[PATCH tip/core/rcu 0/7] Real-time updates for 3.19

[PATCH tip/core/rcu 0/7] Real-time updates for 3.19

[Paul E. McKenney]

Hello!

This series contains real-time-related updates:

1.	Move RCU_NOCB_CPU to choice, courtesy of Stefan Hengelein.

2.	Place RCU_BOOST-specific variables under pre-existing #ifdef.

3.	Prevent synchronize_sched_expedited() from sending IPIs to
	idle and to nohz_full CPUs.

4.	Unify boost and kthread priorities, and allow this unified
	priority to be set at boot time, courtesy of Clark Williams.

5.	Remove redundant TREE_PREEMPT_RCU Kconfig option, courtesy of
	Pranith Kumar.

6.	Handle the possibility of a no-CBs CPU posting callbacks on
	their last pass through the idle loop by waking up the
	leader kthread after the CPU has gone completely offline.

7.	Fix rcuo online-time-creation reoganization bug, which seems
	to be a latent bug due to systems (wisely) bringing CPUs online
	in numerical order.

							Thanx, Paul

------------------------------------------------------------------------

 b/Documentation/RCU/rcu.txt                                                     |    4 
 b/Documentation/RCU/stallwarn.txt                                               |    8 -
 b/Documentation/RCU/trace.txt                                                   |    4 
 b/Documentation/RCU/whatisRCU.txt                                               |    2 
 b/Documentation/kernel-parameters.txt                                           |    6 +
 b/include/linux/init_task.h                                                     |    2 
 b/include/linux/rcupdate.h                                                      |    6 -
 b/include/linux/sched.h                                                         |    4 
 b/include/trace/events/rcu.h                                                    |    4 
 b/init/Kconfig                                                                  |   49 +++------
 b/kernel/rcu/Makefile                                                           |    2 
 b/kernel/rcu/tree.c                                                             |   44 +++++---
 b/kernel/rcu/tree.h                                                             |   10 -
 b/kernel/rcu/tree_plugin.h                                                      |   53 ++++++----
 b/kernel/rcu/update.c                                                           |    2 
 b/lib/Kconfig.debug                                                             |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE01                         |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE02                         |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE02-T                       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE03                         |    4 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE08                         |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE08-T                       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/TREE09                         |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P1-S-T-NH-SD-SMP-HP       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P2-2-t-nh-sd-SMP-hp       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P3-3-T-nh-SD-SMP-hp       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P4-A-t-NH-sd-SMP-HP       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P5-U-T-NH-sd-SMP-hp       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P1-S-T-NH-SD-SMP-HP      |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P2-2-t-nh-sd-SMP-hp      |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P3-3-T-nh-SD-SMP-hp      |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P4-A-t-NH-sd-SMP-HP      |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P5-U-T-NH-sd-SMP-hp      |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P6---t-nh-SD-smp-hp      |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP      |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-all  |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-none |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-hp      |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P1-S-T-NH-SD-SMP-HP       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P2-2-t-nh-sd-SMP-hp       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P3-3-T-nh-SD-SMP-hp       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P4-A-t-NH-sd-SMP-HP       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P5-U-T-NH-sd-SMP-hp       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P1-S-T-NH-SD-SMP-HP       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P2-2-t-nh-sd-SMP-hp       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P3-3-T-nh-SD-SMP-hp       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P4-A-t-NH-sd-SMP-HP       |    2 
 b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P5-U-T-NH-sd-SMP-hp       |    2 
 b/tools/testing/selftests/rcutorture/doc/TINY_RCU.txt                           |    2 
 b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt                   |   14 +-
 50 files changed, 157 insertions(+), 127 deletions(-)

[PATCH tip/core/rcu 1/7] init/Kconfig: move RCU_NOCB_CPU dependencies to choice

[Paul E. McKenney]

From: Stefan Hengelein <stefan.hengelein@fau.de>

Every choice item of the "Build-forced no-CBs CPUs" choice had a
dependency to RCU_NOCB_CPU.  It's more comprehensible if the choice
itself has the dependency instead of every choice item.  The choice
itself doesn't need to be visible if there are no items selectable
(i.e.  on arch/frv) or RCU_NOCB_CPU is not defined.

Signed-off-by: Stefan Hengelein <stefan.hengelein@fau.de>
Signed-off-by: Andreas Ruprecht <rupran@einserver.de>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 init/Kconfig | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 3ee28ae02cc8..0c9546ba56e8 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -739,6 +739,7 @@ config RCU_NOCB_CPU
 choice
 	prompt "Build-forced no-CBs CPUs"
 	default RCU_NOCB_CPU_NONE
+	depends on RCU_NOCB_CPU
 	help
 	  This option allows no-CBs CPUs (whose RCU callbacks are invoked
 	  from kthreads rather than from softirq context) to be specified
@@ -747,7 +748,6 @@ choice
 
 config RCU_NOCB_CPU_NONE
 	bool "No build_forced no-CBs CPUs"
-	depends on RCU_NOCB_CPU
 	help
 	  This option does not force any of the CPUs to be no-CBs CPUs.
 	  Only CPUs designated by the rcu_nocbs= boot parameter will be
@@ -761,7 +761,6 @@ config RCU_NOCB_CPU_NONE
 
 config RCU_NOCB_CPU_ZERO
 	bool "CPU 0 is a build_forced no-CBs CPU"
-	depends on RCU_NOCB_CPU
 	help
 	  This option forces CPU 0 to be a no-CBs CPU, so that its RCU
 	  callbacks are invoked by a per-CPU kthread whose name begins
@@ -776,7 +775,6 @@ config RCU_NOCB_CPU_ZERO
 
 config RCU_NOCB_CPU_ALL
 	bool "All CPUs are build_forced no-CBs CPUs"
-	depends on RCU_NOCB_CPU
 	help
 	  This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
 	  boot parameter will be ignored.  All CPUs' RCU callbacks will
-- 
1.8.1.5

[PATCH tip/core/rcu 2/7] rcu: Move RCU_BOOST variable declarations, eliminating #ifdef

[Paul E. McKenney]

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

There are some RCU_BOOST-specific per-CPU variable declarations that
are needlessly defined under #ifdef in kernel/rcu/tree.c.  This commit
therefore moves these declarations into a pre-existing #ifdef in
kernel/rcu/tree_plugin.h.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcu/tree.c        | 13 -------------
 kernel/rcu/tree_plugin.h | 17 +++++++++++++++--
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9815447d22e0..7f73c5edf8cf 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -152,19 +152,6 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active);
  */
 static int rcu_scheduler_fully_active __read_mostly;
 
-#ifdef CONFIG_RCU_BOOST
-
-/*
- * Control variables for per-CPU and per-rcu_node kthreads.  These
- * handle all flavors of RCU.
- */
-static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
-DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
-DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
-DEFINE_PER_CPU(char, rcu_cpu_has_work);
-
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
 static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
 static void invoke_rcu_core(void);
 static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c1d7f27bd38f..357891104ea0 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -33,11 +33,24 @@
 #define RCU_KTHREAD_PRIO 1
 
 #ifdef CONFIG_RCU_BOOST
+
 #include "../locking/rtmutex_common.h"
 #define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO
-#else
+
+/*
+ * Control variables for per-CPU and per-rcu_node kthreads.  These
+ * handle all flavors of RCU.
+ */
+static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
+DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
+DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
+DEFINE_PER_CPU(char, rcu_cpu_has_work);
+
+#else /* #ifdef CONFIG_RCU_BOOST */
+
 #define RCU_BOOST_PRIO RCU_KTHREAD_PRIO
-#endif
+
+#endif /* #else #ifdef CONFIG_RCU_BOOST */
 
 #ifdef CONFIG_RCU_NOCB_CPU
 static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
-- 
1.8.1.5

[PATCH tip/core/rcu 3/7] rcu: Avoid IPIing idle CPUs from synchronize_sched_expedited()

[Paul E. McKenney]

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

Currently, synchronize_sched_expedited() sends IPIs to all online CPUs,
even those that are idle or executing in nohz_full= userspace.  Because
idle CPUs and nohz_full= userspace CPUs are in extended quiescent states,
there is no need to IPI them in the first place.  This commit therefore
avoids IPIing CPUs that are already in extended quiescent states.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7f73c5edf8cf..9e3c20f117cd 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2950,6 +2950,9 @@ static int synchronize_sched_expedited_cpu_stop(void *data)
  */
 void synchronize_sched_expedited(void)
 {
+	cpumask_var_t cm;
+	bool cma = false;
+	int cpu;
 	long firstsnap, s, snap;
 	int trycount = 0;
 	struct rcu_state *rsp = &rcu_sched_state;
@@ -2984,11 +2987,26 @@ void synchronize_sched_expedited(void)
 	}
 	WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
 
+	/* Offline CPUs, idle CPUs, and any CPU we run on are quiescent. */
+	cma = zalloc_cpumask_var(&cm, GFP_KERNEL);
+	if (cma) {
+		cpumask_copy(cm, cpu_online_mask);
+		cpumask_clear_cpu(raw_smp_processor_id(), cm);
+		for_each_cpu(cpu, cm) {
+			struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+
+			if (!(atomic_add_return(0, &rdtp->dynticks) & 0x1))
+				cpumask_clear_cpu(cpu, cm);
+		}
+		if (cpumask_weight(cm) == 0)
+			goto all_cpus_idle;
+	}
+
 	/*
 	 * Each pass through the following loop attempts to force a
 	 * context switch on each CPU.
 	 */
-	while (try_stop_cpus(cpu_online_mask,
+	while (try_stop_cpus(cma ? cm : cpu_online_mask,
 			     synchronize_sched_expedited_cpu_stop,
 			     NULL) == -EAGAIN) {
 		put_online_cpus();
@@ -3000,6 +3018,7 @@ void synchronize_sched_expedited(void)
 			/* ensure test happens before caller kfree */
 			smp_mb__before_atomic(); /* ^^^ */
 			atomic_long_inc(&rsp->expedited_workdone1);
+			free_cpumask_var(cm);
 			return;
 		}
 
@@ -3009,6 +3028,7 @@ void synchronize_sched_expedited(void)
 		} else {
 			wait_rcu_gp(call_rcu_sched);
 			atomic_long_inc(&rsp->expedited_normal);
+			free_cpumask_var(cm);
 			return;
 		}
 
@@ -3018,6 +3038,7 @@ void synchronize_sched_expedited(void)
 			/* ensure test happens before caller kfree */
 			smp_mb__before_atomic(); /* ^^^ */
 			atomic_long_inc(&rsp->expedited_workdone2);
+			free_cpumask_var(cm);
 			return;
 		}
 
@@ -3032,6 +3053,7 @@ void synchronize_sched_expedited(void)
 			/* CPU hotplug operation in flight, use normal GP. */
 			wait_rcu_gp(call_rcu_sched);
 			atomic_long_inc(&rsp->expedited_normal);
+			free_cpumask_var(cm);
 			return;
 		}
 		snap = atomic_long_read(&rsp->expedited_start);
@@ -3039,6 +3061,9 @@ void synchronize_sched_expedited(void)
 	}
 	atomic_long_inc(&rsp->expedited_stoppedcpus);
 
+all_cpus_idle:
+	free_cpumask_var(cm);
+
 	/*
 	 * Everyone up to our most recent fetch is covered by our grace
 	 * period.  Update the counter, but only if our work is still
-- 
1.8.1.5

[PATCH tip/core/rcu 4/7] rcu: Unify boost and kthread priorities

[Paul E. McKenney]

From: Clark Williams <clark.williams@gmail.com>

Rename CONFIG_RCU_BOOST_PRIO to CONFIG_RCU_KTHREAD_PRIO and use this
value for both the per-CPU kthreads (rcuc/N) and the rcu boosting
threads (rcub/n).

Also, create the module_parameter rcutree.kthread_prio to be used on
the kernel command line at boot to set a new value (rcutree.kthread_prio=N).

Signed-off-by: Clark Williams <clark.williams@gmail.com>
[ paulmck: Ported to rcu/dev, applied Paul Bolle feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 Documentation/kernel-parameters.txt                |  6 ++++++
 init/Kconfig                                       | 23 +++++++++++-----------
 kernel/rcu/tree_plugin.h                           | 20 +++++++++----------
 .../selftests/rcutorture/configs/rcu/TREE03        |  2 +-
 .../selftests/rcutorture/doc/TREE_RCU-kconfig.txt  |  4 ++--
 5 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7dbe5ec9d9cd..7d3b3328bf5c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2922,6 +2922,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			quiescent states.  Units are jiffies, minimum
 			value is one, and maximum value is HZ.
 
+	rcutree.kthread_prio= 	 [KNL,BOOT]
+			Set the SCHED_FIFO priority of the RCU
+			per-CPU kthreads (rcuc/N). This value is also
+			used for the priority of the RCU boost threads
+			(rcub/N). Valid values are 1-99.
+
 	rcutree.rcu_nocb_leader_stride= [KNL]
 			Set the number of NOCB kthread groups, which
 			defaults to the square root of the number of
diff --git a/init/Kconfig b/init/Kconfig
index 0c9546ba56e8..15c299cc7c1e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -672,30 +672,31 @@ config RCU_BOOST
 	  Say Y here if you are working with real-time apps or heavy loads
 	  Say N here if you are unsure.
 
-config RCU_BOOST_PRIO
-	int "Real-time priority to boost RCU readers to"
+config RCU_KTHREAD_PRIO
+	int "Real-time priority to use for RCU worker threads"
 	range 1 99
 	depends on RCU_BOOST
 	default 1
 	help
-	  This option specifies the real-time priority to which long-term
-	  preempted RCU readers are to be boosted.  If you are working
-	  with a real-time application that has one or more CPU-bound
-	  threads running at a real-time priority level, you should set
-	  RCU_BOOST_PRIO to a priority higher then the highest-priority
-	  real-time CPU-bound thread.  The default RCU_BOOST_PRIO value
-	  of 1 is appropriate in the common case, which is real-time
+	  This option specifies the SCHED_FIFO priority value that will be
+	  assigned to the rcuc/n and rcub/n threads and is also the value
+	  used for RCU_BOOST (if enabled). If you are working with a
+	  real-time application that has one or more CPU-bound threads
+	  running at a real-time priority level, you should set
+	  RCU_KTHREAD_PRIO to a priority higher than the highest-priority
+	  real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
+	  value of 1 is appropriate in the common case, which is real-time
 	  applications that do not have any CPU-bound threads.
 
 	  Some real-time applications might not have a single real-time
 	  thread that saturates a given CPU, but instead might have
 	  multiple real-time threads that, taken together, fully utilize
-	  that CPU.  In this case, you should set RCU_BOOST_PRIO to
+	  that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
 	  a priority higher than the lowest-priority thread that is
 	  conspiring to prevent the CPU from running any non-real-time
 	  tasks.  For example, if one thread at priority 10 and another
 	  thread at priority 5 are between themselves fully consuming
-	  the CPU time on a given CPU, then RCU_BOOST_PRIO should be
+	  the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
 	  set to priority 6 or higher.
 
 	  Specify the real-time priority, or take the default if unsure.
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 357891104ea0..344f0e661515 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -30,12 +30,13 @@
 #include <linux/smpboot.h>
 #include "../time/tick-internal.h"
 
-#define RCU_KTHREAD_PRIO 1
-
 #ifdef CONFIG_RCU_BOOST
 
 #include "../locking/rtmutex_common.h"
-#define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO
+
+/* rcuc/rcub kthread realtime priority */
+static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
+module_param(kthread_prio, int, 0644);
 
 /*
  * Control variables for per-CPU and per-rcu_node kthreads.  These
@@ -46,11 +47,7 @@ DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
 DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 DEFINE_PER_CPU(char, rcu_cpu_has_work);
 
-#else /* #ifdef CONFIG_RCU_BOOST */
-
-#define RCU_BOOST_PRIO RCU_KTHREAD_PRIO
-
-#endif /* #else #ifdef CONFIG_RCU_BOOST */
+#endif /* #ifdef CONFIG_RCU_BOOST */
 
 #ifdef CONFIG_RCU_NOCB_CPU
 static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
@@ -98,6 +95,9 @@ static void __init rcu_bootup_announce_oddness(void)
 		pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
 	if (nr_cpu_ids != NR_CPUS)
 		pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
+#ifdef CONFIG_RCU_BOOST
+	pr_info("\tRCU kthread priority: %d.\n", kthread_prio);
+#endif
 }
 
 #ifdef CONFIG_TREE_PREEMPT_RCU
@@ -1339,7 +1339,7 @@ static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 	smp_mb__after_unlock_lock();
 	rnp->boost_kthread_task = t;
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
-	sp.sched_priority = RCU_BOOST_PRIO;
+	sp.sched_priority = kthread_prio;
 	sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
 	wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
 	return 0;
@@ -1356,7 +1356,7 @@ static void rcu_cpu_kthread_setup(unsigned int cpu)
 {
 	struct sched_param sp;
 
-	sp.sched_priority = RCU_KTHREAD_PRIO;
+	sp.sched_priority = kthread_prio;
 	sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
 }
 
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE03 b/tools/testing/selftests/rcutorture/configs/rcu/TREE03
index f4567fb3e332..b95f62efd6f2 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE03
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE03
@@ -17,5 +17,5 @@ CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_CPU_STALL_INFO=n
 CONFIG_RCU_CPU_STALL_VERBOSE=n
 CONFIG_RCU_BOOST=y
-CONFIG_RCU_BOOST_PRIO=2
+CONFIG_RCU_KTHREAD_PRIO=2
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
diff --git a/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
index 3e588db86a17..ab6e7b4103ac 100644
--- a/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
+++ b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
@@ -15,8 +15,8 @@ CONFIG_PREEMPT -- Do half.  (First three and #8.)
 CONFIG_PROVE_LOCKING -- Do all but two, covering CONFIG_PROVE_RCU and not.
 CONFIG_PROVE_RCU -- Do all but one under CONFIG_PROVE_LOCKING.
 CONFIG_RCU_BOOST -- one of TREE_PREEMPT_RCU.
-CONFIG_RCU_BOOST_PRIO -- set to 2 for _BOOST testing.
-CONFIG_RCU_CPU_STALL_INFO -- do one with and without _VERBOSE.
+CONFIG_RCU_KTHREAD_PRIO -- set to 2 for _BOOST testing.
+CONFIG_RCU_CPU_STALL_INFO -- Do one.
 CONFIG_RCU_CPU_STALL_VERBOSE -- do one with and without _INFO.
 CONFIG_RCU_FANOUT -- Cover hierarchy as currently, but overlap with others.
 CONFIG_RCU_FANOUT_EXACT -- Do one.
-- 
1.8.1.5

[PATCH tip/core/rcu 5/7] rcu: Remove redundant TREE_PREEMPT_RCU config option

[Paul E. McKenney]

From: Pranith Kumar <bobby.prani@gmail.com>

PREEMPT_RCU and TREE_PREEMPT_RCU serve the same function after
TINY_PREEMPT_RCU has been removed. This patch removes TREE_PREEMPT_RCU
and uses PREEMPT_RCU config option in its place.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 Documentation/RCU/rcu.txt                          |  4 ++--
 Documentation/RCU/stallwarn.txt                    |  8 ++++----
 Documentation/RCU/trace.txt                        |  4 ++--
 Documentation/RCU/whatisRCU.txt                    |  2 +-
 include/linux/init_task.h                          |  2 +-
 include/linux/rcupdate.h                           |  6 +++---
 include/linux/sched.h                              |  4 ++--
 include/trace/events/rcu.h                         |  4 ++--
 init/Kconfig                                       | 22 ++++++++--------------
 kernel/rcu/Makefile                                |  2 +-
 kernel/rcu/tree.h                                  | 10 +++++-----
 kernel/rcu/tree_plugin.h                           |  6 +++---
 kernel/rcu/update.c                                |  2 +-
 lib/Kconfig.debug                                  |  2 +-
 .../selftests/rcutorture/configs/rcu/TREE01        |  2 +-
 .../selftests/rcutorture/configs/rcu/TREE02        |  2 +-
 .../selftests/rcutorture/configs/rcu/TREE02-T      |  2 +-
 .../selftests/rcutorture/configs/rcu/TREE03        |  2 +-
 .../selftests/rcutorture/configs/rcu/TREE08        |  2 +-
 .../selftests/rcutorture/configs/rcu/TREE08-T      |  2 +-
 .../selftests/rcutorture/configs/rcu/TREE09        |  2 +-
 .../configs/rcu/v0.0/P1-S-T-NH-SD-SMP-HP           |  2 +-
 .../configs/rcu/v0.0/P2-2-t-nh-sd-SMP-hp           |  2 +-
 .../configs/rcu/v0.0/P3-3-T-nh-SD-SMP-hp           |  2 +-
 .../configs/rcu/v0.0/P4-A-t-NH-sd-SMP-HP           |  2 +-
 .../configs/rcu/v0.0/P5-U-T-NH-sd-SMP-hp           |  2 +-
 .../configs/rcu/v3.12/P1-S-T-NH-SD-SMP-HP          |  2 +-
 .../configs/rcu/v3.12/P2-2-t-nh-sd-SMP-hp          |  2 +-
 .../configs/rcu/v3.12/P3-3-T-nh-SD-SMP-hp          |  2 +-
 .../configs/rcu/v3.12/P4-A-t-NH-sd-SMP-HP          |  2 +-
 .../configs/rcu/v3.12/P5-U-T-NH-sd-SMP-hp          |  2 +-
 .../configs/rcu/v3.12/P6---t-nh-SD-smp-hp          |  2 +-
 .../configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP          |  2 +-
 .../configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-all      |  2 +-
 .../configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-none     |  2 +-
 .../configs/rcu/v3.12/P7-4-T-NH-SD-SMP-hp          |  2 +-
 .../configs/rcu/v3.3/P1-S-T-NH-SD-SMP-HP           |  2 +-
 .../configs/rcu/v3.3/P2-2-t-nh-sd-SMP-hp           |  2 +-
 .../configs/rcu/v3.3/P3-3-T-nh-SD-SMP-hp           |  2 +-
 .../configs/rcu/v3.3/P4-A-t-NH-sd-SMP-HP           |  2 +-
 .../configs/rcu/v3.3/P5-U-T-NH-sd-SMP-hp           |  2 +-
 .../configs/rcu/v3.5/P1-S-T-NH-SD-SMP-HP           |  2 +-
 .../configs/rcu/v3.5/P2-2-t-nh-sd-SMP-hp           |  2 +-
 .../configs/rcu/v3.5/P3-3-T-nh-SD-SMP-hp           |  2 +-
 .../configs/rcu/v3.5/P4-A-t-NH-sd-SMP-HP           |  2 +-
 .../configs/rcu/v3.5/P5-U-T-NH-sd-SMP-hp           |  2 +-
 .../testing/selftests/rcutorture/doc/TINY_RCU.txt  |  2 +-
 .../selftests/rcutorture/doc/TREE_RCU-kconfig.txt  | 10 +++++-----
 48 files changed, 74 insertions(+), 80 deletions(-)

diff --git a/Documentation/RCU/rcu.txt b/Documentation/RCU/rcu.txt
index bf778332a28f..745f429fda79 100644
--- a/Documentation/RCU/rcu.txt
+++ b/Documentation/RCU/rcu.txt
@@ -36,7 +36,7 @@ o	How can the updater tell when a grace period has completed
 	executed in user mode, or executed in the idle loop, we can
 	safely free up that item.
 
-	Preemptible variants of RCU (CONFIG_TREE_PREEMPT_RCU) get the
+	Preemptible variants of RCU (CONFIG_PREEMPT_RCU) get the
 	same effect, but require that the readers manipulate CPU-local
 	counters.  These counters allow limited types of blocking within
 	RCU read-side critical sections.  SRCU also uses CPU-local
@@ -81,7 +81,7 @@ o	I hear that RCU is patented?  What is with that?
 o	I hear that RCU needs work in order to support realtime kernels?
 
 	This work is largely completed.  Realtime-friendly RCU can be
-	enabled via the CONFIG_TREE_PREEMPT_RCU kernel configuration
+	enabled via the CONFIG_PREEMPT_RCU kernel configuration
 	parameter.  However, work is in progress for enabling priority
 	boosting of preempted RCU read-side critical sections.	This is
 	needed if you have CPU-bound realtime threads.
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index ef5a2fd4ff70..783e0720994d 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -77,7 +77,7 @@ This message indicates that CPU 5 detected that it was causing a stall,
 and that the stall was affecting RCU-sched.  This message will normally be
 followed by a stack dump of the offending CPU.  On TREE_RCU kernel builds,
 RCU and RCU-sched are implemented by the same underlying mechanism,
-while on TREE_PREEMPT_RCU kernel builds, RCU is instead implemented
+while on PREEMPT_RCU kernel builds, RCU is instead implemented
 by rcu_preempt_state.
 
 On the other hand, if the offending CPU fails to print out a stall-warning
@@ -89,7 +89,7 @@ INFO: rcu_bh_state detected stalls on CPUs/tasks: { 3 5 } (detected by 2, 2502 j
 This message indicates that CPU 2 detected that CPUs 3 and 5 were both
 causing stalls, and that the stall was affecting RCU-bh.  This message
 will normally be followed by stack dumps for each CPU.  Please note that
-TREE_PREEMPT_RCU builds can be stalled by tasks as well as by CPUs,
+PREEMPT_RCU builds can be stalled by tasks as well as by CPUs,
 and that the tasks will be indicated by PID, for example, "P3421".
 It is even possible for a rcu_preempt_state stall to be caused by both
 CPUs -and- tasks, in which case the offending CPUs and tasks will all
@@ -205,10 +205,10 @@ o	A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might
 o	A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that
 	is running at a higher priority than the RCU softirq threads.
 	This will prevent RCU callbacks from ever being invoked,
-	and in a CONFIG_TREE_PREEMPT_RCU kernel will further prevent
+	and in a CONFIG_PREEMPT_RCU kernel will further prevent
 	RCU grace periods from ever completing.  Either way, the
 	system will eventually run out of memory and hang.  In the
-	CONFIG_TREE_PREEMPT_RCU case, you might see stall-warning
+	CONFIG_PREEMPT_RCU case, you might see stall-warning
 	messages.
 
 o	A hardware or software issue shuts off the scheduler-clock
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
index 910870b15acd..b63b9bb3bc0c 100644
--- a/Documentation/RCU/trace.txt
+++ b/Documentation/RCU/trace.txt
@@ -8,7 +8,7 @@ The following sections describe the debugfs files and formats, first
 for rcutree and next for rcutiny.
 
 
-CONFIG_TREE_RCU and CONFIG_TREE_PREEMPT_RCU debugfs Files and Formats
+CONFIG_TREE_RCU and CONFIG_PREEMPT_RCU debugfs Files and Formats
 
 These implementations of RCU provide several debugfs directories under the
 top-level directory "rcu":
@@ -18,7 +18,7 @@ rcu/rcu_preempt
 rcu/rcu_sched
 
 Each directory contains files for the corresponding flavor of RCU.
-Note that rcu/rcu_preempt is only present for CONFIG_TREE_PREEMPT_RCU.
+Note that rcu/rcu_preempt is only present for CONFIG_PREEMPT_RCU.
 For CONFIG_TREE_RCU, the RCU flavor maps onto the RCU-sched flavor,
 so that activity for both appears in rcu/rcu_sched.
 
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index e48c57f1943b..88dfce182f66 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -137,7 +137,7 @@ rcu_read_lock()
 	Used by a reader to inform the reclaimer that the reader is
 	entering an RCU read-side critical section.  It is illegal
 	to block while in an RCU read-side critical section, though
-	kernels built with CONFIG_TREE_PREEMPT_RCU can preempt RCU
+	kernels built with CONFIG_PREEMPT_RCU can preempt RCU
 	read-side critical sections.  Any RCU-protected data structure
 	accessed during an RCU read-side critical section is guaranteed to
 	remain unreclaimed for the full duration of that critical section.
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 77fc43f8fb72..d996aef8044f 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -102,7 +102,7 @@ extern struct group_info init_groups;
 #define INIT_IDS
 #endif
 
-#ifdef CONFIG_TREE_PREEMPT_RCU
+#ifdef CONFIG_PREEMPT_RCU
 #define INIT_TASK_RCU_TREE_PREEMPT()					\
 	.rcu_blocked_node = NULL,
 #else
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index a4a819ffb2d1..295bb4595de6 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -57,7 +57,7 @@ enum rcutorture_type {
 	INVALID_RCU_FLAVOR
 };
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
 void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
 			    unsigned long *gpnum, unsigned long *completed);
 void rcutorture_record_test_transition(void);
@@ -365,7 +365,7 @@ typedef void call_rcu_func_t(struct rcu_head *head,
 			     void (*func)(struct rcu_head *head));
 void wait_rcu_gp(call_rcu_func_t crf);
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
 #include <linux/rcutree.h>
 #elif defined(CONFIG_TINY_RCU)
 #include <linux/rcutiny.h>
@@ -852,7 +852,7 @@ static inline void rcu_preempt_sleep_check(void)
  *
  * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU),
  * it is illegal to block while in an RCU read-side critical section.
- * In preemptible RCU implementations (TREE_PREEMPT_RCU) in CONFIG_PREEMPT
+ * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPT
  * kernel builds, RCU read-side critical sections may be preempted,
  * but explicit blocking is illegal.  Finally, in preemptible RCU
  * implementations in real-time (with -rt patchset) kernel builds, RCU
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5e344bbe63ec..706a9f744909 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1278,9 +1278,9 @@ struct task_struct {
 	union rcu_special rcu_read_unlock_special;
 	struct list_head rcu_node_entry;
 #endif /* #ifdef CONFIG_PREEMPT_RCU */
-#ifdef CONFIG_TREE_PREEMPT_RCU
+#ifdef CONFIG_PREEMPT_RCU
 	struct rcu_node *rcu_blocked_node;
-#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
 #ifdef CONFIG_TASKS_RCU
 	unsigned long rcu_tasks_nvcsw;
 	bool rcu_tasks_holdout;
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index e335e7d8c6c2..c78e88ce5ea3 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -36,7 +36,7 @@ TRACE_EVENT(rcu_utilization,
 
 #ifdef CONFIG_RCU_TRACE
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
 
 /*
  * Tracepoint for grace-period events.  Takes a string identifying the
@@ -345,7 +345,7 @@ TRACE_EVENT(rcu_fqs,
 		  __entry->cpu, __entry->qsevent)
 );
 
-#endif /* #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) */
+#endif /* #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) */
 
 /*
  * Tracepoint for dyntick-idle entry/exit events.  These take a string
diff --git a/init/Kconfig b/init/Kconfig
index 15c299cc7c1e..5ac596e2cb4b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -477,7 +477,7 @@ config TREE_RCU
 	  thousands of CPUs.  It also scales down nicely to
 	  smaller systems.
 
-config TREE_PREEMPT_RCU
+config PREEMPT_RCU
 	bool "Preemptible tree-based hierarchical RCU"
 	depends on PREEMPT
 	select IRQ_WORK
@@ -501,12 +501,6 @@ config TINY_RCU
 
 endchoice
 
-config PREEMPT_RCU
-	def_bool TREE_PREEMPT_RCU
-	help
-	  This option enables preemptible-RCU code that is common between
-	  TREE_PREEMPT_RCU and, in the old days, TINY_PREEMPT_RCU.
-
 config TASKS_RCU
 	bool "Task_based RCU implementation using voluntary context switch"
 	default n
@@ -518,7 +512,7 @@ config TASKS_RCU
 	  If unsure, say N.
 
 config RCU_STALL_COMMON
-	def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
+	def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
 	help
 	  This option enables RCU CPU stall code that is common between
 	  the TINY and TREE variants of RCU.  The purpose is to allow
@@ -576,7 +570,7 @@ config RCU_FANOUT
 	int "Tree-based hierarchical RCU fanout value"
 	range 2 64 if 64BIT
 	range 2 32 if !64BIT
-	depends on TREE_RCU || TREE_PREEMPT_RCU
+	depends on TREE_RCU || PREEMPT_RCU
 	default 64 if 64BIT
 	default 32 if !64BIT
 	help
@@ -596,7 +590,7 @@ config RCU_FANOUT_LEAF
 	int "Tree-based hierarchical RCU leaf-level fanout value"
 	range 2 RCU_FANOUT if 64BIT
 	range 2 RCU_FANOUT if !64BIT
-	depends on TREE_RCU || TREE_PREEMPT_RCU
+	depends on TREE_RCU || PREEMPT_RCU
 	default 16
 	help
 	  This option controls the leaf-level fanout of hierarchical
@@ -621,7 +615,7 @@ config RCU_FANOUT_LEAF
 
 config RCU_FANOUT_EXACT
 	bool "Disable tree-based hierarchical RCU auto-balancing"
-	depends on TREE_RCU || TREE_PREEMPT_RCU
+	depends on TREE_RCU || PREEMPT_RCU
 	default n
 	help
 	  This option forces use of the exact RCU_FANOUT value specified,
@@ -652,11 +646,11 @@ config RCU_FAST_NO_HZ
 	  Say N if you are unsure.
 
 config TREE_RCU_TRACE
-	def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
+	def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
 	select DEBUG_FS
 	help
 	  This option provides tracing for the TREE_RCU and
-	  TREE_PREEMPT_RCU implementations, permitting Makefile to
+	  PREEMPT_RCU implementations, permitting Makefile to
 	  trivially select kernel/rcutree_trace.c.
 
 config RCU_BOOST
@@ -716,7 +710,7 @@ config RCU_BOOST_DELAY
 
 config RCU_NOCB_CPU
 	bool "Offload RCU callback processing from boot-selected CPUs"
-	depends on TREE_RCU || TREE_PREEMPT_RCU
+	depends on TREE_RCU || PREEMPT_RCU
 	default n
 	help
 	  Use this option to reduce OS jitter for aggressive HPC or
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index 807ccfbf69b3..e6fae503d1bc 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -1,6 +1,6 @@
 obj-y += update.o srcu.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_TREE_RCU) += tree.o
-obj-$(CONFIG_TREE_PREEMPT_RCU) += tree.o
+obj-$(CONFIG_PREEMPT_RCU) += tree.o
 obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.o
 obj-$(CONFIG_TINY_RCU) += tiny.o
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index bbdc45d8d74f..66cde5109c7d 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -139,7 +139,7 @@ struct rcu_node {
 	unsigned long expmask;	/* Groups that have ->blkd_tasks */
 				/*  elements that need to drain to allow the */
 				/*  current expedited grace period to */
-				/*  complete (only for TREE_PREEMPT_RCU). */
+				/*  complete (only for PREEMPT_RCU). */
 	unsigned long qsmaskinit;
 				/* Per-GP initial value for qsmask & expmask. */
 	unsigned long grpmask;	/* Mask to apply to parent qsmask. */
@@ -530,10 +530,10 @@ DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
 extern struct rcu_state rcu_bh_state;
 DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
 
-#ifdef CONFIG_TREE_PREEMPT_RCU
+#ifdef CONFIG_PREEMPT_RCU
 extern struct rcu_state rcu_preempt_state;
 DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
-#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
 
 #ifdef CONFIG_RCU_BOOST
 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
@@ -563,10 +563,10 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 static void rcu_preempt_check_callbacks(int cpu);
 void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
-#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU)
 static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
 			       bool wake);
-#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
+#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU) */
 static void __init __rcu_init_preempt(void);
 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 344f0e661515..6d07fb402e84 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -100,7 +100,7 @@ static void __init rcu_bootup_announce_oddness(void)
 #endif
 }
 
-#ifdef CONFIG_TREE_PREEMPT_RCU
+#ifdef CONFIG_PREEMPT_RCU
 
 RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu);
 static struct rcu_state *rcu_state_p = &rcu_preempt_state;
@@ -932,7 +932,7 @@ void exit_rcu(void)
 	__rcu_read_unlock();
 }
 
-#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+#else /* #ifdef CONFIG_PREEMPT_RCU */
 
 static struct rcu_state *rcu_state_p = &rcu_sched_state;
 
@@ -1083,7 +1083,7 @@ void exit_rcu(void)
 {
 }
 
-#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
+#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
 
 #ifdef CONFIG_RCU_BOOST
 
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 3ef8ba58694e..27a5b174b2a4 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -306,7 +306,7 @@ struct debug_obj_descr rcuhead_debug_descr = {
 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
 void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
 			       unsigned long secs,
 			       unsigned long c_old, unsigned long c)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 4e35a5d767ed..12e7b020539f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1252,7 +1252,7 @@ config RCU_CPU_STALL_VERBOSE
 
 config RCU_CPU_STALL_INFO
 	bool "Print additional diagnostics on RCU CPU stall"
-	depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
+	depends on (TREE_RCU || PREEMPT_RCU) && DEBUG_KERNEL
 	default n
 	help
 	  For each stalled CPU that is aware of the current RCU grace
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE01 b/tools/testing/selftests/rcutorture/configs/rcu/TREE01
index 38e3895759dd..69f8e5878a58 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE01
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE01
@@ -2,7 +2,7 @@ CONFIG_SMP=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE02 b/tools/testing/selftests/rcutorture/configs/rcu/TREE02
index ea119ba2f7d4..fc29c6297197 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE02
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE02
@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=8
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE02-T b/tools/testing/selftests/rcutorture/configs/rcu/TREE02-T
index 19cf9485f48a..778ec567a472 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE02-T
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE02-T
@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=8
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE03 b/tools/testing/selftests/rcutorture/configs/rcu/TREE03
index b95f62efd6f2..a022f0332303 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE03
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE03
@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=8
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=y
 CONFIG_NO_HZ_IDLE=n
 CONFIG_NO_HZ_FULL=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE08 b/tools/testing/selftests/rcutorture/configs/rcu/TREE08
index 69a2e255bf98..6f8609d2d072 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE08
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE08
@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=16
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE08-T b/tools/testing/selftests/rcutorture/configs/rcu/TREE08-T
index a0f32fb8f17e..4e55bee2d3f8 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE08-T
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE08-T
@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=16
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE09 b/tools/testing/selftests/rcutorture/configs/rcu/TREE09
index b7a62a540ad1..47e2ecd1844f 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE09
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE09
@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=1
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P1-S-T-NH-SD-SMP-HP b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P1-S-T-NH-SD-SMP-HP
index f72402d7c13d..dd7bd4d2d85a 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P1-S-T-NH-SD-SMP-HP
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P1-S-T-NH-SD-SMP-HP
@@ -9,7 +9,7 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P2-2-t-nh-sd-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P2-2-t-nh-sd-SMP-hp
index 0f3b667d2a9f..81d484362820 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P2-2-t-nh-sd-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P2-2-t-nh-sd-SMP-hp
@@ -10,7 +10,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P3-3-T-nh-SD-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P3-3-T-nh-SD-SMP-hp
index b035e141bf2a..16e22b7815c2 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P3-3-T-nh-SD-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P3-3-T-nh-SD-SMP-hp
@@ -10,7 +10,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P4-A-t-NH-sd-SMP-HP b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P4-A-t-NH-sd-SMP-HP
index 3ccf6a9447f5..ea7ed3b9a2da 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P4-A-t-NH-sd-SMP-HP
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P4-A-t-NH-sd-SMP-HP
@@ -8,7 +8,7 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_RT_MUTEXES=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P5-U-T-NH-sd-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P5-U-T-NH-sd-SMP-hp
index a55c00877fe4..24f4d5e40c80 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P5-U-T-NH-sd-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v0.0/P5-U-T-NH-sd-SMP-hp
@@ -11,7 +11,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_DEBUG_KERNEL=y
 CONFIG_DEBUG_OBJECTS=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P1-S-T-NH-SD-SMP-HP b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P1-S-T-NH-SD-SMP-HP
index 9647c44cf4b7..688066322c89 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P1-S-T-NH-SD-SMP-HP
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P1-S-T-NH-SD-SMP-HP
@@ -10,7 +10,7 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P2-2-t-nh-sd-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P2-2-t-nh-sd-SMP-hp
index 0f3b667d2a9f..81d484362820 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P2-2-t-nh-sd-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P2-2-t-nh-sd-SMP-hp
@@ -10,7 +10,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P3-3-T-nh-SD-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P3-3-T-nh-SD-SMP-hp
index b035e141bf2a..16e22b7815c2 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P3-3-T-nh-SD-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P3-3-T-nh-SD-SMP-hp
@@ -10,7 +10,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P4-A-t-NH-sd-SMP-HP b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P4-A-t-NH-sd-SMP-HP
index 3ccf6a9447f5..ea7ed3b9a2da 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P4-A-t-NH-sd-SMP-HP
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P4-A-t-NH-sd-SMP-HP
@@ -8,7 +8,7 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_RT_MUTEXES=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P5-U-T-NH-sd-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P5-U-T-NH-sd-SMP-hp
index a55c00877fe4..24f4d5e40c80 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P5-U-T-NH-sd-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P5-U-T-NH-sd-SMP-hp
@@ -11,7 +11,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_DEBUG_KERNEL=y
 CONFIG_DEBUG_OBJECTS=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P6---t-nh-SD-smp-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P6---t-nh-SD-smp-hp
index f4c9175828bf..1be59e4c8ba7 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P6---t-nh-SD-smp-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P6---t-nh-SD-smp-hp
@@ -8,7 +8,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-CONFIG_TREE_PREEMPT_RCU=y
+CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP
index 77a8c5b75763..b49ef7463099 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP
@@ -14,7 +14,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_PROVE_LOCKING=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-all b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-all
index 0eecebc6e95f..a55a6ac447d8 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-all
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-all
@@ -14,7 +14,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_PROVE_LOCKING=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-none b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-none
index 0eecebc6e95f..a55a6ac447d8 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-none
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-HP-none
@@ -14,7 +14,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_PROVE_LOCKING=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-hp
index 588bc70420cd..3134f46b2f87 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.12/P7-4-T-NH-SD-SMP-hp
@@ -14,7 +14,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_PROVE_LOCKING=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P1-S-T-NH-SD-SMP-HP b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P1-S-T-NH-SD-SMP-HP
index 9647c44cf4b7..688066322c89 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P1-S-T-NH-SD-SMP-HP
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P1-S-T-NH-SD-SMP-HP
@@ -10,7 +10,7 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P2-2-t-nh-sd-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P2-2-t-nh-sd-SMP-hp
index 0f3b667d2a9f..81d484362820 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P2-2-t-nh-sd-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P2-2-t-nh-sd-SMP-hp
@@ -10,7 +10,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P3-3-T-nh-SD-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P3-3-T-nh-SD-SMP-hp
index b035e141bf2a..16e22b7815c2 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P3-3-T-nh-SD-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P3-3-T-nh-SD-SMP-hp
@@ -10,7 +10,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P4-A-t-NH-sd-SMP-HP b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P4-A-t-NH-sd-SMP-HP
index 3ccf6a9447f5..ea7ed3b9a2da 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P4-A-t-NH-sd-SMP-HP
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P4-A-t-NH-sd-SMP-HP
@@ -8,7 +8,7 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_RT_MUTEXES=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P5-U-T-NH-sd-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P5-U-T-NH-sd-SMP-hp
index a55c00877fe4..24f4d5e40c80 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P5-U-T-NH-sd-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.3/P5-U-T-NH-sd-SMP-hp
@@ -11,7 +11,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_DEBUG_KERNEL=y
 CONFIG_DEBUG_OBJECTS=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P1-S-T-NH-SD-SMP-HP b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P1-S-T-NH-SD-SMP-HP
index 9647c44cf4b7..688066322c89 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P1-S-T-NH-SD-SMP-HP
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P1-S-T-NH-SD-SMP-HP
@@ -10,7 +10,7 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P2-2-t-nh-sd-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P2-2-t-nh-sd-SMP-hp
index 0f3b667d2a9f..81d484362820 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P2-2-t-nh-sd-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P2-2-t-nh-sd-SMP-hp
@@ -10,7 +10,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P3-3-T-nh-SD-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P3-3-T-nh-SD-SMP-hp
index b035e141bf2a..16e22b7815c2 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P3-3-T-nh-SD-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P3-3-T-nh-SD-SMP-hp
@@ -10,7 +10,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SYSFS_DEPRECATED_V2=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P4-A-t-NH-sd-SMP-HP b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P4-A-t-NH-sd-SMP-HP
index 3ccf6a9447f5..ea7ed3b9a2da 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P4-A-t-NH-sd-SMP-HP
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P4-A-t-NH-sd-SMP-HP
@@ -8,7 +8,7 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_RCU_TORTURE_TEST=m
 CONFIG_MODULE_UNLOAD=y
 CONFIG_RT_MUTEXES=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P5-U-T-NH-sd-SMP-hp b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P5-U-T-NH-sd-SMP-hp
index a55c00877fe4..24f4d5e40c80 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P5-U-T-NH-sd-SMP-hp
+++ b/tools/testing/selftests/rcutorture/configs/rcu/v3.5/P5-U-T-NH-sd-SMP-hp
@@ -11,7 +11,7 @@ CONFIG_HIBERNATION=n
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_DEBUG_KERNEL=y
 CONFIG_DEBUG_OBJECTS=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
diff --git a/tools/testing/selftests/rcutorture/doc/TINY_RCU.txt b/tools/testing/selftests/rcutorture/doc/TINY_RCU.txt
index 28db67b54e55..9ef33a743b73 100644
--- a/tools/testing/selftests/rcutorture/doc/TINY_RCU.txt
+++ b/tools/testing/selftests/rcutorture/doc/TINY_RCU.txt
@@ -34,7 +34,7 @@ CONFIG_PREEMPT
 CONFIG_PREEMPT_RCU
 CONFIG_SMP
 CONFIG_TINY_RCU
-CONFIG_TREE_PREEMPT_RCU
+CONFIG_PREEMPT_RCU
 CONFIG_TREE_RCU
 
 	All forced by CONFIG_TINY_RCU.
diff --git a/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
index ab6e7b4103ac..f613755a90bd 100644
--- a/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
+++ b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
@@ -1,5 +1,5 @@
 This document gives a brief rationale for the TREE_RCU-related test
-cases, a group that includes TREE_PREEMPT_RCU.
+cases, a group that includes PREEMPT_RCU.
 
 
 Kconfig Parameters:
@@ -14,7 +14,7 @@ CONFIG_NO_HZ_FULL_SYSIDLE -- Do one.
 CONFIG_PREEMPT -- Do half.  (First three and #8.)
 CONFIG_PROVE_LOCKING -- Do all but two, covering CONFIG_PROVE_RCU and not.
 CONFIG_PROVE_RCU -- Do all but one under CONFIG_PROVE_LOCKING.
-CONFIG_RCU_BOOST -- one of TREE_PREEMPT_RCU.
+CONFIG_RCU_BOOST -- one of PREEMPT_RCU.
 CONFIG_RCU_KTHREAD_PRIO -- set to 2 for _BOOST testing.
 CONFIG_RCU_CPU_STALL_INFO -- Do one.
 CONFIG_RCU_CPU_STALL_VERBOSE -- do one with and without _INFO.
@@ -27,7 +27,7 @@ CONFIG_RCU_NOCB_CPU_ALL -- Do one.
 CONFIG_RCU_NOCB_CPU_NONE -- Do one.
 CONFIG_RCU_NOCB_CPU_ZERO -- Do one.
 CONFIG_RCU_TRACE -- Do half.
-CONFIG_SMP -- Need one !SMP for TREE_PREEMPT_RCU.
+CONFIG_SMP -- Need one !SMP for PREEMPT_RCU.
 RCU-bh: Do one with PREEMPT and one with !PREEMPT.
 RCU-sched: Do one with PREEMPT but not BOOST.
 
@@ -77,7 +77,7 @@ CONFIG_RCU_CPU_STALL_TIMEOUT
 
 CONFIG_RCU_STALL_COMMON
 
-	Implied by TREE_RCU and TREE_PREEMPT_RCU.
+	Implied by TREE_RCU and PREEMPT_RCU.
 
 CONFIG_RCU_TORTURE_TEST
 CONFIG_RCU_TORTURE_TEST_RUNNABLE
@@ -88,7 +88,7 @@ CONFIG_RCU_USER_QS
 
 	Redundant with CONFIG_NO_HZ_FULL.
 
-CONFIG_TREE_PREEMPT_RCU
+CONFIG_PREEMPT_RCU
 CONFIG_TREE_RCU
 
 	These are controlled by CONFIG_PREEMPT.
-- 
1.8.1.5

[PATCH tip/core/rcu 6/7] rcu: Kick rcuo kthreads after their CPU goes offline

[Paul E. McKenney]

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

If a no-CBs CPU were to post an RCU callback with interrupts disabled
after it entered the idle loop for the last time, there might be no
deferred wakeup for the corresponding rcuo kthreads.  This commit
therefore adds a set of calls to do_nocb_deferred_wakeup() after the
CPU has gone completely offline.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9e3c20f117cd..07bf4aa68d50 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3497,8 +3497,10 @@ static int rcu_cpu_notify(struct notifier_block *self,
 	case CPU_DEAD_FROZEN:
 	case CPU_UP_CANCELED:
 	case CPU_UP_CANCELED_FROZEN:
-		for_each_rcu_flavor(rsp)
+		for_each_rcu_flavor(rsp) {
 			rcu_cleanup_dead_cpu(cpu, rsp);
+			do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu));
+		}
 		break;
 	default:
 		break;
-- 
1.8.1.5

[PATCH tip/core/rcu 7/7] rcu: Fix for rcuo online-time-creation reorganization bug

[Paul E. McKenney]

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

Commit 35ce7f29a44a (rcu: Create rcuo kthreads only for onlined CPUs)
contains checks for the case where CPUs are brought online out of
order, re-wiring the rcuo leader-follower relationships as needed.
Unfortunately, this rewiring was broken.  This apparently went undetected
due to the tendency of systems to bring CPUs online in order.  This commit
nevertheless fixes the rewiring.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcu/tree_plugin.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 6d07fb402e84..5053dae4454e 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2586,9 +2586,13 @@ static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu)
 			rdp->nocb_leader = rdp_spawn;
 			if (rdp_last && rdp != rdp_spawn)
 				rdp_last->nocb_next_follower = rdp;
-			rdp_last = rdp;
-			rdp = rdp->nocb_next_follower;
-			rdp_last->nocb_next_follower = NULL;
+			if (rdp == rdp_spawn) {
+				rdp = rdp->nocb_next_follower;
+			} else {
+				rdp_last = rdp;
+				rdp = rdp->nocb_next_follower;
+				rdp_last->nocb_next_follower = NULL;
+			}
 		} while (rdp);
 		rdp_spawn->nocb_next_follower = rdp_old_leader;
 	}
-- 
1.8.1.5

Re: [PATCH tip/core/rcu 3/7] rcu: Avoid IPIing idle CPUs from synchronize_sched_expedited()

[Peter Zijlstra]

On Tue, Oct 28, 2014 at 03:22:58PM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> 
> Currently, synchronize_sched_expedited() sends IPIs to all online CPUs,
> even those that are idle or executing in nohz_full= userspace.  Because
> idle CPUs and nohz_full= userspace CPUs are in extended quiescent states,
> there is no need to IPI them in the first place.  This commit therefore
> avoids IPIing CPUs that are already in extended quiescent states.
> 
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
>  kernel/rcu/tree.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 7f73c5edf8cf..9e3c20f117cd 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2950,6 +2950,9 @@ static int synchronize_sched_expedited_cpu_stop(void *data)
>   */
>  void synchronize_sched_expedited(void)
>  {
> +	cpumask_var_t cm;
> +	bool cma = false;
> +	int cpu;
>  	long firstsnap, s, snap;
>  	int trycount = 0;
>  	struct rcu_state *rsp = &rcu_sched_state;
> @@ -2984,11 +2987,26 @@ void synchronize_sched_expedited(void)
>  	}
>  	WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
>  
> +	/* Offline CPUs, idle CPUs, and any CPU we run on are quiescent. */
> +	cma = zalloc_cpumask_var(&cm, GFP_KERNEL);
> +	if (cma) {
> +		cpumask_copy(cm, cpu_online_mask);
> +		cpumask_clear_cpu(raw_smp_processor_id(), cm);
> +		for_each_cpu(cpu, cm) {
> +			struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
> +
> +			if (!(atomic_add_return(0, &rdtp->dynticks) & 0x1))
> +				cpumask_clear_cpu(cpu, cm);
> +		}
> +		if (cpumask_weight(cm) == 0)
> +			goto all_cpus_idle;
> +	}

Is there a reason not to use on_each_cpu_cond()?

Re: [PATCH tip/core/rcu 4/7] rcu: Unify boost and kthread priorities

[Peter Zijlstra]

On Tue, Oct 28, 2014 at 03:22:59PM -0700, Paul E. McKenney wrote:
> From: Clark Williams <clark.williams@gmail.com>
> 
> Rename CONFIG_RCU_BOOST_PRIO to CONFIG_RCU_KTHREAD_PRIO and use this
> value for both the per-CPU kthreads (rcuc/N) and the rcu boosting
> threads (rcub/n).
> 
> Also, create the module_parameter rcutree.kthread_prio to be used on
> the kernel command line at boot to set a new value (rcutree.kthread_prio=N).
> 
> Signed-off-by: Clark Williams <clark.williams@gmail.com>
> [ paulmck: Ported to rcu/dev, applied Paul Bolle feedback. ]
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
>  Documentation/kernel-parameters.txt                |  6 ++++++
>  init/Kconfig                                       | 23 +++++++++++-----------
>  kernel/rcu/tree_plugin.h                           | 20 +++++++++----------
>  .../selftests/rcutorture/configs/rcu/TREE03        |  2 +-
>  .../selftests/rcutorture/doc/TREE_RCU-kconfig.txt  |  4 ++--
>  5 files changed, 31 insertions(+), 24 deletions(-)
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 7dbe5ec9d9cd..7d3b3328bf5c 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -2922,6 +2922,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>  			quiescent states.  Units are jiffies, minimum
>  			value is one, and maximum value is HZ.
>  
> +	rcutree.kthread_prio= 	 [KNL,BOOT]
> +			Set the SCHED_FIFO priority of the RCU
> +			per-CPU kthreads (rcuc/N). This value is also
> +			used for the priority of the RCU boost threads
> +			(rcub/N). Valid values are 1-99.
> +

It would maybe be useful to mention the default?

Also, should we look at running this stuff as deadline in order to
provide interference guarantees etc.. ?

Re: [PATCH tip/core/rcu 3/7] rcu: Avoid IPIing idle CPUs from synchronize_sched_expedited()

[Paul E. McKenney]

On Wed, Oct 29, 2014 at 11:59:54AM +0100, Peter Zijlstra wrote:
> On Tue, Oct 28, 2014 at 03:22:58PM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> > 
> > Currently, synchronize_sched_expedited() sends IPIs to all online CPUs,
> > even those that are idle or executing in nohz_full= userspace.  Because
> > idle CPUs and nohz_full= userspace CPUs are in extended quiescent states,
> > there is no need to IPI them in the first place.  This commit therefore
> > avoids IPIing CPUs that are already in extended quiescent states.
> > 
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > ---
> >  kernel/rcu/tree.c | 27 ++++++++++++++++++++++++++-
> >  1 file changed, 26 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 7f73c5edf8cf..9e3c20f117cd 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -2950,6 +2950,9 @@ static int synchronize_sched_expedited_cpu_stop(void *data)
> >   */
> >  void synchronize_sched_expedited(void)
> >  {
> > +	cpumask_var_t cm;
> > +	bool cma = false;
> > +	int cpu;
> >  	long firstsnap, s, snap;
> >  	int trycount = 0;
> >  	struct rcu_state *rsp = &rcu_sched_state;
> > @@ -2984,11 +2987,26 @@ void synchronize_sched_expedited(void)
> >  	}
> >  	WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
> >  
> > +	/* Offline CPUs, idle CPUs, and any CPU we run on are quiescent. */
> > +	cma = zalloc_cpumask_var(&cm, GFP_KERNEL);
> > +	if (cma) {
> > +		cpumask_copy(cm, cpu_online_mask);
> > +		cpumask_clear_cpu(raw_smp_processor_id(), cm);
> > +		for_each_cpu(cpu, cm) {
> > +			struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
> > +
> > +			if (!(atomic_add_return(0, &rdtp->dynticks) & 0x1))
> > +				cpumask_clear_cpu(cpu, cm);
> > +		}
> > +		if (cpumask_weight(cm) == 0)
> > +			goto all_cpus_idle;
> > +	}
> 
> Is there a reason not to use on_each_cpu_cond()?

Because I don't know how to write a function that returns a blooean value?
(Sorry, couldn't resist, and yes I do know that "boolean" was meant.)
If we had lambdas, I might be interested in making that transformation,
but pulling the condition into a separate function doesn't seem like
a win to me.

But even with lambdas, it looks to me like on_each_cpu_cond() just does
an IPI, and I need the selected CPUs to do a context switch.  Yes, I
could make the IPI handler function call induce a context switch, but
then I would have to add more mechanism to wait for the induced context
switches to actually happen.

That said, I am considering switching synchronize_sched_expedited()
from try_stop_cpus() to resched_cpu() if I need to parallelize
synchronize_sched_expedited().

							Thanx, Paul

Re: [PATCH tip/core/rcu 4/7] rcu: Unify boost and kthread priorities

[Paul E. McKenney]

On Wed, Oct 29, 2014 at 12:01:46PM +0100, Peter Zijlstra wrote:
> On Tue, Oct 28, 2014 at 03:22:59PM -0700, Paul E. McKenney wrote:
> > From: Clark Williams <clark.williams@gmail.com>
> > 
> > Rename CONFIG_RCU_BOOST_PRIO to CONFIG_RCU_KTHREAD_PRIO and use this
> > value for both the per-CPU kthreads (rcuc/N) and the rcu boosting
> > threads (rcub/n).
> > 
> > Also, create the module_parameter rcutree.kthread_prio to be used on
> > the kernel command line at boot to set a new value (rcutree.kthread_prio=N).
> > 
> > Signed-off-by: Clark Williams <clark.williams@gmail.com>
> > [ paulmck: Ported to rcu/dev, applied Paul Bolle feedback. ]
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > ---
> >  Documentation/kernel-parameters.txt                |  6 ++++++
> >  init/Kconfig                                       | 23 +++++++++++-----------
> >  kernel/rcu/tree_plugin.h                           | 20 +++++++++----------
> >  .../selftests/rcutorture/configs/rcu/TREE03        |  2 +-
> >  .../selftests/rcutorture/doc/TREE_RCU-kconfig.txt  |  4 ++--
> >  5 files changed, 31 insertions(+), 24 deletions(-)
> > 
> > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> > index 7dbe5ec9d9cd..7d3b3328bf5c 100644
> > --- a/Documentation/kernel-parameters.txt
> > +++ b/Documentation/kernel-parameters.txt
> > @@ -2922,6 +2922,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> >  			quiescent states.  Units are jiffies, minimum
> >  			value is one, and maximum value is HZ.
> >  
> > +	rcutree.kthread_prio= 	 [KNL,BOOT]
> > +			Set the SCHED_FIFO priority of the RCU
> > +			per-CPU kthreads (rcuc/N). This value is also
> > +			used for the priority of the RCU boost threads
> > +			(rcub/N). Valid values are 1-99.
> > +
> 
> It would maybe be useful to mention the default?

Good point, fixed.  It now reads as follows:

	rcutree.kthread_prio= 	 [KNL,BOOT]
			Set the SCHED_FIFO priority of the RCU
			per-CPU kthreads (rcuc/N). This value is also
			used for the priority of the RCU boost threads
			(rcub/N). Valid values are 1-99 and the default
			is 1 (the least-favored priority).

> Also, should we look at running this stuff as deadline in order to
> provide interference guarantees etc.. ?

Excellent question!  I have absolutely no idea what the answer might be.

Taking the two sets of kthreads separately...

rcub/N:	This is for RCU priority boosting.  In the preferred common case,
	these never wake up ever.  When they do wake up, all they do is
	cause blocked RCU readers to get priority boosted.   I vaguely
	recall something about inheritance of deadlines, which might
	work here.  One concern is what happens if the deadline is
	violated, as this isn't really necessarily an error condition
	in this case -- we don't know how long the RCU read-side critical
	section will run once awakened.

rcuc/N: This is the softirq replacement in -rt, but in mainline all it
	does is invoke RCU callbacks.	It might make sense to give it a
	deadline of something like a few milliseconds, but we would need
	to temper that if there were huge numbers of callbacks pending.
	Or perhaps have it claim that its "unit of work" was some fixed
	number of callbacks or emptying the list, whichever came first.
	Or maybe have its "unit of work" also depend on the number of
	callbacks pending.

Thoughts?

							Thanx, Paul

Re: [PATCH tip/core/rcu 4/7] rcu: Unify boost and kthread priorities

[Peter Zijlstra]

On Wed, Oct 29, 2014 at 09:16:02AM -0700, Paul E. McKenney wrote:

> > Also, should we look at running this stuff as deadline in order to
> > provide interference guarantees etc.. ?
> 
> Excellent question!  I have absolutely no idea what the answer might be.
> 
> Taking the two sets of kthreads separately...
> 
> rcub/N:	This is for RCU priority boosting.  In the preferred common case,
> 	these never wake up ever.  When they do wake up, all they do is
> 	cause blocked RCU readers to get priority boosted.   I vaguely
> 	recall something about inheritance of deadlines, which might
> 	work here.  One concern is what happens if the deadline is
> 	violated, as this isn't really necessarily an error condition
> 	in this case -- we don't know how long the RCU read-side critical
> 	section will run once awakened.

Yea, this one is 'hard'. How is this used today? From the previous email
we've learnt that the default is FIFO-1, iow. it will preempt
SCHED_OTHER but not much more. How is this used in RT systems, what are
the criteria for actually changing this?

Increase until RCU stops spilling stalled warns, but not so far that
your workload fails?

Not quite sure how to translate that into dl speak :-), the problem of
course is that if a DL task starts to trigger the stalls we need to do
something.

> rcuc/N: This is the softirq replacement in -rt, but in mainline all it
> 	does is invoke RCU callbacks.	It might make sense to give it a
> 	deadline of something like a few milliseconds, but we would need
> 	to temper that if there were huge numbers of callbacks pending.
> 	Or perhaps have it claim that its "unit of work" was some fixed
> 	number of callbacks or emptying the list, whichever came first.
> 	Or maybe have its "unit of work" also depend on the number of
> 	callbacks pending.

Right, so the problem is if we give it insufficient time it will never
catch up on running the callbacks, ie. more will come in than we can
process and get out.

So if it works by splicing a callback list to a local list, then runs
until completion and then either immediately starts again if there's
new work, or goes to sleep waiting for more, _then_ we can already
assign it DL parameters with the only caveat being the above issue.

The advantage being indeed that if there are 'many' callbacks pending,
we'd only run a few, sleep, run a few more, etc.. due to the CBS until
we're done. This smooths out peak interference at the 'cost' of
additional delays in actually running the callbacks.

We should be able to detect the case where more and work piles on and
the actual running does not appear to catch up, but I'm not sure what to
do about it, seeing how system stability is at risk.

Certainly something to think about..

Re: [PATCH tip/core/rcu 4/7] rcu: Unify boost and kthread priorities

[Paul E. McKenney]

On Fri, Oct 31, 2014 at 05:22:10PM +0100, Peter Zijlstra wrote:
> On Wed, Oct 29, 2014 at 09:16:02AM -0700, Paul E. McKenney wrote:
> 
> > > Also, should we look at running this stuff as deadline in order to
> > > provide interference guarantees etc.. ?
> > 
> > Excellent question!  I have absolutely no idea what the answer might be.
> > 
> > Taking the two sets of kthreads separately...
> > 
> > rcub/N:	This is for RCU priority boosting.  In the preferred common case,
> > 	these never wake up ever.  When they do wake up, all they do is
> > 	cause blocked RCU readers to get priority boosted.   I vaguely
> > 	recall something about inheritance of deadlines, which might
> > 	work here.  One concern is what happens if the deadline is
> > 	violated, as this isn't really necessarily an error condition
> > 	in this case -- we don't know how long the RCU read-side critical
> > 	section will run once awakened.
> 
> Yea, this one is 'hard'. How is this used today? From the previous email
> we've learnt that the default is FIFO-1, iow. it will preempt
> SCHED_OTHER but not much more. How is this used in RT systems, what are
> the criteria for actually changing this?

The old way is to update CONFIG_RCU_BOOST_PRIO and rebuild your kernel,
but a recent commit from Clark Williams provides a boot parameter that
allows this priority to be changed more conveniently.

> Increase until RCU stops spilling stalled warns, but not so far that
> your workload fails?

Well, you are supposed to determine the highest RT priority at which
your workload might run CPU-bound tasks, and set the boost priority
at some level above that.  My model of RCU priority boosting is that
it should be used to make inadvertent high-priority infinite loops
easier to debug, but others might have different approaches.

> Not quite sure how to translate that into dl speak :-), the problem of
> course is that if a DL task starts to trigger the stalls we need to do
> something.

Indeed!  ;-)

> > rcuc/N: This is the softirq replacement in -rt, but in mainline all it
> > 	does is invoke RCU callbacks.	It might make sense to give it a
> > 	deadline of something like a few milliseconds, but we would need
> > 	to temper that if there were huge numbers of callbacks pending.
> > 	Or perhaps have it claim that its "unit of work" was some fixed
> > 	number of callbacks or emptying the list, whichever came first.
> > 	Or maybe have its "unit of work" also depend on the number of
> > 	callbacks pending.
> 
> Right, so the problem is if we give it insufficient time it will never
> catch up on running the callbacks, ie. more will come in than we can
> process and get out.

Yep, which can result in OOM.

> So if it works by splicing a callback list to a local list, then runs
> until completion and then either immediately starts again if there's
> new work, or goes to sleep waiting for more, _then_ we can already
> assign it DL parameters with the only caveat being the above issue.
> 
> The advantage being indeed that if there are 'many' callbacks pending,
> we'd only run a few, sleep, run a few more, etc.. due to the CBS until
> we're done. This smooths out peak interference at the 'cost' of
> additional delays in actually running the callbacks.
> 
> We should be able to detect the case where more and work piles on and
> the actual running does not appear to catch up, but I'm not sure what to
> do about it, seeing how system stability is at risk.

I could imagine having a backup SCHED_FIFO task that handled the
case where callbacks were piling up, but synchronizing it with the
SCHED_DEADLINE task while avoiding callback misordering could be a bit
"interesting".  (Recall that callback misordering messes up rcu_barrier().)

> Certainly something to think about..

No argument here!  ;-)

							Thanx, Paul

Re: [PATCH tip/core/rcu 4/7] rcu: Unify boost and kthread priorities

[Peter Zijlstra]

On Fri, Oct 31, 2014 at 09:42:30AM -0700, Paul E. McKenney wrote:

> Well, you are supposed to determine the highest RT priority at which
> your workload might run CPU-bound tasks, and set the boost priority
> at some level above that.  My model of RCU priority boosting is that
> it should be used to make inadvertent high-priority infinite loops
> easier to debug, but others might have different approaches.

Ah, so DL will never be CPU-bound -- and RR/FIFO _should_ never be, but
I digress ;-)

> > We should be able to detect the case where more and work piles on and
> > the actual running does not appear to catch up, but I'm not sure what to
> > do about it, seeing how system stability is at risk.
> 
> I could imagine having a backup SCHED_FIFO task that handled the
> case where callbacks were piling up, but synchronizing it with the
> SCHED_DEADLINE task while avoiding callback misordering could be a bit
> "interesting".  (Recall that callback misordering messes up rcu_barrier().)

Ah, so there is talk of 'soft' CBS modes, which instead of hard throttle
either reclaim 'unused' DL bandwidth, or continue running in lower scheduling
classes.

Re: [PATCH tip/core/rcu 4/7] rcu: Unify boost and kthread priorities

[Paul E. McKenney]

On Fri, Oct 31, 2014 at 05:51:43PM +0100, Peter Zijlstra wrote:
> On Fri, Oct 31, 2014 at 09:42:30AM -0700, Paul E. McKenney wrote:
> 
> > Well, you are supposed to determine the highest RT priority at which
> > your workload might run CPU-bound tasks, and set the boost priority
> > at some level above that.  My model of RCU priority boosting is that
> > it should be used to make inadvertent high-priority infinite loops
> > easier to debug, but others might have different approaches.
> 
> Ah, so DL will never be CPU-bound -- and RR/FIFO _should_ never be, but
> I digress ;-)

;-) ;-) ;-)

> > > We should be able to detect the case where more and work piles on and
> > > the actual running does not appear to catch up, but I'm not sure what to
> > > do about it, seeing how system stability is at risk.
> > 
> > I could imagine having a backup SCHED_FIFO task that handled the
> > case where callbacks were piling up, but synchronizing it with the
> > SCHED_DEADLINE task while avoiding callback misordering could be a bit
> > "interesting".  (Recall that callback misordering messes up rcu_barrier().)
> 
> Ah, so there is talk of 'soft' CBS modes, which instead of hard throttle
> either reclaim 'unused' DL bandwidth, or continue running in lower scheduling
> classes.

OK, something like that might work in this case, at least making the
dubious assumption that I actually understand what you are getting at.  ;-)

You might be amused to hear that one of the solutions in my back pocket
for the potential problem of callbacks piling up in the current RCU
priority boosting scheme is to temporarily increase the priority.  This is
similar to how blimit gets increased if too many callbacks pile up.

Thus far, no need for this back-pocket solution, but I wanted to put it
out there in case it sparks something in the SCHED_DEADLINE approach.

							Thanx, Paul