Merge branches 'docs.2022.04.20a', 'fixes.2022.04.20a', 'nocb.2022.04.11b',...

Merge branches 'docs.2022.04.20a', 'fixes.2022.04.20a', 'nocb.2022.04.11b', 'rcu-tasks.2022.04.11b', 'srcu.2022.05.03a', 'torture.2022.04.11b', 'torture-tasks.2022.04.20a' and 'torturescript.2022.04.20a' into HEAD

docs.2022.04.20a: Documentation updates.
fixes.2022.04.20a: Miscellaneous fixes.
nocb.2022.04.11b: Callback-offloading updates.
rcu-tasks.2022.04.11b: RCU-tasks updates.
srcu.2022.05.03a: Put SRCU on a memory diet.
torture.2022.04.11b: Torture-test updates.
torture-tasks.2022.04.20a: Avoid torture testing changing RCU configuration.
torturescript.2022.04.20a: Torture-test scripting updates.

Documentation/admin-guide/kernel-parameters.txt

@@ -4955,10 +4955,34 @@
 			number avoids disturbing real-time workloads,
 			but lengthens grace periods.
 
+	rcupdate.rcu_task_stall_info= [KNL]
+			Set initial timeout in jiffies for RCU task stall
+			informational messages, which give some indication
+			of the problem for those not patient enough to
+			wait for ten minutes.  Informational messages are
+			only printed prior to the stall-warning message
+			for a given grace period. Disable with a value
+			less than or equal to zero.  Defaults to ten
+			seconds.  A change in value does not take effect
+			until the beginning of the next grace period.
+
+	rcupdate.rcu_task_stall_info_mult= [KNL]
+			Multiplier for time interval between successive
+			RCU task stall informational messages for a given
+			RCU tasks grace period.  This value is clamped
+			to one through ten, inclusive.	It defaults to
+			the value three, so that the first informational
+			message is printed 10 seconds into the grace
+			period, the second at 40 seconds, the third at
+			160 seconds, and then the stall warning at 600
+			seconds would prevent a fourth at 640 seconds.
+
 	rcupdate.rcu_task_stall_timeout= [KNL]
-			Set timeout in jiffies for RCU task stall warning
-			messages.  Disable with a value less than or equal
-			to zero.
+			Set timeout in jiffies for RCU task stall
+			warning messages.  Disable with a value less
+			than or equal to zero.	Defaults to ten minutes.
+			A change in value does not take effect until
+			the beginning of the next grace period.
 
 	rcupdate.rcu_self_test= [KNL]
 			Run the RCU early boot self tests
@@ -5377,6 +5401,17 @@
 	smart2=		[HW]
 			Format: <io1>[,<io2>[,...,<io8>]]
 
+	smp.csd_lock_timeout= [KNL]
+			Specify the period of time in milliseconds
+			that smp_call_function() and friends will wait
+			for a CPU to release the CSD lock.  This is
+			useful when diagnosing bugs involving CPUs
+			disabling interrupts for extended periods
+			of time.  Defaults to 5,000 milliseconds, and
+			setting a value of zero disables this feature.
+			This feature may be more efficiently disabled
+			using the csdlock_debug- kernel parameter.
+
 	smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
 	smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
 	smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
@@ -5608,6 +5643,30 @@
 			off:    Disable mitigation and remove
 				performance impact to RDRAND and RDSEED
 
+	srcutree.big_cpu_lim [KNL]
+			Specifies the number of CPUs constituting a
+			large system, such that srcu_struct structures
+			should immediately allocate an srcu_node array.
+			This kernel-boot parameter defaults to 128,
+			but takes effect only when the low-order four
+			bits of srcutree.convert_to_big is equal to 3
+			(decide at boot).
+
+	srcutree.convert_to_big [KNL]
+			Specifies under what conditions an SRCU tree
+			srcu_struct structure will be converted to big
+			form, that is, with an rcu_node tree:
+
+				   0:  Never.
+				   1:  At init_srcu_struct() time.
+				   2:  When rcutorture decides to.
+				   3:  Decide at boot time (default).
+				0x1X:  Above plus if high contention.
+
+			Either way, the srcu_node tree will be sized based
+			on the actual runtime number of CPUs (nr_cpu_ids)
+			instead of the compile-time CONFIG_NR_CPUS.
+
 	srcutree.counter_wrap_check [KNL]
 			Specifies how frequently to check for
 			grace-period sequence counter wrap for the
@@ -5625,6 +5684,14 @@
 			expediting.  Set to zero to disable automatic
 			expediting.
 
+	srcutree.small_contention_lim [KNL]
+			Specifies the number of update-side contention
+			events per jiffy will be tolerated before
+			initiating a conversion of an srcu_struct
+			structure to big form.	Note that the value of
+			srcutree.convert_to_big must have the 0x10 bit
+			set for contention-based conversions to occur.
+
 	ssbd=		[ARM64,HW]
 			Speculative Store Bypass Disable control
 

arch/Kconfig

@@ -35,6 +35,7 @@ config KPROBES
 	depends on MODULES
 	depends on HAVE_KPROBES
 	select KALLSYMS
+	select TASKS_RCU if PREEMPTION
 	help
 	  Kprobes allows you to trap at almost any kernel address and
 	  execute a callback function.  register_kprobe() establishes

include/linux/rcupdate.h

@@ -196,6 +196,7 @@ void synchronize_rcu_tasks_rude(void);
 void exit_tasks_rcu_start(void);
 void exit_tasks_rcu_finish(void);
 #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
+#define rcu_tasks_classic_qs(t, preempt) do { } while (0)
 #define rcu_tasks_qs(t, preempt) do { } while (0)
 #define rcu_note_voluntary_context_switch(t) do { } while (0)
 #define call_rcu_tasks call_rcu

include/linux/sched.h

@@ -2117,6 +2117,47 @@ static inline void cond_resched_rcu(void)
 #endif
 }
 
+#ifdef CONFIG_PREEMPT_DYNAMIC
+
+extern bool preempt_model_none(void);
+extern bool preempt_model_voluntary(void);
+extern bool preempt_model_full(void);
+
+#else
+
+static inline bool preempt_model_none(void)
+{
+	return IS_ENABLED(CONFIG_PREEMPT_NONE);
+}
+static inline bool preempt_model_voluntary(void)
+{
+	return IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY);
+}
+static inline bool preempt_model_full(void)
+{
+	return IS_ENABLED(CONFIG_PREEMPT);
+}
+
+#endif
+
+static inline bool preempt_model_rt(void)
+{
+	return IS_ENABLED(CONFIG_PREEMPT_RT);
+}
+
+/*
+ * Does the preemption model allow non-cooperative preemption?
+ *
+ * For !CONFIG_PREEMPT_DYNAMIC kernels this is an exact match with
+ * CONFIG_PREEMPTION; for CONFIG_PREEMPT_DYNAMIC this doesn't work as the
+ * kernel is *built* with CONFIG_PREEMPTION=y but may run with e.g. the
+ * PREEMPT_NONE model.
+ */
+static inline bool preempt_model_preemptible(void)
+{
+	return preempt_model_full() || preempt_model_rt();
+}
+
 /*
  * Does a critical section need to be broken due to another
  * task waiting?: (technically does not depend on CONFIG_PREEMPTION,

include/linux/srcutree.h

@@ -47,11 +47,9 @@ struct srcu_data {
  */
 struct srcu_node {
 	spinlock_t __private lock;
-	unsigned long srcu_have_cbs[4];		/* GP seq for children */
-						/*  having CBs, but only */
-						/*  is > ->srcu_gq_seq. */
-	unsigned long srcu_data_have_cbs[4];	/* Which srcu_data structs */
-						/*  have CBs for given GP? */
+	unsigned long srcu_have_cbs[4];		/* GP seq for children having CBs, but only */
+						/*  if greater than ->srcu_gq_seq. */
+	unsigned long srcu_data_have_cbs[4];	/* Which srcu_data structs have CBs for given GP? */
 	unsigned long srcu_gp_seq_needed_exp;	/* Furthest future exp GP. */
 	struct srcu_node *srcu_parent;		/* Next up in tree. */
 	int grplo;				/* Least CPU for node. */
@@ -62,18 +60,24 @@ struct srcu_node {
  * Per-SRCU-domain structure, similar in function to rcu_state.
  */
 struct srcu_struct {
-	struct srcu_node node[NUM_RCU_NODES];	/* Combining tree. */
+	struct srcu_node *node;			/* Combining tree. */
 	struct srcu_node *level[RCU_NUM_LVLS + 1];
 						/* First node at each level. */
+	int srcu_size_state;			/* Small-to-big transition state. */
 	struct mutex srcu_cb_mutex;		/* Serialize CB preparation. */
-	spinlock_t __private lock;		/* Protect counters */
+	spinlock_t __private lock;		/* Protect counters and size state. */
 	struct mutex srcu_gp_mutex;		/* Serialize GP work. */
 	unsigned int srcu_idx;			/* Current rdr array element. */
 	unsigned long srcu_gp_seq;		/* Grace-period seq #. */
 	unsigned long srcu_gp_seq_needed;	/* Latest gp_seq needed. */
 	unsigned long srcu_gp_seq_needed_exp;	/* Furthest future exp GP. */
+	unsigned long srcu_gp_start;		/* Last GP start timestamp (jiffies) */
 	unsigned long srcu_last_gp_end;		/* Last GP end timestamp (ns) */
+	unsigned long srcu_size_jiffies;	/* Current contention-measurement interval. */
+	unsigned long srcu_n_lock_retries;	/* Contention events in current interval. */
+	unsigned long srcu_n_exp_nodelay;	/* # expedited no-delays in current GP phase. */
 	struct srcu_data __percpu *sda;		/* Per-CPU srcu_data array. */
+	bool sda_is_static;			/* May ->sda be passed to free_percpu()? */
 	unsigned long srcu_barrier_seq;		/* srcu_barrier seq #. */
 	struct mutex srcu_barrier_mutex;	/* Serialize barrier ops. */
 	struct completion srcu_barrier_completion;
@@ -81,10 +85,23 @@ struct srcu_struct {
 	atomic_t srcu_barrier_cpu_cnt;		/* # CPUs not yet posting a */
 						/*  callback for the barrier */
 						/*  operation. */
+	unsigned long reschedule_jiffies;
+	unsigned long reschedule_count;
 	struct delayed_work work;
 	struct lockdep_map dep_map;
 };
 
+/* Values for size state variable (->srcu_size_state). */
+#define SRCU_SIZE_SMALL		0
+#define SRCU_SIZE_ALLOC		1
+#define SRCU_SIZE_WAIT_BARRIER	2
+#define SRCU_SIZE_WAIT_CALL	3
+#define SRCU_SIZE_WAIT_CBS1	4
+#define SRCU_SIZE_WAIT_CBS2	5
+#define SRCU_SIZE_WAIT_CBS3	6
+#define SRCU_SIZE_WAIT_CBS4	7
+#define SRCU_SIZE_BIG		8
+
 /* Values for state variable (bottom bits of ->srcu_gp_seq). */
 #define SRCU_STATE_IDLE		0
 #define SRCU_STATE_SCAN1	1
@@ -121,6 +138,7 @@ struct srcu_struct {
 #ifdef MODULE
 # define __DEFINE_SRCU(name, is_static)					\
 	is_static struct srcu_struct name;				\
+	extern struct srcu_struct * const __srcu_struct_##name;		\
 	struct srcu_struct * const __srcu_struct_##name			\
 		__section("___srcu_struct_ptrs") = &name
 #else

include/linux/torture.h

@@ -118,7 +118,7 @@ void _torture_stop_kthread(char *m, struct task_struct **tp);
 	_torture_stop_kthread("Stopping " #n " task", &(tp))
 
 #ifdef CONFIG_PREEMPTION
-#define torture_preempt_schedule() preempt_schedule()
+#define torture_preempt_schedule() __preempt_schedule()
 #else
 #define torture_preempt_schedule()	do { } while (0)
 #endif

kernel/bpf/Kconfig

@@ -27,6 +27,7 @@ config BPF_SYSCALL
 	bool "Enable bpf() system call"
 	select BPF
 	select IRQ_WORK
+	select TASKS_RCU if PREEMPTION
 	select TASKS_TRACE_RCU
 	select BINARY_PRINTF
 	select NET_SOCK_MSG if NET

kernel/rcu/Kconfig

@@ -77,31 +77,56 @@ config TASKS_RCU_GENERIC
 	  This option enables generic infrastructure code supporting
 	  task-based RCU implementations.  Not for manual selection.
 
+config FORCE_TASKS_RCU
+	bool "Force selection of TASKS_RCU"
+	depends on RCU_EXPERT
+	select TASKS_RCU
+	default n
+	help
+	  This option force-enables a task-based RCU implementation
+	  that uses only voluntary context switch (not preemption!),
+	  idle, and user-mode execution as quiescent states.  Not for
+	  manual selection in most cases.
+
 config TASKS_RCU
-	def_bool PREEMPTION
+	bool
+	default n
+	select IRQ_WORK
+
+config FORCE_TASKS_RUDE_RCU
+	bool "Force selection of Tasks Rude RCU"
+	depends on RCU_EXPERT
+	select TASKS_RUDE_RCU
+	default n
 	help
-	  This option enables a task-based RCU implementation that uses
-	  only voluntary context switch (not preemption!), idle, and
-	  user-mode execution as quiescent states.  Not for manual selection.
+	  This option force-enables a task-based RCU implementation
+	  that uses only context switch (including preemption) and
+	  user-mode execution as quiescent states.  It forces IPIs and
+	  context switches on all online CPUs, including idle ones,
+	  so use with caution.	Not for manual selection in most cases.
 
 config TASKS_RUDE_RCU
-	def_bool 0
+	bool
+	default n
+	select IRQ_WORK
+
+config FORCE_TASKS_TRACE_RCU
+	bool "Force selection of Tasks Trace RCU"
+	depends on RCU_EXPERT
+	select TASKS_TRACE_RCU
+	default n
 	help
 	  This option enables a task-based RCU implementation that uses
-	  only context switch (including preemption) and user-mode
-	  execution as quiescent states.  It forces IPIs and context
-	  switches on all online CPUs, including idle ones, so use
-	  with caution.
+	  explicit rcu_read_lock_trace() read-side markers, and allows
+	  these readers to appear in the idle loop as well as on the
+	  CPU hotplug code paths.  It can force IPIs on online CPUs,
+	  including idle ones, so use with caution.  Not for manual
+	  selection in most cases.
 
 config TASKS_TRACE_RCU
-	def_bool 0
+	bool
+	default n
 	select IRQ_WORK
-	help
-	  This option enables a task-based RCU implementation that uses
-	  explicit rcu_read_lock_trace() read-side markers, and allows
-	  these readers to appear in the idle loop as well as on the CPU
-	  hotplug code paths.  It can force IPIs on online CPUs, including
-	  idle ones, so use with caution.
 
 config RCU_STALL_COMMON
 	def_bool TREE_RCU
@@ -225,7 +250,7 @@ config RCU_NOCB_CPU
 
 config TASKS_TRACE_RCU_READ_MB
 	bool "Tasks Trace RCU readers use memory barriers in user and idle"
-	depends on RCU_EXPERT
+	depends on RCU_EXPERT && TASKS_TRACE_RCU
 	default PREEMPT_RT || NR_CPUS < 8
 	help
 	  Use this option to further reduce the number of IPIs sent

kernel/rcu/Kconfig.debug

@@ -28,9 +28,6 @@ config RCU_SCALE_TEST
 	depends on DEBUG_KERNEL
 	select TORTURE_TEST
 	select SRCU
-	select TASKS_RCU
-	select TASKS_RUDE_RCU
-	select TASKS_TRACE_RCU
 	default n
 	help
 	  This option provides a kernel module that runs performance
@@ -47,9 +44,6 @@ config RCU_TORTURE_TEST
 	depends on DEBUG_KERNEL
 	select TORTURE_TEST
 	select SRCU
-	select TASKS_RCU
-	select TASKS_RUDE_RCU
-	select TASKS_TRACE_RCU
 	default n
 	help
 	  This option provides a kernel module that runs torture tests
@@ -66,9 +60,6 @@ config RCU_REF_SCALE_TEST
 	depends on DEBUG_KERNEL
 	select TORTURE_TEST
 	select SRCU
-	select TASKS_RCU
-	select TASKS_RUDE_RCU
-	select TASKS_TRACE_RCU
 	default n
 	help
 	  This option provides a kernel module that runs performance tests

kernel/rcu/rcu.h

@@ -523,6 +523,8 @@ static inline bool rcu_check_boost_fail(unsigned long gp_state, int *cpup) { ret
 static inline void show_rcu_gp_kthreads(void) { }
 static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
 static inline void rcu_fwd_progress_check(unsigned long j) { }
+static inline void rcu_gp_slow_register(atomic_t *rgssp) { }
+static inline void rcu_gp_slow_unregister(atomic_t *rgssp) { }
 #else /* #ifdef CONFIG_TINY_RCU */
 bool rcu_dynticks_zero_in_eqs(int cpu, int *vp);
 unsigned long rcu_get_gp_seq(void);
@@ -535,13 +537,13 @@ void rcu_fwd_progress_check(unsigned long j);
 void rcu_force_quiescent_state(void);
 extern struct workqueue_struct *rcu_gp_wq;
 extern struct workqueue_struct *rcu_par_gp_wq;
+void rcu_gp_slow_register(atomic_t *rgssp);
+void rcu_gp_slow_unregister(atomic_t *rgssp);
 #endif /* #else #ifdef CONFIG_TINY_RCU */
 
 #ifdef CONFIG_RCU_NOCB_CPU
-bool rcu_is_nocb_cpu(int cpu);
 void rcu_bind_current_to_nocb(void);
 #else
-static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
 static inline void rcu_bind_current_to_nocb(void) { }
 #endif
 

kernel/rcu/rcu_segcblist.c

@@ -505,10 +505,10 @@ void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq)
 		WRITE_ONCE(rsclp->tails[j], rsclp->tails[RCU_DONE_TAIL]);
 
 	/*
-	 * Callbacks moved, so clean up the misordered ->tails[] pointers
-	 * that now point into the middle of the list of ready-to-invoke
-	 * callbacks.  The overall effect is to copy down the later pointers
-	 * into the gap that was created by the now-ready segments.
+	 * Callbacks moved, so there might be an empty RCU_WAIT_TAIL
+	 * and a non-empty RCU_NEXT_READY_TAIL.  If so, copy the
+	 * RCU_NEXT_READY_TAIL segment to fill the RCU_WAIT_TAIL gap
+	 * created by the now-ready-to-invoke segments.
 	 */
 	for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
 		if (rsclp->tails[j] == rsclp->tails[RCU_NEXT_TAIL])

kernel/rcu/rcuscale.c

@@ -268,6 +268,8 @@ static struct rcu_scale_ops srcud_ops = {
 	.name		= "srcud"
 };
 
+#ifdef CONFIG_TASKS_RCU
+
 /*
  * Definitions for RCU-tasks scalability testing.
  */
@@ -295,6 +297,16 @@ static struct rcu_scale_ops tasks_ops = {
 	.name		= "tasks"
 };
 
+#define TASKS_OPS &tasks_ops,
+
+#else // #ifdef CONFIG_TASKS_RCU
+
+#define TASKS_OPS
+
+#endif // #else // #ifdef CONFIG_TASKS_RCU
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+
 /*
  * Definitions for RCU-tasks-trace scalability testing.
  */
@@ -324,6 +336,14 @@ static struct rcu_scale_ops tasks_tracing_ops = {
 	.name		= "tasks-tracing"
 };
 
+#define TASKS_TRACING_OPS &tasks_tracing_ops,
+
+#else // #ifdef CONFIG_TASKS_TRACE_RCU
+
+#define TASKS_TRACING_OPS
+
+#endif // #else // #ifdef CONFIG_TASKS_TRACE_RCU
+
 static unsigned long rcuscale_seq_diff(unsigned long new, unsigned long old)
 {
 	if (!cur_ops->gp_diff)
@@ -797,7 +817,7 @@ rcu_scale_init(void)
 	long i;
 	int firsterr = 0;
 	static struct rcu_scale_ops *scale_ops[] = {
-		&rcu_ops, &srcu_ops, &srcud_ops, &tasks_ops, &tasks_tracing_ops
+		&rcu_ops, &srcu_ops, &srcud_ops, TASKS_OPS TASKS_TRACING_OPS
 	};
 
 	if (!torture_init_begin(scale_type, verbose))

kernel/rcu/rcutorture.c

@@ -737,6 +737,50 @@ static struct rcu_torture_ops busted_srcud_ops = {
 	.name		= "busted_srcud"
 };
 
+/*
+ * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
+ * This implementation does not necessarily work well with CPU hotplug.
+ */
+
+static void synchronize_rcu_trivial(void)
+{
+	int cpu;
+
+	for_each_online_cpu(cpu) {
+		rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
+		WARN_ON_ONCE(raw_smp_processor_id() != cpu);
+	}
+}
+
+static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
+{
+	preempt_disable();
+	return 0;
+}
+
+static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
+{
+	preempt_enable();
+}
+
+static struct rcu_torture_ops trivial_ops = {
+	.ttype		= RCU_TRIVIAL_FLAVOR,
+	.init		= rcu_sync_torture_init,
+	.readlock	= rcu_torture_read_lock_trivial,
+	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
+	.readunlock	= rcu_torture_read_unlock_trivial,
+	.readlock_held	= torture_readlock_not_held,
+	.get_gp_seq	= rcu_no_completed,
+	.sync		= synchronize_rcu_trivial,
+	.exp_sync	= synchronize_rcu_trivial,
+	.fqs		= NULL,
+	.stats		= NULL,
+	.irq_capable	= 1,
+	.name		= "trivial"
+};
+
+#ifdef CONFIG_TASKS_RCU
+
 /*
  * Definitions for RCU-tasks torture testing.
  */
@@ -780,47 +824,16 @@ static struct rcu_torture_ops tasks_ops = {
 	.name		= "tasks"
 };
 
-/*
- * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
- * This implementation does not necessarily work well with CPU hotplug.
- */
+#define TASKS_OPS &tasks_ops,
 
-static void synchronize_rcu_trivial(void)
-{
-	int cpu;
+#else // #ifdef CONFIG_TASKS_RCU
 
-	for_each_online_cpu(cpu) {
-		rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
-		WARN_ON_ONCE(raw_smp_processor_id() != cpu);
-	}
-}
+#define TASKS_OPS
 
-static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
-{
-	preempt_disable();
-	return 0;
-}
+#endif // #else #ifdef CONFIG_TASKS_RCU
 
-static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
-{
-	preempt_enable();
-}
 
-static struct rcu_torture_ops trivial_ops = {
-	.ttype		= RCU_TRIVIAL_FLAVOR,
-	.init		= rcu_sync_torture_init,
-	.readlock	= rcu_torture_read_lock_trivial,
-	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
-	.readunlock	= rcu_torture_read_unlock_trivial,
-	.readlock_held	= torture_readlock_not_held,
-	.get_gp_seq	= rcu_no_completed,
-	.sync		= synchronize_rcu_trivial,
-	.exp_sync	= synchronize_rcu_trivial,
-	.fqs		= NULL,
-	.stats		= NULL,
-	.irq_capable	= 1,
-	.name		= "trivial"
-};
+#ifdef CONFIG_TASKS_RUDE_RCU
 
 /*
  * Definitions for rude RCU-tasks torture testing.
@@ -851,6 +864,17 @@ static struct rcu_torture_ops tasks_rude_ops = {
 	.name		= "tasks-rude"
 };
 
+#define TASKS_RUDE_OPS &tasks_rude_ops,
+
+#else // #ifdef CONFIG_TASKS_RUDE_RCU
+
+#define TASKS_RUDE_OPS
+
+#endif // #else #ifdef CONFIG_TASKS_RUDE_RCU
+
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+
 /*
  * Definitions for tracing RCU-tasks torture testing.
  */
@@ -893,6 +917,15 @@ static struct rcu_torture_ops tasks_tracing_ops = {
 	.name		= "tasks-tracing"
 };
 
+#define TASKS_TRACING_OPS &tasks_tracing_ops,
+
+#else // #ifdef CONFIG_TASKS_TRACE_RCU
+
+#define TASKS_TRACING_OPS
+
+#endif // #else #ifdef CONFIG_TASKS_TRACE_RCU
+
+
 static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
 {
 	if (!cur_ops->gp_diff)
@@ -1178,7 +1211,7 @@ rcu_torture_writer(void *arg)
 			 " GP expediting controlled from boot/sysfs for %s.\n",
 			 torture_type, cur_ops->name);
 	if (WARN_ONCE(nsynctypes == 0,
-		      "rcu_torture_writer: No update-side primitives.\n")) {
+		      "%s: No update-side primitives.\n", __func__)) {
 		/*
 		 * No updates primitives, so don't try updating.
 		 * The resulting test won't be testing much, hence the
@@ -1186,6 +1219,7 @@ rcu_torture_writer(void *arg)
 		 */
 		rcu_torture_writer_state = RTWS_STOPPING;
 		torture_kthread_stopping("rcu_torture_writer");
+		return 0;
 	}
 
 	do {
@@ -1322,6 +1356,17 @@ rcu_torture_fakewriter(void *arg)
 	VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
 	set_user_nice(current, MAX_NICE);
 
+	if (WARN_ONCE(nsynctypes == 0,
+		      "%s: No update-side primitives.\n", __func__)) {
+		/*
+		 * No updates primitives, so don't try updating.
+		 * The resulting test won't be testing much, hence the
+		 * above WARN_ONCE().
+		 */
+		torture_kthread_stopping("rcu_torture_fakewriter");
+		return 0;
+	}
+
 	do {
 		torture_hrtimeout_jiffies(torture_random(&rand) % 10, &rand);
 		if (cur_ops->cb_barrier != NULL &&
@@ -2916,10 +2961,12 @@ rcu_torture_cleanup(void)
 			pr_info("%s: Invoking %pS().\n", __func__, cur_ops->cb_barrier);
 			cur_ops->cb_barrier();
 		}
+		rcu_gp_slow_unregister(NULL);
 		return;
 	}
 	if (!cur_ops) {
 		torture_cleanup_end();
+		rcu_gp_slow_unregister(NULL);
 		return;
 	}
 
@@ -3016,6 +3063,7 @@ rcu_torture_cleanup(void)
 	else
 		rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
 	torture_cleanup_end();
+	rcu_gp_slow_unregister(&rcu_fwd_cb_nodelay);
 }
 
 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
@@ -3096,9 +3144,9 @@ rcu_torture_init(void)
 	int flags = 0;
 	unsigned long gp_seq = 0;
 	static struct rcu_torture_ops *torture_ops[] = {
-		&rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
-		&busted_srcud_ops, &tasks_ops, &tasks_rude_ops,
-		&tasks_tracing_ops, &trivial_ops,
+		&rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops, &busted_srcud_ops,
+		TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
+		&trivial_ops,
 	};
 
 	if (!torture_init_begin(torture_type, verbose))
@@ -3320,6 +3368,7 @@ rcu_torture_init(void)
 	if (object_debug)
 		rcu_test_debug_objects();
 	torture_init_end();
+	rcu_gp_slow_register(&rcu_fwd_cb_nodelay);
 	return 0;
 
 unwind:

kernel/rcu/refscale.c

@@ -207,6 +207,8 @@ static struct ref_scale_ops srcu_ops = {
 	.name		= "srcu"
 };
 
+#ifdef CONFIG_TASKS_RCU
+
 // Definitions for RCU Tasks ref scale testing: Empty read markers.
 // These definitions also work for RCU Rude readers.
 static void rcu_tasks_ref_scale_read_section(const int nloops)
@@ -232,6 +234,16 @@ static struct ref_scale_ops rcu_tasks_ops = {
 	.name		= "rcu-tasks"
 };
 
+#define RCU_TASKS_OPS &rcu_tasks_ops,
+
+#else // #ifdef CONFIG_TASKS_RCU
+
+#define RCU_TASKS_OPS
+
+#endif // #else // #ifdef CONFIG_TASKS_RCU
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+
 // Definitions for RCU Tasks Trace ref scale testing.
 static void rcu_trace_ref_scale_read_section(const int nloops)
 {
@@ -261,6 +273,14 @@ static struct ref_scale_ops rcu_trace_ops = {
 	.name		= "rcu-trace"
 };
 
+#define RCU_TRACE_OPS &rcu_trace_ops,
+
+#else // #ifdef CONFIG_TASKS_TRACE_RCU
+
+#define RCU_TRACE_OPS
+
+#endif // #else // #ifdef CONFIG_TASKS_TRACE_RCU
+
 // Definitions for reference count
 static atomic_t refcnt;
 
@@ -790,7 +810,7 @@ ref_scale_init(void)
 	long i;
 	int firsterr = 0;
 	static struct ref_scale_ops *scale_ops[] = {
-		&rcu_ops, &srcu_ops, &rcu_trace_ops, &rcu_tasks_ops, &refcnt_ops, &rwlock_ops,
+		&rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_ops,
 		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops,
 	};
 

kernel/rcu/sync.c

@@ -111,7 +111,7 @@ static void rcu_sync_func(struct rcu_head *rhp)
  * a slowpath during the update.  After this function returns, all
  * subsequent calls to rcu_sync_is_idle() will return false, which
  * tells readers to stay off their fastpaths.  A later call to
- * rcu_sync_exit() re-enables reader slowpaths.
+ * rcu_sync_exit() re-enables reader fastpaths.
  *
  * When called in isolation, rcu_sync_enter() must wait for a grace
  * period, however, closely spaced calls to rcu_sync_enter() can

kernel/rcu/tasks.h

@@ -46,7 +46,7 @@ struct rcu_tasks_percpu {
 
 /**
  * struct rcu_tasks - Definition for a Tasks-RCU-like mechanism.
- * @cbs_wq: Wait queue allowing new callback to get kthread's attention.
+ * @cbs_wait: RCU wait allowing a new callback to get kthread's attention.
  * @cbs_gbl_lock: Lock protecting callback list.
  * @kthread_ptr: This flavor's grace-period/callback-invocation kthread.
  * @gp_func: This flavor's grace-period-wait function.
@@ -77,7 +77,7 @@ struct rcu_tasks_percpu {
  * @kname: This flavor's kthread name.
  */
 struct rcu_tasks {
-	struct wait_queue_head cbs_wq;
+	struct rcuwait cbs_wait;
 	raw_spinlock_t cbs_gbl_lock;
 	int gp_state;
 	int gp_sleep;
@@ -113,11 +113,11 @@ static void call_rcu_tasks_iw_wakeup(struct irq_work *iwp);
 #define DEFINE_RCU_TASKS(rt_name, gp, call, n)						\
 static DEFINE_PER_CPU(struct rcu_tasks_percpu, rt_name ## __percpu) = {			\
 	.lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name ## __percpu.cbs_pcpu_lock),		\
-	.rtp_irq_work = IRQ_WORK_INIT(call_rcu_tasks_iw_wakeup),			\
+	.rtp_irq_work = IRQ_WORK_INIT_HARD(call_rcu_tasks_iw_wakeup),			\
 };											\
 static struct rcu_tasks rt_name =							\
 {											\
-	.cbs_wq = __WAIT_QUEUE_HEAD_INITIALIZER(rt_name.cbs_wq),			\
+	.cbs_wait = __RCUWAIT_INITIALIZER(rt_name.wait),				\
 	.cbs_gbl_lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name.cbs_gbl_lock),			\
 	.gp_func = gp,									\
 	.call_func = call,								\
@@ -143,6 +143,11 @@ module_param(rcu_task_ipi_delay, int, 0644);
 #define RCU_TASK_STALL_TIMEOUT (HZ * 60 * 10)
 static int rcu_task_stall_timeout __read_mostly = RCU_TASK_STALL_TIMEOUT;
 module_param(rcu_task_stall_timeout, int, 0644);
+#define RCU_TASK_STALL_INFO (HZ * 10)
+static int rcu_task_stall_info __read_mostly = RCU_TASK_STALL_INFO;
+module_param(rcu_task_stall_info, int, 0644);
+static int rcu_task_stall_info_mult __read_mostly = 3;
+module_param(rcu_task_stall_info_mult, int, 0444);
 
 static int rcu_task_enqueue_lim __read_mostly = -1;
 module_param(rcu_task_enqueue_lim, int, 0444);
@@ -261,14 +266,16 @@ static void call_rcu_tasks_iw_wakeup(struct irq_work *iwp)
 	struct rcu_tasks_percpu *rtpcp = container_of(iwp, struct rcu_tasks_percpu, rtp_irq_work);
 
 	rtp = rtpcp->rtpp;
-	wake_up(&rtp->cbs_wq);
+	rcuwait_wake_up(&rtp->cbs_wait);
 }
 
 // Enqueue a callback for the specified flavor of Tasks RCU.
 static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func,
 				   struct rcu_tasks *rtp)
 {
+	int chosen_cpu;
 	unsigned long flags;
+	int ideal_cpu;
 	unsigned long j;
 	bool needadjust = false;
 	bool needwake;
@@ -278,8 +285,9 @@ static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func,
 	rhp->func = func;
 	local_irq_save(flags);
 	rcu_read_lock();
-	rtpcp = per_cpu_ptr(rtp->rtpcpu,
-			    smp_processor_id() >> READ_ONCE(rtp->percpu_enqueue_shift));
+	ideal_cpu = smp_processor_id() >> READ_ONCE(rtp->percpu_enqueue_shift);
+	chosen_cpu = cpumask_next(ideal_cpu - 1, cpu_possible_mask);
+	rtpcp = per_cpu_ptr(rtp->rtpcpu, chosen_cpu);
 	if (!raw_spin_trylock_rcu_node(rtpcp)) { // irqs already disabled.
 		raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.
 		j = jiffies;
@@ -460,7 +468,7 @@ static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp, struct rcu_tasks_percpu
 		}
 	}
 
-	if (rcu_segcblist_empty(&rtpcp->cblist))
+	if (rcu_segcblist_empty(&rtpcp->cblist) || !cpu_possible(cpu))
 		return;
 	raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
 	rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq));
@@ -509,7 +517,9 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 		set_tasks_gp_state(rtp, RTGS_WAIT_CBS);
 
 		/* If there were none, wait a bit and start over. */
-		wait_event_idle(rtp->cbs_wq, (needgpcb = rcu_tasks_need_gpcb(rtp)));
+		rcuwait_wait_event(&rtp->cbs_wait,
+				   (needgpcb = rcu_tasks_need_gpcb(rtp)),
+				   TASK_IDLE);
 
 		if (needgpcb & 0x2) {
 			// Wait for one grace period.
@@ -548,8 +558,15 @@ static void __init rcu_spawn_tasks_kthread_generic(struct rcu_tasks *rtp)
 static void __init rcu_tasks_bootup_oddness(void)
 {
 #if defined(CONFIG_TASKS_RCU) || defined(CONFIG_TASKS_TRACE_RCU)
+	int rtsimc;
+
 	if (rcu_task_stall_timeout != RCU_TASK_STALL_TIMEOUT)
 		pr_info("\tTasks-RCU CPU stall warnings timeout set to %d (rcu_task_stall_timeout).\n", rcu_task_stall_timeout);
+	rtsimc = clamp(rcu_task_stall_info_mult, 1, 10);
+	if (rtsimc != rcu_task_stall_info_mult) {
+		pr_info("\tTasks-RCU CPU stall info multiplier clamped to %d (rcu_task_stall_info_mult).\n", rtsimc);
+		rcu_task_stall_info_mult = rtsimc;
+	}
 #endif /* #ifdef CONFIG_TASKS_RCU */
 #ifdef CONFIG_TASKS_RCU
 	pr_info("\tTrampoline variant of Tasks RCU enabled.\n");
@@ -568,7 +585,17 @@ static void __init rcu_tasks_bootup_oddness(void)
 /* Dump out rcutorture-relevant state common to all RCU-tasks flavors. */
 static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
 {
-	struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, 0); // for_each...
+	int cpu;
+	bool havecbs = false;
+
+	for_each_possible_cpu(cpu) {
+		struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);
+
+		if (!data_race(rcu_segcblist_empty(&rtpcp->cblist))) {
+			havecbs = true;
+			break;
+		}
+	}
 	pr_info("%s: %s(%d) since %lu g:%lu i:%lu/%lu %c%c %s\n",
 		rtp->kname,
 		tasks_gp_state_getname(rtp), data_race(rtp->gp_state),
@@ -576,7 +603,7 @@ static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
 		data_race(rcu_seq_current(&rtp->tasks_gp_seq)),
 		data_race(rtp->n_ipis_fails), data_race(rtp->n_ipis),
 		".k"[!!data_race(rtp->kthread_ptr)],
-		".C"[!data_race(rcu_segcblist_empty(&rtpcp->cblist))],
+		".C"[havecbs],
 		s);
 }
 #endif // #ifndef CONFIG_TINY_RCU
@@ -592,10 +619,15 @@ static void exit_tasks_rcu_finish_trace(struct task_struct *t);
 /* Wait for one RCU-tasks grace period. */
 static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
 {
-	struct task_struct *g, *t;
-	unsigned long lastreport;
-	LIST_HEAD(holdouts);
+	struct task_struct *g;
 	int fract;
+	LIST_HEAD(holdouts);
+	unsigned long j;
+	unsigned long lastinfo;
+	unsigned long lastreport;
+	bool reported = false;
+	int rtsi;
+	struct task_struct *t;
 
 	set_tasks_gp_state(rtp, RTGS_PRE_WAIT_GP);
 	rtp->pregp_func();
@@ -621,30 +653,50 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
 	 * is empty, we are done.
 	 */
 	lastreport = jiffies;
+	lastinfo = lastreport;
+	rtsi = READ_ONCE(rcu_task_stall_info);
 
 	// Start off with initial wait and slowly back off to 1 HZ wait.
 	fract = rtp->init_fract;
 
 	while (!list_empty(&holdouts)) {
+		ktime_t exp;
 		bool firstreport;
 		bool needreport;
 		int rtst;
 
-		/* Slowly back off waiting for holdouts */
+		// Slowly back off waiting for holdouts
 		set_tasks_gp_state(rtp, RTGS_WAIT_SCAN_HOLDOUTS);
-		schedule_timeout_idle(fract);
+		if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+			schedule_timeout_idle(fract);
+		} else {
+			exp = jiffies_to_nsecs(fract);
+			__set_current_state(TASK_IDLE);
+			schedule_hrtimeout_range(&exp, jiffies_to_nsecs(HZ / 2), HRTIMER_MODE_REL_HARD);
+		}
 
 		if (fract < HZ)
 			fract++;
 
 		rtst = READ_ONCE(rcu_task_stall_timeout);
 		needreport = rtst > 0 && time_after(jiffies, lastreport + rtst);
-		if (needreport)
+		if (needreport) {
 			lastreport = jiffies;
+			reported = true;
+		}
 		firstreport = true;
 		WARN_ON(signal_pending(current));
 		set_tasks_gp_state(rtp, RTGS_SCAN_HOLDOUTS);
 		rtp->holdouts_func(&holdouts, needreport, &firstreport);
+
+		// Print pre-stall informational messages if needed.
+		j = jiffies;
+		if (rtsi > 0 && !reported && time_after(j, lastinfo + rtsi)) {
+			lastinfo = j;
+			rtsi = rtsi * rcu_task_stall_info_mult;
+			pr_info("%s: %s grace period %lu is %lu jiffies old.\n",
+				__func__, rtp->kname, rtp->tasks_gp_seq, j - rtp->gp_start);
+		}
 	}
 
 	set_tasks_gp_state(rtp, RTGS_POST_GP);
@@ -950,6 +1002,9 @@ static void rcu_tasks_be_rude(struct work_struct *work)
 // Wait for one rude RCU-tasks grace period.
 static void rcu_tasks_rude_wait_gp(struct rcu_tasks *rtp)
 {
+	if (num_online_cpus() <= 1)
+		return;	// Fastpath for only one CPU.
+
 	rtp->n_ipis += cpumask_weight(cpu_online_mask);
 	schedule_on_each_cpu(rcu_tasks_be_rude);
 }

kernel/rcu/tree.c

@@ -1679,6 +1679,8 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
 	rdp->gp_seq = rnp->gp_seq;  /* Remember new grace-period state. */
 	if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap)
 		WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed);
+	if (IS_ENABLED(CONFIG_PROVE_RCU) && READ_ONCE(rdp->gpwrap))
+		WRITE_ONCE(rdp->last_sched_clock, jiffies);
 	WRITE_ONCE(rdp->gpwrap, false);
 	rcu_gpnum_ovf(rnp, rdp);
 	return ret;
@@ -1705,11 +1707,37 @@ static void note_gp_changes(struct rcu_data *rdp)
 		rcu_gp_kthread_wake();
 }
 
+static atomic_t *rcu_gp_slow_suppress;
+
+/* Register a counter to suppress debugging grace-period delays. */
+void rcu_gp_slow_register(atomic_t *rgssp)
+{
+	WARN_ON_ONCE(rcu_gp_slow_suppress);
+
+	WRITE_ONCE(rcu_gp_slow_suppress, rgssp);
+}
+EXPORT_SYMBOL_GPL(rcu_gp_slow_register);
+
+/* Unregister a counter, with NULL for not caring which. */
+void rcu_gp_slow_unregister(atomic_t *rgssp)
+{
+	WARN_ON_ONCE(rgssp && rgssp != rcu_gp_slow_suppress);
+
+	WRITE_ONCE(rcu_gp_slow_suppress, NULL);
+}
+EXPORT_SYMBOL_GPL(rcu_gp_slow_unregister);
+
+static bool rcu_gp_slow_is_suppressed(void)
+{
+	atomic_t *rgssp = READ_ONCE(rcu_gp_slow_suppress);
+
+	return rgssp && atomic_read(rgssp);
+}
+
 static void rcu_gp_slow(int delay)
 {
-	if (delay > 0 &&
-	    !(rcu_seq_ctr(rcu_state.gp_seq) %
-	      (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))
+	if (!rcu_gp_slow_is_suppressed() && delay > 0 &&
+	    !(rcu_seq_ctr(rcu_state.gp_seq) % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))
 		schedule_timeout_idle(delay);
 }
 
@@ -2096,14 +2124,29 @@ static noinline void rcu_gp_cleanup(void)
 	/* Advance CBs to reduce false positives below. */
 	offloaded = rcu_rdp_is_offloaded(rdp);
 	if ((offloaded || !rcu_accelerate_cbs(rnp, rdp)) && needgp) {
+
+		// We get here if a grace period was needed (“needgp”)
+		// and the above call to rcu_accelerate_cbs() did not set
+		// the RCU_GP_FLAG_INIT bit in ->gp_state (which records
+		// the need for another grace period).  The purpose
+		// of the “offloaded” check is to avoid invoking
+		// rcu_accelerate_cbs() on an offloaded CPU because we do not
+		// hold the ->nocb_lock needed to safely access an offloaded
+		// ->cblist.  We do not want to acquire that lock because
+		// it can be heavily contended during callback floods.
+
 		WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT);
 		WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
-		trace_rcu_grace_period(rcu_state.name,
-				       rcu_state.gp_seq,
-				       TPS("newreq"));
+		trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("newreq"));
 	} else {
-		WRITE_ONCE(rcu_state.gp_flags,
-			   rcu_state.gp_flags & RCU_GP_FLAG_INIT);
+
+		// We get here either if there is no need for an
+		// additional grace period or if rcu_accelerate_cbs() has
+		// already set the RCU_GP_FLAG_INIT bit in ->gp_flags. 
+		// So all we need to do is to clear all of the other
+		// ->gp_flags bits.
+
+		WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags & RCU_GP_FLAG_INIT);
 	}
 	raw_spin_unlock_irq_rcu_node(rnp);
 
@@ -2609,6 +2652,13 @@ static void rcu_do_batch(struct rcu_data *rdp)
  */
 void rcu_sched_clock_irq(int user)
 {
+	unsigned long j;
+
+	if (IS_ENABLED(CONFIG_PROVE_RCU)) {
+		j = jiffies;
+		WARN_ON_ONCE(time_before(j, __this_cpu_read(rcu_data.last_sched_clock)));
+		__this_cpu_write(rcu_data.last_sched_clock, j);
+	}
 	trace_rcu_utilization(TPS("Start scheduler-tick"));
 	lockdep_assert_irqs_disabled();
 	raw_cpu_inc(rcu_data.ticks_this_gp);
@@ -2624,6 +2674,8 @@ void rcu_sched_clock_irq(int user)
 	rcu_flavor_sched_clock_irq(user);
 	if (rcu_pending(user))
 		invoke_rcu_core();
+	if (user)
+		rcu_tasks_classic_qs(current, false);
 	lockdep_assert_irqs_disabled();
 
 	trace_rcu_utilization(TPS("End scheduler-tick"));
@@ -3717,7 +3769,9 @@ static int rcu_blocking_is_gp(void)
 {
 	int ret;
 
-	if (IS_ENABLED(CONFIG_PREEMPTION))
+	// Invoking preempt_model_*() too early gets a splat.
+	if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE ||
+	    preempt_model_full() || preempt_model_rt())
 		return rcu_scheduler_active == RCU_SCHEDULER_INACTIVE;
 	might_sleep();  /* Check for RCU read-side critical section. */
 	preempt_disable();
@@ -4179,6 +4233,7 @@ rcu_boot_init_percpu_data(int cpu)
 	rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED;
 	rdp->rcu_onl_gp_seq = rcu_state.gp_seq;
 	rdp->rcu_onl_gp_flags = RCU_GP_CLEANED;
+	rdp->last_sched_clock = jiffies;
 	rdp->cpu = cpu;
 	rcu_boot_init_nocb_percpu_data(rdp);
 }
@@ -4480,6 +4535,7 @@ static int __init rcu_spawn_gp_kthread(void)
 	struct rcu_node *rnp;
 	struct sched_param sp;
 	struct task_struct *t;
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 
 	rcu_scheduler_fully_active = 1;
 	t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name);
@@ -4497,8 +4553,14 @@ static int __init rcu_spawn_gp_kthread(void)
 	smp_store_release(&rcu_state.gp_kthread, t);  /* ^^^ */
 	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	wake_up_process(t);
-	rcu_spawn_nocb_kthreads();
-	rcu_spawn_boost_kthreads();
+	/* This is a pre-SMP initcall, we expect a single CPU */
+	WARN_ON(num_online_cpus() > 1);
+	/*
+	 * Those kthreads couldn't be created on rcu_init() -> rcutree_prepare_cpu()
+	 * due to rcu_scheduler_fully_active.
+	 */
+	rcu_spawn_cpu_nocb_kthread(smp_processor_id());
+	rcu_spawn_one_boost_kthread(rdp->mynode);
 	rcu_spawn_core_kthreads();
 	return 0;
 }
@@ -4782,7 +4844,7 @@ static void __init kfree_rcu_batch_init(void)
 
 void __init rcu_init(void)
 {
-	int cpu;
+	int cpu = smp_processor_id();
 
 	rcu_early_boot_tests();
 
@@ -4802,11 +4864,10 @@ void __init rcu_init(void)
 	 * or the scheduler are operational.
 	 */
 	pm_notifier(rcu_pm_notify, 0);
-	for_each_online_cpu(cpu) {
-		rcutree_prepare_cpu(cpu);
-		rcu_cpu_starting(cpu);
-		rcutree_online_cpu(cpu);
-	}
+	WARN_ON(num_online_cpus() > 1); // Only one CPU this early in boot.
+	rcutree_prepare_cpu(cpu);
+	rcu_cpu_starting(cpu);
+	rcutree_online_cpu(cpu);
 
 	/* Create workqueue for Tree SRCU and for expedited GPs. */
 	rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0);

kernel/rcu/tree.h

@@ -254,6 +254,7 @@ struct rcu_data {
 	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(). */
+	unsigned long last_sched_clock;	/* Jiffies of last rcu_sched_clock_irq(). */
 
 	int cpu;
 };
@@ -364,6 +365,7 @@ struct rcu_state {
 	arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
 						/* Synchronize offline with */
 						/*  GP pre-initialization. */
+	int nocb_is_setup;			/* nocb is setup from boot */
 };
 
 /* Values for rcu_state structure's gp_flags field. */
@@ -421,7 +423,6 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
 static bool rcu_is_callbacks_kthread(void);
 static void rcu_cpu_kthread_setup(unsigned int cpu);
 static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
-static void __init rcu_spawn_boost_kthreads(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);
@@ -439,7 +440,6 @@ static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level);
 static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
 static void rcu_spawn_cpu_nocb_kthread(int cpu);
-static void __init rcu_spawn_nocb_kthreads(void);
 static void show_rcu_nocb_state(struct rcu_data *rdp);
 static void rcu_nocb_lock(struct rcu_data *rdp);
 static void rcu_nocb_unlock(struct rcu_data *rdp);

kernel/rcu/tree_nocb.h

@@ -60,9 +60,6 @@ static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
  * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters.
  * If the list is invalid, a warning is emitted and all CPUs are offloaded.
  */
-
-static bool rcu_nocb_is_setup;
-
 static int __init rcu_nocb_setup(char *str)
 {
 	alloc_bootmem_cpumask_var(&rcu_nocb_mask);
@@ -72,7 +69,7 @@ static int __init rcu_nocb_setup(char *str)
 			cpumask_setall(rcu_nocb_mask);
 		}
 	}
-	rcu_nocb_is_setup = true;
+	rcu_state.nocb_is_setup = true;
 	return 1;
 }
 __setup("rcu_nocbs", rcu_nocb_setup);
@@ -215,14 +212,6 @@ static void rcu_init_one_nocb(struct rcu_node *rnp)
 	init_swait_queue_head(&rnp->nocb_gp_wq[1]);
 }
 
-/* Is the specified CPU a no-CBs CPU? */
-bool rcu_is_nocb_cpu(int cpu)
-{
-	if (cpumask_available(rcu_nocb_mask))
-		return cpumask_test_cpu(cpu, rcu_nocb_mask);
-	return false;
-}
-
 static bool __wake_nocb_gp(struct rcu_data *rdp_gp,
 			   struct rcu_data *rdp,
 			   bool force, unsigned long flags)
@@ -1180,10 +1169,10 @@ void __init rcu_init_nohz(void)
 				return;
 			}
 		}
-		rcu_nocb_is_setup = true;
+		rcu_state.nocb_is_setup = true;
 	}
 
-	if (!rcu_nocb_is_setup)
+	if (!rcu_state.nocb_is_setup)
 		return;
 
 #if defined(CONFIG_NO_HZ_FULL)
@@ -1241,7 +1230,7 @@ static void rcu_spawn_cpu_nocb_kthread(int cpu)
 	struct task_struct *t;
 	struct sched_param sp;
 
-	if (!rcu_scheduler_fully_active || !rcu_nocb_is_setup)
+	if (!rcu_scheduler_fully_active || !rcu_state.nocb_is_setup)
 		return;
 
 	/* If there already is an rcuo kthread, then nothing to do. */
@@ -1277,22 +1266,6 @@ static void rcu_spawn_cpu_nocb_kthread(int cpu)
 	WRITE_ONCE(rdp->nocb_gp_kthread, rdp_gp->nocb_gp_kthread);
 }
 
-/*
- * Once the scheduler is running, spawn rcuo kthreads for all online
- * no-CBs CPUs.  This assumes that the early_initcall()s happen before
- * non-boot CPUs come online -- if this changes, we will need to add
- * some mutual exclusion.
- */
-static void __init rcu_spawn_nocb_kthreads(void)
-{
-	int cpu;
-
-	if (rcu_nocb_is_setup) {
-		for_each_online_cpu(cpu)
-			rcu_spawn_cpu_nocb_kthread(cpu);
-	}
-}
-
 /* How many CB CPU IDs per GP kthread?  Default of -1 for sqrt(nr_cpu_ids). */
 static int rcu_nocb_gp_stride = -1;
 module_param(rcu_nocb_gp_stride, int, 0444);
@@ -1549,10 +1522,6 @@ static void rcu_spawn_cpu_nocb_kthread(int cpu)
 {
 }
 
-static void __init rcu_spawn_nocb_kthreads(void)
-{
-}
-
 static void show_rcu_nocb_state(struct rcu_data *rdp)
 {
 }

kernel/rcu/tree_plugin.h

@@ -486,6 +486,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 	t->rcu_read_unlock_special.s = 0;
 	if (special.b.need_qs) {
 		if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) {
+			rdp->cpu_no_qs.b.norm = false;
 			rcu_report_qs_rdp(rdp);
 			udelay(rcu_unlock_delay);
 		} else {
@@ -660,7 +661,13 @@ static void rcu_read_unlock_special(struct task_struct *t)
 			    expboost && !rdp->defer_qs_iw_pending && cpu_online(rdp->cpu)) {
 				// Get scheduler to re-evaluate and call hooks.
 				// If !IRQ_WORK, FQS scan will eventually IPI.
-				init_irq_work(&rdp->defer_qs_iw, rcu_preempt_deferred_qs_handler);
+				if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) &&
+				    IS_ENABLED(CONFIG_PREEMPT_RT))
+					rdp->defer_qs_iw = IRQ_WORK_INIT_HARD(
+								rcu_preempt_deferred_qs_handler);
+				else
+					init_irq_work(&rdp->defer_qs_iw,
+						      rcu_preempt_deferred_qs_handler);
 				rdp->defer_qs_iw_pending = true;
 				irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu);
 			}
@@ -1124,7 +1131,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
 	__releases(rnp->lock)
 {
 	raw_lockdep_assert_held_rcu_node(rnp);
-	if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) {
+	if (!rnp->boost_kthread_task ||
+	    (!rcu_preempt_blocked_readers_cgp(rnp) && !rnp->exp_tasks)) {
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 		return;
 	}
@@ -1226,18 +1234,6 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
 	free_cpumask_var(cm);
 }
 
-/*
- * Spawn boost kthreads -- called as soon as the scheduler is running.
- */
-static void __init rcu_spawn_boost_kthreads(void)
-{
-	struct rcu_node *rnp;
-
-	rcu_for_each_leaf_node(rnp)
-		if (rcu_rnp_online_cpus(rnp))
-			rcu_spawn_one_boost_kthread(rnp);
-}
-
 #else /* #ifdef CONFIG_RCU_BOOST */
 
 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
@@ -1263,10 +1259,6 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
 {
 }
 
-static void __init rcu_spawn_boost_kthreads(void)
-{
-}
-
 #endif /* #else #ifdef CONFIG_RCU_BOOST */
 
 /*

kernel/rcu/tree_stall.h

@@ -565,9 +565,9 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
 
 	for_each_possible_cpu(cpu)
 		totqlen += rcu_get_n_cbs_cpu(cpu);
-	pr_cont("\t(detected by %d, t=%ld jiffies, g=%ld, q=%lu)\n",
+	pr_cont("\t(detected by %d, t=%ld jiffies, g=%ld, q=%lu ncpus=%d)\n",
 	       smp_processor_id(), (long)(jiffies - gps),
-	       (long)rcu_seq_current(&rcu_state.gp_seq), totqlen);
+	       (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, rcu_state.n_online_cpus);
 	if (ndetected) {
 		rcu_dump_cpu_stacks();
 
@@ -626,9 +626,9 @@ static void print_cpu_stall(unsigned long gps)
 	raw_spin_unlock_irqrestore_rcu_node(rdp->mynode, flags);
 	for_each_possible_cpu(cpu)
 		totqlen += rcu_get_n_cbs_cpu(cpu);
-	pr_cont("\t(t=%lu jiffies g=%ld q=%lu)\n",
+	pr_cont("\t(t=%lu jiffies g=%ld q=%lu ncpus=%d)\n",
 		jiffies - gps,
-		(long)rcu_seq_current(&rcu_state.gp_seq), totqlen);
+		(long)rcu_seq_current(&rcu_state.gp_seq), totqlen, rcu_state.n_online_cpus);
 
 	rcu_check_gp_kthread_expired_fqs_timer();
 	rcu_check_gp_kthread_starvation();

kernel/scftorture.c

@@ -267,9 +267,10 @@ static void scf_handler(void *scfc_in)
 	}
 	this_cpu_inc(scf_invoked_count);
 	if (longwait <= 0) {
-		if (!(r & 0xffc0))
+		if (!(r & 0xffc0)) {
 			udelay(r & 0x3f);
-		goto out;
+			goto out;
+		}
 	}
 	if (r & 0xfff)
 		goto out;

kernel/sched/core.c

@@ -8409,6 +8409,18 @@ static void __init preempt_dynamic_init(void)
 	}
 }
 
+#define PREEMPT_MODEL_ACCESSOR(mode) \
+	bool preempt_model_##mode(void)						 \
+	{									 \
+		WARN_ON_ONCE(preempt_dynamic_mode == preempt_dynamic_undefined); \
+		return preempt_dynamic_mode == preempt_dynamic_##mode;		 \
+	}									 \
+	EXPORT_SYMBOL_GPL(preempt_model_##mode)
+
+PREEMPT_MODEL_ACCESSOR(none);
+PREEMPT_MODEL_ACCESSOR(voluntary);
+PREEMPT_MODEL_ACCESSOR(full);
+
 #else /* !CONFIG_PREEMPT_DYNAMIC */
 
 static inline void preempt_dynamic_init(void) { }

kernel/smp.c

@@ -183,7 +183,9 @@ static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
 static DEFINE_PER_CPU(void *, cur_csd_info);
 static DEFINE_PER_CPU(struct cfd_seq_local, cfd_seq_local);
 
-#define CSD_LOCK_TIMEOUT (5ULL * NSEC_PER_SEC)
+static ulong csd_lock_timeout = 5000;  /* CSD lock timeout in milliseconds. */
+module_param(csd_lock_timeout, ulong, 0444);
+
 static atomic_t csd_bug_count = ATOMIC_INIT(0);
 static u64 cfd_seq;
 
@@ -329,6 +331,7 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 *
 	u64 ts2, ts_delta;
 	call_single_data_t *cpu_cur_csd;
 	unsigned int flags = READ_ONCE(csd->node.u_flags);
+	unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC;
 
 	if (!(flags & CSD_FLAG_LOCK)) {
 		if (!unlikely(*bug_id))
@@ -341,7 +344,7 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 *
 
 	ts2 = sched_clock();
 	ts_delta = ts2 - *ts1;
-	if (likely(ts_delta <= CSD_LOCK_TIMEOUT))
+	if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0))
 		return false;
 
 	firsttime = !*bug_id;

kernel/trace/Kconfig

@@ -144,6 +144,7 @@ config TRACING
 	select BINARY_PRINTF
 	select EVENT_TRACING
 	select TRACE_CLOCK
+	select TASKS_RCU if PREEMPTION
 
 config GENERIC_TRACER
 	bool

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

@@ -301,7 +301,7 @@ specify_qemu_cpus () {
 			echo $2 -smp $3
 			;;
 		qemu-system-ppc64)
-			nt="`lscpu | grep '^NUMA node0' | sed -e 's/^[^,]*,\([0-9]*\),.*$/\1/'`"
+			nt="`lscpu | sed -n 's/^Thread(s) per core:\s*//p'`"
 			echo $2 -smp cores=`expr \( $3 + $nt - 1 \) / $nt`,threads=$nt
 			;;
 		esac

tools/testing/selftests/rcutorture/bin/kvm-find-errors.sh

@@ -36,7 +36,7 @@ do
 	then
 		egrep "error:|warning:|^ld: .*undefined reference to" < $i > $i.diags
 		files="$files $i.diags $i"
-	elif ! test -f ${scenariobasedir}/vmlinux
+	elif ! test -f ${scenariobasedir}/vmlinux && ! test -f "${rundir}/re-run"
 	then
 		echo No ${scenariobasedir}/vmlinux file > $i.diags
 		files="$files $i.diags $i"

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

@@ -33,7 +33,12 @@ do
 		TORTURE_SUITE="`cat $i/../torture_suite`"
 		configfile=`echo $i | sed -e 's,^.*/,,'`
 		rm -f $i/console.log.*.diags
-		kvm-recheck-${TORTURE_SUITE}.sh $i
+		case "${TORTURE_SUITE}" in
+		X*)
+			;;
+		*)
+			kvm-recheck-${TORTURE_SUITE}.sh $i
+		esac
 		if test -f "$i/qemu-retval" && test "`cat $i/qemu-retval`" -ne 0 && test "`cat $i/qemu-retval`" -ne 137
 		then
 			echo QEMU error, output:

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

@@ -138,14 +138,14 @@ chmod +x $T/bin/kvm-remote-*.sh
 # Check first to avoid the need for cleanup for system-name typos
 for i in $systems
 do
-	ncpus="`ssh $i getconf _NPROCESSORS_ONLN 2> /dev/null`"
-	echo $i: $ncpus CPUs " " `date` | tee -a "$oldrun/remote-log"
+	ncpus="`ssh -o BatchMode=yes $i getconf _NPROCESSORS_ONLN 2> /dev/null`"
 	ret=$?
 	if test "$ret" -ne 0
 	then
 		echo System $i unreachable, giving up. | tee -a "$oldrun/remote-log"
 		exit 4
 	fi
+	echo $i: $ncpus CPUs " " `date` | tee -a "$oldrun/remote-log"
 done
 
 # Download and expand the tarball on all systems.
@@ -153,14 +153,14 @@ echo Build-products tarball: `du -h $T/binres.tgz` | tee -a "$oldrun/remote-log"
 for i in $systems
 do
 	echo Downloading tarball to $i `date` | tee -a "$oldrun/remote-log"
-	cat $T/binres.tgz | ssh $i "cd /tmp; tar -xzf -"
+	cat $T/binres.tgz | ssh -o BatchMode=yes $i "cd /tmp; tar -xzf -"
 	ret=$?
 	tries=0
 	while test "$ret" -ne 0
 	do
 		echo Unable to download $T/binres.tgz to system $i, waiting and then retrying.  $tries prior retries. | tee -a "$oldrun/remote-log"
 		sleep 60
-		cat $T/binres.tgz | ssh $i "cd /tmp; tar -xzf -"
+		cat $T/binres.tgz | ssh -o BatchMode=yes $i "cd /tmp; tar -xzf -"
 		ret=$?
 		if test "$ret" -ne 0
 		then
@@ -185,7 +185,7 @@ checkremotefile () {
 
 	while :
 	do
-		ssh $1 "test -f \"$2\""
+		ssh -o BatchMode=yes $1 "test -f \"$2\""
 		ret=$?
 		if test "$ret" -eq 255
 		then
@@ -228,7 +228,7 @@ startbatches () {
 		then
 			continue # System still running last test, skip.
 		fi
-		ssh "$i" "cd \"$resdir/$ds\"; touch remote.run; PATH=\"$T/bin:$PATH\" nohup kvm-remote-$curbatch.sh > kvm-remote-$curbatch.sh.out 2>&1 &" 1>&2
+		ssh -o BatchMode=yes "$i" "cd \"$resdir/$ds\"; touch remote.run; PATH=\"$T/bin:$PATH\" nohup kvm-remote-$curbatch.sh > kvm-remote-$curbatch.sh.out 2>&1 &" 1>&2
 		ret=$?
 		if test "$ret" -ne 0
 		then
@@ -267,7 +267,7 @@ do
 		sleep 30
 	done
 	echo " ---" Collecting results from $i `date` | tee -a "$oldrun/remote-log"
-	( cd "$oldrun"; ssh $i "cd $rundir; tar -czf - kvm-remote-*.sh.out */console.log */kvm-test-1-run*.sh.out */qemu[_-]pid */qemu-retval */qemu-affinity; rm -rf $T > /dev/null 2>&1" | tar -xzf - )
+	( cd "$oldrun"; ssh -o BatchMode=yes $i "cd $rundir; tar -czf - kvm-remote-*.sh.out */console.log */kvm-test-1-run*.sh.out */qemu[_-]pid */qemu-retval */qemu-affinity; rm -rf $T > /dev/null 2>&1" | tar -xzf - )
 done
 
 ( kvm-end-run-stats.sh "$oldrun" "$starttime"; echo $? > $T/exitcode ) | tee -a "$oldrun/remote-log"

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

@@ -44,6 +44,7 @@ TORTURE_KCONFIG_KASAN_ARG=""
 TORTURE_KCONFIG_KCSAN_ARG=""
 TORTURE_KMAKE_ARG=""
 TORTURE_QEMU_MEM=512
+torture_qemu_mem_default=1
 TORTURE_REMOTE=
 TORTURE_SHUTDOWN_GRACE=180
 TORTURE_SUITE=rcu
@@ -86,7 +87,7 @@ usage () {
 	echo "       --remote"
 	echo "       --results absolute-pathname"
 	echo "       --shutdown-grace seconds"
-	echo "       --torture lock|rcu|rcuscale|refscale|scf"
+	echo "       --torture lock|rcu|rcuscale|refscale|scf|X*"
 	echo "       --trust-make"
 	exit 1
 }
@@ -180,6 +181,10 @@ do
 		;;
 	--kasan)
 		TORTURE_KCONFIG_KASAN_ARG="CONFIG_DEBUG_INFO=y CONFIG_KASAN=y"; export TORTURE_KCONFIG_KASAN_ARG
+		if test -n "$torture_qemu_mem_default"
+		then
+			TORTURE_QEMU_MEM=2G
+		fi
 		;;
 	--kconfig|--kconfigs)
 		checkarg --kconfig "(Kconfig options)" $# "$2" '^CONFIG_[A-Z0-9_]\+=\([ynm]\|[0-9]\+\)\( CONFIG_[A-Z0-9_]\+=\([ynm]\|[0-9]\+\)\)*$' '^error$'
@@ -202,6 +207,7 @@ do
 	--memory)
 		checkarg --memory "(memory size)" $# "$2" '^[0-9]\+[MG]\?$' error
 		TORTURE_QEMU_MEM=$2
+		torture_qemu_mem_default=
 		shift
 		;;
 	--no-initrd)
@@ -231,7 +237,7 @@ do
 		shift
 		;;
 	--torture)
-		checkarg --torture "(suite name)" "$#" "$2" '^\(lock\|rcu\|rcuscale\|refscale\|scf\)$' '^--'
+		checkarg --torture "(suite name)" "$#" "$2" '^\(lock\|rcu\|rcuscale\|refscale\|scf\|X.*\)$' '^--'
 		TORTURE_SUITE=$2
 		TORTURE_MOD="`echo $TORTURE_SUITE | sed -e 's/^\(lock\|rcu\|scf\)$/\1torture/'`"
 		shift

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

@@ -54,6 +54,7 @@ do_kvfree=yes
 do_kasan=yes
 do_kcsan=no
 do_clocksourcewd=yes
+do_rt=yes
 
 # doyesno - Helper function for yes/no arguments
 function doyesno () {
@@ -82,6 +83,7 @@ usage () {
 	echo "       --do-rcuscale / --do-no-rcuscale"
 	echo "       --do-rcutorture / --do-no-rcutorture"
 	echo "       --do-refscale / --do-no-refscale"
+	echo "       --do-rt / --do-no-rt"
 	echo "       --do-scftorture / --do-no-scftorture"
 	echo "       --duration [ <minutes> | <hours>h | <days>d ]"
 	echo "       --kcsan-kmake-arg kernel-make-arguments"
@@ -118,6 +120,7 @@ do
 		do_scftorture=yes
 		do_rcuscale=yes
 		do_refscale=yes
+		do_rt=yes
 		do_kvfree=yes
 		do_kasan=yes
 		do_kcsan=yes
@@ -148,6 +151,7 @@ do
 		do_scftorture=no
 		do_rcuscale=no
 		do_refscale=no
+		do_rt=no
 		do_kvfree=no
 		do_kasan=no
 		do_kcsan=no
@@ -162,6 +166,9 @@ do
 	--do-refscale|--do-no-refscale)
 		do_refscale=`doyesno "$1" --do-refscale`
 		;;
+	--do-rt|--do-no-rt)
+		do_rt=`doyesno "$1" --do-rt`
+		;;
 	--do-scftorture|--do-no-scftorture)
 		do_scftorture=`doyesno "$1" --do-scftorture`
 		;;
@@ -322,6 +329,7 @@ then
 	echo " --- make clean" > "$amcdir/Make.out" 2>&1
 	make -j$MAKE_ALLOTED_CPUS clean >> "$amcdir/Make.out" 2>&1
 	echo " --- make allmodconfig" >> "$amcdir/Make.out" 2>&1
+	cp .config $amcdir
 	make -j$MAKE_ALLOTED_CPUS allmodconfig >> "$amcdir/Make.out" 2>&1
 	echo " --- make " >> "$amcdir/Make.out" 2>&1
 	make -j$MAKE_ALLOTED_CPUS >> "$amcdir/Make.out" 2>&1
@@ -350,8 +358,19 @@ fi
 
 if test "$do_scftorture" = "yes"
 then
-	torture_bootargs="scftorture.nthreads=$HALF_ALLOTED_CPUS torture.disable_onoff_at_boot"
-	torture_set "scftorture" tools/testing/selftests/rcutorture/bin/kvm.sh --torture scf --allcpus --duration "$duration_scftorture" --configs "$configs_scftorture" --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory 1G --trust-make
+	torture_bootargs="scftorture.nthreads=$HALF_ALLOTED_CPUS torture.disable_onoff_at_boot csdlock_debug=1"
+	torture_set "scftorture" tools/testing/selftests/rcutorture/bin/kvm.sh --torture scf --allcpus --duration "$duration_scftorture" --configs "$configs_scftorture" --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory 2G --trust-make
+fi
+
+if test "$do_rt" = "yes"
+then
+	# With all post-boot grace periods forced to normal.
+	torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcupdate.rcu_normal=1"
+	torture_set "rcurttorture" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --trust-make
+
+	# With all post-boot grace periods forced to expedited.
+	torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcupdate.rcu_expedited=1"
+	torture_set "rcurttorture-exp" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --trust-make
 fi
 
 if test "$do_refscale" = yes
@@ -363,7 +382,7 @@ fi
 for prim in $primlist
 do
 	torture_bootargs="refscale.scale_type="$prim" refscale.nreaders=$HALF_ALLOTED_CPUS refscale.loops=10000 refscale.holdoff=20 torture.disable_onoff_at_boot"
-	torture_set "refscale-$prim" tools/testing/selftests/rcutorture/bin/kvm.sh --torture refscale --allcpus --duration 5 --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --bootargs "verbose_batched=$VERBOSE_BATCH_CPUS torture.verbose_sleep_frequency=8 torture.verbose_sleep_duration=$VERBOSE_BATCH_CPUS" --trust-make
+	torture_set "refscale-$prim" tools/testing/selftests/rcutorture/bin/kvm.sh --torture refscale --allcpus --duration 5 --kconfig "CONFIG_TASKS_TRACE_RCU=y CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --bootargs "verbose_batched=$VERBOSE_BATCH_CPUS torture.verbose_sleep_frequency=8 torture.verbose_sleep_duration=$VERBOSE_BATCH_CPUS" --trust-make
 done
 
 if test "$do_rcuscale" = yes
@@ -375,13 +394,13 @@ fi
 for prim in $primlist
 do
 	torture_bootargs="rcuscale.scale_type="$prim" rcuscale.nwriters=$HALF_ALLOTED_CPUS rcuscale.holdoff=20 torture.disable_onoff_at_boot"
-	torture_set "rcuscale-$prim" tools/testing/selftests/rcutorture/bin/kvm.sh --torture rcuscale --allcpus --duration 5 --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --trust-make
+	torture_set "rcuscale-$prim" tools/testing/selftests/rcutorture/bin/kvm.sh --torture rcuscale --allcpus --duration 5 --kconfig "CONFIG_TASKS_TRACE_RCU=y CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --trust-make
 done
 
 if test "$do_kvfree" = "yes"
 then
 	torture_bootargs="rcuscale.kfree_rcu_test=1 rcuscale.kfree_nthreads=16 rcuscale.holdoff=20 rcuscale.kfree_loops=10000 torture.disable_onoff_at_boot"
-	torture_set "rcuscale-kvfree" tools/testing/selftests/rcutorture/bin/kvm.sh --torture rcuscale --allcpus --duration 10 --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory 1G --trust-make
+	torture_set "rcuscale-kvfree" tools/testing/selftests/rcutorture/bin/kvm.sh --torture rcuscale --allcpus --duration 10 --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory 2G --trust-make
 fi
 
 if test "$do_clocksourcewd" = "yes"

tools/testing/selftests/rcutorture/configs/rcu/RUDE01

@@ -8,3 +8,5 @@ CONFIG_DEBUG_LOCK_ALLOC=y
 CONFIG_PROVE_LOCKING=y
 #CHECK#CONFIG_PROVE_RCU=y
 CONFIG_RCU_EXPERT=y
+CONFIG_FORCE_TASKS_RUDE_RCU=y
+#CHECK#CONFIG_TASKS_RUDE_RCU=y

tools/testing/selftests/rcutorture/configs/rcu/SRCU-N

@@ -6,3 +6,5 @@ CONFIG_PREEMPT_NONE=y
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=n
 #CHECK#CONFIG_RCU_EXPERT=n
+CONFIG_KPROBES=n
+CONFIG_FTRACE=n

tools/testing/selftests/rcutorture/configs/rcu/TASKS01

@@ -7,4 +7,5 @@ CONFIG_PREEMPT=y
 CONFIG_DEBUG_LOCK_ALLOC=y
 CONFIG_PROVE_LOCKING=y
 #CHECK#CONFIG_PROVE_RCU=y
+CONFIG_TASKS_RCU=y
 CONFIG_RCU_EXPERT=y

tools/testing/selftests/rcutorture/configs/rcu/TASKS02

@@ -2,3 +2,7 @@ CONFIG_SMP=n
 CONFIG_PREEMPT_NONE=y
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=n
+CONFIG_PREEMPT_DYNAMIC=n
+#CHECK#CONFIG_TASKS_RCU=y
+CONFIG_FORCE_TASKS_RCU=y
+CONFIG_RCU_EXPERT=y

tools/testing/selftests/rcutorture/configs/rcu/TASKS02.boot

 rcutorture.torture_type=tasks
+rcutorture.stat_interval=60

tools/testing/selftests/rcutorture/configs/rcu/TASKS03

@@ -7,3 +7,5 @@ CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=n
 CONFIG_NO_HZ_FULL=y
 #CHECK#CONFIG_RCU_EXPERT=n
+CONFIG_TASKS_RCU=y
+CONFIG_RCU_EXPERT=y

tools/testing/selftests/rcutorture/configs/rcu/TRACE01

@@ -4,8 +4,11 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=y
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=n
+CONFIG_PREEMPT_DYNAMIC=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_PROVE_LOCKING=n
 #CHECK#CONFIG_PROVE_RCU=n
+CONFIG_FORCE_TASKS_TRACE_RCU=y
+#CHECK#CONFIG_TASKS_TRACE_RCU=y
 CONFIG_TASKS_TRACE_RCU_READ_MB=y
 CONFIG_RCU_EXPERT=y

tools/testing/selftests/rcutorture/configs/rcu/TRACE02

@@ -7,5 +7,7 @@ CONFIG_PREEMPT=y
 CONFIG_DEBUG_LOCK_ALLOC=y
 CONFIG_PROVE_LOCKING=y
 #CHECK#CONFIG_PROVE_RCU=y
+CONFIG_FORCE_TASKS_TRACE_RCU=y
+#CHECK#CONFIG_TASKS_TRACE_RCU=y
 CONFIG_TASKS_TRACE_RCU_READ_MB=n
 CONFIG_RCU_EXPERT=y

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

 CONFIG_SMP=y
 CONFIG_NR_CPUS=8
-CONFIG_PREEMPT_NONE=y
-CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=y
 CONFIG_PREEMPT=n
+CONFIG_PREEMPT_DYNAMIC=n
 #CHECK#CONFIG_TREE_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=n

tools/testing/selftests/rcutorture/configs/rcu/TREE07

@@ -3,6 +3,7 @@ CONFIG_NR_CPUS=16
 CONFIG_PREEMPT_NONE=y
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=n
+CONFIG_PREEMPT_DYNAMIC=n
 #CHECK#CONFIG_TREE_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=n

tools/testing/selftests/rcutorture/configs/rcu/TREE09

@@ -13,3 +13,5 @@ CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 #CHECK#CONFIG_RCU_EXPERT=n
+CONFIG_KPROBES=n
+CONFIG_FTRACE=n

tools/testing/selftests/rcutorture/configs/rcu/TREE10

@@ -3,6 +3,7 @@ CONFIG_NR_CPUS=56
 CONFIG_PREEMPT_NONE=y
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=n
+CONFIG_PREEMPT_DYNAMIC=n
 #CHECK#CONFIG_TREE_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y

tools/testing/selftests/rcutorture/configs/rcu/ver_functions.sh

@@ -9,7 +9,7 @@
 
 # rcutorture_param_n_barrier_cbs bootparam-string
 #
-# Adds n_barrier_cbs rcutorture module parameter to kernels having it.
+# Adds n_barrier_cbs rcutorture module parameter if not already specified.
 rcutorture_param_n_barrier_cbs () {
 	if echo $1 | grep -q "rcutorture\.n_barrier_cbs"
 	then
@@ -30,13 +30,25 @@ rcutorture_param_onoff () {
 	fi
 }
 
+# rcutorture_param_stat_interval bootparam-string
+#
+# Adds stat_interval rcutorture module parameter if not already specified.
+rcutorture_param_stat_interval () {
+	if echo $1 | grep -q "rcutorture\.stat_interval"
+	then
+		:
+	else
+		echo rcutorture.stat_interval=15
+	fi
+}
+
 # per_version_boot_params bootparam-string config-file seconds
 #
 # Adds per-version torture-module parameters to kernels supporting them.
 per_version_boot_params () {
 	echo $1 `rcutorture_param_onoff "$1" "$2"` \
 		`rcutorture_param_n_barrier_cbs "$1"` \
-		rcutorture.stat_interval=15 \
+		`rcutorture_param_stat_interval "$1"` \
 		rcutorture.shutdown_secs=$3 \
 		rcutorture.test_no_idle_hz=1 \
 		rcutorture.verbose=1

tools/testing/selftests/rcutorture/configs/rcuscale/CFcommon

 CONFIG_RCU_SCALE_TEST=y
 CONFIG_PRINTK_TIME=y
-CONFIG_TASKS_RCU_GENERIC=y
-CONFIG_TASKS_RCU=y
-CONFIG_TASKS_TRACE_RCU=y
+CONFIG_FORCE_TASKS_RCU=y
+#CHECK#CONFIG_TASKS_RCU=y
+CONFIG_FORCE_TASKS_TRACE_RCU=y
+#CHECK#CONFIG_TASKS_TRACE_RCU=y

tools/testing/selftests/rcutorture/configs/rcuscale/TREE

@@ -16,3 +16,5 @@ CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
 CONFIG_RCU_TRACE=y
+CONFIG_KPROBES=n
+CONFIG_FTRACE=n

tools/testing/selftests/rcutorture/configs/refscale/CFcommon

 CONFIG_RCU_REF_SCALE_TEST=y
 CONFIG_PRINTK_TIME=y
+CONFIG_FORCE_TASKS_RCU=y
+#CHECK#CONFIG_TASKS_RCU=y
+CONFIG_FORCE_TASKS_TRACE_RCU=y
+#CHECK#CONFIG_TASKS_TRACE_RCU=y

tools/testing/selftests/rcutorture/configs/refscale/NOPREEMPT

@@ -15,3 +15,5 @@ CONFIG_PROVE_LOCKING=n
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
+CONFIG_KPROBES=n
+CONFIG_FTRACE=n

tools/testing/selftests/rcutorture/configs/scf/NOPREEMPT

@@ -7,3 +7,5 @@ CONFIG_NO_HZ_IDLE=n
 CONFIG_NO_HZ_FULL=y
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_PROVE_LOCKING=n
+CONFIG_KPROBES=n
+CONFIG_FTRACE=n

tools/testing/selftests/rcutorture/configs/scf/PREEMPT

@@ -7,3 +7,4 @@ CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
 CONFIG_DEBUG_LOCK_ALLOC=y
 CONFIG_PROVE_LOCKING=y
+CONFIG_RCU_EXPERT=y

tools/testing/selftests/rcutorture/configs/scf/ver_functions.sh

@@ -25,6 +25,5 @@ per_version_boot_params () {
 	echo $1 `scftorture_param_onoff "$1" "$2"` \
 		scftorture.stat_interval=15 \
 		scftorture.shutdown_secs=$3 \
-		scftorture.verbose=1 \
-		scf
+		scftorture.verbose=1
 }