grace-period cleanup complete. */
 
-#ifndef RCU_TREE_NONCORE
 static const char * const gp_state_names[] = {
 	"RCU_GP_IDLE",
 	"RCU_GP_WAIT_GPS",
@@ -400,13 +374,29 @@ static const char * const gp_state_names[] = {
 	"RCU_GP_CLEANUP",
 	"RCU_GP_CLEANED",
 };
-#endif /* #ifndef RCU_TREE_NONCORE */
 
-extern struct list_head rcu_struct_flavors;
+/*
-
+ * In order to export the rcu_state name to the tracing tools, it
-/* Sequence through rcu_state structures for each RCU flavor. */
+ * needs to be added in the __tracepoint_string section.
-#define for_each_rcu_flavor(rsp) \
+ * This requires defining a separate variable tp_<sname>_varname
-	list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
+ * that points to the string being used, and this will allow
+ * the tracing userspace tools to be able to decipher the string
+ * address to the matching string.
+ */
+#ifdef CONFIG_PREEMPT_RCU
+#define RCU_ABBR 'p'
+#define RCU_NAME_RAW "rcu_preempt"
+#else /* #ifdef CONFIG_PREEMPT_RCU */
+#define RCU_ABBR 's'
+#define RCU_NAME_RAW "rcu_sched"
+#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
+#ifndef CONFIG_TRACING
+#define RCU_NAME RCU_NAME_RAW
+#else /* #ifdef CONFIG_TRACING */
+static char rcu_name[] = RCU_NAME_RAW;
+static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
+#define RCU_NAME rcu_name
+#endif /* #else #ifdef CONFIG_TRACING */
 
 /*
  * RCU implementation internal declarations:
@@ -419,7 +409,7 @@ extern struct rcu_state rcu_bh_state;
 extern struct rcu_state rcu_preempt_state;
 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 
-int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
+int rcu_dynticks_snap(struct rcu_data *rdp);
 
 #ifdef CONFIG_RCU_BOOST
 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
@@ -428,45 +418,37 @@ DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 DECLARE_PER_CPU(char, rcu_cpu_has_work);
 #endif /* #ifdef CONFIG_RCU_BOOST */
 
-#ifndef RCU_TREE_NONCORE
-
 /* Forward declarations for rcutree_plugin.h */
 static void rcu_bootup_announce(void);
-static void rcu_preempt_note_context_switch(bool preempt);
+static void rcu_qs(void);
 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 #ifdef CONFIG_HOTPLUG_CPU
 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
-static void rcu_print_detail_task_stall(struct rcu_state *rsp);
+static void rcu_print_detail_task_stall(void);
 static int rcu_print_task_stall(struct rcu_node *rnp);
 static int rcu_print_task_exp_stall(struct rcu_node *rnp);
-static void rcu_preempt_check_blocked_tasks(struct rcu_state *rsp,
+static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
-					    struct rcu_node *rnp);
+static void rcu_flavor_check_callbacks(int user);
-static void rcu_preempt_check_callbacks(void);
 void call_rcu(struct rcu_head *head, rcu_callback_t func);
-static void __init __rcu_init_preempt(void);
+static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
-static void dump_blkd_tasks(struct rcu_state *rsp, struct rcu_node *rnp,
-			    int ncheck);
 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
 static void invoke_rcu_callbacks_kthread(void);
 static bool rcu_is_callbacks_kthread(void);
-#ifdef CONFIG_RCU_BOOST
-static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
-						 struct rcu_node *rnp);
-#endif /* #ifdef CONFIG_RCU_BOOST */
 static void __init rcu_spawn_boost_kthreads(void);
 static void rcu_prepare_kthreads(int cpu);
 static void rcu_cleanup_after_idle(void);
 static void rcu_prepare_for_idle(void);
 static void rcu_idle_count_callbacks_posted(void);
 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
+static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
+static void rcu_preempt_deferred_qs(struct task_struct *t);
 static void print_cpu_stall_info_begin(void);
-static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
+static void print_cpu_stall_info(int cpu);
 static void print_cpu_stall_info_end(void);
 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
-static void increment_cpu_stall_ticks(void);
+static bool rcu_nocb_cpu_needs_barrier(int cpu);
-static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
 static void rcu_init_one_nocb(struct rcu_node *rnp);
@@ -481,11 +463,11 @@ static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
 static void rcu_spawn_all_nocb_kthreads(int cpu);
 static void __init rcu_spawn_nocb_kthreads(void);
 #ifdef CONFIG_RCU_NOCB_CPU
-static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
+static void __init rcu_organize_nocb_kthreads(void);
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 static bool init_nocb_callback_list(struct rcu_data *rdp);
 static void rcu_bind_gp_kthread(void);
-static bool rcu_nohz_full_cpu(struct rcu_state *rsp);
+static bool rcu_nohz_full_cpu(void);
 static void rcu_dynticks_task_enter(void);
 static void rcu_dynticks_task_exit(void);
 
@@ -496,5 +478,3 @@ void srcu_offline_cpu(unsigned int cpu);
 void srcu_online_cpu(unsigned int cpu) { }
 void srcu_offline_cpu(unsigned int cpu) { }
 #endif /* #else #ifdef CONFIG_SRCU */
-
-#endif /* #ifndef RCU_TREE_NONCORE */

kernel/rcu/tree_exp.h

@@ -25,39 +25,39 @@
 /*
  * Record the start of an expedited grace period.
  */
-static void rcu_exp_gp_seq_start(struct rcu_state *rsp)
+static void rcu_exp_gp_seq_start(void)
 {
-	rcu_seq_start(&rsp->expedited_sequence);
+	rcu_seq_start(&rcu_state.expedited_sequence);
 }
 
 /*
  * Return then value that expedited-grace-period counter will have
  * at the end of the current grace period.
  */
-static __maybe_unused unsigned long rcu_exp_gp_seq_endval(struct rcu_state *rsp)
+static __maybe_unused unsigned long rcu_exp_gp_seq_endval(void)
 {
-	return rcu_seq_endval(&rsp->expedited_sequence);
+	return rcu_seq_endval(&rcu_state.expedited_sequence);
 }
 
 /*
  * Record the end of an expedited grace period.
  */
-static void rcu_exp_gp_seq_end(struct rcu_state *rsp)
+static void rcu_exp_gp_seq_end(void)
 {
-	rcu_seq_end(&rsp->expedited_sequence);
+	rcu_seq_end(&rcu_state.expedited_sequence);
 	smp_mb(); /* Ensure that consecutive grace periods serialize. */
 }
 
 /*
  * Take a snapshot of the expedited-grace-period counter.
  */
-static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
+static unsigned long rcu_exp_gp_seq_snap(void)
 {
 	unsigned long s;
 
 	smp_mb(); /* Caller's modifications seen first by other CPUs. */
-	s = rcu_seq_snap(&rsp->expedited_sequence);
+	s = rcu_seq_snap(&rcu_state.expedited_sequence);
-	trace_rcu_exp_grace_period(rsp->name, s, TPS("snap"));
+	trace_rcu_exp_grace_period(rcu_state.name, s, TPS("snap"));
 	return s;
 }
 
@@ -66,9 +66,9 @@ static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
  * if a full expedited grace period has elapsed since that snapshot
  * was taken.
  */
-static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
+static bool rcu_exp_gp_seq_done(unsigned long s)
 {
-	return rcu_seq_done(&rsp->expedited_sequence, s);
+	return rcu_seq_done(&rcu_state.expedited_sequence, s);
 }
 
 /*
@@ -78,26 +78,26 @@ static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
  * ever been online.  This means that this function normally takes its
  * no-work-to-do fastpath.
  */
-static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp)
+static void sync_exp_reset_tree_hotplug(void)
 {
 	bool done;
 	unsigned long flags;
 	unsigned long mask;
 	unsigned long oldmask;
-	int ncpus = smp_load_acquire(&rsp->ncpus); /* Order against locking. */
+	int ncpus = smp_load_acquire(&rcu_state.ncpus); /* Order vs. locking. */
 	struct rcu_node *rnp;
 	struct rcu_node *rnp_up;
 
 	/* If no new CPUs onlined since last time, nothing to do. */
-	if (likely(ncpus == rsp->ncpus_snap))
+	if (likely(ncpus == rcu_state.ncpus_snap))
 		return;
-	rsp->ncpus_snap = ncpus;
+	rcu_state.ncpus_snap = ncpus;
 
 	/*
 	 * Each pass through the following loop propagates newly onlined
 	 * CPUs for the current rcu_node structure up the rcu_node tree.
 	 */
-	rcu_for_each_leaf_node(rsp, rnp) {
+	rcu_for_each_leaf_node(rnp) {
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		if (rnp->expmaskinit == rnp->expmaskinitnext) {
 			raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
@@ -135,13 +135,13 @@ static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp)
  * Reset the ->expmask values in the rcu_node tree in preparation for
  * a new expedited grace period.
  */
-static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp)
+static void __maybe_unused sync_exp_reset_tree(void)
 {
 	unsigned long flags;
 	struct rcu_node *rnp;
 
-	sync_exp_reset_tree_hotplug(rsp);
+	sync_exp_reset_tree_hotplug();
-	rcu_for_each_node_breadth_first(rsp, rnp) {
+	rcu_for_each_node_breadth_first(rnp) {
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		WARN_ON_ONCE(rnp->expmask);
 		rnp->expmask = rnp->expmaskinit;
@@ -194,7 +194,7 @@ static bool sync_rcu_preempt_exp_done_unlocked(struct rcu_node *rnp)
  *
  * Caller must hold the specified rcu_node structure's ->lock.
  */
-static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
+static void __rcu_report_exp_rnp(struct rcu_node *rnp,
 				 bool wake, unsigned long flags)
 	__releases(rnp->lock)
 {
@@ -212,7 +212,7 @@ static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
 			raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 			if (wake) {
 				smp_mb(); /* EGP done before wake_up(). */
-				swake_up_one(&rsp->expedited_wq);
+				swake_up_one(&rcu_state.expedited_wq);
 			}
 			break;
 		}
@@ -229,20 +229,19 @@ static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
  * Report expedited quiescent state for specified node.  This is a
  * lock-acquisition wrapper function for __rcu_report_exp_rnp().
  */
-static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
+static void __maybe_unused rcu_report_exp_rnp(struct rcu_node *rnp, bool wake)
-					      struct rcu_node *rnp, bool wake)
 {
 	unsigned long flags;
 
 	raw_spin_lock_irqsave_rcu_node(rnp, flags);
-	__rcu_report_exp_rnp(rsp, rnp, wake, flags);
+	__rcu_report_exp_rnp(rnp, wake, flags);
 }
 
 /*
  * Report expedited quiescent state for multiple CPUs, all covered by the
  * specified leaf rcu_node structure.
  */
-static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
+static void rcu_report_exp_cpu_mult(struct rcu_node *rnp,
 				    unsigned long mask, bool wake)
 {
 	unsigned long flags;
@@ -253,23 +252,23 @@ static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
 		return;
 	}
 	rnp->expmask &= ~mask;
-	__rcu_report_exp_rnp(rsp, rnp, wake, flags); /* Releases rnp->lock. */
+	__rcu_report_exp_rnp(rnp, wake, flags); /* Releases rnp->lock. */
 }
 
 /*
  * Report expedited quiescent state for specified rcu_data (CPU).
  */
-static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp,
+static void rcu_report_exp_rdp(struct rcu_data *rdp)
-			       bool wake)
 {
-	rcu_report_exp_cpu_mult(rsp, rdp->mynode, rdp->grpmask, wake);
+	WRITE_ONCE(rdp->deferred_qs, false);
+	rcu_report_exp_cpu_mult(rdp->mynode, rdp->grpmask, true);
 }
 
-/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */
+/* Common code for work-done checking. */
-static bool sync_exp_work_done(struct rcu_state *rsp, unsigned long s)
+static bool sync_exp_work_done(unsigned long s)
 {
-	if (rcu_exp_gp_seq_done(rsp, s)) {
+	if (rcu_exp_gp_seq_done(s)) {
-		trace_rcu_exp_grace_period(rsp->name, s, TPS("done"));
+		trace_rcu_exp_grace_period(rcu_state.name, s, TPS("done"));
 		/* Ensure test happens before caller kfree(). */
 		smp_mb__before_atomic(); /* ^^^ */
 		return true;
@@ -284,28 +283,28 @@ static bool sync_exp_work_done(struct rcu_state *rsp, unsigned long s)
  * with the mutex held, indicating that the caller must actually do the
  * expedited grace period.
  */
-static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
+static bool exp_funnel_lock(unsigned long s)
 {
-	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id());
+	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id());
 	struct rcu_node *rnp = rdp->mynode;
-	struct rcu_node *rnp_root = rcu_get_root(rsp);
+	struct rcu_node *rnp_root = rcu_get_root();
 
 	/* Low-contention fastpath. */
 	if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) &&
 	    (rnp == rnp_root ||
 	     ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) &&
-	    mutex_trylock(&rsp->exp_mutex))
+	    mutex_trylock(&rcu_state.exp_mutex))
 		goto fastpath;
 
 	/*
 	 * Each pass through the following loop works its way up
 	 * the rcu_node tree, returning if others have done the work or
-	 * otherwise falls through to acquire rsp->exp_mutex.  The mapping
+	 * otherwise falls through to acquire ->exp_mutex.  The mapping
 	 * from CPU to rcu_node structure can be inexact, as it is just
 	 * promoting locality and is not strictly needed for correctness.
 	 */
 	for (; rnp != NULL; rnp = rnp->parent) {
-		if (sync_exp_work_done(rsp, s))
+		if (sync_exp_work_done(s))
 			return true;
 
 		/* Work not done, either wait here or go up. */
@@ -314,68 +313,29 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
 
 			/* Someone else doing GP, so wait for them. */
 			spin_unlock(&rnp->exp_lock);
-			trace_rcu_exp_funnel_lock(rsp->name, rnp->level,
+			trace_rcu_exp_funnel_lock(rcu_state.name, rnp->level,
 						  rnp->grplo, rnp->grphi,
 						  TPS("wait"));
 			wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3],
-				   sync_exp_work_done(rsp, s));
+				   sync_exp_work_done(s));
 			return true;
 		}
 		rnp->exp_seq_rq = s; /* Followers can wait on us. */
 		spin_unlock(&rnp->exp_lock);
-		trace_rcu_exp_funnel_lock(rsp->name, rnp->level, rnp->grplo,
+		trace_rcu_exp_funnel_lock(rcu_state.name, rnp->level,
-					  rnp->grphi, TPS("nxtlvl"));
+					  rnp->grplo, rnp->grphi, TPS("nxtlvl"));
 	}
-	mutex_lock(&rsp->exp_mutex);
+	mutex_lock(&rcu_state.exp_mutex);
 fastpath:
-	if (sync_exp_work_done(rsp, s)) {
+	if (sync_exp_work_done(s)) {
-		mutex_unlock(&rsp->exp_mutex);
+		mutex_unlock(&rcu_state.exp_mutex);
 		return true;
 	}
-	rcu_exp_gp_seq_start(rsp);
+	rcu_exp_gp_seq_start();
-	trace_rcu_exp_grace_period(rsp->name, s, TPS("start"));
+	trace_rcu_exp_grace_period(rcu_state.name, s, TPS("start"));
 	return false;
 }
 
-/* Invoked on each online non-idle CPU for expedited quiescent state. */
-static void sync_sched_exp_handler(void *data)
-{
-	struct rcu_data *rdp;
-	struct rcu_node *rnp;
-	struct rcu_state *rsp = data;
-
-	rdp = this_cpu_ptr(rsp->rda);
-	rnp = rdp->mynode;
-	if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
-	    __this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))
-		return;
-	if (rcu_is_cpu_rrupt_from_idle()) {
-		rcu_report_exp_rdp(&rcu_sched_state,
-				   this_cpu_ptr(&rcu_sched_data), true);
-		return;
-	}
-	__this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, true);
-	/* Store .exp before .rcu_urgent_qs. */
-	smp_store_release(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs), true);
-	resched_cpu(smp_processor_id());
-}
-
-/* Send IPI for expedited cleanup if needed at end of CPU-hotplug operation. */
-static void sync_sched_exp_online_cleanup(int cpu)
-{
-	struct rcu_data *rdp;
-	int ret;
-	struct rcu_node *rnp;
-	struct rcu_state *rsp = &rcu_sched_state;
-
-	rdp = per_cpu_ptr(rsp->rda, cpu);
-	rnp = rdp->mynode;
-	if (!(READ_ONCE(rnp->expmask) & rdp->grpmask))
-		return;
-	ret = smp_call_function_single(cpu, sync_sched_exp_handler, rsp, 0);
-	WARN_ON_ONCE(ret);
-}
-
 /*
  * Select the CPUs within the specified rcu_node that the upcoming
  * expedited grace period needs to wait for.
@@ -391,7 +351,6 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
 	struct rcu_exp_work *rewp =
 		container_of(wp, struct rcu_exp_work, rew_work);
 	struct rcu_node *rnp = container_of(rewp, struct rcu_node, rew);
-	struct rcu_state *rsp = rewp->rew_rsp;
 
 	func = rewp->rew_func;
 	raw_spin_lock_irqsave_rcu_node(rnp, flags);
@@ -400,15 +359,14 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
 	mask_ofl_test = 0;
 	for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
 		unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
-		struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
+		struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
-		struct rcu_dynticks *rdtp = per_cpu_ptr(&rcu_dynticks, cpu);
 		int snap;
 
 		if (raw_smp_processor_id() == cpu ||
 		    !(rnp->qsmaskinitnext & mask)) {
 			mask_ofl_test |= mask;
 		} else {
-			snap = rcu_dynticks_snap(rdtp);
+			snap = rcu_dynticks_snap(rdp);
 			if (rcu_dynticks_in_eqs(snap))
 				mask_ofl_test |= mask;
 			else
@@ -429,17 +387,16 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
 	/* IPI the remaining CPUs for expedited quiescent state. */
 	for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
 		unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
-		struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
+		struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
 
 		if (!(mask_ofl_ipi & mask))
 			continue;
 retry_ipi:
-		if (rcu_dynticks_in_eqs_since(rdp->dynticks,
+		if (rcu_dynticks_in_eqs_since(rdp, rdp->exp_dynticks_snap)) {
-					      rdp->exp_dynticks_snap)) {
 			mask_ofl_test |= mask;
 			continue;
 		}
-		ret = smp_call_function_single(cpu, func, rsp, 0);
+		ret = smp_call_function_single(cpu, func, NULL, 0);
 		if (!ret) {
 			mask_ofl_ipi &= ~mask;
 			continue;
@@ -450,7 +407,7 @@ retry_ipi:
 		    (rnp->expmask & mask)) {
 			/* Online, so delay for a bit and try again. */
 			raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
-			trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("selectofl"));
+			trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("selectofl"));
 			schedule_timeout_uninterruptible(1);
 			goto retry_ipi;
 		}
@@ -462,33 +419,31 @@ retry_ipi:
 	/* Report quiescent states for those that went offline. */
 	mask_ofl_test |= mask_ofl_ipi;
 	if (mask_ofl_test)
-		rcu_report_exp_cpu_mult(rsp, rnp, mask_ofl_test, false);
+		rcu_report_exp_cpu_mult(rnp, mask_ofl_test, false);
 }
 
 /*
  * Select the nodes that the upcoming expedited grace period needs
  * to wait for.
  */
-static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
+static void sync_rcu_exp_select_cpus(smp_call_func_t func)
-				     smp_call_func_t func)
 {
 	int cpu;
 	struct rcu_node *rnp;
 
-	trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("reset"));
+	trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("reset"));
-	sync_exp_reset_tree(rsp);
+	sync_exp_reset_tree();
-	trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("select"));
+	trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("select"));
 
 	/* Schedule work for each leaf rcu_node structure. */
-	rcu_for_each_leaf_node(rsp, rnp) {
+	rcu_for_each_leaf_node(rnp) {
 		rnp->exp_need_flush = false;
 		if (!READ_ONCE(rnp->expmask))
 			continue; /* Avoid early boot non-existent wq. */
 		rnp->rew.rew_func = func;
-		rnp->rew.rew_rsp = rsp;
 		if (!READ_ONCE(rcu_par_gp_wq) ||
 		    rcu_scheduler_active != RCU_SCHEDULER_RUNNING ||
-		    rcu_is_last_leaf_node(rsp, rnp)) {
+		    rcu_is_last_leaf_node(rnp)) {
 			/* No workqueues yet or last leaf, do direct call. */
 			sync_rcu_exp_select_node_cpus(&rnp->rew.rew_work);
 			continue;
@@ -505,12 +460,12 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
 	}
 
 	/* Wait for workqueue jobs (if any) to complete. */
-	rcu_for_each_leaf_node(rsp, rnp)
+	rcu_for_each_leaf_node(rnp)
 		if (rnp->exp_need_flush)
 			flush_work(&rnp->rew.rew_work);
 }
 
-static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
+static void synchronize_sched_expedited_wait(void)
 {
 	int cpu;
 	unsigned long jiffies_stall;
@@ -518,16 +473,16 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
 	unsigned long mask;
 	int ndetected;
 	struct rcu_node *rnp;
-	struct rcu_node *rnp_root = rcu_get_root(rsp);
+	struct rcu_node *rnp_root = rcu_get_root();
 	int ret;
 
-	trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("startwait"));
+	trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("startwait"));
 	jiffies_stall = rcu_jiffies_till_stall_check();
 	jiffies_start = jiffies;
 
 	for (;;) {
 		ret = swait_event_timeout_exclusive(
-				rsp->expedited_wq,
+				rcu_state.expedited_wq,
 				sync_rcu_preempt_exp_done_unlocked(rnp_root),
 				jiffies_stall);
 		if (ret > 0 || sync_rcu_preempt_exp_done_unlocked(rnp_root))
@@ -537,9 +492,9 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
 			continue;
 		panic_on_rcu_stall();
 		pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {",
-		       rsp->name);
+		       rcu_state.name);
 		ndetected = 0;
-		rcu_for_each_leaf_node(rsp, rnp) {
+		rcu_for_each_leaf_node(rnp) {
 			ndetected += rcu_print_task_exp_stall(rnp);
 			for_each_leaf_node_possible_cpu(rnp, cpu) {
 				struct rcu_data *rdp;
@@ -548,7 +503,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
 				if (!(rnp->expmask & mask))
 					continue;
 				ndetected++;
-				rdp = per_cpu_ptr(rsp->rda, cpu);
+				rdp = per_cpu_ptr(&rcu_data, cpu);
 				pr_cont(" %d-%c%c%c", cpu,
 					"O."[!!cpu_online(cpu)],
 					"o."[!!(rdp->grpmask & rnp->expmaskinit)],
@@ -556,11 +511,11 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
 			}
 		}
 		pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",
-			jiffies - jiffies_start, rsp->expedited_sequence,
+			jiffies - jiffies_start, rcu_state.expedited_sequence,
 			rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]);
 		if (ndetected) {
 			pr_err("blocking rcu_node structures:");
-			rcu_for_each_node_breadth_first(rsp, rnp) {
+			rcu_for_each_node_breadth_first(rnp) {
 				if (rnp == rnp_root)
 					continue; /* printed unconditionally */
 				if (sync_rcu_preempt_exp_done_unlocked(rnp))
@@ -572,7 +527,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
 			}
 			pr_cont("\n");
 		}
-		rcu_for_each_leaf_node(rsp, rnp) {
+		rcu_for_each_leaf_node(rnp) {
 			for_each_leaf_node_possible_cpu(rnp, cpu) {
 				mask = leaf_node_cpu_bit(rnp, cpu);
 				if (!(rnp->expmask & mask))
@@ -590,21 +545,21 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
  * grace period.  Also update all the ->exp_seq_rq counters as needed
  * in order to avoid counter-wrap problems.
  */
-static void rcu_exp_wait_wake(struct rcu_state *rsp, unsigned long s)
+static void rcu_exp_wait_wake(unsigned long s)
 {
 	struct rcu_node *rnp;
 
-	synchronize_sched_expedited_wait(rsp);
+	synchronize_sched_expedited_wait();
-	rcu_exp_gp_seq_end(rsp);
+	rcu_exp_gp_seq_end();
-	trace_rcu_exp_grace_period(rsp->name, s, TPS("end"));
+	trace_rcu_exp_grace_period(rcu_state.name, s, TPS("end"));
 
 	/*
 	 * Switch over to wakeup mode, allowing the next GP, but -only- the
 	 * next GP, to proceed.
 	 */
-	mutex_lock(&rsp->exp_wake_mutex);
+	mutex_lock(&rcu_state.exp_wake_mutex);
 
-	rcu_for_each_node_breadth_first(rsp, rnp) {
+	rcu_for_each_node_breadth_first(rnp) {
 		if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s)) {
 			spin_lock(&rnp->exp_lock);
 			/* Recheck, avoid hang in case someone just arrived. */
@@ -613,24 +568,23 @@ static void rcu_exp_wait_wake(struct rcu_state *rsp, unsigned long s)
 			spin_unlock(&rnp->exp_lock);
 		}
 		smp_mb(); /* All above changes before wakeup. */
-		wake_up_all(&rnp->exp_wq[rcu_seq_ctr(rsp->expedited_sequence) & 0x3]);
+		wake_up_all(&rnp->exp_wq[rcu_seq_ctr(rcu_state.expedited_sequence) & 0x3]);
 	}
-	trace_rcu_exp_grace_period(rsp->name, s, TPS("endwake"));
+	trace_rcu_exp_grace_period(rcu_state.name, s, TPS("endwake"));
-	mutex_unlock(&rsp->exp_wake_mutex);
+	mutex_unlock(&rcu_state.exp_wake_mutex);
 }
 
 /*
  * Common code to drive an expedited grace period forward, used by
  * workqueues and mid-boot-time tasks.
  */
-static void rcu_exp_sel_wait_wake(struct rcu_state *rsp,
+static void rcu_exp_sel_wait_wake(smp_call_func_t func, unsigned long s)
-				  smp_call_func_t func, unsigned long s)
 {
 	/* Initialize the rcu_node tree in preparation for the wait. */
-	sync_rcu_exp_select_cpus(rsp, func);
+	sync_rcu_exp_select_cpus(func);
 
 	/* Wait and clean up, including waking everyone. */
-	rcu_exp_wait_wake(rsp, s);
+	rcu_exp_wait_wake(s);
 }
 
 /*
@@ -641,15 +595,14 @@ static void wait_rcu_exp_gp(struct work_struct *wp)
 	struct rcu_exp_work *rewp;
 
 	rewp = container_of(wp, struct rcu_exp_work, rew_work);
-	rcu_exp_sel_wait_wake(rewp->rew_rsp, rewp->rew_func, rewp->rew_s);
+	rcu_exp_sel_wait_wake(rewp->rew_func, rewp->rew_s);
 }
 
 /*
- * Given an rcu_state pointer and a smp_call_function() handler, kick
+ * Given a smp_call_function() handler, kick off the specified
- * off the specified flavor of expedited grace period.
+ * implementation of expedited grace period.
  */
-static void _synchronize_rcu_expedited(struct rcu_state *rsp,
+static void _synchronize_rcu_expedited(smp_call_func_t func)
-				       smp_call_func_t func)
 {
 	struct rcu_data *rdp;
 	struct rcu_exp_work rew;
@@ -658,72 +611,38 @@ static void _synchronize_rcu_expedited(struct rcu_state *rsp,
 
 	/* If expedited grace periods are prohibited, fall back to normal. */
 	if (rcu_gp_is_normal()) {
-		wait_rcu_gp(rsp->call);
+		wait_rcu_gp(call_rcu);
 		return;
 	}
 
 	/* Take a snapshot of the sequence number.  */
-	s = rcu_exp_gp_seq_snap(rsp);
+	s = rcu_exp_gp_seq_snap();
-	if (exp_funnel_lock(rsp, s))
+	if (exp_funnel_lock(s))
 		return;  /* Someone else did our work for us. */
 
 	/* Ensure that load happens before action based on it. */
 	if (unlikely(rcu_scheduler_active == RCU_SCHEDULER_INIT)) {
 		/* Direct call during scheduler init and early_initcalls(). */
-		rcu_exp_sel_wait_wake(rsp, func, s);
+		rcu_exp_sel_wait_wake(func, s);
 	} else {
 		/* Marshall arguments & schedule the expedited grace period. */
 		rew.rew_func = func;
-		rew.rew_rsp = rsp;
 		rew.rew_s = s;
 		INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp);
 		queue_work(rcu_gp_wq, &rew.rew_work);
 	}
 
 	/* Wait for expedited grace period to complete. */
-	rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id());
+	rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id());
-	rnp = rcu_get_root(rsp);
+	rnp = rcu_get_root();
 	wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3],
-		   sync_exp_work_done(rsp, s));
+		   sync_exp_work_done(s));
 	smp_mb(); /* Workqueue actions happen before return. */
 
 	/* Let the next expedited grace period start. */
-	mutex_unlock(&rsp->exp_mutex);
+	mutex_unlock(&rcu_state.exp_mutex);
 }
 
-/**
- * synchronize_sched_expedited - Brute-force RCU-sched grace period
- *
- * Wait for an RCU-sched grace period to elapse, but use a "big hammer"
- * approach to force the grace period to end quickly.  This consumes
- * significant time on all CPUs and is unfriendly to real-time workloads,
- * so is thus not recommended for any sort of common-case code.  In fact,
- * if you are using synchronize_sched_expedited() in a loop, please
- * restructure your code to batch your updates, and then use a single
- * synchronize_sched() instead.
- *
- * This implementation can be thought of as an application of sequence
- * locking to expedited grace periods, but using the sequence counter to
- * determine when someone else has already done the work instead of for
- * retrying readers.
- */
-void synchronize_sched_expedited(void)
-{
-	struct rcu_state *rsp = &rcu_sched_state;
-
-	RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
-			 lock_is_held(&rcu_lock_map) ||
-			 lock_is_held(&rcu_sched_lock_map),
-			 "Illegal synchronize_sched_expedited() in RCU read-side critical section");
-
-	/* If only one CPU, this is automatically a grace period. */
-	if (rcu_blocking_is_gp())
-		return;
-
-	_synchronize_rcu_expedited(rsp, sync_sched_exp_handler);
-}
-EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
-
 #ifdef CONFIG_PREEMPT_RCU
 
 /*
@@ -733,34 +652,78 @@ EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
  * ->expmask fields in the rcu_node tree.  Otherwise, immediately
  * report the quiescent state.
  */
-static void sync_rcu_exp_handler(void *info)
+static void sync_rcu_exp_handler(void *unused)
 {
-	struct rcu_data *rdp;
+	unsigned long flags;
-	struct rcu_state *rsp = info;
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+	struct rcu_node *rnp = rdp->mynode;
 	struct task_struct *t = current;
 
 	/*
-	 * Within an RCU read-side critical section, request that the next
+	 * First, the common case of not being in an RCU read-side
-	 * rcu_read_unlock() report.  Unless this RCU read-side critical
+	 * critical section.  If also enabled or idle, immediately
-	 * section has already blocked, in which case it is already set
+	 * report the quiescent state, otherwise defer.
-	 * up for the expedited grace period to wait on it.
 	 */
-	if (t->rcu_read_lock_nesting > 0 &&
+	if (!t->rcu_read_lock_nesting) {
-	    !t->rcu_read_unlock_special.b.blocked) {
+		if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) ||
-		t->rcu_read_unlock_special.b.exp_need_qs = true;
+		    rcu_dynticks_curr_cpu_in_eqs()) {
+			rcu_report_exp_rdp(rdp);
+		} else {
+			rdp->deferred_qs = true;
+			set_tsk_need_resched(t);
+			set_preempt_need_resched();
+		}
 		return;
 	}
 
 	/*
-	 * We are either exiting an RCU read-side critical section (negative
+	 * Second, the less-common case of being in an RCU read-side
-	 * values of t->rcu_read_lock_nesting) or are not in one at all
+	 * critical section.  In this case we can count on a future
-	 * (zero value of t->rcu_read_lock_nesting).  Or we are in an RCU
+	 * rcu_read_unlock().  However, this rcu_read_unlock() might
-	 * read-side critical section that blocked before this expedited
+	 * execute on some other CPU, but in that case there will be
-	 * grace period started.  Either way, we can immediately report
+	 * a future context switch.  Either way, if the expedited
-	 * the quiescent state.
+	 * grace period is still waiting on this CPU, set ->deferred_qs
+	 * so that the eventual quiescent state will be reported.
+	 * Note that there is a large group of race conditions that
+	 * can have caused this quiescent state to already have been
+	 * reported, so we really do need to check ->expmask.
 	 */
-	rdp = this_cpu_ptr(rsp->rda);
+	if (t->rcu_read_lock_nesting > 0) {
-	rcu_report_exp_rdp(rsp, rdp, true);
+		raw_spin_lock_irqsave_rcu_node(rnp, flags);
+		if (rnp->expmask & rdp->grpmask)
+			rdp->deferred_qs = true;
+		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+	}
+
+	/*
+	 * The final and least likely case is where the interrupted
+	 * code was just about to or just finished exiting the RCU-preempt
+	 * read-side critical section, and no, we can't tell which.
+	 * So either way, set ->deferred_qs to flag later code that
+	 * a quiescent state is required.
+	 *
+	 * If the CPU is fully enabled (or if some buggy RCU-preempt
+	 * read-side critical section is being used from idle), just
+	 * invoke rcu_preempt_defer_qs() to immediately report the
+	 * quiescent state.  We cannot use rcu_read_unlock_special()
+	 * because we are in an interrupt handler, which will cause that
+	 * function to take an early exit without doing anything.
+	 *
+	 * Otherwise, force a context switch after the CPU enables everything.
+	 */
+	rdp->deferred_qs = true;
+	if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) ||
+	    WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs())) {
+		rcu_preempt_deferred_qs(t);
+	} else {
+		set_tsk_need_resched(t);
+		set_preempt_need_resched();
+	}
+}
+
+/* PREEMPT=y, so no PREEMPT=n expedited grace period to clean up after. */
+static void sync_sched_exp_online_cleanup(int cpu)
+{
 }
 
 /**
@@ -780,11 +743,11 @@ static void sync_rcu_exp_handler(void *info)
  * you are using synchronize_rcu_expedited() in a loop, please restructure
  * your code to batch your updates, and then Use a single synchronize_rcu()
  * instead.
+ *
+ * This has the same semantics as (but is more brutal than) synchronize_rcu().
  */
 void synchronize_rcu_expedited(void)
 {
-	struct rcu_state *rsp = rcu_state_p;
-
 	RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
 			 lock_is_held(&rcu_lock_map) ||
 			 lock_is_held(&rcu_sched_lock_map),
@@ -792,19 +755,82 @@ void synchronize_rcu_expedited(void)
 
 	if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
 		return;
-	_synchronize_rcu_expedited(rsp, sync_rcu_exp_handler);
+	_synchronize_rcu_expedited(sync_rcu_exp_handler);
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
 
 #else /* #ifdef CONFIG_PREEMPT_RCU */
 
+/* Invoked on each online non-idle CPU for expedited quiescent state. */
+static void sync_sched_exp_handler(void *unused)
+{
+	struct rcu_data *rdp;
+	struct rcu_node *rnp;
+
+	rdp = this_cpu_ptr(&rcu_data);
+	rnp = rdp->mynode;
+	if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
+	    __this_cpu_read(rcu_data.cpu_no_qs.b.exp))
+		return;
+	if (rcu_is_cpu_rrupt_from_idle()) {
+		rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
+		return;
+	}
+	__this_cpu_write(rcu_data.cpu_no_qs.b.exp, true);
+	/* Store .exp before .rcu_urgent_qs. */
+	smp_store_release(this_cpu_ptr(&rcu_data.rcu_urgent_qs), true);
+	set_tsk_need_resched(current);
+	set_preempt_need_resched();
+}
+
+/* Send IPI for expedited cleanup if needed at end of CPU-hotplug operation. */
+static void sync_sched_exp_online_cleanup(int cpu)
+{
+	struct rcu_data *rdp;
+	int ret;
+	struct rcu_node *rnp;
+
+	rdp = per_cpu_ptr(&rcu_data, cpu);
+	rnp = rdp->mynode;
+	if (!(READ_ONCE(rnp->expmask) & rdp->grpmask))
+		return;
+	ret = smp_call_function_single(cpu, sync_sched_exp_handler, NULL, 0);
+	WARN_ON_ONCE(ret);
+}
+
 /*
- * Wait for an rcu-preempt grace period, but make it happen quickly.
+ * Because a context switch is a grace period for !PREEMPT, any
- * But because preemptible RCU does not exist, map to rcu-sched.
+ * blocking grace-period wait automatically implies a grace period if
+ * there is only one CPU online at any point time during execution of
+ * either synchronize_rcu() or synchronize_rcu_expedited().  It is OK to
+ * occasionally incorrectly indicate that there are multiple CPUs online
+ * when there was in fact only one the whole time, as this just adds some
+ * overhead: RCU still operates correctly.
  */
+static int rcu_blocking_is_gp(void)
+{
+	int ret;
+
+	might_sleep();  /* Check for RCU read-side critical section. */
+	preempt_disable();
+	ret = num_online_cpus() <= 1;
+	preempt_enable();
+	return ret;
+}
+
+/* PREEMPT=n implementation of synchronize_rcu_expedited(). */
 void synchronize_rcu_expedited(void)
 {
-	synchronize_sched_expedited();
+	RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
+			 lock_is_held(&rcu_lock_map) ||
+			 lock_is_held(&rcu_sched_lock_map),
+			 "Illegal synchronize_rcu_expedited() in RCU read-side critical section");
+
+	/* If only one CPU, this is automatically a grace period. */
+	if (rcu_blocking_is_gp())
+		return;
+
+	_synchronize_rcu_expedited(sync_sched_exp_handler);
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
 

kernel/rcu/update.c

@@ -203,11 +203,7 @@ void rcu_test_sync_prims(void)
 	if (!IS_ENABLED(CONFIG_PROVE_RCU))
 		return;
 	synchronize_rcu();
-	synchronize_rcu_bh();
-	synchronize_sched();
 	synchronize_rcu_expedited();
-	synchronize_rcu_bh_expedited();
-	synchronize_sched_expedited();
 }
 
 #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU)
@@ -298,7 +294,7 @@ EXPORT_SYMBOL_GPL(rcu_read_lock_held);
  *
  * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
  *
- * Note that rcu_read_lock() is disallowed if the CPU is either idle or
+ * Note that rcu_read_lock_bh() is disallowed if the CPU is either idle or
  * offline from an RCU perspective, so check for those as well.
  */
 int rcu_read_lock_bh_held(void)
@@ -336,7 +332,7 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
 	int i;
 	int j;
 
-	/* Initialize and register callbacks for each flavor specified. */
+	/* Initialize and register callbacks for each crcu_array element. */
 	for (i = 0; i < n; i++) {
 		if (checktiny &&
 		    (crcu_array[i] == call_rcu ||
@@ -472,6 +468,7 @@ int rcu_jiffies_till_stall_check(void)
 	}
 	return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
 }
+EXPORT_SYMBOL_GPL(rcu_jiffies_till_stall_check);
 
 void rcu_sysrq_start(void)
 {
@@ -701,19 +698,19 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 
 		/*
 		 * Wait for all pre-existing t->on_rq and t->nvcsw
-		 * transitions to complete.  Invoking synchronize_sched()
+		 * transitions to complete.  Invoking synchronize_rcu()
 		 * suffices because all these transitions occur with
-		 * interrupts disabled.  Without this synchronize_sched(),
+		 * interrupts disabled.  Without this synchronize_rcu(),
 		 * a read-side critical section that started before the
 		 * grace period might be incorrectly seen as having started
 		 * after the grace period.
 		 *
-		 * This synchronize_sched() also dispenses with the
+		 * This synchronize_rcu() also dispenses with the
 		 * need for a memory barrier on the first store to
 		 * ->rcu_tasks_holdout, as it forces the store to happen
 		 * after the beginning of the grace period.
 		 */
-		synchronize_sched();
+		synchronize_rcu();
 
 		/*
 		 * There were callbacks, so we need to wait for an
@@ -740,7 +737,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 		 * This does only part of the job, ensuring that all
 		 * tasks that were previously exiting reach the point
 		 * where they have disabled preemption, allowing the
-		 * later synchronize_sched() to finish the job.
+		 * later synchronize_rcu() to finish the job.
 		 */
 		synchronize_srcu(&tasks_rcu_exit_srcu);
 
@@ -790,20 +787,20 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 		 * cause their RCU-tasks read-side critical sections to
 		 * extend past the end of the grace period.  However,
 		 * because these ->nvcsw updates are carried out with
-		 * interrupts disabled, we can use synchronize_sched()
+		 * interrupts disabled, we can use synchronize_rcu()
 		 * to force the needed ordering on all such CPUs.
 		 *
-		 * This synchronize_sched() also confines all
+		 * This synchronize_rcu() also confines all
 		 * ->rcu_tasks_holdout accesses to be within the grace
 		 * period, avoiding the need for memory barriers for
 		 * ->rcu_tasks_holdout accesses.
 		 *
-		 * In addition, this synchronize_sched() waits for exiting
+		 * In addition, this synchronize_rcu() waits for exiting
 		 * tasks to complete their final preempt_disable() region
 		 * of execution, cleaning up after the synchronize_srcu()
 		 * above.
 		 */
-		synchronize_sched();
+		synchronize_rcu();
 
 		/* Invoke the callbacks. */
 		while (list) {
@@ -870,15 +867,10 @@ static void __init rcu_tasks_bootup_oddness(void)
 #ifdef CONFIG_PROVE_RCU
 
 /*
- * Early boot self test parameters, one for each flavor
+ * Early boot self test parameters.
  */
 static bool rcu_self_test;
-static bool rcu_self_test_bh;
-static bool rcu_self_test_sched;
-
 module_param(rcu_self_test, bool, 0444);
-module_param(rcu_self_test_bh, bool, 0444);
-module_param(rcu_self_test_sched, bool, 0444);
 
 static int rcu_self_test_counter;
 
@@ -888,25 +880,16 @@ static void test_callback(struct rcu_head *r)
 	pr_info("RCU test callback executed %d\n", rcu_self_test_counter);
 }
 
+DEFINE_STATIC_SRCU(early_srcu);
+
 static void early_boot_test_call_rcu(void)
 {
 	static struct rcu_head head;
+	static struct rcu_head shead;
 
 	call_rcu(&head, test_callback);
-}
+	if (IS_ENABLED(CONFIG_SRCU))
-
+		call_srcu(&early_srcu, &shead, test_callback);
-static void early_boot_test_call_rcu_bh(void)
-{
-	static struct rcu_head head;
-
-	call_rcu_bh(&head, test_callback);
-}
-
-static void early_boot_test_call_rcu_sched(void)
-{
-	static struct rcu_head head;
-
-	call_rcu_sched(&head, test_callback);
 }
 
 void rcu_early_boot_tests(void)
@@ -915,10 +898,6 @@ void rcu_early_boot_tests(void)
 
 	if (rcu_self_test)
 		early_boot_test_call_rcu();
-	if (rcu_self_test_bh)
-		early_boot_test_call_rcu_bh();
-	if (rcu_self_test_sched)
-		early_boot_test_call_rcu_sched();
 	rcu_test_sync_prims();
 }
 
@@ -930,16 +909,11 @@ static int rcu_verify_early_boot_tests(void)
 	if (rcu_self_test) {
 		early_boot_test_counter++;
 		rcu_barrier();
+		if (IS_ENABLED(CONFIG_SRCU)) {
+			early_boot_test_counter++;
+			srcu_barrier(&early_srcu);
+		}
 	}
-	if (rcu_self_test_bh) {
-		early_boot_test_counter++;
-		rcu_barrier_bh();
-	}
-	if (rcu_self_test_sched) {
-		early_boot_test_counter++;
-		rcu_barrier_sched();
-	}
-
 	if (rcu_self_test_counter != early_boot_test_counter) {
 		WARN_ON(1);
 		ret = -1;

kernel/softirq.c

@@ -301,7 +301,8 @@ restart:
 		pending >>= softirq_bit;
 	}
 
-	rcu_bh_qs();
+	if (__this_cpu_read(ksoftirqd) == current)
+		rcu_softirq_qs();
 	local_irq_disable();
 
 	pending = local_softirq_pending();

kernel/torture.c

@@ -573,7 +573,7 @@ static int stutter;
  * Block until the stutter interval ends.  This must be called periodically
  * by all running kthreads that need to be subject to stuttering.
  */
-void stutter_wait(const char *title)
+bool stutter_wait(const char *title)
 {
 	int spt;
 
@@ -590,6 +590,7 @@ void stutter_wait(const char *title)
 		}
 		torture_shutdown_absorb(title);
 	}
+	return !!spt;
 }
 EXPORT_SYMBOL_GPL(stutter_wait);
 

tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh

@@ -120,7 +120,6 @@ then
 	parse-build.sh $resdir/Make.out $title
 else
 	# Build failed.
-	cp $builddir/Make*.out $resdir
 	cp $builddir/.config $resdir || :
 	echo Build failed, not running KVM, see $resdir.
 	if test -f $builddir.wait

tools/testing/selftests/rcutorture/configs/rcu/CFLIST

@@ -3,9 +3,7 @@ TREE02
 TREE03
 TREE04
 TREE05
-TREE06
 TREE07
-TREE08
 TREE09
 SRCU-N
 SRCU-P

tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot

@@ -1 +1,2 @@
 rcutorture.torture_type=srcud
+rcupdate.rcu_self_test=1

tools/testing/selftests/rcutorture/configs/rcu/SRCU-u.boot

@@ -1 +1,2 @@
 rcutorture.torture_type=srcud
+rcupdate.rcu_self_test=1

tools/testing/selftests/rcutorture/configs/rcu/TINY02.boot

@@ -1,3 +1 @@
 rcupdate.rcu_self_test=1
-rcupdate.rcu_self_test_bh=1
-rcutorture.torture_type=rcu_bh

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

@@ -1,4 +1,4 @@
-rcutorture.torture_type=rcu_bh maxcpus=8 nr_cpus=43
+maxcpus=8 nr_cpus=43
 rcutree.gp_preinit_delay=3
 rcutree.gp_init_delay=3
 rcutree.gp_cleanup_delay=3

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

@@ -1 +1 @@
-rcutorture.torture_type=rcu_bh rcutree.rcu_fanout_leaf=4 nohz_full=1-7
+rcutree.rcu_fanout_leaf=4 nohz_full=1-7

tools/testing/selftests/rcutorture/configs/rcu/TREE05.boot

@@ -1,5 +1,4 @@
-rcutorture.torture_type=sched
-rcupdate.rcu_self_test_sched=1
 rcutree.gp_preinit_delay=3
 rcutree.gp_init_delay=3
 rcutree.gp_cleanup_delay=3
+rcupdate.rcu_self_test=1

tools/testing/selftests/rcutorture/configs/rcu/TREE06.boot

@@ -1,6 +1,4 @@
 rcupdate.rcu_self_test=1
-rcupdate.rcu_self_test_bh=1
-rcupdate.rcu_self_test_sched=1
 rcutree.rcu_fanout_exact=1
 rcutree.gp_preinit_delay=3
 rcutree.gp_init_delay=3

tools/testing/selftests/rcutorture/configs/rcu/TREE08.boot

@@ -1,5 +1,3 @@
-rcutorture.torture_type=sched
 rcupdate.rcu_self_test=1
-rcupdate.rcu_self_test_sched=1
 rcutree.rcu_fanout_exact=1
 rcu_nocbs=0-7